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Sample records for advanced nickel-base superalloys

  1. Advanced microcharacterization of nickel-base superalloys

    SciTech Connect

    Anderson, I.M.; Miller, M.K.; Pike, L.M.; Klarstrom, D.L.

    2000-02-01

    The purpose of this project was to characterize the microstructural and microchemical effects of a process revision on HAYNES{reg{underscore}sign} 242{trademark}, a polycrystalline Ni-base superalloy used principally for high temperature applications, such as seal and containment rings in gas turbine engines. The process revision from the current one-step heat treating cycle to a two-step heat treatment would result in savings of energy and ultimately cost to the consumer. However, the proposed process revision could give rise to unforeseen microstructural modifications, such as a change in the size distribution of the ordered particles responsible for alloy strength or the formation of additional phases, which could affect alloy properties and hence performance. Advanced microcharacterization methods that allow images of the microstructure to be acquired at length scales from one micrometer down to the atomic level were used to reveal the effect of the process revision on alloy microstructure. Energy filtered imaging was used to characterize the size distribution and morphology of ordered precipitates and other phases, as well as the partitioning behavior of major elements (Ni, Mo, Cr) among these phases. The compositions of individual ordered particles, including fine-scale compositional variations at precipitate-matrix interfaces, and solute segregation behavior at grain boundaries were characterized at the atomic level by atom probe tomography. The atomic site distributions of selected elements in the ordered precipitates were characterized by atom-location by channeling-enhanced microanalysis (ALCHEMI). The results of these advanced microcharacterization methods were correlated with mechanical testing of similar alloys to address structure-property relationships.

  2. Successful Surface Treatments for Reducing Instabilities in Advanced Nickel-base Superalloys for Turbine Blades

    NASA Technical Reports Server (NTRS)

    Locci, Ivan E.; MacKay, Rebecca A.; Garg, Anita; Ritzert, Frank J.

    2004-01-01

    An optimized carburization treatment has been developed to mitigate instabilities that form in the microstructures of advanced turbine airfoil materials. Current turbine airfoils consist of a single crystal superalloy base that provides the mechanical performance of the airfoil, a thermal barrier coating (TBC) that reduces the temperature of the base superalloy, and a bondcoat between the superalloy and the TBC, that improves the oxidation and corrosion resistance of the base superalloy and the spallation resistance of the TBC. Advanced nickel-base superalloys containing high levels of refractory metals have been observed to develop an instability called secondary reaction zone (SRZ), which can form beneath diffusion aluminide bondcoats. This instability between the superalloy and the bondcoat has the potential of reducing the mechanical properties of thin-wall turbine airfoils. Controlled gas carburization treatments combined with a prior stress relief heat treatment and adequate surface preparation have been utilized effectively to minimize the formation of SRZ. These additional processing steps are employed before the aluminide bondcoat is deposited and are believed to change the local chemistry and local stresses of the surface of the superalloy. This paper presents the detailed processing steps used to reduce SRZ between platinum aluminide bondcoats and advanced single crystal superalloys.

  3. Improving the Oxidation Resistance in Advanced Single Crystal Nickel-Based Superalloys for Turbine Applications

    SciTech Connect

    Alexander, K.B.; Kenik, E.A.; Miller, M.K.; Lin, L.S.; Cetel, A.D.

    1999-07-01

    The focus of this project was the examination of the role of yttrium and other alloying elements on the microstructure and oxidation performance of improved single crystal nickel-based superalloys for advanced turbine applications. The microstructure and microchemistry of both base and modified alloys and their surface oxides have been measured with state-of-the-art microanalytical techniques (atom probe field ion microscopy) and then correlated with identifying the partitioning behavior of the elemental additions in these superalloys before and after burner rig and engine-test oxidation performance. The overall technical goals included; (1) identifying the partitioning behavior of the elemental additions in these superalloys before and after burner rig and engine tests and the effect on the misfit energy between the phases in the alloys; (2) examining the oxidation performance of these newly-developed alloys; (3) identifying the influence of pre-oxidation processing on the subsequent oxidation performance; and (4) relating the microstructural and microchemical observations to the observed performance of these superalloys. The comparison of the base and modified alloys will produce a better understanding of the interaction between chemistry, structure, and performance in superalloys. In addition, it will lead to optimized alloys with improved performance including enhanced durability in the operating environments at the elevated temperature required to improve energy efficiency. The availability of alloys capable of higher temperature operation will minimize the need for expensive coatings in extreme temperature applications.

  4. Nickel Base Superalloy Turbine Disk

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P. (Inventor); Gauda, John (Inventor); Telesman, Ignacy (Inventor); Kantzos, Pete T. (Inventor)

    2005-01-01

    A low solvus, high refractory alloy having unusually versatile processing mechanical property capabilities for advanced disks and rotors in gas turbine engines. The nickel base superalloy has a composition consisting essentially of, in weight percent, 3.0-4.0 N, 0.02-0.04 B, 0.02-0.05 C, 12.0-14.0 Cr, 19.0-22.0 Co, 2.0-3.5 Mo, greater than 1.0 to 2.1 Nb, 1.3 to 2.1 Ta,3.04.OTi,4.1 to 5.0 W, 0.03-0.06 Zr, and balance essentially Ni and incidental impurities. The superalloy combines ease of processing with high temperature capabilities to be suitable for use in various turbine engine disk, impeller, and shaft applications. The Co and Cr levels of the superalloy can provide low solvus temperature for high processing versatility. The W, Mo, Ta, and Nb refractory element levels of the superalloy can provide sustained strength, creep, and dwell crack growth resistance at high temperatures.

  5. The Tensile Properties of Advanced Nickel-Base Disk Superalloys During Quenching Heat Treatments

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Gayda, John; Kantzos, Pete T.; Biles, Tiffany; Konkel, William

    2001-01-01

    There is a need to increase the temperature capabilities of superalloy turbine disks. This would allow full utilization of higher temperature combustor and airfoil concepts under development. One approach to meet this goal is to modify the processing and chemistry of advanced alloys, while preserving the ability to use rapid cooling supersolvus heat treatments to achieve coarse grain, fine gamma prime microstructures. An important step in this effort is to understand the key high temperature tensile properties of advanced alloys as they exist during supersolvus heat treatments. This could help in projecting cracking tendencies of disks during quenches from supersolvus heat treatments. The objective of this study was to examine the tensile properties of two advanced disk superalloys during simulated quenching heat treatments. Specimens were cooled from the solution heat treatment temperatures at controlled rates, interrupted, and immediately tensile tested at various temperatures. The responses and failure modes were compared and related to the quench cracking tendencies of disk forgings.

  6. Techniques Optimized for Reducing Instabilities in Advanced Nickel-Base Superalloys for Turbine Blades

    NASA Technical Reports Server (NTRS)

    MacKay, Rebecca A.; Locci, Ivan E.; Garg, anita; Ritzert, Frank J.

    2002-01-01

    is a three-phase constituent composed of TCP and stringers of gamma phase in a matrix of gamma prime. An incoherent grain boundary separates the SRZ from the gammagamma prime microstructure of the superalloy. The SRZ is believed to form as a result of local chemistry changes in the superalloy due to the application of the diffusion aluminide bondcoat. Locally high surface stresses also appear to promote the formation of the SRZ. Thus, techniques that change the local alloy chemistry or reduce surface stresses have been examined for their effectiveness in reducing SRZ. These SRZ-reduction steps are performed on the test specimen or the turbine blade before the bondcoat is applied. Stressrelief heat treatments developed at NASA Glenn have been demonstrated to reduce significantly the amount of SRZ that develops during subsequent high-temperature exposures. Stress-relief heat treatments reduce surface stresses by recrystallizing a thin surface layer of the superalloy. However, in alloys with very high propensities to form SRZ, stress relief heat treatments alone do not eliminate SRZ entirely. Thus, techniques that modify the local chemistry under the bondcoat have been emphasized and optimized successfully at Glenn. One such technique is carburization, which changes the local chemistry by forming submicron carbides near the surface of the superalloy. Detailed characterizations have demonstrated that the depth and uniform distribution of these carbides are enhanced when a stress relief treatment and an appropriate surface preparation are employed in advance of the carburization treatment. Even in alloys that have the propensity to develop a continuous SRZ layer beneath the diffusion zone, the SRZ has been completely eliminated or reduced to low, manageable levels when this combination of techniques is utilized. Now that the techniques to mitigate SRZ have been established at Glenn, TCP phase formation is being emphasized in ongoing work under the UEET Program. The

  7. Role of cobalt in nickel base superalloys

    NASA Technical Reports Server (NTRS)

    Jarrett, R.; Barefoot, J.; Tien, J.; Sanchez, J.

    1982-01-01

    The effect of cobalt or substituting for cobalt on the mechanical properties of nickel-based superalloys is discussed. Waspaloy, UDIMET 700, and NIMONIC 115, which are representative of Ni-Cr-Co-Al-Ti-Mo superalloys having different gamma prime contents which are strengthened by a heavily alloyed matrix, coherent gamma prime precipitates, and carbides at the grain boundaries. Microstructure and in situ and extracted phase STEM micro-analysis were used to evaluate the three alloys.

  8. On the creep deformation mechanisms of an advanced disk nickel-base superalloy

    NASA Astrophysics Data System (ADS)

    Unocic, Raymond R.

    The main objective of this research was aimed at investigating the fundamental relationship between microstructure and creep deformation mechanisms using a variety of electron microscopy characterization techniques. The alloy used in this research, Rene 104, is a newer generation powder metallurgy Ni-base superalloy that was developed specifically for aircraft gas turbine disk applications with extended service durability at temperatures exceeding 650°C. The influence of stress and temperature was studied first and it was found that during creep deformation at temperatures between 677--815°C and stresses between 345--724MPa a variety of distinctly different creep deformation mechanisms were operative. In addition to identifying the creep deformation mechanisms an attempt was made to determine the creep rate limiting process so that an improved understanding of the fundamental processes that control deformation can be better understood. Microtwinning was found to the dominant deformation mechanism following creep at 677°C/690MPa and 704°C/724MPa. Microtwins form by the motion of paired a/6<112> Shockley partial dislocations that shear both the gamma matrix and gamma' precipitates. The rate limiting process in this mechanism is diffusion mediated atomic reordering that occurs in the wake of the shearing, twinning partial dislocations in order to maintain the ordered L12 structure of the gamma' precipitates. This reordering process helps to fundamentally explain the temperature and rate dependence of microtwinning under creep conditions within this temperature and stress regime. At a slightly higher temperature but lower stress (760°C and 345MPa), a stacking fault related shearing mechanism, which typically spanned only a few micrometers in length, was the principle deformation mode. The faults left behind in the gamma' precipitates determined to be extrinsic in nature. During creep at the highest temperature and lowest stress (815°C and 345MPa) a thermally

  9. High weldability nickel-base superalloy

    DOEpatents

    Gibson, Robert C.; Korenko, Michael K.

    1980-01-01

    This is a nickel-base superalloy with excellent weldability and high strength. Its composition consists essentially of, by weight percent, 10-20 iron, 57-63 nickel, 7-18 chromium, 4-6 molybdenum, 1-2 niobium, 0.2-0.8 silicon, 0.01-0.05 zirconium, 1.0-2.5 titanium, 1.0-2.5 aluminum, 0.02-0.06 carbon, and 0.002-0.015 boron. The weldability and strength of this alloy give it a variety of applications. The long-time structural stability of this alloy together with its low swelling under nuclear radiation conditions, make it especially suitable for use as a duct material and controlling element cladding for sodium-cooled nuclear reactors.

  10. The Effect of Alloying on Topologically Close Packed Phase Instability in Advanced Nickel-Based Superalloy Rene N6

    NASA Technical Reports Server (NTRS)

    Ritzert, Frank; Arenas, David; Keller, Dennis; Vasudevan, Vijay

    1998-01-01

    An investigation was conducted to describe topologically close packed (TCP) phase instability as a function of composition in the advanced Ni-base superalloy Rene N6. TCP phases are detrimental to overall high-temperature performance of Ni-base superalloys because of their brittle nature and because they deplete the Ni-rich matrix of potent solid solution strengthening elements. Thirty-four variations of polycrystalline Rene N6 determined from a design-of-experiments approach were cast and homogenized at 1315"C for 80 hours followed by exposure at 10930C for 400 hours to promote TCP formation. The alloys had the following composition ranges in atomic percent: Co 10.61 to 16.73%, Mo 0.32 to 1.34%, W 1.85 to 2.52%, Re 1.80 to 2.1 1 %, Ta 2.36 to 3.02%, Al 11.90 to 14.75%, and Cr 3.57 to 6.23%. Physical and chemical characteristics of all n-ticrostructures obtained were described using various analytical techniques. From these observations, a mathematical description of TCP occurrence (omega and P phase) was generated for polycrystalline Rene N6.

  11. Quench Crack Behavior of Nickel-base Disk Superalloys

    NASA Technical Reports Server (NTRS)

    Gayda, John; Kantzos, Pete; Miller, Jason

    2002-01-01

    There is a need to increase the temperature capability of superalloy turbine disks to allow higher operating temperatures in advanced aircraft engines. When modifying processing and chemistry of disk alloys to achieve this capability, it is important to preserve the ability to use rapid cooling during supersolvus heat treatments to achieve coarse grain, fine gamma prime microstructures. An important step in this effort is an understanding of the key variables controlling the cracking tendencies of nickel-base disk alloys during quenching from supersolvus heat treatments. The objective of this study was to investigate the quench cracking tendencies of several advanced disk superalloys during simulated heat treatments. Miniature disk specimens were rapidly quenched after solution heat treatments. The responses and failure modes were compared and related to the quench cracking tendencies of actual disk forgings. Cracking along grain boundaries was generally observed to be operative. For the alloys examined in this study, the solution temperature not alloy chemistry was found to be the primary factor controlling quench cracking. Alloys with high solvus temperatures show greater tendency for quench cracking.

  12. The continuing battle against defects in nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Dreshfield, R. L.

    1986-01-01

    In the six decades since the identification of age hardenable nickel-base superalloys their compositions and microstructures have changed markedly. Current alloys are tailored for specific applications. Thus their microstructures are defined for that application. This paper briefly reviews the evolution of superalloy microstructures and comments on the appearance and implications of microstructural defects in high performance superalloys. It is seen that new alloys and proceses have generated new types of defects. Thus as the industry continues to develop new alloys and processes it must remain vigilant toward the identification and control of new types of defects.

  13. Nickel-Based Superalloy Resists Embrittlement by Hydrogen

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan; Chen, PoShou

    2008-01-01

    A nickel-based superalloy that resists embrittlement by hydrogen more strongly than does nickel alloy 718 has been developed. Nickel alloy 718 is the most widely used superalloy. It has excellent strength and resistance to corrosion as well as acceptably high ductility, and is recognized as the best alloy for many high-temperature applications. However, nickel alloy 718 is susceptible to embrittlement by hydrogen and to delayed failure and reduced tensile properties in gaseous hydrogen. The greater resistance of the present nickel-based superalloy to adverse effects of hydrogen makes this alloy a superior alternative to nickel alloy 718 for applications that involve production, transfer, and storage of hydrogen, thereby potentially contributing to the commercial viability of hydrogen as a clean-burning fuel. The table shows the composition of the present improved nickel-based superalloy in comparison with that of nickel alloy 718. This composition was chosen to obtain high resistance to embrittlement by hydrogen while maintaining high strength and exceptional resistance to oxidation and corrosion. The most novel property of this alloy is that it resists embrittlement by hydrogen while retaining tensile strength greater than 175 kpsi (greater than 1.2 GPa). This alloy exhibits a tensile elongation of more than 20 percent in hydrogen at a pressure of 5 kpsi (approximately equal to 34 MPa) without loss of ductility. This amount of elongation corresponds to 50 percent more ductility than that exhibited by nickel alloy 718 under the same test conditions.

  14. Weldability of a Nickel-based Superalloy

    NASA Technical Reports Server (NTRS)

    Kalinowski, Joseph M.

    1994-01-01

    The electron beam welding process is used to investigate the weldability of the Ni-based superalloy Udimet 720LI. This is a modified form of the alloy Udimet 720, which has reduced concentrations of interstitial elements such as boron, silicon, and carbon. The history of high strength superalloys like this one suggests that welding will be difficult because of their tendency towards hot cracking during the welding process, or strain-age cracking during the post-weld aging process. Studies were done on several sizes of weldability test specimens to determine if Udimet 720LI will exhibit cracking tendencies. It was found that the alloy was not susceptible to hot cracking unless it had received the four-step aging heat treatment that is recommended by the manufacturer. It was also found that a restrained weldment is susceptible to strain-age cracking; however, if the weldment is allowed to deform then warpage can occur instead of cracking.

  15. Measurement of size-dependent composition variations for gamma prime (γ') precipitates in an advanced nickel-based superalloy.

    PubMed

    Chen, Y Q; Slater, T J A; Lewis, E A; Francis, E M; Burke, M G; Preuss, M; Haigh, S J

    2014-09-01

    Energy-dispersive X-ray (EDX) spectroscopy in the scanning transmission electron microscope (STEM) has been used to demonstrate the presence of size-dependent compositional variation for L12-structured Ni3Al-type gamma-prime (γ') precipitates within a commercial RR1000 Ni-based superalloy. This semi-quantitative elemental analysis has been achieved using electrochemical extraction of the γ' precipitates from the γ matrix. The applicability of this approach to size-dependent compositional analysis of precipitates was confirmed by a comparison of the size distribution for the extracted precipitates with those present in traditional electropolished foil specimens in the size range 20-250nm. By applying suitable thickness-dependent absorption-corrections we have demonstrated that the composition of γ' precipitates in our material depends on the size of the precipitate in the range of 5nm to 3μm. In particular, the Al content was observed to increase in smaller γ' precipitates while Ti and Ta contents are constant for all sizes of precipitate. Hf was observed to be present only in the largest precipitates. This type of local compositional information provides invaluable input to assess the accuracy of microstructural modelling for these complex alloys and provides new evidence supporting the importance of anti-site diffusion. PMID:24814008

  16. Measurement of size-dependent composition variations for gamma prime (γ') precipitates in an advanced nickel-based superalloy.

    PubMed

    Chen, Y Q; Slater, T J A; Lewis, E A; Francis, E M; Burke, M G; Preuss, M; Haigh, S J

    2014-09-01

    Energy-dispersive X-ray (EDX) spectroscopy in the scanning transmission electron microscope (STEM) has been used to demonstrate the presence of size-dependent compositional variation for L12-structured Ni3Al-type gamma-prime (γ') precipitates within a commercial RR1000 Ni-based superalloy. This semi-quantitative elemental analysis has been achieved using electrochemical extraction of the γ' precipitates from the γ matrix. The applicability of this approach to size-dependent compositional analysis of precipitates was confirmed by a comparison of the size distribution for the extracted precipitates with those present in traditional electropolished foil specimens in the size range 20-250nm. By applying suitable thickness-dependent absorption-corrections we have demonstrated that the composition of γ' precipitates in our material depends on the size of the precipitate in the range of 5nm to 3μm. In particular, the Al content was observed to increase in smaller γ' precipitates while Ti and Ta contents are constant for all sizes of precipitate. Hf was observed to be present only in the largest precipitates. This type of local compositional information provides invaluable input to assess the accuracy of microstructural modelling for these complex alloys and provides new evidence supporting the importance of anti-site diffusion.

  17. Weldability and microstructure development in nickel-base superalloys

    SciTech Connect

    David, S.A.; Babu, S.S.; Vitek, J.M.

    1997-11-01

    The integrity of nickel-base superalloy single-crystal welds depends on the weld cracking tendency, weld metal dendrite selection process, stray crystal formation, and macro- and microstructure development. These phenomena have been investigated in commercial nickel-base superalloy single crystal welds. During electron beam and laser beam welding, transverse and longitudinal weld cracking occurred. However, the weld cracking tendency was reduced with preheating. Most of the dendritic growth pattern development in these welds can be explained by a geometric model. However, the welds also contained misoriented stray crystals, which were frequently associated with weld cracks. The formation of stray crystals was related to thermal and constitutional supercooling effects. Fine-scale elemental partitioning between {gamma} and {gamma}{prime} phase was measured with atom-probe field-ion microscopy. Marked differences in partitioning characteristics in two welds were observed and are related to differences in cooling rates. In this paper, the modeling tools available to describe the above are reviewed.

  18. Effects of cobalt in nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Tien, J. K.; Jarrett, R. N.

    1983-01-01

    The role of cobalt in a representative wrought nickel-base superalloy was determined. The results show cobalt affecting the solubility of elements in the gamma matrix, resulting in enhanced gamma' volume fraction, in the stabilization of MC-type carbides, and in the stabilization of sigma phase. In the particular alloy studied, these microstructural and microchemistry changes are insufficient in extent to impact on tensile strength, yield strength, and in the ductilities. Depending on the heat treatment, creep and stress rupture resistance can be cobalt sensitive. In the coarse grain, fully solutioned and aged condition, all of the alloy's 17% cobalt can be replaced by nickel without deleteriously affecting this resistance. In the fine grain, partially solutioned and aged condition, this resistance is deleteriously affected only when one-half or more of the initial cobalt content is removed. The structure and property results are discussed with respect to existing theories and with respect to other recent and earlier findings on the impact of cobalt, if any, on the performance of nickel-base superalloys.

  19. Anisotropy of nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Maier, R. D.; Dreshfield, R. L.

    1980-01-01

    The effects of crystal orientation on the mechanical properties of single crystals of the nickel-based superalloy Mar-M247 are investigated. Tensile tests at temperatures from 23 to 1093 C and stress rupture tests at temperatures from 760 to 1038 C were performed for 52 single crystals at various orientations. During tensile testing between 23 and 760 C, single crystals with high Schmid factors were found to be favorably oriented for slip and to exhibit lower strength and higher ductility than those with low Schmid factors. Crystals which required large rotations to become oriented for cross slip were observed to have the shortest stress rupture lives at 760 C, while those which required little or no rotation had the longest lives. In addition, stereographic triangles obtained for Mar-M247 and Mar-M200 single crystals reveal that crystals with orientations near the -111 had the highest lives, those near the 001 had high lives, and those near the 011 had low lives.

  20. Compositional Effects on Nickel-Base Superalloy Single Crystal Microstructures

    NASA Technical Reports Server (NTRS)

    MacKay, Rebecca A.; Gabb, Timothy P.; Garg,Anita; Rogers, Richard B.; Nathal, Michael V.

    2012-01-01

    Fourteen nickel-base superalloy single crystals containing 0 to 5 wt% chromium (Cr), 0 to 11 wt% cobalt (Co), 6 to 12 wt% molybdenum (Mo), 0 to 4 wt% rhenium (Re), and fixed amounts of aluminum (Al) and tantalum (Ta) were examined to determine the effect of bulk composition on basic microstructural parameters, including gamma' solvus, gamma' volume fraction, volume fraction of topologically close-packed (TCP) phases, phase chemistries, and gamma - gamma'. lattice mismatch. Regression models were developed to describe the influence of bulk alloy composition on the microstructural parameters and were compared to predictions by a commercially available software tool that used computational thermodynamics. Co produced the largest change in gamma' solvus over the wide compositional range used in this study, and Mo produced the largest effect on the gamma lattice parameter and the gamma - gamma' lattice mismatch over its compositional range, although Re had a very potent influence on all microstructural parameters investigated. Changing the Cr, Co, Mo, and Re contents in the bulk alloy had a significant impact on their concentrations in the gamma matrix and, to a smaller extent, in the gamma' phase. The gamma phase chemistries exhibited strong temperature dependencies that were influenced by the gamma and gamma' volume fractions. A computational thermodynamic modeling tool significantly underpredicted gamma' solvus temperatures and grossly overpredicted the amount of TCP phase at 982 C. Furthermore, the predictions by the software tool for the gamma - gamma' lattice mismatch were typically of the wrong sign and magnitude, but predictions could be improved if TCP formation was suspended within the software program. However, the statistical regression models provided excellent estimations of the microstructural parameters based on bulk alloy composition, thereby demonstrating their usefulness.

  1. Methodology Developed for Modeling the Fatigue Crack Growth Behavior of Single-Crystal, Nickel-Base Superalloys

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Because of their superior high-temperature properties, gas generator turbine airfoils made of single-crystal, nickel-base superalloys are fast becoming the standard equipment on today's advanced, high-performance aerospace engines. The increased temperature capabilities of these airfoils has allowed for a significant increase in the operating temperatures in turbine sections, resulting in superior propulsion performance and greater efficiencies. However, the previously developed methodologies for life-prediction models are based on experience with polycrystalline alloys and may not be applicable to single-crystal alloys under certain operating conditions. One of the main areas where behavior differences between single-crystal and polycrystalline alloys are readily apparent is subcritical fatigue crack growth (FCG). The NASA Lewis Research Center's work in this area enables accurate prediction of the subcritical fatigue crack growth behavior in single-crystal, nickel-based superalloys at elevated temperatures.

  2. Anisotropy of high temperature strength in precipitation-hardened nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Nakagawa, Y. G.; Terashima, H.; Yoshizawa, H.; Ohta, Y.; Murakami, K.

    1986-01-01

    The anisotropy of high temperature strength of nickel-base superalloy, Alloy 454, in service for advanced jet engine turbine blades and vanes, was investigated. Crystallographic orientation dependence of tensile yield strength, creep and creep rupture strength was found to be marked at about 760C. In comparison with other single crystal data, a larger allowance in high strength off-axial orientation from the 001 axis, and relatively poor strength at near the -111 axis were noted. From transmission electron microscopy the anisotropic characteristics of this alloy were explained in terms of available slip systems and stacking geometries of gamma-prime precipitate cuboids which are well hardened by a large tantalum content. 100 cube slip was considered to be primarily responsible for the poor strength of the -111 axis orientation replacing the conventional 111 plane slip systems.

  3. Understanding the roles of the strategic element cobalt in nickel base superalloys

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Dreshfield, R. L.

    1983-01-01

    The United States imports over 90% of its cobalt, chromium, columbium, and tantalum, all key elements in high temperature nickel base superalloys for aircraft gas turbine disks and airfoils. Research progress in understanding the roles of cobalt and some possible substitutes effects on microstructure, mechanical properties, and environmental resistance of turbine alloys is discussed.

  4. New approach for assessing the weldability of precipitation-strengthened nickel-base superalloys

    NASA Astrophysics Data System (ADS)

    Moosavy, Homam Naffakh; Aboutalebi, Mohammad-Reza; Seyedein, Seyed Hossein; Khodabakhshi, Meisam; Mapelli, Carlo

    2013-12-01

    A new procedure was proposed for evaluating the weldability of nickel-base superalloys. The theory is on the basis of two microstructural patterns. In pattern I, the weld microstructure exhibits severe alloying segregation, many low-melting eutectic structures, and low weldability. The weld requires a weaker etchant and a shorter time for etching. In pattern II, the weld microstructure displays less alloying segregation, low quantity of eutectic structures, and high weldability. The weld needs a stronger etchant and a longer time for etching. Five superalloys containing different amounts of Nb and Ti were designed to verify the patterns. After welding operations, the welds were etched by four etchants with different corrosivities. The weldability was determined by TG-DSC measurements. The metallography and weldability results confirmed the theoretic patterns. Finally, the etchant corrosivity and etching time were proposed as new criteria to evaluate the weldability of nickel-base superalloys.

  5. Process of welding gamma prime-strengthened nickel-base superalloys

    DOEpatents

    Speigel, Lyle B.; White, Raymond Alan; Murphy, John Thomas; Nowak, Daniel Anthony

    2003-11-25

    A process for welding superalloys, and particularly articles formed of gamma prime-strengthened nickel-base superalloys whose chemistries and/or microstructures differ. The process entails forming the faying surface of at least one of the articles to have a cladding layer of a filler material. The filler material may have a composition that is different from both of the articles, or the same as one of the articles. The cladding layer is machined to promote mating of the faying surfaces, after which the faying surfaces are mated and the articles welded together. After cooling, the welded assembly is free of thermally-induced cracks.

  6. Manufacturing of nickel-base superalloys with improved high-temperature performance

    SciTech Connect

    McKamey, C.G.; George, E.P.; Liu, C.T.; Horton, J.A.; Carmichael, C.A.; Kennedy, R.L.; Cao, W.D.

    2000-01-01

    This report summarizes the results of research conducted as part of CRADA ORNL95-0327 between Oak Ridge National Laboratory and Teledyne Allvac (now Allvac, an Allegheny Teledyne Co.). The objective was to gain a better understanding of the role of trace elements in nickel-based superalloys, with the ultimate goal of enhancing performance without significantly increasing production cost. Two model superalloys, IN 718 and Waspaloy, were selected for this study, and the synergistic effects of P and B additions on creep and stress rupture properties were determined. Wherever possible the underlying physical mechanisms responsible for the observed effects were investigated.

  7. Understanding the roles of the strategic element cobalt in nickel base superalloys

    NASA Technical Reports Server (NTRS)

    Stephens, J. B.; Dreshfield, R. L.

    1984-01-01

    Research progress in understanding the effects of cobalt and some possible substitute on microstructure, mechanical properties, and environmental resistance of turbine alloys is discussed. The United States imports over 90 percent of its cobalt, chromium, tantalum and columbium, all key elements in high temperature nickel base superalloys for aircraft gas turbine disks and airfoils. NASA, through joint government/industry/university teams, undertook a long range research program aimed at reducing or eliminating these strategic elements by examining their basic roles in superalloys and identifying viable substitutes.

  8. Strainrange partitioning behavior of the nickel-base superalloys, Rene' 80 and in 100

    NASA Technical Reports Server (NTRS)

    Halford, G. R.; Nachtigall, A. J.

    1978-01-01

    A study was made to assess the ability of the method of Strainrange Partitioning (SRP) to both correlate and predict high-temperature, low cycle fatigue lives of nickel base superalloys for gas turbine applications. The partitioned strainrange versus life relationships for uncoated Rene' 80 and cast IN 100 were also determined from the ductility normalized-Strainrange Partitioning equations. These were used to predict the cyclic lives of the baseline tests. The life predictability of the method was verified for cast IN 100 by applying the baseline results to the cyclic life prediction of a series of complex strain cycling tests with multiple hold periods at constant strain. It was concluded that the method of SRP can correlate and predict the cyclic lives of laboratory specimens of the nickel base superalloys evaluated in this program.

  9. Welding of nickel-base superalloys having a nil-ductility range

    NASA Technical Reports Server (NTRS)

    Smashey, Russell W. (Inventor); Kelly, Thomas J. (Inventor); Snyder, John H. (Inventor); Sheranko, Ronald L. (Inventor)

    1999-01-01

    An article made of a nickel-base superalloy having a nil-ductility range from the solidus temperature of the alloy to about 600.degree. F. below the solidus temperature is welded, as for example in the weld repair of surface cracks, by removing foreign matter from the area to be welded, first stress relieving the article, adjusting the temperature of the article to a welding temperature of from about 1800.degree. F. to about 2100.degree. F., welding a preselected area in an inert atmosphere at the welding temperature, and second stress relieving the article. Welding is preferably accomplished by striking an arc in the preselected area so as to locally melt the alloy in the preselected area, providing a filler metal having the same composition as the nickel-based superalloy of the article, and feeding the filler metal into the arc so that the filler metal is melted and fused with the article to form a weldment upon solidification.

  10. Evolution of Microstructure in a Nickel-based Superalloy as a Function of Ageing Time

    SciTech Connect

    Chen, Wei-Ren; Smith, Gregory Scott; Porcar, L.; Liaw, Peter K; Kai, Ji-Jung; Ren, Yang

    2011-01-01

    An experimental investigation, combining synchrotron X-ray powder diffraction, small-angle neutron-scattering, and transmission electron microscopy, has been undertaken to study the microstructure of nanoprecipitates in a nickel-based superalloy. Upon increasing the ageing time during a heat-treatment process, the average size of the precipitates first decreases before changing to a monotonical growth stage. Possible reasons for this observed structural evolution, which is predicted thermodynamically, are suggested.

  11. Mechanism of beneficial effect of tantalum in hot corrosion of nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Fryburg, G. C.; Stearns, C. A.; Kohl, F. J.

    1977-01-01

    X-ray diffraction and electron microprobe analyses were used to examine a prominent NaTaO3 pattern formed in a number of nickel-base superalloys. It is found that a beneficial effect of tantalum with respect to hot corrosion attack arises from the ability of Ta2O5 to tie up Na2O and prevent the formation of a molten Na2MoO4 phase.

  12. Synthetic Microstructure-Based Lifing of Nickel-Based Superalloys

    NASA Astrophysics Data System (ADS)

    Tucker, Joseph C.

    This work focuses on the root cause of life limiting behavior in Ni-based superalloys for high pressure and temperature turbine disks applications in low cycle fatigue (LCF) by generating statistical volume elements (SVEs) of directly measured 3D microstructures for finite element method (FEM) simulations with crystal plasticity. Synthetic microstructures with experimentally determined microstructurally small fatigue crack (MSFC) weakest link features of as large as (ALA) grains and long annealing twins comprise the test cases. Upper limit truncated log-normal distributions account for the log-normal upper tail departure in grain size distributions of Ni-based superalloys more accurately representing ALA grains. Probability plots quantify the log-normality of grain sizes more effectively than traditional histograms. Twins are inserted into synthetic microstructures according to the coherent Sigma3 orientation relationship. A 3D measured dataset of the Inconel 100 (IN100) validates the Saltykov method stereology technique for estimating 3D grain size distributions from 2D; the 3D grain size distribution mean field and upper tail of IN100 is accurately predicted. The Saltykov method gave 3D grain sizes from a Rene 88 Damage Tolerant (R88DT) 2D dataset resulting in fatigue SVEs of approximately 1.5 million elements and 200 grains from FEM sensitivity studies. Changing mesh resolution minimally impacted global damage response, but converging locally requires significantly higher refinement. Fatigue interrogating FEM studies evolved hot spots in the local MSFC environment in one SVE, but not in another SVE with different crystallographic orientations, suggesting strong 3D full-field neighbor effects. The study revealed a need for slip line length considerations in crystal plasticity to better capture life limiting behavior. The findings point towards strictly limiting the ALA grain size in Ni-based superalloys to extend service life.

  13. A concept for the EQ coating system for nickel-based superalloys

    NASA Astrophysics Data System (ADS)

    Kawagishi, K.; Sato, A.; Harada, H.

    2008-07-01

    Nickel-based single-crystal superalloys with high concentrations of refractory elements are prone to generate a diffusion layer called a secondary reaction zone (SRZ) beneath their bond coating during long exposure to high temperatures. The SRZ causes a reduction of the load-bearing cross section and it is detrimental to the creep properties of thin-walled turbine airfoils. In this study, a new bond coat system, “EQ coating,” which is thermodynamically stable and suppresses SRZ has been proposed. Diffusion couples of coating materials and substrate alloys were made and heat treated at 1,100°C for 300 h and 1,000 h. Cyclic oxidation examinations were carried out at 1,100°C in air and the oxidation properties of EQ coating materials were discussed. High-velocity frame-sprayed EQ coatings designed for second-generation nickel-based superalloys were deposited on fourth-and fifth-generation nickel-based superalloys, and the stability of the microstructure at the interface and creep property of the coating system were investigated.

  14. Wave propagation in an anisotropic nickel-based superalloy

    PubMed

    Amulele; Every

    2000-03-01

    The effects of elastic anisotropy on ultrasound propagation in a nickel-based single crystal test component are studied using a 25 MHz focused probe in a water immersion system. Anisotropy gives rise to directionally dependent acoustic wavespeeds, beam steering, acoustic energy focusing and mode conversion for normal incidence. Transverse mode echoes are particularly strong in the vicinity of crystallographic directions in which the Gaussian curvature of the slowness surface is zero and divergence of the echo amplitude is predicted on the basis of the stationary phase approximation. There are other directions where the transverse mode echoes vanish for symmetry reasons. The longitudinal mode echo amplitude also shows significant variation with direction. Overall there is good agreement between the echo signal arrival times and amplitudes we measure and calculation. Progress in applying this technique to gas turbine blades is reported. PMID:10829669

  15. Wave propagation in an anisotropic nickel-based superalloy

    PubMed

    Amulele; Every

    2000-03-01

    The effects of elastic anisotropy on ultrasound propagation in a nickel-based single crystal test component are studied using a 25 MHz focused probe in a water immersion system. Anisotropy gives rise to directionally dependent acoustic wavespeeds, beam steering, acoustic energy focusing and mode conversion for normal incidence. Transverse mode echoes are particularly strong in the vicinity of crystallographic directions in which the Gaussian curvature of the slowness surface is zero and divergence of the echo amplitude is predicted on the basis of the stationary phase approximation. There are other directions where the transverse mode echoes vanish for symmetry reasons. The longitudinal mode echo amplitude also shows significant variation with direction. Overall there is good agreement between the echo signal arrival times and amplitudes we measure and calculation. Progress in applying this technique to gas turbine blades is reported.

  16. Temperature dependence of the structural order in the {gamma}{prime} phase of nickel base superalloy

    SciTech Connect

    Royer, A.; Bastie, P.; Veron, M.

    1999-03-19

    Single crystal nickel base superalloys are used for the high-temperature parts of aircraft engines like turbine blades. Their good mechanical properties at high temperature are related to the precipitation of an ordered {gamma}{prime} phase which induces a structural hardening of the material. The {gamma}{prime} phase has an ordered L1{sub 2} structure while the {gamma} matrix is disordered and has a FCC structure. The volume fraction of f{gamma}{prime} of the {gamma}{prime} phase evolves with the temperature and a complete solutionizing occurs above 1,280 C in the AM1 superalloy. The {gamma}{prime} phase of Ni based superalloys is usually analyzed through its prototype Ni{sub 3}Al. As the Ni{sub 3}Al structure remains totally ordered up to temperature very close to the melting point, it is commonly assumed in superalloys that the {gamma}{prime} phase precipitates are fully ordered up to their solutionizing and that the volume fraction of the precipitates is equivalent to the volume fraction of the ordered phase. However, in superalloys, it is difficult to separate experimentally the effects related to the solutionizing of the precipitates from those due to a possible partial disordering of the {gamma}{prime} phase and this assumption has not been verified yet. The aim of this paper is to study the structural order in the {gamma}{prime} phase of a superalloy.

  17. Development of a hydrogen-based annealing process for desulfurization of single crystalline, nickel-based superalloy. Final report

    SciTech Connect

    Smith, M.; Mickle, T.H.; Frazier, W.E.; Waldman, J.

    1994-11-05

    The presence of minor amounts of sulfur (1-10 ppm) in nickel-based superalloys has been associated with reduced oxidation resistance and premature spallation of protective coatings. A hydrogen annealing process has been developed by NAWCADWAR which effectively reduces the sulfur content of superalloys. The conditions which allow effective desulfurization are delineated. Diffusion of sulfur through the superalloy is found to be the rate controlling step for the process.

  18. Mechanical properties of nanostructured nickel based superalloy Inconel 718

    NASA Astrophysics Data System (ADS)

    Mukhtarov, Sh; Ermachenko, A.

    2010-07-01

    This paper will describe the investigations of a nanostructured (NS) state of nickel based INCONEL® alloy 718. This structure was generated in bulk semiproducts by severe plastic deformation (SPD) via multiple isothermal forging (MIF) of a coarse-grained alloy. The initial structure consisted of γ-phase grains with disperse precipitations of γ"-phase in the forms of discs, 50-75 nm in diameter and 20 nm in thickness. The MIF generated structures possess a large quantity of non-coherent plates and rounded precipitations of δ-phase, primarily along grain boundaries. In the duplex (γ+δ) structure the grains have high dislocation density and a large number of nonequilibrium boundaries. Investigations to determine mechanical properties of the alloy in a nanostructured state were carried out. Nanocrystalline Inconel 718 (80 nm) possesses a very high room-temperature strength after SPD. Microcrystalline (MC) and NS states of the alloy were subjected to strengthening thermal treatment, and the obtained results were compared in order to determine their mechanical properties at room and elevated temperatures.

  19. Creep deformation mechanism mapping in nickel base disk superalloys

    DOE PAGES

    Smith, Timothy M.; Unocic, Raymond R.; Deutchman, Hallee; Mills, Michael J.

    2016-05-10

    We investigated the creep deformation mechanisms at intermediate temperature in ME3, a modern Ni-based disk superalloy, using diffraction contrast imaging. Both conventional transmission electron microscopy (TEM) and scanning TEM were utilised. Distinctly different deformation mechanisms become operative during creep at temperatures between 677-815 °C and at stresses ranging from 274 to 724 MPa. Both polycrystalline and single-crystal creep tests were conducted. The single-crystal tests provide new insight into grain orientation effects on creep response and deformation mechanisms. Creep at lower temperatures (≤760 °C) resulted in the thermally activated shearing modes such as microtwinning, stacking fault ribbons and isolated superlattice extrinsicmore » stacking faults. In contrast, these faulting modes occurred much less frequently during creep at 815 °C under lower applied stresses. Instead, the principal deformation mode was dislocation climb bypass. In addition to the difference in creep behaviour and creep deformation mechanisms as a function of stress and temperature, it was also observed that microstructural evolution occurs during creep at 760 °C and above, where the secondary coarsened and the tertiary precipitates dissolved. Based on this work, a creep deformation mechanism map is proposed, emphasising the influence of stress and temperature on the underlying creep mechanisms.« less

  20. Metallurgical instabilities during the high temperature low cycle fatigue of nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Antolovich, S. D.; Jayaraman, N.

    1983-01-01

    An investigation is made of the microstructural instabilities that affect the high temperature low cycle fatigue (LCF) life of nickel-base superalloys. Crack initiation processes, provoked by the formation of carbides and the coarsening of the grains of the material at high temperatures are discussed. Experimental results are examined, and it is concluded that LCF behavior can be understood more fully only if details of the material and its dynamic behavior at high temperatures are considered. The effects of high stress, dislocation debris, and increasing environmental damage on the life of the alloy are discussed.

  1. Effects of cobalt on the hot workability of nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Jarrett, R. N.; Collier, J. P.; Tien, J. K.

    1984-01-01

    The effect of cobalt on the workability of nickel-base superalloys is examined with reference to experimental results for four heats of alloys based on the Nimonic 115 composition with varying amounts of nickel substituted for the nominal 14 percent cobalt. It is shown that Co lowers the gamma-prime solvus, which in turn lowers the Cr23C6 carbide solvus. It is further shown that these solvus temperatures bracket the hot working range for the alloys. However, thermomechanical processing modifications reflecting the effect of Co on the gamma-prime and carbide solvi are shown to restore the workability and the properties of alloys with little or no cobalt.

  2. Influence of Solid Solution Hardening on Creep Properties of Single-Crystal Nickel-Based Superalloys

    NASA Astrophysics Data System (ADS)

    Fleischmann, Ernst; Konrad, Christian; Preußner, Johannes; Völkl, Rainer; Affeldt, Ernst; Glatzel, Uwe

    2015-03-01

    Improving the creep resistance of the matrix by alloying with refractory elements is a major strengthening effect in nickel-based superalloy with rhenium as one of the most effective elements. In this work, the influence of rhenium on creep properties of single-phase single crystals with varying rhenium content and matrix-near composition is investigated. The use of single-crystalline material leads to very distinct results which are not deteriorated by grain boundary effects. So the strengthening effect can be solely attributed to the alloying element rhenium and is quantified for the first time. By comparing the creep strength of two matrix compositions with the corresponding single-crystal superalloys using the threshold stress concept, the potential of creep strengthening of the matrix in two-phase single-crystal alloys is quantified.

  3. Microstructure-property relationships in directionally solidified single-crystal nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Mackay, Rebecca A.; Nathal, Michael V.

    1988-01-01

    This paper discusses some of the microstructural features which influence the creep properties of directionally solidified and single-crystal nickel-base superalloys. Gamma prime precipitate size and morphology, gamma-gamma (prime) lattice mismatch, phase instability, alloy composition, and processing variations are among the factors considered. Recent experimental results are reviewed and related to the operative deformation mechanisms and to the corresponding mechanical properties. Special emphasis is placed on the creep behavior of single-crystal superalloys at high temperatures, where directional gamma (prime) coarsening is prominent, and at lower temperatures, where gamma (prime) coarsening rates are significantly reduced. It can be seen that very subtle changes in microstructural features can have profound effects on the subsequent properties of these materials.

  4. Microstructure-property relationships in directionally solidified single crystal nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Nathal, M. V.

    1986-01-01

    Some of the microstructural features which influence the creep properties of directionally solidified and single crystal nickel-base superalloys are discussed. Gamma precipitate size and morphology, gamma-gamma lattice mismatch, phase instability, alloy composition, and processing variations are among the factors considered. Recent experimental results are reviewed and related to the operative deformation mechanisms and to the corresponding mechanical properties. Special emphasis is placed on the creep behavior of single crystal superalloys at high temperatures, where directional gamma coarsening is prominent, and at lower temperatures, where gamma coarsening rates are significantly reduced. It can be seen that very subtle changes in microstructural features can have profound effects on the subsequent properties of these materials.

  5. Stereological characterization of {gamma}' phase precipitation in CMSX-6 monocrystalline nickel-base superalloy

    SciTech Connect

    Szczotok, Agnieszka; Richter, Janusz; Cwajna, Jan

    2009-10-15

    The purpose of this investigation was to study in detail the means to quantitatively evaluate {gamma}' phase precipitation. Many of the mechanical properties of superalloys are directly influenced by the presence of the {gamma}' (gamma prime) precipitate phase dispersed in a {gamma} matrix phase. The {gamma}' precipitates act as effective barriers to dislocation motion and restrict plastic deformation, particularly at high temperatures. Due to this, it is essential to accurately quantify the {gamma}' precipitate size, volume fraction and distribution. Investigations based on quantitative metallography and image analysis were performed on a monocrystalline nickel-base superalloy taking into consideration various {gamma}' precipitate sizes present in that alloy microstructure. The authors of the present paper propose a new method of quantifying the total volume fraction of the {gamma}' phase applying images of the microstructure with {gamma}' phase precipitates registered using light microscopy, scanning electron microscopy (at two different magnifications) and scanning transmission electron microscopy.

  6. Microstructures induced by a stress gradient in a nickel-based superalloy

    SciTech Connect

    Ignat, M.; Buffiere, J.Y.; Chaix, J.M. )

    1993-03-01

    The evolution of the microstructure of single crystals of a nickel-based superalloy during high temperature (1,323 K, 1,050 C) creep in bending has been studied. Bending provides both tensile and compressive stress gradients, consequently the effects of varying stress conditions on the evolution of the morphology of the [gamma][prime] precipitates can be determined from a single specimen. The morphological changes were analyzed by scanning electron microscopy using image analysis techniques and by transmission electron microscopy, then described by dimensionless parameters. The authors discuss the dependence of the morphological changes in the superalloy on the stresses acting in the sample (magnitude and sign). The authors also discuss the driving mechanisms for the observed morphological changes.

  7. Replacing critical and strategic refractory metal elements in nickel-base superalloys. [NASA's COSAM program

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Dreshfield, R. L.; Nathal, M. V.

    1983-01-01

    Because of the import status and essential nature of their use, cobalt, chromium, tantalum, and niobium were identified as strategic and critical in the aerospace industry. NASA's Conservation of Strategic Aerospace Materials (COSAM) program aims to reduce the need for strategic materials used in gas turbine engines. Technological thrusts in two major areas are under way to meet the primary objective of conserving the use of strategic materials in nickelbase superalloys. These thrusts consist of strategic element substitution and alternative material identification. The program emphasizes cooperative research teams involving NASA Lewis Research Center, universities, and industry. The adoption of refractory metals in nickel-base superalloys is summarized including their roles in mechanical strengthening and environmental resistance; current research activities under way in the COSAM Program are presented as well as research findings to date.

  8. Microstructural indicators of transition mechanisms in time-dependent fatigue crack growth in nickel base superalloys

    NASA Astrophysics Data System (ADS)

    Heeter, Ann E.

    Gas turbine engines are an important part of power generation in modern society, especially in the field of aerospace. Aerospace engines are design to last approximately 30 years and the engine components must be designed to survive for the life of the engine or to be replaced at regular intervals to ensure consumer safety. Fatigue crack growth analysis is a vital component of design for an aerospace component. Crack growth modeling and design methods date back to an origin around 1950 with a high rate of accuracy. The new generation of aerospace engines is designed to be efficient as possible and require higher operating temperatures than ever seen before in previous generations. These higher temperatures place more stringent requirements on the material crack growth performance under creep and time dependent conditions. Typically the types of components which are subject to these requirements are rotating disk components which are made from advanced materials such as nickel base superalloys. Traditionally crack growth models have looked at high temperature crack growth purely as a function of temperature and assumed that all crack growth was either controlled by a cycle dependent or time dependent mechanism. This new analysis is trying to evaluate the transition between cycle-dependent and time-dependent mechanism and the microstructural markers that characterize this transitional behavior. The physical indications include both the fracture surface morphology as well as the shape of the crack front. The research will evaluate whether crack tunneling occurs and whether it consistently predicts a transition from cycle-dependent crack growth to time-dependent crack growth. The study is part of a larger research program trying to include the effects of geometry, mission profile and environmental effects, in addition to temperature effects, as a part of the overall crack growth system. The outcome will provide evidence for various transition types and correlate those

  9. Effect of crystallographic orientation on plastic deformation of single crystal nickel-base superalloys

    NASA Astrophysics Data System (ADS)

    Westbrooke, Eboni F.

    Nickel-base superalloys, with gamma/gamma' microstructure, are the primary material used in turbines for aerospace applications. The blades in the hottest region of the turbine engine are made of single crystal Ni-base superalloys. It has been shown that the critical resolved shear stress (CRSS) of these materials is orientation dependent (also known as non-Schmid effect). The purpose of this research was to investigate the plastic deformation mechanisms of single crystal Ni-base superalloys as a function of crystallographic orientation in order to understand the factors that contribute to the non-Schmid effect. The superalloys in this study possessed alloying elements in amounts which defined them as 1st and 2nd generation superalloys. Tensile samples of various orientations were loaded to different strain levels. The mechanisms of plastic deformation were characterized by optical and scanning electron microscopy (SEM) observations of deformation bands as well as the dislocation structures using transmission electron microscopy (TEM). It was confirmed that the CRSS of the single crystals did not follow Schmid's law and the near <111> specimens showed the lowest values. The degree of non-Schmid behavior in the <111> specimens was diminished by HIP'ing, which resulted in closure of solidification pores. Furthermore, it was shown that the CRSS for the <100> loaded samples was smallest when loaded along the secondary dendrite arms. The slip analysis by optical microscopy showed that the deformation bands did not follow the expected {111} slip planes for all samples. Studies in SEM proved that those slip bands that followed the {111} planes were associated with extensive shearing of gamma' particles. In addition, it was found that the presence of tri-axial stress states within the macrostructure influenced the deformation path significantly. The TEM observations of deformed specimens revealed that plastic deformation took place mainly in the gamma channels in specimens

  10. Hydrogen induced fracture characteristics of single crystal nickel-based superalloys

    NASA Technical Reports Server (NTRS)

    Chen, Po-Shou; Wilcox, Roy C.

    1990-01-01

    A stereoscopic method for use with x ray energy dispersive spectroscopy of rough surfaces was adapted and applied to the fracture surfaces single crystals of PWA 1480E to permit rapid orientation determinations of small cleavage planes. The method uses a mathematical treatment of stereo pair photomicrographs to measure the angle between the electron beam and the surface normal. One reference crystal orientation corresponding to the electron beam direction (crystal growth direction) is required to perform this trace analysis. The microstructure of PWA 1480E was characterized before fracture analysis was performed. The fracture behavior of single crystals of the PWA 1480E nickel-based superalloy was studied. The hydrogen-induced fracture behavior of single crystals of the PWA 1480E nickel-based superalloy was also studied. In order to understand the temperature dependence of hydrogen-induced embrittlement, notched single crystals with three different crystal growth orientations near zone axes (100), (110), and (111) were tensile tested at 871 C (1600 F) in both helium and hydrogen atmospheres at 34 MPa. Results and conclusions are given.

  11. Eddy Current Nondestructive Residual Stress Assessment in Shot-Peened Nickel-Base Superalloys

    NASA Astrophysics Data System (ADS)

    Blodgett, M. P.; Yu, F.; Nagy, P. B.

    2005-04-01

    Shot peening and other mechanical surface enhancement methods improve the fatigue resistance and foreign-object damage tolerance of metallic components by introducing beneficial near-surface compressive residual stresses and hardening the surface. However, the fatigue life improvement gained via surface enhancement is not explicitly accounted for in current engine component life prediction models because of the lack of accurate and reliable nondestructive methods that could verify the presence of compressive near-surface residual stresses in shot-peened hardware. In light of its frequency-dependent penetration depth, the measurement of eddy current conductivity has been suggested as a possible means to allow the nondestructive evaluation of subsurface residual stresses in surface-treated components. This technique is based on the so-called piezoresistivity effect, i.e., the stress-dependence of electrical resistivity. We found that, in contrast with most other materials, surface-treated nickel-base superalloys exhibit an apparent increase in electrical conductivity at increasing inspection frequencies, i.e., at decreasing penetration depths. Experimental results are presented to illustrate that the excess frequency-dependent apparent eddy current conductivity of shot-peened nickel-base superalloys can be used to estimate the absolute level and penetration depth of the compressive residual stress layer both before and after partial thermal relaxation.

  12. Prediction of rupture lifetime in thin sections of a nickel base superalloy

    SciTech Connect

    Pandey, M.C. ); Taplin, D.M.R. . School of Manufacturing, Materials and Mechanical Engineering)

    1994-09-15

    The prediction of rupture lifetime of a component can be based on the data generated from round, flat and tubular specimens. An investigation on the influence of specimen geometry on the creep behavior of Inconel alloy X-750 showed that the tubular specimen exhibited better creep performance when rupture lifetime data were compared on the basis of section size. However, the time to rupture data of all three specimen geometries merged together when compared on the basis of the volume to surface area ratio (V/S) indicating that there is a definite relationship between V/S and the rupture lifetime. This analysis is now extended in another gamma prime strengthened nickel base superalloy. The chemical composition of the alloy in wt%, is as follows: 0.07C-0.66Si-0.07Cu-0.79Fe-19.1Cr-2.35Ti-1.52Al and remainder nickel. Analysis of the rupture lifetime data of a gamma prime strengthened nickel base superalloy shows that time-to-rupture is controlled by the volume to surface area ratio. Furthermore, the normalization of the volume to surface area ratio with the grain size shows that the time-to-rupture data of two grain sizes, 55 and 250 [mu]m, can be represented by a single curve.

  13. Internal hydrogen effects on tensile properties of iron- and nickel-base superalloys

    NASA Astrophysics Data System (ADS)

    Hicks, P. D.; Altstetter, C. J.

    1990-01-01

    Two nickel-base alloys [superalloys INCONEL 718 (IN718) and INCONEL 625 (IN625)] and one iron-base superalloy (A286) were chosen to study the effects of internal H charging on their room-temperature slow strain rate mechanical behavior. Uniform internal H contents ranged from 0 to 50 wt ppm H (0 to 3000 at. ppm H), and a strain rate of 8.5 X 10-7 m/s was used with notched strip specimens. The three alloys showed varying losses in strength and ductility, and the strongest alloy, IN718, showed a decrease of 67 pet in ductility for a dissolved H content of 40 wt ppm. Superalloy A286 showed a corresponding 50 pet decrease in ductility, and IN625 showed a 29 pet loss in ductility. Fractographic evidence and the marked decrease in strength of the alloys lead the authors to conclude that the enhanced localized plasticity mechanism for H embrittlement is possibly operative in these face-centered cubic (fcc) alloys.

  14. A new method to predict the metadynamic recrystallization behavior in a typical nickel-based superalloy

    NASA Astrophysics Data System (ADS)

    Lin, Y. C.; Chen, Xiao-Min; Chen, Ming-Song; Zhou, Ying; Wen, Dong-Xu; He, Dao-Guang

    2016-06-01

    The metadynamic recrystallization (MDRX) behaviors of a typical nickel-based superalloy are investigated by two-pass hot compression tests and four conventional stress-based conventional approaches (offset stress method, back-extrapolation stress method, peak stress method, and mean stress method). It is found that the conventional stress-based methods are not suitable to evaluate the MDRX softening fractions for the studied superalloy. Therefore, a new approach, `maximum stress method,' is proposed to evaluate the MDRX softening fraction. Based on the proposed method, the effects of deformation temperature, strain rate, initial average grain size, and interpass time on MDRX behaviors are discussed in detail. Results show that MDRX softening fraction is sensitive to deformation parameters. The MDRX softening fraction rapidly increases with the increase of deformation temperature, strain rate, and interpass time. The MDRX softening fraction in the coarse-grain material is lower than that in the fine-grain material. Moreover, the observed microstructures indicate that the initial coarse grains can be effectively refined by MDRX. Based on the experimental results, the kinetics equations are established and validated to describe the MDRX behaviors of the studied superalloy.

  15. Single-crystal superalloy drives turbine advances

    SciTech Connect

    Harris, K.

    1995-04-01

    In searching for ways to improve power-to-weight ratios and fuel efficiency, gas turbine engine manufacturers invest heavily in the development and testing of new alloys. Their goal is to find turbine airfoil materials that can handle the higher operating temperatures, increased component stresses, and faster rotational speeds that are needed to increase turbine performance. Major turbine engine manufacturers find they can achieve these objectives through ultra-high performance, single-crystal superalloys -- a group of nickel-base materials that exhibit outstanding strength and surface stability at temperatures up to 85{percent} of their melting points. One such superalloy is CMSX-4, co-engineered by ingot maker Cannon-Muskegon and turbine engine manufacturers Rolls-Royce and Allison Engine Company. It is currently being used in such applications as Allison`s advanced airfoil programs.

  16. STEM analysis of the local chemical composition in the nickel-based superalloy CMSX-2 after creep at high temperature

    SciTech Connect

    Buffiere, J.Y.; Cheynet, M.C.; Ignat, M.

    1996-02-01

    High temperature creep of nickel-based superalloy single crystals is characterized by directional coalescence of the {gamma}{prime} reinforcing precipitates. The morphology of the coalesced structures depends on experimental parameters such as the sense and direction of the creep stress as well as on intrinsic parameters such as the sign of the misfit between matrix and precipitates. For single crystals of the commercial superalloy CMSX-2 submitted to <100> creep at 1,323K, the initially cuboidal {gamma}{prime} precipitates coalesce into platelets arranged perpendicular or parallel to the stress direction when the stress is in tension or in compression, respectively. So far, however, the evolution of the local chemical composition around dislocations had not been experimentally investigated in nickel-based superalloys.

  17. Effects of cobalt on structure, microchemistry and properties of a wrought nickel-base superalloy

    NASA Technical Reports Server (NTRS)

    Jarrett, R. N.; Tien, J. K.

    1982-01-01

    The effect of cobalt on the basic mechanical properties and microstructure of wrought nickel-base superalloys has been investigated experimentally by systematically replacing cobalt by nickel in Udimet 700 (17 wt% Co) commonly used in gas turbine (jet engine) applications. It is shown that the room temperature tensile yield strength and tensile strength only slightly decrease in fine-grained (disk) alloys and are basically unaffected in coarse-grained (blading) alloys as cobalt is removed. Creep and stress rupture resistances at 760 C are found to be unaffected by cobalt level in the blading alloys and decrease sharply only when the cobalt level is reduced below 8 vol% in the disk alloys. The effect of cobalt is explained in terms of gamma prime strengthening kinetics.

  18. Growth of pores during the creep of a single crystal nickel-base superalloy

    SciTech Connect

    Komenda, J.; Henderson, P.J.

    1997-12-01

    The use of single crystal (SX) nickel-base superalloys is set to increase in the future with the introduction of SX blades into land-based gas turbines for power generation. Cavities are pre-existing in SX alloys as interdendritic casting porosity, from which cracks nucleate and grow during the later stages of creep. It is generally assumed that no new cavities nucleate during creep. In this respect, cavities in SX alloys have been considered uninteresting and there have been no quantitative studies of cavities during the creep of SX alloys. However, cavities can be easily studied by optical microscopy, which could be readily developed into a remaining life assessment technique should the results prove interesting. This was the motivation for the work presented here.

  19. Fatigue and creep-fatigue deformation of several nickel-base superalloys at 650 C

    NASA Technical Reports Server (NTRS)

    Miner, R. V.; Gayda, J.; Maier, R. D.

    1982-01-01

    Transmission electron microscopy has been used to study the bulk deformation characteristics of seven nickel-base superalloys tested in fatigue and creep-fatigue at 650 C. The alloys were Waspalloy, HIP Astroloy, H plus F Astroloy, H plus F Rene 95, IN 100, MERL 76, and NASA IIB-7. The amount of bulk deformation observed in all the alloys was low. In tests with inelastic strain amplitudes less than about 0.003, only some grains exhibited yielding and the majority of those had the 110 line near the tensile axis. Deformation occurred on octahedral systems for all of the alloys except MERL 76 which also showed abundant primary cube slip. Creep-fatigue cycling occasionally produced extended faults between partial dislocations, but otherwise deformation was much the same as for fatigue cycling.

  20. Yielding and deformation behavior of the single crystal nickel-base superalloy PWA 1480

    NASA Technical Reports Server (NTRS)

    Milligan, W. W., Jr.

    1986-01-01

    Interrupted tensile tests were conducted to fixed plastic strain levels in 100 ordered single crystals of the nickel based superalloy PWA 1480. Testing was done in the range of 20 to 1093 C, at strain rate of 0.5 and 50%/min. The yield strength was constant from 20 to 760 C, above which the strength dropped rapidly and became a stong function of strain rate. The high temperature data were represented very well by an Arrhenius type equation, which resulted in three distinct temperature regimes. The deformation substructures were grouped in the same three regimes, indicating that there was a fundamental relationship between the deformation mechanisms and activation energies. Models of the yielding process were considered, and it was found that no currently available model was fully applicable to this alloy. It was also demonstrated that the initial deformation mechanism (during yielding) was frequently different from that which would be inferred by examining specimens which were tested to failure.

  1. Behavior of nickel-base superalloy single crystals under thermal-mechanical fatigue

    NASA Astrophysics Data System (ADS)

    Fleury, E.; Rémy, L.

    1994-12-01

    The thermal-mechanical fatigue behavior of AM1 nickel-base superalloy single crystals is studied using a cycle from 600 °C to 1100 °C. It is found to be strongly dependent on crystallo-graphic orientation, which leads to different shapes of the stress-strain hysteresis loops. The cyclic stress-strain response is influenced by variation in Young’s modulus, flow stress, and cyclic hardening with temperature for every crystallographic orientation. The thermalmechanical fatigue life is mainly spent in crack growth. Two main crack-initiation mechanisms occur, depending on the mechanical strain range. Oxidation-induced cracking is the dominant damage mechanism in the lifetime of interest for turbine blades.

  2. Temperature dependence of gamma-gamma prime lattice mismatch in nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Nathal, M. V.; Mackay, R. A.; Garlick, R. G.

    1985-01-01

    High temperature X-ray diffraction techniques were used to determine the gamma-gamma prime lattice mismatch of three different nickel-base superalloys at temperatures between 18 and 1000 C. The measurements were performed on oriented single-crystal disks which had been aged to produce a semicoherent gamma-gamma prime structure. The thermal expansion of the lattice parameters of the gamma and gamma-prime phases was described by a second-order polynomial expression. The expansion of the gamma-prime phase was consistently smaller than that of the gamma phase, which caused the lattice mismatch to become more negative at higher temperatures. It was also shown that high values of lattice mismatch resulted in increased rates of directional gamma-prime coarsening during elevated temperature creep exposure.

  3. The high temperature deformation in cyclic loading of a single crystal nickel-base superalloy

    NASA Technical Reports Server (NTRS)

    Gabb, T. P.; Welsch, G.

    1989-01-01

    The high temperature cyclic stress softening response of the single crystal nickel-base superalloy PWA 1480 was investigated. Specimens oriented near the 001- and 111-lines were tested at 1050 C in low-cycle fatigue and then microstructurally evaluated. The 001- and 111-line specimens had dissimilar flow behavior in monotonic tensile tests, but comparable softening in low-cycle fatigue. This softening was accompanied by rapid generation of dislocation networks at the gamma-gamma-prime interfaces and by a slower time-dependent coarsening of gamma-prime precipitates. Due to the rapid formation of a dislocation substructure at the gamma-gamma-prime interfaces, the cyclic stress softening could be modeled with an existing theory which related cyclic stress to the evolving microstructure and dislocation structure.

  4. Calibration approach to electron probe microanalysis: A study with PWA-1480, a nickel base superalloy

    NASA Technical Reports Server (NTRS)

    Terepka, F. M.; Vijayakumar, M.; Tewari, S. N.

    1989-01-01

    The utility of an indirect calibration approach in electron probe microanalysis is explored. The methodology developed is based on establishing a functional relationship between the uncorrected k-ratios and the corresponding concentrations obtained using one of the ZAF correction schemes, for all the desired elements in the concentration range of interest. In cases where a very large number of analyses are desired, such a technique significantly reduces the total time required for the microprobe analysis without any significant loss of precision in the data. A typical application of the method in the concentration mapping of the transverse cross-section of a dendrite in directionally solidified PWA-1480, a nickel-based superalloy, is described.

  5. Thermal stress development in a nickel based superalloy during weldability test

    SciTech Connect

    Feng, Z.; Zacharia, T.; David, S.A.

    1997-11-01

    A finite element model has been developed to quantitatively evaluate the local thermomechanical conditions for weld metal solidification cracking in a laboratory weldability test (the Sigmajig test). The loading mechanism in the Sigmajig test was simulated by means of nonlinear spring elements. The effects of weld pool solidification on the thermal and mechanical behaviors of the specimen were considered. An efficient algorithm was developed to include the solidification effects in the material constitutive relations. Stress/temperature/location diagrams were constructed to reveal the local stress development behind the traveling weld pool where solidification cracking occurs. Based on the concept of the material resistance to cracking and the mechanical driving force for cracking, the calculated local stress in the solidification temperature range was used to explain the experimentally observed cracking initiation behaviors of a nickel-based superalloy single crystal under different welding and loading conditions.

  6. Shock wave loading of Nickel based superalloy and microstructural features of the compacts

    NASA Astrophysics Data System (ADS)

    Sharma, A. D.; Sharma, A. K.; Thakur, N.

    2015-02-01

    Explosive shock wave loading has been employed to consolidate micro-sized nickel based IN718 superalloy powder. Cylindrical geometry configuring the various critical parameters with optimized detonation pressure has been used to consolidate the powder with desirable means. The thrust on the work is to compact the powder nearer to theoretical density having almost negligible density gradient and without melting the core of the specimen. XRD study indicates that the crystal structure of the post compacts remains the same. Shock wave loading deformed the particles as has been inferred from SEM. The variation in particle size has been measured from Laser Diffraction based Particle Size Analyzer (LDPSA). It is found that this is a rapid fast technique to produce larger and crack free compacts of metal powders without their melting and with less particle size variation.

  7. Thermal stability of the nickel-base superalloy B-1900 + Hf with tantalum variations

    NASA Technical Reports Server (NTRS)

    Harmon, B. S.; Pletka, B. J.; Janowski, G. M.

    1987-01-01

    The microstructure of the solutionized and aged nickel-base superalloy B-1900 + Hf was examined after additional aging at 982 C for 72, 250, and 1000 hours. Alloy compositions that were examined contained the normal 1.34 at. pct (4.3 wt pct) Ta as well as 0.67 at. pct and zero Ta levels. The gamma-prime phase agglomerated, became platelike in morphology, and decreased in volume fraction for all three alloys throughout the aging treatments. Changes which occurred in the gamma and gamma-prime phase compositions were nearly complete after 72 hours of aging while changes in the MC carbide composition continued throughout the aging. Blocky M6C carbides precipitated along the grain boundaries of all three alloys in the first 72 hours of aging. In addition, an acicular form of this Mo/Cr/Ni-rich carbide developed in the intragranular regions of the Ta-containing alloys.

  8. Electrochemical polarisation studies on plasma-sprayed nickel-based superalloy

    NASA Astrophysics Data System (ADS)

    Khan, M. Adam

    2015-08-01

    The plasma-sprayed NiCr-Cr2O3 and Al2O3-40 % TiO2 powders are deposited as coating on nickel-based superalloy. The electrochemical polarisation studies were carried out with 1.0 M H2SO4 solution as a corrosive medium. The corrosion current density of the coated sample was found to be decreased and exhibits better corrosion resistance than bare metal. The characterisation studies on the exposed sample result reveal that the bare metal has undergone severe intergranular attack and segregation on austenitic phase. The corrosion products formed are in the form of sulphides, and contribution of sulphur was noticed through EDS analysis.

