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Sample records for nickel-base heat-resistant alloys

  1. 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.

  2. 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.

  3. 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.

  4. Mechanically alloyed Ni-base alloys for heat-resistant applications

    SciTech Connect

    Wilson, R.K.; Fischer, J.J.

    1995-12-31

    INCONEL alloys MA 754 and MA 758 are nickel-base oxide dispersion-strengthened (ODS) alloys made by mechanical alloying (MA). Commercial use of Ma Ni-base alloys to date has been predominantly in aerospace applications of alloy MA 754 as turbine engine vanes. Both alloys are suitable for industrial heat treating components and other heat resistant alloy applications. Field trials and commercial experience in such applications of MA alloys are being gained while high temperature property characterization and new product form development continue. Hot isostatic pressing (HIP) is the standard consolidation method for billets from which large bar and plate are produced for industrial applications of MA. This paper describes production of standard mill shapes from HIP billets, and it presents information on current and potential uses of MA alloys in applications such as: skid rails for use in high temperature walking beam furnaces, heat treating furnace components, components for handling molten glass, and furnace tubes. The paper includes comparison of the properties obtained in alloy MA 754 (20% Cr) and alloy MA 758 (30% Cr).

  5. 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.

  6. Nitrogen-atomized, nickel-based, corrosion-resistant alloys

    NASA Astrophysics Data System (ADS)

    Rizzo, Frank J.

    1996-04-01

    Nitrogen gas atomization has been used for many years to produce iron-based powder-metal materials such as stainless and tool steels. However, it is more typical to use argon atomization with nickel-based alloys because it avoids the formation of nitrides that, in some cases, can be detrimental to the mechanical properties of these materials. In this article, two nickel-based materials— alloy 625 and alloy 690—normally used for applications where corrosion resistance is of primary importance were evaluated in their nitrogen-atomized powder metal form. Nitrogen atomization uncovered attributes of these nickel alloys that are not present in their conventionally produced counterparts or in argon-atomized versions of the same compositions.

  7. The metallography of a nickel base casting alloy.

    PubMed

    Lewis, A J

    1975-10-01

    Three groups of tensile test pieces were produced using a nickel base partial denture casting alloy and employing induction fusion in each case. The first group was produced fro new metal, the second from metal which had been recast four times, and the third from new overheated metal. Samples of alloy were cut from each group, and together with a piece from an original ingot, were mounted, polished, etched, and examined under a metallurgical microscope. PMID:1108851

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Pulsed-Current Welding Of Nickel-Based Alloy

    NASA Technical Reports Server (NTRS)

    Gamwell, W. R.; Kurgan, C.; Malone, T. W.

    1993-01-01

    Joints as strong (or stronger than) joints made with constant current. Report based on study of pulsed-current versus constant-current gas/tungsten arc welding of butt joints between panels of nickel-based alloy 718. In pulsed-current welding, arc current alternated between high and low value. Enables greater control of freezing and depth of penetration of weld puddle at given heat input. Thicker sections joined. Readily incorporated into automated welding system, with resultant greater uniformity and reproducibility of welds than attained in manual welding.

  18. 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.

  19. 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.

  20. Exploratory Investigation of Advanced-Temperature Nickel-Base Alloys

    NASA Technical Reports Server (NTRS)

    Freche, John C.; Waters, William J.

    1959-01-01

    An investigation was conducted to provide an advanced-temperature nickel-base alloy with properties suitable for aircraft turbine blades as well as for possible space vehicle applications. An entire series of alloys that do not require vacuum melting techniques and that generally provide good stress-rupture and impact properties was evolved. The basic-alloy composition of 79 percent nickel, 8 percent molybdenum, 6 percent chromium, 6 percent aluminum, and 1 percent zirconium was modified by a series of element additions such as carbon, titanium, and boron, with the nickel content adjusted to account for the additives. Stress-rupture, impact, and swage tests were made with all the alloys. The strongest composition (basic alloy plus 1.5 percent titanium plus 0.125 percent carbon) displayed 384- and 574-hour stress-rupture lives at 1800 F and 15,000 psi in the as-cast and homogenized conditions, respectively. All the alloys investigated demonstrated good impact resistance. Several could not be broken in a low-capacity Izod impact tester and, on this basis, all compared favorably with several high-strength high-temperature alloys. Swaging cracks were encountered with all the alloys. In several cases, however, these cracks were slight and could be detected only by zyglo examination. Some of these compositions may become amenable to hot working on further development. On the basis of the properties indicated, it appears that several of the alloys evolved, particularly the 1.5 percent titanium plus 0.125 percent carbon basic-alloy modification, could be used for advanced- temperature turbine blades, as well as for possible space vehicle applications.

  1. 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.

  2. 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

  3. 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.

  4. The effect of aluminium on the metallography of a nickel base removable partial denture casting alloy.

    PubMed

    Lewis, A J

    1978-12-01

    Three special nickel-chromium alloys were prepared in which the aluminum levels were adjusted both above and below that of a commercial nickel base dental casting alloy. Tensile and metallographic evaluation of representative samples of the alloys were made and the changes in the properties of the alloys are reported. PMID:285671

  5. High strength nickel-base alloy with improved oxidation resistance up to 2200 degrees F

    NASA Technical Reports Server (NTRS)

    Freche, J. C.; Waters, W. J.

    1968-01-01

    Modifying the chemistry of the NASA TAZ-8 alloy and utilizing vacuum melting techniques provides a high strength, workable nickel base superalloy with improved oxidation resistance for use up to 2200 degrees F.

  6. Microstructural characterization of dissimilar welds between alloy 800 and HP heat-resistant steel

    SciTech Connect

    Dehmolaei, R.; Shamanian, M. Kermanpur, A.

    2008-10-15

    In this study, dissimilar welds between HP heat-resistant steel and Incoloy 800 were made with four different filler materials including: 309 stainless steel and nickel-based Inconel 82, 182 and 617. The microstructure of the base metals, weld metals and their interfaces were characterized by utilizing optical and scanning electron microscopy. Grain boundaries migration in the weld metals was studied. It was found that the migration of grain boundaries in the Inconel 82 weld metal was very extensive. Precipitates of TiC and M{sub 23}C{sub 6} (M = Cr and Mo) in the Inconel 617 weld metal are identified. The necessary conditions for the formation of cracks close to the fusion line of the 309-HP joints are described. Furthermore unmixed zone near the fusion line between HP steel base metal and Inconel 82 weld metal is discussed. An epitaxial growth is characterized at the fusion line of the 309-Alloy 800 and Inconel 617-Alloy 800 joints.

  7. Manufacture of a heat-resistant alloy with modified specifications for HTGR structural applications

    SciTech Connect

    Sahira, K.; Kondo, T.; Takeiri, T.

    1984-07-01

    A method of manufacturing a nuclear grade nickel-base heat-resistant alloy in application to heliumcooled reactor primary circuit components has been developed. The Hastelloy-XR alloy, a version of Hastelloy-X, was made available by combining the basic studies of the oxidation behavior of Hastelloy-X and the improvement of manufacturing techniques. In the primary and remelting steps, the choice of appropriate processes was made by performing numerical analyses of the statistical deviation of both chemical composition and the products' mechanical properties. The feasibility of making larger electroslag remelting ingots with reasonable control of macrosegregation was examined by the calculation of a molten metal pool shape during melting. The hot workability of Hastelloy-XR was confirmed to be equivalent to that of Hastelloy-X and the importance of controlling the thermal and mechanical processes more closely was stressed in obtaining a higher level of quality assurance for the nuclear applications. The possibility of enhancing the high-temperature mechanical performance of Hastelloy-XR was suggested based on the preliminary test results with the heats manufactured with controlled boron content.

  8. Heat resistant alloys as interconnect materials of reduced temperature SOFCs

    NASA Astrophysics Data System (ADS)

    Jian, Li; Jian, Pu; Guangyuan, Xie; Shunxu, Wang; Jianzhong, Xiao

    Heat-resistant alloys, Haynes 230 and SS310, were exposed to air and humidified H 2 at 750 °C for up to 1000 h, respectively, simulating the environments in reduced temperature solid oxide fuel cells (SOFCs). The oxidized samples were characterized by using SEM, EDS and X-ray diffraction to obtain the morphology, thickness, composition and crystal structure of the oxide scales. A mechanism for the formation of metallic Ni-rich nodules on top of the oxide scale in Haynes 230 sample oxidized in humidified H 2 was established. Thermodynamic analysis confirmed that MnCr 2O 4 is the favored spinel phase, together with Cr 2O 3, in the oxide scales.

  9. 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.

  10. 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.

  11. 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.

  12. The metallography of heat treatment effects in a nickel-base casting alloy. A preliminary report.

    PubMed

    Goodall, T G; Lewis, A J

    1979-08-01

    A series of standard tensile specimens produced from a nickel-base removable partial denture casting alloy were subjected to heat treatments at three temperatures and three periods at each temperature. The microstructures developed within the castings disclose changes in both the matrix and interdendritic zones. PMID:296698

  13. Joining precipitation-hardened nickel-base alloys by friction welding

    NASA Technical Reports Server (NTRS)

    Moore, T. J.

    1972-01-01

    Solid state deformation welding process, friction welding, has been developed for joining precipitation hardened nickel-base alloys and other gamma prime-strengthened materials which heretofore have been virtually unweldable. Method requires rotation of one of the parts to be welded, but where applicable, it is an ideal process for high volume production jobs.

  14. 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.

  15. Tool wear mechanisms in the machining of Nickel based super-alloys: A review

    NASA Astrophysics Data System (ADS)

    Akhtar, Waseem; Sun, Jianfei; Sun, Pengfei; Chen, Wuyi; Saleem, Zawar

    2014-06-01

    Nickel based super-alloys are widely employed in aircraft engines and gas turbines due to their high temperature strength, corrosion resistance and, excellent thermal fatigue properties. Conversely, these alloys are very difficult to machine and cause rapid wear of the cutting tool, frequent tool changes are thus required resulting in low economy of the machining process. This study provides a detailed review of the tool wear mechanism in the machining of nickel based super-alloys. Typical tool wear mechanisms found by different researchers are analyzed in order to find out the most prevalent wear mechanism affecting the tool life. The review of existing works has revealed interesting findings about the tool wear mechanisms in the machining of these alloys. Adhesion wear is found to be the main phenomenon leading to the cutting tool wear in this study.

  16. A crystallographic model for nickel base single crystal alloys

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    The purpose of this research is to develop a tool for the mechanical analysis of nickel-base single-crystal superalloys, specifically Rene N4, used in gas turbine engine components. This objective is achieved by developing a rate-dependent anisotropic constitutive model and implementing it in a nonlinear three-dimensional finite-element code. The constitutive model is developed from metallurgical concepts utilizing a crystallographic approach. An extension of Schmid's law is combined with the Bodner-Partom equations to model the inelastic tension/compression asymmetry and orientation-dependence in octahedral slip. Schmid's law is used to approximate the inelastic response of the material in cube slip. The constitutive equations model the tensile behavior, creep response and strain-rate sensitivity of the single-crystal superalloys. Methods for deriving the material constants from standard tests are also discussed. The model is implemented in a finite-element code, and the computed and experimental results are compared for several orientations and loading conditions.

  17. Corrosion initiation and propagation of nickel base alloys in severe sea water applications

    SciTech Connect

    Oldfield, J.W.

    1995-10-01

    Nickel base alloys such as Alloy 625, C22, C276 and 59 are generally considered to have exceptional corrosion resistances in critical sea water applications at ambient temperature. Test results published in recent years however indicate that sever crevice corrosion of some of these alloys may occur under certain conditions. Exposure testes have been carried out in natural and chlorinated sea water on these alloys, together with two high N alloys, Alloy 24 and Alloy 654SMO. Electrochemical studies and simple mathematical mode.lling have also been carried out. These data, together with surface studies, help explain the observed phenomena and assist in the safe selection of alloys for critical sea water applications.

  18. Combined thermodynamic study of nickel-base alloys. Progress report

    SciTech Connect

    Brooks, C. R.; Meschter, P. J.

    1981-02-15

    Achievements during this period are the following: (1) initiation of a high-temperature study of the Ni-Ta system using the galvanic cell technique, (2) emf study of high-temperature thermodynamics in the Ni-Mo system, (3) measured heat capacity data on ordered and disordered Ni/sub 4/Mo, (4) heat capacities of Ni and disordered Ni/sub 3/Fe, and (5) computer correlation of thermodynamic and phase diagram data in binary Ni-base alloys. (MOW)

  19. Environmentally enhanced crack growth in nickel-based alloys at elevated temperatures

    SciTech Connect

    Gao, M.; Chen, S.F.; Chen, G.S.; Wei, R.P.

    1997-12-31

    A recent understanding of environmentally enhanced sustained-load crack growth in nickel-based superalloys at elevated temperatures is presented. This understanding is based on the results of coordinated studies of crack growth kinetics, surface chemistry, and microstructure in a commercial Inconel 718. The results suggest that environmental enhancement of sustained-load crack growth in Inconel 718 is associated with the formation and rupture of niobium oxides at grain boundary surfaces and is controlled mainly by the rate of oxidation and decomposition of niobium carbides at the grain boundaries. Data on other nickel-based alloys in the literature appear to support this suggested role of niobium. Initial results from a study of a niobium-free Ni-18Cr-18Fe alloy (its base composition is identical to Inconel 718) confirm the possible influence of niobium and the proposed mechanism. Some open issues for further investigation are discussed.

  20. Dendritic growth and structure of undercooled nickel base alloys

    NASA Technical Reports Server (NTRS)

    Flemings, M. C.; Shiohara, Y.

    1988-01-01

    The principal objectives of this overall investigation are to: study means for obtaining high undercooling in levitation melted droplets, and study structures produced upon the solidification of these undercooled specimens. Thermal measurements are made of the undercooling, and of the rapid recalescence, to develop an understanding of the solidification mechanism. Comparison of results is made with the modeling studies. Characterization and metallographic work is done to gain an understanding of the relationship between rapid solidification variables and the structures so produced. In ground based work to date, solidification of undercooled Ni-25 wt percent Sn alloy was observed by high-speed cinematography and the results compared with optical temperature measurements. Also in ground based work, high-speed optical temperature measurements were made of the solidification behavior of levitated metal samples within a transparent glass medium. Two undercooled Ni-Sn alloys were examined. Measurements were carried out on samples at undercoolings up to 330 K. Microstructures of samples produced in ground based work were determined by optical metallography and by SEM, and microsegregation by electron microprobe measurements. A series of flight tests were planned to conduct experiments similar to the ground based experiments. The Space Shuttle Columbia carried an alloy undercooled experiment in the STS 61-C mission in January 1986. A sample of Ni-32.5 wt percent Sn eutectic was melted and solidified under microgravity conditions.

  1. A nickel base alloy, NASA WAZ-16, with potential for gas turbine stator vane application

    NASA Technical Reports Server (NTRS)

    Waters, W. J.; Freche, J. C.

    1974-01-01

    A nickel-base superalloy based on the nickel-aluminum-tungsten system designated WAZ-16 was developed for high strength in the 1095 C (2000 F) to 1205 C (2200 F) range. Its tensile strength at the latter temperature is approximately 186 MN/m2 (27,000 psi). The combination of properties of the alloy suggest that it has potential as a stator vane material in advanced gas turbine engines.

  2. 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.

  3. 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).

  4. 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.

  5. 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.

  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. Comparative erosion yields, topographical changes and depth profile analysis of ion eroded nickel-based alloys

    NASA Astrophysics Data System (ADS)

    Navinšek, B.; Panjan, P.; Peternel, M.; Žabkar, A.

    1982-03-01

    Polished polycrystalline alloy targets of Inconel 600, Inconel 625 and Nimonic alloy PE 16 were bombarded with 10 keV He + and A + ions at normal incidence and at room temperature. Comparative studies of the ion erosion yield, as measured by step-height measurements, were made. The correlation between the observed topography and the changes in surface composition and depth profile was studied on irradiated samples by AES. Additionally, total sputtering yields were measured on sputtered films of these materials using a quartz crystal microbalance. The results showed that ion erosion yields are different for the three materials studied, while sputtering yields were similar for He + ions and different for A + ions. A non-linear effect was observed for low dose yields when ion dose and fluence dependence was studied. The topography of ion irradiated nickel-based alloys is specific for a chosen metallographic treatment, determining the bulk and surface structure of the target material.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. Constitutional liquid film migration in the weld heat affected zone of a nickel-base alloy

    SciTech Connect

    Acoff, V.L.; Thompson, R.G.

    1996-12-31

    It has been discovered that when multiphase alloys are rapidly heated, it is possible to cause melting of the interface between phases. This phenomenon was discovered to exist in the weld heat-affected zone (HAZ) of several alloys and is called constitutional liquation. Constitutional liquation occurs if during melting, the bulk composition is in a non-liquid region of the phase diagram but the tie-line between the liquating phases passes through a liquid region. The liquid produced during constitutional liquation can spread along grain boundaries and promote constitutional liquid film migration (CLFM). Nickel-base alloy 718 has been studied to determine the effect that HAZ peak temperature has on supersaturated solute concentration in the areas behind CLFM grain boundaries. In order to promote CLFM, a Gleeble 1000 thermomechanical device was used to subject heat treated rods of alloy 718 to rapid thermal cycles. Results show that the concentration of niobium in the migrated region (area behind the migrated boundary) was higher than the niobium concentration in the matrix for HAZ peak temperatures below the solidus temperature (1,227 C and 1,240 C). For an HAZ peak temperature above the solidus temperature (1,250 C), there was no significant difference between the niobium concentration in the migrated region and the matrix.

  14. Characterization of constitutional liquid film migration in nickel-base alloy 718

    NASA Astrophysics Data System (ADS)

    Acoff, V. L.; Thompson, R. G.

    1996-09-01

    When multiphase alloys are rapidly heated, it is possible to cause melting of the interface between phases. This is called constitutional liquation if, during melting, the bulk composition is in a nonliquid region of the phase diagram but the tie-line between the liquating phases passes through a liquid region. The liquid produced during constitutional liquation can spread along grain boundaries and promote liquid film migration (LFM). This is known as constitutional liquid film migration (CLFM), which is thermodynamically similar to liquid film migration; however, mechanistically there are significant differences. Nickel-base alloy 718 has been studied to show the features of migration that are unique to CLFM. Experimentation consisted of heat-treating rods of alloy 718 to promote the trapping of niobium carbide particles on the grain boundaries. These samples were then subjected to isothermal treatments above their constitutional-liquation temperature, which produced CLFM of the grain boundaries. The movement of the liquid films away from their centers of curvature, the formation of a new solid solution behind the migrated liquid films, and the reversals of curvature of the migrated liquid films confirmed that CLFM was the phenomenon observed. The concentration of niobium behind the migrated liquid films for isothermal treatments below the solidus temperature was shown to be greater than the niobium concentration in the matrix. Above the solidus temperature, there was no increase in niobium concentration. The validity of the coherency strain hypothesis as the driving force for CLFM in alloy 718 is discussed.

  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. Evaluation of dispersion strengthened nickel-base alloy heat shields for space shuttle application

    NASA Technical Reports Server (NTRS)

    Johnson, R., Jr.; Killpatrick, D. H.

    1976-01-01

    The results obtained in a program to evaluate dispersion-strengthened nickel-base alloys for use in a metallic radiative thermal protection system operating at surface temperatures to 1477 K for the space shuttle were presented. Vehicle environments having critical effects on the thermal protection system are defined; TD Ni-20Cr characteristics of material used in the current study are compared with previous results; cyclic load, temperature, and pressure effects on sheet material residual strength are investigated; the effects of braze reinforcement in improving the efficiency of spotwelded joints are evaluated; parametric studies of metallic radiative thermal protection systems are reported; and the design, instrumentation, and testing of full scale subsize heat shield panels in two configurations are described. Initial tests of full scale subsize panels included simulated meteoroid impact tests, simulated entry flight aerodynamic heating, programmed differential pressure loads and temperatures simulating mission conditions, and acoustic tests simulating sound levels experienced during boost flight.

  17. Environmentally-enhanced cavity growth in nickel and nickel-based alloys

    SciTech Connect

    Lu, H.M.; Delph, T.J.; Gao, M.; Wei, R.P.; Dwyer, D.J.

    1996-08-01

    Environmental factors have a strong effect on the elevated-temperature failure behavior of nickel-based alloys. It has been proposed that this effect is due to the reactions of oxygen with carbon in the interior of creep cavities. Such reactions can lead to quite high internal gas pressures, sufficient to result in substantial increases in the cavity growth rates. This hypothesis is investigated by carrying out detailed calculations for a simple system which take into account the coupled effects of oxygen diffusion into the cavity and concurrent cavity growth. The results show that creep cavity growth may or may not be affected by internal, gas-producing reactions, depending upon the nature of the carbon-containing particle, the ratio of the grain boundary oxygen diffusivity to the self-diffusivity of nickel, and upon other factors as well.

  18. 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.

  19. Boron and Zirconium from Crucible Refractories in a Complex Heat-Resistant Alloy

    NASA Technical Reports Server (NTRS)

    Decker, R F; Rowe, John P; Freeman, J W

    1958-01-01

    In a laboratory study of the factors involved in the influence of induction vacuum melting on 55ni-20cr-15co-4mo-3ti-3al heat resistant alloy, it was found that the major factor was the type of ceramic used as the crucible. The study concluded that trace amounts of boron or zirconium derived from reaction of the melt with the crucible refactories improved creep-rupture properties at 1,600 degrees F. Boron was most effective and, in addition, markedly improved hot-workability.

  20. Structural and mechanical properties of heat-resistant granular nickel alloys

    SciTech Connect

    Eremenko, V.I.; Anoshkin, N.F.; Fatkullin, O.Kh.

    1992-05-01

    In order to realize the advantage afforded by granular metallurgy, it is necessary to know the laws of structure formation at every stage of the fabrication of semifinished products for heat-resistant nickel alloys. In this regard the structural features connected with the manufacture of granules by rapid cooling of a melt should be taken into account, as well as those related to the specific technological processes used in reworking (hot isostatic pressing - HIP) and heat treatment. 3 refs., 7 figs., 2 tabs.

  1. Erosion-corrosion performance of nickel-based and copper-based alloys in the Arabian Gulf seawater

    SciTech Connect

    Al-Hashem, A.; Carew, J.; Al-Sayegh, A.

    1996-10-01

    The erosion-corrosion behavior of nickel-based (UNS N0 6022) and copper-based (UNS C71500) alloy tubes in water flowing seawater containing sulfide ions is investigated. Visual, optical and scanning electron microscopy examinations of the internal surfaces of the tubes were conducted to compare the susceptibilities to erosion-corrosion attack of these two alloys, taking into consideration the nature of the product films formed.

  2. Alloying-Element Loss During High-Temperature Processing of a Nickel-Base Superalloy

    NASA Astrophysics Data System (ADS)

    Semiatin, S. L.; Shank, J. M.; Saurber, W. M.; Pilchak, A. L.; Ballard, D. L.; Zhang, F.; Gleeson, B.

    2014-02-01

    The effect of exposure at temperatures commonly used for wrought processing/heat treatment of nickel-base superalloys on the loss of alloying elements at the free surface has been determined. For this purpose, LSHR superalloy samples were exposed at 1408 K (1135 °C) for 0.25 to 4 hours in a vacuum or air furnace. Samples heat treated in the air furnace were either bare or enclosed in quartz capsules that had been evacuated or backfilled with argon. Following heat treatment, the alloy composition as a function of depth below the surface was determined by wavelength dispersive spectroscopy. Samples that had been heat treated in the vacuum furnace exhibited significant depletion of only chromium, a behavior explained on the basis of its high activity in nickel solid solution and corresponding rapid rate of evaporation. By contrast, samples heat treated in air exhibited an irregular scale at the surface and an underlying grain-coarsened, gamma-prime-depleted metal layer lean in aluminum, titanium, and chromium. A yet different behavior characterized primarily by aluminum loss at the surface was noted for samples that had been heat treated in evacuated or argon-backfilled capsules. These observations were interpreted in the context of a reaction between the quartz capsule and the aluminum evaporant.

  3. Corrosion behavior of stainless steel and nickel-base alloys in molten carbonate

    SciTech Connect

    Vossen, J.P.T.; Plomp, L.; Rietveld, G.; Wit, J.H.W. de

    1995-10-01

    The corrosion behavior of five commercially available alloys (AISI 316L, AISI 310S, Inconel 601, Thermax 4762, and Kanthal A1) in molten carbonate under reducing gas atmospheres was investigated with cyclic voltammetry and quasi-stationary polarization curve measurements. The reactions that proceed on these materials at distinct potentials could be deduced by comparison of the cyclic voltammograms and polarization curves with those of pure metals and model alloys. The shape of the polarization curves of all materials strongly depends on the preceding electrochemical treatment. A polarization curve recorded immediately after immersion of a sample resulted in a high anodic current. This implies that the passivation of the materials is poor. When a specimen was conditioned at {minus}1,060 mV for 10 h before recording the polarization curve, the anodic current diminished, which indicates passivation. This occurred for all materials except AISI 316L. A ranking of the corrosion properties was determined from polarization curves of samples that had been conditioned assuming the current densities to be representative. The resistance against corrosion of the alloys increases in the order: AISI 316Lnickel-base alloys.

  4. Optimization of Weld Conditions and Alloy Composition for Welding of Single-Crystal Nickel-Based Superalloys

    SciTech Connect

    Vitek, John Michael; David, Stan A; Babu, Sudarsanam S

    2007-01-01

    Calculations were carried out to identify optimum welding conditions and weld alloy compositions to avoid stray grain formation during welding of single-crystal nickel-based superalloys. The calculations were performed using a combination of three models: a thermal model to describe the weld pool shape and the local thermal gradient and solidification front velocity; a geometric model to identify the local active dendrite growth variant, and a nucleation and growth model to describe the extent of stray grain formation ahead of the advancing solidification front. Optimum welding conditions (low weld power, high weld speed) were identified from the model calculations. Additional calculations were made to determine potential alloy modifications that reduce the solidification temperature range while maintaining high gamma prime content. The combination of optimum weld conditions and alloy compositions should allow for weld repair of single-crystal nickel-based superalloys without sacrificing properties or performance.

  5. Creep and stress rupture of a mechanically alloyed oxide dispersion and precipitation strengthened nickel-base superalloy

    NASA Technical Reports Server (NTRS)

    Howson, T. E.; Tien, J. K.; Mervyn, D. A.

    1980-01-01

    The creep and stress rupture behavior of a mechanically alloyed oxide dispersion strengthened (ODS) and gamma-prime precipitation strengthened nickel-base alloy (alloy MA 6000E) was studied at intermediate and elevated temperatures. At 760 C, MA 6000E exhibits the high creep strength characteristic of nickel-base superalloys and at 1093 C the creep strength is superior to other ODS nickel-base alloys. The stress dependence of the creep rate is very sharp at both test temperatures and the apparent creep activation energy measured around 760 C is high, much larger in magnitude than the self-diffusion energy. Stress rupture in this large grain size material is transgranular and crystallographic cracking is observed. The rupture ductility is dependent on creep strain rate, but usually is low. These and accompanying microstructural results are discussed with respect to other ODS alloys and superalloys and the creep behavior is rationalized by invoking a recently-developed resisting stress model of creep in materials strengthened by second phase particles.

  6. Characteristics of heat resistant alloys Ti10Nb45Al and Ti18Nb48Al

    SciTech Connect

    Weijun Zhang; Guoliang Chen; Yandong Wang; Zuqing Sun )

    1993-05-01

    Based on a systematic study of the ternary Ti-Nb-Al system, two attractive heat resistant alloys, Ti10Nb45Al and Ti18Nb48Al, were developed, and the characteristics of these alloys were discussed: (1) After annealing at 1,200 C for 240 h and furnace cooling to room temperature, the Ti10Nb45Al alloy exhibits an [alpha][sub 2] + [gamma] lamellar microstructure, and the Ti18Nb48Al alloy shows a plate-like structure consisting of [alpha][sub 2], [gamma] and [gamma][sub 1] phases. (2) The specific strengths of Ti10Nb45Al and Ti18Nb48Al are much higher than TiAl and superalloys in the temperature range of 800 [approximately] 1,100 C. The compressive yield strengths of these alloys are on the order of 700 MPa at 800 C and 350 MPa at 1,100 C. The density of these alloys is about 4.3 g/cm[sup 3]. (3) The annealed Ti10Nb45Al and Ti18Nb48Al exhibit some ductility at room temperature, with the compressive elongation on the order of 12% and the fracture toughness as high as 16 MPa[radical]m. The ductile-brittle transformation temperatures for Ti10Nb45Al and Ti18Nb48Al are 650 C and 750 C, respectively. (4) The parabolic constant K[sub p] for oxidation of Ti10Nb45Al and Ti18Nb48Al are 0.88 and 0.29 mg[sup 2]cm[sup [minus]4]h[sup [minus]1] respectively, which are two orders of magnitude lower than that of TiAl and Ti[sub 3]Al alloys.

  7. 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. PMID:12963454

  8. 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.