  9. Method of improving fatigue life of cast nickel based superalloys and composition

    DOEpatents

    Denzine, Allen F.; Kolakowski, Thomas A.; Wallace, John F.

    1978-03-14

    The invention consists of a method of producing a fine equiaxed grain structure (ASTM 2-4) in cast nickel-base superalloys which increases low cycle fatigue lives without detrimental effects on stress rupture properties to temperatures as high as 1800.degree. F. These superalloys are variations of the basic nickel-chromium matrix, hardened by gamma prime [Ni.sub.3 (Al, Ti)] but with optional additions of cobalt, tungsten, molybdenum, vanadium, columbium, tantalum, boron, zirconium, carbon and hafnium. The invention grain refines these alloys to ASTM 2 to 4 increasing low cycle fatigue life by a factor of 2 to 5 (i.e. life of 700 hours would be increased to 1400 to 3500 hours for a given stress) as a result of the addition of 0.01% to 0.2% of a member of the group consisting of boron, zirconium and mixtures thereof to aid heterogeneous nucleation. The alloy is vacuum melted and heated to 250.degree.-400.degree. F. above the melting temperature, cooled to partial solidification, thus resulting in said heterogeneous nucleation and fine grains, then reheated and cast at about 50.degree.-100.degree. F. of superheat. Additions of 0.1% boron and 0.1% zirconium (optional) are the preferred nucleating agents.

  10. Thermomechanical fatigue behavior of coated and bare nickel-based superalloy single crystals

    SciTech Connect

    Chataigner, E.; Remy, L.

    1996-12-31

    The thermal-mechanical fatigue behavior of chromium-aluminum coated [001] single crystals of AM1, a nickel-base superalloy for turbine blades, is studied using a diamond shape cycle from 600 to 1,100 C. Comparison with bare specimens does not show any significant difference in thermal-mechanical fatigue nor in isothermal low cycle fatigue at high temperature. Metallographic observations on fracture surfaces and longitudinal sections of specimens tested to fatigue life or to a definite fraction of expected life have shown that the major crack tends to initiate from casting micropores in the sub-surface area very early in bare and coated specimens, under low cycle fatigue or thermal-mechanical fatigue. But the interaction between oxidation and fatigue cracking seems to play a major role. A simple model proposed by Reuchet and Remy has been identified for this single crystal superalloy. Its application to the life prediction under low cycle fatigue and thermal-mechanical fatigue for bare and coated single crystals with different orientations is shown.

  11. Characterization and Modeling of Microstructure Development in Nickel-base Superalloy Welds

    SciTech Connect

    Babu, S.S.; David, S.A.; Miller, M.K.; Vitek, J.M.

    1999-11-01

    Welding is important for economical reuse and reclamation of used and failed nickel-base superalloy blades, respectively [1]. Solidification and solid state decomposition of {gamma} (Face Centered Cubic, FCC) phase into {gamma}{prime} (L1{sub 2}-ordered) phase control the properties of these welds. In previous publications, the microstructure development in electron beam welds of PWA-1480 alloy [2] and laser beam welds of CMSX-4 alloy [3] were presented. These results showed that the weld cracking in these alloys were associated with low melting point eutectic at the dendrite boundaries [1,2]. The eutectic-{gamma}{prime} precipitation was reduced at rapid weld cooling rates and the partitioning between {gamma}-{gamma}{prime} phase was found to be far from equilibrium conditions [3,4]. This observation was related to diffusional growth of {gamma}{prime} precipitate into {gamma} phase. Subsequent to the above work, the precipitation characteristics of {gamma}{prime} phase from {gamma} phase were evaluated during continuous cooling conditions [5]. The results show that the number density of {gamma} precipitates increased with an increase in cooling rate. However, the details of this decomposition and also the fine-scale elemental partitioning characteristics between {gamma}-{gamma}{prime} were not investigated. In this paper, the precipitation characteristics of {gamma}{prime} from {gamma} during continuous cooling conditions were investigated with transmission electron microscopy, and atom probe field ion microscopy. In addition, thermodynamic and kinetic models were used to describe microstructure development in Ni-base superalloy welds.

  12. Effect of Crystal Orientation on Fatigue Failure of Single Crystal Nickel Base Turbine Blade Superalloys

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.; Swanson, Gregory R.

    2000-01-01

    High Cycle Fatigue (HCF) induced failures in aircraft gas-turbine engines is a pervasive problem affecting a wide range of components and materials. HCF is currently the primary cause of component failures in gas turbine aircraft engines. Turbine blades in high performance aircraft and rocket engines are increasingly being made of single crystal nickel superalloys. Single-crystal Nickel-base superalloys were developed to provide superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over polycrystalline alloys previously used in the production of turbine blades and vanes. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493 and PWA 1484. These alloys play an important role in commercial, military and space propulsion systems. PWA1493, identical to PWA1480, but with tighter chemical constituent control, is used in the NASA SSME (Space Shuttle Main Engine) alternate turbopump, a liquid hydrogen fueled rocket engine. Objectives for this paper are motivated by the need for developing failure criteria and fatigue life evaluation procedures for high temperature single crystal components, using available fatigue data and finite element modeling of turbine blades. Using the FE (finite element) stress analysis results and the fatigue life relations developed, the effect of variation of primary and secondary crystal orientations on life is determined, at critical blade locations. The most advantageous crystal orientation for a given blade design is determined. Results presented demonstrates that control of secondary and primary crystallographic orientation has the potential to optimize blade design by increasing its resistance to fatigue crack growth without adding additional weight or cost.

  13. Extraordinary plastic behaviour of the γ‧ precipitate in a directionally solidified nickel-based superalloy

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Ma, Lifeng; Yang, Gongxian; Song, Xiaolong

    2016-01-01

    The deformation behaviour of the γ‧ precipitate in a directionally solidified nickel-based superalloy is investigated using microscopic observations after tensile testing at room temperature. It is found that coarse γ‧ precipitates (604 nm) are sheared by strongly coupled dislocations, and some γ‧ precipitates are elongated to approximately 3-6 times of their original lengths. It reveals that, at room temperature, the γ‧ precipitate within the experimental superalloy has a significant plastic deformation capacity in comparison with Ni3Al bulk alloys. Based on the experimental observations, the extraordinary plastic behaviour of the γ‧ precipitate is analysed.

  14. The effect of hydrogen on the deformation behavior of a single crystal nickel-base superalloy

    NASA Technical Reports Server (NTRS)

    Walston, W. S.; Thompson, A. W.; Bernstein, I. M.

    1989-01-01

    The effect of hydrogen on the tensile deformation behavior of PWA 1480 is presented. Tensile tests were interrupted at different plastic strain levels to observe the development of the dislocation structure. Transmission electron microscopy (TEM) foils were cut perpendicular to the tensile axis to allow the deformation of both phases to be simultaneously observed as well as parallel to zone axes (III) to show the superdislocations on their slip planes. Similar to other nickel-base superalloys, hydrogen was detrimental to the room temperature tensile properties of PWA 1480. There was little effect on strength, however the material was severely embrittled. Even without hydrogen, the elongation-to-failure was only approximately 3 percent. The tensile fracture surface was made up primarily of ductile voids with regions of cleavage fracture. These cleavage facets are the eutectic (gamma') in the microstructure. It was shown by quantitative fractography that hydrogen embrittles the eutectic (gamma') and causes the crack path to seek out and fracture through the eutectic (gamma'). There was two to three times the amount of cleavage on the fracture surface of the hydrogen-charged samples than on the surface of the uncharged samples. The effect of hydrogen can also be seen in the dislocation structure. There is a marked tendency for dislocation trapping in the gamma matrix with and without hydrogen at all plastic strain levels. Without hydrogen there is a high dislocation density in the gamma matrix leading to strain exhaustion in this region and failure through the matrix. The dislocation structure at failure with hydrogen is slightly different. The TEM foils cut parallel to zone axes (III) showed dislocations wrapping around gamma precipitates. Zone axes (001) foils show that there is a lower dislocation density in the gamma matrix which can be linked to the effects of hydrogen on the fracture behavior. The primary activity in the gamma precipitates is in the form of

  15. Influence of composition on microstructural parameters of single crystal nickel-base superalloys

    SciTech Connect

    MacKay, R.A.; Gabb, T.P.; Garg, A.; Rogers, R.B.; Nathal, M.V.

    2012-08-15

    Fourteen nickel-base superalloy single crystals containing a range of chromium (Cr), cobalt (Co), molybdenum (Mo), and rhenium (Re) levels, and fixed amounts of aluminum (Al) and tantalum (Ta), were examined to determine the effect of bulk composition on basic microstructural parameters, including {gamma} Prime solvus, {gamma} Prime volume fraction, topologically close-packed (TCP) phases, {gamma} and {gamma} Prime phase chemistries, and {gamma}-{gamma} Prime lattice mismatch. Regression models describing the influence of bulk alloy composition on each of the microstructural parameters were developed and compared to predictions by a commercially-available software tool that used computational thermodynamics. Co produced the largest change in {gamma} Prime solvus over the wide compositional range explored and Mo produced the biggest effect on the {gamma} lattice parameter over its range, although Re had a very potent influence on all microstructural parameters investigated. Changing the Cr, Co, Mo, and Re contents in the bulk alloy had an impact on their concentrations in the {gamma} matrix and to a smaller extent in the {gamma} Prime phase. The software tool under-predicted {gamma} Prime solvus temperatures and {gamma} Prime volume fractions, and over-predicted TCP phase volume fractions at 982 Degree-Sign C. However, the statistical regression models provided excellent estimations of the microstructural parameters and demonstrated the usefulness of such formulas. - Highlights: Black-Right-Pointing-Pointer Effects of Cr, Co, Mo, and Re on microstructure in new low density superalloys Black-Right-Pointing-Pointer Co produced a large change in {gamma} Prime solvus; Mo had a large effect on lattice mismatch. Black-Right-Pointing-Pointer Re exhibited very potent influence on all microstructural parameters was investigated. Black-Right-Pointing-Pointer {gamma} and {gamma} Prime phase chemistries both varied with temperature and alloy composition. Black

  16. The Effects of Stress Triaxiality, Temperature and Strain Rate on the Fracture Characteristics of a Nickel-Base Superalloy

    NASA Astrophysics Data System (ADS)

    Wang, Jianjun; Guo, Weiguo; Guo, Jin; Wang, Ziang; Lu, Shengli

    2016-05-01

    In this work, to study the effects of stress triaxiality, temperature, and strain rate on the fracture behaviors of a single-crystal Nickel-base superalloy, a series of experiments over a temperature range of 293 to 1373 K, strain rate range of 0.001 to 4000/s, and stress triaxiality range of -0.6 to 1.1 are conducted. Anomalous peak of stress is noticed in the yield stress versus temperature curves, and strain rate effect on the anomalous peak of yield stress is analyzed. The anomalous peak shifts to higher temperature as the strain rate increases. Then the effects of stress triaxiality, temperature, and strain rate on its fracture behaviors, including strain to fracture, path of crack propagation, and fracture surface, are observed and analyzed. A valley of the fracture strain is formed in the fracture strain versus temperature curve over the selected temperature range. The micrograph of fracture surface is largely dependent on the temperature, stress triaxiality, and strain rate. Finally, the original Johnson-Cook (J-C) fracture criterion cannot describe the effect of stress triaxiality and temperature on the fracture behaviors of single-crystal Nickel-base superalloy. A modified J-C fracture criterion is developed, which takes the anomalous stress triaxiality and temperature effects on the fracture behaviors of single-crystal Nickel-base superalloy into account.

  17. Modern fiber laser beam welding of the newly-designed precipitation-strengthened nickel-base superalloys

    NASA Astrophysics Data System (ADS)

    Naffakh Moosavy, Homam; Aboutalebi, Mohammad-Reza; Seyedein, Seyed Hossein; Goodarzi, Massoud; Khodabakhshi, Meisam; Mapelli, Carlo; Barella, Silvia

    2014-04-01

    In the present research, the modern fiber laser beam welding of newly-designed precipitation-strengthened nickel-base superalloys using various welding parameters in constant heat input has been investigated. Five nickel-base superalloys with various Ti and Nb contents were designed and produced by Vacuum Induction Melting furnace. The fiber laser beam welding operations were performed in constant heat input (100 J mm-2) and different welding powers (400 and 1000 W) and velocities (40 and 100 mm s-1) using 6-axis anthropomorphic robot. The macro- and micro-structural features, weld defects, chemical composition and mechanical property of 3.2 mm weldments were assessed utilizing optical and scanning electron microscopes equipped with EDS analysis and microhardness tester. The results showed that welding with higher powers can create higher penetration-to-width ratios. The porosity formation was increased when the welding powers and velocities were increased. None of the welds displayed hot solidification and liquation cracks in 400 and 1000 W welding powers, but liquation phenomenon was observed in all the heat-affected zones. With increasing the Nb content of the superalloys the liquation length was increased. The changing of the welding power and velocity did not alter the hardness property of the welds. The hardness of welds decreased when the Ti content declined in the composition of superalloys. Finally, the 400 and 1000 W fiber laser powers with velocity of 40 and 100 m ms-1 have been offered for hot crack-free welding of the thin sheet of newly-designed precipitation-strengthened nickel-base superalloys.

  18. Modelling of recovery controlled creep in nickel-base superalloy single crystals

    SciTech Connect

    Svoboda, J.; Lukas, P.

    1997-01-01

    A model of the kinetics of recovery controlled creep in {l_angle}001{r_angle} oriented nickel-base superalloy single crystals has been developed. Two basic deformation mechanisms have been considered, namely (1) deformation of {gamma} channels by slip in discrete slip systems connected with the generation of dislocations and their deposition at the {gamma}/{gamma}{prime} interfaces; and (2) dynamic recovery of the dislocation structure due to non-conservative motion (a combination of slip and climb) of dislocations along the {gamma}/{gamma}{prime} interfaces and their annihilation. The climb of dislocations is conditioned by the diffusive transport of vacancies generated and annihilated at the climbing dislocations. In the steady-state creep the rate of the slip deformation in all the {gamma} channels is in equilibrium with the recovery induced diffusional deformation. The model predicts realistic values of the steady-state creep rates and their dependence on the applied stress, as well as the strains corresponding to the end of the primary creep stage, dislocation densities at the {gamma}/{gamma}{prime} interfaces and resolved shear stresses both in the {gamma} channels and in the {gamma}{prime} particles.

  19. Creep lifetime prediction of oxide-dispersion-strengthened nickel-base superalloys: A micromechanically based approach

    NASA Astrophysics Data System (ADS)

    Heilmaier, M.; Reppich, B.

    1996-12-01

    The high-temperature creep behavior of the oxide-dispersion-strengthened (ODS) nickel-base superalloys MA 754 and MA 6000 has been investigated at temperatures up to 1273 K and lifetimes of approximately 4000 hours using monotonic creep tests at constant true stress σ, as well as true constant extension rate tests (CERTs) atdot \\varepsilon . The derivation of creep rupture-lifetime diagrams is usually performed with conventional engineering parametric methods, according to Sherby and Dorn or Larson and Miller. In contrast, an alternative method is presented that is based on a more microstructural approach. In order to describe creep, the effective stress model takes into account the hardening contribution σ p caused by the presence of second-phase particles, as well as the classical Taylor back-stress σ p caused by dislocations. The modeled strain rate-stress dependence can be transferred directly into creep-rupture stress-lifetime diagrams using a modified Monkman-Grant (MG) relationship, which adequately describes the interrelation betweendot \\varepsilon representing dislocation motion, and lifetime t f representing creep failure. The comparison with measured creep-rupture data proves the validity of the proposed micromechanical concept.

  20. Laser micro-hole drilling in thermal barrier coated nickel based superalloy

    NASA Astrophysics Data System (ADS)

    Gupta, Umashanker; Nath, A. K.; Bandyopadhyay, P. P.

    2016-09-01

    This investigation deals with laser drilling of micro holes in yttria stabilised zirconia coated nickel based superalloy using a power modulated fiber laser. The parameters taken into account are assist gas pressure, modulation frequency, pulse on time and hole inclination angle. These parameters affect the important geometrical characteristics of holes, e.g., hole diameter, hole wall smoothness, taper angle and recast layer thickness. It has been found that the assist gas pressure has a significant effect on hole entry and exit diameter, taper angle and hole wall smoothness. It has also been observed less number of pulses of higher energy produces a hole with smaller entry and exit diameter, smaller taper angle, smoother hole wall and a thin stretched recast layer (∼ 15μm). The minimum achieved hole entrance diameter, exit diameter and taper was 342 μm, 200 μm and 3.54° respectively. Off normal drilling produces a hole with elliptical entrance. The eccentricity of such holes increases with inclination angle. Thick recast layers are produced at high inclination angles.

  1. Fatigue crack propagation of nickel-base superalloys at 650 deg C

    NASA Technical Reports Server (NTRS)

    Gayda, J.; Gabb, T. P.; Miner, R. V.

    1988-01-01

    The 650 C fatigue crack propagation behavior of two nickel-base superalloys, Rene 95 and Waspaloy, is studied with particular emphasis placed on understanding the roles of creep, environment, and two key grain boundary alloying additions, boron and zirconium. Comparison of air and vacuum data shows the air environment to be detrimental over a wide range of frequencies for both alloys. More in-depth analysis on Rene 95 shows at lower frequencies, such as 0.02 Hz, failure in air occurs by intergranular, environmentally-assisted creep crack growth, while at higher frequencies, up to 5.0 Hz, environmental interaction are still evident but creep effects are minimized. The effect of B and Zr in Waspaloy is found to be important where environmental and/or creep interactions are presented. In those instances, removal of B and Zr dramatically increases crack growth and it is therefore plausible that effective dilution of these elements may explain a previously observed trend in which crack growth rates increase with decreasing grain size.

  2. Fatigue crack propagation of nickel-base superalloys at 650 deg C

    NASA Technical Reports Server (NTRS)

    Gayda, J.; Gabb, T. P.; Miner, R. V.

    1985-01-01

    The 650 C fatigue crack propagation behavior of two nickel-base superalloys, Rene 95 and Waspaloy, is studied with particular emphasis placed on understanding the roles of creep, environment, and two key grain boundary alloying additions, boron and zirconium. Comparison of air and vacuum data shows the air environment to be detrimental over a wide range of frequencies for both alloys. More in-depth analysis on Rene 95 shows at lower frequencies, such as 0.02 Hz, failure in air occurs by intergranular, environmentally-assisted creep crack growth, while at higher frequencies, up to 5.0 Hz, environmental interactions are still evident but creep effects are minimized. The effect of B and Zr in Waspaloy is found to be important where environmental and/or creep interactions are presented. In those instances, removal of B and Zr dramatically increases crack growth and it is therefore plausible that effective dilution of these elements may explain a previously observed trend in which crack growth rates increase with decreasing grain size.

  3. Studies on the hot corrosion of a nickel-base superalloy, Udimet 700

    NASA Technical Reports Server (NTRS)

    Misra, A. K.

    1984-01-01

    The hot corrosion of a nickel-base superalloy, Udimet 700, was studied in the temperature range of 884 to 965 C and with different amounts of Na2SO4. Two different modes of degradation were identified: (1) formation of Na2MoO4 - MoO3 melt and fluxing by this melt, and (2) formation of large interconnected sulfides. The dissolution of Cr2O3, TiO2 in the Na2SO4 melt does not play a significant role in the overall corrosion process. The conditions for the formation of massive interconnected sulfides were identified and a mechanism of degradation due to sulfide formation is described. The formation of Ns2MoO4 - MoO3 melt requires an induction period and various physiochemical processes during the induction period were identified. The factors affecting the length of the induction period were also examined. The melt penetration through the oxide appears to be the prime mode of degradation whether the degradation is due to the formation of sulfides or the formation of the Na2MoO4 - MoO3 melt.

  4. Imaging and characterization of fine gamma' precipitates in a commercial nickel-base superalloy.

    PubMed

    Sarosi, P M; Viswanathan, G B; Whitis, D; Mills, M J

    2005-04-01

    Empirical datasets of volume fractions and size distributions of small gamma' precipitates from "real" multi-component engineering nickel-based superalloys are vital to calibrate and validate the computer models which predict high sensitivities of mechanical properties to size and volume fraction of these fine gamma precipitates, and in order to accelerate microstructure and alloy development. Consequently, we investigated a number of imaging techniques available in a Tecnai F-20 FEG/TEM and selected the technique which best enabled rapid and extensive acquisition of these datasets using the engineering alloy, René 88'DT. The EFTEM technique was found to be the most appropriate method for imaging fine gamma' precipitates while further investigation showed that the Cr-M-edge, in comparison with other ionization-edges provided the best images based largely on contrast-to-noise ratio. Imaging of the Cr-M-edge elemental maps were further improved by investigating the effects of microscope parameters, imaging filter parameters and analysis of the experimental electron energy loss spectra obtained from this alloy. In addition, a novel technique to determine the volume fraction of the fine gamma' precipitates without the need to determine the absolute thickness of the TEM foil is proposed. PMID:15777602

  5. Effect of casting geometry on mechanical properties of two nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Johnston, J. R.; Dreshfield, R. L.; Collins, H. E.

    1976-01-01

    An investigation was performed to determine mechanical properties of two rhenium-free modifications of alloy TRW, and to evaluate the suitability of the alloy for use in a small integrally cast turbine rotor. The two alloys were initially developed using stress rupture properties of specimens machined from solid gas turbine blades. Properties in this investigation were determined from cast to size bars and bars cut from 3.8 by 7.6 by 17.8 cm blocks. Specimens machined from blocks had inferior tensile strength and always had markedly poorer rupture lives than cast to size bars. At 1,000 C the cast to size bars had shorter rupture lives than those machined from blades. Alloy R generally had better properties than alloy S in the conditions evaluated. The results show the importance of casting geometry on mechanical properties of nickel base superalloys and suggest that the geometry of a component can be simulated when developing alloys for that component.

  6. Imaging and characterization of fine gamma' precipitates in a commercial nickel-base superalloy.

    PubMed

    Sarosi, P M; Viswanathan, G B; Whitis, D; Mills, M J

    2005-04-01

    Empirical datasets of volume fractions and size distributions of small gamma' precipitates from "real" multi-component engineering nickel-based superalloys are vital to calibrate and validate the computer models which predict high sensitivities of mechanical properties to size and volume fraction of these fine gamma precipitates, and in order to accelerate microstructure and alloy development. Consequently, we investigated a number of imaging techniques available in a Tecnai F-20 FEG/TEM and selected the technique which best enabled rapid and extensive acquisition of these datasets using the engineering alloy, René 88'DT. The EFTEM technique was found to be the most appropriate method for imaging fine gamma' precipitates while further investigation showed that the Cr-M-edge, in comparison with other ionization-edges provided the best images based largely on contrast-to-noise ratio. Imaging of the Cr-M-edge elemental maps were further improved by investigating the effects of microscope parameters, imaging filter parameters and analysis of the experimental electron energy loss spectra obtained from this alloy. In addition, a novel technique to determine the volume fraction of the fine gamma' precipitates without the need to determine the absolute thickness of the TEM foil is proposed.

  7. Studies on the hot corrosion of a nickel-base superalloy, Udimet 700

    NASA Technical Reports Server (NTRS)

    Misra, A. K.

    1986-01-01

    The hot corrosion of a nickel-base superalloy, Udimet 700, was studied in the temperture range of 884 to 965 C and with different amounts of Na2SO4. Two different modes of degradation were identified: (1) formation of Na2MoO4-MoO3 melt and fluxing by this melt, and (2) formation of large interconnected sulfides. The dissolution of Cr2O3, TiO2 in the Na2SO4 melt does not play a significnt role in the overall corrosion process. The conditions for the formation of massive interconnected sulfides were identified and a mechanism of degradation due to sulfide formation is described. The formation of Na2MoO4-MoO3 melt requires an induction period and various physiochemical processes during the induction period were identified. The factors affecting the length of the induction period were also examined. The melt penetration through the oxide appears to be the prime mode of degradation whether the degradation is due to the formation of sulfides or the formation of the Na2MoO4-MoO3 melt.

  8. High-Temperature Oxidation Behavior of Two Nickel-Based Superalloys Produced by Metal Injection Molding for Aero Engine Applications

    NASA Astrophysics Data System (ADS)

    Albert, Benedikt; Völkl, Rainer; Glatzel, Uwe

    2014-09-01

    For different high-temperature applications like aero engines or turbochargers, metal injection molding (MIM) of superalloys is an interesting processing alternative. For operation at high temperatures, oxidation behavior of superalloys produced by MIM needs to match the standard of cast or forged material. The oxidation behavior of nickel-based superalloys Inconel 713 and MAR-M247 in the temperature interval from 1073 K to 1373 K (800 °C to 1100 °C) is investigated and compared to cast material. Weight gain is measured discontinuously at different oxidation temperatures and times. Analysis of oxidized samples is done via SEM and EDX-measurements. MIM samples exhibit homogeneous oxide layers with a thickness up to 4 µm. After processing by MIM, Inconel 713 exhibits lower weight gain and thinner oxide layers than MAR-M247.

  9. Experimental Design for Evaluation of Co-extruded Refractory Metal/Nickel Base Superalloy Joints

    SciTech Connect

    ME Petrichek

    2005-12-16

    a critical thickness (0.0005 in.). A diffusion barrier that exceeded this thickness would likely fail. The joint fabrication method must therefore mechanically bond the two materials causing little or no interdiffusion upon formation. Co-extrusion fits this description since it forms a mechanical joint between two materials by using heat and pressure. The two materials to be extruded are first assembled and sealed within a co-extrusion billet which is subsequently heated and then extruded through a die. For a production application, once the joint is formed, it is dejacketed to remove the outer canister. The remaining piece consists of two materials bonded together with a thin diffusion barrier. Therefore, the long-term stability of the joint is determined primarily by the kinetics of interdiffusion reaction between the two materials. An experimental design for co-extrusion of refractory metals and nickel-based superalloys was developed to evaluate this joining process and determine the long-term stability of the joints.

  10. Very high cycle fatigue behavior of nickel-based superalloy Rene 88 DT

    NASA Astrophysics Data System (ADS)

    Miao, Jiashi

    The fatigue behavior of the polycrystalline nickel-based superalloy Rene 88 DT has been investigated at 593°C up to the very high cycle fatigue regime using ultrasonic fatigue techniques. Conventional damage tolerant methods failed to predict the fatigue life nor the large fatigue life viability of two orders of magnitude observed in the very high cycle regime. Fatigue crack initiation rather than fatigue crack growth is the life determining process in this alloy in the very high cycle regime. At 593°C, all fatigue failures have subsurface origins. Most fatigue crack initiation sites consist of a large crystallographic facet or a cluster of several large crystallographic facets. By combining electron backscatter diffraction, metallographic serial sectioning and SEM-stereo-image-based quantitative fractographic analysis, critical microstructure features associated with subsurface crystallographic fatigue crack initiation were identified. Subsurface fatigue cracks formed by the localization of cyclic plastic deformation on {111} slip planes in the region close to and parallel to twin boundaries in favorably oriented large grains. The facet plane in the crack initiation grain is parallel to the slip plane with the highest resolved shear stresses. Analytical calculations show that twin boundary elastic incompatibility stresses contribute to the onset of cyclic plastic strain localization in the fatigue crack initiation grains. Favorably oriented neighbor grains also can assist with fatigue crack initiation and especially early small crack propagation. Environment may play an important role in the shift of fatigue crack initiation sites from surface to subsurface at elevated temperature. The fatigue behavior of Rene 88 DT was also investigated under fully reversed loading at room temperature using ultrasonic fatigue techniques. Cyclic plastic strain localization and microcrack formation on specimen surfaces were quantitatively studied by EBSD. All microcracks examined

  11. Platinum-modified diffusion aluminide coatings on nickel-base superalloys. Final report, June 1985-June 1988

    SciTech Connect

    Kim, G.M.; Meier, G.H.; Pettit, F.S.

    1993-03-01

    Conventional and platinum modified diffusion aluminide coatings on some state-of-the art single crystal and polycrystalline nickel-base superalloys have been compared in tests designed to establish conditions representative of those existing in gas turbines operating over a range of applications. Resistance of these coatings to oxidation, high temperature hot corrosion, and low temperature hot corrosion have been compared. Platinum has been found to significantly improve the resistance of diffusion aluminides to all of these forms of degradation but the improvement with regard to low temperature hot corrosion is not as great as in the case of the other two forms of attack. Substrate composition has been found to exert a very significant effect on the lives of coatings in the high temperature tests. In the case of high temperature oxidation, elements such as Hf are important in that they extend coating lives whereas for high temperature hot corrosion the type and concentration of refractory elements are significant factors affecting coating lives. A limited number of experiments have indicated intermittent hot corrosion exposures degrade the subsequent cyclic oxidation resistance of Pt-aluminide coatings.... Superalloys, Nickel-base superalloys, Oxidation resistance, Platinum coatings, Single crystals.

  12. Selective oxidation and internal nitridation during high-temperature exposure of single-crystalline nickel-base superalloys

    SciTech Connect

    Krupp, U.; Christ, H.J.

    2000-01-01

    The process of internal nitridation of the three commercial single-crystalline nickel-base superalloys CMSX-2, CMSX-6, and SRR99 has been studied in air and oxygen-free nitrogen atmospheres at 800 C to 1,100 C using thermogravimetric techniques supplemented by extensive microstructural examinations. Non-protective oxide formation, particularly cracking and spalling at edges or curved surfaces, enables nitrogen to penetrate into the alloy leading to the precipitation of stable Ti and Al nitrides. The high-temperature corrosion behavior of the superalloys studied is strongly affected by composition differences between dendritic and interdendritic areas due to segregation resulting in an inhomogeneous internal precipitation zone. Furthermore, the stability of the strengthening {radical} phase (N3i(Al, Ti, Ta)) in front of the growing internal-nitridation zone was observed to depend clearly on the alloy composition. Therefore, the near-surface area of the alloys can be weakened by {radical} depletion and by embrittlement resulting from internal-nitride precipitation. The results obtained on the nickel-base superalloys are discussed, taking into account the results of a computer-based simulation of internal-corrosion processes. Furthermore, results on Ni-base model alloys of the system Ni-Cr-Al-Ti provided information on the role of the alloy composition. It was found that a higher Cr concentration seems to increase the nitrogen solubility and diffusion in Ni-base alloys.

  13. Analysis of the Influence of Laser Welding on Fatigue Crack Growth Behavior in a Newly Developed Nickel-Base Superalloy

    NASA Astrophysics Data System (ADS)

    Buckson, R. A.; Ojo, O. A.

    2015-01-01

    The influence of laser welding on fatigue crack growth (FCG) behavior of a newly developed nickel-base superalloy, Haynes 282 was studied. Laser welding resulted in cracking in the heat affected zone (HAZ) of the alloy during welding and FCG test results show that this produces deleterious effect on the fatigue crack growth behavior of Haynes 282. However, two post weld heat treatments, including a new thermal treatment schedule developed in this work, are used to significantly improve the resistance of the Haynes 282 fatigue crack growth after laser welding. The effects of laser welding and thermal treatments are discussed in terms of HAZ cracking and heterogeneity of slip, respectively.

  14. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Precipitate Contribution to the Acoustic Nonlinearity in Nickel-Based Superalloy

    NASA Astrophysics Data System (ADS)

    Chung-seok, Kim; Cliff, Lissenden J.

    2009-08-01

    The influence of γ' precipitate on the acoustic nonlinearity is investigated for a nickel-based superalloy, which is subjected to creep deformation. During creep deformation, the cuboidal γ' precipitate is preferentially coarsened in a direction perpendicular to the applied stress axis. The length and shape factor of the γ' precipitate increase with creep time. The increase of relative acoustic nonlinearity with increasing fraction of creep life is discussed in relation to the rafting of γ' precipitate, which is closely related to the scattering and distortion of the acoustic wave.

  15. Effects of silicon on the oxidation, hot-corrosion, and mechanical behavior of two cast nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Miner, R. V., Jr.

    1977-01-01

    Cast specimens of nickel-base superalloys 713C and Mar-M200 with nominal additions of 0, 0.5, and 1 wt% Si were evaluated for oxidation and corrosion resistance, tensile and stress-rupture properties, microstructure, and phase relations. Results are compared with those of an earlier study of the effects of Si in B-1900. Si had similar effects on all three superalloys. It improves oxidation resistance but the improvement in 713C and Mar-M200 was considerably less than in B-1900. Hot-corrosion resistance is also improved somewhat. Si is, however, detrimental to mechanical properties, in particular, rupture strength and tensile ductility. Si has two obvious microstructural effects. It increases the amount of gamma-prime precipitated in eutectic nodules and promotes a Mo(Ni,Si)2 Laves phase in the alloys containing Mo. These microstructural effects do not appear responsible for the degradation of mechanical properties, however.

  16. Confidence bounds for the estimation of the volume phase fraction from a single image in a nickel base superalloy.

    PubMed

    Blanc, Rémi; Baylou, Pierre; Germain, Christian; Da Costa, Jean-Pierre

    2010-06-01

    We propose an image-based framework to evaluate the uncertainty in the estimation of the volume fraction of specific microstructures based on the observation of a single section. These microstructures consist of cubes organized on a cubic mesh, such as monocrystalline nickel base superalloys. The framework is twofold: a model-based stereological analysis allows relating two-dimensional image observations to three-dimensional microstructure features, and a spatial statistical analysis allows computing approximate confidence bounds while assessing the representativeness of the image. The reliability of the method is assessed on synthetic models. Volume fraction estimation variances and approximate confidence intervals are computed on real superalloy images in the context of material characterization. PMID:20350338

  17. Confidence bounds for the estimation of the volume phase fraction from a single image in a nickel base superalloy.

    PubMed

    Blanc, Rémi; Baylou, Pierre; Germain, Christian; Da Costa, Jean-Pierre

    2010-06-01

    We propose an image-based framework to evaluate the uncertainty in the estimation of the volume fraction of specific microstructures based on the observation of a single section. These microstructures consist of cubes organized on a cubic mesh, such as monocrystalline nickel base superalloys. The framework is twofold: a model-based stereological analysis allows relating two-dimensional image observations to three-dimensional microstructure features, and a spatial statistical analysis allows computing approximate confidence bounds while assessing the representativeness of the image. The reliability of the method is assessed on synthetic models. Volume fraction estimation variances and approximate confidence intervals are computed on real superalloy images in the context of material characterization.

  18. Hot corrosion resistance of high-velocity oxyfuel sprayed coatings on a nickel-base superalloy in molten salt environment

    NASA Astrophysics Data System (ADS)

    Sidhu, T. S.; Prakash, S.; Agrawal, R. D.

    2006-09-01

    No alloy is immune to hot corrosion attack indefinitely. Coatings can extend the lives of substrate materials used at higher temperatures in corrosive environments by forming protective oxides layers that are reasonably effective for long-term applications. This article is concerned with studying the performance of high-velocity oxyfuel (HVOF) sprayed NiCrBSi, Cr3C2-NiCr, Ni-20Cr, and Stellite-6 coatings on a nickel-base superalloy at 900 °C in the molten salt (Na2SO4-60% V2O5) environment under cyclic oxidation conditions. The thermogravimetric technique was used to establish kinetics of corrosion. Optical microscope, x-ray diffraction, scanning electron microscopy/electron dispersive analysis by x-ray (SEM/EDAX), and electron probe microanalysis (EPMA) techniques were used to characterize the as-sprayed coatings and corrosion products. The bare superalloy suffered somewhat accelerated corrosion in the given environmental conditions. whereas hot corrosion resistance of all the coated superalloys was found to be better. Among the coating studied, Ni-20Cr coated superalloy imparted maximum hot corrosion resistance, whereas Stellite-6 coated indicated minimum resistance. The hot corrosion resistance of all the coatings may be attributed to the formation of oxides and spinels of nickel, chromium, or cobalt.

  19. Competing fatigue mechanisms in Nickel-base superalloy Rene 88DT

    NASA Astrophysics Data System (ADS)

    Chang, Paul N.

    Nickel base superalloys exhibit superior high temperature mechanical properties required for aircraft engine components. It has been known that the processing of these alloys by the powder metallurgy route introduces inclusions inside the material. The presence of such inclusions often leads to competing failure modes in fatigue that is described by a step-wise or two distinct S-N curves involving both the surface and internally-initiated cracks, resulting in large uncertainties of fatigue life. A clear understanding of such behavior is yet to be established. The principal objective of this research is to examine the effect of inclusions on the extent of fatigue failure competition from surface and internal initiators at two different specimen test volumes. Experimental fatigue testing has been performed to explore how the presence of inclusions affects the competing fatigue failure modes. In addition, how the competing failure modes will behave with changes in the specimen size was also studied. Two groups of material each with two different specimen sizes were used in this study. It has been shown that the two crack initiation mechanisms occurred in the small unseeded Rene 88DT specimens tested at 650ºC over the stress range tested. Additionally, the fatigue lives were reduced with increase in specimen volume. All fatigue failures in seeded material occurred due to crack initiations from the seeded inclusions. In the fatigue life of seeded material, two competing and separate S-N curves were found in small test volume, whereas, in the large test volume, the regions were separated by a "step" in S-N curve. It has been found that the largest inclusion size observed in metallographic surfaces was smaller than the size determined from the fatigue failure origin. An analysis method based on extreme value statistics developed by Murakami was used to predict the largest size of inclusion in the test volume. The results of this study clearly show that competition for

  20. Creep-rupture in powder metallurgical nickel-base superalloys at intermediate temperatures

    NASA Astrophysics Data System (ADS)

    Law, C. C.; Blackburn, M. J.

    1980-03-01

    To gain insight into the factors which control the creep-rupture properties of powder metallurgical nickel-base superalloys at intermediate temperatures (650 to 775°C), a comparative study was conducted on the alloys AF115, modified MAR-M432 (B6) and modified IN100 (MERL76). Creep-rupture properties in these alloys were characterized in terms of the stress and temperature dependence of the secondary creep rate, ɛS, andrupture time, t R . Within the limited stress ranges used, the stress dependence of both ɛS and t R at 704°C can be represented by power laws ɛS and C n and t R = Mσ -p ; where C, M, n, and p are constants. The stress exponents n and p are approximately equal for both AF115 and B6 with values of 16 and 7, respectively. In the case of MERL76, n and p are different, with values of 15 and 5, respectively. The apparent activation energies, Q, are 700, 370 and 520 KJ mol-1 for AF115, B6 and MERL76, respectively. For these alloys, long creep-rupture lives are associated with large values of n and Q. The sig-nificant differences in n and Q values between AF115 and B6 were related to creep re-covery processes for which the lattice misfit between the gamma and the gamma prime was identified to be an important parameter. However, the unequal n and p values in MERL76 compared with those in AF115 and B6, were traced to differences in fracture mode. Failures in AF115 and B6 were initiated at carbide particles at grain boundaries. In contrast, fracture in MERL76 was initiated at grain boundary triple junctions. The rupture lives of AF115 and B6 can be modeled reasonably well by the growth of cavities during secondary creep and propagation of a surface-nucleated crack during the tertiary creep.

  1. Atom-probe tomography of nickel-based superalloys with green or ultraviolet lasers: a comparative study.

    PubMed

    Amouyal, Yaron; Seidman, David N

    2012-10-01

    Recent developments in the technology of laser-pulsed local-electrode atom-probe (LEAP) tomography include a picosecond ultraviolet (UV) laser system having a 355 nm wavelength and both external and in-vacuum optics. This approach ensures focusing of the laser beam to a smaller spot diameter than has heretofore been obtained using a green (532 nm wavelength) picosecond laser. We compare the mass spectra acquired, using either green or UV laser pulsing, from nickel-based superalloy specimens prepared either electrochemically or by lifting-out from bulk material using ion-beam milling in a dual-beam focused ion beam microscope. The utilization of picosecond UV laser pulsing yields improved mass spectra, which manifests itself in higher signal-to-noise ratios and mass-resolving power (m/Δm) in comparison to green laser pulsing. We employ LEAP tomography to investigate the formation of misoriented defects in nickel-based superalloys and demonstrate that UV laser pulsing yields better accuracy in compositional quantification than does green laser pulsing. Furthermore, we show that using a green laser the quality of mass spectra collected from specimens that were lifted-out by ion milling is usually poorer than for electrochemically-sharpened specimens. Employing UV laser pulsing yields, however, improved mass spectra in comparison to green laser pulsing even for ion-milled microtips. PMID:23046701

  2. Influence of cooling rate on the development of multiple generations of {gamma}' precipitates in a commercial nickel base superalloy

    SciTech Connect

    Singh, A.R.P.; Nag, S.; Hwang, J.Y.; Viswanathan, G.B.; Tiley, J.; Srinivasan, R.; Fraser, H.L.; Banerjee, R.

    2011-09-15

    The compositional and microstructural evolution of different generations of {gamma}' precipitates during the continuous cooling of a commercial nickel base superalloy, Rene88DT, has been characterized by three dimensional atom probe tomography coupled with energy-filtered transmission electron microscopy studies. After solutionizing in the single {gamma} phase field, continuous cooling at a very high rate results in a monomodal size distribution of {gamma}' precipitates with a high nucleation density and non-equilibrium compositions. In contrast, a relatively slower cooling rate ({approx} 24 deg. C/min) results in a multi-modal size distribution of {gamma}' precipitates with the larger first generation primary precipitates exhibiting close to equilibrium composition, along with the smaller scale secondary {gamma}' precipitates, exhibiting non-equilibrium composition (excess of Co and Cr, depleted in Al and Ti). The composition of the {gamma} matrix near these precipitates also exhibits similar trends with the composition being closer to equilibrium near the primary precipitates as compared to the secondary precipitates. - Highlights: {yields} Effect of cooling rate on the precipitation of {gamma}' particles in commercial nickel base superalloy. {yields} Couples EFTEM and 3DAP studies to determine the composition and morphology of {gamma}' precipitates. {yields} Determination of near and far field compositional variations within the gamma matrix leading to subsequent precipitation.

  3. Microstructure Evolution and Analysis of A [011] Orientation, Single-Crystal, Nickel-Based Superalloy During Tensile Creep

    NASA Astrophysics Data System (ADS)

    Tian, Sugui; Zhang, Shu; Li, Chenxi; Yu, Huichen; Su, Yong; Yu, Xingfu; Yu, Lili

    2012-10-01

    By means of the elastic-plastic finite-element method (FEM) for calculating the distribution features of the von Mises stress and strain energy density, the influences of the applied stress on the von Mises stress of the γ'/ γ phases and the rafting of the γ' phase for the [011] orientation, single-crystal, nickel-based superalloy are investigated. The results show that, after being fully heat treated, the microstructure of the [011] orientation, single-crystal, nickel-based superalloy consists of the cuboidal γ' phase embedded coherently in the γ matrix, and the cuboidal γ' phase on (100) plane is regularly arranged along a 45 deg angle relative to the [011] orientation. Compared with the matrix channel of [010] orientation, the bigger von Mises stress is produced within the [001] matrix channel when the tensile stress is applied along the [011] orientation. Under the action of the larger principal stress component, the bigger expanding lattice strain occurs on the (001) plane of the cuboidal γ' phase along the [010] direction, which may trap the Al, Ti atoms with a bigger atomic radius for promoting the directional growth of the γ' phase into the stripe-like rafted structure along the [001] orientation. The changes of the interatomic potential energy, misfit stress, and interfacial energy during the tensile creep are thought to be the driving forces of promoting the elements' diffusion and directional growth of the γ' phase.

  4. Atom-probe tomography of nickel-based superalloys with green or ultraviolet lasers: a comparative study.

    PubMed

    Amouyal, Yaron; Seidman, David N

    2012-10-01

    Recent developments in the technology of laser-pulsed local-electrode atom-probe (LEAP) tomography include a picosecond ultraviolet (UV) laser system having a 355 nm wavelength and both external and in-vacuum optics. This approach ensures focusing of the laser beam to a smaller spot diameter than has heretofore been obtained using a green (532 nm wavelength) picosecond laser. We compare the mass spectra acquired, using either green or UV laser pulsing, from nickel-based superalloy specimens prepared either electrochemically or by lifting-out from bulk material using ion-beam milling in a dual-beam focused ion beam microscope. The utilization of picosecond UV laser pulsing yields improved mass spectra, which manifests itself in higher signal-to-noise ratios and mass-resolving power (m/Δm) in comparison to green laser pulsing. We employ LEAP tomography to investigate the formation of misoriented defects in nickel-based superalloys and demonstrate that UV laser pulsing yields better accuracy in compositional quantification than does green laser pulsing. Furthermore, we show that using a green laser the quality of mass spectra collected from specimens that were lifted-out by ion milling is usually poorer than for electrochemically-sharpened specimens. Employing UV laser pulsing yields, however, improved mass spectra in comparison to green laser pulsing even for ion-milled microtips.

  5. Microstructure-mechanical property relationships in transient liquid phase bonded nickel-based superalloys and iron-based ODS alloys

    NASA Astrophysics Data System (ADS)

    Aluru, Sreenivasa Charan Rajeev

    The research work presented here discusses the microstructure-mechanical property relationships in wide gap transient liquid phase (TLP) bonds, between the single crystal nickel-base superalloy CMSX-4 and two polycrystalline superalloys, IN 738 and IN 939, using wide-gap style composite interlayers. Fabrication of complicated geometries and successful repair development of gas turbine engine components made of superalloys requires a high performance metallurgical joining technique and a complete understanding of microstructure-mechanical property relationships. A number of joining processes have been investigated, but all of them have significant disadvantages that limit their ability to produce sound joints. TLP bonding has proved to be a successful method and is the most preferred joining method for nickel-based superalloys, with microstructures and compositions of the joint similar to that of the bulk substrates resulting in mechanical properties close to that of the parent metal. The current joining process used two proprietary wide-gap style composite interlayers, Niflex-110 and Niflex-115, consisting of a nickel-based core with boron-rich surfaces, and a conventional rapidly solidified metallic glass foil interlayer BNi-3 was chosen for comparison. When composite interlayers were employed, competition between wetting of the faying surfaces and formation of the eutectic along the grain boundaries was observed to lead to non-bonded regions at the faying surfaces, unless a boron-rich interlayer was employed. Composite interlayers resulted in the suppression of bondline boride formation. With the exception of this competition, adequate wetting of the substrates occurred for all interlayers. Two factors dominated the room temperature mechanical properties of the wide-gap bonds. The first was the extent of gamma-prime formation at the bondline. Results from shear testing and fractography of the bonds indicated ductile shear failure at the bondline. This was due to

  6. Computational Thermodynamic Study to Predict Complex Phase Equilibria in the Nickel-Base Superalloy Rene N6

    NASA Technical Reports Server (NTRS)

    Copland, Evan H.; Jacobson, Nathan S.; Ritzert, Frank J.

    2001-01-01

    A previous study by Ritzert et al. on the formation and prediction of topologically closed packed (TCP) phases in the nickel-base superalloy Rene' N6 is re-examined with computational thermodynamics. The experimental data on phase distribution in forty-four alloys with a composition within the patent limits of the nickel-base superalloy Rene' N6 provide a good basis for comparison to and validation of a commercial nickel superalloy database used with ThermoCalc. Volume fraction of the phases and partitioning of the elements are determined for the forty-four alloys in this dataset. The baseline heat treatment of 400 h at 1366 K was used. This composition set is particularly interesting since small composition differences lead to dramatic changes in phase composition. In general the calculated values follow the experimental trends. However, the calculations indicated no TCP phase formation when the experimental measurements gave a volume percent of TCP phase less than 2 percent. When TCP phases were predicted, the calculations under-predict the volume percent of TCP phases by a factor of 2 to 8. The calculated compositions of the gamma and gamma' phases show fair agreement with the measurements. However, the calculated compositions of the P Phase do not agree with those measured. This may be due to inaccuracies in the model parameters for P phase and/or issues with the microprobe analyses of these phases. In addition, phase fraction diagrams and sigma and P phase solvus temperatures are calculated for each of the alloys. These calculations indicate that P phase is the primary TCP phase formed for the alloys considered here at 1366 K. Finally, a series of isopleths are calculated for each of the seven alloying elements. These show the effect of each alloying element on creating TCP phases.

  7. Effect of microstructure on high-temperature mechanical behavior of nickel-base superalloys for turbine disc applications

    NASA Astrophysics Data System (ADS)

    Sharpe, Heather Joan

    2007-05-01

    Engineers constantly seek advancements in the performance of aircraft and power generation engines, including, lower costs and emissions, and improved fuel efficiency. Nickel-base superalloys are the material of choice for turbine discs, which experience some of the highest temperatures and stresses in the engine. Engine performance is proportional to operating temperatures. Consequently, the high-temperature capabilities of disc materials limit the performance of gas-turbine engines. Therefore, any improvements to engine performance necessitate improved alloy performance. In order to take advantage of improvements in high-temperature capabilities through tailoring of alloy microstructure, the overall objectives of this work were to establish relationships between alloy processing and microstructure, and between microstructure and mechanical properties. In addition, the projected aimed to demonstrate the applicability of neural network modeling to the field of Ni-base disc alloy development and behavior. The first phase of this work addressed the issue of how microstructure varies with heat treatment and by what mechanisms these structures are formed. Further it considered how superalloy composition could account for microstructural variations from the same heat treatment. To study this, four next-generation Ni-base disc alloys were subjected to various controlled heat-treatments and the resulting microstructures were then quantified. These quantitative results were correlated to chemistry and processing, including solution temperature, cooling rate, and intermediate hold temperature. A complex interaction of processing steps and chemistry was found to contribute to all features measured; grain size, precipitate distribution, grain boundary serrations. Solution temperature, above a certain threshold, and cooling rate controlled grain size, while cooling rate and intermediate hold temperature controlled precipitate formation and grain boundary serrations. Diffusion

  8. The effect of temperature on the deformation structure of single crystal nickel based superalloys

    NASA Technical Reports Server (NTRS)

    Dollar, M.; Bernstein, I. M.

    1988-01-01

    Results for the temperature dependence of the yield and flow stress were obtained for the superalloys PWA 1480 and CMSX-2. An extended Copley-Kear (1967) model is used to predict flow stresses from the dislocation densities measured at different strains and temperatures. Differences found between the two superalloys include the development of their dislocation structure, their ductility, and their work hardening characteristics.

  9. Effect of orientations on in situ tensile deformation and fracture behaviours of nickel-base single-crystal superalloys

    NASA Astrophysics Data System (ADS)

    Li, P.; Zhou, B. M.; Zhou, Y. Z.; Li, J. G.; Jin, T.; Sun, X. F.; Zhang, Z. F.

    2014-07-01

    After systematically investigating in situ tensile deformation and fracture behaviours of nickel-base single-crystal superalloys with four different orientations, their slip and fracture modes in relation to the orientations are obtained and shown as follows. In [0 0 1] oriented specimen, four slip systems were activated and the crack initiated along the interactive location between the third slip bands (SBs) and deformation bands in priority. The crack propagation involves all three crack opening types of I, II and III. [0 1 1] oriented specimens exhibited obvious low strain hardening rate and high ductility, which can be attributed to the balance between the softening caused by the propagation of SBs and the latent hardening caused by the propagation of deformation bands. Except for ? case, the critical resolved shear stress (CRSS) of the other oriented superalloys at room temperature is approximate, which is due to non-Schmid behaviour in superalloys. Lall-Chin-Pope model is used to explain the orientation dependence of CRSS. Furthermore, the fracture modes of different oriented specimens depend on the intensity of intrusion and extrusion and the degree of match between normal stress and shear stress. The shear stress is beneficial to the crack initiation and the normal stress contributes to the crack propagation.

  10. Effect of Heat Treatment on Chemical Segregation in CMSX-4 Nickel-Base Superalloy

    NASA Astrophysics Data System (ADS)

    Szczotok, A.; Chmiela, B.

    2014-08-01

    Superalloys display a strong tendency toward chemical segregation during solidification. Therefore, it is of great importance to develop appropriate techniques for the melting and casting of superalloys. Elements partitioning between the γ and γ' phases in single crystal superalloys have been investigated by several authors using electron probe microanalysis (Hemmersmeier and Feller-Kniepmeier Mater Sci Eng A 248:87-97, 1998; Kearsey et al. Intermetallics 12:903-910, 2004; Kearsey et al. Superalloys 2004, pp 801-810, 2004; D'Souza et al. Mater Sci Eng A 490:258-265, 2008). We examined the effect of the particular stages of standard heat treatment (solution treatment and ageing) applied to CMSX-4 single crystal superalloy on chemical segregation that occurs between dendrites and interdendritic areas. Dendritic structures were observed using a scanning electron microscope. Analyses of the chemical composition were performed using energy dispersive x-ray spectroscopy. The obtained qualitative and quantitative results for the concentrations of elements enabled us to confirm the dendritic segregation in as-cast CMSX-4 superalloy. The concentrations of some refractory elements (tungsten, rhenium) were much greater in dendrites than in interdendritic areas. However, these differences in chemical composition gradually decreased during heat treatment. The results obtained in this study warrant further examination of the diffusion processes of elements during heat treatment of the investigated superalloy, and of the kinetics of diffusion.

  11. Stereological characterization of the {gamma}' particles in a nickel base superalloy: Comparison between transmission electron microscopy and atomic force microscopy techniques

    SciTech Connect

    Risbet, M. Feaugas, X.; Guillemer-Neel, C.; Clavel, M.

    2008-09-15

    Critical comparison of transmission electron microscopy and atomic force microscopy techniques was provided concerning size measurements of {gamma}' precipitates in a nickel-base superalloy. The divergence between results is explained in terms of the resolution limit for atomic force microscopy, linked both to the tip dimension and the diameter of the investigated particles.

  12. Evidence of multimicrometric coherent γ' precipitates in a hot-forged γ-γ' nickel-based superalloy.

    PubMed

    Charpagne, M-A; Vennéguès, P; Billot, T; Franchet, J-M; Bozzolo, N

    2016-07-01

    This paper demonstrates the existence of large γ' precipitates (several micrometres in diameter) that are coherent with their surrounding matrix grain in a commercial γ-γ' nickel-based superalloy. The use of combined energy dispersive X-ray spectrometry and electron backscattered diffraction (EBSD) analyses allowed for revealing that surprising feature, which was then confirmed by transmission electron microscopy (TEM). Coherency for such large second-phase particles is supported by a very low crystal lattice misfit between the two phases, which was confirmed thanks to X-ray diffractograms and TEM selected area electron diffraction patterns. Dynamic recrystallization of polycrystalline γ-γ' nickel-based superalloys has been extensively studied in terms of mechanisms and kinetics. As in many materials with low stacking fault energy, under forging conditions, the main softening mechanism is discontinuous dynamic recrystallization. This mechanism occurs with preferential nucleation on the grain boundaries of the deformed matrix. The latter is then being consumed by the growth of the newly formed grains of low energy and by nucleation that keeps generating new grains. In the case of sub-solvus forging, large γ' particles usually pin the migrating boundaries and thus limit grain growth to a size which is determined by the distribution of second-phase particles, in good agreement with the Smith-Zener model. Under particular circumstances, the driving force associated with the difference in stored energy between the growing grains and the matrix can be large enough that the pinning forces can be overcome, and some grains can then reach much larger grain sizes. In the latter exceptional case, some intragranular primary γ' particles can be observed, although they are almost exclusively located on grain boundaries and triple junctions otherwise. In both cases, primary precipitates have no special orientation relationship with the surrounding matrix grain(s). This

  13. Evidence of multimicrometric coherent γ' precipitates in a hot-forged γ-γ' nickel-based superalloy.

    PubMed

    Charpagne, M-A; Vennéguès, P; Billot, T; Franchet, J-M; Bozzolo, N

    2016-07-01

    This paper demonstrates the existence of large γ' precipitates (several micrometres in diameter) that are coherent with their surrounding matrix grain in a commercial γ-γ' nickel-based superalloy. The use of combined energy dispersive X-ray spectrometry and electron backscattered diffraction (EBSD) analyses allowed for revealing that surprising feature, which was then confirmed by transmission electron microscopy (TEM). Coherency for such large second-phase particles is supported by a very low crystal lattice misfit between the two phases, which was confirmed thanks to X-ray diffractograms and TEM selected area electron diffraction patterns. Dynamic recrystallization of polycrystalline γ-γ' nickel-based superalloys has been extensively studied in terms of mechanisms and kinetics. As in many materials with low stacking fault energy, under forging conditions, the main softening mechanism is discontinuous dynamic recrystallization. This mechanism occurs with preferential nucleation on the grain boundaries of the deformed matrix. The latter is then being consumed by the growth of the newly formed grains of low energy and by nucleation that keeps generating new grains. In the case of sub-solvus forging, large γ' particles usually pin the migrating boundaries and thus limit grain growth to a size which is determined by the distribution of second-phase particles, in good agreement with the Smith-Zener model. Under particular circumstances, the driving force associated with the difference in stored energy between the growing grains and the matrix can be large enough that the pinning forces can be overcome, and some grains can then reach much larger grain sizes. In the latter exceptional case, some intragranular primary γ' particles can be observed, although they are almost exclusively located on grain boundaries and triple junctions otherwise. In both cases, primary precipitates have no special orientation relationship with the surrounding matrix grain(s). This

  14. Effect of Crystal Orientation on Fatigue Failure of Single Crystal Nickel Base Turbine Blade Superalloys

    NASA Technical Reports Server (NTRS)

    Arakere, N. K.; Swanson, G.

    2002-01-01

    High cycle fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Single crystal nickel turbine blades are being utilized in rocket engine turbopumps and jet engines throughout industry because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493, PWA 1484, RENE' N-5 and CMSX-4. These alloys play an important role in commercial, military and space propulsion systems. Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. The failure modes of single crystal turbine blades are complicated to predict due to the material orthotropy and variations in crystal orientations. Fatigue life estimation of single crystal turbine blades represents an important aspect of durability assessment. It is therefore of practical interest to develop effective fatigue failure criteria for single crystal nickel alloys and to investigate the effects of variation of primary and secondary crystal orientation on fatigue life. A fatigue failure criterion based on the maximum shear stress amplitude /Delta(sub tau)(sub max))] on the 24 octahedral and 6 cube slip systems, is presented for single crystal nickel superalloys (FCC crystal). This criterion reduces the scatter in uniaxial LCF test data considerably for PWA 1493 at 1200 F in air. Additionally, single crystal turbine blades used in the alternate advanced high-pressure fuel turbopump (AHPFTP/AT) are modeled using a large-scale three-dimensional finite element model. This finite element model is capable of accounting for material orthotrophy and variation in primary and secondary crystal orientation. Effects of variation in crystal orientation on blade stress response are studied based on 297

  15. Hot corrosion studies of four nickel-base superalloys: B-1900, NASA-TRW VIA, 713C and IN738

    NASA Technical Reports Server (NTRS)

    Fryburg, G. C.; Kohl, F. J.; Stearns, C. A.

    1976-01-01

    The susceptibility to hot corrosion of four nickel base superalloys has been studied at 900 deg and 1000 deg C in one atmosphere of slowly flowing oxygen. Hot corrosion was induced by coating the samples with known doses of NaSO4 and oxidizing the coated samples isothermally on a sensitive microbalance. In general, the order of susceptibility found was: B-1900 is greater than 713C is greater than NASA-TRW VIA and is greater than IN738. This order corresponds to the order of decreasing molybdenum content of the alloys. Chemical evidence for B-1900 indicates that hot corrosion is instigated by acid fluxing of the protective Al2O3 coating by MoO3.

  16. Hot corrosion studies of four nickel-base superalloys - B-1900, NASA-TRW VIA, 713C and IN738

    NASA Technical Reports Server (NTRS)

    Fryburg, G. C.; Kohl, F. J.; Stearns, C. A.

    1976-01-01

    The susceptibility to hot corrosion of four nickel-base superalloys has been studied at 900 and 1000 C in one atmosphere of slowly flowing oxygen. Hot corrosion was induced by coating the samples with known doses of Na2SO4 and oxidizing the coated samples isothermally on a sensitive microbalance. In order of decending susceptibility to hot corrosion, these alloys were ranked: B-1900, 713C, NASA-TRW VIA, IN738. This order corresponds to the order of decreasing molybdenum content of the alloys. Chemical evidence for B-1900 indicates that hot corrosion is instigated by acid fluxing of the protective Al2O3 coating by MoO3.

  17. Fatigue Crack Growth Behavior of Nickel-base Superalloy Haynes 282 at 550-750 °C

    NASA Astrophysics Data System (ADS)

    Rozman, K. A.; Kruzic, J. J.; Hawk, J. A.

    2015-08-01

    The fatigue crack growth rates for nickel-based superalloy Haynes 282 were measured at temperatures of 550, 650, and 750 °C using compact tension specimens with a load ratio of 0.1 and cyclic loading frequencies of 25 Hz and 0.25 Hz. Increasing the temperature from 550 to 750 °C caused the fatigue crack growth rates to increase from ~20 to 60% depending upon the applied stress intensity level. The effect of reducing the applied loading frequency increased the fatigue crack growth rates from ~20 to 70%, also depending upon the applied stress intensity range. The crack path was observed to be transgranular for the temperatures and frequencies used during fatigue crack growth rate testing. At 750 °C, there were some indications of limited intergranular cracking excursions at both loading frequencies; however, the extent of intergranular crack growth was limited and the cause is not understood at this time.

  18. Influence of cubic boron nitride grinding on the fatigue strengths of carbon steels and a nickel-base superalloy

    SciTech Connect

    Kawagoishi, N.; Chen, Q.; Kondo, E.; Goto, M.; Nisitani, H.

    1999-04-01

    The influence of cubic boron nitride (CBN) grinding on fatigue strength was investigated on an annealed carbon steel, a quenched and tempered carbon steel at room temperature, and a nickel-base superalloy, Inconel 718, at room temperature and 500 C. The results were discussed from several viewpoints, including surface roughness, residual stress, and work hardening or softening due to CBN grinding. The fatigue strength increased upon CBN grinding at room temperature, primarily because of the generation of compressive residual stress in the surface region. However, in the case of Inconel 718, this marked increase in the fatigue strength tended to disappear at the elevated temperature due to the release of compressive residual stress and the decrease of crack growth resistance at an elevated temperature.

  19. Fracture of single crystals of the nickel-base superalloy PWA 1480E in hydrogen at 22 C

    NASA Technical Reports Server (NTRS)

    Chen, P. S.; Wilcox, R. C.

    1991-01-01

    The present study investigates the hydrogen-induced fracture behavior of notched single crystals of the PWA 1480E nickel-based superalloy. Notched single crystals with seven different crystal orientations were tensile tested at 22 C in a hydrogen atmosphere at 34 MPa. Hydrogen-enhanced cleavage along 100-line planes in the notched region was found to be due to cracking along the gamma/gamma-prime interfaces. Cleavage on 111-line-type planes was observed only outside the notch region. The occurrence of 100- and 111-line-types of cleavage was independent of the single-crystal orientation. Outside the notch region, the fracture surfaces of specimens tested in hydrogen appeared very similar to those tested in helium. Differences in the fracture surfaces were located primarily near the notch region.

  20. Effect of crystallographic orientation on subcritical grain boundary cracking in a conventionally cast polycrystalline nickel-based superalloy.

    PubMed

    Swaminathan, Kameshwaran; Blendell, John E; Trumble, Kevin P

    2013-08-01

    The role of grain orientation and grain boundary misorientation on the formation of subcritical grain boundary cracks in creep of a conventionally cast nickel-based superalloy has been studied. The crystallographic orientations of the grains adjacent to grain boundaries normal to the tensile axis were measured using electron backscattered diffraction. The difference in the Schmid factor for the {111} <112> slip system between the grains was compared to the occurrence of grain boundary cracking. In addition, the difference in the amount of potential primary creep was calculated. The cracked grain boundaries were found to have a larger difference in Schmid factor, as well as a larger difference in potential primary creep, compared with uncracked grain boundaries. PMID:23718929

  1. High temperature low-cycle fatigue mechanisms in single crystals of nickel-based superalloy Mar-M 200

    NASA Technical Reports Server (NTRS)

    Milligan, W. W.; Jayaraman, N.

    1984-01-01

    Twenty three high temperature low-cycle fatigue tests were conducted on single crystals of the nickel-based superalloy Mar-M 200. Tests were conducted at 760 and 870 C. SEM fractography and transmission electron microscopy were used to determine mechanisms responsible for the observed orientation dependent fatigue behavior. It has been concluded that the plastic characteristics of the alloy lead to orientation-dependent strain hardening and fatigue lives at 760 C. At 870 C, the elastic characteristics of the alloy dominated the behavior, even though the plastic strain ranges were about the same as they were at 760 C. This led to orientation-dependent fatigue lives, but the trends were not the same as they were at 760 C.

  2. Influence of an aluminide coating on the TMF life of a single crystal nickel-base superalloy

    SciTech Connect

    Affeldt, E.E.

    1999-10-01

    TMF tests were conducted with bare and aluminide coated single crystal nickel-based superalloy specimens. Temperature cycling was between 400 C and 1,100 C with a phase shift (135 deg) that is typical for damaged locations on turbine blades. Stress response is characterized by a constant range and the formation of a tensile mean stress as a result of relaxation in the high temperature part of the cycle which is in compression. Bare specimens showed crack initiation from typical oxide hillocks. Coated specimens showed life reduction with respect to the bare ones caused by brittle cracking of the coating in the low temperature part of the cycle. Isothermal bending tests of coated specimens confirmed the low ductility of the coating at temperatures below 600 C but quantitative correlation with the TMF test results failed.

  3. Creep data analyses of a columnar-grained nickel-base superalloy by conventional and {beta}-envelope methods

    SciTech Connect

    Krishna, M.S.G.; Sriramamurthy, A.M.; Radhakrishnan, V.M.

    1998-08-01

    Creep-rupture properties of a columnar-grained nickel-base superalloy have been evaluated over a wide temperature range (1,033 to 1,311 K) and stress levels (80 to 850 MPa). Creep data analyses based on the conventional approach as well as on a new graphical method--the {beta}-envelope method--have been carried out for creep strain and life estimation purposes. The relation between minimum creep rate of the alloy with the applied stress obeys simple power law, whereas the rupture data of the alloy fits well to the Larson-Miller parameter. Also, the Monkman-Grant relation between the minimum creep rate and the rupture life produces a trend with some degree of scatter in the data. The latter relation in its generalized form by the {beta}-envelope method exhibited the best correlation with significantly reduced scatter in the data.

  4. Effect of crystallographic orientation on subcritical grain boundary cracking in a conventionally cast polycrystalline nickel-based superalloy.

    PubMed

    Swaminathan, Kameshwaran; Blendell, John E; Trumble, Kevin P

    2013-08-01

    The role of grain orientation and grain boundary misorientation on the formation of subcritical grain boundary cracks in creep of a conventionally cast nickel-based superalloy has been studied. The crystallographic orientations of the grains adjacent to grain boundaries normal to the tensile axis were measured using electron backscattered diffraction. The difference in the Schmid factor for the {111} <112> slip system between the grains was compared to the occurrence of grain boundary cracking. In addition, the difference in the amount of potential primary creep was calculated. The cracked grain boundaries were found to have a larger difference in Schmid factor, as well as a larger difference in potential primary creep, compared with uncracked grain boundaries.

  5. The influence of cobalt on the microstructure of the nickel-base superalloy MAR-M247

    NASA Technical Reports Server (NTRS)

    Nathal, M. V.; Maier, R. D.; Ebert, L. J.

    1982-01-01

    Nickel was substituted for Co to produce 0, 5, and the standard 10% versions of MAR-M247, a cast nickel-base superalloy. The microstructures of the alloys were examined in as-cast, heat treated, aged, and stress-rupture tested conditions using a variety of metallographic techniques and differential thermal analysis. As cobalt concentration was reduced from 10 to 0 wt %, the gamma-prime weight fraction decreased from 59 to 41%; W and Ti concentrations in the gamma-prime phase increased from 5 to 8 and 2 to 3 at.%, respectively; the mean gamma-prime particle size increased from 0.6 to 0.8 micron; Cr and Al concentrations in the gamma matrix decreased from 17 to 13 and 15 to 12 at.%, respectively; and the weight fraction of carbides increased by approximately 1%.

  6. ON THE INFLUENCE OF COLD WORK ON RESISTIVITY VARIATIONS WITH THERMAL EXPOSURE IN IN-718 NICKEL-BASE SUPERALLOY

    SciTech Connect

    Madhi, Elhoucine; Nagy, Peter B.

    2010-02-22

    In nickel-base superalloys, irreversible electrical conductivity changes occur above a transition temperature where thermally-activated microstructural evolution initiates. The electrical conductivity first decreases above about 450 deg. C then increases above 600 deg. C. However, the presence of plastic deformation results in accelerated microstructure evolution at an earlier transition temperature. It was recently suggested that this well-known phenomenon might explain the notable conductivity difference between the peened near-surface part and the intact part at sufficiently large depth in surface-treated specimens. The influence of cold work on the electrical conductivity change with thermal exposure offers a probable answer to one of the main remaining questions in eddy current residual stress assessment, namely unusually fast and occasionally even non-monotonic decay of the apparent eddy current conductivity (AECC) change that was observed at temperatures as low as 400 deg. C. To validate this explanation, the present study investigates the influence of cold work on low-frequency Alternating Current Potential Drop (ACPD) resistivity variations with thermal exposure. In-situ resistivity monitoring was conducted throughout various heating cycles using the ACPD technique. IN-718 nickel-base superalloy specimens with different levels of cold work were exposed to gradually increasing peak temperatures from 400 deg. C to 800 deg. C. The results indicate that the initial irreversible rise in resistivity is approximately one order of magnitude higher and occurs at about 50 deg. C lower temperature in cold-worked samples of 30% plastic strain than in the intact material.

  7. Sulfidation Characteristics of an Advanced Superalloy and Comparison with Other Superalloys Intended for Gas Turbine Use

    NASA Astrophysics Data System (ADS)

    Gurrappa, I.; Yashwanth, I. V. S.; Burnell-Gray, J. S.

    2013-11-01

    Sulfidation may occur even in an overall oxidizing environment beneath a corrosion product which assumes the role of a diffusion barrier allowing sulfur species transport at a faster rate when compared with that of oxygen species. The current paper presents sulfidation characteristics of an advanced single-crystal nickel-based superalloy (ANS) and compares performance with IN 792 and CMSX-4 superalloys. The results showed that all the superalloys were highly vulnerable to sulfidation and their lives were significantly reduced. Among them, the ANS was more susceptible to sulfidation and its life was reduced considerably. This is attributed to the changed chemistry of the advanced alloy. The results for ANS are compared with its oxidation data and the difference in its behavior is discussed. A degradation mechanism, which represents the deterioration of ANS under sulfidation conditions, is proposed based on the results obtained from different techniques. Finally, the necessity of protective coatings for shielding against high temperature sulfidation for potential application in enhanced efficiency of gas turbine engines is emphasized.

  8. Phase-contrast x-ray imaging of microstructure and fatigue-crack propagation in single-crystal nickel-base superalloys

    NASA Astrophysics Data System (ADS)

    Husseini, Naji Sami

    Single-crystal nickel-base superalloys are ubiquitous in demanding turbine-blade applications, and they owe their remarkable resilience to their dendritic, hierarchical microstructure and complex composition. During normal operations, they endure rapid low-stress vibrations that may initiate fatigue cracks. This failure mode in the very high-cycle regime is poorly understood, in part due to inadequate testing and diagnostic equipment. Phase-contrast imaging with coherent synchrotron x rays, however, is an emergent technique ideally suited for dynamic processes such as crack initiation and propagation. A specially designed portable ultrasonic-fatigue apparatus, coupled with x-ray radiography, allows real-time, in situ imaging while simulating service conditions. Three contrast mechanisms - absorption, diffraction, and phase contrast - span the immense breadth of microstructural features in superalloys. Absorption contrast is sensitive to composition and crack displacements, and diffraction contrast illuminates dislocation aggregates and crystallographic misorientations. Phase contrast enhances electron-density gradients and is particularly useful for fatigue-crack studies, sensitive to internal crack tips and openings less than one micrometer. Superalloy samples were imaged without external stresses to study microstructure and mosaicity. Maps of rhenium and tungsten concentrations revealed strong segregation to the center of dendrites, as manifested by absorption contrast. Though nominally single crystals, dendrites were misoriented from the bulk by a few degrees, as revealed by diffraction contrast. For dynamic studies of cyclic fatigue, superalloys were mounted in the portable ultrasonic-fatigue apparatus, subjected to a mean tensile stress of ˜50-150 MPa, and cycled in tension to initiate and propagate fatigue cracks. Radiographs were recorded every thousand cycles over the multimillion-cycle lifetime to measure micron-scale crack growth. Crack

  9. Effects of processing and microstructure on the fatigue behaviour of the nickel-base superalloy Rene95

    NASA Technical Reports Server (NTRS)

    Miner, R. V.; Gayda, J.

    1984-01-01

    Forms of the nickel-base superalloy Rene95 produced by three processing methods were evaluated in tensile, low cycle fatigue and fatigue crack propagation tests at 540 and 650 C. Two powder-metallurgy (PM) forms, hot-isostatically-pressed and extruded-and-forged, and a conventionally cast-and-wrought form were all given the same heat treatment. The extruded-and-forged form showed superior fatigue life in low strain range tests though the two PM forms exhibited nearly identical mechanical behavior in all other respects. Further, this life difference could not be explained by significant differences in the types, sizes or shapes of the defects initiating failure. The cast-and-wrought Rene95, however, had lower strength, ductility and fatigue life, but higher fatigue crack propagation resistance because of a larger grain size. It did not exhibit the environmentally-assisted intergranular mode of propagation which occurs in PM Rene95 and other fine-grained superalloys at these test temperatures and frequencies.

  10. Effects of Solutioning on the Dissolution and Coarsening of γ' Precipitates in a Nickel-Based Superalloy

    NASA Astrophysics Data System (ADS)

    Wang, Xiaomeng; Zhou, Yu; Zhao, Zihua; Zhang, Zheng

    2015-04-01

    The dissolution and the coarsening of the γ' precipitates in a nickel-based superalloy GTD-111 solutionized under various solution heat treatment conditions were investigated. The γ' solvus temperature for the GTD-111 superalloy was about 1180.79 °C obtained by differential scanning calorimetry test. The dissolution and the coarsening of γ' in the dendrite core were simultaneously observed, but the γ' precipitates in the interdendritics only occurred to coarsen under the condition of 1125 °C/2 h. The γ' dissolution, including dendrite core and interdendritics, gradually played a dominant role in the competition between the dissolution and the coarsening of γ' during the solutioning with the increase of solution temperature and holding time, indicating that the elastic strain field of the alloy gradually reduced. The solution condition of 1225 °C/6 h or 1250 °C/2 h was the optimal solutioning schedule than the other schedules. For a lower solution temperature, the volume fraction of primary γ' precipitates can faster reach its equilibrium value which is larger than that for a higher solution temperature. With the increase of holding time, the γ' dissolution rate continuously decreased, and the dissolution activation energy of γ' gradually increased.

  11. Local x-ray diffraction analysis of the structure of dendrites in single-crystal nickel-base superalloys

    SciTech Connect

    Brueckner, U.; Epishin, A.; Link, T.

    1997-12-01

    The structure of the dendrites in the single-crystal nickel-base superalloys SC16, SRR99 and CMSX4 with different refractory element levels (Mo + Ta + W + Re) has been investigated by local X-ray diffraction. A special technique was used to improve the spatial resolution of the X-ray diffraction and to enable the precise control of the X-ray spot position within the dendritic structure. A significant change of the {gamma}/{gamma}{prime}-lattice misfit was found within the dendrite in the superalloys with higher refractory element levels SRR99 and CMSX4. The observed misfit change is based on the change of the {gamma}-lattice parameter due to segregation of W and Re. The intensity of the X-ray beam reflected from the dendrite periphery was found to be weaker than that from the dendrite centre because of the mosaicity. Therefore misfit measurements without knowledge of the X-ray spot position in the dendritic structure lead to values that correspond more to the dendrite core.

  12. Microstructure evolution and FEM analysis of a [111] oriented single crystal nickel-based superalloy during tensile creep

    NASA Astrophysics Data System (ADS)

    Tian, Sugui; Li, Qiuyang; Su, Yong; Yu, Huichen; Xie, Jun; Zhang, Shu

    2015-03-01

    By means of the elastic-plastic stress-strain finite element method (FEM), the distribution of the von Mises stress and strain energy density in the regions near the interfaces of the cuboidal γ/ γ' phases is calculated to investigate the rafted behaviors of γ' phase in a [111] oriented single crystal (SC) nickel-based superalloy. Results show that, after fully heat treated, the microstructure of the superalloy consists of the cuboidal γ' phase embedded coherently in the γ matrix and arranged regularly along the <100> orientation. And the parameters and misfits of γ'/ γ phases in the alloy increase with the temperature. After crept for 50 h, the γ' phase in alloy has transformed into the mesh-like rafted structure on (010) plane along [001] and [100] orientations. When the tensile stress is applied along [111] direction, the change of the strain energy on the planes of the cuboidal γ' phase results in the directional diffusion of the elements. Thereinto, compared with (010) plane, the bigger expanding strain occurs on (100) and (001) planes along the [010], [001] and [010], [100] directions, which may trap the Al and Ti atoms with bigger radius to promote the directional growth of γ' phase on (010) plane along [100] and [001] directions. This is thought to be the main reason for the γ' phase directionally growing into the mesh-like rafted structure on (010) plane.

  13. The influence of primary and secondary orientations on the elastic response of a nickel-base single-crystal superalloy

    NASA Technical Reports Server (NTRS)

    Abdul-Aziz, Ali; Kalluri, Sreeramesh; Mcgaw, Michael A.

    1993-01-01

    The influence of primary orientation on the elastic response of a (001)-oriented nickel-base single-crystal superalloy, PWA 1480, was investigated under mechanical, thermal, and combined thermal and mechanical loading conditions using finite element techniques. Elastic stress analyses were performed using the MARC finite element code on a square plate of PWA 1480 material. Primary orientation of the single crystal superalloy was varied in increments of 2 deg, from 0 to 10 deg, from the (001) direction. Two secondary orientations (0 and 45 deg) were considered, with respect to the global coordinate system, as the primary orientation angle was varied. The stresses developed within the single crystal plate were determined for each loading condition. In this paper, the influence of the angular offset between the primary crystal orientation and the loading direction on the elastic stress response of the PWA 1480 plate is presented for different loading conditions. The influence of primary orientation angle, when constrained between the bounds considered, was not found to be as significant as the influence of the secondary orientation angle, which is not typically controlled.

  14. Quantification of precipitates and their effects on the response of nickel-base superalloy to shot peening

    NASA Astrophysics Data System (ADS)

    Chandrasekar, R.; Lo, C. C. H.; Frishman, A. M.; Larson, B. F.; Nakagawa, N.

    2012-05-01

    This paper reports on a microstructural study of a nickel-base superalloy, Inconel 718, with a focus on quantifying precipitate density and their effects on conductivity variations. The study is motivated by eddy current (EC) characterization of residual stresses, where observed EC signals are attempted to correlate with stress profiles of shot peened superalloy surfaces. It has been observed that the correlation is less universal than anticipated, and in fact strongly influenced by the material hardness, or the aging conditions. For example, the soft sample surface exhibits significantly stronger EC signals than the fully hardened sample when both are shot peened at the same Almen intensity. Thus, the objective of the present study is to examine this complex material response against aging and shot peening treatments at the microstructure scale, by the use of techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM). We will describe preparations of a series of Inconel 718 samples that was aged and shot peened at various conditions, and present microstructural data obtained from SEM and TEM images such as precipitate densities, correlated with bulk properties such as the hardness and conductivity.

  15. Equilibrium partition ratios, densities, and transport phenomena in nickel-base superalloys

    NASA Astrophysics Data System (ADS)

    Sung, Pil Kyung

    To simulate transport phenomena, macrosegregation and segregation defects known as "freckles" during directional solidification of Ni-base superalloys, numerical modeling can be used; hence it is essential to have reasonably accurate values of the thermodynamic and transport properties for the alloys. In this research, therefore, the equilibrium partition ratios of the solutes in the Ni-Al-Ta-Cr quaternary system, as a model alloy, were measured, and the solid- and liquid-densities in Ni-base superalloys. were estimated. Also, the importance of these properties on the sensitivity of the results of numerical simulations was studied. The partition ratios apply to equilibria between melts and gamma-phase in the range of 1615 K to 1694 K, and it was found that the equilibrium partition ratio of Ta varies from approximately 0.6 at dilute Ta to 0.85 at 17 wt.% Ta. For the same range of Ta-contents, the partition ratios of Al and Cr vary much less and range from about 0.92 to 0.96. In addition to the partition ratios, the liquidus temperatures of the liquid in equilibrium with gamma in the Ni-Al-Ta-Cr system were estimated with a multidimensional regression analysis. To calculate the densities of solid Ni-base superalloys as functions of temperature and composition, lattice parameters at 20°C and coefficients of thermal expansion (CTEs) were estimated by combining available data. The CTEs calculated from the regressions result in densities that are within 0.5% error or less for seventeen alloys. To estimate the densities of liquid Ni-base superalloys, the densities and temperature coefficients of density of the liquid transition-metals, which are used as alloy elements in Ni-base superalloys, were applied to a simple correlation. By using this approach, the estimates of the liquid densities of five Ni-base superalloys agree with the measured values to +/-2.5%. Finally, the importance of using reasonably accurate estimates of the transport properties was illustrated by

  16. Deleterious Phase Formation in Next- Generation Nickel-Base Superalloys Predicted

    NASA Technical Reports Server (NTRS)

    Ritzert, Frank J.

    1999-01-01

    Nickel- (Ni-) base superalloy single crystals represent the state-of-the-art for turbine engine airfoil applications because they offer the best balance of properties under the high operating temperatures required for efficient engine operation. Current trends in alloy design take advantage of improved creep rupture strength with the addition of higher levels of refractory elements. In particular, the addition of significantly higher levels of rhenium in third-generation superalloys is key for both microstructural stability and creep rupture strength. Although refractories provide strength benefits, alloys tend to be unstable when their refractory content is high because of topologically close-packed (TCP) phases. The formation of these phases in sufficient amount is detrimental to the performance of these alloys because of their brittle nature and because they deplete the Nirich matrix of potent solid-solution strengthening elements.

  17. Precipitation of the δ-Ni3Nb phase in two nickel base superalloys

    NASA Astrophysics Data System (ADS)

    Sundararaman, M.; Mukhopadhyay, P.; Banerjee, S.

    1988-03-01

    The precipitation of the equilibrium δ-Ni3Nb phase has been studied in two niobium bearing nickel base superalloys—INCONEL 718 and INCONEL* 625—both of which are hardenable by the precipitation of the metastable γ″-Ni3Nb phase. The morphology and the distribution of precipitates have been examined and the crystallographic orientation relationship between the austenite and the δ phases has been determined. The nucleation of the δ phase at stacking faults within pre-existing δ" precipitates has been discussed.

  18. Determination of γ-γ' lattice misfit in a single-crystal nickel-based superalloy using convergent beam electron diffraction aided by finite element calculations.

    PubMed

    Brunetti, G; Settefrati, A; Hazotte, A; Denis, S; Fundenberger, J-J; Tidu, A; Bouzy, E

    2012-02-01

    In single-crystal nickel-based superalloys, the lattice mismatch associated with interface coherency between γ matrix and γ' precipitates has a strong influence on mechanical properties. The unconstrained lattice misfit in a single-crystal of the MC2 nickel-based superalloy is determined using convergent beam electron diffraction measurements and finite element calculations. The apparent lattice parameters of both constrained phases are obtained in thin foils, using a new multi-pattern approach, which allows for unambiguous determination of all the lattice parameters considering the real symmetry of the strained crystals. Finite element calculations are used to establish relations between the constrained and unconstrained lattice parameters, with the stress relaxation resulting from the thin foil geometry taken into account. PMID:22055767

  19. Determination of γ-γ' lattice misfit in a single-crystal nickel-based superalloy using convergent beam electron diffraction aided by finite element calculations.

    PubMed

    Brunetti, G; Settefrati, A; Hazotte, A; Denis, S; Fundenberger, J-J; Tidu, A; Bouzy, E

    2012-02-01

    In single-crystal nickel-based superalloys, the lattice mismatch associated with interface coherency between γ matrix and γ' precipitates has a strong influence on mechanical properties. The unconstrained lattice misfit in a single-crystal of the MC2 nickel-based superalloy is determined using convergent beam electron diffraction measurements and finite element calculations. The apparent lattice parameters of both constrained phases are obtained in thin foils, using a new multi-pattern approach, which allows for unambiguous determination of all the lattice parameters considering the real symmetry of the strained crystals. Finite element calculations are used to establish relations between the constrained and unconstrained lattice parameters, with the stress relaxation resulting from the thin foil geometry taken into account.

  20. Resistivity-Microstructure Relationships in Nickel Base Superalloys Used in Gas Turbine Engines for Power Generation and as Interconnects in Solid Oxide Fuel Cells

    SciTech Connect

    Gerhardt, Rosario A.

    2012-02-20

    This report summarizes the results accomplished during this 3-year with funds from this grant. The most important new contribution was the development of a microstructural model, based on analysis of the small angle scattering spectra that can relate the measured electrical resistivity to the precipitate population present in a nickel base superalloy in a quantitative way. A total of 24 research articles were published or were in press at the time the final report was written.

  1. Selection of etching methods of primary carbides in MAR-M247 nickel-base superalloy for computer-aided quantitative metallography

    SciTech Connect

    Szczotok, Agnieszka . E-mail: agnieszka.szczotok@polsl.pl; Szala, Janusz . E-mail: janusz.szala@polsl.pl; Cwajna, Jan . E-mail: jan.cwajna@polsl.pl; Hetmanczyk, Marek . E-mail: marek.hetmanczyk@polsl.pl

    2006-06-15

    The usefulness of various etching methods for revealing the structure of MAR-M247 nickel-base superalloy and image acquisition methods were analyzed from a desire to estimate primary carbides quantitatively. The analysis was carried out on images registered using light and scanning electron microscopes. The analyzed images contained a complete range of primary carbides occurring in the matrix and on the grain boundaries of MAR-M247 alloy.

  2. Homogenizing a Nickel-Based Superalloy: Thermodynamic and Kinetic Simulation and Experimental Results

    SciTech Connect

    Paul D. Jablonski; Christopher J. Cowen

    2009-03-01

    If the chemical inhomogeneity profile is known a priori, kinetic modeling software such as diffusion-controlled transformations (DICTRA) can be used to model the homogenization kinetics of an alloy. In this study, the Scheil module within the Thermo-Calc software was used to predict the as-cast segregation present within the Ni-based superalloy Nimonic 105. The segregation profiles were read into DICTRA to refine the homogenization heat treatment of this alloy. The thermodynamic and kinetic modeling of the computationally predicted heat treatment and microstructure, and subsequent experimental verification on a real casting of Nimonic 105, are presented.

  3. Methodological fundamentals of computer-assisted designing of nickel-based superalloys

    NASA Astrophysics Data System (ADS)

    Logunov, A. V.; Shmotin, Yu. N.; Danilov, D. V.

    2015-12-01

    More than 180 Russian and foreign nickel superalloys are analyzed to develop regression models to find a relation between chemical composition and a number of the most important thermodynamic, structural, and strength parameters, which directly influence the high-temperature strength of the alloys. The high accuracy of constructing the characteristics of distribution of alloying elements between the γ and γ' phases under scarce experimental data conditions is ensured by the application of bunch map analysis of random characteristics, which allowed the reliability of the calculated results to be significantly increased.

  4. Analysis of Grain Boundary Character in a Fine-Grained Nickel-Based Superalloy 718

    NASA Astrophysics Data System (ADS)

    Araujo, L. S.; dos Santos, D. S.; Godet, S.; Dille, J.; Pinto, A. L.; de Almeida, L. H.

    2014-11-01

    In the current work, sheets of superalloy 718 were processed via thermomechanical route by hot and cold rolling, followed by annealing below the δ phase solvus temperature and precipitation hardening to optimum strength. Grain boundary character distribution throughout the processing was mapped via EBSD and its evolution discussed. The results show that it is possible to process the alloy to a fine grain size obtaining concomitantly a considerably high proportion of special boundaries Σ3, Σ9, and Σ27. The precipitation of δ phase presented a strong grain refining role, without significantly impairing the twinning mechanism and, consequently, the Σ3, Σ9, and Σ27 boundary formations.

  5. Multiscale Characterization of Deformation Mechanisms in the Weld Joint of a Nickel-based Superalloy

    SciTech Connect

    Barabash, Oleg M.; Horton, Joe; Babu, Suresh; Vitek, John; David, Stan; Ice, Gene; Barabash, Rozaliya

    2007-12-19

    Multiscale plastic deformation in the heat affected zone (HAZ) of a Ni-based single crystal superalloy has been characterized using white microbeam synchrotron diffraction measurements together with OIM imaging, electron and optical microscopy. Characteristic length scales on the macro, meso and nano scale are determined. Dissolution of the {gamma} - phase particles during heating and secondary precipitation of {gamma} - phase during cooling is found, as well as formation and multiplication of dislocations. This process is more intense as one approaches the fusion line (FL). In the regions immediately neighboring the FL, {gamma} - phase particles dissolve completely and re-precipitate from the solid solution in the form of very small (50-70nm) particles. In the immediate vicinity of the FL, the temperature gradient and the rate of it's change reaches maximal values and causes the formation of large amounts of dislocations. Dislocations are concentrated in the ? matrix of the single crystal superalloy. X-ray Laue diffraction (both conventional and microbeam) and electron microscopy show that alternating dislocations slip systems dominate in the HAZ with typical Burgers vector b=[110]. Local lattice rotations in different zones of the weld joint are linking with the microslip events in different zones of the weld.

  6. Multiscale Characterization of Deformation Mechanisms in the Weld Joint of a Nickel-based Superalloy

    SciTech Connect

    Barabash, Oleg M

    2005-01-01

    Multiscale plastic deformation in the heat affected zone (HAZ) of a Ni-based single crystal superalloy has been characterized using white microbeam synchrotron diffraction measurements together with OIM imaging, electron and optical microscopy. Characteristic length scales on the macro, meso and nano scale are determined. Dissolution of the {gamma}{prime} - phase particles during heating and secondary precipitation of {gamma}{prime} - phase during cooling is found, as well as formation and multiplication of dislocations. This process is more intense as one approaches the fusion line (FL). In the regions immediately neighboring the FL, {gamma}{prime} - phase particles dissolve completely and re-precipitate from the solid solution in the form of very small (50-70nm) particles. In the immediate vicinity of the FL, the temperature gradient and the rate of it's change reaches maximal values and causes the formation of large amounts of dislocations. Dislocations are concentrated in the {gamma} matrix of the single crystal superalloy. X-ray Laue diffraction (both conventional and microbeam) and electron microscopy show that alternating dislocations slip systems dominate in the HAZ with typical Burgers vector b=[110]. Local lattice rotations in different zones of the weld joint are linking with the microslip events in different zones of the weld.

  7. Multiscale characterization of deformation mechanisms in the weld joint of a nickel-based superalloy

    SciTech Connect

    Barabash, Oleg M; Horton Jr, Joe A; Babu, Sudarsanam S; Vitek, John Michael; David, Stan A; Ice, Gene E; Barabash, Rozaliya

    2005-01-01

    Multiscale plastic deformation in the heat affected zone (HAZ) of a Ni-based single crystal superalloy has been characterized using white microbeam synchrotron diffraction measurements together with OIM imaging, electron and optical microscopy. Characteristic length scales on the macro, meso and nano scale are determined. Dissolution of the gamma' - phase particles during heating and secondary precipitation of gamma' during cooling is found, as well as formation and multiplication of dislocations. This process is more intense as one approaches the fusion line (FL). In the regions immediately neighboring the FL, gamma' - phase particles dissolve completely and re-precipitate from the solid solution in the form of very small (10-20nm) particles. In the immediate vicinity of the FL, the temperature gradient and the rate of it's change reaches maximal values and causes the formation of large amounts of dislocations. Dislocations are concentrated in the gamma matrix of the single crystal superalloy. X-ray Laue diffraction (both conventional and microbeam) and electron microscopy show that alternating dislocations slip systems dominate in the HAZ with Burgers vector b=[110] and dislocation lines [1-12] and [1-1-2] ; or b=[-110], dislocation lines [112] and [11-2] . Each of these two dislocation groups forms two Z-shaped dislocation lines fluctuating around two cubic directions [100] and [010]. Local lattice rotations in different zones of the weld joint are linking with the microslip events in different zones of the weld.

  8. Effect of B, Zr, and C on Hot Tearing of a Directionally Solidified Nickel-Based Superalloy

    NASA Astrophysics Data System (ADS)

    Grodzki, J.; Hartmann, N.; Rettig, R.; Affeldt, E.; Singer, R. F.

    2016-06-01

    The effect of the minor elements B, Zr, and C on the castability of a Nickel-based γ'-strengthened superalloy has been investigated. Tube-like specimens were prepared by directional solidification where the rigid ceramic core leads to hoop stresses and grain boundary cracking. It was found that an important improvement in castability can be achieved by adjusting the minor elemental composition. Too low C (≤0.15 pct) and too high B and Zr contents (≥0.05 pct) lead to material that is very prone to solidification cracking and should be avoided. The results cannot be rationalized on the basis of the current models for solidification cracking. Instead, pronounced hot tearing is observed to occur at high amounts of γ/ γ'-eutectic and high Zr contents. The critical film stage where dendrites at the end of solidification do not touch and are separated by thin liquid films must be avoided. How Zr promotes the film stage will be discussed in the paper.

  9. Effect of Notches on Creep-Fatigue Behavior of a P/M Nickel-Based Superalloy

    NASA Technical Reports Server (NTRS)

    Telesman, Jack; Gabb, Timothy P.; Ghosn, Louis J.; Gayda, John, Jr.

    2015-01-01

    A study was performed to determine and model the effect of high temperature dwells on notched low cycle fatigue (NLCF) and notch stress rupture behavior of a fine grain LSHR powder metallurgy (PM) nickel-based superalloy. It was shown that a 90 second dwell applied at the minimum stress (min dwell) was considerably more detrimental to the NLCF lives than similar dwell applied at the maximum stress (max dwell). The short min dwell NLCF lives were shown to be caused by growth of small oxide blisters which caused preferential cracking when coupled with high concentrated notch root stresses. The cyclic max dwell notch tests failed mostly by a creep accumulation, not by fatigue, with the crack origin shifting internally to a substantial distance away from the notch root. The classical von Mises plastic flow model was unable to match the experimental results while the hydrostatic stress profile generated using the Drucker-Prager plasticity flow model was consistent with the experimental findings. The max dwell NLCF and notch stress rupture tests exhibited substantial creep notch strengthening. The triaxial Bridgman effective stress parameter was able to account for the notch strengthening by collapsing the notched and uniform gage geometry test data into a singular grouping.

  10. The fracture morphology of nickel-base superalloys tested in fatigue and creep-fatigue at 650 C

    NASA Technical Reports Server (NTRS)

    Gayda, J.; Miner, R. V.

    1981-01-01

    The fracture surfaces of compact tension specimens from seven nickel-base superalloys fatigue tested at 650 C were studied by scanning electron microscopy and optical metallography to determine the nature and morphology of the crack surface in the region of stable growth. Crack propagation testing was performed as part of an earlier study at 650 C in air using a 0.33 Hz fatigue cycle and a creep-fatigue cycle incorporating a 900 second dwell at maximum load. In fatigue, alloys with a grain size greater than 20 micrometers, HIP Astroloy, Waspaloy, and MERL 76, exhibited transgranular fracture. MERL 76 also displayed numerous fracture sites which were associated with boundaries of prior powder particles. The two high strength, fine grain alloys, IN 100 and NASA IIB-7, exhibited intergranular fracture. Rene 95 and HIP plus forged Astroloy displayed a mixed failure mode that was transgranular in the coarse grains and intergranular in the fine grains. Under creep-fatigue conditions, fracture was found to be predominantly intergranular in all seven alloys.

  11. Multi-objective constrained design of nickel-base superalloys using data mining- and thermodynamics-driven genetic algorithms

    NASA Astrophysics Data System (ADS)

    Menou, Edern; Ramstein, Gérard; Bertrand, Emmanuel; Tancret, Franck

    2016-06-01

    A new computational framework for systematic and optimal alloy design is introduced. It is based on a multi-objective genetic algorithm which allows (i) the screening of vast compositional ranges and (ii) the optimisation of the performance of novel alloys. Alloys performance is evaluated on the basis of their predicted constitutional and thermomechanical properties. To this end, the CALPHAD method is used for assessing equilibrium characteristics (such as constitution, stability or processability) while Gaussian processes provide an estimate of thermomechanical properties (such as tensile strength or creep resistance), based on a multi-variable non-linear regression of existing data. These three independently well-assessed tools were unified within a single C++ routine. The method was applied to the design of affordable nickel-base superalloys for service in power plants, providing numerous candidates with superior expected microstructural stability and strength. An overview of the metallurgy of optimised alloys, as well as two detailed examples of optimal alloys, suggest that improvements over current commercial alloys are achievable at lower costs.

  12. Description of a high temperature quenching furnace for the study of the directional solidification of nickel-base superalloys

    SciTech Connect

    Schmale, D.T.; Kelley, J.B.; Damkroger, B.K.

    1994-06-01

    A high temperature resistance furnace has been modified for the study of directional solidification of nickel-base superalloys such as alloys 718 and 625. The furnace will be used to study segregation and solidification phenomena that occur in consumable-electrode melting processes such as vacuum arc remelting and electro-slag remelting. The system consists of a water cooled high temperature furnace (maximum temperature {approximately}2900 C), roughing vacuum,system, cooling system, cooled hearth, molten metal quenching bath, and a mechanism to lower the hearth from the furnace into the molten metal bath. The lowering mechanism is actuated by a digital stopping motor with a programmable controller. The specimen (1.9 cm dia {times} 14 cm long) is melted and contained within an alumina tube (2.54 cm dia {times} 15.24 cm long) which is seated on a copper hearth cooled with {approximately}13 C water. Directional solidification can then be accomplished by decreasing the furnace temperature while holding the specimen in position, maintaining the temperature gradient in the furnace and lowering the specimen at a controlled rate or a combination of both. At any point the specimen can be lowered rapidly into the 70 C molten metal bath to quench the specimen, preserve the solidification structure, and minimize solid state diffusion, enhancing the ability to study the localized solidification conditions.

  13. Fatigue Crack Growth Mechanisms for Nickel-based Superalloy Haynes 282 at 550-750 °C

    NASA Astrophysics Data System (ADS)

    Rozman, Kyle A.; Kruzic, Jamie J.; Sears, John S.; Hawk, Jeffrey A.

    2015-10-01

    The fatigue crack growth rates for nickel-based superalloy Haynes 282 were measured at 550, 650, and 750 °C using compact tension specimens with a load ratio of 0.1 and cyclic loading frequencies of 25 and 0.25 Hz. The crack path was observed to be primarily transgranular for all temperatures, and the observed effect of increasing temperature was to increase the fatigue crack growth rates. The activation energy associated with the increasing crack growth rates over these three temperatures was calculated less than 60 kJ/mol, which is significantly lower than typical creep or oxidation mechanisms; therefore, creep and oxidation cannot explain the increase in fatigue crack growth rates. Transmission electron microscopy was done on selected samples removed from the cyclic plastic zone, and a trend of decreasing dislocation density was observed with increasing temperature. Accordingly, the trend of increasing crack growth rates with increasing temperature was attributed to softening associated with thermally assisted cross slip and dislocation annihilation.

  14. The effect of hydrogen on deformation substructure, flow and fracture in a nickel-base single crystal superalloy

    NASA Technical Reports Server (NTRS)

    Dollar, M.; Bernstein, I. M.

    1988-01-01

    The room temperature flow and fracture of a nickel-base single crystal gamma/gamma-/prime superalloy in the presence and absence of hydrogen is explored. The procedure of hydrogen-charging employed in this study provides a very high and uniform hydrogen concentration of the order of 5000 at.-ppm in the material. It is shown that the most compelling hydrogen-induced changes in deformation behavior are enhanced dislocation accumulation in the gamma matrix and extensive cross-slip of super-dislocations. The explanation of these changes is proposed. Both effects contribute to the increase of flow stress and the notable work hardening that occurs prior to fracture. Hydrogen enhanced strain localization in the gamma matrix leads to the dramatic loss of ductility and premature cracking, which manifests as failure macroscopically parallel to the 100-plane-oriented faces of gamma-prime precipitates. On the microscale, cracking, while limited to the gamma matrix, occurs parallel to multiple 111-plane-oriented slip systems.

  15. High-temperature measurements of lattice parameters and internal stresses of a creep-deformed monocrystalline nickel-base superalloy

    NASA Astrophysics Data System (ADS)

    Biermann, Horst; Strehler, Marcus; Mughrabi, Haël

    1996-04-01

    High-temperature X-ray line profile measurements were performed to maximal temperatures of 1050 °C on samples of the nickel-base superalloy SRR 99. The samples with rod axes near the [001] direction were investigated in the initially undeformed state and after creep deformation at different temperatures and stresses. For the measurements of the (002) and (020) line profiles, a special X-ray double crystal diffractometer with negligible line broadening was used which was equipped with a high-temperature vacuum chamber. The line profiles were evaluated for the lattice parameters of the matrix phase γ and the precipitated γ' phase and for values of the lattice mismatch parallel and perpendicular to the stress axis, respectively, which were found to be different. Elastic, tetragonal distortions of the phases γ and γ' could be determined between room temperature and about 900 °C. These distortions are thermally induced due to the different thermal expansion coefficients of the two phases and deformation induced due to interfacial dislocation networks which were built up during deformation. At the high temperatures of the X-ray measurements, at least partial recovery of the deformation-induced internal stresses occurred, depending on the temperature of the X-ray measurements. The results are discussed and compared with data obtained by complementary techniques.

  16. The Cyclic Stress-Strain Behavior of a Single Crystal Nickel-Base Superalloy. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.

    1988-01-01

    The cyclic stress-strain response and similar deformation structures of the single crystal nickel based superalloy was described under a specific set of conditions. The isothermal low cycle fatigue response and deformation structures were described at a typical intermediate temperature and at high temperature. Specimens oriented near the (001) and (111) crystallographic orientations were tested at 1050 C, where more moderate orientation effects were expected. This enabled the description of the deformation structures at each of the 2 temperatures and their relationship to the observed cyclic stress-strain behavior. The initial yield strength of all specimens tested at 650 C was controlled by the shearing of the gamma prime precipitates by dislocation pairs. Low cycle fatigue tests at 650 C had cyclic hardening, which was associated with dislocation interactions in the gamma matrix. The initial yield strength of specimens tested at 1050 C was associated with dislocation bypassing of the gamma prime precipitates. Low cycle fatigue tests at 1050 C had cyclic softening, associated with extensive dislocation recovery at the gamma-gamma prime interfaces along with some gamma prime precipitate coarsening.

  17. On the Feasibility of Eddy Current Characterization of the Near-Surface Residual Stress Distribution in Nickel-Base Superalloys

    SciTech Connect

    Blodgett, Mark P.; Nagy, Peter B.

    2004-02-26

    In light of its frequency-dependent penetration depth, the measurement of eddy current conductivity has been suggested as a possible means to allow the nondestructive evaluation of subsurface residual stresses in shot-peened specimens. This technique is based on the so-called electroelastic effect, i.e., the stress-dependence of the electrical conductivity. Unfortunately, the relatively small ({approx}1%) change in electrical conductivity caused by the presence of compressive residual stresses is often distorted, or even completely overshadowed, by the accompanying conductivity loss caused by cold work and surface roughness effects. Recently, it was observed that, in contrast with most other materials, shot-peened Waspaloy and IN100 specimens exhibit an apparent increase in electrical conductivity at increasing inspection frequencies. This observation by itself indicates that in these materials the measured conductivity change is probably dominated by residual stress effects, since both surface roughness and increased dislocation density are known to decrease rather than increase the conductivity and the presence of crystallographic texture does not affect the electrical conductivity of these materials, which crystallize in cubic symmetry. Our preliminary experiments indicate that probably there exists a unique 'window of opportunity' for eddy current NDE in nickel-base superalloys. We identified five major effects that contribute to this fortunate constellation of material properties, which will be reviewed in this presentation.

  18. Microstructural Changes of a Creep-Damaged Nickel-Based K002 Superalloy Containing Hf Element under Different HIP Temperatures

    NASA Astrophysics Data System (ADS)

    Wang, Xiaomeng; Zhou, Yu; Dong, Jian; Wang, Tianyou; Zhao, Zihua; Zhang, Zheng

    2016-02-01

    Effects of hot isostatic pressing (HIP) temperature on the microstructural evolution of a nickel-based K002 superalloy containing Hf element after long-term service were investigated using three different soaking temperatures during HIP. The degraded γ' precipitates represented coarse and irregular morphology after long-term service. These γ' precipitates still were of coarse and irregular shape, but the size and volume fraction of γ' precipitates were markedly reduced under HIP condition of 1,190°C/200 MPa/4 h, indicating that the γ' precipitates were experiencing a dissolution process. Meanwhile, the concentrically oriented N-type γ' rafting structure around the cavities was formed. With HIP temperature increase to 1,220°C and 1,250°C, the small-sized, cubic and regular γ' precipitates were re-precipitated, and the concentrically oriented γ' structure vanished. The unstable morphology induced by the nucleation and growth of γ matrix was found near the creep cavities, indicating that the solute atoms diffused inward the creep-induced cavities during HIP. However, at HIP temperature of 1,220°C and 1,250°C, a large number of blocky MC(2)-type carbides containing amounts of Hf elements were precipitated, demonstrating that HIP treatment at higher temperatures can result in the formation of a large number of blocky MC(2)-type carbides.

  19. The influence of cobalt, tantalum, and tungsten on the elevated temperature mechanical properties of single crystal nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Nathal, M. V.; Ebert, L. J.

    1985-01-01

    The influence of composition on the tensile and creep strength of 001-line oriented nickel-base superalloy single crystals at temperatures near 1000 C was investigated. Cobalt, tantalum, and tungsten concentrations were varied according to a matrix of compositions based on the single crystal version of MAR-M247. For alloys with the baseline refractory metal level of 3 wt pct Ta and 10 wt pct W, decreases in Co level from 10 to 0 wt pct resulted in increased tensile and creep strength. Substitution of 2 wt pct W for 3 wt pct Ta resulted in decreased creep life at high stresses, but improved life at low stresses. Substitution of Ni for Ta caused large reductions in tensile strength and creep resistance, and corresponding increases in ductility. For these alloys with low Ta-plus-W totals, strength was independent of Co level. The effects of composition on properties were related to the microstructural features of the alloys. In general, high creep strength was associated with high levels of gamma-prime volume fraction, gamma-gamma-prime lattice mismatch, and solid solution hardening.

  20. The influence of cobalt, tantalum, and tungsten on the microstructure of single crystal nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Nathal, M. V.; Ebert, L. J.

    1985-01-01

    The influence of composition on the microstructure of single crystal nickel-base superalloys was investigated. Co was replaced by Ni, and Ta was replaced by either Ni or W, according to a matrix of compositions based on MAR-M247. Substitution of Ni for Co caused an increase in gamma-prime solvus temperature, an increase in gamma-gamma-prime lattice mismatch, and the precipitation of W-rich phases in the alloys with high refractory metal levels. Substitution of Ni for Ta caused large decreases in gamma-prime solvus temperature, gamma-prime volume fraction, and gamma-gamma-prime lattice mismatch, whereas substitution of W for Ta resulted in smaller decreases in these features. For the alloys with gamma-prime particles that remained coherent, substitution of Ni for Co caused an increase in gamma-prime coarsening rate. The two alloys with the largest magnitude of lattice mismatch possessed gamma-prime particles which lost coherency during unstressed aging and exhibited anomalously low coarsening rates. Creep exposure at 1000 C resulted in the formation of gamma-prime lamellae oriented perpendicular to the applied stress axis in all alloys.

  1. Microstructural Characterization of a Polycrystalline Nickel-Based Superalloy Processed via Tungsten-Intert-Gas-Shaped Metal Deposition

    NASA Astrophysics Data System (ADS)

    Clark, Daniel; Bache, Martin R.; Whittaker, Mark T.

    2010-12-01

    Recent trials have produced tungsten-inert-gas (TIG)-welded structures of a suitable scale to allow an evaluation of the technique as an economic and commercial process for the manufacture of complex aeroengine components. The employment of TIG welding is shown to have specific advantages over alternative techniques based on metal inert gas (MIG) systems. Investigations using the nickel-based superalloy 718 have shown that TIG induces a smaller weld pool with less compositional segregation. In addition, because the TIG process involves a pulsed power source, a faster cooling rate is achieved, although this rate, in turn, compromises the deposition rate. The microstructures produced by the two techniques differ significantly, with TIG showing an absence of the detrimental delta and Laves phases typically produced by extended periods at a high temperature using MIG. Instead, an anisotropic dendritic microstructure was evident with a preferred orientation relative to the axis of epitaxy. Niobium was segregated to the interdendritic regions. A fine-scale porosity was evident within the microstructure with a maximum diameter of approximately 5 μm. This porosity often was found in clusters and usually was associated with the interdendritic regions. Subsequent postdeposition heat treatment was shown to have no effect on preexisting porosity and to have a minimal effect on the microstructure.

  2. Thermodynamic analysis of the oxidation period of making a nickel-based multicomponent superalloy

    NASA Astrophysics Data System (ADS)

    Shil'nikov, E. V.; Alpatov, A. V.; Paderin, S. N.

    2013-11-01

    The oxygen activity is studied by oxygen sensors during the oxidation period in experimental heat of a superalloy in a 5-t electric arc furnace. The results of chemical analysis of metal and slag samples are used to calculate the activities of the metallic and oxide solution components using the energy parameters of the models of a pseudosubregular solution for the melt and a pseudoregular ionic solution for the slag, which were determined and presented in our earlier works. Equations are derived for the activity of oxygen in equilibrium with all melt components simultaneously and with each component individually. The entire oxidation process and the oxidation reaction of each metallic solution component are analyzed by comparing the actual and equilibrium oxygen activities in the metal at the beginning, middle, and end of the oxidation period of heat. The driving forces of the oxidation process are calculated from the difference between the actual and equilibrium chemical potentials of oxygen.

  3. Formation of Minor Phases in a Nickel-Based Disk Superalloy

    NASA Technical Reports Server (NTRS)

    Gabb, T. P.; Garg, A.; Miller, D. R.; Sudbrack, C. K.; Hull, D. R.; Johnson, D.; Rogers, R. B.; Gayda, J.; Semiatin, S. L.

    2012-01-01

    The minor phases of powder metallurgy disk superalloy LSHR were studied. Samples were consistently heat treated at three different temperatures for long times to approximate equilibrium. Additional heat treatments were also performed for shorter times, to then assess non-equilibrium conditions. Minor phases including MC carbides, M23C6 carbides, M3B2 borides, and sigma were identified. Their transformation temperatures, lattice parameters, compositions, average sizes and total area fractions were determined, and compared to estimates of an existing phase prediction software package. Parameters measured at equilibrium sometimes agreed reasonably well with software model estimates, with potential for further improvements. Results for shorter times representing non-equilibrium indicated significant potential for further extension of the software to such conditions, which are more commonly observed during heat treatments and service at high temperatures for disk applications.

  4. Fatigue crack growth and low cycle fatigue of two nickel base superalloys

    NASA Technical Reports Server (NTRS)

    Stoloff, N. S.; Duquette, D. J.; Choe, S. J.; Golwalkar, S.

    1983-01-01

    The fatigue crack growth and low cycle fatigue behavior of two P/M superalloys, Rene 95 and Astroloy, in the hot isostatically pressed (HIP) condition, was determined. Test variables included frequency, temperature, environment, and hold times at peak tensile loads (or strains). Crack initiation sites were identified in both alloys. Crack growth rates were shown to increase in argon with decreasing frequency or with the imposition of hold times. This behavior was attributed to the effect of oxygen in the argon. Auger analyses were performed on oxide films formed in argon. Low cycle fatigue lives also were degraded by tensile hold, contrary to previous reports in the literature. The role of environment in low cycle fatigue behavior is discussed.

  5. Structure-property effects of tantalum additions to nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Heckel, R. W.; Pletka, B. J.; Koss, D. A.; Jackson, M. R.

    1982-01-01

    The characterization of the effect of Ta on the structure of Ni base superalloys, the determination of the effects of Ta (structure) variations on the mechanical, thermal, and oxidation behavior, and the identification of alloying elements which have potential as substitutes for Ta are investigated. Mar M247 type alloys are emphasized; nominal and analyzed compositions of ten alloys under study are given. X-ray and composition analysis are being used to determine the partitioning of alloying elements between gamma, gamma primes, and MC (cubic) as a function of Ta content. The diffusional interactions of the Mar M247-type alloys with as cast beta + gamma alloys are studied to determine the effects of Ta on alloy/coating degradation.

  6. Influence of microstructures on thermal fatigue property of a nickel-base superalloy

    NASA Astrophysics Data System (ADS)

    Xia, Peng-Cheng; Chen, Feng-Wen; Xie, Kun; Qiao, Ling; Yu, Jin-Jiang

    2015-03-01

    Effect of microstructures such as the distribution and shape of carbide and γ' phase on thermal fatigue property of a superalloy was investigated experimentally. The resistance of thermal fatigue of the studied alloy decreases with the rising upper temperature. For the as-cast alloy, the thermal fatigue crack mostly origins from carbide at low upper temperature and results from oxidation at high upper temperature. The thermal fatigue crack of the heat treated alloy is mainly initiated by the oxidized cavity and then propagates through the join of the oxidized cavity. The orientation of crack propagation and direction of dendrite growth of alloy have the angle of 45°. There is γ' denuded region near the thermal fatigue crack because of oxidation.

  7. Creep property and microstructure evolution of a nickel-base single crystal superalloy in [011] orientation

    SciTech Connect

    Han, G.M. Yu, J.J.; Hu, Z.Q.; Sun, X.F.

    2013-12-15

    The creep property and microstructure evolution of a single crystal superalloy with [011] orientation were investigated at the temperatures of 700 °C, 900 °C and 1040 °C. It is shown that there exist stages of primary, steady-state, and tertiary creep under the lower temperature 700 °C. As the temperature increases to high temperatures of 900 °C and 1040 °C, steady-state creep stage is reduced or disappears and the shape of creep curves is dominated by an extensive tertiary stage. The minimum creep strain rate exhibits power law dependence on the applied stress; the stress exponents at 700 °C, 900 °C and 1040 °C are 28, 13 and 6.5, respectively. Microstructure observation shows that the morphologies of γ′ phase almost keep original shape at the lower temperature 700 °C and high applied stress. With the increasing creep temperature, γ′ precipitates tend to link together and form lamellar structure at an angle of 45° inclined to the applied stress. Transmission electron microscopy (TEM) investigations reveal that multiple < 110 > (111) slip systems gliding in the matrix channels and shearing γ′ precipitates by stacking faults or bending dislocation pairs are the main deformation mechanism at the lower temperature of 700 °C. At the high temperatures of 900 °C and 1040 °C, dislocation networks are formed at γ/γ′ interfaces and the γ′ rafts are sheared by dislocation pairs. - Highlights: • Creep properties of < 011 >-oriented single crystal superalloys were investigated. • γ′ phases become rafting at an angle of 45° inclined to the applied stress. • Creep deformation mechanisms depend on temperature and stress.

  8. The stability of lamellar gamma-gamma-prime structures. [nickel-base superalloy

    NASA Technical Reports Server (NTRS)

    Nathal, M. V.; Mackay, R. A.

    1987-01-01

    The stability of stress-annealed gamma/gamma-prime lamellar structures were investigated using three nickel-base single-crystal alloys (the NASAIR 100 and two similar alloys, E and F, containing 5 and 10 wt pct Co, respectively) stress-annealed at 1000 C to form lamellae perpendicular to the applied stress. The rate of the lamellar thickening under various thermal and creep exposures was examined by SEM. For unstressed aging at 1100 C, the lamellar structures of the NASAIR and the E alloys exhibited continuous but slow lamellar coarsening, whereas the lamellae of the alloy F showed pronounced thickening plus spheroidization. Resistance to lamellar thickening was correlated with high magnitudes of lattice mismatch, which promoted a more regular lamellar structure and a finer spacing of misfit dislocations. Specimens which were tension-annealed prior to compressive creep testing exhibited an earlier onset of tertiary creep in comparison with only heat-treated specimens. This was associated with accelerated lamellar coarsening in the stress-annealed specimens.

  9. Microscopic evaluation of creep-fatigue interaction in a nickel-based superalloy

    SciTech Connect

    Santella, Michael L; Yamamoto, Masato; Shingledecker, John P; Boehlert, C. J.; Ogata, Takashi

    2009-01-01

    In order to verify the applicability of Nickel-based alloy Alloy 263 for the thick component, a series of creep, fatigue and creep-fatigue experiments were carried out. To investigate the detailed damage process under the creep-fatigue condition, simple aged, crept, fatigued, and creep-fatigued specimens were subjected to electron back scattering diffraction (EBSD) pattern observation in the SEM. While the simple aged and fatigued specimens showed no remarkable local change in orientation (less than 1deg), the crept specimen exhibited inhomogeneous change of crystallographic orientation, at most 5 degrees, within the grains. This shows that the creep strain is inhomogeneously distributed in the grains due to the effect of relative constraint among the grains. The creep-fatigued specimen exhibited similar local inhomogeniety in strain distribution compared to the crept sample near the center of the grains. However, the creep-fatigued specimen showed remarkable local change in orientation at the vicinity of grain boundaries up to 15 degrees, indicating the occurrence of high strain concentration nearby the grain boundaries. A detailed observation of creep-fatigue damage evolution process in SEM revealed that the inhomogeneous grain deformation precedes the remarkable inhomogeneous deformation nearby the grain boundaries, and followed by the grain boundary cracking.

  10. CO2 laser cut quality of Inconel 718 nickel - based superalloy

    NASA Astrophysics Data System (ADS)

    Hasçalık, Ahmet; Ay, Mustafa

    2013-06-01

    This paper experimentally investigates the cut quality of laser cutting for the age hardened Inconel 718 nickel based super alloy, with the use of a continuous CO2 4.0 kW laser cutting system. The quality of the cut has been monitored by measuring the kerf taper ratio, the recast layer thickness and the surface roughness of the cut specimens. The effects of processing parameters, such as the laser power, the cutting speed and the assisting gas pressure were evaluated. Scanning electron microscopy (SEM), Energy Dispersive Spectrography (EDS), X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM) and Knoop hardness tests are carried out to examine the cutting defects, the kerf size variation and formed carbide on the surfaces. A statistical analysis of the results has been performed in order for the effect of each parameter on the cutting quality to be determined. The regression analysis has been used for the development of empirical models able to describe the effect of the process parameters on the quality of laser cutting.

  11. Quantitative characterization and comparison of precipitate and grain shape in Nickel -base superalloys using moment invariants

    NASA Astrophysics Data System (ADS)

    Callahan, Patrick Gregory

    A fundamental objective of materials science and engineering is to understand the structure-property-processing-performance relationship. We need to know the true 3-D microstructure of a material to understand certain geometric properties of a material, and thus fulfill this objective. Focused ion beam (FIB) serial sectioning allows us to find the true 3-D microstructure of Ni-base superalloys. Once the true 3-D microstructure is obtained, an accurate quantitative description and characterization of precipitate and/or grain shapes is needed to understand the microstructure and describe it in an unbiased way. In this thesis, second order moment invariants, the shape quotient Q, a convexity measure relating the volume of an object to the volume of its convex hull, V/Vconv, and Gaussian curvature have been used to compare an experimentally observed polycrystalline IN100 microstructure to three synthetic microstructures. The three synthetic microstructures used different shape classes to produce starting grain shapes. The three shape classes are ellipsoids, superellipsoids, and the shapes generated when truncating a cube with an octahedron. The microstructures are compared using a distance measure, the Hellinger distance. The Hellinger distance is used to compare distributions of shape descriptors for the grains in each microstructure. The synthetic microstructure that has the smallest Hellinger distance, and so best matched the experimentally observed microstructure is the microstructure that used superellipsoids as a starting grain shape. While it has the smallest Hellinger distance, and is approaching realistic grain morphologies, the superellipsoidal microstructure is still not realistic. Second order moment invariants, Q, and V/V conv have also been used to characterize the γ' precipitate shapes from four experimental Ru-containing Ni-base superalloys with differences in alloying additions. The superalloys are designated UM-F9, UM-F18, UM-F19, and UM-F22. The

  12. Temporal Evolution of Nanostructures in a Model Nickel-Base Superalloy: Experiments and Simulations

    NASA Technical Reports Server (NTRS)

    Sudbrack, Chantal K.; Yoon, Kevin E.; Mao, Zugang; Noebe, Ronald D.; Isheim, Dieter; Seidman, David N.

    2003-01-01

    The temporal evolution of the nanostructure of a model Ni-base superalloy (Ni-5.2 at.% Al-14.2 at.% Cr) is studied experimentally employing three-dimensional atom-probe (3DAP) microscopy in conjunction with kinetic Monte Carlo (KMC) simulations at 600 C. It is demonstrated that not only can the mean compositions of individual gamma' (Ni3Al with the Li2 structure) precipitates be measured but the Ni, Al, and Cr concentration profiles within the precipitates can also be determined for precipitates with a mean radius () as small as 0.85 nm. The three asymptotic tinie dependencies of the Lifshitz-Slyzov-Wagner (LSW) theory of coarsening (Ostwald ripening) are measured and found to deviate from its theoretical predictions: possible explanations for these discrepancies are discussed. At 0.25 hr. there is 3DAP microscope evidence for the presence of precipitates of another nickel-rich phase. ="Ni3Cr" (Ni3Cr(1-x)Al(x)), which exhibits short-range order (SRO) and that is metastable with respect to Ni3Al. This metastable phase is also found by KMC simulations and has the composition Ni3Cr(1-x)Al(x), which is Ni-2.91 at.% Al-21.98 at.% Cr at 16 hours. Our results demonstrate that the decomposition of gamma the primary gamma (FCC) phase results in the concurrent formation of an ordered phase and a disordered phase by 0.25 hours.

  13. Creep-Environment Interactions in Dwell-Fatigue Crack Growth of Nickel Based Superalloys

    NASA Astrophysics Data System (ADS)

    Maciejewski, Kimberly; Dahal, Jinesh; Sun, Yaofeng; Ghonem, Hamouda

    2014-05-01

    A multi-scale, mechanistic model is developed to describe and predict the dwell-fatigue crack growth rate in the P/M disk superalloy, ME3, as a function of creep-environment interactions. In this model, the time-dependent cracking mechanisms involve grain boundary sliding and dynamic embrittlement, which are identified by the grain boundary activation energy, as well as, the slip/grain boundary interactions in both air and vacuum. Modeling of the damage events is achieved by adapting a cohesive zone (CZ) approach which considers the deformation behavior of the grain boundary element at the crack tip. The deformation response of this element is controlled by the surrounding continuum in both far field (internal state variable model) and near field (crystal plasticity model) regions and the intrinsic grain boundary viscosity which defines the mobility of the element by scaling up the motion of dislocations into a mesoscopic scale. This intergranular cracking process is characterized by the rate at which the grain boundary sliding reaches a critical displacement. A damage criterion is introduced by considering the grain boundary mobility limit in the tangential direction leading to strain incompatibility and failure. Results of simulated intergranular crack growth rate using the CZ model are generated for temperatures ranging from 923 K to 1073 K (650 °C to 800 °C), in both air and vacuum. These results are compared with those experimentally obtained and analysis of the model sensitivity to loading conditions, particularly temperature and oxygen partial pressure, are presented.

  14. Formation and relaxation of coherency strain in the nickel-base superalloy SC16.

    PubMed

    Pinto, Haroldo Cavalcanti; Bruno, Giovanni

    2003-03-01

    An in situ study of the kinetics of relaxation of the gamma-gamma' lattice mismatch in the single-crystal Ni-base superalloy SC16 was carried out by means of high-energy synchrotron radiation diffraction. The high resolution achievable was exploited to measure the time variation of the gamma and gamma' lattice parameters during isothermal ageing at several temperatures, starting from the gamma' solvus point. On cooling from the solvus temperature (1523 K) the gamma' precipitate phase nucleates and grows following concurrent mechanisms. The variations of the gamma and gamma' peak position and integrated intensity could be followed by means of fundamental and superstructure reflections. At each temperature T < 1473 K the integrated intensity follows an Avrami time law. The gamma' Volume fraction increases as a function of time at each temperature. It increases with cooling, until saturation occurs at temperatures as low as 1075 K. The lattice mismatch follows an exponential time decay, while having larger values at high temperatures. The pArticles are born fully coherent, and the coherency strains the set-up. Over time, long-term ageing shows a stabilization of the misfit value, while the precipitates are supposed to lose their coherency to the matrix (within 3-4 h) and the strains relax. PMID:12606793

  15. Effect of Crystal Orientation on Analysis of Single-Crystal, Nickel-Based Turbine Blade Superalloys

    NASA Technical Reports Server (NTRS)

    Swanson, G. R.; Arakere, N. K.

    2000-01-01

    High-cycle fatigue-induced failures in turbine and turbopump blades is a pervasive problem. Single-crystal nickel turbine blades are used because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities. Single-crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant and complicating factor. A fatigue failure criterion based on the maximum shear stress amplitude on the 24 octahedral and 6 cube slip systems is presented for single-crystal nickel superalloys (FCC crystal). This criterion greatly reduces the scatter in uniaxial fatigue data for PWA 1493 at 1,200 F in air. Additionally, single-crystal turbine blades used in the Space Shuttle main engine high pressure fuel turbopump/alternate turbopump are modeled using a three-dimensional finite element (FE) model. This model accounts for material orthotrophy and crystal orientation. Fatigue life of the blade tip is computed using FE stress results and the failure criterion that was developed. Stress analysis results in the blade attachment region are also presented. Results demonstrate that control of crystallographic orientation has the potential to significantly increase a component's resistance to fatigue crack growth without adding additional weight or cost.

  16. Laser Clad Nickel Based Superalloys: Microstructure Evolution And High Temperature Oxidation Studies

    NASA Astrophysics Data System (ADS)

    Sircar, S.; Ribaudo, C.; Mazumder, J.

    1988-10-01

    Application of alloy coatings with superior oxidation resistance at elevated temperatures (1200°C) on superalloy components is of interest at present. There is a general consensus that the addition of rare earths such as hafnium (Hf) to these alloys has a pronounced effect on their performance. An in situ laser cladding technique was used to produce Ni-Al-Cr-Hf alloys on a nickel alloy substrate. Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), and Scanning Transmission Electron Microscope (STEM) attached with Energy Dispersive X-ray (EDX) analyzers were employed for microstructural evolution studies of alloys produced during the laser cladding process. The microstructure of these alloys mainly consists of dendrites of Y' of the Ni3Al type with about 11-14 wt% Hf and an interdendritic eutectic phase. Electron microscopy in the dendritic zones reveals ordered domains whose morphology depends on laser cladding process parameters. Variation in these parameters produced only subtle changes in the composition and cell spacing of the dendritic phase. The eutectic constituent consists of a Hf-rich phase and a Hf-lean phase in an alternating lamellar structure. Convergent beam diffraction and x-ray spectroscopy techniques were used to characterize the constituents. A possible phase transformation sequence has been suggested. Differential Thermal Analysis (DTA) work indicates that the Y' dissolution temperature for the claddings is at least as high as the substrate material (Rene 80). Single cycle oxidation tests of eight hours at 1200°C in slowly flowing air reveal that the claddings have a lower weight gain rate than the substrate itself. Microchemistry and microstructure of the oxidized samples are examined using SEM attached with EDX and Auger Electron Spectroscopic (AES) techniques. The improvement in the oxidation resistance is believed to be at least partially due to the mechanical pegging between alumina coated hafnia protrusions and the

  17. Effects of Microstructural Parameters on Creep of Nickel-Base Superalloy Single Crystals

    NASA Technical Reports Server (NTRS)

    MacKay, Rebecca A.; Gabb, Timothy P.; Nathal, Michael V.

    2013-01-01

    Microstructure-sensitive creep models have been developed for Ni-base superalloy single crystals. Creep rupture testing was conducted on fourteen single crystal alloys at two applied stress levels at each of two temperatures, 982 and 1093 C. The variation in creep lives among the different alloys could be explained with regression models containing relatively few microstructural parameters. At 982 C, gamma-gamma prime lattice mismatch, gamma prime volume fraction, and initial gamma prime size were statistically significant in explaining the creep rupture lives. At 1093 C, only lattice mismatch and gamma prime volume fraction were significant. These models could explain from 84 to 94 percent of the variation in creep lives, depending on test condition. Longer creep lives were associated with alloys having more negative lattice mismatch, lower gamma prime volume fractions, and finer gamma prime sizes. The gamma-gamma prime lattice mismatch exhibited the strongest influence of all the microstructural parameters at both temperatures. Although a majority of the alloys in this study were stable with respect to topologically close packed (TCP) phases, it appeared that up to approximately 2 vol% TCP phase did not affect the 1093 C creep lives under applied stresses that produced lives of approximately 200 to 300 h. In contrast, TCP phase contents of approximately 2 vol% were detrimental at lower applied stresses where creep lives were longer. A regression model was also developed for the as-heat treated initial gamma prime size; this model showed that gamma prime solvus temperature, gamma-gamma prime lattice mismatch, and bulk Re content were all statistically significant.

  18. Advanced nickel base alloys for high strength, corrosion applications

    DOEpatents

    Flinn, John E.

    1998-01-01

    Improved nickel-base alloys of enhanced strength and corrosion resistance, produced by atomization of an alloy melt under an inert gas atmosphere and of composition 0-20Fe, 10-30Cr, 2-12Mo, 6 max. Nb, 0.05-3 V, 0.08 max. Mn, 0.5 max. Si, less than 0.01 each of Al and Ti, less than 0.05 each of P and S, 0.01-0.08C, less than 0.2N, 0.1 max. 0, bal. Ni.

  19. Advanced nickel base alloys for high strength, corrosion applications

    DOEpatents

    Flinn, J.E.

    1998-11-03

    Improved nickel-base alloys of enhanced strength and corrosion resistance, produced by atomization of an alloy melt under an inert gas atmosphere and of composition 0--20Fe, 10--30Cr, 2--12Mo, 6 max. Nb, 0.05--3 V, 0.08 max. Mn, 0.5 max. Si, less than 0.01 each of Al and Ti, less than 0.05 each of P and S, 0.01--0.08C, less than 0.2N, 0.1 max. 0, bal. Ni. 3 figs.

  20. Liquation Microfissuring in the Weld Heat-Affected Zone of an Overaged Precipitation-Hardened Nickel-Base Superalloy

    NASA Astrophysics Data System (ADS)

    Ojo, O. A.; Chaturvedi, M. C.

    2007-02-01

    The effect of preweld overaging heat treatment on the microstructural response in the heat-affected zone (HAZ) of a precipitation-hardened nickel-base superalloy INCONEL 738LC subjected to the welding thermal cycle ( i.e., rapid) was investigated. The overaging heat treatment resulted in the formation of an interfacial microconstituent containing M23X6 particles and coarsening of primary and secondary γ' precipitates. The HAZ microstructures around welds in the overaged alloy were simulated using the Gleeble thermomechanical simulation system. Microstructural examination of simulated HAZs and those present in tungsten inert gas (TIG) welded specimens showed the occurrence of extensive grain boundary liquation involving liquation reaction of the interfacial microconstituents containing M23X6 particles and MC-type carbides. In addition, the coarsened γ' precipitate particles present in the overaged alloy persisted well above their solvus temperature to temperatures where they constitutionally liquated and contributed to considerable liquation of grain boundaries, during continuous rapid heating. Intergranular HAZ microfissuring, with resolidified product formed mostly on one side of the microfissures, was observed in welded specimens. This suggested that the HAZ microfissuring generally occurred by decohesion across one of the solid-liquid interfaces during the grain boundary liquation stage of the weld thermal cycle. Correlation of simulated HAZ microstructures with hot ductility properties of the alloy revealed that the temperature at which the alloy exhibited zero ductility during heating was within the temperature range at which grain boundary liquation was observed. The on-cooling ductility of the alloy was significantly damaged by the on-heating liquation reaction, as reflected by the considerably low ductility recovery temperature (DRT). Important characteristics of the intergranular liquid that could influence HAZ microfissuring of the alloy in overaged

  1. Crack initiation modeling of a directionally-solidified nickel-base superalloy

    NASA Astrophysics Data System (ADS)

    Gordon, Ali Page

    Combustion gas turbine components designed for application in electric power generation equipment are subject to periodic replacement as a result of cracking, damage, and mechanical property degeneration that render them unsafe for continued operation. In view of the significant costs associated with inspecting, servicing, and replacing damaged components, there has been much interest in developing models that not only predict service life, but also estimate the evolved microstructural state of the material. This thesis explains manifestations of microstructural damage mechanisms that facilitate fatigue crack nucleation in a newly-developed directionally-solidified (DS) Ni-base superalloy components exposed to elevated temperatures and high stresses. In this study, models were developed and validated for damage and life prediction using DS GTD-111 as the subject material. This material, proprietary to General Electric Energy, has a chemical composition and grain structure designed to withstand creep damage occurring in the first and second stage blades of gas-powered turbines. The service conditions in these components, which generally exceed 600°C, facilitate the onset of one or more damage mechanisms related to fatigue, creep, or environment. The study was divided into an empirical phase, which consisted of experimentally simulating service conditions in fatigue specimens, and a modeling phase, which entailed numerically simulating the stress-strain response of the material. Experiments have been carried out to simulate a variety of thermal, mechanical, and environmental operating conditions endured by longitudinally (L) and transversely (T) oriented DS GTD-111. Both in-phase and out-of-phase thermo-mechanical fatigue tests were conducted. In some cases, tests in extreme environments/temperatures were needed to isolate one or at most two of the mechanisms causing damage. Microstructural examinations were carried out via SEM and optical microscopy. A continuum

  2. Advanced protective coating for superalloys

    NASA Technical Reports Server (NTRS)

    Elam, R. C.; Talboom, F. P.; Wilson, L. W.

    1972-01-01

    Superior oxidation protection for nickel-base alloys at temperatures up to 1367 K was obtained with cobalt-base alloy coating. Coating had 25 Cr, 14 Al, and 0.5 Y weight percent composition. Coating was applied by electron beam vapor deposition to thickness of 76 to 127 microns.

  3. Multiphase wide gap braze alloys for the repair of nickel-base superalloy turbine components: Development and characterization

    NASA Astrophysics Data System (ADS)

    Nelson, Scott David

    Gas turbine components made of nickel-base superalloys experience cracking after service in extreme environments. As these cracks can be wide, brazing or fusion welding is typically used to repair them. Properly designed and applied, brazing filler metal will help extend the useful life of damaged turbine components. During repair of defective OEM parts, brazing is also considered, provided that proper filler metals with enhanced ductility and improved resistance to low-cycle fatigue are available. This research strives to develop the brazing technique and alloys to achieve a repair with acceptable mechanical properties. Additionally, the effects of silicon and boron, as fast diffusing and melting point suppressing elements on the braze microstructure and mechanical properties were examined in detail to help guide future alloy development. Three commercially available "low-temperature" brazing powders were mixed with an additive superalloy powder to prepare a series of filler metals for wide gap brazing used to repair OEM gas turbine components. BNi-2 (Ni-7Cr-4.2Si-3B-3Fe), BNi-5 (Ni-19Cr-10Si) and BNi-9 (Ni-15Cr-3.5B) were mixed with MARM247 (Ni-10W-10Co-8.25Cr-5.5Al-3Ta-1Ti-0.7Mo-0.5Fe-0.015B) at ratios of 40, 50, and 60 wt. pct. creating a total of nine experimental filler alloys. The brazes were applied to a 0.06 inch gap in a Rene 108(TM) substrate for mechanical and microstructural analysis. The wettability and flow of each of the experimental alloys were analyzed to determine the required brazing temperature through isothermal spreadability experiments. Bend testing was performed on brazed joints to determine their mechanical properties and maximum angular deflection. The metallurgical driving factors, such as solidification behavior and compositional effects, were analyzed to correlate the resulting microstructural constituents to the mechanical properties developed through experimentation. It was found that because of the solid solubility of silicon into

  4. Effect of volume fraction and size of fine-gamma prime particles on raising the creep strength of a DS nickel-base superalloy

    NASA Technical Reports Server (NTRS)

    Lin, D. L.; Yao, D. L.; Lin, X. J.; Sun, C. Q.