  9. A View of Compatible Heat-Resistant Alloy and Coating Systems at High-Temperatures

    SciTech Connect

    Narita, Toshio

    2009-09-14

    Conventional and advanced coatings were reviewed, and it was pointed out that the coated Ni-base superalloys decreased their creep rupture life significantly at higher temperatures, and the advanced high strength superalloy became more remarkably. Concept of diffusion barrier coating system (DBC system) and their formation process was introduced, and the results obtained for several heat-resistant alloys, stainless steel (SUS310S), Ni-Mo base alloy (Hastelloy-X), and 4{sup th} generation single crystal superalloy (TMS-138) were given. It was noted that creep-rupture life of the SUS310S and Hastelloy-X with the DBC system became longer than those of the bare alloys with or without conventional {beta}-NiAl coatings. This is due to slow creep-deformation of the Re-base alloy layer as the diffusion barrier. A novel concept based on combination of superalloys and coatings was proposed, by taking both the materials science and corrosion science into consideration.

  10. A View of Compatible Heat-Resistant Alloy and Coating Systems at High-Temperatures

    NASA Astrophysics Data System (ADS)

    Narita, Toshio

    2009-09-01

    Conventional and advanced coatings were reviewed, and it was pointed out that the coated Ni-base superalloys decreased their creep rupture life significantly at higher temperatures, and the advanced high strength superalloy became more remarkably. Concept of diffusion barrier coating system (DBC system) and their formation process was introduced, and the results obtained for several heat-resistant alloys, stainless steel (SUS310S), Ni-Mo base alloy (Hastelloy-X), and 4th generation single crystal superalloy (TMS-138) were given. It was noted that creep-rupture life of the SUS310S and Hastelloy-X with the DBC system became longer than those of the bare alloys with or without conventional β-NiAl coatings. This is due to slow creep-deformation of the Re-base alloy layer as the diffusion barrier. A novel concept based on combination of superalloys and coatings was proposed, by taking both the materials science and corrosion science into consideration.

  11. Effect of Alloy 625 Buffer Layer on Hardfacing of Modified 9Cr-1Mo Steel Using Nickel Base Hardfacing Alloy

    NASA Astrophysics Data System (ADS)

    Chakraborty, Gopa; Das, C. R.; Albert, S. K.; Bhaduri, A. K.; Murugesan, S.; Dasgupta, Arup

    2016-04-01

    Dashpot piston, made up of modified 9Cr-1Mo steel, is a part of diverse safety rod used for safe shutdown of a nuclear reactor. This component was hardfaced using nickel base AWS ER NiCr-B alloy and extensive cracking was experienced during direct deposition of this alloy on dashpot piston. Cracking reduced considerably and the component was successfully hardfaced by application of Inconel 625 as buffer layer prior to hardface deposition. Hence, a separate study was undertaken to investigate the role of buffer layer in reducing the cracking and on the microstructure of the hardfaced deposit. Results indicate that in the direct deposition of hardfacing alloy on modified 9Cr-1Mo steel, both heat-affected zone (HAZ) formed and the deposit layer are hard making the thickness of the hard layer formed equal to combined thickness of both HAZ and deposit. This hard layer is unable to absorb thermal stresses resulting in the cracking of the deposit. By providing a buffer layer of Alloy 625 followed by a post-weld heat treatment, HAZ formed in the modified 9Cr-1Mo steel is effectively tempered, and HAZ formed during the subsequent deposition of the hardfacing alloy over the Alloy 625 buffer layer is almost completely confined to Alloy 625, which does not harden. This reduces the cracking susceptibility of the deposit. Further, unlike in the case of direct deposition on modified 9Cr-1Mo steel, dilution of the deposit by Ni-base buffer layer does not alter the hardness of the deposit and desired hardness on the deposit surface could be achieved even with lower thickness of the deposit. This gives an option for reducing the recommended thickness of the deposit, which can also reduce the risk of cracking.

  12. The impact of carbon on single crystal nickel-base superalloys: Carbide behavior and alloy performance

    NASA Astrophysics Data System (ADS)

    Wasson, Andrew Jay

    Advanced single crystal nickel-base superalloys are prone to the formation of casting grain defects, which hinders their practical implementation in large gas turbine components. Additions of carbon (C) have recently been identified as a means of reducing grain defects, but the full impact of C on single crystal superalloy behavior is not entirely understood. A study was conducted to determine the effects of C and other minor elemental additions on the behavior of CMSX-4, a commercially relevant 2nd generation single crystal superalloy. Baseline CMSX-4 and three alloy modifications (CMSX-4 + 0.05 wt. % C, CMSX-4 + 0.05 wt. % C and 68 ppm boron (B), and CMSX-4 + 0.05 wt. % C and 23 ppm nitrogen (N)) were heat treated before being tested in high temperature creep and high cycle fatigue (HCF). Select samples were subjected to long term thermal exposure (1000 °C/1000 hrs) to assess microstructural stability. The C modifications resulted in significant differences in microstructure and alloy performance as compared to the baseline. These variations were generally attributed to the behavior of carbide phases in the alloy modifications. The C modification and the C+B modification, which both exhibited script carbide networks, were 25% more effective than the C+N modification (small blocky carbides) and 10% more effective than the baseline at preventing grain defects in cast bars. All C-modified alloys exhibited reduced as-cast gamma/gamma' eutectic and increased casting porosity as compared to baseline CMSX-4. The higher levels of porosity (volume fractions 0.002 - 0.005 greater than the baseline) were attributed to carbides blocking molten fluid flow during the final stages of solidification. Although the minor additions resulted in reduced solidus temperature by up to 16 °C, all alloys were successfully heat treated without incipient melting by modifying commercial heat treatment schedules. In the B-containing alloy, heat treatment resulted in the transformation of

  13. 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.

  14. High gas velocity oxidation and hot corrosion testing of oxide dispersion-strengthened nickel-base alloys

    NASA Technical Reports Server (NTRS)

    Deadmore, D. L.; Lowell, C. E.

    1975-01-01

    Several oxide dispersion strengthened (ODS) nickel-base alloys were tested in high velocity gases for cyclic oxidation resistance at temperatures to 1200 C and times to 500 hours and for hot corrosion resistance at 900 C for 200 hours. Nickel-chromium-aluminum ODS alloys were found to have superior resistance to oxidation and hot corrosion when compared to bare and coated nickel-chromium ODS alloys. The best of the alloys tested had compositions of nickel - 15.5 to 16 weight percent chromium with aluminum weight percents between 4.5 and 5.0. All of the nickel-chromium-aluminum ODS materials experienced small weight losses (less than 16 mg/sq cm).

  15. 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.

  16. 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.

  17. Development, processing and fabrication of a nickel based nickel-chromium-iron alloy

    NASA Astrophysics Data System (ADS)

    Akinlade, Dotun Adebayo

    An optimal powder metallurgy (P/M) approach to produce a nickel base Superalloy similar in composition to INCONEL(TM) 600 was carried out utilising a simple uniaxial pressing process. The efficiencies of a lubricant addition, binder, sintering times and temperatures were measured in terms of green and sintered densities as well as microstructural changes that occurred during processing. It was observed that with increasing % polyvinyl alcohol (PVA), an overall decrease in density of compact was obtained and that using 0.75wt % of lubricant (microwax) green densities in excess of 70% can be obtained. The samples were subsequently sintered in air at 1270°C for times ranging from 0.5h to 5h and also in vacuum (6 millitorr) with temperatures ranging from 1260 through to 1400°C. The air sintering was carried out to optimize sintering time, whereas the vacuum sintering was employed to optimize sintering temperature. On sintering for 5h in air, chromium enrichment occurred at the grain boundaries with subsequent depletion of nickel and iron; this was not noted for 2h sintering or for sintering under vacuum. The optimum sintering conditions were determined to be at 1300°C sintering for 2h in vacuum. The samples processed under the optimum conditions were successfully cold rolled to 40% of the original thickness without cracking. An investigation was also undertaken to determine the effect of Al concentration (1-12w/o) on the microstructure of the powder metallurgically (P/M) processed Ni-Cr-Fe ternary alloy, with a view to determine the concentration of aluminium that would yield a homogenously distributed and optimum volume fraction of the intermetallic-gamma'(Ni3Al) phase without the formation of topologically closed packed phases in the ternary alloy. The phases that were likely to form with the variation in concentration of Al were first simulated by JMatPro(TM) thermodynamic software package, and then Ni-Cr-Fe alloys with varying concentration of aluminum were

  18. Structural transformations in heat-resistant protective coatings on nickel alloys

    SciTech Connect

    Veksler, Yu.G.; Lesnikov, V.P.; Paleeva, S.Ya.; Lesnikova, E.G.; Myal'nitsa, G.F.

    1987-09-01

    In this work a comprehensive metallophysical study was carried out for two aluminosilicide slip coatings of the systems Al-Si and Al-Nb-Si and an electron-beam Co-Cr-Al-Y coating on alloy EP-539 (17...19% Cr, 4...6% Co, 2.5...4% W, 4.5...6.5% Mo, 2...3% Ti, 3...4% Al, 1.4...2% Nb, balance Ni) after high-temperature testing. The protective properties of the coatings were evaluated from the results of laboratory tests for heat resistance at 1000/sup 0/C in the combustion products of diesel fuel with added sulfur at 970, 1000, and 1060/sup 0/C for 100 h and after full-scale tests for 150, 250, 400, and 700 h. Metallographic, hardness, x-ray, and micro x-ray studies of the coating were carried out. Layer-by-layer phase composition and the lattice spacing of the main phases were determined. X-ray analysis was carried out in an a DRON-1 diffractometer in copper K/sub ..-->../-radiation, and x-ray microanalysis was carried out in a MS-46 Cameca microanalyzer

  19. UNDERSTANDING THE MECHANISMS CONTROLLING ENVIRONMENTALLY-ASSISTED INTERGRANULAR CRACKING OF NICKEL-BASE ALLOYS

    SciTech Connect

    Gary S. Was

    2004-02-13

    Creep and IG cracking of nickel-base alloys depend principally on two factors--the deformation behavior and the effect of the environment. We have shown that both contribute to the observed degradation in primary water. The understanding of cracking does not lie wholly within the environmental effects arena, nor can it be explained only by intrinsic mechanical behavior. Rather, both processes contribute to the observed behavior in primary water. In this project, we had three objectives: (1) to verify that grain boundaries control deformation in Ni-16Cr-9Fe at 360 C, (2) to identify the environmental effect on IGSCC, and (3) to combine CSLBs and GBCs to maximize IGSCC resistance in Ni-Cr-Fe in 360 C primary water. Experiments performed in hydrogen gas at 360 C confirm an increase in the primary creep rate in Ni-16Cr-9Fe at 360 C due to hydrogen. The creep strain transients caused by hydrogen are proposed to be due to the collapse of dislocation pile-ups, as confirmed by observations in HVEM. The observations only partially support the hydrogen-enhanced plasticity model, but also suggest a potential role of vacancies in the accelerate creep behavior in primary water. In high temperature oxidation experiments designed to examine the potential for selective internal oxidation in the IGSCC process, cracking is greatest in the more oxidizing environments compared to the low oxygen potential environments where nickel metal is stable. In Ni-Cr-Fe alloys, chromium oxides form preferentially along the grain boundaries, even at low oxygen potential, supporting a potential role in grain boundary embrittlement due to preferential oxidation. Experiments designed to determine the role of grain boundary deformation on intergranular cracking have established, for the first time, a cause-and-effect relationship between grain boundary deformation and IGSCC. That is, grain boundary deformation in Ni-16Cr-9Fe in 360 C primary water leads to IGSCC of the deformed boundaries. As well

  20. Possibility of enhancement of the high-temperature strength and the heat resistance of a nickel aluminide-based structural intermetallic alloy

    NASA Astrophysics Data System (ADS)

    Bazyleva, O. A.; Shestakov, A. V.; Arginbaeva, E. G.; Turenko, E. Yu.

    2016-01-01

    The assimilation of a number of rare-earth metals (REM = praseodymium, neodymium, erbium) in a cast high-temperature nickel aluminide-based intermetallic alloy and the effect of REM alloying of the alloy on the critical temperatures, the high-temperature strength, and the heat resistance (time to failure) of the structural alloy are studied. It is shown that the heat resistance and the time to failure of the alloy at 1200°C can be increased by microalloying of the intermetallic alloy with REM.

  1. Heat treating of a lamellar eutectic alloy (gamma/gamma prime + delta). [heat resistant alloys

    NASA Technical Reports Server (NTRS)

    Tewari, S. N.; Dreshfield, R. L.

    1976-01-01

    Eutectic superalloys are being developed at several laboratories for application as aircraft gas turbine airfoils. One such alloy was subjected to several heat treatments to determine if its mechanical properties could be improved. It was found that by partially dissolving the alloy at 1210 C and then aging at 900 C the tensile strength can be increased about 12 percent at temperatures up to 900 C. At 1040 C no change in tensile strength was observed. Times to rupture were measured between 760 and 1040 C and were essentially the same or greater than for as-grown material. Tensile and rupture ductility of the alloy are reduced by heat treatment. Photographs of the microstructure are shown.

  2. Electrothermal atomic absorption spectrometric determination of copper in nickel-base alloys with various chemical modifiers*1

    NASA Astrophysics Data System (ADS)

    Tsai, Suh-Jen Jane; Shiue, Chia-Chann; Chang, Shiow-Ing

    1997-07-01

    The analytical characteristics of copper in nickel-base alloys have been investigated with electrothermal atomic absorption spectrometry. Deuterium background correction was employed. The effects of various chemical modifiers on the analysis of copper were investigated. Organic modifiers which included 2-(5-bromo-2-pyridylazo)-5-(diethylamino-phenol) (Br-PADAP), ammonium citrate, 1-(2-pyridylazo)-naphthol, 4-(2-pyridylazo)resorcinol, ethylenediaminetetraacetic acid and Triton X-100 were studied. Inorganic modifiers palladium nitrate, magnesium nitrate, aluminum chloride, ammonium dihydrogen phosphate, hydrogen peroxide and potassium nitrate were also applied in this work. In addition, zirconium hydroxide and ammonium hydroxide precipitation methods have also been studied. Interference effects were effectively reduced with Br-PADAP modifier. Aqueous standards were used to construct the calibration curves. The detection limit was 1.9 pg. Standard reference materials of nickel-base alloys were used to evaluate the accuracy of the proposed method. The copper contents determined with the proposed method agreed closely with the certified values of the reference materials. The recoveries were within the range 90-100% with relative standard deviation of less than 10%. Good precision was obtained.

  3. Physical properties of a nickel-base alloy prepared by isostatic pressing and sintering of the powdered metal.

    PubMed

    Fuys, R A; Craig, R G; Asger, K

    1976-04-01

    The physical and mechanical properties of samples of a nickel-base alloy fabricated by powder metallurgy were determined. The particle sizes of the powders used to make the samples varied from -80/ +200 mesh to -325 mesh. The compaction pressure varied from 138 to 414 MN/m2 and the sintering temperature varied from 1150 to 1250 degrees C. The shrinkage during processing, the porosity, tensile strength, yield strength, elongation, and elastic modulus were used to characterize the samples. The strength of the samples generally increased with decreasing particle size of the powder and increasing compaction pressure and sintering temperatures. The porosity and strength, therefore, could be varied over a wide range by controlling the various parameters. The properties of the samples prepared by powder metallurgy were compared with those of the cast alloy and compact bone. Conditions can be selected that will yield equivalent or better properties by powder metallurgy than by casting. PMID:1066448

  4. The Influence of Dynamic Strain Aging on Fatigue and Creep-Fatigue Characterization of Nickel-Base Solid Solution Strengthened Alloys

    SciTech Connect

    L.J. Carroll; W.R. Lloyd; J.A. Simpson; R.N. Wright

    2010-12-01

    The nickel-base solid solution alloys, Alloy 617 and Alloy 230, have been observed to exhibit serrated yielding or dynamic strain aging (DSA) in a temperature/strain rate regime of interest for intermediate heat exchangers (IHX) of high temperature nuclear reactors. At 800°C, these nickel-base alloys are prone to large serrated yielding events at relatively low strains. The presence of DSA introduces challenges in characterizing the creep-fatigue and low cycle fatigue behavior. These challenges include inability to control the target strains as a result of DSA induced strain excursions and distorted hysteresis loops. Methods to eliminate or reduce the influence of DSA on creep-fatigue testing have been investigated, including varying the strain rate, stepping to the target strain, and adjusting servo-hydraulic tuning parameters. It has not been possible to eliminate the impact of serrated flow in the temperature range of interest for these alloys without compromising the desired test protocols.

  5. The role of salt melts on the corrosion of steels and nickel-based alloys in waste incineration plants

    SciTech Connect

    Spiegel, M.

    1999-11-01

    Laboratory experiments were carried out to study the corrosion behavior of steels and nickel-based alloys beneath heavy-metal-rich chloride and sulfate melts. Exposure tests on low- and high alloy steels in (Ca, K, Na, Pb, Zn)-sulfate mixtures in N{sub 2} - 5 vol.% O{sub 2} at 600 C have shown accelerated corrosion after addition of PbSO{sub 4} and ZnSO{sub 4}. The corrosion products were identified as (Fe, Ni)-oxide precipitates in contact with the gas phase and chromium-rich corrosion products close to the metal. Thermogravimetric investigations in He-5 vol.% O{sub 2} with the 2.25Cr-1Mo steel and also Alloy 625 have shown that severe corrosion occurred in the presence of a 50 wt.% ZnCl{sub 2}-50wt.% KCl salt mixture in the temperature range from 300 to 500 C. The corrosion products on 2.25Cr-1Mo were found to be Zn-rich iron-oxide precipitates in contact with the gas phase and a Fe{sub 2}O{sub 3} layer underneath. In contact with the metal, a mixture of iron-chlorides and Fe{sub 2}O{sub 3} was detected, together with variable amounts of K and Zn. A thick scale has formed on Alloy 625, consisting of nickel- and chromium-oxides with some dissolved Mo.

  6. Effects of prior deformation and annealing process on microstructure and annealing twin density in a nickel based alloy

    SciTech Connect

    Li, Zhigang; Zhang, Lanting; Sun, Nairong; Sun, Yanle; Shan, Aidang

    2014-09-15

    The nickel based alloys with different Σ3 boundary density were achieved by cold-rolling and subsequent annealing treatment. Electron backscattered diffraction analysis showed that the grain size distribution changed with the processing parameters, and the discontinuous Σ3 boundary became continuous with the increase of prior deformation level. Furthermore, the Σ3 boundary density was found to be manipulated by both grain size distribution and Σ3 boundary density per grain which showed an increasing trend with prior deformation level and annealing temperature. - Highlights: • The prior deformation amount influenced the morphology of Σ3 boundary. • The grain size was not the only factor influencing Σ3 boundary density. • The fact that grain size distribution had an important effect on Σ3 boundary density was confirmed. • The nature of grain size distribution on Σ3 boundary density was revealed. • There was a great deviation in Σ3 boundary density between experimental results and predictions.

  7. Arrhenius-Type Constitutive Model for High Temperature Flow Stress in a Nickel-Based Corrosion-Resistant Alloy

    NASA Astrophysics Data System (ADS)

    Wang, L.; Liu, F.; Cheng, J. J.; Zuo, Q.; Chen, C. F.

    2016-04-01

    Hot deformation behavior of Nickel-based corrosion-resistant alloy (N08028) was studied in compression tests conducted in the temperature range of 1050-1200 °C and the strain rate range of 0.001-1 s-1. The flow stress behavior and microstructural evolution were observed during the hot deformation process. The results show that the flow stress increases with deformation temperature decreasing and strain rate increasing, and that the deformation activation energy ( Q) is not a constant but increases with strain rate increasing at a given strain, which is closely related with dislocation movement. On this basis, a revised strain-dependent hyperbolic sine constitutive model was established, which considered that the "material constants" in the original model vary as functions of the strain and strain rate. The flow curves of N08028 alloy predicted by the proposed model are in good agreement with the experimental results, which indicates that the revised constitutive model can estimate precisely the flow curves of N08028 alloy.

  8. Nickel-based alloy/austenitic stainless steel dissimilar weld properties prediction on asymmetric distribution of laser energy

    NASA Astrophysics Data System (ADS)

    Zhou, Siyu; Ma, Guangyi; Chai, Dongsheng; Niu, Fangyong; Dong, Jinfei; Wu, Dongjiang; Zou, Helin

    2016-07-01

    A properties prediction method of Nickel-based alloy (C-276)/austenitic stainless steel (304) dissimilar weld was proposed and validated based on the asymmetric distribution of laser energy. Via the dilution level DC-276 (the ratio of the melted C-276 alloy), the relations between the weld properties and the energy offset ratio EC-276 (the ratio of the irradiated energy on the C-276 alloy) were built, and the effects of EC-276 on the microstructure, mechanical properties and corrosion resistance of dissimilar welds were analyzed. The element distribution Cweld and EC-276 accorded with the lever rule due to the strong convention of the molten pool. Based on the lever rule, it could be predicted that the microstructure mostly consists of γ phase in each weld, the δ-ferrite phase formation was inhibited and the intermetallic phase (P, μ) formation was promoted with the increase of EC-276. The ultimate tensile strength σb of the weld joint could be predicted by the monotonically increasing cubic polynomial model stemming from the strengthening of elements Mo and W. The corrosion potential U, corrosion current density I in the active region and EC-276 also met the cubic polynomial equations, and the corrosion resistance of the dissimilar weld was enhanced with the increasing EC-276, mainly because the element Mo could help form a steady passive film which will resist the Cl- ingress.

  9. Nickel-based gadolinium alloy for neutron adsorption application in RAM packages.

    SciTech Connect

    Mizia, Ronald A.; Dupont, John Neuman; McConnell, Paul E.; Robino, Charles Victor

    2005-02-01

    The National Spent Nuclear Fuel Program, located at the Idaho National Laboratory (INL), coordinates and integrates national efforts in management and disposal of US Department of Energy (DOE)-owned spent nuclear fuel. These management functions include development of standardised systems for long-term disposal in the proposed Yucca Mountain repository. Nuclear criticality control measures are needed in these systems to avoid restrictive fissile loading limits because of the enrichment and total quantity of fissile material in some types of the DOE spent nuclear fuel. This need is being addressed by development of corrosion-resistant, neutron-absorbing structural alloys for nuclear criticality control. This paper outlines results of a metallurgical development programme that is investigating the alloying of gadolinium into a nickel-chromium-molybdenum alloy matrix. Gadolinium has been chosen as the neutron absorption alloying element due to its high thermal neutron absorption cross section and low solubility in the expected repository environment. The nickel-chromium-molybdenum alloy family was chosen for its known corrosion performance, mechanical properties, and weldability. The workflow of this programme includes chemical composition definition, primary and secondary melting studies, ingot conversion processes, properties testing, and national consensus codes and standards work. The microstructural investigation of these alloys shows that the gadolinium addition is present in the alloy as a gadolinium-rich second phase. The mechanical strength values are similar to those expected for commercial Ni-Cr-Mo alloys. The alloys have been corrosion tested with acceptable results. The initial results of weldability tests have also been acceptable. Neutronic testing in a moderated critical array has generated favourable results. An American Society for Testing and Materials material specification has been issued for the alloy and a Code Case has been submitted to the

  10. Low cycle fatigue life of two nickel-base casting alloys in a hydrogen environment. [for high-pressure oxidizer turbopump turbine nozzles

    NASA Technical Reports Server (NTRS)

    Cooper, R. A.

    1976-01-01

    Samples of two nickel-base casting alloys, Mar-M-246 (a Martin Company alloy) and 713LC (a low-carbon modification of the alloy 713C developed by International Nickel Company) were tested as candidate materials for the high-pressure fuel and high-pressure oxidizer turbopump turbine nozzles. The samples were subjected to tensile tests and to low cycle fatigue tests in high-pressure hydrogen to study the influence of the hydrogen environment. The Mar-M-246 material was found to have a three times higher cyclic life in hydrogen than the 713LC alloy, and was selected as the nozzle material.

  11. The crevice corrosion behavior of chromium stainless steel and nickel base alloys in a reverse osmosis plant utilizing seawater

    SciTech Connect

    Al-Odwani, A.; Carew, J.; Al-Hashem, A.

    1999-11-01

    The crevice corrosion tests were performed on UNS S31603, UNS S31703, UNS S31726, UNS S31254, UNS N08904, UNS N625, UNS N825 and UNS N276 was investigated in seawater and neutral brine solution using a multiple crevice washer assembly. PTFE multiple-crevice washers were bolted to both sides of the test specimens with PTFE bolts and nuts. The specimens were exposed to seawater flowing at a rate of 100 L/h for periods of 3,000 h and 6,000 h. Duplicate specimens were immersed in a plexiglass cell containing the flowing seawater at a temperature of 30 C. The results showed that all the tested coupons were susceptible to some degree of crevice corrosion attack. However, the stainless steels were the most severely affected. The degree of crevice corrosion attack for the nickel base alloys decreased as the percentage of molybdenum content in the alloys increased. Destruction of the passive layer by the concentration of chloride or acidity and reduction of hydrogen ions at the crevices is believed to be the cause of the crevice attack.

  12. The effect of carbon on the metallography of a nickel base removable partial denture casting alloy.

    PubMed

    Lewis, A J

    1979-04-01

    This study has demonstrated the pattern of carbide development associated with progressive increases in carbon content in a series of six nickel chromium alloys. The carbon content is critical since it influences the production and distribution of carbides, which have been shown to alter the mechanical properties, of the nickel chromium alloys, that are dependent upon the development of gamma prime. Furthermore, it has been shown that the attainment of suitable strength is invariably associated with an unacceptable level of ductility. PMID:288385

  13. Physical Simulation of Friction Stir Welding and Processing of Nickel-Base Alloys Using Hot Torsion

    NASA Astrophysics Data System (ADS)

    Rule, James R.; Lippold, John C.

    2013-08-01

    The Gleeble hot torsion test was utilized in an attempt to simulate the friction stir-processed microstructure of three Ni-base alloys: Hastelloy X, Alloy 625, and Alloy 718. The simulation temperatures were based on actual thermal cycles measured by embedded thermocouples during friction stir processing of these alloys. Peak process temperatures were determined to be approximately 1423 K (1150 °C) for Hastelloy X and Alloy 625 K and 1373 K (352 °C and 1100 °C) for Alloy 718. The peak temperature and cooling rates were programed into the Gleeble™ 3800 thermo-mechanical simulator to reproduce the stir zone and thermo-mechanically affected zone (TMAZ) microstructures. The TMAZ was successfully simulated using this technique, but the stir zone microstructure could not be accurately reproduced, with hot torsion samples exhibiting larger grain size than actual friction stir processing trials. Shear stress and strain rates as a function of temperature were determined for each material using hot torsion simulation.

  14. Evaluation and Characterization of Iron- and Nickel-Based Alloys for Microturbine Recuperators

    SciTech Connect

    Lara-Curzio, Edgar; Trejo, Rosa M; More, Karren Leslie; Maziasz, Philip J; Pint, Bruce A

    2005-01-01

    The effects of stress, temperature and time of exposure to microturbine exhaust gases on the mechanical properties and corrosion resistance of alloys HR-120(reg. sign) and 230(reg. sign) was investigated at turbine exhaust temperatures between 620 C and 760 C. It was found that the ultimate tensile strength and ductility of alloy 230(reg. sign) decreased by 30% and 60%, respectively, after 500 hours exposure at 752 C. At the lowest exposure temperature of 679 C the ultimate tensile strength and ductility decreased by 10% and 25%, respectively. The ultimate tensile strength and ductility of HR-120(reg. sign) alloy decreased by 15% and 50%, respectively, after 500 hours exposure at 745 C. At the lowest exposure temperature of 632 C the ultimate tensile strength and ductility decreased by 10% and 23%, respectively. The microstructural changes associated with exposure to microturbine exhaust gases are analyzed and discussed.

  15. Interdiffusional effects between tungsten fibers and an iron-nickel-base alloy

    NASA Technical Reports Server (NTRS)

    Caulfield, T.; Bellows, R. S.; Tien, J. K.

    1985-01-01

    Tungsten fibers in the INCOLOY 903 alloy were annealed for over 100 hours at 1038 C and 1200 C. It was found that interdiffusion results in the formation of a reaction zone. SEM-EDS probe analysis showed that the chemistries across this zone were constant, suggesting the zone was a compound phase. The composition of the compound was estimated to be that of a mu-type phase. The local chemistry (in atomic percent) at the reaction zone/alloy matrix interface was found to be approximately 8 pct W, 1.2 pct Nb, 40 pct Fe, 14 pct Co, and 36 pct Ni. In addition, recrystallization was observed in both the remaining tungsten fiber and the nearby INCOLOY 903 matrix after annealing at 1200 C, but not at 1038 C. The results of this study suggest that reaction zone growth kinetics can be minimized by the reduction of Co and Fe and the increase of W in the matrix alloy.

  16. Crack propagation in stainless steels and nickel base alloys in a commercial operating BWR

    SciTech Connect

    Jenssen, A.; Morin, U.; Bengtsson, B.; Jansson, C.