    1986-01-01

    The creep behavior of a directionally solidifified nickel-base superalloy, DKS3, has been investigated as a function of the volume fraction and size of the gamma-prime phase at 760 and 950 C. The dislocation structure and morphology of gamma-prime was examined by transmission electron microscopy at the primary, secondary and tertiary creep stages at 73.8 kgf/sq mm. Experimental results are described in terms of a high temperature creep model in the range of temperatures and applied stresses where shearing of the gamma-prime phase does not control the straining process.

  5. Microstructural, mechanical and weldability assessments of the dissimilar welds between γ′- and γ″-strengthened nickel-base superalloys

    SciTech Connect

    Naffakh Moosavy, Homam; Aboutalebi, Mohammad-Reza; Seyedein, Seyed Hossein; Mapelli, Carlo

    2013-08-15

    Dissimilar welding of γ′- and γ″-strengthened nickel-base superalloys has been investigated to identify the relationship between the microstructure of the welds and the resultant mechanical and weldability characteristics. γ′-Strengthened nickel-base Alloy 500 and γ″-strengthened nickel-base Alloy 718 were used for dissimilar welding. Gas tungsten arc welding operations were utilized for performing the autogenous dissimilar welding. Alloy 500 and Alloy 718 base metals showed various types of phases, carbides, intermetallics and eutectics in their microstructure. The results for Alloy 500 weld metal showed severe segregation of titanium to the interdendritic regions. The Alloy 718 weld metal compositional analysis confirmed the substantial role of Nb in the formation of low-melting eutectic-type morphologies which can reduce the weldability. The microstructure of dissimilar weld metal with dilution level of 65% wt.% displayed semi-developed dendritic structure. The less segregation and less formation of low-melting eutectic structures caused to less susceptibility of the dissimilar weld metal to the solidification cracking. This result was confirmed by analytic modeling achievements. Dissolution of γ″-Ni{sub 3}Nb precipitations took place in the Alloy 718 heat-affected zone leading to sharp decline of the microhardness in this region. Remelted and resolidified regions were observed in the partially-melted zone of Alloy 500 and Alloy 718. Nevertheless, no solidification and liquation cracking happened in the dissimilar welds. Finally, this was concluded that dissimilar welding of γ′- and γ″-strengthened nickel-base superalloys can successfully be performed. - Highlights: • Dissimilar welding of γ′- and γ″-strengthened nickel-base superalloys is studied. • Microstructural, mechanical and weldability aspects of the welds are assessed. • Microstructure of welds, bases and heat-affected zones is characterized in detail. • The type

  6. A novel unified dislocation density-based model for hot deformation behavior of a nickel-based superalloy under dynamic recrystallization conditions

    NASA Astrophysics Data System (ADS)

    Lin, Y. C.; Wen, Dong-Xu; Chen, Ming-Song; Chen, Xiao-Min

    2016-09-01

    In this study, a novel unified dislocation density-based model is presented for characterizing hot deformation behaviors in a nickel-based superalloy under dynamic recrystallization (DRX) conditions. In the Kocks-Mecking model, a new softening item is proposed to represent the impacts of DRX behavior on dislocation density evolution. The grain size evolution and DRX kinetics are incorporated into the developed model. Material parameters of the developed model are calibrated by a derivative-free method of MATLAB software. Comparisons between experimental and predicted results confirm that the developed unified dislocation density-based model can nicely reproduce hot deformation behavior, DRX kinetics, and grain size evolution in wide scope of initial grain size, strain rate, and deformation temperature. Moreover, the developed unified dislocation density-based model is well employed to analyze the time-variant forming processes of the studied superalloy.

  7. Quantitative experimental determination of the solid solution hardening potential of rhenium, tungsten and molybdenum in single-crystal nickel-based superalloys

    SciTech Connect

    Fleischmann, Ernst; Miller, Michael K.; Affeldt, Ernst; Glatzel, Uwe

    2015-01-31

    Here, the solid-solution hardening potential of the refractory elements rhenium, tungsten and molybdenum in the matrix of single-crystal nickel-based superalloys was experimentally quantified. Single-phase alloys with the composition of the nickel solid-solution matrix of superalloys were cast as single crystals, and tested in creep at 980 °C and 30–75 MPa. The use of single-phase single-crystalline material ensures very clean data because no grain boundary or particle strengthening effects interfere with the solid-solution hardening. This makes it possible to quantify the amount of rhenium, tungsten and molybdenum necessary to reduce the creep rate by a factor of 10. Rhenium is more than two times more effective for matrix strengthening than either tungsten or molybdenum. The existence of rhenium clusters as a possible reason for the strong strengthening effect is excluded as a result of atom probe tomography measurements. If the partitioning coefficient of rhenium, tungsten and molybdenum between the γ matrix and the γ' precipitates is taken into account, the effectiveness of the alloying elements in two-phase superalloys can be calculated and the rhenium effect can be explained.

  8. Quantitative experimental determination of the solid solution hardening potential of rhenium, tungsten and molybdenum in single-crystal nickel-based superalloys

    DOE PAGES

    Fleischmann, Ernst; Miller, Michael K.; Affeldt, Ernst; Glatzel, Uwe

    2015-01-31

    Here, the solid-solution hardening potential of the refractory elements rhenium, tungsten and molybdenum in the matrix of single-crystal nickel-based superalloys was experimentally quantified. Single-phase alloys with the composition of the nickel solid-solution matrix of superalloys were cast as single crystals, and tested in creep at 980 °C and 30–75 MPa. The use of single-phase single-crystalline material ensures very clean data because no grain boundary or particle strengthening effects interfere with the solid-solution hardening. This makes it possible to quantify the amount of rhenium, tungsten and molybdenum necessary to reduce the creep rate by a factor of 10. Rhenium is moremore » than two times more effective for matrix strengthening than either tungsten or molybdenum. The existence of rhenium clusters as a possible reason for the strong strengthening effect is excluded as a result of atom probe tomography measurements. If the partitioning coefficient of rhenium, tungsten and molybdenum between the γ matrix and the γ' precipitates is taken into account, the effectiveness of the alloying elements in two-phase superalloys can be calculated and the rhenium effect can be explained.« less

  9. Nickel base alloy. [for gas turbine engine stator vanes

    NASA Technical Reports Server (NTRS)

    Freche, J. C.; Waters, W. J. (Inventor)

    1977-01-01

    A nickel base superalloy for use at temperatures of 2000 F (1095 C) to 2200 F (1205 C) was developed for use as stator vane material in advanced gas turbine engines. The alloy has a nominal composition in weight percent of 16 tungsten, 7 aluminum, 1 molybdenum, 2 columbium, 0.3 zirconium, 0.2 carbon and the balance nickel.

  10. Effect of minor carbon additions on the high-temperature creep behavior of a single-crystal nickel-based superalloy

    SciTech Connect

    Wang, L. Wang, D.; Liu, T.; Li, X.W.; Jiang, W.G.; Zhang, G.; Lou, L.H.

    2015-06-15

    Different amounts of carbon were added to a single-crystal nickel-based superalloy. The microstructural evolution of these alloys before and after high-temperature creep tests was investigated by employing scanning electron microscopy and transmission electron microscopy. Upon increasing the carbon contents, the volume fraction and diameter of the carbides increased gradually: however, the creep lives of the alloys increased slightly at first and subsequently decreased. The formation of second-phase particles, such as the nano-sized M{sub 23}C{sub 6}, blocky and needle-shaped μ phase, was observed in the creep samples, which was closely related to the high-temperature creep behaviors. - Highlights: • Creep behaviors of alloys with different amounts of carbon were investigated. • The creep rupture lives increased and later decreased with more carbon. • Second-phase particles were responsible for the different creep behaviors.

  11. A study of reduced chromium content in a nickel-base superalloy via element substitution and rapid solidification processing. Ph.D. ThesisFinal Report

    NASA Technical Reports Server (NTRS)

    Powers, William O.

    1987-01-01

    A study of reduced chromium content in a nickel base superalloy via element substitution and rapid solidification processing was performed. The two elements used as partial substitutes for chromium were Si and Zr. The microstructure of conventionally solidified materials was characterized using microscopy techniques. These alloys were rapidly solidified using the chill block melt spinning technique and the rapidly solidified microstructures were characterized using electron microscopy. The spinning technique and the rapidly solidified microstructures was assessed following heat treatments at 1033 and 1272 K. Rapidly solidified material of three alloys was reduced to particulate form and consolidated using hot isostatic pressing (HIP). The consolidated materials were also characterized using microscopy techniques. In order to evaluate the relative strengths of the consolidated alloys, compression tests were performed at room temperature and 1033 K on samples of as-HIPed and HIPed plus solution treated material. Yield strength, porosity, and oxidation resistance characteristics are given and compared.

  12. The effects of tantalum on the microstructure of two polycrystalline nickel-base superalloys - B-1900 + Hf and MAR-M247

    NASA Technical Reports Server (NTRS)

    Heckel, R. W.; Pletka, B. J.; Janowski, G. M.

    1986-01-01

    The effect of changing the content of Ta on the gamma/gamma-prime carbide microstructure was investigated in two crystalline nickel-base superalloys: conventionally cast B-1900 + Hf, and both conventionally cast and directionally solidified MAR-M247. The changes occurring in the microstructure effects were similar in both alloys. The gamma-prime and carbide volume fractions increased linearly with Ta additions, while the gamma-prime phase compositions did not change. Bulk Ta additions increased the levels of Cr and Co (in addition to that of Ta) of the gamma phase, a result of the approximately constant partitioning ratios for these two elements. The addition of Ta led to a partial replacement of Hf in the MC carbides. In addition, Cr-rich M(23)C(6) carbides formed as a result of MC carbide decomposition during heat treatment.

  13. The role of the gamma/gamma-prime eutectic and porosity on the tensile behavior of a single-crystal nickel-base superalloy

    NASA Technical Reports Server (NTRS)

    Walston, W. S.; Bernstein, I. M.; Thompson, A. W.

    1991-01-01

    The microstructure of a single-crystal nickel-base superalloy, PWA 1480, has been varied by heat treatment and hot isostatic pressing in order to study the role of the gamma/gamma-prime eutectic and porosity on subsequent tensile behavior. The level of porosity was found not to affect any of the tensile properties, while the gamma/gamma-prime eutectic strongly influenced ductility. Eliminating the gamma/gamma-prime eutectic increased ductility which was attributed to the cleavage fracture of this constituent. It is proposed that such cleavage of the gamma/gamma-prime eutectic is initiated by the stress created from impinging slip bands, promoting shear localization, and final fracture along 111 slip planes. The precise nature of this fracture process is discussed, with emphasis on the role of the gamma/gamma-prime microstructure. The deformation structure of PWA 1480 was also studied, and while different in some respects from many other single-crystal superalloys, its fracture process appears to be similar.

  14. Investigation of the Formation of Topologically Close Packed Phase Instabilities in Nickel-Based Superalloy Rene N6

    NASA Technical Reports Server (NTRS)

    Ritzert, Frank; Keller, Dennis; Vasudevan, Vijay

    1999-01-01

    Topologically close packed (TCP) phase instability in third generation Ni-base superalloys is understood to hinder component performance when used in high-temperature jet engine applications. The detrimental effects on high temperature performance from these brittle phases includes weakening of the Ni-rich matrix through the depletion of potent solid solution strengthening elements. Thirty-four compositional variations of polycrystalline Rene N6 were defined from a design-of-experiments approach and then cast, homogenized, and finally aged to promote TCP formation. Our prior work reported on the results of the multiple retression modeling of these alloys in order to predict the volume fraction of TCP. This paper will present further regression modeling results on these alloys in order to predict the occurrence of TCP in third generation Ni-base superalloy microstructures. Kinetic results are also discussed.

  15. Influence of precipitate morphology on intermediate temperature creep properties of a nickel-base superalloy single crystal

    NASA Technical Reports Server (NTRS)

    Nathal, M. V.; Mackay, R. A.; Miner, R. V.

    1989-01-01

    The relative creep behavior of cuboidal (as-heat treated) and rafted (precrept at 1000 C) gamma-prime microstructures in the single-crystal Ni-based superalloy NASAIR 100 at 760 C was investigated using SEM and TEM examinations of materials at various stages of creep. It was found that, at high applied stresses, the crystals with cuboidal gamma-prime structure had both lower minimum creep rates and longer rupture lives than the crystals with lamellar gamma-prime. At lower stress levels, the initially cuboidal gamma-prime microstructure maintained a lower creep rate, but exhibited a similar rupture life compared to the prerafted crystals.

  16. Hydrogen environment embrittlement of astroloy and Udimet 700 (nickel-base) and V-57 (iron-base) superalloys

    NASA Technical Reports Server (NTRS)

    Gray, H. R.; Joyce, J. P.

    1975-01-01

    The sensitivity to hydrogen environment embrittlement of three superalloys was determined. Astroloy forgings were resistant to embrittlement during smooth tensile, notched tensile, and creep testing in 3.5-MN/sq m hydrogen over the range 23 to 760 C. The notched tensile strength of Udimet 700 bar stock in hydrogen at 23 C was only 50 percent of the baseline value in helium. Forgings of V-57 were not significantly embrittled by hydrogen during smooth tensile testing over the range 23 to 675 C; creep and rupture lives of V-57 were degraded by hydrogen. Postcreep tensile ductility of V-57 was reduced by 40 percent after creep exposure in hydrogen.

  17. The effect of hydrogen and microstructure on the deformation and fracture behavior of a single crystal nickel-base superalloy. Final Report Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Walston, William S.

    1990-01-01

    A study was conducted on the effects of internal hydrogen and microstructure on the deformation and fracture of a single crystal nickel-base superalloy. In particular, room temperature plane strain fracture toughness and tensile tests were performed on hydrogen-free and hydrogen charged samples of PWA 1480. The role of microstructure was incorporated by varying the levels of porosity and eutectic gamma/gamma prime through hot isostatic pressing and heat treatment. The room temperature behavior of PWA 1480 was unusual because precipitate shearing was not the primary deformation mechanism at all strains. At strains over 1 percent, dislocations were trapped in the gamma matrix and an attempt was made to relate this behavior to compositional differences between PWA 1480 and other superalloys. Another unique feature of the tensile behavior was cleavage of the eutectic gamma/gamma prime, which is believed to initiate the failure process. Fracture occurred on (111) planes and is likely a result of shear localization along these planes. Elimination of the eutectic gamma/gamma prime greatly improved the tensile ductility, but pososity had no effect on tensile properties. Large quantities of hydrogen (1.74 at. percent) were gas-phase charged into the material, but surprisingly this was not a function of the amount of porosity or eutectic gamma/gamma prime present. Desorption experiments suggest that the vast majority of hydrogen is at reversible lattice trapping sites. This large, uniform concentration of hydrogen dramatically reduced the tensile strain to failure, but only slightly affected the reduction in area. Available hydrogen embrittlement models were examined in light of these results and it was found that the hydrogen enhanced localized plasticity model can explain much of the tensile behavior. K(IC) fracture toughness tests were conducted, but it was necessary to also perform J(IC) tests to provide valid data.

  18. Polycrystal plasticity modeling of nickel-based superalloy IN 617 subjected to cyclic loading at high temperature

    NASA Astrophysics Data System (ADS)

    Zhang, Xiang; Oskay, Caglar

    2016-06-01

    A crystal plasticity finite element (CPFE) model considering isothermal, large deformation and cyclic loading conditions has been formulated and employed to investigate the mechanical response of a nickel-based alloy at high temperature. The investigations focus on fatigue and creep-fatigue hysteresis response of IN 617 subjected to fatigue and creep-fatigue cycles. A new slip resistance evolution equation is proposed to account for cyclic transient features induced by solute drag creep that occur in IN 617 at 950 °C. The crystal plasticity model parameters are calibrated against the experimental fatigue and creep-fatigue data based on an optimization procedure that relies on a surrogate modeling (i.e. Gaussian process) technique to accelerate multi-parameter optimizations. The model predictions are validated against experimental data, which demonstrates the capability of the proposed model in capturing the hysteresis behavior for various hold times and strain ranges in the context of fatigue and creep-fatigue loading.

  19. Effect of Surface Preparation on the 815°C Oxidation of Single-Crystal Nickel-Based Superalloys

    NASA Astrophysics Data System (ADS)

    Sudbrack, Chantal K.; Beckett, Devon L.; MacKay, Rebecca A.

    2015-11-01

    A primary application for single-crystal superalloys has been jet engine turbine blades, where operation temperatures reach well above 1000°C. The NASA Glenn Research Center is considering use of single-crystal alloys for future, lower temperature application in the rims of jet engine turbine disks. Mechanical and environmental properties required for potential disk rim operation at 815°C are being examined, including the oxidation and corrosion behavior, where there is little documentation at intermediate temperatures. In this study, single-crystal superalloys, LDS-1101+Hf and CMSX-4+Y, were prepared with different surface finishes and compared after isothermal and cyclic oxidation exposures. Surface finish has a clear effect on oxide formation at 815°C. Machined low-stress ground surfaces after exposure for 440 h produce thin Al2O3 external scales, which is consistent with higher temperature oxidation, whereas polished surfaces with a mirror finish yield much thicker NiO external scales with subscale of Cr2O3-spinel-Al2O3, which may offer less reliable oxidation resistance. Additional experiments separate the roles of cold-work, localized deformation, and the extent of polishing and surface roughness on oxide formation.

  20. The effect of hydrogen on the deformation and fracture behavior of a single crystal nickel-base superalloy

    NASA Technical Reports Server (NTRS)

    Walston, W. S.; Thompson, A. W.; Bernstein, I. M.

    1990-01-01

    The room temperature and 300 C tensile behavior of a single crystal superalloy, PWA 1480, has been studied as a function of internal hydrogen concentration and microstructure. Hydrogen is trapped at the porosity and eutectic gamma/gamma in the microstructure, and the effect of these trapping sites on the tensile behavior will be discussed. There is no effect of hydrogen on strength, however, the strain to failure decreases steadily with increasing hydrogen content up to 200 ppm. Cleavage of the eutectic gamma/gamma occurs without hydrogen, but the presence of internal hydrogen causes cracking in the eutectic gamma/gamma at a much earlier stage of deformation leading to a small total strain. In contrast to many superalloys with a high volume fraction of gamma precipitates, there was no evidence of shearing of the gamma, and it was found that at all strains the dislocations are trapped in the gamma matrix. The effect of hydrogen on this behavior and its relation to fracture is described.

  1. High-Frequency Eddy Current Conductivity Spectroscopy for Near-Surface Residual Stress Profiling in Surface-Treated Nickel-Base Superalloys

    SciTech Connect

    Abu-Nabah, Bassam A.; Nagy, Peter B.

    2007-03-21

    Recent research indicated that eddy current conductivity measurements can be exploited for nondestructive evaluation of subsurface residual stress in surface-treated components. This technique is based on the so-called piezoresistive effect, i.e., the stress-dependence of electric conductivity. Previous experimental studies were conducted on excessively peened (Almen 10-16A peening intensity levels) nickel-base superalloy specimens that exhibited harmful cold work in excess of 30% plastic strain. The main reason for choosing peening intensities above recommended normal levels was that the eddy current penetration depth could not be decreased below 0.2 mm without conducting accurate measurements above 10 MHz, which is beyond the operational range of most commercially available eddy current instruments. In this paper we report the development of a new high-frequency eddy current conductivity measuring system that offers an extended inspection frequency range up to 80 MHz with a single probe coil. In addition, the new system offers better reproducibility, accuracy, and measurement speed than the previously used conventional system.

  2. Susceptibility to hot corrosion of four nickel-base superalloys, NASA-TRW VIA, B-1900, 713C and IN-738

    NASA Technical Reports Server (NTRS)

    Stearns, C. A.; Kohl, F. J.; Fryburg, G. C.

    1977-01-01

    The susceptibility to hot corrosion of four nickel-base, cast superalloys has been studied at 900 and 1000 C. The test consisted of coating alloy samples with known amounts of Na2SO4 and oxidizing the coated samples isothermally in 1 atmosphere of slowly flowing oxygen, the weight-gain being monitored on a sensitive recording microbalance. Susceptibility to hot corrosion decreased in the order of decreasing molybdenum content of the alloys. Preoxidation of samples before hot-corrosion testing markedly increased the induction period observed prior to the inception of hot corrosion for all alloys tested. X-ray diffraction analyses of the oxide scales were made. All samples that underwent hot corrosion showed the presence of a (Ni,Co)MoO4 layer near the alloy-oxide interface. Several specimens displayed resistance to hot corrosion and these showed NaTaO3 as a prominent feature in their oxide scale. Our results may be interpreted as indicating that molybdenum in an alloy is detrimental, with respect to hot corrosion, while tantalum is beneficial.

  3. Influence of base alloy composition on processing time during transient liquid phase bonding of nickel-base superalloys

    NASA Astrophysics Data System (ADS)

    Hunedy, Juhaina Farouk

    An experimental investigation to study the influence of base metal composition on the time required to achieve complete isothermal solidification (t f) during TLP bonding of three Ni-base superalloys was performed. Alloys IN 738, DS Rene80 and DS IC 6 show similar behaviour when bonded at 1100 °C, with comparable tf. However, at higher temperatures, IN 738 requires extended period of time (as compared to DS Rene80 and DS IC 6) to achieve complete isothermal solidification. The prolonged tf in IN 738 appears to be caused by a more pronounced reduction in concentration gradient of the diffusing solute within the material during bonding. In contrast, the shorter complete isothermal solidification time experienced by alloy DS IC6 is attributable to its capability to better accommodate the diffusing solute, through the formation of densely packed second-phase precipitates in the diffusion affected zone (DAZ).

  4. The development of gamma-gamma-prime lamellar structures in a nickel-base superalloy during elevated temperature mechanical testing

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Ebert, L. J.

    1985-01-01

    The kinetics of the formation and subsequent development of the directional coarsening of the gamma-prime precipitate in model Ni-Al-Mo-Ta superalloy single crystals are examined during tensile creep under various stress levels at 982 and 1038 C. Special attention is given to the gamma and gamma-prime relation to creep time and strain in order to trace the changing gamma-gamma-prime morphology. Directional coarsening of gamma-prime is found to begin during primary creep and its rate is shown to increase with an increase in temperature or stress level. The length of gamma-prime thickness increased linearly with time up to a plateau reached after the onset of steady state creep. The raft thickness, equal to the gamma-prime size, remained constant at this initial value up through the onset of the tertiary creep. The interlaminar spacing indicates the stability of directionally coarsened structure.

  5. Fracture of single crystals of the nickel-base superalloy PWA 1480E in helium at 22 C

    NASA Technical Reports Server (NTRS)

    Chen, P. S.; Wilcox, R. C.

    1991-01-01

    The fracture behavior and deformation of He-charged (at 22 C) single crystals of PWA 1480E Ni-base superalloy were investigated using SEM and TEM techniques to observe the behavior of tensile fractures in notched single crystals with seven different crystal growth orientations: 100-line, 110-line, 111-line, 013-line, 112-line, 123-line, and 223-line. To identify the cleavage plane orientation, a stereoscopic technique, combined with the use of planar gamma-prime morphologies, was applied. It was found that gamma-prime particles were orderly and closely aligned with edges along the 100-line, 010-line, and 001-line-oriented directions of the gamma matrix. Different crystal growth orientations were found not to affect the morphology of gamma-prime particles. The accumulation of dislocations around gamma/gamma-prime interfaces formed strong barriers to subsequent dislocation movement and was the primary strengthening mechanism at room temperature.

  6. Modeling Long-term Creep Performance for Welded Nickel-base Superalloy Structures for Power Generation Systems

    SciTech Connect

    Shen, Chen

    2015-01-01

    We report here a constitutive model for predicting long-term creep strain evolution in’ strengthened Ni-base superalloys. Dislocation climb-bypassing’, typical in intermediate’ volume fraction (~20%) alloys, is considered as the primary deformation mechanism. Dislocation shearing’ to anti-phase boundary (APB) faults and diffusional creep are also considered for high-stress and high-temperature low-stress conditions, respectively. Additional damage mechanism is taken into account for rapid increase in tertiary creep strain. The model has been applied to Alloy 282, and calibrated in a temperature range of 1375-1450°F, and stress range of 15-45ksi. The model parameters and a MATLAB code are provided. This report is prepared by Monica Soare and Chen Shen at GE Global Research. Technical discussions with Dr. Vito Cedro are greatly appreciated. This work was supported by DOE program DE-FE0005859

  7. The Effect of Solution Heat Treatment on an Advanced Nickel-Base Disk Alloy

    NASA Technical Reports Server (NTRS)

    Gayda, J.; Gabb, T. P.; Kantzos, P. T.

    2004-01-01

    Five heat treat options for an advanced nickel-base disk alloy, LSHR, have been investigated. These included two conventional solution heat treat cycles, subsolvus/oil quench and supersolvus/fan cool, which yield fine grain and coarse grain microstructure disks respectively, as well as three advanced dual microstructure heat treat (DMHT) options. The DMHT options produce disks with a fine grain bore and a coarse grain rim. Based on an overall evaluation of the mechanical property data, it was evident that the three DMHT options achieved a desirable balance of properties in comparison to the conventional solution heat treatments for the LSHR alloy. However, one of the DMHT options, SUB/DMHT, produced the best set of properties, largely based on dwell crack growth data. Further evaluation of the SUB/DMHT option in spin pit experiments on a generic disk shape demonstrated the advantages and reliability of a dual grain structure at the component level.

  8. Determination of solute site occupancies within γ' precipitates in nickel-base superalloys via orientation-specific atom probe tomography

    SciTech Connect

    Meher, Subhashish; Rojhirunsakool, Tanaporn; Nandwana, Peeyush; Tiley, Jamie; Banerjee, Rajarshi

    2015-04-28

    In this study, the analytical limitations in atom probe tomography such as resolving a desired set of atomic planes, for solving complex materials science problems, have been overcome by employing a well-developed unique and reproducible crystallographic technique, involving synergetic coupling of orientation microscopy with atom probe tomography. The crystallographic information in atom probe reconstructions has been utilized to determine the solute site occupancies in Ni-Al-Cr based superalloys accurately. The structural information in atom probe reveals that both Al and Cr occupy the same sub-lattice within the L12-ordered g precipitates to form Ni3(Al,Cr) precipitates in a Ni-14Al-7Cr(at.%) alloy. Interestingly, the addition of Co, which is a solid solution strengthener, to a Ni-14Al-7Cr alloy results in the partial reversal of Al site occupancy within g precipitates to form (Ni,Al)3(Al,Cr,Co) precipitates. This unique evidence of reversal of Al site occupancy, resulting from the introduction of other solutes within the ordered structures, gives insights into the relative energetics of different sub-lattice sites when occupied by different solutes.

  9. Determination of solute site occupancies within γ' precipitates in nickel-base superalloys via orientation-specific atom probe tomography

    DOE PAGES

    Meher, Subhashish; Rojhirunsakool, Tanaporn; Nandwana, Peeyush; Tiley, Jamie; Banerjee, Rajarshi

    2015-04-28

    In this study, the analytical limitations in atom probe tomography such as resolving a desired set of atomic planes, for solving complex materials science problems, have been overcome by employing a well-developed unique and reproducible crystallographic technique, involving synergetic coupling of orientation microscopy with atom probe tomography. The crystallographic information in atom probe reconstructions has been utilized to determine the solute site occupancies in Ni-Al-Cr based superalloys accurately. The structural information in atom probe reveals that both Al and Cr occupy the same sub-lattice within the L12-ordered g precipitates to form Ni3(Al,Cr) precipitates in a Ni-14Al-7Cr(at.%) alloy. Interestingly, the additionmore » of Co, which is a solid solution strengthener, to a Ni-14Al-7Cr alloy results in the partial reversal of Al site occupancy within g precipitates to form (Ni,Al)3(Al,Cr,Co) precipitates. This unique evidence of reversal of Al site occupancy, resulting from the introduction of other solutes within the ordered structures, gives insights into the relative energetics of different sub-lattice sites when occupied by different solutes.« less

  10. Production of Al-Co-Ni Ternary Alloys by the SHS Method for Use in Nickel Based Superalloys Manufacturing

    NASA Astrophysics Data System (ADS)

    Alkan, Murat; Sonmez, M. Seref; Derin, Bora; Yücel, Onuralp; Andreev, Dmitrii E.; Sanin, Vladimir N.; Yukhvid, Vladimir I.

    2015-05-01

    In this study, Al-Co-Ni ternary alloys were synthesized, in order to obtain low-cost starting material for Ni-based superalloy production, by a self-propagating high temperature synthesis (SHS) both under normal gravity conditions (a = 9.81 m/s2) and under high gravity conditions (up to 1000 g-force) by using a centrifugal machine. The mixture of Co3O4-NiO powder were reduced by Al powder for the production of SHS alloys with the estimated compositions of 5-10 mass% Al, 20-65 mass% Co, 25-75 mass% Ni. The effect of green mixture compositions and centrifugal overload on combustion temperature, alloy/slag separations, chemical composition and microstructure of final alloys were investigated. The chemical analysis results showed that production of SHS alloys were achieved by having up to 86.12% of Co and 92.32% of Ni recoveries. The highest metal recovery value was obtained in SHS alloy with the estimated composition of 10%Al-65%Co-25%Ni by the addition of 20% Al2O3 into the green mixture. The metal/slag separation efficiency increased by increasing the centrifugal overload.

  11. Determination of solute site occupancies within γ' precipitates in nickel-base superalloys via orientation-specific atom probe tomography.

    PubMed

    Meher, S; Rojhirunsakool, T; Nandwana, P; Tiley, J; Banerjee, R

    2015-12-01

    The analytical limitations in atom probe tomography such as resolving a desired set of atomic planes, for solving complex materials science problems, have been overcome by employing a well-developed unique and reproducible crystallographic technique, involving synergetic coupling of orientation microscopy with atom probe tomography. The crystallographic information in atom probe reconstructions has been utilized to determine the solute site occupancies in Ni-Al-Cr based superalloys accurately. The structural information in atom probe reveals that both Al and Cr occupy the same sub-lattice within the L12-ordered γ' precipitates to form Ni3(Al,Cr) precipitates in a Ni-14Al-7Cr (at%) alloy. Interestingly, the addition of Co, which is a solid solution strengthener, to a Ni-14Al-7Cr alloy results in the partial reversal of Al site occupancy within γ' precipitates to form (Ni,Al)3(Al,Cr,Co) precipitates. This unique evidence of reversal of Al site occupancy, resulting from the introduction of other solutes within the ordered structures, gives insights into the relative energetics of different sub-lattice sites when occupied by different solutes.

  12. Factors which influence directional coarsening of Gamma prime during creep in nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Ebert, L. J.

    1984-01-01

    Changes in the morphology of the gamma prime precipitate were examined as a function of time during creep at 982 C in 001 oriented single crystals of a Ni-Al-Mo-Ta superalloy. In this alloy, which has a large negative misfit of -0.80 pct., the gamma prime particles link together during creep to form platelets, or rafts, which are aligned with their broad faces perpendicular to the applied tensile axis. The effects of initial microstructure and alloy composition of raft development and creep properties were investigated. Directional coarsening of gamma prime begins during primary creep and continues well after the onset of second state creep. The thickness of the rafts remains constant up through the onset of tertiary creep a clear indication of the stability of the finely-spaced gamma/gamma prime lamellar structure. The thickness of the rafts which formed was equal to the initial gamma prime size which was present prior to testing. The single crystals with the finest gamma prime size exhibited the longest creep lives, because the resultant rafted structure had a larger number of gamma/gamma prime interfaces per unit volume of material. Reducing the Mo content by only 0.73 wt. pct. increased the creep life by a factor of three, because the precipitation of a third phase was eliminated.

  13. Factors which influence directional coarsening of gamma-prime during creep in nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Ebert, L. J.

    1984-01-01

    Changes in the morphology of the gamma prime precipitate were examined as a function of the time during creep at 982 C in 001 oriented single crystals of a Ni-Al-Mo-Ta superalloy. In this alloy, which has a large negative misfit of -0.80 pct., the gamma prime particles link together during creep to form platelets, or rafts, which are aligned with their broad faces perpendicular to the applied tensile axis. The effects of initial microstructure and alloy composition of raft development and creep properties were investigated. Directional coarsening of gamma prime begins during primary creep and continues well after the onset of second state creep. The thickness of the rafts remains constant up through the onset of tertiary creep, a clear indication of the stability of the finely-spaced gamma/gamma prime lamellar structure. The thickness of the rafts which formed was equal to the initial gamma prime size which was present prior to testing. The single crystals with the finest gamma prime size exhibited the longest creep lives, because the resultant rafted structure had a larger number of gamma/gamma prime interfaces per unit volume of material. Reducing the Mo content by only 0.73 wt. pct. increased the creep life by a factor of three, because the precipitation of a third phase was eliminated.

  14. Detailed Analysis of the Solution Heat Treatment of a Third-Generation Single-Crystal Nickel-Based Superalloy CMSX-10K®

    NASA Astrophysics Data System (ADS)

    Pang, Hon Tong; D'Souza, Neil; Dong, Hongbiao; Stone, Howard J.; Rae, Catherine M. F.

    2016-02-01

    A detailed analysis of the response of as-cast third-generation single-crystal nickel-based superalloy CMSX-10K® to solution heat treatment (SHT) has been carried out, alongside an SHT optimization exercise. The analysis was conducted through microstructural characterization, differential scanning calorimetry, and compositional homogeneity measurements, quantifying (i) the dissolution and microstructural evolution of the inter-dendritic constituents, (ii) the shift in thermo-physical characteristics of the material, and (iii) the change in compositional homogeneity across the microstructure, in order to gain further understanding of these phenomena during the progression of the SHT. During the early stages of SHT, the coarse cellular γ'/narrow γ channel inter-dendritic constituents which were the last areas to solidify during casting, progressively dissolve; homogenization between these inter-dendritic areas and adjacent dendritic areas leads to a rapid increase in the incipient melting temperature T IM. The fine γ/γ' morphology which were the first inter-dendritic constituents to solidify after primary γ dendrite solidification were found to progressively coarsen; however, subsequent dissolution of these coarsened γ/γ' inter-dendritic areas did not result in significant increases in the T IM until the near-complete dissolution of these inter-dendritic areas. After the final SHT step, residual compositional micro-segregation could still be detected across the microstructure despite the near-complete dissolution of these remnant inter-dendritic areas; even so the T IM of the material approached the solidus temperature of the alloy.

  15. Multiscale study of the boron and carbon behavior in the fracture zone of the rapidly quenched nickel-based superalloy by the nuclear physics methods of the track and activation autoradiography

    NASA Astrophysics Data System (ADS)

    Shulga, A. V.

    2016-04-01

    The results of the study of the fracture zone of the rapidly quenched nickel-based superalloy after tensile tests are presented. The main attention was attended to the multiscale investigation of boron and carbon distribution in the area of the cracks propagation by the direct nuclear physics methods of the track and activation autoradiography. Tensile tests were performed at the temperatures up to 1150 °C. The nuclear reactor MEPhI IRT-2000 and cyclotron were applied for the autoradiography studies. Significant depleting of boron in the fracture zone which was revealed can be explained due to the intensive moving of the dislocation.

  16. Phase chemistry of nickel-base superalloy after creep experiments. [66. 7 Ni, 12. 0 Al, 2. 8 Ti, 0. 9 Ta, 9. 6 Cr, 5. 0 Co, 3. 0 W

    SciTech Connect

    Schmidt, R.; Feller-Kniepmeier, M. . Inst. fur Metallforschung)

    1993-10-15

    The formation of rafts by the ordered [gamma]-phase under a tensile load at high temperatures is one of the most interesting features of nickel-base superalloys. It has been investigated by many authors, both theoretically and experimentally. From elasto-plastic finite-element calculations of it is known that matrix channels depending on their orientation to the load axis experience quite different stress levels. In order to determine the influence of these different stress levels on phase chemistry and phase growth, in this work the phase compositions of the single crystal superalloy SRR99 have been analyzed after creep experiments at T = 980 C and T = 760 C in [001] direction.

  17. Analyses of Elemental Partitioning in Advanced Nickel-Base Superalloy Single Crystals

    NASA Technical Reports Server (NTRS)

    Dreshfield, Robert L.; Thomas, Kimberly J.

    2005-01-01

    Aircraft propulsion engines for the High Speed Civil Transport which may be developed early in the 21st century will require significantly different durability requirements than those which currently power civil aircraft. The durability will be more difficult to achieve because it is expected that the new aircraft engines will have to operate at near maximum power for more than half of each flight compared to 5 to 10 percent for typical current aircraft. To meet this requirement, a team of NASA, Pratt & Whitney Aircraft, and General Electric personnel have been formed to develop an appropriate alloy for the mission. This report summarizes the work performed by a part of that team up to the retirement of one of its members, R.L. Dreshfield. The prime purpose of the report is to assemble the data obtained in a single document so that it may be more accessible to those who may wish to pursue it at a later date.

  18. The correlation between the temperature dependence of the CRSS and the formation of superlattice-intrinsic stacking faults in the nickel-base superalloy PWA 1480. [critical resolved shear stress

    NASA Technical Reports Server (NTRS)

    Milligan, Walter W.; Antolovich, Stephen D.

    1989-01-01

    The PWA 1480 nickel-base superalloy is known to exhibit a unique minimum in the critical resolved shear stress (CRSS) at about 400 C. This paper reports an observation of a deformation mechanism whose temperature dependence correlates exactly with the reduction in the CRSS. It was found that, after monotonic or cyclic deformation of PWA 1480 at 20 C, the deformation substructures typically contain high density of superlattice-intrinsic stacking faults (S-ISFs) within the gamma-prime precipitates. As the temperature of deformation is increased, the density of S-ISFs is reduced, until finally no faults are observed after deformation in the range from 400 to 705 C. The reduction in the fault density corresponds exactly to the reduction in the CRSS, and the temperature at which the fault density is zero corresponds with the minimum in the CRRS. Two possible mechanisms related to the presence of the S-ISFs in the alloy are considered.

  19. An Evaluation of the Use of X-ray Residual Stress Determination as a Means of Characterizing Oxidation Damage of Nickel-Based, Cr2O3-Forming Superalloys Subjected to Various Oxidizing Condition

    SciTech Connect

    Barnard, Bryan R; Watkins, Thomas R; Liaw, Peter K

    2010-01-01

    The use of X-ray residual stress determination as a technique for evaluating the damage incurred by nickel-based, Cr2O3-forming superalloy materials under various service conditions (isothermal heating, thermal cycling, applied stress, stressed and cycled) was investigated. Large and small compressive residual stresses were observed for the oxides and the near surface substrates, respectively. It was expected that the applied stresses and thermal cycling would cause an enhanced degree of oxidation damage that would translate into appreciable differences in residual stress values. Differences in the magnitude of residual stress values were not appreciable condition-to-condition, however. An increase in the severity of the oxidizing conditions in the form of longer oxidation times, higher oxidizing temperatures, and a much greater frequency of thermal cycling is suggested for future studies.

  20. Oxidation in oxygen at 900 deg and 1000 deg C of four nickel-base cast superalloys: NASA-TRW VIA, B-1900, alloy 713C, and IN-738

    NASA Technical Reports Server (NTRS)

    Fryburg, G. C.; Kohl, F. J.; Stearns, C. A.

    1977-01-01

    The oxidation at 900 and 1,000 C of four nickel-base superalloys in 1 atmosphere of slowly flowing oxygen was investigated. Thermogravimetric rate data were obtained for periods to 100 hours. The morphology and composition of the oxide scales formed after 100 hours were studied by optical microscopy, X-ray diffraction, electron microprobe, scanning electron microscopy, and X-ray photoelectron spectroscopy (ESCA). Alloys B-1900 and VIA were found to be primarily alumina formers, though probably 25 percent of their surface was covered by CR2O3-containing oxides at 900 C. Alloys 713C and IN-738 were primarily chromia formers, though the surface of 713C at 1,000 C was covered with NiO, and the surface of IN-738 at both temperatures was covered with a thin layer of TiO2.

  1. Microstructure and stress-rupture life of polycrystal, directionally solidified, and single crystal castings of nickel-based IN 939 superalloy

    SciTech Connect

    Jovanovic, M.T.; Miskovic, Z.; Lukic, B.

    1998-04-01

    A comparative investigation of microstructural and mechanical properties (stress-rupture life) in conventionally cast, directionally solidified, and single crystal IN 939 superalloy has been undertaken. Directional castings possess only a few columnar grains, all oriented in the <100> crystallographic direction, whereas only one grain is present in a single crystal. Single crystals are characterized by the highest values of stress-rupture life, much higher than those of directionally solidified and, especially, polycrystal castings, which is accounted for by the absence of grain boundaries.

  2. The influence of high thermal gradient casting, hot isostatic pressing and alternate heat treatment on the structure and properties of a single crystal nickel base superalloy

    NASA Technical Reports Server (NTRS)

    Fritzemeier, L. G.

    1988-01-01

    A development program has been conducted to improve the cyclic properties of the PWA 1480 single-crystal superalloy by reducing or entirely eliminating casting porosity at fatigue-initiation sites, through the use of improved casting process parameters and HIPing; potential mechanical property improvements in a high-pressure hydrogen environment were also sought in alternatives to the standard coating and heat-treatment cycle. High thermal gradient casting was found to yield a reduction in overall casting porosity density and pore sizes. The most dramatic mechanical property improvement resulted from HIPing.

  3. Subsurface characterization of an oxidation-induced phase transformation and twinning in nickel-based superalloy exposed to oxy-combustion environments

    SciTech Connect

    Zhu, Jingxi; Holcomb, Gordon R.; Jablonski, Paul D.; Wise, Adam; Li, Jia; Laughlin, David E.; Sridhar, Seetharaman

    2012-07-30

    In the integration of oxy-fuel combustion to turbine power generation system, turbine alloys are exposed to high temperature and an atmosphere comprised of steam, CO{sub 2} and O{sub 2}. While surface and internal oxidation of the alloy takes place, the microstructure in the subsurface region also changes due to oxidation. In this study, bare metal coupons of Ni-base superalloys were exposed in oxy-fuel combustion environment for up to 1000 h and the oxidation-related microstructures were examined. Phase transformation occurred in the subsurface region in Ni-based superalloy and led to twinning. The transformation product phases were analyzed through thermodynamic equilibrium calculations and various electron microscopy techniques, including scanning electron microscopy (SEM), orientation imaging microscopy (OIM) and transmission electron microscopy (TEM). The mechanism by which the phase transformation and the formation of the microstructure occurred was also discussed. The possible effects of the product phases on the performance of the alloy in service were discussed.

  4. Orientation and temperature dependence of some mechanical properties of the single-crystal nickel-base superalloy Rene N4. 3: Tension-compression anisotropy

    NASA Technical Reports Server (NTRS)

    Miner, R. V.; Gaab, T. P.; Gayda, J.; Hemker, K. J.

    1985-01-01

    Single crystal superalloy specimens with various crystallographic directions along their axes were tested in compression at room temperature, 650, 760, 870, and 980 deg C. These results are compared with the tensile behavior studied previously. The alloy, Rene N4, was developed for gas turbine engine blades and has the nominal composition 3.7 Al, 4.2 Ti, 4 Ta, 0.5 Nb, 6 W, 1.5 Mo 9 Cr. 7.5 Co, balance Ni, in weight percent. Slip trace analysis showed that primary cube slip occurred even at room temperature for the 111 specimens. With increasing test temperature more orientations exhibited primary cube slip, until at 870 deg C only the 100 and 011 specimens exhibited normal octahedral slip. The yield strength for octahedral slip was numerically analysed using a model proposed by Lall, Chin, and Pope to explain deviations from Schmid's Law in the yielding behavior of a single phase Gamma prime alloy, Ni3(Al, Nb). The Schmid's Law deviations in Rene N4 were found to be largely due to a tension-compression anisotropy. A second effect, which increases trength for orientations away from 001, was found to be small in Rene N4. Analysis of recently published data on the single crystal superalloy PWA 1480 yielded the same result.

  5. Mechanism of Na2SO4-induced corrosion of molybdenum containing nickel-base superalloys at high temperatures. I - Corrosion in atmospheres containing O2 only. II - Corrosion in O2 + SO2 atmospheres

    NASA Technical Reports Server (NTRS)

    Misra, A. K.

    1986-01-01

    Kinetics of the Na2SO4-induced corrosion of the molybdenum-containing nickel-base superalloys, B-1900 and Udimet 700, coated with Na2MoO4, has been studied in oxygen atmosphere at temperatures ranging from 750 to 950 C. Because the gas turbine atmosphere always contains some SO2 and SO3, the effect of atmospheric SO2 content on corrosion of Udimet-700 has also been studied. It was found that in the O2 atmosphere the melt in the catastrophic corrosion phase consists of Na2MoO4 plus MoO3, with the onset of the catastrophic corrosion coinciding with the appearance of MoO3. In the presence of low levels of atmospheric SO2 (below 0.24 percent), the melt during catastrophic corrosion contains, in addition to Na2MoO4 and MoO3, some quantities of Na2SO4. At the levels of SO2 above 1 percent, no catastrophic corrosion was observed. At these SO2 levels, internal sulfidation appears to be the primary mode of degradation.

  6. Measurement of gamma' precipitates in a nickel-based superalloy using energy-filtered transmission electron microscopy coupled with automated segmenting techniques.

    PubMed

    Tiley, J S; Viswanathan, G B; Shiveley, A; Tschopp, M; Srinivasan, R; Banerjee, R; Fraser, H L

    2010-08-01

    Precipitates of the ordered L1(2) gamma' phase (dispersed in the face-centered cubic or FCC gamma matrix) were imaged in Rene 88 DT, a commercial multicomponent Ni-based superalloy, using energy-filtered transmission electron microscopy (EFTEM). Imaging was performed using the Cr, Co, Ni, Ti and Al elemental L-absorption edges in the energy loss spectrum. Manual and automated segmentation procedures were utilized for identification of precipitate boundaries and measurement of precipitate sizes. The automated region growing technique for precipitate identification in images was determined to measure accurately precipitate diameters. In addition, the region growing technique provided a repeatable method for optimizing segmentation techniques for varying EFTEM conditions. PMID:20434346

  7. Measurement of gamma' precipitates in a nickel-based superalloy using energy-filtered transmission electron microscopy coupled with automated segmenting techniques.

    PubMed

    Tiley, J S; Viswanathan, G B; Shiveley, A; Tschopp, M; Srinivasan, R; Banerjee, R; Fraser, H L

    2010-08-01

    Precipitates of the ordered L1(2) gamma' phase (dispersed in the face-centered cubic or FCC gamma matrix) were imaged in Rene 88 DT, a commercial multicomponent Ni-based superalloy, using energy-filtered transmission electron microscopy (EFTEM). Imaging was performed using the Cr, Co, Ni, Ti and Al elemental L-absorption edges in the energy loss spectrum. Manual and automated segmentation procedures were utilized for identification of precipitate boundaries and measurement of precipitate sizes. The automated region growing technique for precipitate identification in images was determined to measure accurately precipitate diameters. In addition, the region growing technique provided a repeatable method for optimizing segmentation techniques for varying EFTEM conditions.

  8. The Effect of Stabilization Heat Treatments on the Tensile and Creep Behavior of an Advanced Nickel-Based Disk Alloy

    NASA Technical Reports Server (NTRS)

    Gayda, John

    2003-01-01

    As part of NASA s Advanced Subsonic Technology Program, a study of stabilization heat treatment options for an advanced nickel-base disk alloy, ME 209, was performed. Using a simple, physically based approach, the effect of stabilization heat treatments on tensile and creep properties was analyzed in this paper. Solutions temperature, solution cooling rate, and stabilization temperature/time were found to have a significant impact on tensile and creep properties. These effects were readily quantified using the following methodology. First, the effect of solution cooling rate was assessed to determine its impact on a given property. The as-cooled property was then modified by using two multiplicative factors which assess the impact of solution temperature and stabilization parameters. Comparison of experimental data with predicted values showed this physically based analysis produced good results that rivaled the statistical analysis employed, which required numerous changes in the form of the regression equation depending on the property and temperature in question. As this physically based analysis uses the data for input, it should be noted that predictions which attempt to extrapolate beyond the bounds of the data must be viewed with skepticism. Future work aimed at expanding the range of the stabilization/aging parameters explored in this study would be highly desirable, especially at the higher solution cooling rates.

  9. Effects of alloy composition on cyclic flame hot-corrosion attack of cast nickel-base superalloys at 900 deg C

    NASA Technical Reports Server (NTRS)

    Deadmore, D. L.

    1984-01-01

    The effects of Cr, Al, Ti, Mo, Ta, Nb, and W content on the hot corrosion of nickel base alloys were investigated. The alloys were tested in a Mach 0.3 flame with 0.5 ppmw sodium at a temperature of 900 C. One nondestructive and three destructive tests were conducted. The best corrosion resistance was achieved when the Cr content was 12 wt %. However, some lower-Cr-content alloys ( 10 wt%) exhibited reasonable resistance provided that the Al content alloys ( 10 wt %) exhibited reasonable resistance provided that the Al content was 2.5 wt % and the Ti content was Aa wt %. The effect of W, Ta, Mo, and Nb contents on the hot-corrosion resistance varied depending on the Al and Ti contents. Several commercial alloy compositions were also tested and the corrosion attack was measured. Predicted attack was calculated for these alloys from derived regression equations and was in reasonable agreement with that experimentally measured. The regression equations were derived from measurements made on alloys in a one-quarter replicate of a 2(7) statistical design alloy composition experiment. These regression equations represent a simple linear model and are only a very preliminary analysis of the data needed to provide insights into the experimental method.

  10. Morphological changes of gamma prime precipitates in nickel-base superalloy single crystals. Ph.D. Thesis - Case Western Reserve Univ., May 1984

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.

    1984-01-01

    Changes in the morphology of the gamma prime precipitate were examined during tensile creep at temperatures between 927 and 1038 C in 001-oriented single crystals of a Ni-Al-Mo-Ta superalloy. In this alloy, which has a large negative misfit of -0.80%, the gamma prime particles link together during creep to form platelets, or rafts, which are aligned with their broad faces perpendicular to the applied tensile axis. The dimensions of the gamma and gamma prime phases were measured as directional coarsening developed in an attempt to trace the changing morphology under various stress levels. In addition, the effects of initial microstructure, as well as slight compositional variations, were related to raft development and creep properties. The results showed that directional coarsening of gamma prime began during primary creep, and under certain conditions, continued to develop after the onset of steady-state creep. The length of the rafts increased linearly with time up to a plateau region. The thickness of the rafts, however, remained equal to the initial gamma prime size at least up through the onset of tertiary creep; this is a clear indication of the stability of the finely-spaced gamma-gamma prime lamellar structure. It was found that the single crystals with the finest gamma prime size exhibited the longest creep lives, because the resultant rafted structure had a larger number of gamma-gamma prime interfaces per unit volume of material.

  11. Effects of Jet Pressure on the Ground Surface Quality and CBN Wheel Wear in Grinding AISI 690 Nickel-Based Superalloy

    NASA Astrophysics Data System (ADS)

    Guitouni, Ahmed; Chaieb, Iheb; Rhouma, Amir Ben; Fredj, Nabil Ben

    2016-09-01

    Fluid application in grinding is getting attention as higher stock removal rates, higher surface integrity and longer wheel life are required. It is necessary to define proper conditions of application for meeting high productivity goals by lowering the specific grinding energy and reducing the temperature of the contact zone. The present study investigated the capacity of the jet pressure of a spot nozzle to improve the wear of a CBN wheel when grinding the AISI 690 superalloy. Grinding experiments were conducted with an emulsion-type cooling fluid delivered at pressure ranging from 0.1 to 4 MPa. Results show that the maximum stock removal, reached at 4 MPa, is 5 times the stock removal obtained at 0.1 MPa, while the grinding ratio at 4 MPa is 8 times that at 0.1 MPa, and there is a critical pressure (P c) around 1.5 MPa corresponding to the minimum specific grinding energy. Scanning electron microscopy of the grain tips showed that the wear mechanism shifts from breaking and dislodgment at low jet pressure to micro-fracture resulting in continuous self-sharpening of the abrasive grains. By lubricating at jet pressure close to P c, there is less thermal damage due to plowing and sliding and the resulting lower loading of the abrasive grains favors the micro-fracture of grains and thus a longer wheel life.

  12. Elevated temperature mechanical behavior of new low CTE superalloys

    SciTech Connect

    Cowen, C.J.; Jablonski, P.D.

    2008-09-01

    This paper presents the high temperature mechanical properties of several experimental low coefficient of thermal expansion (CTE) alloys. The use of such alloys facilitate the extension of advanced ferritic stainless steels to higher use temperature in advanced power generation systems. We find that one of these alloys, J5 appears to be favorable for bridging ferritic alloys (operating up to ~600°C) to traditional nickel based superalloys (operating at 750°C).

  13. The key role of dislocation dissociation in the plastic behaviour of single crystal nickel-based superalloy with low stacking fault energy: Three-dimensional discrete dislocation dynamics modelling

    NASA Astrophysics Data System (ADS)

    Huang, Minsheng; Li, Zhenhuan

    2013-12-01

    To model the deformation of single crystal nickel based superalloys (SCNBS) with low stacking fault energy (SFE), three-dimensional discrete dislocation dynamics (3D-DDD) is extended by incorporating dislocation dissociation mechanism. The present 3D-DDD simulations show that, consistent with the existing TEM observation, the leading partial can enter the matrix channel efficiently while the trailing partial can hardly glide into it when the dislocation dissociation is taken into account. To determine whether the dislocation dissociation can occur or not, a critical percolation stress (CPS) based criterion is suggested. According to this CPS criterion, for SCNBS there exists a critical matrix channel width. When the channel width is lower than this critical value, the dislocation tends to dissociate into an extended configuration and vice versa. To clarify the influence of dislocation dissociation on CPS, the classical Orowan formula is improved by incorporating the SFE. Moreover, the present 3D-DDD simulations also show that the yielding stress of SCNBSs with low SFE may be overestimated up to 30% if the dislocation dissociation is ignored. With dislocation dissociation being considered, the size effect due to the width of γ matrix channel and the length of γ‧ precipitates on the stress-strain responses of SCNBS can be enhanced remarkably. In addition, due to the strong constraint effect by the two-phase microstructure in SCNBS, the configuration of formed junctions is quite different from that in single phase crystals such as Cu. The present results not only provide clear understanding of the two-phase microstructure levelled microplastic mechanisms in SCNBSs with low SFE, but also help to develop new continuum-levelled constitutive laws for SCNBSs.

  14. Perspectives on radiation effects in nickel-base alloys for applications in advanced reactors

    NASA Astrophysics Data System (ADS)

    Rowcliffe, A. F.; Mansur, L. K.; Hoelzer, D. T.; Nanstad, R. K.

    2009-07-01

    Because of their superior high temperature strength and corrosion properties, a set of Ni-base alloys has been proposed for various in-core applications in Gen IV reactor systems. However, irradiation-performance data for these alloys is either limited or non-existent. A review is presented of the irradiation-performance of a group of Ni-base alloys based upon data from fast breeder reactor programs conducted in the 1975-1985 timeframe with emphasis on the mechanisms involved in the loss of high temperature ductility and the breakdown in swelling resistance with increasing neutron dose. The implications of these data for the performance of the Gen IV Ni-base alloys are discussed and possible pathways to mitigate the effects of irradiation on alloy performance are outlined. A radical approach to designing radiation damage-resistant Ni alloys based upon recent advances in mechanical alloying is also described.

  15. A lifetime-prediction approach to understanding corrosion: The corrosion-fatigue and corrosion behavior of a nickel-based superalloy and a nanocrystalline alloy

    NASA Astrophysics Data System (ADS)

    Steward, Rejanah Vernice

    Lifetime-prediction models are useful for simulating a material's in-service behavior or outcome. Perhaps the greatest advantage of these models is the ability to use the predicted results to help optimize engineering designs and reduce costs. The HastelloyRTM C-2000RTM superalloy is a single-phase material and face-centered cubic in structure at all temperatures. The C-2000RTM alloy is a commercially designed alloy manufactured to function in both reducing and oxidizing solutions. C-2000RTM is used as a fabrication material for heat exchangers, piping for chemical refineries, and storage repositories. The corrosion properties of C-2000RTM are excellent, and the ductility and fatigue properties are good. In this study, C-2000RTM is used to verify the theoretical basis of an electrochemical-micromechanical crack-initiation corrosion-fatigue model for materials under passive electrochemical conditions. The results from electrochemical and mechanical experiments, along with the findings from the conventional electron microscopy and a laser interferometer will be presented. A nanocrystalline Ni-18 weight percent (wt.%) Fe alloy is examined to investigate its electrochemical behavior in a 3.5 wt.% NaCl solution. Three Ni-18 wt.% Fe samples were annealed at 400°C for 3, 8, and 24 hours (hrs.) to study the effects of grain sizes on the electrochemical properties of bulk Ni-18 wt.% Fe. The electrochemical results from the annealed samples are compared with those measured for the as-received Ni-18 wt.% Fe material consisting of an average grain size of 23 nanometers (nm). The samples annealed for times longer than 8 hrs. appear to have undergone an abnormal grain growth, where nanometer and micrometer (mum) grain sizes are present. Unlike the electrochemical results for the as-received material, the annealed nanocrystalline materials appear to be susceptible to localized corrosion. Consequently, these larger grains within the nanoncrystalline-grain matrix are

  16. On the dissolution mechanisms of [gamma][prime] precipitates in nickel-base superalloys. [Ni-7. 5Cr-5. 5W-8Ta-5. 3Al-6. 5Co-1. 2Ti-2Mo and Ni-8Cr-8W-6Ta-5. 6Al-4. 6Co-1Ti-0. 6Mo

    SciTech Connect

    Grosdidier, T.; Hazotte, A.; Simon, A. . Lab. de Science et Genie des Materiaux Metalliques)

    1994-05-15

    The strengthening of nickel-based superalloys is mainly obtained by the coherent precipitation of a large amount of the Ni[sub 3]Al type [gamma][prime] phase in a nickel based [gamma] matrix. Although many studies have shown the importance of the [gamma][prime] phase morphology and size on the mechanical behavior of Ni-based superalloys, little work has concentrated on the high temperature [gamma] + [gamma][prime] <=> [gamma] phase transformation domain where large [gamma][prime] volume fraction and shape changes are experienced. In particular, the dissolution of the [gamma][prime] precipitates which can occur under overheating'' of the material during its service life has received little attention. Lee et al, have proposed that dissolution of the [gamma][prime] phase could occur by the splitting of the [gamma][prime] precipitates from the interface. The present paper deals with the own observations of the structural evolution of the [gamma][prime] phase during dissolution and a discussion of the mechanisms involved.

  17. Superalloy material with improved weldability

    SciTech Connect

    Allen, David B.; Wagner, Gregg P.; Seth, Brij B.

    2004-02-24

    A fusion weldable superalloy containing 0.005-0.5 wt. % scandium. In one embodiment, the superalloy may have a composition similar to IN-939 alloy, but having added scandium and having only 0.005-0.040 wt. % zirconium. A gas turbine component may be formed by an investment casting of such a scandium-containing superalloy, and may include a fusion weld repaired area. A scandium-containing nickel-based superalloy coated with an MCrAlY bond coat will have improved cyclic oxidation resistance due to the sulfur-gettering effect of the scandium.

  18. Analysis of interfacial dislocations in a single crystal nickel-base superalloy after [001] creep at 1,033 K evolution of internal stresses. [Ni-5. 5Al-2. 2Ti-8. 5Cr-5. 0Co-2. 8Ta-9. 5W-0. 018C

    SciTech Connect

    Feller-Kniepmeier, M.; Hemmersmeier, U.; Kuttner, T.; Link, T. . Inst. fuer Metallforschung)

    1994-05-15

    Single crystal Nickel-base superalloys are composite consisting of high volume fractions of the ordered L1[sub 2] [gamma][prime] phase embedded in the fcc matrix. Due to the misfit between the two phases, coherency stresses arise in the microstructure. FEM calculations of the principal stress distributions have shown that the narrow matrix channels are highly loaded in compression parallel to the [gamma]/[gamma][prime] interfaces, while tensile stresses perpendicular to the interfaces are small. The interior of the [gamma][prime] cube is under low tensile stress. In the present paper the authors are interested in the evolution of interfacial dislocations at the early stages of creep and at medium temperature where diffusion effects can be neglected. The interfacial dislocations are used for an experimental check of the micromechanical and the crystallographic model.

  19. Secondary orientation effects in a single crystal superalloy under mechanical and thermal loads

    NASA Technical Reports Server (NTRS)

    Kalluri, Sreeramesh; Abdul-Aziz, Ali; Mcgaw, Michael A.

    1991-01-01

    The nickel-base single crystal superalloy PWA 1480 is a candidate blading material for the advanced turbopump development program of the SSME. In order to improve thermal fatigue resistance of the turbine blades, the single crystal superalloy PWA 1480 is grown along the low modulus zone axes (001) crystal orientation by a directional solidification process. Since cubic single crystal materials such as PWA 1480 exhibit anisotropic elastic behavior, the stresses developed within the single crystal superalloy due to mechanical and thermal loads are likely to be affected by the exact orientation of the secondary crystallographic direction with respect to the geometry of the turbine blade. The effects of secondary crystal orientation on the elastic response of single crystal PWA 1480 superalloy were investigated.

  20. Burst Testing of a Superalloy Disk with a Dual Grain Structure

    NASA Technical Reports Server (NTRS)

    Gayda, John; Kantzos, Pete

    2002-01-01

    Room temperature burst testing of an advanced nickel-base superalloy disk with a dual grain structure was conducted. The disk had a fine grain bore and a coarse grain rim. The results of this test showed that the disk burst at 39,100 rpm in line with predictions based on a 2-D finite element analysis. Further, significant growth of the disk was observed before failure which was also in line with predictions.

  1. Fabrication of tungsten wire reinforced nickel-base alloy composites

    NASA Technical Reports Server (NTRS)

    Brentnall, W. D.; Toth, I. J.

    1974-01-01

    Fabrication methods for tungsten fiber reinforced nickel-base superalloy composites were investigated. Three matrix alloys in pre-alloyed powder or rolled sheet form were evaluated in terms of fabricability into composite monotape and multi-ply forms. The utility of monotapes for fabricating more complex shapes was demonstrated. Preliminary 1093C (2000F) stress rupture tests indicated that efficient utilization of fiber strength was achieved in composites fabricated by diffusion bonding processes. The fabrication of thermal fatigue specimens is also described.

  2. NICKEL-BASE ALLOY

    DOEpatents

    Inouye, H.; Manly, W.D.; Roche, T.K.

    1960-01-19

    A nickel-base alloy was developed which is particularly useful for the containment of molten fluoride salts in reactors. The alloy is resistant to both salt corrosion and oxidation and may be used at temperatures as high as 1800 deg F. Basically, the alloy consists of 15 to 22 wt.% molybdenum, a small amount of carbon, and 6 to 8 wt.% chromium, the balance being nickel. Up to 4 wt.% of tungsten, tantalum, vanadium, or niobium may be added to strengthen the alloy.

  3. In Situ Measurement of the γ/ γ' Lattice Mismatch Evolution of a Nickel-Based Single-Crystal Superalloy During Non-isothermal Very High-Temperature Creep Experiments

    NASA Astrophysics Data System (ADS)

    Le Graverend, Jean-Briac; Dirand, Laura; Jacques, Alain; Cormier, Jonathan; Ferry, Olivier; Schenk, Thomas; Gallerneau, Franck; Kruch, Serge; Mendez, José

    2012-11-01

    The evolution of the γ/ γ' lattice mismatch of the AM1 single-crystal superalloy was measured during in situ non-isothermal very high-temperature creep tests under X-ray synchrotron radiation. The magnitude of the effective lattice mismatch in the 1273 K to 1323 K (1000 °C to 1050 °C) temperature range always increased after overheatings performed at temperatures lower than 1403 K (1130 °C). In contrast, a decrease of its magnitude was observed after overheatings at temperatures greater than 1453 K (1180 °C) due to massive dislocation recovery processes occurring at very high temperature.

  4. The Effect of Heat Treatment on Residual Stress and Machining Distortions in Advanced Nickel Base Disk Alloys

    NASA Technical Reports Server (NTRS)

    Gayda, John

    2001-01-01

    This paper describes an extension of NASA's AST and IDPAT Programs which sought to predict the effect of stabilization heat treatments on residual stress and subsequent machining distortions in the advanced disk alloy, ME-209. Simple "pancake" forgings of ME-209 were produced and given four heat treats: 2075F(SUBSOLVUS)/OIL QUENCH/NO AGE; 2075F/OIL QUENCH/1400F@8HR;2075F/OIL QUENCH/1550F@3HR/l400F@8HR; and 2160F(SUPERSOLVUS)/OIL QUENCH/1550F@3HR/ 1400F@8HR. The forgings were then measured to obtain surface profiles in the heat treated condition. A simple machining plan consisting of face cuts from the top surface followed by measurements of the surface profile opposite the cut were made. This data provided warpage maps which were compared with analytical results. The analysis followed the IDPAT methodology and utilized a 2-D axisymmetric, viscoplastic FEA code. The analytical results accurately tracked the experimental data for each of the four heat treatments. The 1550F stabilization heat treatment was found to significantly reduce residual stresses and subsequent machining distortions for fine grain (subsolvus) ME209, while coarse grain (supersolvus) ME209 would require additional time or higher stabilization temperatures to attain the same degree of stress relief.

  5. Oxidation and the Effects of High Temperature Exposures on Notched Fatigue Life of an Advanced Powder Metallurgy Disk Superalloy

    NASA Technical Reports Server (NTRS)

    Sudbrack, Chantal K.; Draper, Susan L.; Gorman, Timothy T.; Telesman, Jack; Gab, Timothy P.; Hull, David R.

    2012-01-01

    Oxidation and the effects of high temperature exposures on notched fatigue life were considered for a powder metallurgy processed supersolvus heat-treated ME3 disk superalloy. The isothermal static oxidation response at 704 C, 760 C, and 815 C was consistent with other chromia forming nickel-based superalloys: a TiO2-Cr2O3 external oxide formed with a branched Al2O3 internal subscale that extended into a recrystallized - dissolution layer. These surface changes can potentially impact disk durability, making layer growth rates important. Growth of the external scales and dissolution layers followed a cubic rate law, while Al2O3 subscales followed a parabolic rate law. Cr- rich M23C6 carbides at the grain boundaries dissolved to help sustain Cr2O3 growth to depths about 12 times thicker than the scale. The effect of prior exposures was examined through notched low cycle fatigue tests performed to failure in air at 704 C. Prior exposures led to pronounced debits of up to 99 % in fatigue life, where fatigue life decreased inversely with exposure time. Exposures that produced roughly equivalent 1 m thick external scales at the various isotherms showed statistically equivalent fatigue lives, establishing that surface damage drives fatigue debit, not exposure temperature. Fractographic evaluation indicated the failure mode for the pre-exposed specimens involved surface crack initiations that shifted with exposure from predominately single intergranular initiations with transgranular propagation to multi-initiations from the cracked external oxide with intergranular propagation. Weakened grain boundaries at the surface resulting from the M23C6 carbide dissolution are partially responsible for the intergranular cracking. Removing the scale and subscale while leaving a layer where M23C6 carbides were dissolved did not lead to a significant fatigue life improvement, however, also removing the M23C6 carbide dissolution layer led to nearly full recovery of life, with a

  6. An evaluation of an overlay coated ODS superalloy in high temperature oxidation and burner rig environments

    SciTech Connect

    Ganesan, P.; Smith, G.D. )

    1989-01-01

    Inconel alloy MA 6000 is a precipitation hardenable, oxide dispersion strengthened nickel base superalloy produced by mechanical alloying. The alloy was developed as an airfoil section material for advanced gas turbines. The desire for maximum service life prompted a study to evaluate the coatability of alloy MA 6000 and its performance in the coated condition. This paper presents preliminary results of this study and compares the oxidation and burner-rig test results of coated alloy MA 6000, with and without the interlayer, with the performance of uncoated alloy MA 6000.