    1995-12-31

    Crack propagation was investigated to study critical stress intensity factors for intergranular stress corrosion cracking (IGSCC), and crack growth rates in various materials. Modified bolt loaded compact tension (CT) specimens were exposed to BWR normal water chemistry (NWC) in a commercially operating BWR. The test facility was a pressure vessel, originally designed for high temperature magnetite filters. Stainless steels (SS) of Types 304 SS and 316 SS were included in the test matrix, as well as the Ni base weld materials alloys 82 and 182. The SS were investigated both in sensitized and in cold worked condition. For alloy 182 various parameters were studied, such as the effect of the carbon stabilization parameter, and the as-welded condition versus a post weld heat treatment (PWHT). Crack growth was measured annually, during the normal outages, by an optical microscope. The results were evaluated as crack growth rate as a function of stress intensity. A few specimens have been removed from testing for fractographic examination. Most of the specimens were exposed to NWC for more than 30,000 hours. Alloy 82 in as welded condition was found to be susceptible to IGSCC, at least at stress intensities above 30 MPa{radical}m. For alloy 182, in as welded condition, significant crack growth was detected in all specimens. No beneficial effect of the carbon stabilization parameter could be found. PWHT had a beneficial effect on the IGSCC susceptibility of alloy 182, and at stress intensities below 30 MPa{radical}m the crack growth rates were one to two orders of magnitude lower, compared to alloy 182 in as welded condition. As expected, an increasing susceptibility to IGSCC with increasing degree of cold work was found for stainless steel. At 5% cold work Type 304 SS cracked at a higher rate than Type 316NG with the same degree of cold work. At 20% cold work Type 304 SS and Type 316NG cracked at essentially the same rate.

  17. Growth Stresses in Thermally Grown Oxides on Nickel-Based Single-Crystal Alloys

    NASA Astrophysics Data System (ADS)

    Rettberg, Luke H.; Laux, Britta; He, Ming Y.; Hovis, David; Heuer, Arthur H.; Pollock, Tresa M.

    2016-03-01

    Growth stresses that develop in α-Al2O3 scale that form during isothermal oxidation of three Ni-based single crystal alloys have been studied to elucidate their role in coating and substrate degradation at elevated temperatures. Piezospectroscopy measurements at room temperature indicate large room temperature compressive stresses in the oxides formed at 1255 K or 1366 K (982 °C or 1093 °C) on the alloys, ranging from a high of 4.8 GPa for René N4 at 1366 K (1093 °C) to a low of 3.8 GPa for René N5 at 1255 K (982 °C). Finite element modeling of each of these systems to account for differences in coefficients of thermal expansion of the oxide and substrate indicates growth strains in the range from 0.21 to 0.44 pct at the oxidation temperature, which is an order of magnitude higher than the growth strains measured in the oxides on intermetallic coatings that are typically applied to these superalloys. The magnitudes of the growth strains do not scale with the parabolic oxidation rate constants measured for the alloys. Significant spatial inhomogeneities in the growth stresses were observed, due to (i) the presence of dendritic segregation and (ii) large carbides in the material that locally disrupts the structure of the oxide scale. The implications of these observations for failure during cyclic oxidation, fatigue cycling, and alloy design are considered.

  18. Oxidation resistance of eight heat-resistant alloys at 870, 980, 1,095, and 1,150 C

    SciTech Connect

    Rundell, G.; McConnell, J. )

    1991-10-01

    Oxidation testing of heat-resistant alloys is described. The testing procedure utilized weight-gain measurements using one specimen, which was withdrawn and weighted at intervals of 1 week, for 10-18 weeks. The specimen was placed in a porcelain cup during exposure and covered upon cooling to retain spalled oxide. Weight gain was used to determine the kinetics of oxidation and was extrapolated to 3,000 hr. The specimen was withdrawn at the end of the exposure, weighed, cathodically descaled, and reweighed. The ratio of oxygen ions to metal ions was determined for each alloy and test temperature. This ratio approaches the stoichiometric ratio for Fe{sub 3}O{sub 4} or Cr{sub 2}O{sub 3}. The ratio for each test is used to convert weight gain to weight loss. The amount of adherent oxide was determined as well as the total amount of oxide, leading to an expression for oxide adherency. The oxidation resistance of Fe-Cr-Ni alloys increased with increasing Cr and Ni, with Cr being the most critical element. Additions of Si, Al, or Ce were shown to extend the usefulness of Fe-Cr-Ni alloys.

  19. Corrosion of ferritic-martensitic steels and nickel-based alloys in supercritical water

    NASA Astrophysics Data System (ADS)

    Ren, Xiaowei

    The corrosion behavior of ferritic/martensitic (F/M) steels and Ni-based alloys in supercritical water (SCW) has been studied due to their potential applications in future nuclear reactor systems, fossil fuel power plants and waste treatment processes. 9˜12% chromium ferritic/martensitic steels exhibit good radiation resistance and stress corrosion cracking resistance. Ni-based alloys with an austenitic face-centered cubic (FCC) structure are designed to retain good mechanical strength and corrosion/oxidation resistance at elevated temperatures. Corrosion tests were carried out at three temperatures, 360°C, 500°C and 600°C, with two dissolved oxygen contents, 25 ppb and 2 ppm for up to 3000 hours. Alloys modified by grain refinement and reactive element addition were also investigated to determine their ability to improve the corrosion resistance in SCW. A duplex oxide structure was observed in the F/M steels after exposure to 25 ppb oxygen SCW, including an outer oxide layer with columnar magnetite grains and an inner oxide layer constituted of a mixture of spinel and ferrite phases in an equiaxed grain structure. An additional outermost hematite layer formed in the SCW-exposed samples when the oxygen content was increased to 2 ppm. Weight gain in the F/M steels increased with exposure temperatures and times, and followed parabolic growth kinetics in most of the samples. In Ni-based alloys after exposure to SCW, general corrosion and pitting corrosion were observed, and intergranular corrosion was found when exposed at 600°C due to formation of a local healing layer. The general oxide structure on the Ni-based alloys was characterized as NiO/Spinel/(CrxFe 1-x)2O3/(Fe,Ni). No change in oxidation mechanism was observed in crossing the critical point despite the large change in water properties. Corrosion resistance of the F/M steels was significantly improved by plasma-based yttrium surface treatment because of restrained outward diffusion of iron by the

  20. Effect of Specific Energy Input on Microstructure and Mechanical Properties of Nickel-Base Intermetallic Alloy Deposited by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Awasthi, Reena; Kumar, Santosh; Chandra, Kamlesh; Vishwanadh, B.; Kishore, R.; Viswanadham, C. S.; Srivastava, D.; Dey, G. K.

    2012-12-01

    This article describes the microstructural features and mechanical properties of nickel-base intermetallic alloy laser-clad layers on stainless steel-316 L substrate, with specific attention on the effect of laser-specific energy input (defined as the energy required per unit of the clad mass, kJ/g) on the microstructure and properties of the clad layer, keeping the other laser-cladding parameters same. Defect-free clad layers were observed, in which various solidified zones could be distinguished: planar crystallization near the substrate/clad interface, followed by cellular and dendritic morphology towards the surface of the clad layer. The clad layers were characterized by the presence of a hard molybdenum-rich hexagonal close-packed (hcp) intermetallic Laves phase dispersed in a relatively softer face-centered cubic (fcc) gamma solid solution or a fine lamellar eutectic phase mixture of an intermetallic Laves phase and gamma solid solution. The microstructure and properties of the clad layers showed a strong correlation with the laser-specific energy input. As the specific energy input increased, the dilution of the clad layer increased and the microstructure changed from a hypereutectic structure (with a compact dispersion of characteristic primary hard intermetallic Laves phase in eutectic phase mixture) to near eutectic or hypoeutectic structure (with reduced fraction of primary hard intermetallic Laves phase) with a corresponding decrease in the clad layer hardness.

  1. 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.

  2. Lubricating Properties of Ceramic-Bonded Calcium Fluoride Coatings on Nickel-Base Alloys from 75 to 1900 deg F

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.

    1962-01-01

    The endurance life and the friction coefficient of ceramic-bonded calcium fluoride (CaF2) coatings on nickel-base alloys were determined at temperatures from 75 F to 1900 F. The specimen configuration consisted of a hemispherical rider (3/16-in. rad.) sliding against the flat surface of a rotating disk. Increasing the ambient temperature (up to 1500 F) or the sliding velocity generally reduced the friction coefficient and improved coating life. Base-metal selection was critical above 1500 F. For instance, cast Inconel sliding against coated Inconel X was lubricated effectively to 1500 F, but at 1600 F severe blistering of the coatings occurred. However, good lubrication and adherence were obtained for Rene 41 sliding against coated Rene 41 at temperatures up to 1900 F; no blisters developed, coating wear life was fairly good, and the rider wear rate was significantly lower than for the unlubricated metals. Friction coefficients were 0.12 at 1500 F, 0.15 at 1700 F, and 0.17 at 1800 F and 1900 F. Because of its ready availability, Inconel X appears to be the preferred substrate alloy for applications in which the temperature does not exceed 1500 F. Rene 41 would have to be used in applications involving higher temperatures. Improved coating life was derived by either preoxidizing the substrate metals prior to the coating application or by applying a very thin (less than 0.0002 in.) burnished and sintered overlay to the surface of the coating. Preoxidation did not affect the friction coefficient. The overlay generally resulted in a higher friction coefficient than that obtained without the overlay. The combination of both modifications resulted in longer coating life and in friction coefficients intermediate between those obtained with either modification alone.

  3. Transient liquid phase bonding of titanium-, iron- and nickel-based alloys

    NASA Astrophysics Data System (ADS)

    Rahman, A. H. M. Esfakur

    The operating temperature of land-based gas turbines and jet engines are ever-increasing to increase the efficiency, decrease the emissions and minimize the cost. Within the engines, complex-shaped parts experience extreme temperature, fatigue and corrosion conditions. Ti-based, Ni-based and Fe-based alloys are commonly used in gas turbines and jet engines depending on the temperatures of different sections. Although those alloys have superior mechanical, high temperature and corrosion properties, severe operating conditions cause fast degradation and failure of the components. Repair of these components could reduce lifecycle costs. Unfortunately, conventional fusion welding is not very attractive, because Ti reacts very easily with oxygen and nitrogen at high temperatures, Ni-based superalloys show heat affected zone (HAZ) cracking, and stainless steels show intergranular corrosion and knife-line attack. On the other hand, transient liquid phase (TLP) bonding method has been considered as preferred joining method for those types of alloys. During the initial phase of the current work commercially pure Ti, Fe and Ni were diffusion bonded using commercially available interlayer materials. Commercially pure Ti (Ti-grade 2) has been diffusion bonded using silver and copper interlayers and without any interlayer. With a silver (Ag) interlayer, different intermetallics (AgTi, AgTi2) appeared in the joint centerline microstructure. While with a Cu interlayer eutectic mixtures and Ti-Cu solid solutions appeared in the joint centerline. The maximum tensile strengths achieved were 160 MPa, 502 MPa, and 382 MPa when Ag, Cu and no interlayers were used, respectively. Commercially pure Fe (cp-Fe) was diffusion bonded using Cu (25 m) and Au-12Ge eutectic interlayer (100 microm). Cu diffused predominantly along austenite grain boundaries in all bonding conditions. Residual interlayers appeared at lower bonding temperature and time, however, voids were observed in the joint

  4. High temperature corrosion of a nickel base alloy by helium impurities

    NASA Astrophysics Data System (ADS)

    Rouillard, F.; Cabet, C.; Wolski, K.; Terlain, A.; Tabarant, M.; Pijolat, M.; Valdivieso, F.

    2007-05-01

    High temperature corrosion properties of Haynes 230 were investigated in a purposely-designed facility under a typical very high temperature reactor (VHTR) impure helium medium. The study was focused on the surface oxide scale formation and its stability at about 1223 K. The alloy developed a Mn/Cr rich oxide layer on its surface under impure helium at 1173 K. Nevertheless, a deleterious reaction destructing the chromium oxide was evidenced above a critical temperature, TA. Reagents and products of this last reaction were investigated.

  5. Tensile Deformation of a Nickel-base Alloy at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Roy, Ajit K.; Venkatesh, Anand; Marthandam, Vikram; Ghosh, Arindam

    2008-08-01

    The results of tensile testing involving Waspaloy indicate that the failure strain was gradually reduced at temperatures ranging between ambient and 300 °C. Further, serrations were observed in the engineering stress versus strain diagrams in the temperature range of 300-600 °C. The reduced failure strain and the formation of serrations in these temperature regimes could be the result of dynamic strain aging of this alloy. The extent of work hardening due to plastic deformation was reduced at temperatures above 300 °C. A combination of ductile and intergranular brittle failures was seen at temperatures above 600 °C. γ' was detected at all tested temperatures.

  6. Rupture Strength of Several Nickel-base Alloys in Sheet Form

    NASA Technical Reports Server (NTRS)

    Dance, James H; Clauss, Francis J

    1957-01-01

    The 100-hour rupture strengths of Inconel X, Inconel 700, Incoloy 901, Refractaloy 26, and R-235 at 1200 and 1350 F. in both the annealed and heat-treated conditions were determined. Inconel 700 had the highest rupture strength at both temperatures; Incoloy 901 was second strongest at 1200 F, and R-235 second strongest at 1350 F. With the exception of Incoloy 901, ductility was low. Photomicrographs show that fractures are through the grain boundaries. Results are compared with published data for other sheet alloys and bar stock.

  7. Laser cladding of nickel-based alloy coatings on copper substrates

    NASA Astrophysics Data System (ADS)

    Balu, Prabu; Rea, Edward; Deng, Justin

    2015-07-01

    The wear resistance of high-value copper components used in the metal casting, automotive, aerospace and electrical equipment industries can be improved by applying nickel (Ni)-based coatings through laser cladding. A high-power diode laser array providing continuous power levels up to 10 kilowatts with beam-shaping optics providing a rectangular focal region of various dimensions was used to deposit Ni-based alloy coatings with controlled thickness ranging from 0.3 mm to 1.6 mm in a single pass on copper (Cu) substrates. Slotted powder feeding plates with various discrete widths delivered uniform streams of powdered metal particles entrained in a carrier gas, matching the selected focal spot dimensions. To enhance laser beam coupling with the substrate and to avoid defects such as cracks, delamination and porosity, Cu substrates were preheated to a temperature of 300°C. The effect of heat input on microstructure of the cladding and extent of the heat-affected zone (HAZ) was evaluated using optical microscopy and scanning electron microscopy. Excessive heat input with longer interaction time increased dilution, porosity and expanded HAZ that significantly reduced the hardness of both the clad and the Cu substrates. Average microhardness of the Ni-C-B-Si-W alloy coating was 572 HV, which was almost 7 times greater than the hardness of the Cu substrate (84 HV).

  8. Transient liquid phase bonding of titanium-, iron- and nickel-based alloys

    NASA Astrophysics Data System (ADS)

    Rahman, A. H. M. Esfakur

    The operating temperature of land-based gas turbines and jet engines are ever-increasing to increase the efficiency, decrease the emissions and minimize the cost. Within the engines, complex-shaped parts experience extreme temperature, fatigue and corrosion conditions. Ti-based, Ni-based and Fe-based alloys are commonly used in gas turbines and jet engines depending on the temperatures of different sections. Although those alloys have superior mechanical, high temperature and corrosion properties, severe operating conditions cause fast degradation and failure of the components. Repair of these components could reduce lifecycle costs. Unfortunately, conventional fusion welding is not very attractive, because Ti reacts very easily with oxygen and nitrogen at high temperatures, Ni-based superalloys show heat affected zone (HAZ) cracking, and stainless steels show intergranular corrosion and knife-line attack. On the other hand, transient liquid phase (TLP) bonding method has been considered as preferred joining method for those types of alloys. During the initial phase of the current work commercially pure Ti, Fe and Ni were diffusion bonded using commercially available interlayer materials. Commercially pure Ti (Ti-grade 2) has been diffusion bonded using silver and copper interlayers and without any interlayer. With a silver (Ag) interlayer, different intermetallics (AgTi, AgTi2) appeared in the joint centerline microstructure. While with a Cu interlayer eutectic mixtures and Ti-Cu solid solutions appeared in the joint centerline. The maximum tensile strengths achieved were 160 MPa, 502 MPa, and 382 MPa when Ag, Cu and no interlayers were used, respectively. Commercially pure Fe (cp-Fe) was diffusion bonded using Cu (25 m) and Au-12Ge eutectic interlayer (100 microm). Cu diffused predominantly along austenite grain boundaries in all bonding conditions. Residual interlayers appeared at lower bonding temperature and time, however, voids were observed in the joint

  9. Metallographic examination of TD-nickel base alloys. [thermal and chemical etching technique evaluation

    NASA Technical Reports Server (NTRS)

    Kane, R. D.; Petrovic, J. J.; Ebert, L. J.

    1975-01-01

    Techniques are evaluated for chemical, electrochemical, and thermal etching of thoria dispersed (TD) nickel alloys. An electrochemical etch is described which yielded good results only for large grain sizes of TD-nickel. Two types of thermal etches are assessed for TD-nickel: an oxidation etch and vacuum annealing of a polished specimen to produce an etch. It is shown that the first etch was somewhat dependent on sample orientation with respect to the processing direction, the second technique was not sensitive to specimen orientation or grain size, and neither method appear to alter the innate grain structure when the materials were fully annealed prior to etching. An electrochemical etch is described which was used to observe the microstructures in TD-NiCr, and a thermal-oxidation etch is shown to produce better detail of grain boundaries and to have excellent etching behavior over the entire range of grain sizes of the sample.

  10. Fiber laser cladding of nickel-based alloy on cast iron

    NASA Astrophysics Data System (ADS)

    Arias-González, F.; del Val, J.; Comesaña, R.; Penide, J.; Lusquiños, F.; Quintero, F.; Riveiro, A.; Boutinguiza, M.; Pou, J.

    2016-06-01

    Gray cast iron is a ferrous alloy characterized by a carbon-rich phase in form of lamellar graphite in an iron matrix while ductile cast iron presents a carbon-rich phase in form of spheroidal graphite. Graphite presents a higher laser beam absorption than iron matrix and its morphology has also a strong influence on thermal conductivity of the material. The laser cladding process of cast iron is complicated by its heterogeneous microstructure which generates non-homogeneous thermal fields. In this research work, a comparison between different types of cast iron substrates (with different graphite morphology) has been carried out to analyze its impact on the process results. A fiber laser was used to generate a NiCrBSi coating over flat substrates of gray cast iron (EN-GJL-250) and nodular cast iron (EN-GJS-400-15). The relationship between processing parameters (laser irradiance and scanning speed) and geometry of a single laser track was examined. Moreover, microstructure and composition were studied by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and X-Ray Diffraction (XRD). The hardness and elastic modulus were analyzed by means of micro- and nanoindentation. A hardfacing coating was generated by fiber laser cladding. Suitable processing parameters to generate the Ni-based alloy coating were determined. For the same processing parameters, gray cast iron samples present higher dilution than cast iron samples. The elastic modulus is similar for the coating and the substrate, while the Ni-based coating obtained presents a significantly superior hardness than cast iron.

  11. The Crystal Structure at Room Temperature of Six Cast Heat-Resisting Alloys

    NASA Technical Reports Server (NTRS)

    Rosenbaum, Burt M.

    1947-01-01

    The crystal structures of alloys 61, X-40,X-50, 422-19, 6059, and Vitallium, derived from x-ray diffraction, are discussed. The alloys have been, or are being considered for use in gas turbine applications. The predominant phase was a solid solution of the face centered cubic type of the principal constituent elements.The lattice parameters were found to be between 3.5525 and 3.5662.

  12. Physical and welding metallurgy of Gd-enriched austenitic alloys for spent nuclear fuel applications. Part II, nickel base alloys.

    SciTech Connect

    Mizia, Ronald E.; Michael, Joseph Richard; Williams, David Brian; Dupont, John Neuman; Robino, Charles Victor

    2004-06-01

    The physical and welding a metallurgy of gadolinium- (Gd-) enriched Ni-based alloys has been examined using a combination of differential thermal analysis, hot ductility testing. Varestraint testing, and various microstructural characterization techniques. Three different matrix compositions were chosen that were similar to commercial Ni-Cr-Mo base alloys (UNS N06455, N06022, and N06059). A ternary Ni-Cr-Gd alloy was also examined. The Gd level of each alloy was {approx}2 wt-%. All the alloys initiated solidification by formation of primary austenite and terminated solidification by a Liquid {gamma} + Ni{sub 5}Gd eutectic-type reaction at {approx}1270 C. The solidification temperature ranges of the alloys varied from {approx}100 to 130 C (depending on alloy composition). This is a substantial reduction compared to the solidification temperature range to Gd-enriched stainless steels (360 to 400 C) that terminate solidification by a peritectic reaction at {approx}1060 C. The higher-temperature eutectic reaction that occurs in the Ni-based alloys is accompanied by significant improvements in hot ductility and solidification cracking resistance. The results of this research demonstrate that Gd-enriched Ni-based alloys are excellent candidate materials for nuclear criticality control in spent nuclear fuel storage applications that require production and fabrication of large amounts of material through conventional ingot metallurgy and fusion welding techniques.

  13. Chemical reactivity of nickel and nickel-based alloys with a SiAlON ceramic

    SciTech Connect

    Vleugels, J.; Van Der Biest, O.

    1995-11-01

    At the high cutting speeds typical for machining with ceramics and the concomitant high temperatures generated at the cutting edge and the rake face of the tool, chemical interaction between tool and workpiece material becomes the predominant mode of tool wear. To obtain more information concerning this chemical interaction mechanism, the chemical interaction of a {beta}{prime}-O{prime} SiAlON ceramic with pure nickel, Inconel 600, and Nimonic 105 is studied. The chemical reactivity was assessed by studying ceramic-alloy interaction couples after exposure at elevated temperatures (1,100--1,200 C) for times long enough to be able to characterize the interaction layer. At 1,200 C, the {beta}{prime}-O{prime} SiAlON ceramic dissociates in contact with pure nickel. Silicon from the dissociation of the ceramic dissolves and diffuses into the nickel, whereas Al and O form Al{sub 2}O{sub 3} particles. At the interface, a nitrogen pressure is built up. Inconel 600 is very reactive with the SiAlON ceramic, with the formation of molten silicides at 1,200 C. Cr{sub 3}Ni{sub 2}Si, Al{sub 2}O{sub 3}, and Ni{sub 31}Si{sub 12} are the major reaction products. The reactivity of Nimonic 105 is less than that of pure nickel because of the formation of a continuous protective TiN layer at the ceramic-metal interface.

  14. Structural evaluation of a nickel base super alloy metal foam via NDE and finite element

    NASA Astrophysics Data System (ADS)

    Abdul-Aziz, Ali; Abumeri, G.; Garg, Mohit; Young, P. G.

    2008-03-01

    Cellular materials are known to be useful in the application of designing light but stiff structures. This applies to various components used in various industries such as rotorcraft blades, car bodies or portable electronic devices. Structural application of the metal foam is typically confined to light weight sandwich panels, made up of thin solid face sheets and a metallic foam core. The resulting high-stiffness structure is lighter than that constructed only out of the solid metal material. The face sheets carry the applied in-plane and bending loads and the role of the foam core is separate the face sheets to carry some of the shear stresses, while remaining integral with the face sheet. Many challenges relating to the fabrication and testing of these metal foam panels continue to exist due to some mechanical properties falling short of their theoretical potential. Hence in this study, a detailed three dimensional foam structure is generated using series of 2D Computer Tomography (CT) scans, on Haynes 25 metal foam. Series of the 2D images are utilized to construct a high precision solid model including all the fine details within the metal foam as detected by the CT scanning technique. Subsequently, a finite element analysis is then performed on an as fabricated metal foam microstructures to evaluate the foam structural durability and behavior under tensile and compressive loading conditions. The analysis includes a progressive failure analysis (PFA) using GENOA code to further assess the damage initiation, propagation, and failure. The open cell metal foam material is a cobalt-nickel-chromium-tungsten alloy that combines excellent high-temperature strength with good resistance to oxidizing environments up to 1800 °F (980 °C) for prolonged exposures. The foam is formed by a powder metallurgy process with an approximate 100 pores per inch (PPI).

  15. The Corrosion and Corrosion Fatigue Behavior of Nickel Based Alloy Weld Overlay and Coextruded Claddings

    NASA Astrophysics Data System (ADS)

    Stockdale, Andrew

    The use of low NOx boilers in coal fired power plants has resulted in sulfidizing corrosive conditions within the boilers and a reduction in the service lifetime of the waterwall tubes. As a solution to this problem, Ni-based weld overlays are used to provide the necessary corrosion resistance however; they are susceptible to corrosion fatigue. There are several metallurgical factors which give rise to corrosion fatigue that are associated with the localized melting and solidification of the weld overlay process. Coextruded coatings offer the potential for improved corrosion fatigue resistance since coextrusion is a solid state coating process. The corrosion and corrosion fatigue behavior of alloy 622 weld overlays and coextruded claddings was investigated using a Gleeble thermo-mechanical simulator retrofitted with a retort. The experiments were conducted at a constant temperature of 600°C using a simulated combustion gas of N2-10%CO-5%CO2-0.12%H 2S. An alternating stress profile was used with a minimum tensile stress of 0 MPa and a maximum tensile stress of 300 MPa (ten minute fatigue cycles). The results have demonstrated that the Gleeble can be used to successfully simulate the known corrosion fatigue cracking mechanism of Ni-based weld overlays in service. Multilayer corrosion scales developed on each of the claddings that consisted of inner and outer corrosion layers. The scales formed by the outward diffusion of cations and the inward diffusion of sulfur and oxygen anions. The corrosion fatigue behavior was influenced by the surface finish and the crack interactions. The initiation of a large number of corrosion fatigue cracks was not necessarily detrimental to the corrosion fatigue resistance. Finally, the as-received coextruded cladding exhibited the best corrosion fatigue resistance.

  16. Enhanced Heat Resistance of Al-Cu-Mg Alloy by a Combination of Pre-stretching and Underaging

    NASA Astrophysics Data System (ADS)

    Wang, Xiaohu; Liu, Zhiyi; Bai, Song; Lin, Lianghua; Ye, Chengwu; Wang, Heng

    2016-06-01

    Enhanced heat resistance of Al-Cu-Mg alloy by employing a combined effect of pre-stretching and underaging has been characterized by thermal exposure, tensile testing, transmission electron microscopy (TEM) examination, and quantitative analysis. Tensile testing results showed that the samples subjected to both pre-stretching and underaging processing, presented a high tensile strength up to 440 MPa after thermal exposure at 200 °C for 500 h. This suggests that the long-time application temperature of Al-Cu-Mg alloys, which were normally applied at elevated temperature below 150 °C or even below 100 °C, can be raised to 200 °C by employing a combined effect of pre-stretching and underaging. TEM results showed that a fine and a narrow size distribution range of S' phase was formed by the combined processing of pre-stretching and underaging, as compared to that without pre-stretching. Quantitative analysis results indicated that this narrow range of size distribution greatly reduced the growth rate of S' phase during thermal exposure. It is suggested that this effect was ascribed to the Ostwald ripening mechanism.

  17. Development of improved low-strain creep strength in Cabot alloy R-41 sheet. [nickel base sheet alloy for reentry shielding

    NASA Technical Reports Server (NTRS)

    Rothman, M. F.

    1984-01-01

    The feasibility of improving the low-strain creep properties of a thin gauge nickel base sheet alloy through modified heat treatment or through development of a preferred crystal-lographic texture was investigated. The basic approach taken to improve the creep strength of the material by heat treatment was to increase grain size by raising the solution treatment temperature for the alloy to the range of 1420 K to 1475 K (2100 F to 2200 F). The key technical issue involved was maintenance of adequate tensile ductility following the solutioning of M6C primary carbides during the higher temperature solution treatment. The approach to improve creep properties by developing a sheet texture involved varying both annealing temperatures and the amount of prior cold work. Results identified a heat treatment for alloy R-14 sheet which yields a substantial creep-life advantage at temperatures above 1090 K (1500 F) when compared with material given the standard heat treatment. At the same time, this treatment provides reasonable tensile ductility over the entire temperature range of interest. The mechanical properties of the material given the new heat treatment are compared with those for material given the standard heat treatment. Attempts to improve creep strength by developing a sheet texture were unsuccessful.

  18. Selection and Evaluation of Heat-Resistant Alloys for Planar SOFC Interconnect Applications

    SciTech Connect

    Yang, Z Gary; Weil, K. Scott; Paxton, Dean M.; Stevenson, Jeffry W.

    2002-11-21

    Over the past several years, the steady reduction in SOFC operating temperatures to the intermediate range of 700~850oC [1] has made it feasible for lanthanum chromite to be supplanted by metals or alloys as the interconnect materials. Compared to doped lanthanum chromite, metals or alloys offer significantly lower raw material and fabrication costs. However, to be a durable and reliable, a metal or alloy has to satisfy several functional requirements specific to the interconnect under SOFC operating conditions. Specifically, the interconnect metal or alloy should possess the following properties: (i) Good surface stability (resistance to oxidation, hot corrosion, and carburization) in both cathodic (air) and anodic (fuel) atmospheres; (ii) Thermal expansion matching to the ceramic PEN (positive cathode-electrolyte-negative anode) and seal materials (as least for a rigid seal design); (iii) High electrical conductivity through both the bulk material and in-situ formed oxide scales; (iv) Bulk and interfacial thermal mechanical reliability and durability at the operating temperature; (v) Compatibility with other materials in contact with interconnects such as seals and electrical contact materials.