  7. High Temperature Burst Testing of a Superalloy Disk With a Dual Grain Structure

    NASA Technical Reports Server (NTRS)

    Gayda, J.; Kantzos, P.

    2004-01-01

    Elevated temperature burst testing of a disk with a dual grain structure made from an advanced nickel-base superalloy, LSHR, was conducted. The disk had a fine grain bore and coarse grain rim, produced using NASA's low cost DMHT technology. The results of the spin testing showed the disk burst at 42 530 rpm in line with predictions based on a 2-D finite element analysis. Further, significant growth of the disk was observed before failure which was also in line with predictions.

  8. Mechanical Properties of a Superalloy Disk with a Dual Grain Structure

    NASA Technical Reports Server (NTRS)

    Gayda, John; Gabb, Timothy; Kantzos, Peter

    2003-01-01

    Mechanical properties from an advanced, nickel-base superalloy disk, with a dual grain structure consisting of a fine grain bore and coarse grain rim, were evaluated. The dual grain structure was produced using NASA's low cost Dual Microstructure Heat Treatment (DMHT) process. The results showed the DMHT disk to have a high strength, fatigue resistant bore comparable to a subsolvus (fine grain) heat treated disk, and a creep resistant rim comparable to a supersolvus (coarse grain) heat treated disk. Additional work on subsolvus solutioning before or after the DMHT conversion appears to be a viable avenue for further improvement in disk properties.

  9. Estimation of the engineering elastic constants of a directionally solidified superalloy for finite element structural analysis

    NASA Technical Reports Server (NTRS)

    Abdul-Aziz, Ali; Kalluri, Sreeramesh

    1991-01-01

    The temperature-dependent engineering elastic constants of a directionally solidified nickel-base superalloy were estimated from the single-crystal elastic constants of nickel and MAR-MOO2 superalloy by using Wells' method. In this method, the directionally solidified (columnar-grained) nickel-base superalloy was modeled as a transversely isotropic material, and the five independent elastic constants of the transversely isotropic material were determined from the three independent elastic constants of a cubic single crystal. Solidification for both the single crystals and the directionally solidified superalloy was assumed to be along the (001) direction. Temperature-dependent Young's moduli in longitudinal and transverse directions, shear moduli, and Poisson's ratios were tabulated for the directionally solidified nickel-base superalloy. These engineering elastic constants could be used as input for performing finite element structural analysis of directionally solidified turbine engine components.

  10. Lattice parameter variations during aging in nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Nathal, M. V.; Mackay, R. A.; Garlick, R. G.

    1988-01-01

    The importance of the state of coherency on measurements of gamma/gamma-prime lattice mismatch has been experimentally demonstrated during aging at 1000 C of specimens of an alloy with composition Ni-(8.6)Cr-(5.3)Al-(10.1)Co-(11.7)W-(1.2)Ti-(0.7)Mo (wt pct). Lattice parameter measurements are given as a function of aging time, and the corresponding sample microstructures are presented. The results show that changes of the two phases during aging did not influence the lattice parameter measurements, indicating that aging specimens to produce a semicoherent gamma/gamma-prime structure provides a good approximation of the true, unconstrained lattice mismatch.

  11. Anisotropy of nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Dreshfield, R. L.; Maier, R. D.

    1980-01-01

    The influence of orientation on the tensile and stress rupture behavior of 52 Mar-M247 single crystals was studied. Tensile tests were performed at temperatures between 23 and 1093 C; stress rupture behavior was examined between 760 and 1038 C. The mechanical behavior of the single crystals was rationalized on the basis of the Schmid factor contours for the operative slip systems and the lattice rotations which the crystals underwent during deformation. The tensile properties correlated well with the appropriate Schmid factor contours. The stress rupture lives at lower testing temperatures were greatly influenced by the lattice rotations required to produce cross slip. A unified analysis was attained for the stress rupture life data generated for the Mar-M247 single crystals at 760 and 774 C under a stress of 724 MPa and the data reported for Mar-M200 single crystals tested at 760 C under a stress of 689 MPa. Based on this analysis, the stereographic triangle was divided into several regions which were rank ordered according to stress rupture life for this temperature regime.

  12. Thermal-mechanical fatigue behavior of nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Pelloux, R. M.; Marchand, N.

    1986-01-01

    The main achievements of a 36-month research program are presented. The main objective was to gain more insight into the problem of crack growth under thermal mechanical fatigue (TMF) conditions. This program was conducted at M.I.T. for the period of September 1982 to September 1985. The program was arranged into five technical tasks. Under Task I, the literature of TMF data was reviewed. The goal was to identify the crack propagation conditions in aircraft engines (hot section) and to assess the validity of conventional fracture mechanics parameters to address TMF crack growth. The second task defined the test facilities, test specimen and the testing conditions needed to establish the effectiveness of data correlation parameters identified in Task I. Three materials (Inconel X-750, Hastelloy-X, and B-1900) were chosen for the program. Task II was accomplished in collaboration with Pratt & Whitney Aircraft engineers. Under Task III, a computerized testing system to measure the TMF behavior (LCF and CG behaviors) of various alloys systems was built. The software used to run isothermal and TMF tests was also developed. Built around a conventional servohydraulic machine, the system is capable of push-pull tests under stress or strain and temperature controlled conditions in the temperature range of 25C to 1050C. A crack propagation test program was defined and conducted under Task IV. The test variables included strain range, strain rate (frequency) and temperature. Task V correlated and generalized the Task IV data for isothermal and variable temperature conditions so that several crack propagation parameters could be compared and evaluated. The structural damage (mode of cracking and dislocation substructure) under TMF cycling was identified and contrasted with the isothermal damage to achieve a sound fundamental mechanistic understanding of TMF.

  13. Superalloys with improved weldability for high temperature applications

    DOEpatents

    Seth, Brij B.; George, Easo P.; Babu, Sudarsanum S.; Goodwin, Gene M.; David, Stanislaus A.; Moyer, Carol E.

    2001-01-01

    A cast nickel-base superalloy component (10) is made having a composition containing small amounts of both boron and zirconium which are effective in combination to provide increased weldability, where such alloy is adapted for welding by weld (18) to a second superalloy piece, where the two pieces are firmly bonded together and have a Sigmajig transverse stress value (16) greater than 137.9 million Newtons per square meter.

  14. Effects of Exposures on Superalloys for Space Applications

    NASA Technical Reports Server (NTRS)

    Gabb, Tim; Garg, Anita; Gayda, John

    2007-01-01

    The industry is demanding longer term service at high temperatures for nickel-base superalloys in gas turbine engine as well as potential space applications. However, longer term service can severely tax alloy phase stability, to the potential detriment of mechanical properties. Cast Mar-M247LC and wrought Haynes 230 superalloys were exposed and creep tested for extended times at elevated temperature. Microstructure and phase evaluations were then undertaken for comparisons.

  15. Fretting Stresses in Single Crystal Superalloy Turbine Blade Attachments

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.; Swanson, Gregory

    2000-01-01

    Single crystal nickel base superalloy turbine blades are being utilized in rocket engine turbopumps and turbine engines because of their superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal nickel base turbine blade superalloys are PWA 1480/1493 and PWA 1484. These alloys play an important role in commercial, military and space propulsion systems. High Cycle Fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Blade attachment regions are prone to fretting fatigue failures. Single crystal nickel base superalloy turbine blades are especially prone to fretting damage because the subsurface shear stresses induced by fretting action at the attachment regions can result in crystallographic initiation and crack growth along octahedral planes. Furthermore, crystallographic crack growth on octahedral planes under fretting induced mixed mode loading can be an order of magnitude faster than under pure mode I loading. This paper presents contact stress evaluation in the attachment region for single crystal turbine blades used in the NASA alternate Advanced High Pressure Fuel Turbo Pump (HPFTP/AT) for the Space Shuttle Main Engine (SSME). Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. Blades and the attachment region are modeled using a large-scale 3D finite element (FE) model capable of accounting for contact friction, material orthotrophy, and variation in primary and secondary crystal orientation. Contact stress analysis in the blade attachment regions is presented as a function of coefficient of friction and primary and secondary crystal orientation, Stress results are used to discuss fretting fatigue failure analysis of SSME blades. Attachment stresses are seen to reach

  16. Dendritic microstructure in argon atomized superalloy powders

    NASA Technical Reports Server (NTRS)

    Tewari, S. N.; Kumar, Mahundra

    1986-01-01

    The dendritic microstructure of atomized nickel base superalloy powders (Ni-20 pct Cr, NIMONIC-80A, ASTROALOY, and ZHS6-K) was studied. Prealloyed vacuum induction melted ingots were argon-atomized, the powders were cooled to room temperature, and various powder-size fractions were examined by optical metallography. Linear correlations were obtained for the powder size dependence of the secondary dendrite arm spacing, following the expected d-alpha (R) to the m power dependence on the particle size for all four superalloy compositions. However, the Ni-20 pct Cr alloy, which had much coarser arm spacing as compared to the other three alloys, had a much larger value of m.

  17. A New Approach of Designing Superalloys for Low Density

    NASA Technical Reports Server (NTRS)

    MacKay, Rebecca A.; Gabb, Timothy P.; Smialek, James L.; Nathal, Michael V.

    2010-01-01

    New low-density single-crystal (LDS) alloy, have bee. developed for turbine blade applications, which have the potential for significant improvements in the thrust-to-weight ratio over current production superalloys. An innovative alloying strategy was wed to achieve alloy density reductions, high-temperature creep resistance, microstructural stability, and cyclic oxidation resistance. The alloy design relies on molybdenum as a potent. lower-density solid-solution strengthener in the nickel-based superalloy. Low alloy density was also achieved with modest rhenium levels tmd the absence of tungsten. Microstructural, physical mechanical, and environmental testing demonstrated the feasibility of this new LDS superalloy design.

  18. Stress rupture resistance. [of Co and Ni superalloys

    NASA Technical Reports Server (NTRS)

    Freche, J. C.

    1976-01-01

    Principles underlying the design of metallic systems for stress rupture resistance are outlined by considering the specific case studies of cobalt- and nickel-base superalloys. Ways in which superalloys can be designed for high stress rupture resistance are discussed. In describing the alloying procedures, the strengthening mechanisms involved and methods of avoiding phases detrimental to stress rupture resistance are identified. New processing techniques such as controlled solidification, prealloyed powder processing, and autoclave heat treatments are described as further means of achieving increased stress rupture resistance in superalloy and other systems.

  19. Oxidation and thermal fatigue of coated and uncoated NX-188 nickel-base alloy in a high velocity gas stream

    NASA Technical Reports Server (NTRS)

    Johnson, J. R.; Young, S. G.

    1972-01-01

    A cast nickel-base superalloy, NX-188, coated and uncoated, was tested in a high-velocity gas stream for resistance to oxidation and thermal fatigue by cycling between room temperature and 980, 1040, and 1090 C. Contrary to the behavior of more conventional nickel-base alloys, uncoated NX-188 exhibited the greatest weight loss at the lowest test temperature. In general, on the basis of weight change and metallographic observations a coating consisting of vapor-deposited Fe-Cr-Al-Y over a chromized substrate exhibited the best overall performance in resistance to oxidation and thermal fatigue.

  20. Evaluation of powder metallurgy superalloy disk materials

    NASA Technical Reports Server (NTRS)

    Evans, D. J.

    1975-01-01

    A program was conducted to develop nickel-base superalloy disk material using prealloyed powder metallurgy techniques. The program included fabrication of test specimens and subscale turbine disks from four different prealloyed powders (NASA-TRW-VIA, AF2-1DA, Mar-M-432 and MERL 80). Based on evaluation of these specimens and disks, two alloys (AF2-1DA and Mar-M-432) were selected for scale-up evaluation. Using fabricating experience gained in the subscale turbine disk effort, test specimens and full scale turbine disks were formed from the selected alloys. These specimens and disks were then subjected to a rigorous test program to evaluate their physical properties and determine their suitability for use in advanced performance turbine engines. A major objective of the program was to develop processes which would yield alloy properties that would be repeatable in producing jet engine disks from the same powder metallurgy alloys. The feasibility of manufacturing full scale gas turbine engine disks by thermomechanical processing of pre-alloyed metal powders was demonstrated. AF2-1DA was shown to possess tensile and creep-rupture properties in excess of those of Astroloy, one of the highest temperature capability disk alloys now in production. It was determined that metallographic evaluation after post-HIP elevated temperature exposure should be used to verify the effectiveness of consolidation of hot isostatically pressed billets.

  1. Evolution of precipitate in nickel-base alloy 718 irradiated with argon ions at elevated temperature

    NASA Astrophysics Data System (ADS)

    Jin, Shuoxue; Luo, Fengfeng; Ma, Shuli; Chen, Jihong; Li, Tiecheng; Tang, Rui; Guo, Liping

    2013-07-01

    Alloy 718 is a nickel-base superalloy whose strength derives from γ'(Ni3(Al,Ti)) and γ″(Ni3Nb) precipitates. The evolution of the precipitates in alloy 718 irradiated with argon ions at elevated temperature were examined via transmission electron microscopy. Selected-area electron diffraction indicated superlattice spots disappeared after argon ion irradiation, which showing that the ordered structure of the γ' and γ″ precipitates became disordered. The size of the precipitates became smaller with the irradiation dose increasing at 290 °C.

  2. Hot Corrosion of Nickel-Base Alloys in Biomass-Derived Fuel Simulated Atmosphere

    SciTech Connect

    Leyens, C.; Pint, B.A.; Wright, I.G.

    1999-02-28

    Biomass fuels are considered to be a promising renewable source of energy. However, impurities present in the fuel may cause corrosion problems with the materials used in the hot sections of gas turbines and only limited data are available so far. As part of the Advanced Turbine Systems Program initiated by the U.S. Department of Energy, the present study provides initial data on the hot corrosion resistance of different nickel-base alloys against sodium sulfate-induced corrosion as a baseline, and against salt compositions simulating biomass-derived fuel deposits. Single crystal nickel-superalloy Rene N5, a cast NiCrAlY alloy, a NiCoCrAlY alloy representing industrially used overlay compositions, and a model {beta}NiAl+Hf alloy were tested in 1h thermal cycles at 950 C with different salt coatings deposited onto the surfaces. Whereas the NiCoCrAlY alloy exhibited reasonable resistance against pure sodium sulfate deposits, the NiCrAiY alloy and Rene N5 were attacked severely. Although considered to be an ideal alumina former in air and oxygen at higher temperatures, {beta}NiAl+Hf also suffered from rapid corrosion attack at 950 C when coated with sodium sulfate. The higher level of potassium present in biomass fuels compared with conventional fuels was addressed by testing a NiCoCrAlY alloy coated with salts of different K/Na atomic ratios. Starting at zero Na, the corrosion rate increased considerably when sodium was added to potassium sulfate. In an intermediate region the corrosion rate was initially insensitive to the K/Na ratio but accelerated when very Na-rich compositions were deposited. The key driver for corrosion of the NiCoCrAlY alloy was sodium sulfate rather than potassium sulfate, and no simple additive or synergistic effect of combining sodium and potassium was found.

  3. A high-throughput search for new ternary superalloys

    NASA Astrophysics Data System (ADS)

    Nyshadham, Chandramouli; Hansen, Jacob; Oses, Corey; Curtarolo, Stefano; Hart, Gus

    In 2006 an unexpected new superalloy, Co3[Al,W], was discovered. This new alloy is cobalt-based, in contrast to conventional superalloys, which are nickel-based. Inspired by this new discovery, we performed first-principles calculations, searching through 2224 ternary metallic systems of the form A3[B0.5C0.5], where A = Ni/Co/Fe and [B, C] = all binary combinations of 40 different elements chosen from the periodic table. We found 175 new systems that are better than the Co3[Al, W] superalloy. 75 of these systems are brand new--they have never been reported in experimental literature. These 75 new potential superalloys are good candidates for further experiments. Our calculations are consistent with current experimental literature where data exists. Work supported under: ONR (MURI N00014-13-1-0635).

  4. Surface modification of nickel based alloys for improved oxidation resistance

    SciTech Connect

    Jablonski, Paul D.; Alman, David E.

    2005-02-01

    The present research is aimed at the evaluation of a surface modification treatment to enhance the high temperature stability of nickel-base superalloys. A low Coefficient Thermal Expansion (CTE ~12.5x10-6/°C) alloy based on the composition (in weight %) of Ni-22Mo-12.5Cr was produced by Vacuum Induction Melting and Vacuum Arc Melting and reduced to sheet by conventional thermal-mechanical processing. A surface treatment was devised to enhance the oxidation resistance of the alloys at high temperature. Oxidation tests (in dry and wet air; treated and untreated) were conducted 800°C to evaluate the oxidation resistance of the alloys. The results were compared to the behavior of Haynes 230 (Ni-22Cr) in the treated and untreated conditions. The treatment was not very effective for Haynes 230, as this alloy had similar oxidation behavior in both the treated and untreated conditions. However, the treatment had a significant effect on the behavior of the low CTE alloy. At 800°C, the untreated Ni-12.5Cr alloy was 5 times less oxidation resistant than Haynes 230. However, in the treated condition, the Ni-12.5Cr alloy had comparable oxidation resistance to the Haynes 230 alloy.

  5. Low-Cobalt Powder-Metallurgy Superalloy

    NASA Technical Reports Server (NTRS)

    Harf, F. H.

    1986-01-01

    Highly-stressed jet-engine parts made with less cobalt. Udimet 700* (or equivalent) is common nickel-based superalloy used in hot sections of jet engines for many years. This alloy, while normally used in wrought condition, also gas-atomized into prealloyed powder-metallurgy (PM) product. Product can be consolidated by hot isostatically pressing (HIPPM condition) and formed into parts such as turbine disk. Such jet-engine disks "see" both high stresses and temperatures to 1,400 degrees F (760 degrees C).

  6. Conditions Of Directional Solidification Affect Superalloy

    NASA Technical Reports Server (NTRS)

    Schmidt, D. D.; Alter, W. S.; Hamilton, W. D.; Parr, R. A.

    1992-01-01

    Report describes experiments to determine effects of gradient of temperature and rate of solidification on microstructure and fatigue properties of nickel-based superalloy MAR-M246(Hf). Enhancement of properties extends lifespans of objects, including turbo-pump blades of Space Shuttle Main Engines. Results indicate significant improvements in fatigue properties derived through manipulation of parameters of directional solidification. Particularly MAR-M246(Hf) for turbine blades contains small, well-dispersed blocky carbide and microstructure with small distances between dendrite arms, and without eutectic phase.

  7. Corrosion of nickel-base alloys

    SciTech Connect

    Scarberry, R.C.

    1985-01-01

    The volume consists of three tutorial lectures and 18 contributed papers. The three tutorial lectures provide state-of-the-art background on the physical metallurgy of nickel-base alloys as it relates to corrosion. Also featured are the mechanisms and applications of these alloys and an insight into the corrosion testing techniques. The three tutorial lecture papers will help acquaint newcomers to this family of alloys with a thorough overview. The contributed papers are categorized into four major topics: general corrosion, stress corrosion cracking, fatigue and localized corrosion. Each topic is key-noted by one invited lecture followed by several contributed papers. The papers in the general corrosion section are wide ranging and cover the aspects of material selection, development of galvanic series in corrosive environments, corrosion resistance characteristics, hydrogen permeation and hydrogen embrittlement of nickel and some nickel-base alloys.

  8. High-pressure hydrogen testing of single crystal superalloys for advanced rocket engine turbopump turbine blades

    NASA Technical Reports Server (NTRS)

    Alter, W. S.; Parr, R. A.; Johnston, M. H.; Strizak, J. P.

    1984-01-01

    A screening program to determine the effects of high pressure hydrogen on selected candidate materials for advanced single crystal turbine blade applications is examined. The alloys chosen for the investigation are CM SX-2, CM SX-4C, Rene N-4, and PWA1480. Testing is carried out in hydrogen and helium at 34 MPa and room temperature, with both notched and unnotched single crystal specimens. Results show a significant variation in susceptibility to Hydrogen Environment Embrittlement (HEE) among the four alloys and a marked difference in fracture topography between hydrogen and helium environment specimens.

  9. High-pressure hydrogen testing of single crystal superalloys for advanced rocket engine turbopump turbine blades

    NASA Technical Reports Server (NTRS)

    Parr, R. A.; Alter, W. S.; Johnston, M. H.; Strizak, J. P.

    1985-01-01

    A screening program to determine the effects of high pressure hydrogen on selected candidate materials for advanced single crystal turbine blade applications is examined. The alloys chosen for the investigation are CM SX-2, CM SX-4C, Rene N-4, and PWA1480. Testing is carried out in hydrogen and helium at 34 MPa and room temperature, with both notched and unnotched single crystal specimens. Results show a significant variation in susceptibility to Hydrogen Environment Embrittlement (HEE) among the four alloys and a marked difference in fracture topography between hydrogen and helium environment specimens.

  10. Effect of Environmental Exposures on Fatigue Life of P/M Disk Superalloys

    NASA Technical Reports Server (NTRS)

    Draper, Susan

    2011-01-01

    As the temperature capability of Ni-base superalloy powder metallurgy disks is steadily increased, environmental resistance and protection of advanced nickel-based turbine disk components are becoming increasingly important. Localized surface hot corrosion attack and damage from oxidation have been shown to impair disk fatigue life and may eventually limit disk operating temperatures. NASA Research Announcement (NRA) contracts have been awarded to GE Aviation and Honeywell Aerospace to separately develop fatigue resistant metallic and ceramic coatings for corrosion resistance and the corrosion/fatigue results of selected coatings will be presented. The microstructural response of a bare ME3 disk superalloy has been evaluated for moderate (704 C) and aggressive (760-816 C) oxidizing exposures up to 2,020 hours. Cross section analysis reveals sub-surface damage (significant for aggressive exposures) that consists of Al2O3 "fingers", interfacial voids, a recrystallized precipitate-free layer and GB carbide dissolution. The effects of a Nichrome corrosion coating on this microstructural response will also be presented.

  11. Materials for Advanced Ultrasupercritical Steam Turbines Task 4: Cast Superalloy Development

    SciTech Connect

    Thangirala, Mani

    2015-09-30

    The Steam Turbine critical stationary structural components are high integrity Large Shell and Valve Casing heavy section Castings, containing high temperature steam under high pressures. Hence to support the development of advanced materials technology for use in an AUSC steam turbine capable of operating with steam conditions of 760°C (1400°F) and 35 Mpa (5000 psia), Casting alloy selection and evaluation of mechanical, metallurgical properties and castability with robust manufacturing methods are mandated. Alloy down select from Phase 1 based on producability criteria and creep rupture properties tested by NETL-Albany and ORNL directed the consortium to investigate cast properties of Haynes 282 and Haynes 263. The goals of Task 4 in Phase 2 are to understand a broader range of mechanical properties, the impact of manufacturing variables on those properties. Scale up the size of heats to production levels to facilitate the understanding of the impact of heat and component weight, on metallurgical and mechanical behavior. GE Power & Water Materials and Processes Engineering for the Phase 2, Task 4.0 Castings work, systematically designed and executed casting material property evaluation, multiple test programs. Starting from 15 lbs. cylinder castings to world’s first 17,000 lbs. poured weight, heavy section large steam turbine partial valve Haynes 282 super alloy casting. This has demonstrated scalability of the material for steam Turbine applications. Activities under Task 4.0, Investigated and characterized various mechanical properties of Cast Haynes 282 and Cast Nimonic 263. The development stages involved were: 1) Small Cast Evaluation: 4 inch diam. Haynes 282 and Nimonic 263 Cylinders. This provided effects of liquidus super heat range and first baseline mechanical data on cast versions of conventional vacuum re-melted and forged Ni based super alloys. 2) Step block castings of 300 lbs. and 600 lbs. Haynes 282 from 2 foundry heats were evaluated which

  12. Initial Mechanical Testing of Superalloy Lattice Block Structures Conducted

    NASA Technical Reports Server (NTRS)

    Krause, David L.; Whittenberger, J. Daniel

    2002-01-01

    The first mechanical tests of superalloy lattice block structures produced promising results for this exciting new lightweight material system. The testing was performed in-house at NASA Glenn Research Center's Structural Benchmark Test Facility, where small subelement-sized compression and beam specimens were loaded to observe elastic and plastic behavior, component strength levels, and fatigue resistance for hundreds of thousands of load cycles. Current lattice block construction produces a flat panel composed of thin ligaments arranged in a three-dimensional triangulated trusslike structure. Investment casting of lattice block panels has been developed and greatly expands opportunities for using this unique architecture in today's high-performance structures. In addition, advances made in NASA's Ultra-Efficient Engine Technology Program have extended the lattice block concept to superalloy materials. After a series of casting iterations, the nickel-based superalloy Inconel 718 (IN 718, Inco Alloys International, Inc., Huntington, WV) was successfully cast into lattice block panels; this combination offers light weight combined with high strength, high stiffness, and elevated-temperature durability. For tests to evaluate casting quality and configuration merit, small structural compression and bend test specimens were machined from the 5- by 12- by 0.5-in. panels. Linear elastic finite element analyses were completed for several specimen layouts to predict material stresses and deflections under proposed test conditions. The structural specimens were then subjected to room-temperature static and cyclic loads in Glenn's Life Prediction Branch's material test machine. Surprisingly, the test results exceeded analytical predictions: plastic strains greater than 5 percent were obtained, and fatigue lives did not depreciate relative to the base material. These assets were due to the formation of plastic hinges and the redundancies inherent in lattice block construction

  13. Welding and brazing of nickel and nickel-base alloys

    NASA Technical Reports Server (NTRS)

    Mortland, J. E.; Evans, R. M.; Monroe, R. E.

    1972-01-01

    The joining of four types of nickel-base materials is described: (1) high-nickel, nonheat-treatable alloys, (2) solid-solution-hardening nickel-base alloys, (3) precipitation-hardening nickel-base alloys, and (4) dispersion-hardening nickel-base alloys. The high-nickel and solid-solution-hardening alloys are widely used in chemical containers and piping. These materials have excellent resistance to corrosion and oxidation, and retain useful strength at elevated temperatures. The precipitation-hardening alloys have good properties at elevated temperature. They are important in many aerospace applications. Dispersion-hardening nickel also is used for elevated-temperature service.

  14. Dendritic growth and crystalline quality of nickel-base single grains

    NASA Astrophysics Data System (ADS)

    Siredey, Nathalie; Boufoussi, M'Bareck; Denis, Sabine; Lacaze, Jacques

    1993-05-01

    It is a usual observation that subgrains exist in nickel-base single grain components solidified by the lost wax process. The associated misorientations are generally small, but they can eventually lead to casting defects in the case of highly complex mold shapes. This work presents an attempt to relate the formation of subgrain boundaries with the development of the dendritic solidification microstructure. Experimental investigations have been undertaken on cast components made of AM1 nickel-base superalloy designed for high temperature turbine blades. Single grains were obtained by means of a grain selector at the bottom of each part. Metallographic observations have been made to characterize the dendritic array, together with gamma diffraction to measure the crystalline quality of the material and X-ray topography for mapping of misorientations on a dendritic scale. Small misorientations between dendrite stems have been found at the upper end of the selector which lead to the formation of subgrains. Moreover, during the growth process, the total mosaicity of the material increases, firstly as a consequence of an increase in the misorientations between subgrains, and secondly because of a decrease of the internal quality of each subgrain. It is proposed that misorientations are due to thermomechanical stresses which build up during λ' precipitation at temperatures slightly below the solidus temperature of the alloy.

  15. Advanced powder processing

    SciTech Connect

    Janney, M.A.

    1997-04-01

    Gelcasting is an advanced powder forming process. It is most commonly used to form ceramic or metal powders into complex, near-net shapes. Turbine rotors, gears, nozzles, and crucibles have been successfully gelcast in silicon nitride, alumina, nickel-based superalloy, and several steels. Gelcasting can also be used to make blanks that can be green machined to near-net shape and then high fired. Green machining has been successfully applied to both ceramic and metal gelcast blanks. Recently, the authors have used gelcasting to make tooling for metal casting applications. Most of the work has centered on H13 tool steel. They have demonstrated an ability to gelcast and sinter H13 to near net shape for metal casting tooling. Also, blanks of H13 have been cast, green machined into complex shape, and fired. Issues associated with forming, binder burnout, and sintering are addressed.

  16. NASA Lewis Helps Develop Advanced Saw Blades for the Lumber Industry

    NASA Technical Reports Server (NTRS)

    1998-01-01

    NASA Lewis Research Center's Structures and Material Divisions are centers of excellence in high-temperature alloys for aerospace applications such as advanced aircraft and rocket engines. Lewis' expertise in these fields was enlisted in the development of a new generation of circular sawblades for the lumber industry to use in cutting logs into boards. The U.S. Department of Agriculture's (USDA) Forest Products Laboratory and their supplier had succeeded in developing a thinner sawblade by using a nickel-based alloy, but they needed to reduce excessive warping due to residual stresses. They requested assistance from Lewis' experts, who successfully eliminated the residual stress problem and increased blade strength by over 12 percent. They achieved this by developing an innovative heat treatment based on their knowledge of nickel-based superalloys used in aeropropulsion applications.

  17. Influence of solidification conditions on {gamma}{prime}-phase thermal stability in <001> single crystals of Ni-based superalloys

    SciTech Connect

    Stepanova, N.N.; Sazonova, V.A.; Rodionov, D.P.

    1999-02-05

    Operating conditions for details of the nickel-based superalloys under long-term high-temperature loading necessitate high thermal stability of the alloy structure as a whole and {gamma}{prime}-phase especially, as the latter is an essential factor of the alloy strengthening. The direct investigation of the phase stability of superalloy specimens in the range of operating temperatures is of major interest. In the present work high-temperature X-ray technique was used to study the {gamma}{prime}-phase thermal stability upon heating in the temperature range from 20 C to 1200 C for a series of <001> single crystal specimens of nickel-based superalloy ZhS 26 obtained using various regimes of the melt overheating before solidification.

  18. Elevated temperature fretting fatigue of nickel based alloys

    NASA Astrophysics Data System (ADS)

    Gean, Matthew C.

    This document details the high temperature fretting fatigue of high temperature nickel based alloys common to turbine disk and blade applications. The research consists of three area of focus: Experiments are conducted to determine quantitatively the fretting fatigue lives of advanced nickel based alloys; Analytical tools are developed and used to investigate the fretting fatigue response of the material; Fractographic analysis of the experimental results is used to improve the analytical models employed in the analysis of the experiments. Sixty three fretting fatigue experiments were conducted at 649 °C using a polycrystalline Nickel specimen in contact with directionally solidified and single crystal Nickel pads. Various influences on the fretting fatigue life are investigated. Shot peened Rene' 95 had better fretting fatigue life compared to shot peened Rene' 88. Shot peening produced a 2x increase in life for Rene' 95, but only a marginal improvement in the fretting fatigue life for Rene' 88. Minor cycles in variable amplitude loading produces significant damage to the specimen. Addition of occasional overpeaks in load produces improvements in fretting fatigue life. Contact tractions and stresses are obtained through a variety of available tools. The contact tractions can be efficiently obtained for limited geometries, while FEM can provide the contact tractions for a broader class of problems, but with the cost of increased CPU requirements. Similarly, the subsurface contact stresses can be obtained using the contact tractions as a boundary condition with either a semi-analytical FFT method or FEM. It is found that to calculate contact stresses the FFT was only marginally faster than FEM. The experimental results are combined with the analysis to produce tools that are used to design against fretting fatigue. Fractographic analysis of the fracture surface indicates the nature of the fretting fatigue crack behavior. Interrupted tests were performed to analyze

  19. Study of phase transformations in CMSX-6 and CMSX-8 superalloys

    NASA Astrophysics Data System (ADS)

    Szczotok, Agnieszka; Wierzbicka-Miernik, Anna

    2014-09-01

    Nickel-based superalloys are extensively used mainly in the aircraft and aeronautic industry, particularly in the hottest parts of engines or turbo-reactors. The phase reactions occurring in these heat-resistant materials play a crucial role in many aspects of the processing and service of the highly alloyed materials. Cast Ni-based superalloys are obtained in a complex way and their structure is complicated. Differential scanning calorimetry (DSC) technique was applied for determination of temperature ranges of the phase transformations occurring in the CMSX-6 and CMSX-8 superalloys during heating/cooling processes. Thermophysical properties, including temperatures of the phase transformation, are the critical input parameters in mathematical models of solidification and casting of metallic materials. The literature data concerning phase transformations and performance of the heat treatment for CMSX-6 and CMSX-8 are incomplete and ambiguous. DSC results accompanied by scanning electron microscopy characterization of microstructure of CMSX-6 and CMSX-8 superalloy was applied. The present study will improve the understanding of the fundamental mechanisms of phase transformations of single-crystal nickel-based superalloys.

  20. Nickel-base alloys combat corrosion

    SciTech Connect

    Agarwal, D.C.; Herda, W.

    1995-06-01

    The modern chemical process industry must increase production efficiency to remain competitive. Manufacturers typically meet this challenge by utilizing higher temperatures and pressures, and more-corrosive catalysts. At the same time, the industry has to solve the technical and commercial problems resulting from rigid environmental regulations. To overcome these obstacles, new alloys having higher levels of corrosion resistance have been developed. These materials are based on increased understanding of the physical metallurgy of nickel-base alloys, especially the role of alloying elements. Results of many studies have led to innovations in nickel-chromium-molybdenum alloys containing both high and low amounts of nickel. Higher molybdenum and chromium contents, together with nitrogen additions, have opened up an entirely new class of alloys having unique properties. In addition, a new chromium-base, fully wrought super stainless steel shows excellent promise in solving many corrosion problems. These newer alloys have the ability to combat uniform corrosion, localized corrosion, and stress-corrosion cracking in the harsh halogenic environment of the chemical process industry. This article briefly lists some of the major highlights and corrosion data on recent nickel-chromium-molybdenum and nickel-molybdenum alloys, and the development of a chromium-base, wrought super-austenitic alloy known as Nicrofer 3033 (Alloy 33). Some comparisons with existing alloys are presented, along with a few commercial applications.

  1. Hydrogen Annealing Of Single-Crystal Superalloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Schaeffer, John C.; Murphy, Wendy

    1995-01-01

    Annealing at temperature equal to or greater than 2,200 degrees F in atmosphere of hydrogen found to increase ability of single-crystal superalloys to resist oxidation when subsequently exposed to oxidizing atmospheres at temperatures almost as high. Supperalloys in question are principal constituents of hot-stage airfoils (blades) in aircraft and ground-based turbine engines; also used in other high-temperature applications like chemical-processing plants, coal-gasification plants, petrochemical refineries, and boilers. Hydrogen anneal provides resistance to oxidation without decreasing fatigue strength and without need for coating or reactive sulfur-gettering constituents. In comparison with coating, hydrogen annealing costs less. Benefits extend to stainless steels, nickel/chromium, and nickel-base alloys, subject to same scale-adhesion and oxidation-resistance considerations, except that scale is chromia instead of alumina.

  2. Mapping the evolution of hierarchical microstructures in a Ni-based superalloy.

    PubMed

    Vogel, Florian; Wanderka, Nelia; Balogh, Zoltan; Ibrahim, Mohammed; Stender, Patrick; Schmitz, Guido; Banhart, John

    2013-01-01

    Phase separation of γ' precipitates determines the microstructure and mechanical properties of nickel-based superalloys. In the course of ageing, disordered γ spheres form inside ordered (L12) γ' precipitates, undergo a morphological change to plates and finally split the γ' precipitates. The presence of γ particles inside γ' affects coarsening kinetics and increases alloy hardness. Here we use atom probe tomography to visualize phase separation in a Ni86.1Al8.5Ti5.4 alloy in three dimensions and to quantify the composition of all the phases with near-atomic resolution. We find that γ' precipitates are supersaturated in nickel, thereby driving the formation of γ particles and observe a compositional evolution of the γ particles, which accompanies their morphological change. Our results suggest that by controlling nickel supersaturation we can tailor the phase separation and thereby the properties of nickel-based superalloys. PMID:24356413

  3. Mapping the evolution of hierarchical microstructures in a Ni-based superalloy.

    PubMed

    Vogel, Florian; Wanderka, Nelia; Balogh, Zoltan; Ibrahim, Mohammed; Stender, Patrick; Schmitz, Guido; Banhart, John

    2013-01-01

    Phase separation of γ' precipitates determines the microstructure and mechanical properties of nickel-based superalloys. In the course of ageing, disordered γ spheres form inside ordered (L12) γ' precipitates, undergo a morphological change to plates and finally split the γ' precipitates. The presence of γ particles inside γ' affects coarsening kinetics and increases alloy hardness. Here we use atom probe tomography to visualize phase separation in a Ni86.1Al8.5Ti5.4 alloy in three dimensions and to quantify the composition of all the phases with near-atomic resolution. We find that γ' precipitates are supersaturated in nickel, thereby driving the formation of γ particles and observe a compositional evolution of the γ particles, which accompanies their morphological change. Our results suggest that by controlling nickel supersaturation we can tailor the phase separation and thereby the properties of nickel-based superalloys.

  4. Local Electrode Atom Probe Characterization of Crept CMSX-4 Superalloy

    SciTech Connect

    Miller, Michael K; Reed, R. C.

    2006-01-01

    The solute distributions in crept and annealed single crystal CMSX-4 nickel-based superalloy have been characterized from multi-million atom data sets obtained with the local electrode atom probe. Solute-depleted and solute-enriched regions are evident on both sides of the - interface. Ultrafine (~1 nm diameter) rhenium clusters containing up to ~10-15% Re were evident in the 10-nm wide Reenriched region in the matrix close to the - interface. Re-enriched regions were also detected in asperities in the - interface in the crept conditions.

  5. Constitutive modelling of single crystal and directionally solidified superalloys

    NASA Technical Reports Server (NTRS)

    Jordan, E. H.; Walker, K. P.

    1986-01-01

    The trend towards improved engine efficiency and durability places increasing demands on materials that operate in the hot section of the gas turbine engine. These demands are being met by new coatings and materials such as single crystal and directionally solidified nickel-base superalloys which have greater creep/fatigue resistance at elevated temperatures and reduced susceptibility to grain boundary creep, corrosion and oxidation than conventionally cast alloys. Work carried out as part of a research program aimed at the development of constitutive equations to describe the elevated temperature stress-strain-time behavior of single crystal and directionally solidified turbine blade superalloys is discussed. The program involves both development of suitable constitutive models and their verification through elevated temperature tension-torsion testing of single crystals of PWA 1480.

  6. Analysis of laser beam weldability of Inconel 738 superalloy

    SciTech Connect

    Egbewande, A.T.; Buckson, R.A.; Ojo, O.A.

    2010-05-15

    The susceptibility of pre-weld heat treated laser beam welded IN 738 superalloy to heat affected zone (HAZ) cracking was studied. A pre-weld heat treatment that produced the minimal grain boundary liquation resulted in a higher level of cracking compared to those with more intergranular liquation. This deviation from the general expectation of influence of intergranular liquation extent on HAZ microfissuring is attributable to the reduction in the ability of the base alloy to accommodate welding tensile stress that accompanied a pre-weld heat treatment condition designed to minimize intergranular liquation. Furthermore, in contrast to what has been generally reported in other nickel-based superalloys, a decrease in laser welding speed resulted in increased HAZ cracking in the IN 738, which can be attributed to exacerbated process instability at lower welding speeds.

  7. Analysis of thermoelectric properties of high-temperature complex alloys of nickel-base, iron-base and cobalt-base groups

    NASA Technical Reports Server (NTRS)

    Holanda, R.

    1984-01-01

    The thermoelectric properties alloys of the nickel-base, iron-base, and cobalt-base groups containing from 1% to 25% 106 chromium were compared and correlated with the following material characteristics: atomic percent of the principle alloy constituent; ratio of concentration of two constituents; alloy physical property (electrical resistivity); alloy phase structure (percent precipitate or percent hardener content); alloy electronic structure (electron concentration). For solid-solution-type alloys the most consistent correlation was obtained with electron concentration, for precipitation-hardenable alloys of the nickel-base superalloy group, the thermoelectric potential correlated with hardener content in the alloy structure. For solid-solution-type alloys, no problems were found with thermoelectric stability to 1000; for precipitation-hardenable alloys, thermoelectric stability was dependent on phase stability. The effects of the compositional range of alloy constituents on temperature measurement uncertainty are discussed.

  8. Development of the recovery technology for nickel superalloy blades of the aircraft engine by laser cladding

    NASA Astrophysics Data System (ADS)

    Bykovskiy, D. P.; Petrovskiy, V. N.; Polskiy, V. I.; Chirikov, S. N.; Dzhumaev, P. S.

    2016-09-01

    Development of cladding modes was performed with a superalloy nickel based powder on a flat substrate from material identical to compressor and turbine blades. Cross sections were made, and a visual inspection of the shape and the quality of the clad track as well as themetallographic analysis were performed. Microhardness of the deposition zone, chemical composition of the base, cladded metals, and the heat affected zone were determined.

  9. Vapor phase lubrication of a Ni-based superalloy

    SciTech Connect

    Hanyaloglu, B.; Fedor, D.C.; Graham, E.E.

    1995-03-01

    In addition to ceramics, alloys such as tool steel and nickel- and iron-based superalloys are being considered for high temperature applications such as missile bearings and low heat rejection engines. Studies were made to lubricate a nickel-based superalloy at 500{degrees}C, by using a vaporized aryl phosphate ester, at a concentration of 0.1% in air. From deposition and wear studies it was found that it was impossible to form a good polymeric coating on the superalloy surface. Energy dispersive X-ray analyzer (EDXA) analysis showed that this was due to minute quantities of aluminum in the alloy segregating to the surface, upon being heated to 500{degrees}C, forming a passive oxide coating. It was necessary to activate the surface, in order to lubricate the material successfully. A method of activation by electrodepositing the surface with a layer of iron oxide was developed. Once activated, a good lubricous polymer was formed on the superalloy surface. Tests performed under dynamic conditions and 1 MPa pressure, using an activated specimen surface showed no wear and a coefficient of friction ({mu}) of 0.05. These results stress the importance of material selection for high temperature vapor phase lubrication. 15 refs., 13 figs., 2 tabs.

  10. On rafting in a single crystal nickel-base superalloy after high and low temperature creep

    SciTech Connect

    Henderson, P.; Berglin, L.; Jansson, C.

    1998-12-18

    Rafting (also known as directional coarsening) was first studied more than 25 years ago in SX Udimet 700. At intermediate temperatures, 700--800 C, no microstructural changes were seen during the creep of SX alloys in tests which lasted less than a few thousand hours. In a study of CMSX-4 crept at 750 C the immediate area of the fracture contained many cracks, but away from the fracture the microstructure looked identical to that of the uncrept material. It was not possible to see a change in the material with scanning electron microscopy. The aim of the work presented here was to find a way of imaging low and intermediate temperature creep damage using simple techniques and equipment readily available in most laboratories. This area is one of practical importance as SX alloys are being introduced into industrial gas turbines for power generation and principles for condition assessment need to be developed which are relevant to the temperature of usage. As a first step towards finding a solution it was necessary to study the conditions under which rafting occurred in other SX alloys and a brief summary of some important findings is given.

  11. High temperature monotonic and cyclic deformation in a directionally solidified nickel-base superalloy

    NASA Technical Reports Server (NTRS)

    Huron, Eric S.

    1986-01-01

    Directionally solidified (DS) MAR-M246+Hf was tested in tension and fatigue, at temperatures from 20 C to 1093 C. Tests were performed on (001) oriented specimens at strain rates of 50 % and 0.5 % per minute. In tension, the yield strength was constant up to 704 C, above which the strength dropped off rapidly. A strong dependence of strength on strain rate was seen at the higher temperatures. The deformation mode was observed to change from heterogeneous to homogeneous with increasing temperature. Low Cycle Fatigue tests were done using a fully reversed waveform and total strain control. For a given plastic strain range, lives increased with increasing temperature. For a given temperature strain rate had a strong effect on life. At 704 C, decreasing strain rates decreased life, while at the higher temperatures, decreasing strain rates increased life, for a given plastic strain range. These results could be explained through considerations of the deformation modes and stress levels. At the higher temperatures, marked coarsening caused beneficial stress reductions, but oxidation limited the life. The longitudinal grain boundaries were found to influence slip behavior. The degree of secondary slip adjacent to the boundaries was found to be related to the degree of misorientation between the grains.

  12. On apparent activation energies of creep in nickel-base superalloys

    SciTech Connect

    Picasso, A.C. |; Marzocca, A.J.

    1999-09-10

    Generally, the steady state is well defined in the creep curve in pure metals and some single-phase alloys. In this case, the diagram log {dot {epsilon}} vs. {epsilon} (where {epsilon} is the plastic strain) shows an extensive range of strain where the steady-state creep rate is maintained approximately constant. However, in those materials which present an unstable substructure, such as the particle strengthened alloys, the strain rate reaches a momentary minimum value instead of a steady-state creep rate. In this way, the minimum creep rate is observed in a regime of unstable transition. In this work, a study of the apparent activation energy of creep for IN-X750 was performed, using the differential temperature step technique. The tests were carried out near the minimum strain rate in order to analyze the influence of the material substructure on the values of the apparent activation energy.

  13. Effect of Heating Rate on the Pressureless Sintering Densification of a Nickel-Based Superalloy

    NASA Astrophysics Data System (ADS)

    Levasseur, David; Brochu, Mathieu

    2016-05-01

    Pressureless sintering of Inconel 718 has important technological applications for the densification of metal injection molding or additive manufacturing of parts with powder/binder systems. The effect of heating rates ranging from 15 to 200 K/minute on the sintering behavior of fine (-325 mesh) Inconel 718 powders was studied using the master sintering curve (MSC) concept. A pressureless pulsed electric current sintering setup was used to heat samples. The temperature at the onset of sintering increased as the heating rate increased. The formation of a supersolidus liquid fraction was shifted toward higher temperatures for increased heating rates. The apparent activation energy of sintering was obtained by least squares fitting of the sintering data to the MSC and was in good agreement with the lattice diffusion activation energy of the alloying elements present in Inconel 718. The MSC followed different kinetics for low heating rates (≤50 K/minute) and high heating rates (≥75 K/minute), and these differences were related to liquation kinetics.

  14. Characterization of the Micro-Welding Process for Repair of Nickel Base Superalloys

    NASA Astrophysics Data System (ADS)

    Durocher, J.; Richards, N. L.

    2007-12-01

    Micro-welding is a low-heat input process whereby a metal or cermet, is deposited by the generation of a low-power arc between a consumable electrode and a substrate. The low-heat input of this process offers unique advantages over more common welding processes such as gas tungsten arc, plasma arc, laser, and electron beam welding. At present, the repair of turbine blades and vanes commonly involves gas tungsten arc welding and these components are susceptible to heat affected zone cracking during the weld repair process; vacuum brazing is also used but mainly on low-stress components such as stators. In this study, the low-heat input characteristic of micro-welding has been utilized to simulate repair of Inconel (Trade Mark of Special Metals) 625, Inconel 718, and Inconel 722 filler alloys to a cast Inconel 738 substrate. The effect of micro-welding process parameters on the deposition rate, coating quality, and substrate has been investigated.

  15. Evaluation of the Low Heat Input Process for Weld Repair of Nickel-Base Superalloys

    NASA Astrophysics Data System (ADS)

    Durocher, J.; Richards, N. L.

    2011-10-01

    The repair of turbine blades and vanes commonly involves gas tungsten arc welding or an equivalent process, but unfortunately these components are often susceptible to heat-affected zone (HAZ) cracking during the weld repair process. This is a major problem especially in cast alloys due to their coarse-grain size and where the (Al + Ti) contents is in excess of 3-4%; vacuum brazing is also used but mainly on low stress non-rotating components such as vanes. Micro-welding has the potential to deposit small amounts of filler at low heat input levels with minimum HAZ and thus is an attractive process for depositing a quality weld. As with conventional fusion processes, the filler alloy is deposited by the generation of a low power arc between a consumable electrode and the substrate. The low heat input of this process offers unique advantages over more common welding processes such as gas tungsten arc, plasma arc, laser, and electron beam welding. In this study, the low heat input characteristic of micro-welding has been used to simulate weld repair using Inconel (IN) (Inconel and IN are trademarks of INCO Alloys International) 625, Rene (Rene is a trademark of General Electric Company) 41, Nimonic (Nimonic is a trademark of INCO Alloys International) 105 and Inconel 738LC filler alloys, to a cast Inconel 738LC substrate. The effect of micro-welding process parameters on the deposition rate, coating quality, and substrate has been investigated.

  16. The influence of orientation on the stress rupture properties of nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Maier, R. D.

    1982-01-01

    Constant load creep rupture tests were performed on MAR-M247 single crystals at 724 MPa and 774 C where the effect of anisotropy is prominent. The initial orientations of the specimens as well as the final orientations of selected crystals after stress rupture testing were determined by the Laue back-reflection X-ray technique. The stress rupture lives of the MAR-M247 single crystals were found to be largely determined by the lattice rotations required to produce intersecting slip, because second-stage creep does not begin until after the onset of intersecting slip. Crystals which required large rotations to become oriented for intersecting slip exhibited the shortest stress rupture lives, whereas crystals requiring little or no rotations exhibited the lowest minimum creep rates, and consequently, the longest stress rupture lives.

  17. Orientation dependence of the stress rupture properties of Nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.

    1981-01-01

    The influence of orientation of the stress rupture behavior of Mar-M247 single crystals was studied. Stress rupture tests were performed at 724 MPa and 774 C where the effect of anisotropy is prominent. The mechanical behavior of the single crystals was rationalized on the basis of the Schmid factors for the operative slip systems and the lattice rotations which the crystals underwent during deformation. The stress rupture lives were found to be greatly influenced by the lattice rotations required to produce intersecting slip, because steady-state creep does not begin until after the onset of intersecting slip. Crystals which required large rotations to become oriented for intersecting slip exhibited a large primary creep strain, a large effective stress level at the onset of steady-state creep, and consequently a short stress rupture life. A unified analysis was attained for the stress rupture behavior of the Mar-M247 single crystals tested in this study at 774 C and that of the Mar-M200 single crystals tested in a prior study at 760 C. In this analysis, the standard 001-011-111 stereographic triangle was divided into several regions of crystallographic orientation which were rank ordered according to stress rupture life for this temperature regime. This plot indicates that those crystals having orientations within about 25 deg of the 001 exhibited significantly longer lives when their orientations were closer to the 001-011 boundary of the stereographic triangle than to the 001-111 boundary.

  18. Influence of molybdenum on the creep properties of nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Nathal, M. V.; Pearson, D. D.

    1990-01-01

    The Mo content of an alloy series based on Ni-6 wt pct Al-6 wt pct Ta was systematically varied from 9.8 to 14.6 wt pct, in order to ascertain the influence of Mo on the creep properties of single crystals. The optimum initial gamma-gamma prime microstructure for raft development and creep strength was established in each alloy before testing. It was found that, as the Mo content increased from 9.8 to 14.0 percent, the magnitude of the lattice mismatch increased; upon reaching 14.6 percent, a degradation of mechanical properties occurred due to the precipitation of a third phase. These results suggest that small refractory metal content and initial gamma-prime variations can profoundly affect mechanical properties.

  19. Development of an extra-high strength powder metallurgy nickel-base superalloy

    NASA Technical Reports Server (NTRS)

    Kent, W. B.

    1977-01-01

    A program was conducted to optimize the composition of NASA IIb-11, an alloy originally developed as a wrought material, for thermal stability and to determine the feasibility for producing the alloy using powder metallurgy techniques. Seven compositions were melted and atomized, hot isostatically pressed, cross rolled to disks and heat treated. Tensile and stress rupture properties from room temperature to 870 C (1600 F) were determined in addition to thermal stability characteristics. Processing variables included hot isostatic pressing parameters and handling, cross rolling procedures and heat treatment cycles. NASA IIb-11E displayed the best combination of overall properties for service as a 760 C (1400 F) disk material. Its composition is 0.06 C, 8.5 Cr, 9.0 Co, 2.0 Mo, 7.1 W, 6.6 Ta, 4.5 Al, 0.75 Ti, 0.5 V, 0.7 Hf, 0.01 B, 0.05 Zr and balance Ni. While the alloy exhibits the highest 760 C (1400 F) rupture strength reported for any powder metallurgy disk alloy to date, additional studies to further evaluate the effects of heat treatment may be required. The alloy is not susceptible to topologically close-packed phase formation during thermal exposure at 870 C (1600 F) for 1,500 hours, but its mechanical property levels are lowered due to grain boundary carbide formation.

  20. Atom probe field-ion microscopy investigation of nickel base superalloy welds

    SciTech Connect

    Babu, S.S.; David, S.A.; Vitek, J.M.; Miller, M.K.

    1998-11-01

    Microstructure development and elemental partitioning between {gamma} and {gamma}{prime} were measured in PWA-1480 electron beam welds and CMSX-4 pulsed-laser welds. In PWA-1480 EB welds, eutectic {gamma}{prime} phases were observed along the dendritic boundaries. The elemental partitioning between {gamma} and {gamma}{prime} was found to be similar to that in PWA-1480 base metal. In CMSX-4 pulsed laser welds, negligible eutectic {gamma}{prime} was observed. In addition, fine and irregularly shaped {gamma}{prime} precipitates were observed. The elemental partitioning between {gamma} and {gamma}{prime} was found to be different from that measured in the base metal. Large concentration gradients were observed in the {gamma} phase. The {gamma}{prime} precipitation kinetics in CM247DS alloy was measured using dilatometry and showed differences with different cooling rates. The microstructural investigations showed that at large undercoolings the number density of {gamma}{prime} precipitates increased and led to a finer size. This supports the microstructure development observations in PWA-1480 and CMSX-4 welds. Thermodynamic and kinetic calculations for the Ni-Al-Cr alloy system showed that as the cooling rate increases, the {gamma}{prime} growth leads to large concentration gradients in the {gamma} phase. The calculations agree with the atom probe results from PWA-1480 and CMSX-4 welds.

  1. Microstructural evolution and mechanical behavior of nickel-based superalloy 625 made by selective laser melting

    NASA Astrophysics Data System (ADS)

    Witkin, David B.; Adams, Paul; Albright, Thomas

    2015-03-01

    The mechanical properties and microstructures of Selective Laser Melted (SLM) alloy 625 procured from different suppliers were compared. The post-SLM process of hot isostatic pressing (HIP) led to a relatively coarse recrystallized gamma matrix phase that was similar in all the suppliers' materials, resulting in nearly identical tensile properties. These similarities obscure significant differences between them with respect to the population of second phase particles, which consisted of carbides or Laves phase. During solidification, the final liquid phase is concentrated in Nb, Mo, Si and C, and leads to L --> γ + carbide/Laves eutectic reactions. Secondary particles are very small prior to HIP and their composition has not been analyzed yet, but are limited to the fine-grained eutectic regions of the material prior to HIP. During HIP the gamma phase recrystallizes to remove the original as-solidified SLM microstructure, but secondary particles nucleate and grow where their elemental constituents first solidified, leading to a non-homogeneous distribution. Quasi-static tensile properties do not appear to be sensitive to these differences, but it is likely that other mechanical properties will be affected, especially fatigue and fracture behavior. Surface roughness, large grain size, and pores and voids left unhealed by the HIP cycle will also influence fatigue and fracture. Surface roughness and porosity in particular are features that could be improved by implementing novel approaches to laser processing in SLM.

  2. Thermal-mechanical fatigue behavior of nickel-base superalloys. Final Report

    SciTech Connect

    Pelloux, R.M.; Marchand, N.

    1986-03-01

    The main achievements of a 36-month research program are presented. The main objective was to gain more insight into the problem of crack growth under thermal mechanical fatigue (TMF) conditions. This program was conducted at M.I.T. for the period of September 1982 to September 1985. The program was arranged into five technical tasks. Under Task I, the literature of TMF data was reviewed. The goal was to identify the crack propagation conditions in aircraft engines (hot section) and to assess the validity of conventional fracture mechanics parameters to address TMF crack growth. The second task defined the test facilities, test specimen and the testing conditions needed to establish the effectiveness of data correlation parameters identified in Task I. Three materials (Inconel X-750, Hastelloy-X, and B-1900) were chosen for the program. Task II was accomplished in collaboration with Pratt and Whitney Aircraft engineers. Under Task III, a computerized testing system to measure the TMF behavior (LCF and CG behaviors) of various alloys systems was built. The software used to run isothermal and TMF tests was also developed. Built around a conventional servohydraulic machine, the system is capable of push-pull tests under stress or strain and temperature controlled conditions in the temperature range of 25C to 1050C. A crack propagation test program was defined and conducted under Task IV. The test variables included strain range, strain rate (frequency) and temperature. Task V correlated and generalized the Task IV data for isothermal and variable temperature conditions so that several crack propagation parameters could be compared and evaluated. The structural damage (mode of cracking and dislocation substructure) under TMF cycling was identified and contrasted with the isothermal damage to achieve a sound fundamental mechanistic understanding of TMF.

  3. Superalloy Lattice Block Structures

    NASA Technical Reports Server (NTRS)

    Nathal, M. V.; Whittenberger, J. D.; Hebsur, M. G.; Kantzos, P. T.; Krause, D. L.

    2004-01-01

    Initial investigations of investment cast superalloy lattice block suggest that this technology will yield a low cost approach to utilize the high temperature strength and environmental resistance of superalloys in lightweight, damage tolerant structural configurations. Work to date has demonstrated that relatively large superalloy lattice block panels can be successfully investment cast from both IN-718 and Mar-M247. These castings exhibited mechanical properties consistent with the strength of the same superalloys measured from more conventional castings. The lattice block structure also accommodates significant deformation without failure, and is defect tolerant in fatigue. The potential of lattice block structures opens new opportunities for the use of superalloys in future generations of aircraft applications that demand strength and environmental resistance at elevated temperatures along with low weight.

  4. Mechanical and Microstructure Study of Nickel-Based ODS Alloys Processed by Mechano-Chemical Bonding and Ball Milling

    NASA Astrophysics Data System (ADS)

    Amare, Belachew N.

    Due to the need to increase the efficiency of modern power plants, land-based gas turbines are designed to operate at high temperature creating harsh environments for structural materials. The elevated turbine inlet temperature directly affects the materials at the hottest sections, which includes combustion chamber, blades, and vanes. Therefore, the hottest sections should satisfy a number of material requirements such as high creep strength, ductility at low temperature, high temperature oxidation and corrosion resistance. Such requirements are nowadays satisfied by implementing superalloys coated by high temperature thermal barrier coating (TBC) systems to protect from high operating temperature required to obtain an increased efficiency. Oxide dispersive strengthened (ODS) alloys are being considered due to their high temperature creep strength, good oxidation and corrosion resistance for high temperature applications in advanced power plants. These alloys operating at high temperature are subjected to different loading systems such as thermal, mechanical, and thermo-mechanical combined loads at operation. Thus, it is critical to study the high temperature mechanical and microstructure properties of such alloys for their structural integrity. The primary objective of this research work is to investigate the mechanical and microstructure properties of nickel-based ODS alloys produced by combined mechano-chemical bonding (MCB) and ball milling subjected to high temperature oxidation, which are expected to be applied for high temperature turbine coating with micro-channel cooling system. Stiffness response and microstructure evaluation of such alloy systems was studied along with their oxidation mechanism and structural integrity through thermal cyclic exposure. Another objective is to analyze the heat transfer of ODS alloy coatings with micro-channel cooling system using finite element analysis (FEA) to determine their feasibility as a stand-alone structural

  5. Plastic Behavior of a Nickel-Based Alloy under Monotonic-Tension and Low-Cycle-Fatigue Loading

    SciTech Connect

    Huang, E-Wen; Barabash, Rozaliya; Wang, Yandong; Clausen, Bjorn; Li, Li; Liaw, Peter K; Ice, Gene E; Yang, Dr Ren; Choo, Hahn; Pike, Lee M; Klarstrom, Dwaine L

    2008-01-01

    The plasticity behavior of the annealed HASTELLOY C-22HSTM alloy, a face-centered cubic (FCC), nickel-based superalloy, was examined by the in-situ neutron-diffraction experiments at room temperature. Monotonic-tension and low-cycle-fatigue experiments were conducted to observe the plastic behavior of the alloy. The tension straining and cyclic-loading deformation were studied as a function of the stress. The plastic behaviors during the deformation are discussed in the light of the relationship between the stress and dislocation-density evolutions. The calculated dislocation-density evolutions within the alloys reflect the strain hardening and cyclic hardening/softening. Experimental lattice strains are compared to verify the hardening mechanism at the selected stress levels for tension and cyclic loadings. Combining with the calculations of the dislocation densities, the neutron-diffraction experiments give an evidence of the strain and cyclic hardening of the alloy.

  6. Mechanisms of High Temperature/Low Stress Creep of Ni-Based Superalloy Single Crystals

    SciTech Connect

    Michael J. Mills

    2009-03-05

    Cast nickel-based superalloys are used for blades in land-based, energy conversion and powerplant applications, as well as in aircraft gas turbines operating at temperatures up to 1100 C, where creep is one of the life-limiting factors. Creep of superalloy single crystals has been extensively studied over the last several decades. Surprisingly, only recently has work focused specifically on the dislocation mechanisms that govern high temperature and low stress creep. Nevertheless, the perpetual goal of better engine efficiency demands that the creep mechanisms operative in this regime be fully understood in order to develop alloys and microstructures with improved high temperature capability. At present, the micro-mechanisms controlling creep before and after rafting (the microstructure evolution typical of high temperature creep) has occurred have yet to be identified and modeled, particularly for [001] oriented single crystals. This crystal orientation is most interesting technologically since it exhibits the highest creep strength. The major goal of the program entitled ''Mechanisms of High Temperature/Low Stress Creep of Ni-Based Superalloy Single Crystals'' (DOE Grant DE-FG02-04ER46137) has been to elucidate these creep mechanisms in cast nickel-based superalloys. We have utilized a combination of detailed microstructure and dislocation substructure analysis combined with the development of a novel phase-field model for microstructure evolution.

  7. The elastic modulus correction term in creep activation energies Applied to oxide dispersion strengthened superalloy

    NASA Technical Reports Server (NTRS)

    Malu, M.; Tien, J. K.

    1975-01-01

    The effect of elastic modulus and the temperature dependence of elastic modulus on creep activation energies for an oxide dispersion strengthened nickel-base superalloy are investigated. This superalloy is commercially known as Inconel Alloy MA 753, strengthened both by gamma-prime precipitates and by yttria particles. It is shown that at intermediate temperatures, say below 1500 F, where elastic modulus is weakly dependent on temperature, the modulus correction term to creep activation energy is small. Accordingly, modulus corrections are insignificant for the superalloy considered, which shows high apparent creep activation energies at this temperature. On the contrary, at very high temperatures, the elastic modulus correction term can be significant, thus reducing the creep activation energy to that of vacancy self-diffusion. In order to obtain high-temperature creep resistance, a high-value elastic modulus with a weak dependence on temperature is required.

  8. Elevated temperature creep-fatigue crack propagation in nickel-base alloys and 1 Cr-Mo-V steel

    NASA Astrophysics Data System (ADS)

    Nazmy, M.; Hoffelner, W.; Wüthrich, C.

    1988-04-01

    The crack growth behavior of several high temperature nickel-base alloys, under cyclic and static loading, is studied and reviewed. In the oxide dispersion strengthened (ODS) MA 6000 and MA 754 alloys, the high temperature crack propagation exhibited orientation dependence under cyclic as well as under static loading. The creep crack growth (CCG) behavior of cast nickel-base IN-738 and IN-939* superalloys at 850 °C could be characterized by the stress intensity factor, K 1. In the case of the alloy IN-901 at 500 °C and 600 °C, K 1 was found to be the relevant parameter to characterize the creep crack growth behavior. The energy rate line integral, C*, may be the appropriate loading parameter to describe the creep crack growth behavior of the nickel-iron base IN-800H alloy at 800 °C. The creep crack growth data of 1 Cr-Mo-V steel, with bainitic microstructure, at 550 °C could be correlated better by C * than by K 1.

  9. The mechanisms and temperature dependence of superlattice stacking fault formation in the single-crystal superalloy PWA 1480

    NASA Technical Reports Server (NTRS)

    Milligan, Walter W.; Antolovich, Stephen D.

    1991-01-01

    The mechanism of the formation of superlattice staking faults in the single-crystal nickel-base superalloy PWA 1480 was investigated by observing deformation microstructures in the superalloy single crystals in the temperature range 20-1100 C. Results showed that, in addition to superlattice stacking faults observed after slow strain rate deformation at temperatures from 700 to 950 C, a high-density of superlattice staking faults formed after deformation at 200 C and below. The mechanisms of fault formation, which are different in the high- and the low-temperature regimes, are discussed.

  10. Anisotropic constitutive model for nickel base single crystal alloys: Development and finite element implementation

    NASA Technical Reports Server (NTRS)

    Dame, L. T.; Stouffer, D. C.

    1986-01-01

    A tool for the mechanical analysis of nickel base single crystal superalloys, specifically Rene N4, used in gas turbine engine components is developed. This is achieved by a rate dependent anisotropic constitutive model implemented in a nonlinear three dimensional finite element code. The constitutive model is developed from metallurigical concepts utilizing a crystallographic approach. A non Schmid's law formulation is used to model the tension/compression asymmetry and orientation dependence in octahedral slip. Schmid's law is a good approximation to the inelastic response of the material in cube slip. The constitutive equations model the tensile behavior, creep response, and strain rate sensitivity of these alloys. Methods for deriving the material constants from standard tests are presented. The finite element implementation utilizes an initial strain method and twenty noded isoparametric solid elements. The ability to model piecewise linear load histories is included in the finite element code. The constitutive equations are accurately and economically integrated using a second order Adams-Moulton predictor-corrector method with a dynamic time incrementing procedure. Computed results from the finite element code are compared with experimental data for tensile, creep and cyclic tests at 760 deg C. The strain rate sensitivity and stress relaxation capabilities of the model are evaluated.

  11. Design of an Eta-Phase Precipitation-Hardenable Nickel-Based Alloy with the Potential for Improved Creep Strength Above 1023 K (750 °C)

    NASA Astrophysics Data System (ADS)

    Wong, Matthew J.; Sanders, Paul G.; Shingledecker, John P.; White, Calvin L.

    2015-07-01

    In a number of nickel-based superalloy systems strengthened by gamma prime ( γ'), eta-phase (Ni3Ti, η) forms during prolonged high-temperature exposure, but its effect on mechanical properties is not well characterized. Using thermodynamic modeling and design-of-experiments techniques, three modifications of the nickel-based superalloy Nimonic (Nimonic® is a trademark of Special Metals Corporation group of companies.) 263 were identified that yield increased volume fractions of the eta-phase (Ni3Ti, η) at temperatures above 1023 K (750 °C). Volume fractions of η-phase were evaluated for each alloy and heat-treatment condition using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. Compared to Nimonic 263, small additions of V and Ta were found to increase the volume fraction of η-phase above 1023 K (750 °C) from approximately 5 pct to above 15 pct, thus providing a route for future mechanical behavior experimental studies, which was not in the scope of this work.

  12. Processing-structure characterization of rheocast IN-100 superalloy

    NASA Astrophysics Data System (ADS)

    Cheng, Jung-Jen Allen; Apelian, Diran; Doherty, Roger D.

    1986-11-01

    The rheocasting solidification process has been applied in the production of IN-100 nickel base superalloy. A high vacuum furnace for rheocasting superalloys was used to rheocast ingots under different processing conditions. Processing variables which were evaluated include stirring speed, isothermal stirring time, and volume fraction solid during isothermal stirring. Ingots, furnace cooled at the same rate but without stirring, were also examined for comparison with the rheocast ingots. A detailed microstructural examination was made of the resultant microstructure both on furnace cooling after stirring and on reheating to the isothermal stirring temperature followed by water quenching. Rheocasting yielded fine-grained structures, where the extent of microsegregatiori, the variation in macrostructure, and the solidification-induced porosity were found to be reduced in comparison to the unstirred ingot. The grain size and nonuniformity in the as-cast ingot were reduced by increasing the stirring speed, isothermal stirring time, or the volume fraction solid during stirring. The degree of the microsegregation decreased significantly with increasing volume fraction solid. Grain boundaries, both with and without solute enrichment, were found in the rosette-like solid particles after rheocasting, lending support to the Vogel-Cantor-Doherty model of rheocasting based on the formation of grain boundaries by strain-induced recrystallization and by sintering. It is clear from these results that the microstructure of this superalloy was significantly improved by rheocasting. Improved mechanical properties were also found and will be reported separately.