  19. Effect of the Fine-Grained Structure on the Fatigue Properties of the Heat-Resistant Nickel-Iron Alloy Inconel 718

    NASA Astrophysics Data System (ADS)

    Mukhtarov, Sh. Kh.; Shakhov, R. V.

    2015-10-01

    It is well known that ultrafine-grained nickel alloys with average grain sizes d = 0.1-1 μm possess improved hot workability and can be used for superplastic forming or rolling. However, microstructure refinement can worsen some performance characteristics of the alloy, for example, heat-resistant or fatigue properties. In the present work, fatigue characteristics of the fine-grained alloy Inconel 718 are investigated. Ultrafine-grained alloys with average grain sizes d = 0.1-1 μm were manufactured by multiple forging with stage-by-stage deformation temperature decrease. During standard heat treatment of the alloy performed to obtain the desired properties, the γ-grain size was controlled by precipitations of δ-phase particles along the boundaries. Results of low-cycle fatigue tests of the fine-grained alloy at room and elevated temperatures are compared with the properties of the coarse-grained alloy.

  20. Influence of surface modifications on pitting corrosion behavior of nickel-base alloy 718. Part 1: Effect of machine hammer peening

    SciTech Connect

    2013-12-01

    The effect of surface modifications induced by machine hammer peening on pitting corrosion behavior of nickel-base alloy 718 in a 3.5 wt.% NaCl solution is investigated. Severe work hardening and high compressive residual stress are generated with surface smoothing and microstructure evolution in terms of formation of nano-grains and nano-twins in the near surface region after machine hammer peening. Electrochemical tests results show that machine hammer peening has a beneficial influence on the corrosion resistance, indicated by a significant increase of the critical pitting potential (+134 mV) accompanied with lower corrosion current density and higher polarization resistance.

  1. 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.

  2. 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.

  3. Changes In Mechanical Properties Of Heat Resisting Alloy For A Satellite Propulsion System After A Nitriding Process

    NASA Astrophysics Data System (ADS)

    Kagawa, Hideshi; Fujii, Go; Kajiwara, Kenichi; Kuroda, Daisuke; Suzuki, Takuya; Yamabe-Mitarai, Yoko; Murakami, Hideyuki; Ono, Yoshinori

    2012-07-01

    Haynes25 (L-605) is a common heat resistant alloy used in mono-propellant structures and screen materials for catalyst beds. The lifetime requirements for thrusters have expanded dramatically after studies conducted in the 1970s on mono-propellant materials used to extend the service life. The material design had long remained unchanged, and the L-605 was still used as thruster material due to its good heritage. However, some important incidents involving degradation were found during the test-unit break-up inspection following the thruster life tests. The Japanese research team focused on the L-605 degradations found on the catalyst bed screen mesh used for mono-propellant thruster and analysed the surface of the wire material and the cross- section of the wire screen mesh used in the life tests. The investigation showed that the degradation was caused by nitriding L-605 component elements. The team suggested that the brittle fracture was attributable to tungsten (W) carbides, which formed primarily in the grain boundaries, and chromium (Cr) nitride, which formed mainly in the parts in contact with the hot firing gas. The team also suggested the installation of a platinum coating on the material surface as a countermeasure L-605 nitric degradation. Inconel 625 is now selected as a mono-propellant structure material due to its marginal raw material characters and cost. The team believes that Inconel 625 does not form W carbides since it contains no tungsten component, but does contain Cr and Fe, which form nitrides easily. Therefore, the team agreed that for the Inconel 625, there was a need to evaluate changes in the microstructure and mechanical properties following exposure to hot nitrogen gases. This paper will describe these changes of Inconel 625.

  4. Brushing-Induced Surface Roughness of Two Nickel Based Alloys and a Titanium Based Alloy: A Comparative Study - In Vitro Study

    PubMed Central

    Acharya, B L Guruprasanna; Nadiger, Ramesh; Shetty, Bharathraj; Gururaj, G; Kumar, K Naveen; Darshan, D D

    2014-01-01

    be given to the selection of the toothbrushes and toothpastes with the medium abrasives in patients with these restorations. How to cite the article: Acharya BL, Nadiger R, Shetty B, Gururaj G, Kumar KN, Darshan DD. Brushing induced surface roughness of two nickel based alloys and a titanium based alloy: A comparative study - In vitro study. J Int Oral Health 2014;6(3):36-49. PMID:25083031

  5. Synthesis and characterization of binder-free Cr3C2 coatings on nickel-based alloys for molten fluoride salt corrosion resistance

    NASA Astrophysics Data System (ADS)

    Brupbacher, Michael C.; Zhang, Dajie; Buchta, William M.; Graybeal, Mark L.; Rhim, Yo-Rhin; Nagle, Dennis C.; Spicer, James B.

    2015-06-01

    Under various conditions, chromium carbides appear to be relatively stable in the presence of molten fluoride salts and this suggests that their use in corrosion resistant coatings for fluoride salt environments could be beneficial. One method for producing these coatings is the carburization of sprayed Cr coatings using methane-containing gaseous precursors. This process has been investigated for the synthesis of binder-free chromium carbide coatings on nickel-based alloy substrates for molten fluoride salt corrosion resistance. The effects of the carburization process on coating microstructure have been characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) in conjunction with energy dispersive spectroscopy (EDS). Both plasma-sprayed and cold-sprayed Cr coatings have been successfully converted to Cr3C2, with the mechanism of conversion being strongly influenced by the initial porosity in the as-deposited coatings.

  6. Corrosion of austenitic stainless steels and nickel-base alloys in supercritical water and novel control methods

    SciTech Connect

    Tan, Lizhen; Allen, Todd R.; Yang, Ying

    2012-01-01

    This chapter contains sections titled: (1) Introduction; (2) Thermodynamics of Alloy Oxidation; (3) Corrosion of Austenitic Stainless Steels and Ni-Base Alloys in SCW; (4) Novel Corrosion Control Methods; (5) Factors Influencing Corrosion; (6) Summary; and (7) References.

  7. 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

  8. Corrosion behavior of experimental and commercial nickel-base alloys in HCl and HCl containing Fe3+

    SciTech Connect

    Holcomb, G.R.; Covino, B.S., Jr.; Bullard, S.J.; Ziomek-Moroz, M.

    2006-03-01

    The effects of ferric ions on the corrosion resistance and electrochemical behavior of a series of Ni-based alloys in 20% HCl at 30ºC were investigated. The alloys studied were those prepared by the Albany Research Center (ARC), alloys J5, J12, J13, and those sold commercially, alloys 22, 242, 276, and 2000. Tests included mass loss, potentiodynamic polarization, and linear polarization.

  9. 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

  10. Intergranular tellurium cracking of nickel-based alloys in molten Li, Be, Th, U/F salt mixture

    NASA Astrophysics Data System (ADS)

    Ignatiev, Victor; Surenkov, Alexander; Gnidoy, Ivan; Kulakov, Alexander; Uglov, Vadim; Vasiliev, Alexander; Presniakov, Mikhail

    2013-09-01

    In Russia, R&D on Molten Salt Reactor (MSR) are concentrated now on fast/intermediate spectrum concepts which were recognized as long term alternative to solid fueled fast reactors due to their attractive features: strong negative feedback coefficients, easy in-service inspection, and simplified fuel cycle. For high-temperature MSR corrosion of the metallic container alloy in primary circuit is the primary concern. Key problem receiving current attention include surface fissures in Ni-based alloys probably arising from fission product tellurium attack. This paper summarizes results of corrosion tests conducted recently to study effect of oxidation state in selected fuel salt on tellurium attack and to develop means of controlling tellurium cracking in the special Ni-based alloys recently developed for molten salt actinide recycler and tranforming (MOSART) system. Tellurium corrosion of Ni-based alloys was tested at temperatures up to 750 °C in stressed and unloaded conditions in molten LiF-BeF2 salt mixture fueled by about 20 mol% of ThF4 and 2 mol% of UF4 at different [U(IV)]/[U(III)] ratios: 0.7, 4, 20, 100 and 500. Following Ni-based alloys (in mass%): HN80М-VI (Mo—12, Cr—7.6, Nb—1.5), HN80МТY (Mo—13, Cr—6.8, Al—1.1, Ti—0.9), HN80МТW (Mo—9.4, Cr—7.0, Ti—1.7, W—5.5) and ЕМ-721 (W—25.2, Cr—5.7, Ti—0.17) were used for the study in the corrosion facility. If the redox state the fuel salt is characterized by uranium ratio [U(IV)]/[U(III)] < 1 the alloys' specimens get a more negative stationary electrode potential than equilibrium electrode potentials of some uranium intermetallic compounds and alloys with nickel and molybdenum. This leads to spontaneous behavior of alloy formation processes on the specimens' surface and further diffusion of uranium deep into the metallic phase. As consequence of this films of intermetallic compounds and alloys of nickel, molybdenum, tungsten with uranium are formed on the alloys specimens' surface

  11. Creep and tensile properties of several oxide-dispersion-strengthened nickel-base alloys at 1365 K

    NASA Technical Reports Server (NTRS)

    Wittenberger, J. D.

    1977-01-01

    The tensile properties at room temperature and at 1365 K and the tensile creep properties at low strain rates at 1365 K were measured for several oxide-dispersion-strengthened (ODS) alloys. The alloys examined included ODS Ni, ODS Ni-20Cr, and ODS Ni-16Cr-Al. Metallography of creep tested, large grain size ODS alloys indicated that creep of these alloys is an inhomogeneous process. All alloys appear to possess a threshold stress for creep. This threshold stress is believed to be associated with diffusional creep in the large grain size ODS alloys and normal dislocation motion in perfect single crystal (without transverse low angle boundaries) ODS alloys. Threshold stresses for large grain size ODS Ni-20Cr and Ni-16Cr-Al type alloys are dependent on the grain aspect ratio. Because of the deleterious effect of prior creep on room temperature mechanical properties of large grain size ODS alloys, it is speculated that the threshold stress may be the design limiting creep strength property.

  12. Development of Simultaneous Corrosion Barrier and Optimized Microstructure in FeCrAl Heat-Resistant Alloy for Energy Applications. Part 1: The Protective Scale

    NASA Astrophysics Data System (ADS)

    Pimentel, G.; Aranda, M. M.; Chao, J.; González-Carrasco, J. L.; Capdevila, C.

    2015-09-01

    Coarse-grained Fe-based oxide dispersion-strengthened (ODS) steels are a class of advanced materials for combined cycle gas turbine systems to deal with operating temperatures and pressures of around 1100°C and 15-30 bar in aggressive environments, which would increase biomass energy conversion efficiencies up to 45% and above. This two-part paper reports the possibility of the development of simultaneous corrosion barrier and optimized microstructure in a FeCrAl heat-resistant alloy for energy applications. The first part reports the mechanism of generating a dense, self-healing α-alumina layer by thermal oxidation, during a heat treatment that leads to a coarse-grained microstructure with a potential value for high-temperature creep resistance in a FeCrAl ODS ferritic alloy, which will be described in more detail in the second part.

  13. Pacific Northwest National Laboratory Investigation of the Stress Corrosion Cracking in Nickel-Base Alloys, Volume 2

    SciTech Connect

    Bruemmer, Stephen M.; Toloczko, Mychailo B.; Olszta, Matthew J.

    2012-03-01

    The objective of this program is to evaluate the primary water stress corrosion cracking (PWSCC) susceptibility of high chromium alloy 690 and its weld metals, establish quantitative measurements of crack-growth rates and determine relationships among cracking susceptibility, environmental conditions and metallurgical characteristics. Stress-corrosion, crack-growth rates have been determined for 12 alloy 690 specimens, 11 alloy 152/52/52M weld metal specimens, 4 alloy 52M/182 overlay specimens and 2 alloy 52M/82 inlay specimens in simulated PWR primary water environments. The alloy 690 test materials included three different heats of extruded control-rod-drive mechanism (CRDM) tubing with variations in the initial material condition and degree of cold work for one heat. Two cold-rolled (CR) alloy 690 plate heats were also obtained and evaluated enabling comparisons to the CR CRDM materials. Weld metal, overlay and inlay specimens were machined from industry mock ups to provide plant-representative materials for testing. Specimens have been tested for one alloy 152 weld, two alloy 52 welds and three alloy 52M welds. The overlay and inlay specimens were prepared to propagate stress-corrosion cracks from the alloy 182 or 82 material into the more resistant alloy 52M. In all cases, crack extension was monitored in situ by direct current potential drop (DCPD) with length resolution of about +1 µm making it possible to measure extremely low growth rates approaching 5x10-10 mm/s. Most SCC tests were performed at 325-360°C with hydrogen concentrations from 11-29 cc/kg; however, environmental conditions were modified during a few experiments to evaluate the influence of temperature, water chemistry or electrochemical potential on propagation rates. In addition, low-temperature (~50°C) cracking behavior was examined for selected alloy 690 and weld metal specimens. Extensive characterizations have been performed on material microstructures and stress-corrosion cracks by

  14. Silver and lanthanum as effective modifiers in trace determination of cadmium in nickel-base alloys by electrothermal atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Tsai, Suh-Jen Jane; Chang, Li-Lin; Chang, Shiow-Ing

    1997-01-01

    Trace cadmium in nickel-base superalloys was determined by a stabilized temperature platform furnace using atomic absorption spectrometry with a deuterium arc background correction system. The volatility of cadmium limits the pyrolysis temperature. This prevents the removal of the interfering alloy matrix at the thermal pretreatment step. Hence, an enormously high background signal has been observed. Chemical modifiers including ammonium citrate, 1-(2-pyridylazo)-naphthol, 4-(2pyridylazo)resorcinol, 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol, Triton-X 100, EDTA, potassium nitrate, palladium nitrate, magnesium nitrate, aluminum chloride, ammonium dihydrogen phosphate, lanthanum oxide, lanthanum chloride and silver nitrate have been studied. Matrix interferences were effectively reduced by silver and lanthanum. The 100-300°C increase in the pyrolysis temperature effectively reduced the non-specific absorption from the alloy matrix. Interferences from foreign ions were also investigated. The merit of the proposed method was increased by the excellent agreement between the certified and the experimental values of Cd in the standard reference material, IN100, and the recovery obtained (100-104%). The precision of six successive replicate measurements was 4.9% with Ag modifier and 2.5% with La modifier, respectively. The results of analysing Tracealloy B were also satisfactory.