  13. Effect of tensile mean stress on fatigue behavior of single-crystal and directionally solidified superalloys

    NASA Technical Reports Server (NTRS)

    Kalluri, Sreeramesh; Mcgaw, Michael A.

    1990-01-01

    Two nickel base superalloys, single crystal PWA 1480 and directionally solidified MAR-M 246 + Hf, were studied in view of the potential usage of the former and usage of the latter as blade materials for the turbomachinery of the space shuttle main engine. The baseline zero mean stress (ZMS) fatigue life (FL) behavior of these superalloys was established, and then the effect of tensile mean stress (TMS) on their FL behavior was characterized. At room temperature these superalloys have lower ductilities and higher strengths than most polycrystalline engineering alloys. The cycle stress-strain response was thus nominally elastic in most of the fatigue tests. Therefore, a stress range based FL prediction approach was used to characterize both the ZMS and TMS fatigue data. In the past, several researchers have developed methods to account for the detrimental effect of tensile mean stress on the FL for polycrystalline engineering alloys. However, the applicability of these methods to single crystal and directionally solidified superalloys has not been established. In this study, these methods were applied to characterize the TMS fatigue data of single crystal PWA 1480 and directionally solidified MAR-M 246 + Hf and were found to be unsatisfactory. Therefore, a method of accounting for the TMS effect on FL, that is based on a technique proposed by Heidmann and Manson was developed to characterize the TMS fatigue data of these superalloys. Details of this method and its relationship to the conventionally used mean stress methods in FL prediction are discussed.

  14. Microstructural analysis of laser weld fusion zone in Haynes 282 superalloy

    SciTech Connect

    Osoba, L.O.; Ding, R.G.; Ojo, O.A.

    2012-03-15

    Analytical electron microscopy and spectroscopy analyses of the fusion zone (FZ) microstructure in autogenous laser beam welded Haynes 282 (HY 282) superalloy were performed. The micro-segregation patterns observed in the FZ indicate that Co, Cr and Al exhibited a nearly uniform distribution between the dendrite core and interdendritic regions while Ti and Mo were rejected into the interdendritic liquid during the weld solidification. Transmission electron diffraction analysis and energy dispersive X-ray microanalysis revealed the second phase particles formed along the FZ interdendritic region to be Ti-Mo rich MC-type carbide particles. Weld FZ solidification cracking, which is sometimes associated with the formation of {gamma}-{gamma}' eutectic in {gamma}' precipitation strengthened nickel-base superalloys, was not observed in the HY 282 superalloy. Modified primary solidification path due to carbon addition in the newly developed superalloy is used to explain preclusion of weld FZ solidification cracking in the material. - Highlights: Black-Right-Pointing-Pointer A newly developed superalloy was welded by CO{sub 2} laser beam joining technique. Black-Right-Pointing-Pointer Electron microscopy characterization of the weld microstructure was performed. Black-Right-Pointing-Pointer Identified interdendritic microconstituents consist of MC-type carbides. Black-Right-Pointing-Pointer Modification of primary solidification path is used to explain cracking resistance.

  15. Microstructural response to heat affected zone cracking of prewelding heat-treated Inconel 939 superalloy

    SciTech Connect

    Gonzalez, M.A.; Garza, A.

    2011-12-15

    The microstructural response to cracking in the heat-affected zone (HAZ) of a nickel-based IN 939 superalloy after prewelding heat treatments (PWHT) was investigated. The PWHT specimens showed two different microstructures: 1) spherical ordered {gamma} Prime precipitates (357-442 nm), with blocky MC and discreet M{sub 23}C{sub 6} carbides dispersed within the coarse dendrites and in the interdendritic regions; and 2) ordered {gamma} Prime precipitates in 'ogdoadically' diced cube shapes and coarse MC carbides within the dendrites and in the interdendritic regions. After being tungsten inert gas welded (TIG) applying low heat input, welding speed and using a more ductile filler alloy, specimens with microstructures consisting of spherical {gamma} Prime precipitate particles and dispersed discreet MC carbides along the grain boundaries, displayed a considerably improved weldability due to a strong reduction of the intergranular HAZ cracking associated with the liquation microfissuring phenomena. - Highlights: Black-Right-Pointing-Pointer Homogeneous microstructures of {gamma} Prime spheroids and discreet MC carbides of Ni base superalloys through preweld heat treatments. Black-Right-Pointing-Pointer {gamma} Prime spheroids and discreet MC carbides reduce the intergranular HAZ liquation and microfissuring of Nickel base superalloys. Black-Right-Pointing-Pointer Microstructure {gamma} Prime spheroids and discreet blocky type MC carbides, capable to relax the stress generated during weld cooling. Black-Right-Pointing-Pointer Low welding heat input welding speeds and ductile filler alloys reduce the HAZ cracking susceptibility.

  16. Processing of Advanced Cast Alloys for A-USC Steam Turbine Applications

    NASA Astrophysics Data System (ADS)

    Jablonski, Paul D.; Hawk, Jeffery A.; Cowen, Christopher J.; Maziasz, Philip J.

    2012-02-01

    The high-temperature components within conventional supercritical coal-fired power plants are manufactured from ferritic/martensitic steels. To reduce greenhouse-gas emissions, the efficiency of pulverized coal steam power plants must be increased to as high a temperature and pressure as feasible. The proposed steam temperature in the DOE/NETL Advanced Ultra Supercritical power plant is high enough (760°C) that ferritic/martensitic steels will not work for the majority of high-temperature components in the turbine or for pipes and tubes in the boiler due to temperature limitations of this class of materials. Thus, Ni-based superalloys are being considered for many of these components. Off-the-shelf forged nickel alloys have shown good promise at these temperatures, but further improvements can be made through experimentation within the nominal chemistry range as well as through thermomechanical processing and subsequent heat treatment. However, cast nickel-based superalloys, which possess high strength, creep resistance, and weldability, are typically not available, particularly those with good ductility and toughness that are weldable in thick sections. To address those issues related to thick casting for turbine casings, for example, cast analogs of selected wrought nickel-based superalloys such as alloy 263, Haynes 282, and Nimonic 105 have been produced. Alloy design criteria, melt processing experiences, and heat treatment are discussed with respect to the as-processed and heat-treated microstructures and selected mechanical properties. The discussion concludes with the prospects for full-scale development of a thick section casting for a steam turbine valve chest or rotor casing.

  17. Recrystallization characteristics of oxide dispersion strengthened nickel-base alloys

    NASA Technical Reports Server (NTRS)

    Hotzler, R. K.; Glasgow, T. K.

    1980-01-01

    Electron microscopy was employed to study the process of recrystallization in two oxide dispersion strengthened (ODS) mechanically alloyed nickel-base alloys, MA 754 and MA 6000E. MA 754 contained both fine, uniformly dispersed particles and coarser oxides aligned along the working direction. Hot rolled MA 754 had a grain size of 0.5 microns and high dislocation densities. After partial primary recrystallization, the fine grains transformed to large elongated grains via secondary (or abnormal) grain growth. Extruded and rolled MA 6000E contained equiaxed grains of 0.2 micron diameter. Primary recrystallization occurring during working eliminated virtually all dislocations. Conversion from fine to coarse grains was triggered by gamma prime dissolution; this was also a process of secondary or abnormal grain growth. Comparisons were made to conventional and oxide dispersion strengthened nickel-base alloys.

  18. Attack polish for nickel-base alloys and stainless steels

    DOEpatents

    Steeves, Arthur F.; Buono, Donald P.

    1983-01-01

    A chemical attack polish and polishing procedure for use on metal surfaces such as nickel base alloys and stainless steels. The chemical attack polish comprises Fe(NO.sub.3).sub.3, concentrated CH.sub.3 COOH, concentrated H.sub.2 SO.sub.4 and H.sub.2 O. The polishing procedure includes saturating a polishing cloth with the chemical attack polish and submicron abrasive particles and buffing the metal surface.

  19. Attack polish for nickel-base alloys and stainless steels

    DOEpatents

    Not Available

    1980-05-28

    A chemical attack polish and polishing procedure for use on metal surfaces such as nickel base alloys and stainless steels is described. The chemical attack polich comprises FeNO/sub 3/, concentrated CH/sub 3/COOH, concentrated H/sub 2/SO/sub 4/ and H/sub 2/O. The polishing procedure includes saturating a polishing cloth with the chemical attack polish and submicron abrasive particles and buffing the metal surface.

  20. Method of polishing nickel-base alloys and stainless steels

    DOEpatents

    Steeves, Arthur F.; Buono, Donald P.

    1981-01-01

    A chemical attack polish and polishing procedure for use on metal surfaces such as nickel base alloys and stainless steels. The chemical attack polish comprises Fe(NO.sub.3).sub.3, concentrated CH.sub.3 COOH, concentrated H.sub.2 SO.sub.4 and H.sub.2 O. The polishing procedure includes saturating a polishing cloth with the chemical attack polish and submicron abrasive particles and buffing the metal surface.

  1. Metal dusting and carburization resistance of nickel-base alloys

    SciTech Connect

    Kloewer, J.; Grabke, H.J.; Mueller-Lorenz, E.M.; Agarwal, D.C.

    1997-08-01

    Severe material failures caused by so-called metal dusting have been reported during recent years. The reason for these failures were strongly carburizing CO-H{sub 2} gas mixtures such as encountered in chemical plants for the synthesis of hydrocarbons, methanol, ammonia etc. as well as in plants for the reduction of iron ores. The carburization behavior of nine commercial nickel-base alloys and four iron-nickel-chromium alloys was investigated at 650 C in a carburizing H{sub 2}-CO-H{sub 2}O-gas with a carbon activity of a{sub c} {much_gt} 1. The iron-nickel-chromium alloys suffered severe metal dusting after a very short test period. Nickel base alloys were generally less susceptible to metal dusting than iron-base alloys. However, their corrosion behavior was found to depend sensitively on the chromium concentration of the respective alloys. Alloys like alloy 600H, with a chromium concentration of only 16%, suffered wastage rates which were similar to those of the more resistant iron-base alloys. Nickel-base alloys with chromium concentrations of 25% and above, on the other hand, showed no significant evidence of metal dusting even after 10,000 hours of exposure. It was found that these alloys are protected against metal dusting by the formation of a dense, self-healing chromia scale, which prevents the penetration of carbon into the base metal.

  2. Influence of Processing Parameters on Grain Size Evolution of a Forged Superalloy

    NASA Astrophysics Data System (ADS)

    Reyes, L. A.; Páramo, P.; Salas Zamarripa, A.; de la Garza, M.; Guerrero-Mata, M. P.

    2016-01-01

    The microstructure evolution of nickel-based superalloys has a great influence on the mechanical behavior during service conditions. Microstructure modification and the effect of process variables such as forging temperature, die-speed, and tool heating were evaluated after hot die forging of a heat-resistant nickel-based alloy. Forging sequences in a temperature range from 1253 to 1323 K were considered through experimental trials. An Avrami model was applied using finite element data to evaluate the average grain size and recrystallization at different evolution zones. It was observed that sequential forging at final temperatures below 1273 K provided greater grain refinement through time-dependent recrystallization phenomena. This investigation was aim to explore the influence of forging parameters on grain size evolution in order to design a fully homogenous and refined microstructure after hot die forging.

  3. Processing-structure characterization of rheocast IN-100 superalloy

    NASA Technical Reports Server (NTRS)

    Cheng, Jung-Jen Allen; Apelian, Diran; Doherty, Roger D.

    1986-01-01

    The rheocasting solidification process was applied in the production of IN-100 nickel base superalloy, and the effects of processing variables, such as stirring speed, isothermal stirring time, and volume fraction solid during isothermal stirring, on the resultant rheocast structure were investigated. Ingots that were furnace cooled at the same rate but without stirring were compared with the rheocast ingots. Rheocasting yielded fine-grained structures, where the extent of microsegregation, the variation in macrostructure, and the solidification-induced porosity and ingot cracking were found to be reduced in comparison to the unstirred ingots. The grain size and nonuniformity were reduced by increasing the stirring speed, isothermal stirring time, or the volume fraction solid during stirring; decreased microsegregation was achieved by an increase in the volume fraction solid. The structures of grain boundaries lent support to the grain boundary mechanism proposed by Vogel et al. (1977) for rheocasting.

  4. Microstructural Evaluation of Forging Parameters for Superalloy Disks

    NASA Technical Reports Server (NTRS)

    Falsey, John R.

    2004-01-01

    Forgings of nickel base superalloy were formed under several different strain rates and forging temperatures. Samples were taken from each forging condition to find the ASTM grain size, and the as large as grain (ALA). The specimens were mounted in bakelite, polished, etched and then optical microscopy was used to determine grain size. The specimens ASTM grain sizes from each forging condition were plotted against strain rate, forging temperature, and presoak time. Grain sizes increased with increasing forging temperature. Grain sizes also increased with decreasing strain rates and increasing forging presoak time. The ALA had been determined from each forging condition using the ASTM standard method. Each ALA was compared with the ASTM grain size of each forging condition to determine if the grain sizes were uniform or not. The forging condition of a strain rate of .03/sec and supersolvus heat treatment produced non uniform grains indicated by critical grain growth. Other anomalies are noted as well.

  5. Low-Density, Creep-Resistant Single-Crystal Superalloys

    NASA Technical Reports Server (NTRS)

    MacKay, Rebecca A.; Gabb, Timothy P.; Smialek, James L.; Nathal, Michael V.

    2006-01-01

    Several recently formulated nickel-base superalloys have been developed with excellent high-temperature creep resistance, at lower densities than those of currently used nickel-base superalloys. These alloys are the latest products of a continuing effort to develop alloys that have even greater strength-to-weight ratios, suitable for use in turbine blades of aircraft engines. Mass densities of turbine blades exert a significant effect on the overall weight of aircraft. For a given aircraft, a reduction in the density of turbine blades enables design reductions in the weight of other parts throughout the turbine rotor, including the disk, hub, and shaft, as well as supporting structures in the engine. The resulting total reduction in weight can be 8 to 10 times that of the reduction in weight of the turbine blades. The approach followed in formulating these alloys involved several strategies for identifying key alloying elements and the range of concentration of each element to study. To minimize the number of alloys needed to be cast, a design-of--experiments methodology was adopted. A statistics-based computer program that models the effects of varying compositions of four elements, including effects of two-way interactions between elements, was used to test all possible alloys within the design space. The starting points for the computational analysis were three alloy compositions mandated by engineering consensus. After likewise identification of key alloying elements to vary and the allowed ranges of concentrations, the computer program then selects a minimum number of alloys within the design space to allow determination of effects for all four elements and their interactions.

  6. Examination of the influence of coatings on thin superalloy sections. Volume 1: Description and analysis

    NASA Technical Reports Server (NTRS)

    Kaufman, M.

    1974-01-01

    The effects of an aluminide coating and of section thickness were investigated on two cast nickel-base superalloys. Cast section thickness ranged from 0.038 cm to 0.15 cm. Simulated engine exposures in a jet fuel burner rig with cyclic air cooling were studied. The effects of surface machining before coating and re-machining and re-coating after exposures were examined. The properties evaluated included tensile strength, stress rupture, high-cycle mechanical fatigue, and thermal fatigue. A metallurgical analysis was made of the microstructures of the coated and uncoated alloy.

  7. Feasibility of producing cast-refractory metal-fiber superalloy composites

    NASA Technical Reports Server (NTRS)

    Mcintyre, R. D.

    1973-01-01

    A study was conducted to evaluate the feasibility of direct casting as a practical method for producing cast superalloy tungsten or columbium alloy fiber composites while retaining a high percentage of fiber strength. Fourteen nickel base, four cobalt, and three iron based matrices were surveyed for their degree of reaction with the metal fibers. Some stress-rupture results were obtained at temperatures of 760, 816, 871, and 1093 C for a few composite systems. The feasibility of producing acceptable composites of some cast nickel, cobalt, and iron matrix alloys with tungsten or columbium alloy fibers was demonstrated.

  8. Mechanical property anisotropy in superalloy El-929 directionally solidified by an exothermic technique

    NASA Technical Reports Server (NTRS)

    Pradhan, D. C.; Sharma, K. K.; Tewari, S. N.

    1986-01-01

    Directional solidification (DS) of the nickel-based superalloy El-929 was carried out by employing the exothermic technique for preparing several 150 mm long x 55 mm diameter rods. Specimens machined from blanks cut at 0, 45, 75 and 90 deg to the chill surface were tensile and stress-rupture tested at different temperatures. The air-melted DS alloy, when loaded parallel to the growth direction, shows considerable improvement in stress-rupture life and tensile ductility as compared with the vacuum induction melted, forged and heat-treated alloy. However, these property advantages rapidly degrade with the increasing deviation of the load axis from the growth direction.

  9. Role of molybdenum in the Na2SO4 induced corrosion of superalloys at high temperature

    NASA Technical Reports Server (NTRS)

    Misra, A. K.

    1987-01-01

    Sodium sulfate induced corrosion of a molybdenum containing nickel-base superalloy, Udimet 700, was studied in laboratory furnace test and in a high velocity (Mach 0.3) burner rig. Tlhe effect of SO2 content in the atmosphere on the corrosion behavior in the laboratory furnace tests was determined. catastrophic corrosion occursonly when the melt contains MoO3 in addition to Na2SO4 and Na2MoO4. The conditions under which catastrophic corrosion occurs are identified and a mechanism is described to explain the catastrophic corrosion.

  10. Configurationally exhaustive first-principles study of a quaternary superalloy with a vast configuration space

    NASA Astrophysics Data System (ADS)

    Maisel, S. B.; Höfler, M.; Müller, S.

    2016-07-01

    Exploration of the vast configuration space encountered in a multicomponent alloy is impossible without a suitable engine like the cluster-expansion (CE) method. While a CE ansatz can be formulated for an arbitrary number of components n , the combinatorial explosion of configuration space with increasing n can still be prohibitive. In this paper, we present a configurationally exhaustive study of a four-component nickel-based superalloy. We obtain all ground-state compounds, temperature- and concentration-dependent configurational energies, and micrographs of the γ /γ' microstructure of the γ'-strengthened superalloy Ni-Al-Ta-W. Several phenomena that cannot be studied from the binary building blocks Ni-Al, Ni-W, or Ni-Ta alone are discussed, e.g., the suppression of γ'' formation in Al-Ni-Ta-W, the effect of Ta on the γ' composition, and the tungsten partitioning ratio as a function of both temperature and bulk composition.

  11. A study of microstructural characteristics and differential thermal analysis of Ni-based superalloys

    NASA Technical Reports Server (NTRS)

    Aggarwal, M. D.; Lal, R. B.; Oyekenu, Samuel A.; Parr, Richard; Gentz, Stephen

    1989-01-01

    The objective of this work is to correlate the mechanical properties of the Ni-based superalloy MAR M246(Hf) used in the Space Shuttle Main Engine with its structural characteristics by systematic study of optical photomicrographs and differential thermal analysis. The authors developed a method of predicting the liquidus and solidus temperature of various nickel based superalloys (MAR-M247, Waspaloy, Udimet-41, polycrystalline and single crystals of CMSX-2 and CMSX-3) and comparing the predictions with the experimental differential thermal analysis (DTA) curves using Perkin-Elmer DTA 1700. The method of predicting these temperatures is based on the additive effect of the components dissolved in nickel. The results were compared with the experimental values.

  12. The unusual near-threshold FCG behavior of a single crystal superalloy and the resolved shear stress as the crack driving force

    NASA Technical Reports Server (NTRS)

    Telesman, Jack; Ghosn, Louis J.

    1989-01-01

    An investigation of the fatigue growth (FCG) behavior of PWA 1480 single crystal nickel base superalloy was conducted. Typical Paris region behavior was observed above a Delta-K of 8 MPa sq rt m. However, below that stress intensity range, the alloy exhibted highly unusual behavior. The behavior consisted of a region where the crack growth rate became essentially independent of the applied stress intensity. The transition in the FCG behavior was related to a change in the observed crack growth mechanisms.

  13. Fatigue damage modeling for coated single crystal superalloys

    NASA Technical Reports Server (NTRS)

    Nissley, David M.

    1988-01-01

    A high temperature, low-cycle fatigue life prediction method for coated single crystal nickel-base superalloys is being developed. The method is being developed for use in predicting crack initiation life of coated single crystal turbine airfoils. Although the models are being developed using coated single crystal PWA 1480, they should be readily adaptable to other coated nickel-base single crystal materials. The coatings choosen for this effort were of two generic types: a low pressure plasma sprayed NiCoCrAlY overlay, designated PWA 286, and an aluminide diffusion, designated PWA 273. In order to predict the useful crack initiation life of airfoils, the constitutive and failure behavior of the coating/substrate combination must be taken into account. Coatings alter the airfoil surface microstructure and are a primary source from which cracks originate. The adopted life prediction approach addresses this complexity by separating the coating and single crystal crack initiation regimes. This provides a flexible means for using different life model formulations for the coating and single crystal materials. At the completion of this program, all constitutive and life model formulations will be available in equation form and as software. The software will use the MARC general purpose finite element code to drive the constitutive models and calculate life parameters.

  14. NEUTRON-DIFFRACTION STUDY ON PLASTIC BEHAVIOR OF A NICKEL-BASED ALLOY UNDER THE MONOTONIC-TENSION AND THE LOW-CYCLE-FATIGUE EXPERIMENTS

    SciTech Connect

    Huang, E-Wen; Barabash, Rozaliya; Clausen, Bjorn; Wang, Yandong; Yang, Dr Ren; Li, Li; Choo, Hahn; Liaw, Peter K

    2007-01-01

    The plastic behavior of an annealed HASTELLOY C-22HS alloy, a face-centered cubic (FCC), nickel-based superalloy, was examined by in-situ neutron-diffraction measurements at room temperature. Both monotonic-tension and low-cycle-fatigue experiments were conducted. Monotonic-tension straining and cyclic-loading deformation were studied as a function of stress. The plastic behavior during deformation is discussed in light of the relationship between the stress and dislocation-density evolution. The calculated dislocation-density evolution within the alloy reflects the strain hardening and cyclic hardening/softening. Experimentally determined lattice strains are compared to verify the hardening mechanism at selected stress levels for tension and cyclic loadings. Combined with calculations of the dislocation densities, the neutron-diffraction experiments provide direct information about the strain and cyclic hardening of the alloy.

  15. Neutron Diffraction Study on Plastic behavior of a Nickel-Based Alloy Under the Monotonic-Tension and the Low-Cyclic-Fatigue Experiments

    SciTech Connect

    Huang, E.-W.; Barabash, R.; Clausen, B.; Wang, Y.; Yang, R.; Li, L.; Choo, H.; Liaw, P.K.

    2007-11-02

    The plastic behavior of an annealed HASTELLOY C-22HS alloy, a face-centered cubic (FCC), nickel-based superalloy, was examined by in-situ neutron-diffraction measurements at room temperature. Both monotonic-tension and low-cycle-fatigue experiments were conducted. Monotonic-tension straining and cyclic-loading deformation were studied as a function of stress. The plastic behavior during deformation is discussed in light of the relationship between the stress and dislocation-density evolution. The calculated dislocation-density evolution within the alloy reflects the strain hardening and cyclic hardening/softening. Experimentally determined lattice strains are compared to verify the hardening mechanism at selected stress levels for tension and cyclic loadings. Combined with calculations of the dislocation densities, the neutron-diffraction experiments provide direct information about the strain and cyclic hardening of the alloy.

  16. Fiber-Reinforced Superalloys For Rocket Engines

    NASA Technical Reports Server (NTRS)

    Lewis, Jack R.; Yuen, Jim L.; Petrasek, Donald W.; Stephens, Joseph R.

    1990-01-01

    Report discusses experimental studies of fiber-reinforced superalloy (FRS) composite materials for use in turbine blades in rocket engines. Intended to withstand extreme conditions of high temperature, thermal shock, atmospheres containing hydrogen, high cycle fatigue loading, and thermal fatigue, which tax capabilities of even most-advanced current blade material - directionally-solidified, hafnium-modified MAR M-246 {MAR M-246 (Hf) (DS)}. FRS composites attractive combination of properties for use in turbopump blades of advanced rocket engines at temperatures from 870 to 1,100 degrees C.

  17. Precipitation hardening austenitic superalloys

    DOEpatents

    Korenko, Michael K.

    1985-01-01

    Precipitation hardening, austenitic type superalloys are described. These alloys contain 0.5 to 1.5 weight percent silicon in combination with about 0.05 to 0.5 weight percent of a post irradiation ductility enhancing agent selected from the group of hafnium, yttrium, lanthanum and scandium, alone or in combination with each other. In addition, when hafnium or yttrium are selected, reductions in irradiation induced swelling have been noted.

  18. Additive Manufacturing of IN100 Superalloy Through Scanning Laser Epitaxy for Turbine Engine Hot-Section Component Repair: Process Development, Modeling, Microstructural Characterization, and Process Control

    NASA Astrophysics Data System (ADS)

    Acharya, Ranadip; Das, Suman

    2015-09-01

    This article describes additive manufacturing (AM) of IN100, a high gamma-prime nickel-based superalloy, through scanning laser epitaxy (SLE), aimed at the creation of thick deposits onto like-chemistry substrates for enabling repair of turbine engine hot-section components. SLE is a metal powder bed-based laser AM technology developed for nickel-base superalloys with equiaxed, directionally solidified, and single-crystal microstructural morphologies. Here, we combine process modeling, statistical design-of-experiments (DoE), and microstructural characterization to demonstrate fully metallurgically bonded, crack-free and dense deposits exceeding 1000 μm of SLE-processed IN100 powder onto IN100 cast substrates produced in a single pass. A combined thermal-fluid flow-solidification model of the SLE process compliments DoE-based process development. A customized quantitative metallography technique analyzes digital cross-sectional micrographs and extracts various microstructural parameters, enabling process model validation and process parameter optimization. Microindentation measurements show an increase in the hardness by 10 pct in the deposit region compared to the cast substrate due to microstructural refinement. The results illustrate one of the very few successes reported for the crack-free deposition of IN100, a notoriously "non-weldable" hot-section alloy, thus establishing the potential of SLE as an AM method suitable for hot-section component repair and for future new-make components in high gamma-prime containing crack-prone nickel-based superalloys.

  19. Superalloy Lattice Block Structures

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.; Nathal, M. V.; Hebsur, M. G.; Kraus, D. L.

    2003-01-01

    In their simplest form, lattice block panels are produced by direct casting and result in lightweight, fully triangulated truss-like configurations which provide strength and stiffness [2]. The earliest realizations of lattice block were made from A1 and steels, primarily under funding from the US Navy [3]. This work also showed that the mechanical efficiency (eg., specific stiffness) of lattice block structures approached that of honeycomb structures [2]. The lattice architectures are also less anisotropic, and the investment casting route should provide a large advantage in cost and temperature capability over honeycombs which are limited to alloys that can be processed into foils. Based on this early work, a program was initiated to determine the feasibility of extending the high temperature superalloy lattice block [3]. The objective of this effort was to provide an alternative to intermetallics and composites in achieving a lightweight high temperature structure without sacrificing the damage tolerance and moderate cost inherent in superalloys. To establish the feasibility of the superalloy lattice block concept, work was performed in conjunction with JAMCORP, Inc. Billerica, MA, to produce a number of lattice block panels from both IN71 8 and Mar-M247.

  20. Permeability of hydrogen isotopes through nickel-based alloys

    SciTech Connect

    Edge, E.M.; Mitchell, D.J.

    1983-04-01

    Permeabilities and diffusivities of deuterium in several nickel-based alloys were measured in this investigation. Measurements were made by the gas-phase breakthrough technique in the temperature range 200 to 450/sup 0/C with applied pressures ranging from 1 to 100 kPa. The results were extrapolated to predict the permeabilities (K) of the alloys at room temperature. The alloy with the smallest deuterium permeability is Carpenter 49, for which K = 4.3 x 10/sup -18/ mol s/sup -1/ m/sup -1/ Pa/sup -//sup 1/2/ at 22/sup 0/C. The permeability of deuterium in Kovar or Ceramvar is about 80% greater than that for Carpenter 49. Premeabilities of Inconel 625, Inconel 718, Inconel 750 and Monel K-500 are all equal to about 5 x 10/sup -17/ mol m/sup -1/ s/sup -1/ Pa/sup -//sup 1/2/ at 22/sup 0/C. The validity (from a statistical standpoint) of the extrapolation of the permeabilities to room temperature is considered in detail. Published permeabilities of stainless steels and nickel-iron alloys are also reviewed. The greatest differences in permeabilities among the nickel-based alloys appear to be associated with the tendency for some alloys to form protective oxide layers. Permeabilities of deuterium through laminates containing copper are smaller than for any of the iron-nickel alloys.

  1. Stress corrosion crack tip microstructure in nickel-based alloys

    SciTech Connect

    Shei, S.A.; Yang, W.J.

    1994-04-01

    Stress corrosion cracking behavior of several nickel-base alloys in high temperature caustic environments has been evaluated. The crack tip and fracture surfaces were examined using Auger/ESCA and Analytical Electron Microscopy (AEM) to determine the near crack tip microstructure and microchemistry. Results showed formation of chromium-rich oxides at or near the crack tip and nickel-rich de-alloying layers away from the crack tip. The stress corrosion resistance of different nickel-base alloys in caustic may be explained by the preferential oxidation and dissolution of different alloying elements at the crack tip. Alloy 600 (UNS N06600) shows good general corrosion and intergranular attack resistance in caustic because of its high nickel content. Thermally treated Alloy 690 (UNS N06690) and Alloy 600 provide good stress corrosion cracking resistance because of high chromium contents along grain boundaries. Alloy 625 (UNS N06625) does not show as good stress corrosion cracking resistance as Alloy 690 or Alloy 600 because of its high molybdenum content.

  2. Superalloy for high-temperature hydrogen environmental applications

    NASA Technical Reports Server (NTRS)

    McKannan, Eugene C. (Inventor); McPherson, William B. (Inventor); Ahmed, Shaffiq (Inventor); Chandler, Shirley S. (Inventor)

    1991-01-01

    A nickel-based superalloy is provided which is resistant to deterioration in hydrogen at high operating temperatures and pressures, and which thus can be used in hydrogen-fueled spacecraft such as the Space Shuttle. The superalloy is characterized by a two-phase microstructure and consists of a gamma-prime precipitated phase in a gamma matrix. The gamma matrix phase is a primary solid solution and the gamma precipitated phase will be an intermetallic compound of the type A.sub.3 B, such as nickel aluminide or titanide. Both phases are coherent, ordered, and compatible, and thus will retain most of their strength at elevated temperatures. The alloy consists essentially of (by weight): Ni 50-60%, Cr 10-20%, Al 2-6%, Co 2-5%, Ti 3-8%, W 5-12%, Mo 5-10%, Nb 1-3%, wherein the ratio W/MO is approximately equal to 1, and Ti/Al ranges from about 1 to about 2.

  3. Oxy-Combustion Environment Characterization: Fire- and Steam-Side Corrosion in Advanced Combustion

    SciTech Connect

    G. R. Holcomb; J. Tylczak; G. H. Meier; B. S. Lutz; N. M. Yanar; F. S. Pettit; J. Zhu; A. Wise; D. E. Laughlin; S. Sridhar

    2012-09-25

    Oxy-fuel combustion is burning a fuel in oxygen rather than air. The low nitrogen flue gas that results is relatively easy to capture CO{sub 2} from for reuse or sequestration. Corrosion issues associated with the environment change (replacement of much of the N{sub 2} with CO{sub 2} and higher sulfur levels) from air- to oxy-firing were examined. Alloys studied included model Fe-Cr alloys and commercial ferritic steels, austenitic steels, and nickel base superalloys. The corrosion behavior is described in terms of corrosion rates, scale morphologies, and scale/ash interactions for the different environmental conditions. Additionally, the progress towards laboratory oxidation tests in advanced ultra-supercritical steam is updated.

  4. Microstructural evolution in advanced boiler materials for ultra-supercritical coal power plants

    NASA Astrophysics Data System (ADS)

    Wu, Quanyan

    The goal of improving the efficiency of pulverized coal powerplants has been pursued for decades. The need for greater efficiency and reduced environmental impact is pushing utilities to ultra supercritical conditions (USC), i.e. steam temperatures approaching 760°C under a stress of 35 MPa. The long-term creep strength and environmental resistance requirements imposed by these conditions are clearly beyond the capacity of the currently used ferritic steels and other conventional alloys. As part of a large DOE-funded consortium, new and existing materials based on advanced austenitic stainless steels and nickel base superalloys are being evaluated for these very demanding applications. In the present work, the nickel base superalloys of Inconel 617, CCA617, Haynes 230 and Inconel 740, and austenitic alloys Super 304H and HR6W, were evaluated on their microstructural properties over elevated temperature ageing and creep rupture conditions. The materials were aged for different lengths of time at temperatures relevant to USC applications, i.e., in the range from 700 to 800°C. The precipitation behaviors, namely of the gamma', carbides and eta phase in some conditions in nickel base superalloys, carbides in Haynes 230, Cu-rich precipitates in Super 304H and Laves phase particles in HR6W, were studied in detail using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and related analytical techniques. Particular attention has been given on the structure, morphology and compositional distinctiveness of various phases (including gamma, gamma', carbides, secondary phase precipitates, and other types of particles) and their nature, dislocation structures and other types of defects. The results were presented and discussed in light of associated changes in microhardness in the cases of aged samples, and in close reference to mechanical testing (including tensile and creep rupture tests) wherever available. Several mechanical strengthening

  5. Application of superalloy powder metallurgy for aircraft engines

    NASA Technical Reports Server (NTRS)

    Dreshfield, R. L.; Miner, R. V., Jr.

    1980-01-01

    The results of the Materials for Advanced Turbine Engines (MATE) program initiated by NASA are presented. Mechanical properties comparisons are made for superalloy parts produced by as-HIP powder consolidation and by forging of HIP consolidated billets. The effect of various defects on the mechanical properties of powder parts are shown.

  6. Noburnium: Systems design of niobium superalloys

    NASA Astrophysics Data System (ADS)

    Misra, Abhijeet

    2005-11-01

    A systems-based approach, integrating quantum mechanical calculations with efficient experimentation, was employed to design niobium-based superalloys. The microstructural concept of gamma-gamma' nickel-based superalloys was adopted, where, the coherent gamma ' aluminides act both as the strengthening phase and a source of aluminum for Al2O3 passivation. Building on previous research, the selected bcc-type ordered aluminide was L2 1 structured Pd2HfAl phase. Comprehensive phase relations were measured on Nb-Pd-Hf-Al prototype alloys, and key tie-tetrahedra were identified. Aluminide precipitation in a bcc matrix was demonstrated in designed Nb+Pd2HfAl alloys. Thermodynamic databases were developed by integrating first-principles calculations with measured phase relations. Atomic volume models were developed for the bcc matrix and the Pd2HfAl phase and matrix elements which would reduce lattice misfit were identified. An experimental 2-phase alloy demonstrated a misfit of 3%. A modified Wagner's model was used to predict the required transient properties to form external Al2O3. The principal oxidation design goal was to decrease the oxygen permeability ( NSOx DO ) divided by the aluminum diffusivity (DAl) by 5 orders of magnitude. A multicomponent mobility database was developed to predict the diffusivities. Guided by first-principles calculations the effect of alloying elements on the oxygen diffusivity in Nb was measured, and the mobility database was experimentally validated. Based on the mobility database, it was found that increasing Al solubility in the bcc matrix greatly increased Al diffusivity. Alloying elements were identified that would increase Al solubility in the bcc matrix. Prototype alloys were prepared and the best oxidation performance was exhibited by a bcc+Nb2Al Nb-Hf-Al alloy, which exhibited parabolic oxidation behavior at 1300°C. The alloy was shown to have achieved the required 5 orders of magnitude reduction in the design parameter. The

  7. Profile Grinding of Superalloys with Ultrafine-Crystalline cBN Wheels

    NASA Astrophysics Data System (ADS)

    Ichida, Yoshio; Sato, Ryunosuke; Morimoto, Yoshitaka; Inoue, Yoshihiro

    This paper deals with the grinding characteristics of newly developed polycrystalline cBN (cBN-U) abrasives in creep feed profile grinding of nickel-based superalloys. Experiments for producing a V-shaped groove on a flat surface in one pass by creep feed grinding have been carried out using the new polycrystalline cBN-U and representative conventional cBN (cBN-B) grits. When grinding with cBN-U abrasives, both radial wear and profile wear are less, and hence the grinding ratio is around 10 times higher than that with the conventional cBN-B abrasives. Grinding forces in grinding with cBN-U abrasives are reduced by 20-30% compared with those in Grinding with cBN-B abrasives. The cBN-U abrasive is suitable for the applications with a high dimensional accuracy in creep feed profile grinding for nickel-based superalloys, because it gives less profile wear, and hence better form retention, than conventional cBN abrasive.

  8. Fatigue Resistance of the Grain Size Transition Zone in a Dual Microstructure Superalloy Disk

    NASA Technical Reports Server (NTRS)

    Gabb, T. P.; Kantzos, P. T.; Telesman, J.; Gayda, J.; Sudbrack, C. K.; Palsa, B. S.

    2010-01-01

    Mechanical property requirements vary with location in nickel-based superalloy disks. To maximize the associated mechanical properties, heat treatment methods have been developed for producing tailored microstructures. In this study, a specialized heat treatment method was applied to produce varying grain microstructures from the bore to the rim portions of a powder metallurgy processed nickel-based superalloy disk. The bore of the contoured disk consisted of fine grains to maximize strength and fatigue resistance at lower temperatures. The rim microstructure of the disk consisted of coarse grains for maximum resistance to creep and dwell crack growth at high temperatures up to 704 C. However, the fatigue resistance of the grain size transition zone was unclear, and needed to be evaluated. This zone was located as a band in the disk web between the bore and rim. Specimens were extracted parallel and transverse to the transition zone, and multiple fatigue tests were performed at 427 and 704 C. Mean fatigue lives were lower at 427 C than for 704 C. Specimen failures often initiated at relatively large grains, which failed on crystallographic facets. Grain size distributions were characterized in the specimens, and related to the grains initiating failures as well as location within the transition zone. Fatigue life decreased with increasing maximum grain size. Correspondingly, mean fatigue resistance of the transition zone was slightly higher than that of the rim, but lower than that of the bore. The scatter in limited tests of replicates was comparable for all transition zone locations examined.

  9. Fiber reinforced superalloys

    NASA Technical Reports Server (NTRS)

    Petrasek, Donald W.; Signorelli, Robert A.; Caulfield, Thomas; Tien, John K.

    1987-01-01

    Improved performance of heat engines is largely dependent upon maximum cycle temperatures. Tungsten fiber reinforced superalloys (TFRS) are the first of a family of high temperature composites that offer the potential for significantly raising hot component operating temperatures and thus leading to improved heat engine performance. This status review of TFRS research emphasizes the promising property data developed to date, the status of TFRS composite airfoil fabrication technology, and the areas requiring more attention to assure their applicability to hot section components of aircraft gas turbine engines.

  10. Microstructural study of the nickel-base alloy WAZ-20 using qualitative and quantitative electron optical techniques

    NASA Technical Reports Server (NTRS)

    Young, S. G.

    1973-01-01

    The NASA nickel-base alloy WAZ-20 was analyzed by advanced metallographic techniques to qualitatively and quantitatively characterize its phases and stability. The as-cast alloy contained primary gamma-prime, a coarse gamma-gamma prime eutectic, a gamma-fine gamma prime matrix, and MC carbides. A specimen aged at 870 C for 1000 hours contained these same constituents and a few widely scattered high W particles. No detrimental phases (such as sigma or mu) were observed. Scanning electron microscope, light metallography, and replica electron microscope methods are compared. The value of quantitative electron microprobe techniques such as spot and area analysis is demonstrated.

  11. Comparative coarsening kinetics of gamma prime precipitates in nickel and cobalt base superalloys

    NASA Astrophysics Data System (ADS)

    Meher, Subhashish

    The increasing technological need to push service conditions of structural materials to higher temperatures has motivated the development of several alloy systems. Among them, superalloys are an excellent candidate for high temperature applications because of their ability to form coherent ordered precipitates, which enable the retention of high strength close to their melting temperature. The accelerated kinetics of solute diffusion, with or without an added component of mechanical stress, leads to coarsening of the precipitates, and results in microstructural degradation, limiting the durability of the materials. Hence, the coarsening of precipitates has been a classical research problem for these alloys in service. The prolonged hunt for an alternative of nickel base superalloys with superior traits has gained hope after the recent discovery of Co-Al-W based alloys, which readily form high temperature gamma' precipitates, similar to Ni base superalloys. In the present study, coarsening behavior of gamma' precipitates in Co-10Al-10W (at. %) has been carried out at 800°C and 900°C. This study has, for the first time, obtained critical coarsening parameters in cobalt-base alloys. Apart from this, it has incorporated atomic scale compositional information across the gamma/gamma' interfaces into classical Cahn-Hilliard model for a better model of coarsening kinetics. The coarsening study of gamma' precipitates in Ni-14Al-7 Cr (at. %) has shown the importance of temporal evolution of the compositional width of the gamma/gamma' interfaces to the coarsening kinetics of gamma' precipitates. This study has introduced a novel, reproducible characterization method of crystallographic study of ordered phase by coupling of orientation microscopy with atom probe tomography (APT). Along with the detailed analysis of field evaporation behaviors of Ni and Co superalloys in APT, the present study determines the site occupancy of various solutes within ordered gamma' precipitates

  12. Rafting in superalloys

    SciTech Connect

    Nabarro, F.R.N.

    1996-03-01

    The phenomenon of rafting in superalloys is described, with particular reference to modern superalloys with a high volume fraction of the particulate {gamma}{prime} phase. It is shown that in the elastic regime, the thermodynamic driving force for rafting is proportional to the applied stress, to the difference between the lattice parameters of the {gamma} matrix and the {gamma}{prime} particles, and to the difference of their elastic constants. A qualitative argument gives the sign of this driving force, which agrees with that determined by Pineau for a single isolated particle. Drawing on the work of Pollock and Argon and of Socrate and Parks, it is shown that after a plastic strain of the sample of order 2 {times} 10{sup {minus}4}, the driving force is proportional to the product of the applied stress and the lattice misfit, in agreement with the results of the calculations of Socrate and Parks. The rate of rafting is controlled by the diffusion of alloying elements. Here, the tendency of large atoms to move from regions of high hydrostatic pressure to those of low may outweigh the influence of concentration gradients. The deformation of the sample directly produced by rafting is small, of order 4.5 {times} 10{sup {minus}4}. The rafted structure is resistant to creep under low stresses at high temperatures. Under most experimental conditions at relatively high stresses, rafting accelerates creep; this effect may be less pronounced at the small strains acceptable under operational conditions.

  13. Rafting in Superalloys

    NASA Astrophysics Data System (ADS)

    Nabarro, Frank R. N.

    1996-03-01

    The phenomenon of rafting in superalloys is described, with particular reference to modern superalloys with a high volume fraction of the particulate γ’ phase. It is shown that in the elastic regime, the thermodynamic driving force for rafting is proportional to the applied stress, to the difference between the lattice parameters of the γ matrix and the γ’ particles, and to the difference of their elastic constants. A qualitative argument gives the sign of this driving force, which agrees with that determined by Pineau for a single isolated particle. Drawing on the work of Pollock and Argon and of Socrate and Parks, it is shown that after a plastic strain of the sample of order 2 × 10-4, the driving force is proportional to the product of the applied stress and the lattice misfit, in agreement with the results of the calculations of Socrate and Parks. The rate of rafting is controlled by the diffusion of alloying elements. Here, the tendency of large atoms to move from regions of high hydrostatic pressure to those of low may outweigh the influence of concentration gradients. The deformation of the sample directly produced by rafting is small, of order 4.5 × 10-4. The rafted structure is resistant to creep under low stresses at high temperatures. Under most experimental conditions at relatively high stresses, rafting accelerates creep; this effect may be less pronounced at the small strains acceptable under operational conditions.

  14. Effects of silicon additions on oxidation and mechanical behavior of the nickel-base superalloy B-1900

    NASA Technical Reports Server (NTRS)

    Miner, R. V., Jr.; Lowell, C. E.

    1975-01-01

    Test specimens with nominal additions of Si were tested in oxidation, thermal fatigue, sulfidation, tension, and stress rupture, and were also extensively studied metallographically. Alloy B-1900 modified with 0.6- or 1.2-wt% Si exhibited oxidation resistance equivalent to that of aluminide-coated B-1900 during cyclic, high-gas-velocity oxidation tests. Resistances to thermal fatigue and sulfidation were improved by the Si additions, but were not superior to aluminide-coated B-1900. Stress-rupture tests at 1000 C of specimens given the standard heat treatment to simulate an aluminide coating cycle showed Si to be detrimental. However, application of another heat treatment increased the rupture life of the alloy with 0.6-wt% Si to that of the unmodified B-1900 given the standard heat treatment.

  15. Improvement in cyclic oxidation of the nickel-base superalloy B-1900 by addition of one percent silicon

    NASA Technical Reports Server (NTRS)

    Lowell, C. E.; Miner, R. V.

    1973-01-01

    Cast B-1900 with and without 1 weight percent Si was subjected to cyclic oxidation at 1000 and 1100 C in air for 700 and 200 hours, respectively. The results were judged by specific weight change, metallography and X-ray diffraction. Si was found to be of significant value in reducing oxidation attack, probably by increasing scale adherence.

  16. The role of microstructure on deformation and damage mechanisms in a Nickel-based superalloy at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Maciejewski, Kimberly E.

    The overall objective of this research work is the development and implementation of a mechanistic based time-dependent crack growth model which considers the role of creep, fatigue and environment interactions on both the bulk and the grain boundary phase in ME3 disk material. The model is established by considering a moving crack tip along a grain boundary path in which damage events are described in terms of the grain boundary deformation and related accommodation processes. Modeling of these events was achieved by adapting a cohesive zone approach (an interface with internal singular surfaces) in which the grain boundary dislocation network is smeared into a Newtonian fluid element. The deformation behavior of this element is controlled by the continuum in both far field (internal state variable model) and near field (crystal plasticity model) and the intrinsic grain boundary viscosity which is characterized by microstructural parameters, including grain boundary precipitates and morphology, and is able to define the mobility of the element by scaling the motion of dislocations into a mesoscopic scale. Within the cohesive zone element, the motion of gliding dislocations in the tangential direction relates to the observed grain boundary sliding displacement, the rate of which is limited by the climb of dislocations over grain boundary obstacles. Effects of microstructural variation and orientation of the surrounding continuum are embedded in the tangential stress developing in the grain boundary. The mobility of the element in the tangential direction (i.e. by grain boundary sliding) characterizes the accumulation of irreversible displacement while the vertical movement (migration), although present, is assumed to alter stress by relaxation and, thus, is not considered a contributing factor in the damage process. This process is controlled by the rate at which the time-dependent sliding reaches a critical displacement and as such, a damage criterion is introduced by considering the mobility limit in the tangential direction leading to strain incompatibility and failure. This limit is diminished by environmental effects which are introduced as a dynamic embrittlement process that hinders grain boundary mobility due to oxygen diffusion. The concepts described herein indicate that implementation of the cohesive zone model requires the knowledge of the grain boundary external and internal deformation fields. The external field is generated by developing and coupling two continuum constitutive models including (i) a microstructure-explicit coarse scale crystal plasticity model with strength provided by tertiary and secondary gamma' precipitates. This scale is appropriate for the representation of the continuum region at the immediate crack tip, and (ii) a macroscopic internal state variable model for the purpose of modeling the response of the far field region located several grains away from the crack path. The hardening contributions of the gamma' precipitates consider dislocation/precipitate interactions in terms of gamma' particles shearing and/or Orowan by-passing mechanisms. The material parameters for these models are obtained from results of low cycle fatigue tests which were performed at three temperatures; 650, 704 and 760°C. Furthermore, a series of microstructure controlled experiments were carried out in order to develop and validate the microstructure dependency feature of the continuum constitutive models. The second requirement in the implementation of the cohesive zone model is a grain boundary deformation model which has been developed, as described above, on the basis of viscous flow rules of the boundary material. This model is supported by dwell crack growth experiments carried out at the three temperatures mentioned above, in both air and vacuum environments. Results of these tests have identified the frequency range in which the grain boundary cohesive zone model is applicable and also provided data to calculate the grain boundary activation energy as well as identifying the relative contributions of creep and environment in the critical sliding displacement leading to failure. Validation of the cohesive zone model has been carried out by comparing the simulated crack growth data with that obtained experimentally. This comparison is used to optimize the different model components and to provide a route to assess the relative significance of each of these components in relation to the intergranular damage associated with dwell fatigue crack growth in the ME3 alloy. For this purpose, a set of case studies were performed in order to illustrate the sensitivity of the cohesive zone model to variations in microstructure parameters (gamma ' statistics and grain boundary morphology) examined within the range of temperatures utilized in this study.

  17. Hydrogen effects on low-cycle fatigue of the single-crystal nickel-base superalloy CMSX-2

    NASA Technical Reports Server (NTRS)

    Dollar, M.; Bernstein, I. M.; Kromp, W.; Domnanovitch, A.; Pinczolits, H.

    1991-01-01

    The effects of hydrogen on the low-cycle fatigue behavior of CMSX-2 (001)-oriented single crystals were examined. Fatigue tests were conducted under constant plastic strain amplitude control. Cyclic stress-strain curves and fatigue life data at different plastic strain amplitudes were determined for hydrogen-free and hydrogen-charged specimens. Two charging procedures, leading to different hydrogen concentrations, were applied. Hydrogen was found to decrease significantly the number of cycles to failure under the various experimental conditions. The increasing hydrogen concentration and ratio of the hydrogen to nonhydrogen-containing volume were found to shorten fatigue life in hydrogen-charged specimens. Based on the analysis of cyclic stress-strain curves and optical and transmission electron microscopy, it was established that hydrogen enhanced strain localization and promoted crystallographic stage I cracking, leading to embrittlement.

  18. Microstructure Evolution and Rapid Solidification Behavior of Blended Nickel-Based Superalloy Powders Fabricated by Laser Powder Deposition

    NASA Astrophysics Data System (ADS)

    Tian, Y.; Gauvin, R.; Brochu, M.

    2016-07-01

    Laser powder deposition was performed on a substrate of Inconel 738 using blended powders of Mar M247 and Amdry DF3 with a ratio of 4:1 for repairing purposes. In the as-deposited condition, continuous secondary phases composed of γ-Ni3B eutectics and discrete (Cr, W)B borides were observed in inter-dendritic regions, and time-dependent nucleation simulation results confirmed that (Cr, W)B was the primary secondary phase formed during rapid solidification. Supersaturated solid solution of B was detected in the γ solid solution dendritic cores. The Kurz-Giovanola-Trivedi model was performed to predict the interfacial morphology and correlate the solidification front velocity (SFV) with dendrite tip radius. It was observed from high-resolution scanning electron microscopy that the dendrite tip radius of the upper region was in the range of 15 to 30 nm, which yielded a SFV of approx 30 cm/s. The continuous growth model for solute trapping behavior developed by Aziz and Kaplan was used to determine that the effective partition coefficient of B was approximately 0.025. Finally, the feasibility of the modeling results were rationalized with the Clyne-Kurz segregation simulation of B, where Clyne-Kurz prediction using a partition coefficient of 0.025 was in good agreement with the electron probe microanalysis results.

  19. Directional solidification of large cross-section nickel-base superalloy castings via liquid-metal cooling

    NASA Astrophysics Data System (ADS)

    Elliott, Andrew J.

    The drive for higher efficiency in very large industrial gas turbines (IGTs) used in power generation applications has led to the need for directional solidification of large cross-section components, such as turbine blades, used in the hot gas path sections of the IGTs. The Bridgman directional solidification technique, which is currently used to produce these components, has been optimized for much smaller aero-engine components. The scale-up of this technique to produce large parts has resulted in numerous problems, and consequently low casting yield, which can all be related to the limited cooling capability of the Bridgman process. In this dissertation, a higher cooling efficiency process, liquid-metal cooling (LMC) using Sn as the cooling medium, has been evaluated for improved capability to cast large cross-section components. A series of castings were made for direct comparison using both the conventional Bridgman and the high thermal gradient LMC processes. Casting conditions were selected to simulate the state of the art for the Bridgman method and to assess the limits of casting with the less familiar LMC method. The experiments were evaluated through thermocouple analyses of casting conditions and post-casting analyses of grain defects, microstructural features, and mechanical behavior. Additionally, a finite element model of the solidification process was developed to further elucidate casting conditions. The casting parameters and elements of the LMC process that had the greatest influence on casting conditions were determined. Results indicated that the LMC process is capable of significantly enhancing cooling efficiency during directional solidification of large cross-section components. The enhanced cooling allowed much faster solidification withdrawal rates and resulted in substantially refined cast microstructure. The LMC process eliminated freckle-type defects in all cases and considerably reduced other casting defects under optimal conditions. It also was determined that the location of the solidification front during the LMC process is a crucial parameter that must be controlled to produce a high quality casting. Additionally, a floating thermal baffle used with the LMC-Sn process was established as an indispensable element of the LMC process.

  20. Nickel Based Superalloy with Improved Weldability and Oxidation Resistance. Fourth quarterly report for the period July 1999 to October 1999

    SciTech Connect

    George Simkovich; Eric Whitney

    1999-11-01

    The aim of this project is to determine and provide technical and economic data to a commercial end user of the alloy so that a full-scale alloy qualification program can be defined and implemented. The object of this project is to define the compositional range for a new alloy that is suitable for evaluation and qualification by a commercial enterprise. Alloy properties that will need to be determined include weldability, oxidation resistance, creep strength, resistance to thermo-mechanical fatigue, microstructure stability, and cost. Test results will be used to finalize the compositional range of an alloy that will undergo a rigorous qualification process.

  1. The role of microstructure on deformation and damage mechanisms in a Nickel-based superalloy at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Maciejewski, Kimberly E.

    The overall objective of this research work is the development and implementation of a mechanistic based time-dependent crack growth model which considers the role of creep, fatigue and environment interactions on both the bulk and the grain boundary phase in ME3 disk material. The model is established by considering a moving crack tip along a grain boundary path in which damage events are described in terms of the grain boundary deformation and related accommodation processes. Modeling of these events was achieved by adapting a cohesive zone approach (an interface with internal singular surfaces) in which the grain boundary dislocation network is smeared into a Newtonian fluid element. The deformation behavior of this element is controlled by the continuum in both far field (internal state variable model) and near field (crystal plasticity model) and the intrinsic grain boundary viscosity which is characterized by microstructural parameters, including grain boundary precipitates and morphology, and is able to define the mobility of the element by scaling the motion of dislocations into a mesoscopic scale. Within the cohesive zone element, the motion of gliding dislocations in the tangential direction relates to the observed grain boundary sliding displacement, the rate of which is limited by the climb of dislocations over grain boundary obstacles. Effects of microstructural variation and orientation of the surrounding continuum are embedded in the tangential stress developing in the grain boundary. The mobility of the element in the tangential direction (i.e. by grain boundary sliding) characterizes the accumulation of irreversible displacement while the vertical movement (migration), although present, is assumed to alter stress by relaxation and, thus, is not considered a contributing factor in the damage process. This process is controlled by the rate at which the time-dependent sliding reaches a critical displacement and as such, a damage criterion is introduced by considering the mobility limit in the tangential direction leading to strain incompatibility and failure. This limit is diminished by environmental effects which are introduced as a dynamic embrittlement process that hinders grain boundary mobility due to oxygen diffusion. The concepts described herein indicate that implementation of the cohesive zone model requires the knowledge of the grain boundary external and internal deformation fields. The external field is generated by developing and coupling two continuum constitutive models including (i) a microstructure-explicit coarse scale crystal plasticity model with strength provided by tertiary and secondary gamma' precipitates. This scale is appropriate for the representation of the continuum region at the immediate crack tip, and (ii) a macroscopic internal state variable model for the purpose of modeling the response of the far field region located several grains away from the crack path. The hardening contributions of the gamma' precipitates consider dislocation/precipitate interactions in terms of gamma' particles shearing and/or Orowan by-passing mechanisms. The material parameters for these models are obtained from results of low cycle fatigue tests which were performed at three temperatures; 650, 704 and 760°C. Furthermore, a series of microstructure controlled experiments were carried out in order to develop and validate the microstructure dependency feature of the continuum constitutive models. The second requirement in the implementation of the cohesive zone model is a grain boundary deformation model which has been developed, as described above, on the basis of viscous flow rules of the boundary material. This model is supported by dwell crack growth experiments carried out at the three temperatures mentioned above, in both air and vacuum environments. Results of these tests have identified the frequency range in which the grain boundary cohesive zone model is applicable and also provided data to calculate the grain boundary activation energy as well as identifying the relative contributions o

  2. Nickel based superalloy with improved weldability and oxidation resistance. Fifth quarterly report for the period November 1999 - January 2000

    SciTech Connect

    Simkovich, George; Whitney, Eric

    2000-02-29

    This program is part of the US Department of Energy (DOE) Energy Related Inventions Program (ERIP). The purpose of ERIP is to promote and facilitate the development of energy saving technologies that may not otherwise be developed solely by commercial enterprises. The program has been highly successful in achieving its mission. The aim of this project is to determine and provide technical and economic data to a commercial end user of the alloy so that a full-scale alloy qualification program can be defined and implemented. The object of this project is to define the compositional range for a new alloy that is suitable for evaluation and qualification by a commercial enterprise. Alloy properties that will need to be determined include weldability, oxidation resistance, creep strength, resistance to thermo-mechanical fatigue, microstructure stability, and cost. Test results will be used to finalize the compositional range of an alloy that will undergo a rigorous qualification process.

  3. Effects of chromium and aluminum on mechanical and oxidation properties of iron-nickel-base superalloys based on CG-27

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.

    1985-01-01

    The effects of chromium and aluminum on the mechanical and oxidation properties of a series of gamma-prime-strengthened alloys based on CG-27 were studied. Gamma-prime dispersion and solid-solution strengthening were the principal modes of alloy strengthening. The oxidation attack parameter K sub a decreased with increasing Cr and Al contents for each alloy group based on Al content. As a group, alloys with 3 wt % Al had the lowest attack parameters. Therefore, 3 wt % is the optimum level of Al for parabolic oxidation behavior. Spalling, due to diffusion-induced grain growth, was controlled by the overall Cr and Al levels. The alloy with 4 wt % Cr and 3 wt % Al had stress-rupture properties superior to those of the base alloy, CG-27, and maintained parabolic oxidation behavior while the Cr content was reduced by two-thirds of its value in cast CG-27.

  4. Role of molybdenum in the Na sub 2SO sub 4 induced corrosion of superalloys at high temperatures

    NASA Technical Reports Server (NTRS)

    Misra, A. K.

    1986-01-01

    Sodium sulfate induced corrosion of a molybdenum containing nickel-base superalloy, Udimet 700, was studied in laboratory furnace tests and in a high velocity (Mach 0.3) burner rig. The effect of SO2 content in the atmosphere on the corrosion behavior in the laboratory furnace tests was determined. Catastrophic corrosion occurs only when the melt contains MoO3 in addition to Na2SO4 and Na2MoO4. The conditions under which catastrophic corrosion occurs are identified and a mechanism is described to explain the catastrophic corrosion.

  5. Boride Zone Formation in Transient Liquid Phase Bonding of Pairings of Parent Superalloy Materials with Different Compositions and Grain Structures

    NASA Astrophysics Data System (ADS)

    Steuer, S.; Singer, R. F.

    2013-05-01

    Two nickel-base superalloys are joined via transient liquid phase (TLP) bonding with boron as the MPD. Boride formation is observed in the parent materials at some distance from the solid/liquid interface. The boron concentration profile over the joint is measured with glow discharge optical emission spectroscopy (GDOES). Boron concentration peaks are observed corresponding to the boride formation. Boron distribution is discussed on the basis of theoretical predictions in the literature. It is concluded that diffusion of another element is necessary to explain the results with the second element influencing the solubility of boron.

  6. Cyclic-loading-induced Accumulation of the Geometrically Necessary Dislocations Near the Grain Boundaries of the Ni-Based Superalloy

    SciTech Connect

    Huang, E-Wen; Barabash, Rozaliya; Ice, Gene E; Liu, Wenjun; Liu, Yee-Lang; Kai, Ji-Jung; Liaw, Peter K

    2009-01-01

    In this study, a nickel-based polycrystalline superalloy is subjected to cyclic loading. The fatigue-induced microstructure is characterized by novel polychromatic X-ray microdiffraction (PXM) together with in-situ neutron diffraction and TEM. In-situ neutron strain measurements reveal two distinct stages of the fatigue damage. Three-dimensional (3D) spatially-resolved PXM micro-Laue measurements demonstrate the development of local texture and formation of geometrically necessary dislocations near the grain boundaries, which is accompanied by lattice rotations and grain subdivisions. The PXM results are in agreement with the in-situ neutron diffraction and TEM results.

  7. Fatigue Behavior and Deformation Mechanisms in Inconel 718 Superalloy Investigated

    NASA Technical Reports Server (NTRS)

    2005-01-01

    The nickel-base superalloy Inconel 718 (IN 718) is used as a structural material for a variety of components in the space shuttle main engine (SSME) and accounts for more than half of the total weight of this engine. IN 718 is the bill-of-material for the pressure vessels of nickel-hydrogen batteries for the space station. In the case of the space shuttle main engine, structural components are typically subjected to startup and shutdown load transients and occasional overloads in addition to high-frequency vibratory loads from routine operation. The nickel-hydrogen battery cells are prooftested before service and are subjected to fluctuating pressure loads during operation. In both of these applications, the structural material is subjected to a monotonic load initially, which is subsequently followed by fatigue. To assess the life of these structural components, it is necessary to determine the influence of a prior monotonic load on the subsequent fatigue life of the superalloy. An insight into the underlying deformation and damage mechanisms is also required to properly account for the interaction between the prior monotonic load and the subsequent fatigue loading. An experimental investigation was conducted to establish the effect of prior monotonic straining on the subsequent fatigue behavior of wrought, double-aged, IN 718 at room temperature. First, monotonic strain tests and fully-reversed, strain-controlled fatigue tests were conducted on uniform-gage-section IN 718 specimens. Next, fully reversed fatigue tests were conducted under strain control on specimens that were monotonically strained in tension. Results from this investigation indicated that prior monotonic straining reduced the fatigue resistance of the superalloy particularly at the lowest strain range. Some of the tested specimens were sectioned and examined by transmission electron microscopy to reveal typical microstructures as well as the active deformation and damage mechanisms under each of

  8. Innovative technologies for powder metallurgy-based disk superalloys: Progress and proposal

    NASA Astrophysics Data System (ADS)

    Chong-Lin, Jia; Chang-Chun, Ge; Qing-Zhi, Yan

    2016-02-01

    Powder metallurgy (PM) superalloys are an important class of high temperature structural materials, key to the rotating components of aero engines. In the purview of the present challenges associated with PM superalloys, two novel approaches namely, powder preparation and the innovative spray-forming technique (for making turbine disk) are proposed and studied. Subsequently, advanced technologies like electrode-induction-melting gas atomization (EIGA), and spark-plasma discharge spheroidization (SPDS) are introduced, for ceramic-free superalloy powders. Presently, new processing routes are sought after for preparing finer and cleaner raw powders for disk superalloys. The progress of research in spray-formed PM superalloys is first summarized in detail. The spray-formed superalloy disks specifically exhibit excellent mechanical properties. This paper reviews the recent progress in innovative technologies for PM superalloys, with an emphasis on new ideas and approaches, central to the innovation driving techniques like powder processing and spray forming. Project supported by the National Natural Science Foundation of China (Grant Nos. 50974016 and 50071014).

  9. Coarsening in high volume fraction nickel-base alloys

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Nathal, M. V.

    1990-01-01

    The coarsening behavior of the gamma-prime precipitate has been examined in high volume fraction nickel-base alloys aged at elevated temperatures for times of up to 5000 h. Although the cube rate law was observed during coarsening, none of the presently available coarsening theories showed complete agreement with the experimental particle size distributions (PSDs). These discrepancies were thought to be due to elastic coherency strains which were not considered by the available models. Increasing the Mo content significantly influenced the PSDs and decreased the coarsening rate of the gamma-prime cubes, as a result of increasing the magnitude of the lattice mismatch. After extended aging times, the gamma-prime cubes underwent massive coalescence into plates at a rate which was much faster than the cuboidal coarsening rate. Once the gamma-prime plates were formed, further coarsening was not observed, and this stabilization of the microstructure was attributed to the development of dislocation networks at the gamma-gamma-prime interfaces.

  10. Tungsten wire-nickel base alloy composite development

    NASA Technical Reports Server (NTRS)

    Brentnall, W. D.; Moracz, D. J.

    1976-01-01

    Further development and evaluation of refractory wire reinforced nickel-base alloy composites is described. Emphasis was placed on evaluating thermal fatigue resistance as a function of matrix alloy composition, fabrication variables and reinforcement level and distribution. Tests for up to 1,000 cycles were performed and the best system identified in this current work was 50v/o W/NiCrAlY. Improved resistance to thermal fatigue damage would be anticipated for specimens fabricated via optimized processing schedules. Other properties investigated included 1,093 C (2,000 F) stress rupture strength, impact resistance and static air oxidation. A composite consisting of 30v/o W-Hf-C alloy fibers in a NiCrAlY alloy matrix was shown to have a 100-hour stress rupture strength at 1,093 C (2,000 F) of 365 MN/square meters (53 ksi) or a specific strength advantage of about 3:1 over typical D.S. eutectics.

  11. HIP clad nickel base Alloy 625 for deep sour wells

    SciTech Connect

    Uhl, W.K.; Pendley, M.R.

    1984-05-01

    The hot isostatic pressing (HIP) process was used to clad nickel base Alloy 625 to AISI 4130 low alloy steel. The performance of the HIP clad material in the corrosive environment characteristic of deep, sour oil and gas wells was evaluated in laboratory tests. Included in the test program were NACE TM-01-77 sulfide stress cracking tests, chloride stress corrosion cracking tests in boiling MgCl /SUB 2'/ , and pitting and crevice corrosion tests. The HIP clad 625 performed excellently, displaying essentially the same corrosion resistance as wrought 625. Specifically the HIP clad 625 resisted sulfide stress cracking at applied stresses as high as 120% of yield strength and resisted chloride stress corrosion cracking at stresses exceeding 100% of yield. The HIP clad 625 also displayed immunity to pitting and crevice corrosion, with corrosion rates of <0.025 mm/y (1 mil/y). The 4130 base metal, however, was attacked severly in all tests. SEM/EDX analysis of the 625/4130 interface demonstrated that dilution of the cladding by the base metal was essentially eliminated.

  12. Permeation characteristics of some iron and nickel based alloys

    SciTech Connect

    Mitchell, D.J.; Edge, E.M.

    1985-06-15

    The permeation characteristics of deuterium in several iron and nickel based alloys were measured by the gas phase breakthrough technique in the temperature range 100 to 500 /sup 0/C with applied pressures ranging from 10 Pa to 100 kPa. The restriction of the gas flux imposed by surface oxides was modeled in order to evaluate the effects of surface oxide retardation of the gas flux on the effective values of the deuterium permeabilities and diffusivities in the alloys. The most permeable alloys were 430 and 431 stainless steels. The next most permeable alloy was Monel K-500, which exceeded the permeability of pure Ni by more than a factor of five at room temperature. The alloys with permeabilities less than pure Ni were, in order of decreasing permeability: the Inconels 625, 718, and 750, the Fe-Ni-Co glass-sealing alloys Kovar and Ceramvar, and the 300-series stainless steels. Deuterium trapping within the alloys appeared to influence the values of bulk diffusivities, which were not correlated with either the permeabilities or the chemical compositions of the alloys.

  13. Gelcasting superalloy powders

    SciTech Connect

    Janney, M.A.

    1995-12-31

    Gelcasting is a process for forming inorganic powders into complex shapes. It was originally developed for ceramic powders. A slurry of powder and a monomer solution is poured in to mold and polymerized in-situ to form gelled parts. Typically, only 2-4 wt % Polymer is used. The process has both aqueous and nonaqueous versions. Gelcasting is a generic process and has been used to produce ceramic parts from over a dozen different ceramic compositions ranging from alumina-based refractories to high-performance silicon nitride. Recently, gelcasting has been applied to forming superalloy powders into complex shapes. This application has posed several challenges not previously encountered in ceramics. In particular, problems were caused by the larger particle size and the higher density of the particles. Additional problems were encountered with binder removal. How these problems were overcome will be described.

  14. Effect of tensile mean stress on fatigue behavior of single-crystal and directionally solidified superalloys

    NASA Technical Reports Server (NTRS)

    Kalluri, Sreeramesh; Mcgaw, Michael A.

    1992-01-01

    Two nickel base superalloys, single crystal PWA 1480 and directionally solidified MAR-M 246 + Hf, were studied in view of the potential usage of the former and usage of the latter as blade materials for the turbomachinery of the Space Shuttle main engine. The baseline zero mean stress (ZMS) fatigue life (FL) behavior of these superalloys was established, and then the effect of tensile mean stress (TMS) on their FL behavior was characterized. A stress range based FL prediction approach was used to characterize both the ZMS and TMS fatigue data. In the past, several researchers have developed methods to account for the detrimental effect of tensile mean stress on the FL for polycrystalline engineering alloys. These methods were applied to characterize the TMS fatigue data of single crystal PWA 1480 and directionally solidified MAR-M 246 + Hf and were found to be unsatisfactory. Therefore, a method of accounting for the TMS effect on FL, that is based on a technique proposed by Heidmann and Manson was developed to characterize the TMS fatigue data of these superalloys. Details of this method and its relationship to the conventionally used mean stress methods in FL prediction are discussed.

  15. Hot Corrosion Behavior of Some Superalloys in a Simulated Incinerator Environment at 900 °C

    NASA Astrophysics Data System (ADS)

    Mudgal, Deepa; Singh, Surendra; Prakash, Satya

    2014-01-01

    Incinerators are being used to burn solid waste of all types. This burning of waste creates a very aggressive environment at extremely high temperature. This environment attacks the various components of the incinerators. Some studies have been reported regarding behavior of steels in simulated incinerator environment at 550 °C. In present work superalloys Superco 605, Superni 600, and Superni 718 have been subjected to cyclic oxidation in 40 wt.% K2SO4 + 40 wt.% Na2SO4 + 10 wt.% KCl + 10 wt.% NaCl environment at 900 °C under cyclic condition. Weight change measurements have been done and weight change has been plotted against the numbers of cycles. The oxide scales formed on the surface of the corroded superalloys have been characterize by FESEM, EDS, XRD, cross-sectional analysis, and x-ray mapping. The nickel-based superalloys Superni 600 and Superni 718 indicated better resistance to corrosion in the above environment whereas Superco 605 lead to massive weight gain.

  16. Effect of melt homogenization temperature on the cast structures of in 738 LC superalloy

    SciTech Connect

    Liu, L.; Zhen, B.L.; Banerji, A.; Reif, W. . Inst. fuer Metallforschung-Metallkunde); Sommer, F. . Inst. fuer Werkstoffwissenschaft)

    1994-03-01

    The structure of investment cast superalloys can be controlled by optimizing the process variables such as melt treatment, including melt superheating (T[sub s]) and the time of homogenization (t[sub h]), as well as casting parameters including mold preheating temperature (T[sub m]) and pouring temperature of the melt (T[sub p]). The effect of casting parameters has been extensively studied for several superalloys. A variation of the melt superheat, i.e. the temperature above the liquidus of the alloy, produces a significant effect on the cast microstructure. The melt must be superheated sufficiently above the liquidus temperature of the alloy to homogenize the melt by dissolving all the previously present phases in the charge. It is generally known that low superheating temperatures cause significant reductions in the grain size. There is no report on the details of the processing and mechanism of this effect. This paper presents the results of heterogeneous nucleation of the primary crystallites of [gamma]-phase and some modes of carbide precipitation in the nickel-base superalloy Inconel 738 LC cast with low melt superheating temperatures.

  17. Iron rich low cost superalloys. Ph.D. Thesis. Final Report

    NASA Technical Reports Server (NTRS)

    Wayne, S. F.

    1985-01-01

    An iron-rich low-cost superalloy was developed. The alloy, when processed by conventional chill casting, has physical and mechanical properties that compare favorably with existing nickel and cobalt based superalloys while containing significantly lower amounts of strategic elements. Studies were also made on the properties of Cr(20)-Mn(10)-C(3.4)-Fe(bal.), a eutectic alloy processed by chill casting and directional solidification which produced an aligned microstructure consisting of M7C3 fibers in a gamma-Fe matrix. Thermal expansion of the M7C3 (M = Fe, Cr, Mn) carbide lattice was measured up to 800 C and found to be highly anisotropic, with the a-axis being the predominant mode of expansion. Repetitive impact sliding wear experiments performed with the Fe rich eutectic alloy showed that the directionally solidified microstructure greatly improved the alloy's wear resistance as compared to the chill cast microstructure and conventional nickel base superalloys. Studies on the molybdenum cementite phase prove that the crystal structure of the xi phase is not orthorhombic. The crystal structure of the xi phase is made up of octahedra building elements consisting of four Mo and two Fe atoms and trigonal prisms consisting of four Fe and two Mo atoms. The voids are occupied by carbon atoms. The previous chemical formula for the molybdenum cementite MoFe2C is now clearly seen to be Mo12Fe22C10.

  18. Compatibility of Niobium Alloys and Superalloys in a Flowing He-Xe Power Conversion System

    NASA Technical Reports Server (NTRS)

    Bowman, Cheryl L.; Ritzert, Frank J.; Smialek, James L.; Jaster, Mark L.; rker, Samuel P.

    2004-01-01

    Proposed concepts for an ambitious mission to explore Jupiter's three icy moons place significant demands on the various spacecraft systems. There are many challenges related to the high output power conversion systems being considered, and one example is the need to ensure system compatibility at all levels. The utilization of appropriate materials for component structures is important to ensuring long mission life. Refractory metal alloys have attractive high-temperature properties in inert environments, but these alloys are sometimes susceptible to contamination. Potential material compatibility issues exist between refractory metal candidates and more conventional alloys. Nb-1Zr has long been considered one of the most well characterized refractory alloys that is well suited for elevated-temperature use and liquid-metal compatibility. However, previous studies have suggested that niobium alloys can not co-exist in a closed system with traditional stainless steels or superalloys due to transport of contaminants. The relevance of this information to a proposed power conversion system is discussed. Also, experiments and fundamental calculations are being performed to determine contamination transport from candidate superalloys to Nb-1Zr in a closed system with an inert carrier gas. Potential protective schemes are explored to ensure system level compatibility between the refractory alloy Nb-1Zr and a nickel-based superalloy.

  19. Aqueous electrochemistry of precipitation-hardened nickel base alloys

    SciTech Connect

    Hosoya, K.; Ballinger, R.; Prybylowski, J.; Hwang, I.S. )

    1990-11-01

    An investigation has been conducted to explore the importance of local crack tip electrochemical processes in precipitation-hardened Ni-Cr-Fe alloys driven by galvanic couples between grain boundary precipitates and the local matrix. The electrochemical behavior of {gamma}{prime} (Ni{sub 3}(Al,Ti)) has been determined as a function of titanium concentration, temperature, and solution pH. The electrochemical behavior of Ni-Cr-Fe solid solution alloys has been investigated as a function of chromium content for a series of 10 Fe-variable Cr (6--18%)-balance Ni alloys, temperature, and pH. The investigation was conducted in neutral and pH3 solutions over the temperature range 25--300{degree}C. The results of the investigation show that the electrochemical behavior of these systems is a strong function of temperature and composition. This is especially true for the {gamma}{prime} (Ni{sub 3}(Al,Ti)) system where a transition from active/passive behavior to purely active behavior and back again occurs over a narrow temperature range near 100{degree}C. Behavior of this system was also found to be a strong function of titanium concentration. In all cases, the Ni{sub 3}(Al,Ti) phase was active with respect to the matrix. The peak in activity near 100{degree}C correlates well with accelerated crack growth in this temperature range, observed in nickel-base alloy X-750 heat treated to precipitate {gamma}{prime} on the grain boundaries. 20 refs., 23 figs., 3 tabs.

  20. Effects of neutron irradiation on deformation behavior of nickel-base fastener alloys

    SciTech Connect

    Bajaj, R.; Mills, W.J.; Kammenzind, B.F.; Burke, M.G.

    1999-07-01

    This paper presents the effects of neutron irradiation on the fracture behavior and deformation microstructure of high-strength nickel-base alloy fastener materials, Alloy X-750 and Alloy 625. Alloy X-750 in the HTH condition, and Alloy 625 in the direct aged condition were irradiated to a fluence of 2.4x10{sup 20} n/cm{sup 2} at 264 C in the Advanced Test Reactor. Deformation structures at low strains were examined. It was previously shown that Alloy X-750 undergoes hardening, a significant degradation in ductility and an increase in intergranular fracture. In contrast, Alloy 625 had shown softening with a concomitant increase in ductility and transgranular failure after irradiation. The deformation microstructures of the two alloys were also different. Alloy X-750 deformed by a planar slip mechanism with fine microcracks forming at the intersections of slip bands with grain boundaries. Alloy 625 showed much more homogeneous deformation with fine, closely spaced slip bands and an absence of microcracks. The mechanism(s) of irradiation assisted stress corrosion cracking (IASCC) are discussed.

  1. Phase Stability of a Powder Metallurgy Disk Superalloy

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Gayda, John; Kantzos, P.; Telesman, Jack; Gang, Anita

    2006-01-01

    Advanced powder metallurgy superalloy disks in aerospace turbine engines now entering service can be exposed to temperatures approaching 700 C, higher than those previously encountered. They also have higher levels of refractory elements, which can increase mechanical properties at these temperatures but can also encourage phase instabilities during service. Microstructural changes including precipitation of topological close pack phase precipitation and coarsening of existing gamma' precipitates can be slow at these temperatures, yet potentially significant for anticipated disk service times exceeding 1,000 h. The ability to quantify and predict such potential phase instabilities and degradation of capabilities is needed to insure structural integrity and air worthiness of propulsion systems over the full life cycle. A prototypical advanced disk superalloy was subjected to high temperature exposures, and then evaluated. Microstructural changes and corresponding changes in mechanical properties were quantified. The results will be compared to predictions of microstructure modeling software.

  2. Computational and Experimental Design of Fe-Based Superalloys for Elevated-Temperature Applications

    SciTech Connect

    Liaw, Peter K.; Fine, Morris E.; Ghosh, Gautam; Asta, Mark D.; Liu, Chain T.; Sun, Zhiqian; Huang, Shenyan; Teng, Zhenke; Wang, Gongyao

    2012-04-13

    Analogous to nickel-based superalloys, Fe-based superalloys, which are strengthened by coherent B2- type precipitates are proposed for elevated-temperature applications. During the period of this project, a series of ferritic superalloys have been designed and fabricated by methods of vacuum-arc melting and vacuum-induction melting. Nano-scale precipitates were characterized by atom-probe tomography, ultrasmall- angle X-ray scattering, and transmission-electron microscopy. A duplex distribution of precipitates was found. It seems that ferritic superalloys are susceptible to brittle fracture. Systematic endeavors have been devoted to understanding and resolving the problem. Factors, such as hot rolling, precipitate volume fractions, alloy compositions, precipitate sizes and inter-particle spacings, and hyperfine cooling precipitates, have been investigated. In order to understand the underlying relationship between the microstructure and creep behavior of ferric alloys at elevated temperatures, in-situ neutron studies have been carried out. Based on the current result, it seems that the major role of β' with a 16%-volume fraction in strengthening ferritic alloys is not load sharing but interactions with dislocations. The oxidation behavior of one ferritic alloy, FBB8 (Fe-6.5Al-10Ni-10Cr-3.4Mo-0.25Zr-0.005B, weight percent), was studied in dry air. It is found that it possesses superior oxidation resistance at 1,023 and 1,123 K, compared with other creep-resistant ferritic steels [T91 (modified 9Cr-1Mo, weight percent) and P92 (9Cr-1.8W-0.5Mo, weight percent)]. At the same time, the calculation of the interfacial energies between the -iron and B2-type intermetallics (CoAl, FeAl, and NiAl) has been conducted.

  3. Solution heat-treatment of Nb-modified MAR-M247 superalloy

    SciTech Connect

    Soares Azevedo e Silva, Paulo Ricardo; Baldan, Renato; Nunes, Carlos Angelo; Carvalho Coelho, Gilberto; and others

    2013-01-15

    MAR-M247 superalloy has excellent mechanical properties and good oxidation resistance at elevated temperatures. Niobium is an element known as {gamma} Prime phase hardener in nickel-based superalloys, besides promoting homogeneous distribution of MC carbides. This work is inserted in a project that aims to evaluate the total replacement of tantalum by niobium atoms in MAR-M247 superalloy (10.2 Co, 10.2 W, 8.5Cr, 5.6 Al, 1.6 Nb, 1.4 Hf, 1.1 Ti, 0.7 Mo, 0.15 C, 0.06 Zr, 0.015 B, Ni balance-wt.%). Based on microstructural characterizations (SEM and FEG-SEM, both with EDS) of the as-cast material and heat-treated materials as well as utilizing Thermocalc simulations and experiments of differential thermal analysis (DTA), heat-treatment at 1260 Degree-Sign C for 8 h was chosen as an ideal condition for the solution of Nb-modified MAR-M247 superalloy. The hardness of as-cast and ideally solution treated materials was 390 {+-} 14 HV and 415 {+-} 6 HV, respectively. - Highlights: Black-Right-Pointing-Pointer DTA and microstructure of MAR-M247(Nb) showed a good agreement with Thermocalc. Black-Right-Pointing-Pointer An ideal condition for solution heat-treatment of MAR-M247(Nb) is 1260 Degree-Sign C for 8 h. Black-Right-Pointing-Pointer It was an observed evidence of incipient melting in samples heat-treated at 1280 Degree-Sign C.

  4. Crystal Structure Effects on Surface Fractures of Impacted Superalloy Cubes

    SciTech Connect

    Holt, William H.; Mock, Willis Jr.; Armstrong, Ronald W.

    2006-07-28

    Cubes (9.5 mm on edge) of polycrystalline and unidirectionally solidified forms of a nickel-based superalloy (62.5% Ni) were impacted in vacuum at 761 m/sec and 746 m/sec, respectively, by gas-gun-accelerated 3.18 mm-thick disks of 7075-T6 aluminum. Visible fractures on the cubes were primarily associated with the impacted surfaces. The polycrystalline cube showed an irregular pattern of many open cracks; the residual compression along the direction of impact is 3.3%. The unidirectionally solidified single crystal cube (impacted on a face normal to the <100> direction) showed only minor cracks near the center of the cube face, extending to the centers of the face edges; the residual compression is 6.2%. The results are discussed in terms of the obstacle nature of grain boundaries and local stress buildup for cracking, along with the otherwise seemingly contrary result of lower polycrystal ductility relative to that observed for the undirectionally solidified single crystal material.

  5. Expert systems for superalloy studies

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.; Kaukler, William F.

    1990-01-01

    There are many areas in science and engineering which require knowledge of an extremely complex foundation of experimental results in order to design methodologies for developing new materials or products. Superalloys are an area which fit well into this discussion in the sense that they are complex combinations of elements which exhibit certain characteristics. Obviously the use of superalloys in high performance, high temperature systems such as the Space Shuttle Main Engine is of interest to NASA. The superalloy manufacturing process is complex and the implementation of an expert system within the design process requires some thought as to how and where it should be implemented. A major motivation is to develop a methodology to assist metallurgists in the design of superalloy materials using current expert systems technology. Hydrogen embrittlement is disasterous to rocket engines and the heuristics can be very complex. Attacking this problem as one module in the overall design process represents a significant step forward. In order to describe the objectives of the first phase implementation, the expert system was designated Hydrogen Environment Embrittlement Expert System (HEEES).

  6. Oxidation Resistance and Critical Sulfur Content of Single-Crystal Superalloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    1997-01-01

    The high-temperature components of a jet turbine engine are made from nickel-base superalloys. These components must be able to withstand high stresses, fatigue, and corrosive reactions with high-temperature gases. Such oxidation resistance is associated with slow-growing Al2O3 scales that remain adherent to superalloy components after many thermal cycles. Historically, good oxidation resistance has been obtained by coating these components with Ni-Cr-Al-Y coatings, where small additions of yttrium (Y) were necessary for scale adhesion. Subsequently, it was found that the Y aids scale adhesion by preventing sulfur from segregating to the scale metal interface and thus preventing the sulfur from weakening the oxide-metal bonds. Y is a difficult element to incorporate in single-crystal superalloy castings, but it was shown in early work at the NASA Lewis Research Center that good adhesion could be obtained for low-sulfur, uncoated, singlecrystal superalloys, without Y additions. Low sulfur contents for these uncoated superalloys were achieved in the laboratory by a high-temperature hydrogen annealing process. This process allows segregation and surface cleaning of sulfur monolayers in a reducing environment. Another approach is to remove sulfur from the alloy in the melting process. The present study was designed to establish a guideline for the minimum level of desulfurization needed to achieve maximum performance. Coupons of various thicknesses of the superalloy PWA 1480 were hydrogen annealed at various times (8 to 100 hr) and temperatures (1000 to 1300 C), resulting in coupons with sulfur contents ranging from about 0.05 to 5 ppm. Cyclic oxidation tests at 1100 C were then used to assess adhesion and spalling. The weight change of one set of 20-mil (0.5-mm) samples, annealed for 20 hr at 1000, 1100, 1200, and 1300 C, is shown in the following figure. Clearly, the effect of the annealing temperature is quite dramatic in that the higher temperatures produced scales

  7. Effects of Hydrogen Annealing, Sulfur Segregation and Diffusion on the Cyclic Oxidation Resistance of Superalloys: a Review

    NASA Technical Reports Server (NTRS)

    Smialek, J. L.; Jayne, D. T.; Schaeffer, J. C.; Murphy, W. H.

    1994-01-01

    This review is based on the phenomenon of improved oxide scale adhesion for desulfurized superalloys. The proposed adhesion mechanism involves sulfur interfacial segregation and scale-metal bond weakening. Sulfur surface segregation on superalloys is examined as a function of temperature and sulfur content and related to classical behavior predicted by the McLean isotherm. Effective desulfurization to less than 1 ppmw can be accomplished by hydrogen annealing and is governed by sulfur diffusion kinetics in nickel. Hydrogen annealing results in excellent cyclic oxidation resistance for a number of advanced superalloys. The concept of a critical sulfur content is discussed in terms of practical annealing conditions and section thicknesses.

  8. Effects of hydrogen annealing, sulfur segregation and diffusion on the cyclic oxidation resistance of superalloys: A review

    NASA Technical Reports Server (NTRS)

    Smialek, J. L.; Jayne, D. T.; Schaeffer, J. C.; Murphy, W. H.

    1994-01-01

    This review is based on the phenomenon of improved oxide scale adhesion for desulfurized superalloys. The proposed adhesion mechanism involves sulfur interfacial segregation and scale-metal bond weakening. Sulfur surface segregation on superalloys is examined as a function of temperature and sulfur content, and is related to the classical behavior predicted by the McLean isotherm. Effective desulfurization to less than 1 ppmw can be accomplished by hydrogen annealing and is described by sulfur diffusion kinetics in nickel. Hydrogen annealing results in excellent cyclic oxidation resistance for a number of advanced superalloys. The concept of a critical sulfur content is discussed in terms of practical annealing conditions and section thicknesses.

  9. The role of interfacial dislocation networks in high temperature creep of superalloys

    NASA Technical Reports Server (NTRS)

    Gabb, T. P.; Draper, S. L.; Hull, D. R.; Mackay, R. A.; Nathal, M. V.

    1989-01-01

    The dislocation networks generated during high-temperature creep of several single-crystal nickel-based superalloys are analyzed. The networks continually evolve during creep at relatively low temperatures or eventually reach a more stable configuration at high temperatures. Specifically, the role of these networks in directional coarsening processes are studied, along with their formation kinetics, characteristics, and stability during creep. The results of this study combined with previous findings suggest that the directional coarsening process is strongly influenced by elastic strain energy. The dislocation networks formed during primary creep are found to be stable during all subsequent creep stages. Aspects of these dislocation networks are determined to be a product of both the applied creep stress and coherency strains.

  10. Development of superalloys by powder metallurgy for use at 1000 - 1400 F

    NASA Technical Reports Server (NTRS)

    Calhoun, C. D.

    1971-01-01

    Consolidated powders of four nickel-base superalloys were studied for potential application as compressor and turbine discs in jet engines. All of the alloys were based on the Rene' 95 chemistry. Three of these had variations in carbon and A12O3 contents, and the fourth alloy was chemically modified to a higher volume fraction. The A12O3 was added by preoxidation of the powders prior to extrusion. Various levels of four experimental factors (1) alloy composition, (2) grain size, (3) thermomechanical processing, and (4) room temperature deformation plus final age were evaluated by tensile and stress rupture testing at 1200 F. Various levels of the four factors were assumed in order to construct the statistically-designed experiment, but the actual levels investigated were established in preliminary studies that preceded the statistical process development study.

  11. Low Cost Heat Treatment Process for Production of Dual Microstructure Superalloy Disks

    NASA Technical Reports Server (NTRS)

    Gayda, John; Gabb, Tim; Kantzos, Pete; Furrer, David

    2003-01-01

    There are numerous incidents where operating conditions imposed on a component mandate different and distinct mechanical property requirements from location to location within the component. Examples include a crankshaft in an internal combustion engine, gears for an automotive transmission, and disks for a gas turbine engine. Gas turbine disks are often made from nickel-base superalloys, because these disks need to withstand the temperature and stresses involved in the gas turbine cycle. In the bore of the disk where the operating temperature is somewhat lower, the limiting material properties are often tensile and fatigue strength. In the rim of the disk, where the operating temperatures are higher than those of the bore, because of the proximity to the combustion gases, resistance to creep and crack growth are often the limiting properties.

  12. High temperature seals between ceramic separation membranes and super-alloy housing

    NASA Technical Reports Server (NTRS)

    Honea, G.; Sridhar, K. R.

    1991-01-01

    One of the concepts for oxygen production from Martian atmospheric carbon dioxide involves the use of tubular electrochemical membranes for oxygen separation. The tubular configuration offers the advantage of being able to separate the oxygen at pressures of up to 500 psi, thereby eliminating the need for a pre-liquefaction oxygen compressor. A key technology that has to be developed in order for the electrochemical separator to combine as a compressor is a high temperature static seal between the ceramic separation cell and the nickel-based super-alloy tube. Equipment was designed and fabricated to test the seals. Efforts are under way to develop a finite element model to study the thermal stresses at the joints and on the seal, and the optimal shape of the seal. The choice of seal materials and the technique to be used to fabricate the seals are also being investigated.

  13. Technology of High-speed Direct Laser Deposition from Ni-based Superalloys

    NASA Astrophysics Data System (ADS)

    Klimova-Korsmik, Olga; Turichin, Gleb; Zemlyakov, Evgeniy; Babkin, Konstantin; Petrovsky, Pavel; Travyanov, Andrey

    Recently, additive manufacturing is the one of most perspective technologies; it can replace conventional methods of casting and subsequent time-consuming machining. One of the most interesting additive technologies - high-speed direct laser deposition (HSDLD) allows realizing heterophase process during the manufacturing, which there is process takes place with a partial melting of powder. This is particularly important for materials, which are sensitive to strong fluctuations of temperature treatment regimes, like nickel base alloys with high content of gamma prime phase. This alloys are interested for many industrial areas, mostly there are used in engine systems, aircraft and shipbuilding, aeronautics. Heating and cooling rates during the producing process determine structure and affect on its properties. Using HSDLD process it possible to make a products from Ni superalloys with ultrafine microstructure and satisfactory mechanical characteristics without special subsequent heatreatment.

  14. Microstructural tomography of a Ni(70)Cr(20)Al(10) superalloy using focused ion beam microscopy.

    PubMed

    Uchic, M D; De Graef, M; Wheeler, R; Dimiduk, D M

    2009-09-01

    A focused ion beam (FIB) microscope has been used to simultaneously depth profile and image the gamma-gamma' microstructure of a nickel base superalloy using normal incidence milling in order to characterize the precipitate microstructure in three dimensions (3D). The normal incidence milling rates of the gamma and gamma' phases in this alloy are closely matched when the orientation of the depth-profiled surface is near 001, which allows for uniform material removal to depths up to a couple of microns. Depth-profiling experiments consisted of automated ion milling and collection of ion-generated secondary-electron images at specified intervals, and was demonstrated for a voxel resolution of roughly 15 x 15 x 16 nm(3). Image-processing software was used for automated processing of the 2D image sequence to render the gamma precipitate structure in 3D. PMID:19523769

  15. Microstructural changes during creep of CMSX-4 single crystal Ni base superalloy at 750 degrees C.

    PubMed

    Dubiel, B T; Czyrska-Filemonowicz, A

    2010-03-01

    TEM studies of creep tested CMSX-4 nickel-base single crystal superalloy were performed to analyse a microstructure evolution during creep at temperature 750 degrees C, and uniaxial tensile stress of 675 MPa. Microstructural analyses were focused mainly on examination of dislocation configurations during primary and secondary creep stages of high temperature deformation. At such low temperature and high stress creep deformation proceed by cutting of gamma' particles by dislocations. It was found that primary creep is initiated by movement of dislocations with Burgers vector a/2 <110> in the gamma phase. The second type of dislocations active at primary creep stage are extended dislocation ribbons with overall a<112> Burgers vector, separated by superlattice stacking faults, cutting both the gamma and gamma' phases. The movement of the dislocation ribbons is inhibited at secondary creep stage by dislocation networks formed at gamma-gamma' interfaces. PMID:20500397

  16. Evaluation of Die Chilling Effects during Forging of Nimonic-80A Superalloy

    SciTech Connect

    Shahriari, D.; Sadeghi, M. H.; Amiri, A.; Cheraghzadeh, M.

    2010-06-15

    Nimonic-80A is a kind of nickel-based superalloys which is used in high temperature components of land gas turbines. In this paper, the influence of four design factors: die temperature, strain rate, friction coefficient and geometry size of ring sample over the variation of internal diameters (VID) and forging load (FL) was studied. It was done by means of design methodology based on DOE-designated full factorial and FE simulations. FEM and experimental results showed that the variation of internal diameters and forging load had inverse proportion to the die temperature. Regression models were developed by using the response surface methodology (RSM) for VID and FL. Rate of the dynamic recrystallization varied depending on different amounts of die temperature. The results can be used in the semi-isothermal forging of complex part of the Nimonic-80A.

  17. Influence of cobalt, tantalum, and tungsten on the microstructure and mechanical properties of superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Nathal, M. V.; Ebert, L. J.

    1982-01-01

    The influence of Co, Ta, and W on the microstructure and mechanical properties of nickel base super-alloy single crystals was investigated. A matrix of alloys was based on Mar-M 247 stripped of C, B, Zr, and Hf. The microstructures of the alloys were examined using optical and electron microscopy, phase extraction, X-ray diffraction, and differential thermal analysis. Tensile and creep-rupture tests were performed at 1000 C. An increase in tensile and creep strength resulted when Co was removed from alloys containing high refractory metal contents, but Co effects were negligible for alloys with lower refractory metal levels. In the composition range studied, W was more effective than Ta in increasing the creep resistance. The mechanical properties are discussed in relation to the microstructures of the alloys.

  18. Soft Computing Methods in Design of Superalloys

    NASA Technical Reports Server (NTRS)

    Cios, K. J.; Berke, L.; Vary, A.; Sharma, S.

    1996-01-01

    Soft computing techniques of neural networks and genetic algorithms are used in the design of superalloys. The cyclic oxidation attack parameter K(sub a), generated from tests at NASA Lewis Research Center, is modelled as a function of the superalloy chemistry and test temperature using a neural network. This model is then used in conjunction with a genetic algorithm to obtain an optimized superalloy composition resulting in low K(sub a) values.

  19. Advanced single crystal for SSME turbopumps

    NASA Technical Reports Server (NTRS)

    Fritzemeier, L. G.

    1989-01-01

    The objective of this program was to evaluate the influence of high thermal gradient casting, hot isostatic pressing (HIP) and alternate heat treatments on the microstructure and mechanical properties of a single crystal nickel base superalloy. The alloy chosen for the study was PWA 1480, a well characterized, commercial alloy which had previously been chosen as a candidate for the Space Shuttle Main Engine high pressure turbopump turbine blades. Microstructural characterization evaluated the influence of casting thermal gradient on dendrite arm spacing, casting porosity distribution and alloy homogeneity. Hot isostatic pressing was evaluated as a means of eliminating porosity as a preferred fatigue crack initiation site. The alternate heat treatment was chosen to improve hydrogen environment embrittlement resistance and for potential fatigue life improvement. Mechanical property evaluation was aimed primarily at determining improvements in low cycle and high cycle fatigue life due to the advanced processing methods. Statistically significant numbers of tests were conducted to quantitatively demonstrate life differences. High thermal gradient casting improves as-cast homogeneity, which facilitates solution heat treatment of PWA 1480 and provides a decrease in internal pore size, leading to increases in low cycle and high cycle fatigue lives.

  20. Effects of hafnium additions on the solidification behavior of directionally solidified superalloys. Final report, 1 June 1975-31 August 1977

    SciTech Connect

    Brody, H.D.; Giamei, A.F.

    1981-10-01

    A cooperative university/industry research program into the effect of hafnium additions on the solidification behavior of nickel base superalloys was carried out under Air Force sponsorship at the University of Pittsburgh and Pratt and Whitney Aircraft Company. The research was aimed at gaining a fundamental understanding of the basic solidification characteristics, i.e., development of structure and segregation, of hafnium-modified MAR-M200 over the normal range of casting conditions and for a reasonable variation in alloy content, especially hafnium content.

  1. Feasibility Study for Casting of High Temperature Refractory Superalloy Composites

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    1998-01-01

    Abstract This study investigated the feasibility of using conventional casting technique to fabricate refractory wires reinforced superalloy composites. These composites were being developed for advanced rocket engine turbine blades and other high temperature applications operating up to 2000 F. Several types of refractory metal wires such as W- Th, W-Re, Mo-Hf-C and W-HF-C reinforced waspaloy were experimentally cast and heat treated at 2000 F up to 48 hrs. Scanning electron microscope analysis was conducted in regions adjacent to the wire-matrix interface to determine the reaction zone and chemical compatibility resulting from material interdiffusion. It was concluded that fabrication using conventional casting may be feasible because the wire-matrix reaction zone thickness was comparable to similar composites produced by arc-sprayed monotape with hot isostatic pressing technique, Moreover, it was also found that the chemical compatibility could be improved significantly through a slight modification of the superalloy matrix compositions.

  2. Cleaning process for contaminated superalloy powders

    NASA Technical Reports Server (NTRS)

    Anglin, A. E.

    1978-01-01

    A cleaning process for removing interstitial contaminants from superalloy powders after wet grinding is described. Typical analyses of oxygen, carbon, nitrogen, and hydrogen in ball-milled WAZ-20 superalloy samples after hydrogen plus vacuum cleaning are presented. The hydrogen cleaning step involves heating retorts containing superalloy powder twice under flowing hydrogen with a 24-hour hold at each temperature. The vacuum step involves heating cold-pressed billets two hours at an elevated temperature at a pressure of 10 microPa. It is suggested that the hydrogen plus vacuum cleaning procedure can be applied to superalloys contaminated by other substances in other industrial processes.

  3. Near-Threshold Fatigue Crack Growth Behavior of Fine-Grain Nickel-Based Alloys

    NASA Technical Reports Server (NTRS)

    Newman, John A.; Piascik, Robert S.

    2003-01-01

    Constant-Kmax fatigue crack growth tests were performed on two finegrain nickel-base alloys Inconel 718 (DA) and Ren 95 to determine if these alloys exhibit near-threshold time-dependent crack growth behavior observed for fine-grain aluminum alloys in room-temperature laboratory air. Test results showed that increases in K(sub max) values resulted in increased crack growth rates, but no evidence of time-dependent crack growth was observed for either nickel-base alloy at room temperature.

  4. X-ray photoelectron spectroscopy study of nickel and nickel-base alloy surface alterations in simulated hot corrosion conditions with emphasis on eventual application to turbine blade corrosion

    NASA Technical Reports Server (NTRS)

    Mateescu, G. D.; Smith, S. R.

    1979-01-01

    Research on the high temperature oxidation and Na2SO4 induced hot corrosion of some nickel base superalloys was accomplished by using ESCA to determine the surface composition of the oxidized or corroded samples. Oxidation was carried out at 900 or 1000 C in slowly flowing O2 for samples of B-1900, NASA-TRW VIA, 713C, and IN-738. Oxidation times ranged from 0.5 to 100 hr. Hot corrosion of B-1900 was induced applying a coating of Na2SO4 to peroxidized samples, the heating to 900 C in slowly flowing O2. For oxidized samples, the predominant type of scale formed by each superalloy was determined, and a marked surface enrichment of Ti was found in each case. For corroded samples, the transfer of significant amounts of material from the oxide layer to the surface of the salt layer was observed to occur long before the onset of accelerating weight-gain. Changes in surface composition were observed to coincide with the beginning of accelerating corrosion, the most striking of which was a tenfold decrease in the sulfur to sodium ration and an increase in the Cr(VI) ratio.

  5. Superalloy Foams for Aeroshell Applications

    NASA Technical Reports Server (NTRS)

    Gayda, John; Padula, Santo, II

    2001-01-01

    Current thermal protection systems for reentry from space, such as that employed on the space shuttle, rely on ceramic tiles with ultra-low conductivity. These materials provide excellent thermal protection but are extremely fragile, easily degraded by environmental attack, and carry no structural loads. Future thermal protection systems being proposed in NASAs MITAS Program will attempt to combine thermal protection with improved durability and structural capability without significant increases in vehicle weight. This may be accomplished by combining several materials in a layered structure to obtain the desired function for aeroshell applications. One class of materials being considered for inclusion in this concept are high temperature metal foam. The objective of this paper was to fabricate low density, superalloy foams and conduct limited testing to evaluate their thermal and structural capabilities. Superalloys were chosen for evaluation as they possesses good strength and excellent environmental endurance over a wide range of temperatures. Utilizing superalloys as low density foams, with porosity contents greater than 90%, minimizes weight and thermal conductivity.

  6. Microstructure Modeling of a Ni-Fe-Based Superalloy During the Rotary Forging Process

    NASA Astrophysics Data System (ADS)

    Loyda, A.; Hernández-Muñoz, G. M.; Reyes, L. A.; Zambrano-Robledo, P.

    2016-06-01

    The microstructure evolution of Ni-Fe superalloys has a great influence on the mechanical behavior during service conditions. The rotary forging process offers an alternative to conventional bulk forming processes where the parts can be rotary forged with a fraction of the force commonly needed by conventional forging techniques. In this investigation, a numerical modeling of microstructure evolution for design and optimization of the hot forging operations has been used to manufacture a heat-resistant nickel-based superalloy. An Avrami model was implemented into finite element commercial platform DEFORM 3D to evaluate the average grain size and recrystallization during the rotary forging process. The simulations were carried out considering three initial temperatures, 980, 1000, and 1050 °C, to obtain the microstructure behavior after rotary forging. The final average grain size of one case was validated by comparing with results of previous experimental work of disk forging operation. This investigation was aimed to explore the influence of the rotary forging process on microstructure evolution in order to obtain a homogenous and refined grain size in the final component.

  7. Influence of a magnetic field during directional solidification of MAR-M 246 + Hf superalloy

    NASA Technical Reports Server (NTRS)

    Andrews, J. Barry; Alter, Wendy; Schmidt, Dianne

    1991-01-01

    An area that has been almost totally overlooked in the optimization of properties in directionally solidified superalloys is the control of microstructural features through the application of a magnetic field during solidification. The influence of a magnetic field on the microstructural features of a nickel-base superalloys is investigated. Studies were performed on the dendritic MAR-M 246+Hf alloy, which was solidified under both a 5 K gauss magnetic field and under no-applied-field conditions. The possible influences of the magnetic field on the solidification process were observed by studying variations in microstructural features including volume fraction, surface area, number, and shape of the carbide particles. Stereological factors analyzed also included primary and secondary dendrite arm spacing and the volume fraction of the interdendritic eutectic constituent. Microprobe analysis was performed to determine the chemistry of the carbides, dendrites, and interdendritic constituents, and how it varied between field and no-field solidification samples. Experiments involving periodic application and removal of the magnetic field were also performed in order to permit a comparison with structural variations observed in a MAR-M 246+Hf alloy solidified during KC-135 high-g, low-g maneuvers.

  8. NASA and Superalloys: A Customer, a Participant, and a Referee

    NASA Technical Reports Server (NTRS)

    Nathal, Michael V.

    2008-01-01

    NASA has had a long history of research and development in the field of superalloys. These efforts have continued today, where the latest advancements in turbine disk and blade technologies are being developed. Although NASA does support military flight systems, its predominant role is in supporting civilian air transportation systems, and thus has goals for improving fuel efficiency, emissions, noise, and safety of today s aircraft. NASA has traditionally served several distinct but complimentary roles as participants in multi-disciplinary research teams, as customers who fund research and development efforts at industry and universities, and as referees who can address broad issues that affect the entire aeronautics community. Because of our longer range viewpoint, we can take on higher risk, higher reward research topics. NASA can also serve as an intermediary between the basic research performed primarily at universities and the development efforts emphasized by industry. By interacting with individual companies, NASA can identify areas of general interest and problems common to a large portion of the aeronautics community, and devise programs aimed at solving these problems. In space missions, NASA is a direct customer responsible for developing vehicles. In the case of the Space Shuttle, NASA has worked with various contractors to design and build numerous components out of superalloys. Another fascinating area for the use of superalloys is in power systems for long life applications in space. Potential missions include providing electric power for deep space missions, surface rovers, including lunar and Mars, and stationary power generators on the lunar surface.

  9. NASA and Superalloys: A Customer, a Participant, and a Referee

    NASA Technical Reports Server (NTRS)

    Nathal, Michael V.

    2008-01-01

    NASA has had a long history of research and development in the field of superalloys. These efforts have continued today, where the latest advancements in turbine disk and blade technologies are being developed Although NASA does support military flight systems, it s predominant role is in supporting civilian air transportation systems, and thus has goals for improving fuel efficiency, emissions, noise, and safety of today s aircraft. NASA has traditionally served several distinct but complimentary roles as participants in multi-disciplinary research teams, as customers who fund research and development efforts at industry and universities, and as referees who can address broad issues that affect the entire aeronautics community. Because of our longer range viewpoint, we can take on higher risk, higher reward research topics. NASA can also serve as an intermediary between the basic research performed primarily at universities and the development efforts emphasized by industry. By interacting with individual companies, NASA can identify areas of general interest and problems common to a large portion of the aeronautics community, and devise programs aimed at solving these problems. In space missions, NASA is a direct customer responsible for developing vehicles. In the case of the Space Shuttle, NASA has worked with various contractors to design and build numerous components out of superalloys. Another fascinating area for the use of superalloys is in power systems for long life applications in space. Potential missions include providing electric power for deep space missions, surface rovers, including lunar and Mars, and stationary power generators on the lunar surface.

  10. A study on laser weldability improvement of newly developed Haynes 282 superalloy

    NASA Astrophysics Data System (ADS)

    Osoba, Lawrence Opeyemi

    Haynes alloy 282 is a new gamma prime (gamma') precipitation strengthened nickel-base superalloy developed for high temperature applications in land-based and aero turbine engines. Joining is a crucial process both during the manufacturing of new components and repair of service-damaged turbine parts. Unfortunately, the new superalloy cracks during laser beam welding (LBW), which is an attractive technique for joining superalloys components due to its low heat input characteristic that preclude the geometrical distortion of welded components. This research is therefore initiated with the goal of studying and developing an effective approach for preventing or minimizing cracking during LBW of the new superalloy Haynes 282. Careful and detailed electron microscopy and spectroscopy study reveal, for the first time, the formation of sub-micron grain boundary M5B3 particles, in the material. Microstructural study of welded specimens coupled with Gleeble thermo-mechanical physical simulations shows that the primary cause of weld heat affected zone (HAZ) cracking in the alloy is the sub-solidus liquation reaction of intergranular M5B3 borides in the material. Further weldability study showed that the HAZ liquation cracking problem worsens with reduction in welding heat input, which is normally necessary to produce the desired weld geometry with minimum distortion. In order to minimize the HAZ cracking during low heat input laser welding, microstructural modification of the alloy by heat treatment at 1080--1100°C has been developed. The pre-weld heat treatment minimizes cracking in the alloy by reducing the volume fraction of the newly identified M5B3 borides, while also minimizing non-equilibrium grain boundary segregation of boron liberated during dissociation of the boride particles. Further improvement in resistance to cracking was produced by subjecting the material to thermo-mechanically induced grain refinement coupled with a pre-weld heat treatment at 1080

  11. Nickel-based anodic electrocatalysts for fuel cells and water splitting

    NASA Astrophysics Data System (ADS)

    Chen, Dayi

    Our world is facing an energy crisis, so people are trying to harvest and utilize energy more efficiently. One of the promising ways to harvest energy is via solar water splitting to convert solar energy to chemical energy stored in hydrogen. Another of the options to utilize energy more efficiently is to use fuel cells as power sources instead of combustion engines. Catalysts are needed to reduce the energy barriers of the reactions happening at the electrode surfaces of the water-splitting cells and fuel cells. Nickel-based catalysts happen to be important nonprecious electrocatalysts for both of the anodic reactions in alkaline media. In alcohol fuel cells, nickel-based catalysts catalyze alcohol oxidation. In water splitting cells, they catalyze water oxidation, i.e., oxygen evolution. The two reactions occur in a similar potential range when catalyzed by nickel-based catalysts. Higher output current density, lower oxidation potential, and complete substrate oxidation are preferred for the anode in the applications. In this dissertation, the catalytic properties of nickel-based electrocatalysts in alkaline medium for fuel oxidation and oxygen evolution are explored. By changing the nickel precursor solubility, nickel complex nanoparticles with tunable sizes on electrode surfaces were synthesized. Higher methanol oxidation current density is achieved with smaller nickel complex nanoparticles. DNA aggregates were used as a polymer scaffold to load nickel ion centers and thus can oxidize methanol completely at a potential about 0.1 V lower than simple nickel electrodes, and the methanol oxidation pathway is changed. Nickel-based catalysts also have electrocatalytic activity towards a wide range of substrates. Experiments show that methanol, ethanol, glycerol and glucose can be deeply oxidized and carbon-carbon bonds can be broken during the oxidation. However, when comparing methanol oxidation reaction to oxygen evolution reaction catalyzed by current nickel-based

  12. Superalloy Lattice Block Developed for Use in Lightweight, High-Temperature Structures

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G.; Whittenberger, J. Daniel; Krause, David L.

    2003-01-01

    Successful development of advanced gas turbine engines for aircraft will require lightweight, high-temperature components. Currently titanium-aluminum- (TiAl) based alloys are envisioned for such applications because of their lower density (4 g/cm3) in comparison to superalloys (8.5 g/cm3), which have been utilized for hot turbine engine parts for over 50 years. However, a recently developed concept (lattice block) by JAMCORP, Inc., of Willmington, Massachusetts, would allow lightweight, high-temperature structures to be directly fabricated from superalloys and, thus, take advantage of their well-known, characterized properties. In its simplest state, lattice block is composed of thin ligaments arranged in a three dimensional triangulated trusslike configuration that forms a structurally rigid panel. Because lattice block can be fabricated by casting, correctly sized hardware is produced with little or no machining; thus very low cost manufacturing is possible. Together, the NASA Glenn Research Center and JAMCORP have extended their lattice block methodology for lower melting materials, such as Al alloys, to demonstrate that investment casting of superalloy lattice block is possible. This effort required advances in lattice block pattern design and assembly, higher temperature mold materials and mold fabrication technology, and foundry practice suitable for superalloys (ref. 1). Lattice block panels have been cast from two different Ni-base superalloys: IN 718, which is the most commonly utilized superalloy and retains its strength up to 650 C; and MAR M247, which possesses excellent mechanical properties to at least 1100 C. In addition to the open-cell lattice block geometry, same-sized lattice block panels containing a thin (1-mm-thick) solid face on one side have also been cast from both superalloys. The elevated-temperature mechanical properties of the open cell and face-sheeted superalloy lattice block panels are currently being examined, and the

  13. Materials review for improved automotive gas turbine engine. [superalloys, refractory alloys, and ceramics

    NASA Technical Reports Server (NTRS)

    Belleau, C.; Ehlers, W. L.; Hagen, F. A.

    1978-01-01

    The potential role of superalloys, refractory alloys, and ceramics in the hottest sections of engines operating with turbine inlet temperatures as high as 1370 C is examined. The convential superalloys, directionally solidified eutectics, oxide dispersion strenghened alloys, and tungsten fiber reinforced superalloys are reviewed and compared on the basis of maximum turbine blade temperature capability. Improved high temperature protective coatings and special fabrication techniques for these advanced alloys are discussed. Chromium, columbium, molybdenum, tantalum, and tungsten alloys are also reviewed. Molbdenum alloys are found to be the most suitable for mass produced turbine wheels. Various forms and fabrication processes for silicon nitride, silicon carbide, and SIALON's are investigated for use in highstress and medium stress high temperature environments.

  14. Tensile Properties and Deformation Characteristics of a Ni-Fe-Base Superalloy for Steam Boiler Applications

    NASA Astrophysics Data System (ADS)

    Zhong, Zhihong; Gu, Yuefeng; Yuan, Yong; Shi, Zhan

    2014-01-01

    Ni-Fe-base superalloys due to their good manufacturability and low cost are the proper candidates for boiler materials in advanced power plants. The major concerns with Ni-Fe-base superalloys are the insufficient mechanical properties at elevated temperatures. In this paper, tensile properties, deformation, and fracture characteristics of a Ni-Fe-base superalloy primarily strengthened by γ' precipitates have been investigated from room temperature to 1073 K (800 °C). The results showed a gradual decrease in the strength up to about 973 K (700 °C) followed by a rapid drop above this temperature and a ductility minimum at around 973 K (700 °C). The fracture surfaces were studied using scanning electron microscopy and the deformation mechanisms were determined by the observation of deformed microstructures using transmission electron microscopy. An attempt has been made to correlate the tensile properties and fracture characteristics at different temperatures with the observed deformation mechanisms.

  15. Additive Manufacturing of Single-Crystal Superalloy CMSX-4 Through Scanning Laser Epitaxy: Computational Modeling, Experimental Process Development, and Process Parameter Optimization

    NASA Astrophysics Data System (ADS)

    Basak, Amrita; Acharya, Ranadip; Das, Suman

    2016-08-01

    This paper focuses on additive manufacturing (AM) of single-crystal (SX) nickel-based superalloy CMSX-4 through scanning laser epitaxy (SLE). SLE, a powder bed fusion-based AM process was explored for the purpose of producing crack-free, dense deposits of CMSX-4 on top of similar chemistry investment-cast substrates. Optical microscopy and scanning electron microscopy (SEM) investigations revealed the presence of dendritic microstructures that consisted of fine γ' precipitates within the γ matrix in the deposit region. Computational fluid dynamics (CFD)-based process modeling, statistical design of experiments (DoE), and microstructural characterization techniques were combined to produce metallurgically bonded single-crystal deposits of more than 500 μm height in a single pass along the entire length of the substrate. A customized quantitative metallography based image analysis technique was employed for automatic extraction of various deposit quality metrics from the digital cross-sectional micrographs. The processing parameters were varied, and optimal processing windows were identified to obtain good quality deposits. The results reported here represent one of the few successes obtained in producing single-crystal epitaxial deposits through a powder bed fusion-based metal AM process and thus demonstrate the potential of SLE to repair and manufacture single-crystal hot section components of gas turbine systems from nickel-based superalloy powders.

  16. Thermomechanical and isothermal fatigue behavior of bare and coated superalloys

    SciTech Connect

    Kadioglu, Y.; Sehitoglu, H.

    1996-01-01

    Thermomechanical fatigue (TMF) and isothermal fatigue (IF) experiments were performed on bare Mar-M246 as well as bare and coated Mar-M247 nickel based superalloys at strain ranges from 0.335 to 1 percent. The experiments were conducted in air, through a temperature range of 500 to 1,038 C at a constant strain rate of 5.0 {times} 10{sup {minus}5} s{sup {minus}1}. Due to the coarse-grained structure of Mar-M246, TMF lives scattered considerably under low strain range conditions. Electron microscopy studies show that significant surface oxidation and gamma prime, {gamma}{prime}, depleted zones occur for Mar-M246 under these conditions. In the surface grain, where the change in {gamma}{prime} morphology is most pronounced, {gamma}{prime} rafted along axes {approx}{+-}45 deg from the loading axis. The influence of a protective coating on the IF and TMF lives of Mar-M247 was also examined. Results indicate that the coating does not significantly affect the fatigue lives of Mar-M247. The oxidation behavior of bare and coating Mar-M247 was investigated via X-ray microprobe and Auger Spectroscopy. Through these analyses, it is evident that the coating was completely degraded when exposed to the test environment for a long time. In both Mar-M246 and Mar-M247, in-phase thermomechanical fatigue (TMF IP) loading resulted in intergranular cracking. TMF IP loading promoted multiple cracks at the coating/substrate interface of coating Mar-M247. Finally, Eshelby techniques were used to calculate stress distributions in the vicinity of a surface oxide and second-phase particle at the coating/substrate interface.

  17. Microstructural aspects of fatigue in Ni-base superalloys.

    PubMed

    Antolovich, Stephen D

    2015-03-28

    Nickel-base superalloys are primarily used as components in jet engines and land-based turbines. While compositionally complex, they are microstructurally simple, consisting of small (50-1000 nm diameter), ordered, coherent Ni(3)(Al,Ti)-type L1(2) or Ni(3)Nb-type DO(22) precipitates (called γ(') and γ(''), respectively) embedded in an FCC substitutional solid solution consisting primarily of Ni and other elements which confer desired properties depending upon the application. The grain size may vary from as small as 2 μm for powder metallurgy alloys used in discs to single crystals the actual size of the component for turbine blades. The fatigue behaviour depends upon the microstructure, deformation mode, environment and cycle time. In many cases, it can be controlled or modified through small changes in composition which may dramatically change the mechanism of damage accumulation and the fatigue life. In this paper, the fundamental microstructural, compositional, environmental and deformation mode factors which affect fatigue behaviour are critically reviewed. Connections are made across a range of studies to provide more insight. Modern approaches are pointed out in which the wealth of available microstructural, deformation and damage information is used for computerized life prediction. The paper ends with a discussion of the very important and highly practical subject of thermo-mechanical fatigue (TMF). It is shown that physics-based modelling leads to significantly improved life prediction. Suggestions are made for moving forward on the critical subject of TMF life prediction in notched components. PMID:25713453

  18. Method for improve x-ray diffraction determinations of residual stress in nickel-base alloys

    DOEpatents

    Berman, Robert M.; Cohen, Isadore

    1990-01-01

    A process for improving the technique of measuring residual stress by x-ray diffraction in pieces of nickel-base alloys which comprises covering part of a predetermined area of the surface of a nickel-base alloy with a dispersion, exposing the covered and uncovered portions of the surface of the alloy to x-rays by way of an x-ray diffractometry apparatus, making x-ray diffraction determinations of the exposed surface, and measuring the residual stress in the alloy based on these determinations. The dispersion is opaque to x-rays and serves a dual purpose since it masks off unsatisfactory signals such that only a small portion of the surface is measured, and it supplies an internal standard by providing diffractogram peaks comparable to the peaks of the nickel alloy so that the alloy peaks can be very accurately located regardless of any sources of error external to the sample.

  19. Method for improving x-ray diffraction determinations of residual stress in nickel-base alloys

    DOEpatents

    Berman, R.M.; Cohen, I.

    1988-04-26

    A process for improving the technique of measuring residual stress by x-ray diffraction in pieces of nickel-base alloys is discussed. Part of a predetermined area of the surface of a nickel-base alloy is covered with a dispersion. This exposes the covered and uncovered portions of the surface of the alloy to x-rays by way of an x-ray diffractometry apparatus, making x-ray diffraction determinations of the exposed surface, and measuring the residual stress in the alloy based on these determinations. The dispersion is opaque to x-rays and serves a dual purpose, since it masks off unsatisfactory signals such that only a small portion of the surface is measured, and it supplies an internal standard by providing diffractogram peaks comparable to the peaks of the nickel alloy so that the alloy peaks can be very accurately located regardless of any sources of error external to the sample. 2 figs.

  20. Recent progress in studies of metallic nickel and nickel-based nanoparticles' genotoxicity and carcinogenicity.

    PubMed

    Magaye, Ruth; Zhao, Jinshun

    2012-11-01

    Recently, nanoparticles have been the focus of many research and innovation. Metallic nickel and nickel-based nanoparticles are among those being exploited. Nickel fine particles are known to be genotoxic and carcinogenic. It has been discovered that many properties of nano sized elements and materials are not present in their bulk states. The nano size of these particles renders them the ability to be easily transported into biological systems, thus raising the question of their effects on the susceptible system. Therefore scientific research on the effects of nickel nanoparticles is important. This mini-review intends to summarize the current knowledge on the genotoxicity and carcinogenicity potential of metallic nickel and nickel-based nanoparticles implicated in in vitro and in vivo mammalian studies. PMID:23000472

  1. Superalloy resources: Supply and availability

    NASA Technical Reports Server (NTRS)

    Stephens, Joseph R.

    1987-01-01

    Over the past several decades there have been shortages of strategic materials because of our near total import dependence on such metals as chromium, cobalt, and tantalum. In response to the continued vulnerability of U.S. superalloy producers to disruptions in resource supplies, NASA has undertaken a program to address alternatives to the super-alloys containing significant quantities of the strategic materials such as chromium, cobalt, niobium, and tantalum. The research program called Conservation of Strategic Aerospace Materials (COSAM) focuses on substitution, processing, and alternate materials to achieve its goals. In addition to NASA Lewis Research Center, universities and industry play an important role in the COSAM Program. This paper defines what is meant by strategic materials in the aerospace community, presents a strategic materials index, and reviews the resource supply and availability picture from the U.S. point of view. In addition, research results from the COSAM Program are highlighted and future directions for the use of low strategic material alloys or alternate materials are discussed.

  2. Method of Making a Nickel Fiber Electrode for a Nickel Based Battery System

    NASA Technical Reports Server (NTRS)

    Britton, Doris L. (Inventor)

    2001-01-01

    The general purpose of the invention is to develop a high specific energy nickel electrode for a nickel based battery system. The invention discloses a method of producing a lightweight nickel electrode which can be cycled to deep depths of discharge (i.e., 40% or greater of electrode capacity). These deep depths of discharge can be accomplished by depositing the required amount of nickel hydroxide active material into a lightweight nickel fiber substrate.

  3. Corrosion behavior of iron and nickel base alloys under solid oxide fuel cell exposure conditions

    SciTech Connect

    Ziomek-Moroz, M.; Holcomb, G.R.; Covino, B.S., Jr.; Bullard, S.J.

    2006-03-01

    Topography and phase composition of the scales formed on commercial ferritic stainless steels and experimental low CTE nickel-based alloys were studied in atmospheres simulating solid oxide fuel cell (SOFC) environments. The materials were studied under dual environment conditions with air on one side of the sample and carbon monoxide on the other side at 750°C. Surface characterization techniques, such as scanning electron microscopy and X-ray diffraction analysis were used in this study.

  4. The strengthening mechanism of a nickel-based alloy after laser shock processing at high temperatures

    NASA Astrophysics Data System (ADS)

    Li, Yinghong; Zhou, Liucheng; He, Weifeng; He, Guangyu; Wang, Xuede; Nie, Xiangfan; Wang, Bo; Luo, Sihai; Li, Yuqin

    2013-10-01

    We investigated the strengthening mechanism of laser shock processing (LSP) at high temperatures in the K417 nickel-based alloy. Using a laser-induced shock wave, residual compressive stresses and nanocrystals with a length of 30-200 nm and a thickness of 1 μm are produced on the surface of the nickel-based alloy K417. When the K417 alloy is subjected to heat treatment at 900 °C after LSP, most of the residual compressive stress relaxes while the microhardness retains good thermal stability; the nanocrystalline surface has not obviously grown after the 900 °C per 10 h heat treatment, which shows a comparatively good thermal stability. There are several reasons for the good thermal stability of the nanocrystalline surface, such as the low value of cold hardening of LSP, extreme high-density defects and the grain boundary pinning of an impure element. The results of the vibration fatigue experiments show that the fatigue strength of K417 alloy is enhanced and improved from 110 to 285 MPa after LSP. After the 900 °C per 10 h heat treatment, the fatigue strength is 225 MPa the heat treatment has not significantly reduced the reinforcement effect. The feature of the LSP strengthening mechanism of nickel-based alloy at a high temperature is the co-working effect of the nanocrystalline surface and the residual compressive stress after thermal relaxation.

  5. Mechanistic study of nickel based catalysts for oxygen evolution and methanol oxidation in alkaline medium

    NASA Astrophysics Data System (ADS)

    Chen, Dayi; Minteer, Shelley D.

    2015-06-01

    Nickel based catalysts have been studied as catalysts for either organic compound (especially methanol) oxidation or oxygen evolution reactions in alkaline medium for decades, but methanol oxidation and oxygen evolution reactions occur at a similar potential range and pH with nickel based catalysts. In contrast to previous studies, we studied these two reactions simultaneously under various pH and methanol concentrations with electrodes containing a series of NiOOH surface concentrations. We found that nickel based catalysts are more suitable to be used as oxygen evolution catalysts than methanol oxidation catalysts based on the observation that: The rate-determining step of methanol oxidation involves NiOOH, OH- and methanol while high methanol to OH- ratio could poison the NiOOH sites. Since NiOOH is involved in the rate-determining step, methanol oxidation suffers from high overpotential and oxygen evolution is favored over methanol oxidation in the presence of an equivalent amount (0.1 M) of alkali and methanol.

  6. Effect of Process Variables on the Inertia Friction Welding of Superalloys LSHR and Mar-M247

    NASA Astrophysics Data System (ADS)

    Mahaffey, D. W.; Senkov, O. N.; Shivpuri, R.; Semiatin, S. L.

    2016-08-01

    The effect of inertia friction welding process parameters on microstructure evolution, weld plane quality, and the tensile behavior of welds between dissimilar nickel-base superalloys was established. For this purpose, the fine-grain, powder metallurgy alloy LSHR was joined to coarse-grain cast Mar-M247 using a fixed level of initial kinetic energy, but different combinations of the flywheel moment of inertia and initial rotation speed. It was found that welds made with the largest moment of inertia resulted in a sound bond with the best microstructure and room-temperature tensile strength equal to or greater than that of the parent materials. A relationship between the moment of inertia and weld process efficiency was established. The post-weld tensile behavior was interpreted in the context of observed microstructure gradients and weld-line defects.

  7. TEM, HRTEM, electron holography and electron tomography studies of gamma' and gamma'' nanoparticles in Inconel 718 superalloy.

    PubMed

    Dubiel, B; Kruk, A; Stepniowska, E; Cempura, G; Geiger, D; Formanek, P; Hernandez, J; Midgley, P; Czyrska-Filemonowicz, A

    2009-11-01

    The aim of the study was the identification of gamma' and gamma'' strengthening precipitates in a commercial nickel-base superalloy Inconel 718 (Ni-19Fe-18Cr-5Nb-3Mo-1Ti-0.5Al-0.04C, wt %) using TEM dark-field, HRTEM, electron holography and electron tomography imaging. To identify gamma' and gamma'' nanoparticles unambiguously, a systematic analysis of experimental and theoretical diffraction patterns were performed. Using HRTEM method it was possible to analyse small areas of precipitates appearance. Electron holography and electron tomography techniques show new possibilities of visualization of gamma' and gamma'' nanoparticles. The analysis by means of different complementary TEM methods showed that gamma'' particles exhibit a shape of thin plates, while gamma' phase precipitates are almost spherical. PMID:19903242

  8. Cyclic-loading-induced Accumulation of Geometrically Necessary Dislocations Near Grain Boundaries in an Ni-based Superalloy

    SciTech Connect

    Huang, E-Wen; Barabash, Rozaliya I.; Ice, Gene E.; Liu, Wenjun; Liu, Yee-Lang; Kai, Ji-Jung; Liaw, Peter K.

    2011-12-14

    In this study, the fatigue-induced microstructure produced in a nickel-based polycrystalline superalloy that was subjected to cyclic loading was characterized by polychromatic x-ray microdiffraction (PXM) together with in-situ neutron diffraction and transmission-electron microscopy (TEM). In-situ neutron-diffraction measurements reveal two distinct stages of the fatigue damage: cyclic hardening followed by cyclic softening. Three-dimensional spatially resolved PXM micro-Laue measurements find an increase in the density of geometrically necessary dislocations near the grain boundaries, which is accompanied by lattice rotations and grain subdivisions. The PXM results are in agreement with the in-situ neutron-diffraction and TEM results.

  9. Cyclic-loading-induced accumulation of geometrically necessary dislocations near grain boundaries in a an ni-based superalloy.

    SciTech Connect

    Huang, E. W.; Barabash, R. I.; Ice, G. I.; Liu, W.; Liu, Y. L.; Kai, J. J.; Liaw, P. K.; Univ.of Tennessee; ORNL; Tsing-Hua Univ.

    2009-01-01

    In this study, the fatigue-induced microstructure produced in a nickel-based polycrystalline superalloy that was subjected to cyclic loading was characterized by polychromatic x-ray microdiffraction (PXM) together with in-situ neutron diffraction and transmission-electron microscopy (TEM). In-situ neutron-diffraction measurements reveal two distinct stages of the fatigue damage: cyclic hardening followed by cyclic softening. Three-dimensional spatially resolved PXM micro-Laue measurements find an increase in the density of geometrically necessary dislocations near the grain boundaries, which is accompanied by lattice rotations and grain subdivisions. The PXM results are in agreement with the in-situ neutron-diffraction and TEM results.

  10. An empirical-statistical model for coaxial laser cladding of NiCrAlY powder on Inconel 738 superalloy

    NASA Astrophysics Data System (ADS)

    Ansari, M.; Shoja Razavi, R.; Barekat, M.

    2016-12-01

    In this study, coaxial laser cladding of NiCrAlY powder on a nickel-based superalloy is investigated from an experimental point of view so as to propose an empirical-statistical model for the process. The correlations between main processing parameters (i.e. scanning speed, powder feeding rate, and laser power) and geometrical characteristics (i.e. width, height, penetration depth, dilution and wetting angle) of single clad tracks have been predicted and are discussed using regression analysis (RA). The validity of the predictions is confirmed by providing correlation coefficient and analysis of the residuals. The correlations are established as a combined parameter (PαVβFγ) for each studied characteristic of single clad tracks. These correlations finally lead to the design of a processing map that can be practically used to select proper processing parameters for laser cladding of the particular material.

  11. Low expansion superalloy with improved toughness

    DOEpatents

    Smith, Darrell F.; Stein, Larry I.; Hwang, Il S.

    1995-01-01

    A high strength, low coefficient of thermal expansion superalloy exhibiting improved toughness over a broad temperature range down to about 4.degree. K. The composition is adapted for use with wrought superconducting sheathing.

  12. Low expansion superalloy with improved toughness

    DOEpatents

    Smith, D.F.; Stein, L.I.; Hwang, I.S.

    1995-06-20

    A high strength, low coefficient of thermal expansion superalloy exhibiting improved toughness over a broad temperature range down to about 4 K is disclosed. The composition is adapted for use with wrought superconducting sheathing.

  13. Fiber reinforced superalloys for rocket engines

    NASA Technical Reports Server (NTRS)

    Petrasek, Donald W.; Stephens, Joseph R.

    1988-01-01

    High-pressure turbopumps for advanced reusable liquid-propellant rocket engines such as that for the Space Shuttle Main Engine (SSME) require turbine blade materials that operate under extreme conditions of temperature, hydrogen environment, high-cycle fatigue loading, thermal fatigue and thermal shock. Such requirements tax the capabilities of current blade materials. Based on projections of properties for tungsten fiber reinforced superalloy (FRS) composites, it was concluded that FRS turbine blades offer the potential of a several-fold increase in life and over a 200C increase in temperature capability over current SSME blade material. FRS composites were evaluated with respect to mechanical property requirements for SSME blade applications. Compared to the current blade material, the thermal shock resistance of FRS materials is excellent, two to nine times better, and their thermal fatigue resistance is equal to or higher than the current blade material. FRS materials had excellent low and high-cycle fatigue strengths, and thermal shock-induced surface microcracks had no influence on their fatigue strength. The material also exhibited negligible embrittlement when exposed to a hydrogen environment.

  14. Fiber reinforced superalloys for rocket engines

    NASA Technical Reports Server (NTRS)

    Petrasek, Donald W.; Stephens, Joseph R.

    1989-01-01

    High pressure turbopumps for advanced reusable liquid propellant rocket engines such as that for the Space Shuttle Main Engine (SSME) require turbine blade materials that operate under extreme conditions of temperature, hydrogen environment, high-cycle fatigue loading, thermal fatigue and thermal shock. Such requirements tax the capabilities of current blade materials. Based on projections of properties for tungsten fiber reinforced superalloy (FRS) composites, it was concluded that FRS turbine blades offer the potential of a several fold increase in life and over a 200 C increase in temperature capability over the current SSME blade material. FRS composites were evaluated with respect to mechanical property requirements for SSME blade applications. Compared to the current blade material, the thermal shock resistance of FRS materials is excellent, two to nine times better, and their thermal fatigue resistance is equal to or higher than the current blade material. FRS materials had excellent low and high-cycle fatigue strengths, and thermal shock-induced surface microcracks had no influence on their fatigue strength. The material also exhibited negligible embrittlement when exposed to a hydrogen environment.

  15. Electrodeposition on Superalloy Substrates: a Review

    NASA Astrophysics Data System (ADS)

    Allahyarzadeh, M. H.; Aliofkhazraei, M.; Rouhaghdam, A. Sabour

    2016-02-01

    The present paper reviews various types of coatings, including platinum, platinum alloys, palladium, ruthenium, iridium, nickel, nickel alloys and composite coatings, on superalloy substrates using electrodeposition method. Attempts were carried out to represent an overall view of plating conditions and electrolyte and highlight the importance of the layer regarding to the performance of high-temperature coatings applied on superalloys, which is extensively used on gas-turbine components.

  16. Advanced Stirling Duplex Materials Assessment for Potential Venus Mission Heater Head Application

    NASA Technical Reports Server (NTRS)

    Ritzert, Frank; Nathal, Michael V.; Salem, Jonathan; Jacobson, Nathan; Nesbitt, James

    2011-01-01

    This report will address materials selection for components in a proposed Venus lander system. The lander would use active refrigeration to allow Space Science instrumentation to survive the extreme environment that exists on the surface of Venus. The refrigeration system would be powered by a Stirling engine-based system and is termed the Advanced Stirling Duplex (ASD) concept. Stirling engine power conversion in its simplest definition converts heat from radioactive decay into electricity. Detailed design decisions will require iterations between component geometries, materials selection, system output, and tolerable risk. This study reviews potential component requirements against known materials performance. A lower risk, evolutionary advance in heater head materials could be offered by nickel-base superalloy single crystals, with expected capability of approximately 1100C. However, the high temperature requirements of the Venus mission may force the selection of ceramics or refractory metals, which are more developmental in nature and may not have a well-developed database or a mature supporting technology base such as fabrication and joining methods.

  17. Encapsulation of sulfur with thin-layered nickel-based hydroxides for long-cyclic lithium–sulfur cells

    PubMed Central

    Jiang, Jian; Zhu, Jianhui; Ai, Wei; Wang, Xiuli; Wang, Yanlong; Zou, Chenji; Huang, Wei; Yu, Ting

    2015-01-01

    Elemental sulfur cathodes for lithium/sulfur cells are still in the stage of intensive research due to their unsatisfactory capacity retention and cyclability. The undesired capacity degradation upon cycling originates from gradual diffusion of lithium polysulfides out of the cathode region. To prevent losses of certain intermediate soluble species and extend lifespan of cells, the effective encapsulation of sulfur plays a critical role. Here we report an applicable way, by using thin-layered nickel-based hydroxide as a feasible and effective encapsulation material. In addition to being a durable physical barrier, such hydroxide thin films can irreversibly react with lithium to generate protective layers that combine good ionic permeability and abundant functional polar/hydrophilic groups, leading to drastic improvements in cell behaviours (almost 100% coulombic efficiency and negligible capacity decay within total 500 cycles). Our present encapsulation strategy and understanding of hydroxide working mechanisms may advance progress on the development of lithium/sulfur cells for practical use. PMID:26470847

  18. Superalloy Disk With Dual-Grain Structure Spin Tested

    NASA Technical Reports Server (NTRS)

    Gayda, John; Kantzos, Pete T.

    2003-01-01

    Advanced nickel-base disk alloys for future gas turbine engines will require greater temperature capability than current alloys, but they must also continue to deliver safe, reliable operation. An advanced, nickel-base disk alloy, designated Alloy 10, was selected for evaluation in NASA s Ultra Safe Propulsion Project. Early studies on small test specimens showed that heat treatments that produced a fine grain microstructure promoted high strength and long fatigue life in the bore of a disk, whereas heat treatments that produced a coarse grain microstructure promoted optimal creep and crack growth resistance in the rim of a disk. On the basis of these results, the optimal combination of performance and safety might be achieved by utilizing a heat-treatment technology that could produce a fine grain bore and coarse grain rim in a nickel-base disk. Alloy 10 disks that were given a dual microstructure heat treatment (DMHT) were obtained from NASA s Ultra-Efficient Engine Technology (UEET) Program for preliminary evaluation. Data on small test specimens machined from a DMHT disk were encouraging. However, the benefit of the dual grain structure on the performance and reliability of the entire disk still needed to be demonstrated. For this reason, a high temperature spin test of a DMHT disk was run at 20 000 rpm and 1500 F at the Balancing Company of Dayton, Ohio, under the direction of NASA Glenn Research Center personnel. The results of that test showed that the DMHT disk exhibited significantly lower crack growth than a disk with a fine grain microstructure. In addition, the results of these tests could be accurately predicted using a two-dimensional, axisymmetric finite element analysis of the DMHT disk. Although the first spin test demonstrated a significant performance advantage associated with the DMHT technology, a second spin test on the DMHT disk was run to determine burst margin. The disk burst in the web at a very high speed, over 39 000 rpm, in line with

  19. High-temperature oxidation resistance of sputtered micro-grain superalloy K38G. [Ni-16. 3Cr-8. 4Co-4. 01Al-3. 81Ti-2. 7W-1. 8Mo-1. 75Ta-0. 76Nb

    SciTech Connect

    Lou Hanyi; Wang Fuhui; Xia Bangjie; Zhang Lixin )

    1992-10-01

    The oxidation of sputtered and cast superalloy K38G specimens was studied. The sputtered alloy was microcrystalline, with an average grain size [lt]0.1 [mu]m. The mass gains of the sputtered alloy were much less than those of the cast alloy at 800, 900, and 1,000C up to 500 hr, and were even less than those of pack aluminide on the cast alloy. K38G is a chromia-forming cast nickel-base superalloy, so the oxide scale formed on it is composed of Cr[sub 2]O[sub 3], TiO[sub 2], Al[sub 2]O[sub 3],and a spinel. The oxide scale formed on the sputtered alloy was Al[sub 2]O[sub 3]. This scale is thin, compact, and adherent. This result implied that microcrystallization reduced the critical aluminum content necessary to form alumina on the surface of this superalloy. No oxide spallation, as typically observed for cast of aluminized alloys, occurred on the sputtered superalloy. The reduction of the critical aluminum content for the formation of alumina and the improvement of the spallation resistance may be attributed to the microcrystalline structure formed during sputtering. The numerous grain boundaries favor outward aluminum grain-boundary diffusion, provide increased nucleation sites, and reduced stresses in the oxide scales.

  20. Effect of high temperature fatigue on the fracture toughness of a nickel-base alloy

    SciTech Connect

    Hwang, S.K.

    1981-01-01

    The purpose of the present work was to investigate the effect of cyclic loading at high temperature on the fracture toughness of a precipitate hardened alloy. A ..gamma..' precipitate hardened Inconcel X-750 alloy was chosen because of its importance in practical applications as well as its relatively well defined microstructure compared to other superalloys. This paper presents a study of the variation of the relative fracture toughness of this alloy during continuous and hold-time fatigue at 973/sup 0/K.

  1. Influence of a magnetic field during directional solidification of MAR-M 246 + Hf superalloy. Final Technical Report

    SciTech Connect

    Andrews, J.B.; Alter, W.; Schmidt, D.

    1991-01-01

    An area that has been almost totally overlooked in the optimization of properties in directionally solidified superalloys is the control of microstructural features through the application of a magnetic field during solidification. The influence of a magnetic field on the microstructural features of a nickel-base superalloys is investigated. Studies were performed on the dendritic MAR-M 246+Hf alloy, which was solidified under both a 5 K gauss magnetic field and under no-applied-field conditions. The possible influences of the magnetic field on the solidification process were observed by studying variations in microstructural features including volume fraction, surface area, number, and shape of the carbide particles. Stereological factors analyzed also included primary and secondary dendrite arm spacing and the volume fraction of the interdendritic eutectic constituent. Microprobe analysis was performed to determine the chemistry of the carbides, dendrites, and interdendritic constituents, and how it varied between field and no-field solidification samples. Experiments involving periodic application and removal of the magnetic field were also performed in order to permit a comparison with structural variations observed in a MAR-M 246+Hf alloy solidified during KC{sup {minus}135} high-g, low-g maneuvers.

  2. Development of a Power Metallurgy Superalloy for Use at 1800-2000 F (980-1090 C)

    NASA Technical Reports Server (NTRS)

    Kortovich, C. S.

    1973-01-01

    A program was conducted to develop a powder metallurgy nickel-base superalloy for 1800-2000 F (980-1090 C) temperature applications. The feasibility of a unique concept for alloying carbon into a superalloy powder matrix and achieving both grain growth and a discrete particle grain boundary carbide precipitation was demonstrated. The process consisted of blending metastable carbides with a carbon free base alloy and consolidating this blend by hot extrusion. This was followed by heat treatment to grow a desired ASTM No. 2-3 grain size and to solution the metastable carbides to allow precipitation of discrete particle grain boundary carbides during subsequent aging heat treatments. The best alloy developed during this program was hydrogen-atomized, thermal-mechanically processed, modified MAR-M246 base alloy plus VC (0.28 w/o C). Although below those for cast MAR-M246, the mechanical properties exhibited by this alloy represent the best combination offered by conventional powder metallurgy processing to date.

  3. Ion irradiation induced disappearance of dislocations in a nickel-based alloy

    NASA Astrophysics Data System (ADS)

    Chen, H. C.; Li, D. H.; Lui, R. D.; Huang, H. F.; Li, J. J.; Lei, G. H.; Huang, Q.; Bao, L. M.; Yan, L.; Zhou, X. T.; Zhu, Z. Y.

    2016-06-01

    Under Xe ion irradiation, the microstructural evolution of a nickel based alloy, Hastelloy N (US N10003), was studied. The intrinsic dislocations are decorated with irradiation induced interstitial loops and/or clusters. Moreover, the intrinsic dislocations density reduces as the irradiation damage increases. The disappearance of the intrinsic dislocations is ascribed to the dislocations climb to the free surface by the absorption of interstitials under the ion irradiation. Moreover, the in situ annealing experiment reveals that the small interstitial loops and/or clusters induced by the ion irradiation are stable below 600 °C.

  4. Laser-Aided Direct Writing of Nickel-Based Single-Crystal Super Alloy (N5)

    NASA Astrophysics Data System (ADS)

    Wang, Yichen; Choi, Jeongyoung; Mazumder, Jyoti

    2016-09-01

    This communication reports direct writing of René N5 nickel-based Super alloy. N5 powder was deposited on (100) single-crystal substrate of René N5, for epitaxial growth, using laser and induction heating with a specially designed closed-loop thermal control system. A thin wall (1 mm width) of René N5 single crystal of 22.1 mm (including 3 mm SX substrate) in height was successfully deposited within 100 layers. SEM and EBSD characterized the single-crystal nature of the deposit.

  5. Interface reaction between nickel-base self-fluxing alloy coating and steel substrate

    NASA Astrophysics Data System (ADS)

    Otsubo, F.; Era, H.; Kishitake, K.

    2000-06-01

    The interface reaction between a nickel-base, self-fluxing alloy coating and a steel substrate has been investigated to examine the formation of “pores,” which are observed along the interface of used boiler tubes. It was found that lumpy precipitates form along the interface instead of pores after heating at high temperatures and that the precipitates are of Fe2B boride. The adhesion strength of the coating is not decreased by the formation of Fe2B precipitates along the interface because of the increase of the adhesion due to interdiffusion.

  6. Thermal and mechanical treatments for nickel and some nickel-base alloys: Effects on mechanical properties

    NASA Technical Reports Server (NTRS)

    Hall, A. M.; Beuhring, V. F.

    1972-01-01

    This report deals with heat treating and working nickel and nickel-base alloys, and with the effects of these operations on the mechanical properties of the materials. The subjects covered are annealing, solution treating, stress relieving, stress equalizing, age hardening, hot working, cold working, combinations of working and heat treating (often referred to as thermomechanical treating), and properties of the materials at various temperatures. The equipment and procedures used in working the materials are discussed, along with the common problems that may be encountered and the precautions and corrective measures that are available.

  7. Evaluation of commercially available coating techniques for application of thermographic phosphor to nickel-based alloys

    SciTech Connect

    Beshears, D.L.; Bridges, M.J.; Harris, L.A.

    1986-04-01

    Remote temperature measurements using laser-induced fluorescence of phosphors has been established for temperatures ranging from room temperature to 1200/sup 0/C. This remote surface thermometry requires that the phosphors be firmly bonded to the surface of interest. The intent of this paper is to take a quick look at several bonding techniques used to bond the thermographic phosphor yttrium oxide doped with europium (Y/sub 2/O/sub 3/:Eu) to nickel-based alloy. The evaluation of the samples were performed after the samples had been subjected to extreme heat and, in some cases, mechanically deformed.

  8. Stack linings in high-alloy stainless steels and nickel-base alloys

    SciTech Connect

    Herda, W.R.; Grossmann, G.K.

    1999-11-01

    In power stations as well as in waste incineration plants, the stack is the last component in which residues and condensates can separate from the treated flue gas. The process of condensate formation due to temperatures below dewpoint, and the extreme corrosiveness of specific condensates are discussed in detail. Stack lining, using an appropriately corrosion-resistant metallic material, has proven to be an effective means of corrosion protection. Selected high-alloy stainless steels and nickel-base alloys, particularly well suited to this application, are introduced. The various techniques available for fitting such highly corrosion resistant linings are described in selected case histories.

  9. Thermogravimetric study of reduction of oxides present in oxidized nickel-base alloy powders

    NASA Technical Reports Server (NTRS)

    Herbell, T. P.

    1976-01-01

    Carbon, hydrogen, and hydrogen plus carbon reduction of three oxidized nickel-base alloy powders (a solid solution strengthened alloy both with and without the gamma prime formers aluminum and titanium and the solid solution strengthened alloy NiCrAlY) were evaluated by thermogravimetry. Hydrogen and hydrogen plus carbon were completely effective in reducing an alloy containing chromium, columbium, tantalum, molybdenum, and tungsten. However, with aluminum and titanium present the reduction was limited to a weight loss of about 81 percent. Carbon alone was not effective in reducing any of the alloys, and none of the reducing conditions were effective for use with NiCrAlY.

  10. Effects of Long Term Exposures on PM Disk Superalloys

    NASA Technical Reports Server (NTRS)

    Gabb, T. P.; Sudbrack, C. K.; Draper, S. L.; MacKay, R. A.; Telesman, J.

    2013-01-01

    Turbine disks in some advanced engine applications may be exposed to temperatures above 700 C for extended periods of time, approaching 1,000 h. These exposures could affect the near-surface composition and microstructure through formation of damaged and often embrittled layers. The creation of such damaged layers could significantly affect local mechanical properties. Powder metal disk superalloys LSHR and ME3 were exposed at temperatures of 704, 760, and 815 C for times up to 2,020 h, and the types and depths of environmental attacked were measured. Fatigue tests were performed for selected cases at 704 and 760 C, to determine the impact of these exposures on fatigue life. Fatigue resistance was reduced up to 98% in both superalloys for some exposure conditions. Tensile tests were also performed to help understand fatigue responses, and showed corresponding reductions in ductility. The changes in surface composition and phases, depths of these changed layers, failure responses, and failure initiation modes were compared.

  11. Joint Development of a Fourth Generation Single Crystal Superalloy

    NASA Technical Reports Server (NTRS)

    Walston, S.; Cetel, A.; MacKay, R.; OHara, K.; Duhl, D.; Dreshfield, R.

    2004-01-01

    A new, fourth generation, single crystal superalloy has been jointly developed by GE Aircraft Engines, Pratt & Whitney, and NASA. The focus of the effort was to develop a turbine airfoil alloy with long-term durability for use in the High Speed Civil Transport. In order to achieve adequate long-time strength improvements at moderate temperatures and retain good microstructural stability, it was necessary to make significant composition changes from 2nd and 3rd generation single crystal superalloys. These included lower chromium levels, higher cobalt and rhenium levels and the inclusion of a new alloying element, ruthenium. It was found that higher Co levels were beneficial to reducing both TCP precipitation and SRZ formation. Ruthenium caused the refractory elements to partition more strongly to the ' phase, which resulted in better overall alloy stability. The final alloy, EPM 102, had significant creep rupture and fatigue improvements over the baseline production alloys and had acceptable microstructural stability. The alloy is currently being engine tested and evaluated for advanced engine applications.

  12. High-temperature microstructural stability in iron- and nickel-base alloys from rapid solidification processing

    SciTech Connect

    Flinn, J.E. ); Bae, J.C.; Kelly, T.F. )

    1991-08-01

    The properties and performance of metallic alloys for heat resistant applications depend on the fineness, homogeneity, and stability of their microstructures, particularly after high temperature exposures. Potential advantages of rapid solidification processing (RSP) of alloys for such applications are the homogeneity in composition and fine microstructural features derived from the nature of the RSP process. The main RSP product form is powder, is which obtained by atomizing a narrow melt stream into fine molten droplets. Rapid cooling of the droplets is typically achieved through convective cooling with noble gases such as argon or helium. Consolidation of RSP powder, either using near-net-shape methods or into forms that can be converted to final product shapes, requires exposures to fairly high temperatures, usually 900 to 1200{degrees}C for iron- and nickel-base alloys. Full consolidation, i.e., complete densification with accompanying particle bonding, usually requires pressure or stress assistance. Consolidation, as well as any subsequent thermal-mechanical processing, may affect the chemical homogeneity and fine microstructures. A study has been performed on a series of RSP iron- and nickel-base alloys. The results of microstructure examinations and mechanical properties tests of the consolidated powders, and their correlation, will be covered in this paper. 14 refs., 10 figs., 1 tab.

  13. Underwater wet flux-cored arc welding development of stainless steel and nickel-based materials

    SciTech Connect

    Findlan, S.J.; Frederick, G.J.

    1995-12-31

    The inaccessibility and high radiation fields of components in the lower two thirds of a reactor pressure vessel (RPV) has generated the need for an automated underwater wet welding process to address repair applications. Mechanical methods presently employed for this type of repair application produce crevices, which promote concerns of intergranular stress corrosion cracking (IGSCC), crevice corrosion and pitting. To address these concerns, the EPRI Repair and Replacement Applications Center (RRAC) has developed underwater wet flux-cored arc welding (FCAW) technology for the welding of stainless steel and nickel based materials. The benefits of underwater wet welding include: (1) provides a permanent repair; (2) offers crevice-five conditions; (3) reduces future inspection requirements (4) eliminates the potential for ``loose parts`` (5) can be performed in a timely approach. Underwater wet shielded metal arc welding (SMAW) has been successfully used to repair components in radiation areas of the upper section of the RPV, although this process is a manual operation and is impractical for remote applications. The developmental work at the EPRI RRAC is directed towards remote repair applications of nickel-based and stainless steel components, which are inaccessible with normal manual repair techniques, e.g., access hole covers. The flux-cored arc welding process (FCAW) was considered a viable option for underwater development, due to the ease of automation, out of position welding proficiency and self-shielding capabilities.

  14. Laser rapid manufacturing of special pattern Inco 718 nickel-based alloy component

    NASA Astrophysics Data System (ADS)

    Zhong, Minlin; Yang, Lin; Liu, Wenjin; Huang, Ting; He, Jingjiang

    2005-01-01

    Laser rapid manufacturing based on laser cladding is a novel layer additive manufacturing technology, which can be well used for producing specific material, geometry and properties components normally unavailable or very costly by conventional methods. This paper presents a project research work on laser rapid manufacturing of special pattern Inco 718 nickel based alloy component with special pattern for aeronautical application. The required pattern Inco 718 nickel based alloy component was manufactured directly by laser deposition with optimized parameters: laser power: 800W, laser beam diameter: 0.8 mm, scanning speed: 0.5 m/min, powder feeding rate: 3g/min; The basic microstructure of laser deposited sample is directionally solidified columnar structure, with metallurgical bound to the substrate. Laser deposited component has good metallurgical and compositional and hardness homogeneity. The average hardness is about Hv0.2 440. The tensile strength of the laser deposited Inco 718 sample is respectively 121 and 116 kgf/mm2 at room temperature and at 650°C, which are a little bit less than the data of forged Inco 718 plate 142 and 127 kgf/mm2 due to its directional solidified columnar structure perpendicular to the tensile test force.

  15. Application of single crystal superalloys for Earth-to-orbit propulsion systems

    NASA Technical Reports Server (NTRS)

    Dreshfield, R. L.; Parr, R. A.

    1987-01-01

    Single crystal superalloys were first identified as potentially useful engineering materials for aircraft gas turbine engines in the mid-1960's. Although they were not introduced into service as turbine blades in commercial aircraft engines until the early 1980's, they have subsequently accumulated tens of millions of flight hours in revenue producing service. The space shuttle main engine (SSME) and potential advanced earth-to-orbit propulsion systems impose severe conditions on turbopump turbine blades which for some potential failure modes are more severe than in aircraft gas turbines. Research activities which are directed at evaluating the potential for single crystal superalloys for application as turbopump turbine blades in the SSME and advanced rocket engines are discussed. The mechanical properties of these alloys are summarized and the effects of hydrogen are noted. The use of high gradient directional solidification and hot isostatic pressing to improve fatigue properties is also addressed.

  16. Application of single crystal superalloys for earth-to-orbit propulsion systems

    NASA Technical Reports Server (NTRS)

    Dreshfield, R. L.; Parr, R. A.

    1987-01-01

    Single crystal superalloys were first identified as potentially useful engineering materials for aircraft gas turbine engines in the mid-1960s. Although they were not introduced into service as turbine blades in commercial aircraft engines until the early 1980's, they have subsequently accumulated tens of millions of flight hours in revenue producing service. The Space Shuttle main engine (SSME) and potential advanced earth-to-orbit propulsion systems impose severe conditions on turbopump turbine blades which for some potential failure modes are more severe than in aircraft gas turbines. Research activities which are directed at evaluating the potential for single crystal superalloys for application as turbopump turbine blades in the SSME and advanced rocket engines are discussed. The mechanical properties of these alloys are summarized and the effects of hydrogen are noted. The use of high gradient directional solidification and hot isostatic pressing to improve fatigue properties is also addressed.

  17. Low coefficient of thermal expansion (CTE) nickel-base superalloys for interconnect application in intermediate high temperature solid oxide fuel cells

    SciTech Connect

    Alman, David E.; Jablonski, Paul D.

    2004-09-01

    This paper deals with the fabrication, microstructure and oxidation resistance of Ni-base alloys with CTE on the order of 12.5x10{sup}-6{/sup}/°C. Alloys based on the composition Ni-(18-22wt%) Mo-12Cr-1Ti were readily rolled into 1 mm strip. Modifications to this base composition, such as increasing Cr or Ti content adversely affected the ability to form the alloy. The oxidation resistance at 750°C of several of these alloys was superior to a Fe-base alloy containing significantly more (22wt%) Cr.

  18. Effects of rare earth yttrium on microstructure and properties of Ni–16Mo–7Cr–4Fe nickel-based superalloy

    SciTech Connect

    Li, X.L.; He, S.M.; Zhou, X.T.; Zou, Y.; Li, Z.J.; Li, A.G.; Yu, X.H.

    2014-09-15

    Effects of rare earth yttrium on microstructure of Ni–16Mo–7Cr–4Fe alloy were examined by optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray fluorescence. M{sub 6}C phase was observed in the alloys with and without yttrium addition, and Ni{sub 17}Y{sub 2} phase existed in the alloys containing 0.05–0.43 wt.% yttrium simultaneously. The amount of Ni{sub 17}Y{sub 2} phase increased as yttrium concentration increased. When the concentration of yttrium increased to 0.43 wt.%, some multi-precipitated phase regions appeared in the form of large amount of coarse Ni{sub 3}Y phase surrounded by M{sub 6}C phase and γ phase in the alloy. Influences of rare earth yttrium on high temperature static oxidation and mechanical properties of Ni–16Mo–7Cr–4Fe alloy were also investigated. The alloy containing 0.05 wt.% yttrium showed the best oxidation resistance and mechanical properties simultaneously. The adequate concentration of yttrium at grain boundary and in the solid-solution (γ phase) and the adhesion enhancement of the outer oxidation scale to the substrate are key factors for the improvements in the mechanical properties and oxidation resistance respectively. - Highlights: • When the content of yttrium reaches to 0.43%, some multiphase regions appear. • When the content of yttrium reaches to 0.43%, some Ni{sub 17}Y{sub 2} chains appear. • The morphology of M{sub 6}C changes with increasing concentration of yttrium. • The Ni–16Mo–7Cr–4Fe alloy with 0.05% yttrium performs the best mechanical property. • The Ni–16Mo–7Cr–4Fe alloy with 0.05% yttrium performs the best oxidation resistance.

  19. Influence of cobalt, tantaum and tungsten on the high temperature mechanical properties of single crystal nickel-base superalloys. Ph.D. Thesis - Case Western Reserve Univ.

    NASA Technical Reports Server (NTRS)

    Nathal, M. V.

    1984-01-01

    For alloys with the baseline refractory metal level of 3 percent Ta and 10 percent W, decreases in Co level from 10 to 0 percent resulted in increased tensile strength and creep resistance. Substitution of W for Ta resulted in decreased creep life at high stresses but improved life at low stresses. Substitution of Ni for Ta caused large reductions in tensile strength and creep resistance, and corresponding increases in ductility. For these alloys with low Ta plus W totals, strength was independent of Co level. The increases in tensile strength with increases in refractory metal content were related to the increases in gamma volume fraction and solid solution hardening. Increases in strength as Co level decreased were considered to be the result of coherency strain hardening from the increased lattice mismatch. Dislocation shear through the gamma-gamma interface is considered to be the rate limiting step in the deformation process.

  20. The effect of tantalum and carbon on the structure/properties of a single crystal nickel-base superalloy. M.S. Thesis. Final Report

    NASA Technical Reports Server (NTRS)

    Nguyen, H. C.

    1984-01-01

    The microstructure, phase chemistry, and creep and hot tensile properties were studied as a function of tantalum and carbon levels in Mar-M247 type single crystal alloys. Microstructural studies showed that several types of carbides (MC, M23C6 and M5C) are present in the normal carbon (0.10 wt % C) alloys after heat treatment. In general, the composition of the MC carbides changes from titanium rich to tantalum rich as the tantalum level in the alloy increases. Small M23C6 carbides are present in all alloys. Tungsten rich M6C carbides are also observed in the alloy containing no tantalum. No carbides are present in the low carbon (0.01 wt % C) alloy series. The morphology of gamma prime is observed to be sensitive to heat treatment and tantalum level in the alloy. Cuboidal gamma prime is present in all the as cast structures. After heat treatment, the gamma prime precipitates tend to have a more spheroidal like morphology, and this tendency increases as the tantalum level decreases. On prolonged aging, the gamma prime reverts back to a cuboidal morphology or under stress at high temperatures, forms a rafted structure. The weight fraction and lattice parameter of the spheroidal gamma prime increases with increasing tantalum content. Changes in the phase chemistry of the gamma prime matrix and gamma prime have also been analyzed using phase extraction techniques. The partitioning ratio decreases for tungsten and aluminum and increases for tantalum as the tantalum content increases for both alloy series; no significant changes occur in the partitioning ratios of the other alloying elements. A reduction in secondary creep rate and an increase in rupture time result from increasing the tantalum content and decreasing the carbon level.

  1. A Constitutive Model for the Inelastic Multiaxial Cyclic Response of a Nickel Base Superalloy Rene 80. Ph.D. Thesis. Final Report

    NASA Technical Reports Server (NTRS)

    Ramaswamy, V. G.

    1986-01-01

    The objective was to develop unified constitutive equations which can model a variety of nonlinear material phenomena observed in Rene 80 at elevated temperatures. A constitutive model was developed based on back stress and drag stress. The tensorial back stress was used to model directional effects; whereas, the scalar drag stress was used to model isotropic effects and cyclic hardening or softening. A flow equation and evolution equations for the state variables were developed in multiaxial form. Procedures were developed to generate the material parameters. The model predicted very well the monotonic tensile, cyclic, creep, and stress relaxation behavior of Rene 80 at 982 C. The model was then extended to 871, 760, and 538 C. It was shown that strain rate dependent behavior at high temperatures and strain rate independent behavior at the lower temperatures could be predicted very well. A large number of monotonic tensile, creep, stress relation, and cyclic experiments were predicted. The multiaxial capabilities of the model were verified extensively for combined tension/torsion experiments. The prediction of the model agreed very well for proportional, nonproportional, and pure shear cyclic loading conditions at 982 and 871 C.

  2. Environmentally enhanced crack growth in nickle-based superalloys

    NASA Astrophysics Data System (ADS)

    Huang, Zhifan Frank

    This dissertation research was designed to develop a better understand the role of niobium and other strengthening elements in enhancing crack growth by oxygen in nickel-based superalloys at high temperatures. It included modeling of diffusion controlled crack growth coupled with oxidation ahead of the crack tip, and an examination of the relationship between crack growth under sustained and fatigue loading. Three gamma' strengthened powder metallurgy (P/M) alloys (having about 53 vol. pct of gamma' precipitates), with 0, 2.5 and 5 wt pct niobium and with the formation of gamma″ precipitates suppressed, were specially designed for this study. Crack growth and supporting microstructural studies were conducted on the alloys. They were complemented by a separate surface chemistry study of the alloys, key precipitates, fracture surfaces of interrupted crack growth specimens by x-ray photoelectron spectroscopy (XPS). The results showed that sustained load and fatigue crack growth are directly related. Crack growth rates were significantly enhanced by oxygen, increasing by about 104 and 103 over those in argon (at 973 K) in the Nb containing and Nb free alloys, respectively. Crack growth was thermally activated, with an average apparent activation energy of about 250 kJ/mol; the actual values depended upon K and the alloys. The observed K dependence suggested oxygen diffusion control of crack growth, and was confirmed by results from the proposed model. Microstructural analyses of grain boundaries demonstrated that the Nb-containing phases were oxidized. The presence of zone of an oxygen affected region (OAR), or embrittled zone, ahead of the growing crack was established mechanically, and confirmed by XPS analyses. The XPS analyses showed preferential oxidization of Nb along with Al and Ti (principally of Nb-rich carbides, Ni3Al and Ni3Ti), but not Ni within the OAR. The results taken in toto show that embrittlement resulted from the formation and rupture of a brittle

  3. Numerical Simulation of Solidification, Homogenization, and Precipitation in an Industrial Ni-Based Superalloy

    NASA Astrophysics Data System (ADS)

    Rougier, Luc; Jacot, Alain; Gandin, Charles-André; Ponsen, Damien; Jaquet, Virginie

    2016-11-01

    A comprehensive simulation approach integrating solidification, homogenization, and precipitation during aging has been used to predict the formation of γ/ γ' microstructures in the AM1 nickel-based superalloy. The particle size distribution of intradendritic γ' precipitates after aging was calculated with a multicomponent diffusion model coupled with CALPHAD thermodynamics for the equilibrium at the interface. The influence of residual microsegregation after homogenization and quenching was analyzed through different initial conditions obtained from calculations of the concentration profiles in the primary γ dendritic microstructure during solidification and the homogenization heat treatment. While the global sequence of precipitation remains qualitatively the same, substantial differences in the final volume fraction of γ' precipitates were predicted between the core and the periphery of a former dendrite arm, for typical homogenization and aging conditions. To demonstrate the relevance of the developed simulation approach, the model was also used to investigate modified precipitation heat treatments. The simulations showed that relatively short heat treatments based on slow continuous cooling could potentially replace the extended isothermal heat treatments which are commonly used. Slow continuous cooling conditions can lead to similar γ' precipitates radii and volume fractions, the main differences with isothermal heat treatments lying in a narrower particle size distribution.

  4. Study of the effects of gaseous environmental on the hot corrosion of superalloy materials

    NASA Technical Reports Server (NTRS)

    Smeggil, J. G.

    1981-01-01

    Studies have been conducted to examine the effect of low concentrations of NaCl(g) on the high temperature oxidation behavior of complex superalloys and potential coating formulations modified by silicon and reactive element (i.e., yttrium and hafnium) additions. Depending on alloy composition, a variety of effects were thermogravimetrically produced. Aluminum free alloys such as MAR-M509 and Hastelloy X with molybdenum and tungsten in solid solution showed accelerated (or breakaway) kinetics similar to that observed for Ni-Cr alloys. For IN-792, an alloy high in chromium and low in aluminum, molybdenum and tungsten present in solid solution does not adversely affect oxidation kinetics in the presence of NaCl(g). On the other hand, nickel-base alloys high in aluminum and molybdenum are catastrophically attacked by NaCl-bearing atmospheres. Silicon additions were, in general, observed to slightly improve the oxidation resistance of Ni, Ni-40Cr and CoCrAlY compositions in NaCl(g)-bearing atmospheres. To the degree that processes responsible for Al2O3 whisker formation deleteriously affect protective scale adherence, the addition of yttrium or hafnium can inhibit such whisker growth.

  5. Properties and microstructures for dual alloy combinations of three superalloys with alloy 901

    NASA Technical Reports Server (NTRS)

    Harf, F. H.

    1985-01-01

    Dual alloy combinations have potential for use in aircraft engine components such as turbine disks where a wide range of stress and temperature regimes exists during operation. Such alloy combinations may directly result in the conservation of elements which are costly or not available domestically. Preferably, a uniform heat treatment yielding good properties for both alloys should be used. Dual alloy combinations of iron rich Alloy 901 with nickel base superalloys Rene 95, Astroloy, or MERL 76 were not isostatically pressed from prealloyed powders. Individual alloys, alloy mixtures, and layered alloy combinations were given the heat treatments specified for their use in turbine disks or appropriate for Alloy 901. Selected specimens were overaged for 1500 hr at 650 C. Metallographic examinations revealed the absence of phases not originally present in either alloy of a combination. Mechanical tests showed adequate properties in combinations of Rene 95 or Astroloy with Alloy 901 when given the Alloy 901 heat treatment. Combinations with MERL 76 had better properties when given the MERL 76 heat treatment. The results indicate that these combinations are promising candidates for use in turbine disks.

  6. Secondary arm coarsening and microsegregation in superalloy PWA-1480 single crystals: Effect of low gravity

    NASA Technical Reports Server (NTRS)

    Vijayakumar, M.; Tewari, S. N.; Lee, J. E.; Curreri, P. A.

    1990-01-01

    Single crystal specimens of nickel base superalloy PWA-1480 were directionally solidified on ground and during low gravity (20 sec) and high gravity (90 sec) parabolic maneuver of KC-135 aircraft. Thermal profiles were measured during solidification by two in-situ thermocouples positioned along the sample length. The samples were quenched during either high or low gravity cycles so as to freeze the structures of the mushy zone developing under different gravity levels. Microsegregation was measured by examining the solutal profiles on several transverse cross-sections across primary dendrites along their length in the quenched mushy zone. Effect of gravity level on secondary arm coarsening kinetics and microsegregation have been investigated. The results indicate that there is no appreciable difference in the microsegregation and coarsening kinetics behavior in the specimens grown under high or low gravity. This suggests that short duration changes in gravity/levels (0.02 to 1.7 g) do not influence convection in the interdendritic region. Examination of the role of natural convection, in the melt near the primary dendrite tips, on secondary arm spacings requires low gravity periods longer than presently available on KC-135. Secondary arm coarsening kinetics show a reasonable fit with the predictions from a simple analytical model proposed by Kirkwood for a binary alloy.

  7. Numerical Simulation of Solidification, Homogenization, and Precipitation in an Industrial Ni-Based Superalloy

    NASA Astrophysics Data System (ADS)

    Rougier, Luc; Jacot, Alain; Gandin, Charles-André; Ponsen, Damien; Jaquet, Virginie

    2016-08-01

    A comprehensive simulation approach integrating solidification, homogenization, and precipitation during aging has been used to predict the formation of γ/γ' microstructures in the AM1 nickel-based superalloy. The particle size distribution of intradendritic γ' precipitates after aging was calculated with a multicomponent diffusion model coupled with CALPHAD thermodynamics for the equilibrium at the interface. The influence of residual microsegregation after homogenization and quenching was analyzed through different initial conditions obtained from calculations of the concentration profiles in the primary γ dendritic microstructure during solidification and the homogenization heat treatment. While the global sequence of precipitation remains qualitatively the same, substantial differences in the final volume fraction of γ' precipitates were predicted between the core and the periphery of a former dendrite arm, for typical homogenization and aging conditions. To demonstrate the relevance of the developed simulation approach, the model was also used to investigate modified precipitation heat treatments. The simulations showed that relatively short heat treatments based on slow continuous cooling could potentially replace the extended isothermal heat treatments which are commonly used. Slow continuous cooling conditions can lead to similar γ' precipitates radii and volume fractions, the main differences with isothermal heat treatments lying in a narrower particle size distribution.

  8. Effect of small amounts of nitrogen on properties of a Ni-based superalloy

    SciTech Connect

    Huang, X.; Zhang, Y.; Hu, Z.

    1999-07-01

    The microstructural, tensile, and stress-rupture lives of conventionally and directionally solidified (DS) cast specimens of a nickel-based superalloy have been investigated using materials of normal commercial composition and two melts with additions of 22 and 30 ppm nitrogen. It was found that the ductility, tensile life, and stress-rupture life of the conventional castings dramatically decreased with the increase of nitrogen content, but, in the longitudinal direction of DS samples, these properties were independent of nitrogen within the contents studied. The transverse tensile rupture life of DS castings had no significant change with nitrogen, except for some decrease in elongation of the sample containing 30 ppm N. The stress-rupture life and elongation in the transverse direction of the DS samples were improved at the 22 ppm nitrogen level, which might be attributed to the dendrite refining. Increasing the nitrogen content resulted in a change in carbide morphology from that of a Chinese script to a blocky form and a change in microporosity formation, especially in the conventional castings. The increased nitrogen content resulted in a significant reduction in the volume fraction of eutectic microconstituents and the in dendrite refinement in DS samples, but nitrogen content did not affect the morphology of {gamma}{prime} precipitates in the heat-treated alloys.

  9. Oxidation corrosion resistant superalloys and coatings

    NASA Technical Reports Server (NTRS)

    Jackson, Melvin R. (Inventor); Rairden, III, John R. (Inventor)

    1980-01-01

    An article of manufacture having improved high temperature oxidation and corrosion resistance comprising: (a) a superalloy substrate containing a carbide reinforcing phase, and (b) a coating consisting of chromium, aluminum, carbon, at least one element selected from iron, cobalt or nickel, and optionally an element selected from yttrium or the rare earth elements.

  10. Oxidation corrosion resistant superalloys and coatings

    NASA Technical Reports Server (NTRS)

    Jackson, Melvin R. (Inventor); Rairden, III, John R. (Inventor)

    1978-01-01

    An article of manufacture having improved high temperature oxidation and corrosion resistance comprising: (a) a superalloy substrate containing a carbide reinforcing phase, and (b) a coating consisting of chromium, aluminum, carbon, at least one element selected from iron, cobalt or nickel, and optionally an element selected from yttrium or the rare earth elements.

  11. Application of superalloy powder metallurgy for aircraft engines

    NASA Technical Reports Server (NTRS)

    Dreshfield, R. L.; Miner, R. V., Jr.

    1980-01-01

    In the last decade, Government/Industry programs have advanced powder metallurgy-near-net-shape technology to permit the use of hot isostatic pressed (HIP) turbine disks in the commercial aircraft fleet. These disks offer a 30% savings of input weight and an 8% savings in cost compared in cast-and-wrought disks. Similar savings were demonstrated for other rotating engine components. A compressor rotor fabricated from hot-die-forged-HIP superalloy billets revealed input weight savings of 54% and cost savings of 35% compared to cast-and-wrought parts. Engine components can be produced from compositions such as Rene 95 and Astroloy by conventional casting and forging, by forging of HIP powder billets, or by direct consolidation of powder by HIP. However, each process produces differences in microstructure or introduces different defects in the parts. As a result, their mechanical properties are not necessarily identical. Acceptance methods should be developed which recognize and account for the differences.

  12. The corrosion performance of nickel-based alloys in a reverse osmosis plant utilizing seawater

    SciTech Connect

    Al-Hashem, A.; Carew, J.; Al-Odwani, A.

    1998-12-31

    Four nickel-based alloys, UNS N06625, UNS N08825, UNS N10276, and UNS N05500, were evaluated in terms of their corrosion performance in a seawater reverse osmosis plant using the electrochemical impedance spectroscopy (EIS), open circuit potential (OCP) and linear polarization resistance (LPR) measurements. Slight changes in the EIS spectra were observed for UNS N06625, UNSN10276 and UNS N05500 at low frequencies. However, UNS N08825 EIS spectra exhibited more changes than the other alloys at low frequencies. The OCP of UNS N10276 was more noble than the other alloys under the same conditions. The LPR measurements indicated that UNS N10276 and UNS N05500 exhibited lower corrosion rates than UNS NO6625 and UNS N08825.

  13. Dual Microstructure Heat Treatment of a Nickel-Base Disk Alloy

    NASA Technical Reports Server (NTRS)

    Gayda, John

    2001-01-01

    Existing Dual Microstructure Heat Treat (DMHT) technology was successfully applied to Alloy 10, a high strength, nickel-base disk alloy, to produce a disk with a fine grain bore and coarse grain rim. Specimens were extracted from the DMHT disk and tested in tension, creep, fatigue, and crack growth using conditions pertinent to disk applications. These data were then compared with data from "traditional" subsolvus and supersolvus heat treatments for Alloy 10. The results showed the DMHT disk to have a high strength, fatigue resistant bore comparable to that of subsolvus Alloy 10. Further, creep resistance of the DMHT rim was comparable to that of supersolvus Alloy 10. Crack growth resistance in the DMHT rim, while better than that for subsolvus, was inferior to that of supersolvus Alloy 10. The slow cool at the end of the DMHT conversion and/or the subsolvus resolution step are thought to be responsible for degrading rim DMHT crack growth resistance.

  14. Analysis of Nickel Based Hardfacing Materials Manufactured by Laser Cladding for Sodium Fast Reactor

    NASA Astrophysics Data System (ADS)

    Aubry, P.; Blanc, C.; Demirci, I.; Dal, M.; Malot, T.; Maskrot, H.

    For improving the operational capacity, the maintenance and the decommissioning of the future French Sodium Fast Reactor ASTRID which is under study, it is asked to find or develop a cobalt free hardfacing alloy and the associated manufacturing process that will give satisfying wear performances. This article presents recent results obtained on some selected nickel-based hardfacing alloys manufactured by laser cladding, particularly on Tribaloy 700 alloy. A process parameter search is made and associated the microstructural analysis of the resulting clads. A particular attention is made on the solidification of the main precipitates (chromium carbides, boron carbides, Laves phases,…) that will mainly contribute to the wear properties of the material. Finally, the wear resistance of some samples is evaluated in simple wear conditions evidencing promising results on tribology behavior of Tribaloy 700.

  15. Ignition characteristics of the nickel-based alloy UNS N07718 in pressurized oxygen

    NASA Technical Reports Server (NTRS)

    Bransford, James W.; Billiard, Phillip A.; Hurley, James A.; Mcdermott, Kathleen M.; Vazquez, Isaura

    1989-01-01

    The development of ignition and combustion in pressurized oxygen atmospheres was studied for the nickel based alloy UNS N07718. Ignition of the alloy was achieved by heating the top. It was found that the alloy would autoheat to destruction from temperatures below the solidus temperature. In addition, endothermic events occurred as the alloy was heated, many at reproducible temperatures. Many endothermic events occurred prior to abrupt increases in surface temperature and appeared to accelerate the rate of increase in specimen temperature. It appeared that the source of some endotherms may increase the oxidation rate of the alloy. Ignition parameters are defined and the temperatures at which these parameters occur are given for the oxygen pressure range of 1.72 to 13.8 MPa (250 to 2000 psia).

  16. Assessment of special stainless steels and nickel-base alloys for use under offshore conditions

    SciTech Connect

    Jasner, M.R.; Herda, W.R.

    1994-12-31

    Major offshore installations are designed for a 25-years` life span and more. To predict the corrosion behavior of various alloys for such a long period results from accelerated laboratory tests have to be verified by suitable field tests. The results from laboratory tests and exposure to natural seawater show that nickel-based alloys such as alloy 59 (UNS N06059) and alloy 31 (UNS N08031) can be employed to most severe conditions. For general applications 6Mo stainless steels with 25% Ni such as alloy 926 (UNS N08926) may be used. If higher strength is required alloy 24 (18 Ni-24.5 Cr-6.2 Mn-4.3 Mo-0.6 Cu-0.45 Mn) is the preferred material.

  17. Comparison of joining processes for Haynes 230 nickel based super alloy

    NASA Astrophysics Data System (ADS)

    Williston, David Hugh

    Haynes 230 is a nickel based, solid-solution strengthened alloy that is used for high-temperature applications in the aero-engine and power generation industries. The alloy composition is balanced to avoid precipitation of undesirable topologically closed-packed (TCP) intermetallic phases, such as Sigma, Mu, or Laves-type, that are detrimental to mechanical and corrosion properties. This material is currently being used for the NASA's J2X upper stage rocket nozzle extension. Current fabrication procedures use fusion welding processes to join blanks that are subsequently formed. Cracks have been noted to occur in the fusion welded region during the forming operations. Use of solid state joining processes, such as friction stir welding are being proposed to eliminate the fusion weld cracks. Of interest is a modified friction stir welding process called thermal stir welding. Three welding process: Gas Metal Arc Welding (GMAW), Electron Beam Welding (EBW), and Thermal Stir Welding (TSWing) are compared in this study.

  18. Effects of Rhenium Addition on the Temporal Evolution of the Nanostructure and Chemistry of a Model Ni-Cr-Al Superalloy. 1; Experimental Observations

    NASA Technical Reports Server (NTRS)

    Yoon, Kevin E.; Noebe, Ronald D.; Seidman, David N.

    2006-01-01

    The temporal evolution of the nanostructure and chemistry of a model Ni-8.5 at.% Cr-10 at. % Al alloy, with the addition of 2 at.% Re, aged at 1073 K from 0.25 to 264 h, was studied. Transmission electron microscopy and atom-probe tomography were used to measure the number density and mean radius of the gamma prime (L1(sub 2) structure)-precipitates and the chemistry of the gamma prime-precipitates and the gamma (face-centered cubic)-matrix, including the partitioning behavior of all alloying elements between the gamma- and gamma prime-phases and the segregation behavior at gamma/gamma prime interfaces. The precipitates remained spheroidal for an aging time of up to 264 h and, unlike commercial nickel-based superalloys containing Re, there was not confined (nonmonotonic) Re segregation at the gamma/gamma prime interfaces.

  19. Physics-based simulation modeling and optimization of microstructural changes induced by machining and selective laser melting processes in titanium and nickel based alloys

    NASA Astrophysics Data System (ADS)

    Arisoy, Yigit Muzaffer

    Manufacturing processes may significantly affect the quality of resultant surfaces and structural integrity of the metal end products. Controlling manufacturing process induced changes to the product's surface integrity may improve the fatigue life and overall reliability of the end product. The goal of this study is to model the phenomena that result in microstructural alterations and improve the surface integrity of the manufactured parts by utilizing physics-based process simulations and other computational methods. Two different (both conventional and advanced) manufacturing processes; i.e. machining of Titanium and Nickel-based alloys and selective laser melting of Nickel-based powder alloys are studied. 3D Finite Element (FE) process simulations are developed and experimental data that validates these process simulation models are generated to compare against predictions. Computational process modeling and optimization have been performed for machining induced microstructure that includes; i) predicting recrystallization and grain size using FE simulations and the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model, ii) predicting microhardness using non-linear regression models and the Random Forests method, and iii) multi-objective machining optimization for minimizing microstructural changes. Experimental analysis and computational process modeling of selective laser melting have been also conducted including; i) microstructural analysis of grain sizes and growth directions using SEM imaging and machine learning algorithms, ii) analysis of thermal imaging for spattering, heating/cooling rates and meltpool size, iii) predicting thermal field, meltpool size, and growth directions via thermal gradients using 3D FE simulations, iv) predicting localized solidification using the Phase Field method. These computational process models and predictive models, once utilized by industry to optimize process parameters, have the ultimate potential to improve performance of

  20. Separating the Influence of Environment from Stress Relaxation Effects on Dwell Fatigue Crack Growth in a Nickel-Base Disk Alloy

    NASA Technical Reports Server (NTRS)

    Telesman, J.; Gabb, T. P.; Ghosn, L. J.

    2016-01-01

    Both environmental embrittlement and crack tip visco-plastic stress relaxation play a significant role in determining the dwell fatigue crack growth (DFCG) resistance of nickel-based disk superalloys. In the current study performed on the Low Solvus High Refractory (LSHR) disk alloy, the influence of these two mechanisms were separated so that the effects of each could be quantified and modeled. Seven different microstructural variations of LSHR were produced by controlling the cooling rate and the subsequent aging and thermal exposure heat treatments. Through cyclic fatigue crack growth testing performed both in air and vacuum, it was established that four out of the seven LSHR heat treatments evaluated, possessed similar intrinsic environmental resistance to cyclic crack growth. For these four heat treatments, it was further shown that the large differences in dwell crack growth behavior which still persisted, were related to their measured stress relaxation behavior. The apparent differences in their dwell crack growth resistance were attributed to the inability of the standard linear elastic fracture mechanics (LEFM) stress intensity parameter to account for visco-plastic behavior. Crack tip stress relaxation controls the magnitude of the remaining local tensile stresses which are directly related to the measured dwell crack growth rates. It was hypothesized that the environmentally weakened grain boundary crack tip regions fail during the dwells when their strength is exceeded by the remaining local crack tip tensile stresses. It was shown that the classical creep crack growth mechanisms such as grain boundary sliding did not contribute to crack growth, but the local visco-plastic behavior still plays a very significant role by determining the crack tip tensile stress field which controls the dwell crack growth behavior. To account for the influence of the visco-plastic behavior on the crack tip stress field, an empirical modification to the LEFM stress

  1. Progress in Synthesis of Highly Active and Stable Nickel-Based Catalysts for Carbon Dioxide Reforming of Methane.

    PubMed

    Kawi, Sibudjing; Kathiraser, Yasotha; Ni, Jun; Oemar, Usman; Li, Ziwei; Saw, Eng Toon

    2015-11-01

    In recent decades, rising anthropogenic greenhouse gas emissions (mainly CO2 and CH4 ) have increased alarm due to escalating effects of global warming. The dry carbon dioxide reforming of methane (DRM) reaction is a sustainable way to utilize these notorious greenhouse gases. This paper presents a review of recent progress in the development of nickel-based catalysts for the DRM reaction. The enviable low cost and wide availability of nickel compared with noble metals is the main reason for persistent research efforts in optimizing the synthesis of nickel-based catalysts. Important catalyst features for the rational design of a coke-resistant nickel-based nanocatalyst for the DRM reaction are also discussed. In addition, several innovative developments based on salient features for the stabilization of nickel nanocatalysts through various means (which include functionalization with precursors, synthesis by plasma treatment, stabilization/confinement on mesoporous/microporous/carbon supports, and the formation of metal oxides) are highlighted. The final part of this review covers major issues and proposed improvement strategies pertaining to the rational design of nickel-based catalysts with high activity and stability for the DRM reaction.

  2. Progress in Synthesis of Highly Active and Stable Nickel-Based Catalysts for Carbon Dioxide Reforming of Methane.

    PubMed

    Kawi, Sibudjing; Kathiraser, Yasotha; Ni, Jun; Oemar, Usman; Li, Ziwei; Saw, Eng Toon

    2015-11-01

    In recent decades, rising anthropogenic greenhouse gas emissions (mainly CO2 and CH4 ) have increased alarm due to escalating effects of global warming. The dry carbon dioxide reforming of methane (DRM) reaction is a sustainable way to utilize these notorious greenhouse gases. This paper presents a review of recent progress in the development of nickel-based catalysts for the DRM reaction. The enviable low cost and wide availability of nickel compared with noble metals is the main reason for persistent research efforts in optimizing the synthesis of nickel-based catalysts. Important catalyst features for the rational design of a coke-resistant nickel-based nanocatalyst for the DRM reaction are also discussed. In addition, several innovative developments based on salient features for the stabilization of nickel nanocatalysts through various means (which include functionalization with precursors, synthesis by plasma treatment, stabilization/confinement on mesoporous/microporous/carbon supports, and the formation of metal oxides) are highlighted. The final part of this review covers major issues and proposed improvement strategies pertaining to the rational design of nickel-based catalysts with high activity and stability for the DRM reaction. PMID:26440576

  3. Design overview of fiber-reinforced superalloy composites for the Space Shuttle main engine

    NASA Technical Reports Server (NTRS)

    Lewis, J. R.

    1985-01-01

    This preliminary design study evaluated the potential of fiber-reinforced superalloys (FRS) for hot-section components of Space Shuttle Main Engine turbopumps. Emphasis was placed on uncooled turbine blades, with a more limited evaluation of FRS turbine stator vanes. The study included FRS properties evaluation, current structural design capability, and preliminary design and structural analysis. In addition, key technology needs were identified, and a plan was generated to develop operational hardware for advanced versions of the SSME. Based on projections of design properties for FRS composites comprising 50 volume percent of W-4Re-0.38Hf-0.02C wire filaments in a ductile superalloy matrix, it was concluded that FRS turbine blades offer the potential of significant improved operating life and higher temperature capability over the MAR-M-246(Hf) (DS) blades currently used in the SSME.

  4. Creep and fatigue research efforts on advanced materials

    NASA Technical Reports Server (NTRS)

    Gayda, John

    1987-01-01

    Two of the more important materials problems encountered in turbine blades of aircraft engines are creep and fatigue. To withstand these high-temperature phenomena modern engines utilize single-crystal, nickel-based superalloys as the material of choice in critical applications. Recent research activities at Lewis on single-crystal blading material as well as future research initiatives on metal matrix composites related to creep and fatigue are discussed. The goal of these research efforts is improving the understanding of microstructure-property relationships and thereby guide material development.

  5. Creep and fatigue research efforts on advanced materials

    NASA Technical Reports Server (NTRS)

    Gayda, John

    1990-01-01

    Two of the more important materials problems encountered in turbine blades of aircraft engines are creep and fatigue. To withstand these high-temperature phenomena, modern engines utilize single-crystal, nickel-base superalloys as the material of choice in critical applications. This paper will present recent research activities at NASA's Lewis Research Center on single-crystal blading material, related to creep and fatique. The goal of these research efforts is to improve the understanding of microstructure-property relationships and thereby guide material development.

  6. Optimizing Scale Adhesion on Single Crystal Superalloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Pint, Bruce A.

    2000-01-01

    To improve scale adhesion, single crystal superalloys have been desulfurized to levels below 1 ppmw by hydrogen annealing. A transition to fully adherent behavior has been shown to occur at a sulfur level of about 0.2 ppmw, as demonstrated for PWA 1480, PWA 1484, and Rene N5 single crystal superalloys in 1100-1150 C cyclic oxidation tests up to 2000 h. Small additions of yttrium (15 ppmw) also have been effective in producing adhesion for sulfur contents of about 5 ppmw. Thus the critical Y/S ratio required for adhesion was on the order of 3-to-1 by weight (1-to-1 atomic), in agreement with values estimated from solubility products for yttrium sulfides. While hydrogen annealing greatly improved an undoped alloy, yielding <= 0.01 ppmw S, it also produced benefits for Y-doped alloys without measurably reducing the sulfur content.

  7. Characterizing solute-lean defects in superalloys

    NASA Astrophysics Data System (ADS)

    Samuelsson, E.; Domingue, J. A.; Maurer, G. E.

    1990-08-01

    Solute-lean defects, commonly called white spots, are frequently found in superalloys. These defects limit the service life of components made from superalloys, and alloy producers have devoted intense study to their characterization and elimination. Recent work shows that solute lean defects can be classified as "discrete," "diffuse" and "mini," and can be further classified into "clean" and "dirty" white spots. More than one formation mechanism for white spots is exemplified by the chemical and morphological differences between discrete, diffuse and mini white spots. White spot detection depends on the thermomechanically developed precipitation of hardening phases, coupled with specific etches that preferentially react to microstructure differences. The white spot defect is indigenous to the vacuum arc remelting process, but defect formation can be minimized by careful process control.

  8. Oxidation of Superalloys in Extreme Environments

    SciTech Connect

    Pint, Bruce A; Dryepondt, Sebastien N; Unocic, Kinga A

    2010-01-01

    Superalloys like 718 and its derivatives primarily rely on the formation of an external Cr-rich oxide layer or scale for environmental protection at high temperatures. Operating conditions where environmental resistance is more of a concern generally involve higher temperatures or more corrosive environments, especially where S is present, usually due to fuel impurities. With clean fuels, the presence of water vapor and oxygen, such as a combustion environment in a natural gas-fired turbine, chromia forms a volatile oxy-hydroxide leading to accelerated Cr loss. In laboratory experiments, mass losses are measured due to this volatilization. For sulfidizing or hot corrosion environments, the role of alloy and coating composition on corrosion resistance will be reviewed. An increasing area of interest is the interaction between environmental degradation and the stress-induced deformation of the superalloy including the influence of oxidation-resistant coatings on mechanical properties. Strategies to study this interaction will be discussed.

  9. Maraging superalloys and heat treatment processes

    DOEpatents

    Korenko, Michael K.; Gelles, David S.; Thomas, Larry E.

    1986-01-01

    Described herein are nickel-chromium-iron maraging, gamma prime strengthened superalloys containing about 18 to 25 weight percent nickel, about 4 to 8 weight percent chromium, gamma prime forming elements such as aluminum and/or titanium, and a solid solution strengthening element, such as molybdenum. After heat treatment, which includes at least one ausaging treatment and at least one maraging treatment, a microstructure containing gamma prime phase and decomposed Fe-Ni-Cr type martensite is produced.

  10. Dual Microstructure Heat Treatment of a Nickel-Base Disk Alloy Assessed

    NASA Technical Reports Server (NTRS)

    Gayda, John

    2002-01-01

    Gas turbine engines for future subsonic aircraft will require nickel-base disk alloys that can be used at temperatures in excess of 1300 F. Smaller turbine engines, with higher rotational speeds, also require disk alloys with high strength. To address these challenges, NASA funded a series of disk programs in the 1990's. Under these initiatives, Honeywell and Allison focused their attention on Alloy 10, a high-strength, nickel-base disk alloy developed by Honeywell for application in the small turbine engines used in regional jet aircraft. Since tensile, creep, and fatigue properties are strongly influenced by alloy grain size, the effect of heat treatment on grain size and the attendant properties were studied in detail. It was observed that a fine grain microstructure offered the best tensile and fatigue properties, whereas a coarse grain microstructure offered the best creep resistance at high temperatures. Therefore, a disk with a dual microstructure, consisting of a fine-grained bore and a coarse-grained rim, should have a high potential for optimal performance. Under NASA's Ultra-Safe Propulsion Project and Ultra-Efficient Engine Technology (UEET) Program, a disk program was initiated at the NASA Glenn Research Center to assess the feasibility of using Alloy 10 to produce a dual-microstructure disk. The objectives of this program were twofold. First, existing dual-microstructure heat treatment (DMHT) technology would be applied and refined as necessary for Alloy 10 to yield the desired grain structure in full-scale forgings appropriate for use in regional gas turbine engines. Second, key mechanical properties from the bore and rim of a DMHT Alloy 10 disk would be measured and compared with conventional heat treatments to assess the benefits of DMHT technology. At Wyman Gordon and Honeywell, an active-cooling DMHT process was used to convert four full-scale Alloy 10 disks to a dual-grain microstructure. The resulting microstructures are illustrated in the

  11. Barrier Coatings for Refractory Metals and Superalloys

    SciTech Connect

    SM Sabol; BT Randall; JD Edington; CJ Larkin; BJ Close

    2006-02-23

    In the closed working fluid loop of the proposed Prometheus space nuclear power plant (SNPP), there is the potential for reaction of core and plant structural materials with gas phase impurities and gas phase transport of interstitial elements between superalloy and refractory metal alloy components during service. Primary concerns are surface oxidation, interstitial embrittlement of refractory metals and decarburization of superalloys. In parallel with kinetic investigations, this letter evaluates the ability of potential coatings to prevent or impede communication between reactor and plant components. Key coating requirements are identified and current technology coating materials are reviewed relative to these requirements. Candidate coatings are identified for future evaluation based on current knowledge of design parameters and anticipated environment. Coatings were identified for superalloys and refractory metals to provide diffusion barriers to interstitial transport and act as reactive barriers to potential oxidation. Due to their high stability at low oxygen potential, alumina formers are most promising for oxidation protection given the anticipated coolant gas chemistry. A sublayer of iridium is recommended to provide inherent diffusion resistance to interstitials. Based on specific base metal selection, a thin film substrate--coating interdiffusion barrier layer may be necessary to meet mission life.

  12. Numerical Simulation of Transport Phenomena for a Double-Layer Laser Powder Deposition of Single-Crystal Superalloy

    NASA Astrophysics Data System (ADS)

    Liu, Zhaoyang; Qi, Huan

    2014-04-01

    A turbine blade made of single-crystal superalloys has been commonly used in gas turbine and aero engines. As an effective repair technology, laser powder deposition has been implemented to restore the worn turbine blade tips with a near-net shape capability and highly controllable solidified microstructure. Successful blade repair technology for single-crystal alloys requires a continuous epitaxial grain growth in the same direction of the crystalline orientation of the substrate material to the newly deposited layers. This work presents a three-dimensional numerical model to simulate the transport phenomena for a multilayer coaxial laser powder deposition process. Nickel-based single-crystal superalloy Rene N5 powder is deposited on a directional solidified substrate made of nickel-based directional-solidified alloy GTD 111 to verify the simulation results. The effects of processing parameters including laser power, scanning speed, and powder feeding rate on the resultant temperature field, fluid velocity field, molten pool geometric sizes, and the successive layer remelting ratios are studied. Numerical simulation results show that the maximum temperature of molten pool increases over layers due to the reduced heat dissipation capacity of the deposited geometry, which results in an increased molten pool size and fluid flow velocity at the successive deposited layer. The deposited bead geometry agrees well between the simulation and the experimental results. A large part of the first deposition layer, up to 85 pct of bead height, can be remelted during the deposition of the second layer. The increase of scanning speed decreases the ratio of G/ V (temperature gradient/solidification velocity), leading to an increased height ratio of the misoriented grain near the top surface of the previous deposited layer. It is shown that the processing parameters used in the simulation and experiment can produce a remelting ratio R larger than the misoriented grain height ratio

  13. 76 FR 8773 - Superalloy Degassed Chromium From Japan

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-15

    ... applicable deadline.'' (75 FR 80457). Accordingly, pursuant to section 751(c) of the Tariff Act of 1930 (19 U... COMMISSION Superalloy Degassed Chromium From Japan AGENCY: United States International Trade Commission... 2010 to determine whether revocation of the antidumping duty order on superalloy degassed chromium...

  14. Investigations of White Layer Formation During Machining of Powder Metallurgical Ni-Based ME 16 Superalloy

    NASA Astrophysics Data System (ADS)

    Veldhuis, S. C.; Dosbaeva, G. K.; Elfizy, A.; Fox-Rabinovich, G. S.; Wagg, T.

    2010-10-01

    Surface integrity of machined parts made from the advanced Ni-based superalloys is important for modern manufacturing in the aerospace industry. Metallographic observations of the ME 16 alloy microstructure were made using optical metallography and a high-resolution scanning electron microscope with energy dispersive x-ray spectrometer (HR SEM/EDS). Tool life of cemented carbide inserts with TiAlN coating during machining (finishing turning operation) of ME 16 superalloy has been studied and wear patterns of the cutting tools were identified. Surface integrity of the machined part after completion of the turning operation was investigated. The morphology of machined parts has been examined and cross-sections of the machined surfaces have been analyzed. The formation of white layer on the surface of the machined part was studied for varied machining conditions. It was found that a 2-4 µm thick white layer forms during turning of the ME 16 superalloy. This layer was investigated using EDS and XRD. The studies show that the white layer is an oxygen-containing layer with a high amount of aluminum, enriched by chromium and tungsten. Under specific cutting conditions, the structure of white layer transforms into a γ-alumina. Formation of this thermal barrier ceramic white layer on the surface of the machined part negatively affects its surface integrity and cutting tool life.

  15. Ignition characteristics of the nickel-based alloy UNS N07001 in pressurized oxygen

    NASA Technical Reports Server (NTRS)

    Bransford, J. W.; Billiard, P. A.

    1990-01-01

    The development of ignition and combustion in pressurized oxygen atmospheres was studied for the nickel-based alloy UNS N07001. Ignition of the alloy was achieved by heating the top surface of a cylindrical specimen with a continuous-wave CO2 laser. Two heating procedures were used. In the first, laser power was adjusted to maintain an approximately linear increase in surface temperature. In the second, laser power was periodically increased until autoheating (self-heating) was established. It was found that the alloy would autoheat to combustion from temperatures below the solidus temperature. In addition, the alloy had a tendency to develop combustion zones (hot spots) at high oxygen pressures when the incremental (step) heating test mode was used. Unique points on the temperature-time curves that describe certain events are defined and the temperatures at which these events occur are given for the oxygen pressure range of 1.72 to 13.8 MPa (250 to 2000 psia).

  16. Infrared repair brazing of 403 stainless steel with a nickel-based braze alloy

    NASA Astrophysics Data System (ADS)

    Shiue, R. K.; Wu, S. K.; Hung, C. M.

    2002-06-01

    Martensitic stainless steel (403SS) is extensively used for intermediate and low-pressure steam turbine blades in fossil-fuel power plants. The purpose of this investigation is to study the repair of shallow cracks on the surface of 403SS steam turbine blades by infrared repair brazing using rapid thermal cycles. A nickel-based braze alloy (NICROBRAZ LM) is used as filler metal. The braze alloy after brazing is primarily comprised of borides and an FeNi3 matrix with different amounts of alloying elements, especially B and Si. As the brazing temperature increases, more Fe atoms are dissolved into the molten braze. Some boron atoms diffuse into the 403SS substrate primarily via grain boundary diffusion and form B-Cr-Fe intermetallic precipitates along the grain boundaries. The LM filler metal demonstrates better performance than 403SS in both microhardness and wear tests. It is also noted that specimens brazed in a vacuum have less porosity than those brazed in an Ar atmosphere. The shear strength of the joint is around 300 MPa except for specimens brazed in short time periods, e.g., 5 seconds in Ar flow and 30 seconds in vacuum. The fractographs mainly consist of brittle fractures and no ductile dimple fractures observed in the scanning electron microscope (SEM) examination.

  17. Spectrophotometric studies and applications for the determination of yttrium in pure and in nickel base alloys.

    PubMed

    Amin, A S; Mohammed, T Y; Mousa, A A

    2003-09-01

    Yttrium reacts with 5-(4'-chlorophenylazo)-6-hydroxypyrimidine-2,4-dione (I), 5-(2'-bromophenylazo)-6-hydroxypyrimidine-2,4-dione (II), 5-(2',4'-dimethylphenylazo)-6-hydroxypyrimidine-2,4-dione (III), 5-(4'-nitro-2',6'-dichlorophenylazo)-6-hydroxypyrimidine-2,4-dione (IV), 5-(2'-methyl-4'-hydroxyphenylazo)-6-hydroxypyrimidine-2,4-dione (V) to form a dark pink complexes, having an absorption maximum at 610, 577, 596, 567 and 585 nm, respectively. The complex formation was completed spontaneously in theil buffer solution and the resulting complex was stable for at least 3 h after dilution. Under the optimum conditions employed, the molar absorptivities were found to be 1.60 x 10(4), 1.29 x 10(4), 1.96 x 10(4), 1.45 x 10(4) and 1.21 x 10(4) l mol(-1) cm(-1) and the molar ratios were (1:1) and (1:2) (M:L). The linear ranges were found within 95 microg of yttrium in 25 ml solution. One of the characteristics of the complex was its high tolerance for calcium and hence a method of separation and enrichment of microamounts of yttrium by using calcium oxalate precipitate was developed and applied to measure yttrium in nickel-base alloys. Interfering species and their elimination have been studied. The precision and recovery are both satisfactory.

  18. Microstructure and mechanical properties of hip-consolidated Rene 95 powders. [hot-isostatic pressed nickel-based powder metal

    NASA Technical Reports Server (NTRS)

    Shimanuki, Y.; Nishino, Y.; Masui, M.; Doi, H.

    1980-01-01

    The effects of heat-treatments on the microstructure of P/M Rene 95 (a nickel-based powder metal), consolidated by the hot-isostatic pressing (HIP), were examined. The microstructure of as-HIP'd specimen was characterized by highly serrated grain boundaries. Mechanical tests and microstructural observations reveal that the serrated grain boundaries improved ductility at both room and elevated temperatures by retarding crack propagation along grain boundaries.

  19. Fabrication of coatings and bulk products made of a nickel-based material by additive technology laser metal deposition

    NASA Astrophysics Data System (ADS)

    Gorunov, A. I.

    2016-01-01

    It is shown that products made of a nickel-based material can be formed by direct additive laser deposition. Ring samples with good antifriction properties are formed. The material after direct laser deposition is characterized by a heterogeneous structure: coarse inclusions with a high hardness are distributed in a softer matrix. Final laser treatment leads to the formation of a homogeneous microstructure and the refinement of second phases.

  20. Refractory metal superalloys: Design of yttrium aluminum garnet passivating niobium alloys

    NASA Astrophysics Data System (ADS)

    Bryan, David

    A systems-based approach, integrating computational modeling with experimental techniques to approach engineering problems in a time and cost efficient manner, was employed to design a Nb-based refractory superalloy for use at 1300°C. Ashby-type selection criteria for both thermodynamic and kinetic parameters were employed to identify a suitable protective oxide for Nb alloys. Yttrium aluminum garnet (YAG) was selected as the most promising candidate for its excellent combination of desirable properties. The alloy microstructural concept was based upon the gamma - gamma' nickel-based superalloys in which the multifunctional gamma' phase serves as both a creep strengthening dispersion and a source of reactive elements for oxide passivation. Candidate ternary Pd-Y-Al and Pt-Y-Al compounds were fabricated and characterized by XRD and DTA. Of the intermetallics studied, only PtYAl had a high enough melting point (1580°C) for use in an alloy operating at 1300°C. The alloy matrix design was based upon Wahl's extension of Wagner's criterion for protective oxidation, requiring a reduction of the product N ODO/DAl by 5 orders of magnitude relative to binary Nb-Al. A thermodynamic and kinetic analysis identified elements with large oxygen affinities as the most beneficial for reducing the magnitude of the quantity NOD O. Construction of a combined thermodynamic and mobility database identified increased Al solubility as the best approach for increasing D Al. Utilizing the thermodynamic and mobility databases, obtained from a combination of model alloys, oxidation experiments, and first principles calculations, theoretical designs predicted the large changes in solubility and transport parameters were achievable. Several prototype alloys were then fabricated and evaluated via oxidation tests at both 1300°C and 1100°C. YAG formation was demonstrated as part of multicomponent oxide scales in the alloys that exhibited the greatest reduction in oxidation rates. The oxidation