  15. Thermal fatigue of a heat-resistant Fe-0.45C-26Cr-33Ni-2Si-2Nb alloy

    NASA Astrophysics Data System (ADS)

    Oryshchenko, A. S.; Utkin, Yu. A.; Belyaeva, L. A.; Potapova, V. A.; Balakin, S. M.

    2011-03-01

    The thermal fatigue of a heat-resistant Fe-0.45C-26Cr-33Ni-2Si-2Nb alloy is studied during thermal cycling in the temperature range 50-900°C up to 1000 cycles. The alloy is investigated in the initial as-cast state and after isothermal annealing during 1000 h at a temperature of 800, 900, 1000, or 1100°C; these conditions imitate the temperature conditions of operation and the structural state of various layers in a reaction pipe in the radiant furnace coils of ethylene production installations. After isothermal annealing, the thermal fatigue life of the alloy is found to decrease by a factor of 1.7-1.2 as compared to the initial as-cast state. It is shown that isothermal annealing and subsequent thermal cycling lead to the formation of carbide precipitates of various sizes in the alloy structure that affect the thermal fatigue life of the alloy. Thermal fatigue cracks are shown to form and grow predominantly at the sites of accumulation of fine carbide precipitates. Coarse (>10 μm) precipitates retard crack growth, and cracks branch near such precipitates.

  16. Grinding as an approach to the production of high-strength, dispersion-strengthened nickel-base alloys

    NASA Technical Reports Server (NTRS)

    Orth, N. W.; Quatinetz, M.; Weeton, J. W.

    1970-01-01

    Mechanical process produces dispersion-strengthened metal alloys. Power surface contamination during milling is removed by a cleaning method that involves heating thin shapes or partially-compacted milled powder blends in hydrogen to carefully controlled temperature schedules.

  17. Oxidation behavior of nickel-base superalloys and High Strength Low Alloy (HSLA) steels at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Talekar, Anjali S.

    Alloy C-22 (UNS N06022) and High Strength Low Alloy (HSLA) steels are candidate materials for use in outer layer of waste storage packages and as rock bolts in the underground roof supports at Yucca Mountain nuclear waste repository respectively. Oxidation kinetics of three Ni-base Superalloys and two HSLA Steels, Split Set Friction Rock Stabilizers (SS-46) and Swellex Mn-24, have been determined by isothermal high temperature continuous measurement thermogravimetry at temperatures ranging between 600°C to 1100°C in pure oxygen atmosphere for predetermined periods of exposures (48 hours for the Superalloys and 100 hours for HSLA steels). The two other Ni-base Superalloys selected were Alloy-263 (UNS N07263) and Alloy-282. These are similar in their Cr composition to Alloy C-22 and have variations in the contents of other alloying elements namely Co and Mo. The alloys were selected for comparison of their oxidation resistance with C-22 as a baseline material. All three Superalloys are known chromia formers. All the superalloys were evaluated for determining their kinetic parameters and the activation energies for the superalloys were also calculated. The activation energy for the parabolic regime of Alloy-282 is found to be 232 kJ/mol. The slope of the curves on a plot of kp as a function of (1/T) show Alloy-282 to have better oxidation resistance up to 980°C and thereafter the rate constants are similar for all three alloys, but when activation energies over the whole temperature range are calculated, Alloy-263 shows the best average oxidation resistance. Surface characterization by means of microscopy as well as X-ray photoelectron spectroscopy showed the nature of oxides formed. Based on the kinetics and the characterization, proposed mechanisms for oxidation of these alloys at high temperatures are put forth. Temperature modulated thermogravimetry was used for studies on HSLA steels. The imposed sinusoidal temperature modulations on the isothermal temperature

  18. Application of powder metallurgy to an advanced-temperature nickel-base alloy, NASA-TRW 6-A

    NASA Technical Reports Server (NTRS)

    Freche, J. C.; Ashbrook, R. L.; Waters, W. J.

    1971-01-01

    Bar stock of the NASA-TRW 6-A alloy was made by prealloyed powder techniques and its properties evaluated over a range of temperatures. Room temperature ultimate tensile strength was 1894 MN/sq m (274 500 psi). The as-extruded powder product showed substantial improvements in strength over the cast alloy up to 649 C (1200 F) and superplasticity at 1093 C (2000 F). Both conventional and autoclave heat treatments were applied to the extruded powder product. The conventional heat treatment was effective in increasing rupture life at 649 and 704 C (1200 and 1300 F); the autoclave heat treatment, at 760 and 816 C (1400 and 1500 F).

  19. Intergranular Cracking Susceptibility of 2.25Cr Heat-Resistant Steels Depending on Alloying Elements and Impurities

    NASA Astrophysics Data System (ADS)

    Sung, Hyun Je; Heo, Nam Hoe; Kim, Sung-Joon

    2016-05-01

    The intergranular cracking susceptibility of 2.25Cr heat-resistant steels increases with increasing bulk phosphorus content. This is due to the increase in phosphorus segregation concentration of prior austenite grain boundaries (PAGBs) and the prior austenite grain boundary/carbide interfaces (GCIs) with increasing bulk phosphorus content. Moreover, the susceptibility is higher in tungsten-added steels than the molybdenum-added steel. This is attributed to the higher driving force for carbide formation of tungsten which causes more active carbide formation in the tungsten-added steel, the consequent absence of the repulsive segregation between carbon and phosphorus, and the final higher phosphorus segregation concentration at the PAGBs and the GCIs. Additionally, the absence of sulfur segregation at the PAGBs and the GCIs of the molybdenum-added steel, which arises from the repulsive segregation between carbon and sulfur, acts as an additional factor which lowers the intergranular cracking susceptibility.

  20. Effect of the pre-existing carbides on the grain boundary network during grain boundary engineering in a nickel based alloy

    SciTech Connect

    Liu, Tingguang; Xia, Shuang; Li, Hui; Zhou, Bangxin; Bai, Qin

    2014-05-01

    Grain boundary engineering was carried out on an aging-treated nickel based Alloy 690, which has precipitated carbides at grain boundaries. Electron backscatter diffraction technique was used to investigate the grain boundary networks. Results show that, compared with the solution-annealed samples, the aging-treated samples with pre-existing carbides at grain boundaries need longer duration or higher temperature during annealing after low-strain tensile deformation for forming high proportion of low-Σ coincidence site lattice grain boundaries (more than 75%). The reason is that the primary recrystallization is inhibited or retarded owing to that the pre-existing carbides are barriers to grain boundaries migration. - Highlights: • Study of GBE as function of pre-existing GB carbides, tensile strain and annealing • Recrystallization of GBE is inhibited or retarded by the pre-existing carbides. • Retained carbides after annealing show the original GB positions. • More than 80% of special GBs were formed after the modification of GBE processing. • Multiple twinning during recrystallization is the key process of GBE.

  1. Friction and wear of oxide-ceramic sliding against IN-718 nickel base alloy at 25 to 800 C in atmospheric air

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.; Deadmore, Daniel L.

    1989-01-01

    The friction and wear of oxide-ceramics sliding against the nickel base alloy IN-718 at 25 to 800 C were measured. The oxide materials tested were mullite (3Al2O3.2SiO2); lithium aluminum silicate (LiAlSi(x)O(y)); polycrystalline monolithic alpha alumina (alpha-Al2O3); single crystal alpha-Al2O3 (sapphire); zirconia (ZrO2); and silicon carbide (SiC) whisker-reinforced Al2O3 composites. At 25 C the mullite and zirconia had the lowest friction and the polycrystalline monolithic alumina had the lowest wear. At 800 C the Al2O3-8 vol/percent SiC whisker composite had the lowest friction and the Al2O3-25 vol/percent SiC composite had the lowest wear. The friction of the Al2O3-SiC whisker composites increased with increased whisker content while the wear decreased. In general, the wear-resistance of the ceramics improve with their hardness.

  2. Hydrogen adsorption and diffusion, and subcritical-crack growth in high strength steels and nickel base alloys

    NASA Technical Reports Server (NTRS)

    Wei, R. P.; Klier, K.; Simmons, G. W.; Chornet, E.

    1973-01-01

    Embrittlement, or the enhancement of crack growth by gaseous hydrogen in high strength alloys, is of primary interest in selecting alloys for various components in the space shuttle. Embrittlement is known to occur at hydrogen gas pressures ranging from fractions to several hundred atmospheres, and is most severe in the case of martensitic high strength steels. Kinetic information on subcritical crack growth in gaseous hydrogen is sparse at this time. Corroborative information on hydrogen adsorption and diffusion is inadequate to permit a clear determination of the rate controlling process and possible mechanism in hydrogen enhanced crack growth, and for estimating behavior over a range of temperatures and pressures. Therefore, coordinated studies of the kinetics of crack growth, and adsorption and diffusion of hydrogen, using identical materials, have been initiated. Comparable conditions of temperature and pressure will be used in the chemical and mechanical experiments. Inconel 718 alloy and 18Ni(200) maraging steel have been selected for these studies. Results from these studies are expected to provide not only a better understanding of the gaseous hydrogen embrittlement phenomenon itself, but also fundamental information on hydrogen adsorption and diffusion, and crack growth information that can be used directly for design.

  3. The role of intergranular chromium carbides on intergranular oxidation of nickel based alloys in pressurized water reactors primary water

    NASA Astrophysics Data System (ADS)

    Gaslain, F. O. M.; Le, H. T.; Duhamel, C.; Guerre, C.; Laghoutaris, P.

    2016-02-01

    Alloy 600 is used in pressurized water reactors (PWRs) but is susceptible to primary water stress corrosion cracking (PWSCC). Intergranular chromium carbides have been found beneficial to reduce PWSCC. Focussed ion beam coupled with scanning electron microscopy (FIB/SEM) 3D tomography has been used to reconstruct the morphology of grain boundary oxide penetrations and their interaction with intergranular Cr carbides in Alloy 600 subjected to a PWR environment. In presence of intergranular Cr carbides, the intergranular oxide penetrations are less deep but larger than without carbide. However, the intergranular oxide volumes normalized by the grain boundary length for both samples are similar, which suggest that intergranular oxidation growth rate is not affected by carbides. Analytical transmission electron microscopy (TEM) shows that the intergranular oxide consists mainly in a spinel-type oxide containing nickel and chromium, except in the vicinity of Cr carbides where Cr2O3 was evidenced. The formation of chromium oxide may explain the lower intergranular oxide depth observed in grain boundaries containing Cr carbides.

  4. Hydrogen adsorption and diffusion, and subcritical-crack growth in high-strength steels and nickel base alloys

    NASA Technical Reports Server (NTRS)

    Wei, R. P.; Klier, K.; Simmons, G. W.

    1974-01-01

    Coordinated studies of the kinetics of crack growth and of hydrogen adsorption and diffusion were initiated to develop information that is needed for a clearer determination of the rate controlling process and possible mechanism for hydrogen enhanced crack growth, and for estimating behavior over a range of temperatures and pressures. Inconel 718 alloy and 18Ni(200) maraging steel were selected for these studies. 18Ni(250) maraging steel, 316 stainless steel, and iron single crystal of (111) orientation were also included in the chemistry studies. Crack growth data on 18Ni(250) maraging steel from another program are included for comparison. No sustained-load crack growth was observed for the Inconel 718 alloy in gaseous hydrogen. Gaseous hydrogen assisted crack growth in the 18Ni maraging steels were characterized by K-independent (Stage 2) extension over a wide range of hydrogen pressures (86 to 2000 torr or 12 kN/m2 to 266 kN/m2) and test temperatures (-60 C to +100 C). The higher strength 18Ni(250) maraging steel was more susceptible than the lower strength 200 grade. A transition temperature was observed, above which crack growth rates became diminishingly small.

  5. A feasibility study of a diffusion barrier between Ni-Cr-Al coatings and nickel-based eutectic alloys

    NASA Technical Reports Server (NTRS)

    Young, S. G.; Zellars, G. R.

    1978-01-01

    Coating systems have been proposed for potential use on eutectic alloy components in high-temperature gas turbine engines. In a study to prevent the deterioration of such systems by diffusion, a tungsten sheet 25 microns thick was placed between eutectic alloys and an Ni-Cr-Al layer. Layered test specimens were aged at 1100 C for as long as 500 h. Without the tungsten barrier the delta phase of the eutectic deteriorated by diffusion of niobium into the Ni-Cr-Al. Insertion of the tungsten barrier stopped the diffusion of niobium from the delta phase. Chromium diffusion from the Ni-Cr-Al into the gamma/gamma-prime phase of the eutectic was greatly reduced by the barrier. However, the barrier thickness decreased with time, and tungsten diffused into both the Ni-Cr-Al and the eutectic. When the delta platelets were aligned parallel rather than perpendicular to the Ni-Cr-Al layer, diffusion into the eutectic was reduced.

  6. A multiple linear regression analysis of hot corrosion attack on a series of nickel base turbine alloys

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.

    1985-01-01

    Multiple linear regression analysis was used to determine an equation for estimating hot corrosion attack for a series of Ni base cast turbine alloys. The U transform (i.e., 1/sin (% A/100) to the 1/2) was shown to give the best estimate of the dependent variable, y. A complete second degree equation is described for the centered" weight chemistries for the elements Cr, Al, Ti, Mo, W, Cb, Ta, and Co. In addition linear terms for the minor elements C, B, and Zr were added for a basic 47 term equation. The best reduced equation was determined by the stepwise selection method with essentially 13 terms. The Cr term was found to be the most important accounting for 60 percent of the explained variability hot corrosion attack.

  7. Materials Reliability Program Low-Temperature Cracking of Nickel-Based Alloys and Weld Metals (MRP-108)

    SciTech Connect

    B. Young

    2004-02-01

    OAK-B135 A rising load test in low-temperature (50-100 degree C) pH 10 water containing a high concentration of dissolved hydrogen (150 cc/kg) has demonstrated that Alloy 690 as well as weld metals 82 and 52 exhibit a marked loss of ductility. A similar loss of ductility has been shown to occur in widely used weld metal 182 under replica test conditions and simulated PWR primary water containing 100 cc/kg of hydrogen. The objective of this report was to confirm the Bettis test results for weld metal 82 and determine whether weld metal 182 is susceptible to the same reductions in toughness. This report documents the first industry effort to reckon with the low temperature crack propagation (LTCP) issue.

  8. 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.

  9. 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.

  10. Fatigue crack propagation thresholds for long and short cracks in Rene 95 nickel-base super alloy

    SciTech Connect

    McCarver, J.F.; Ritchie, R.O.

    1981-10-01

    A study has been made of the near-threshold fatigue crack propagation behavior of a wroght Ni-base superalloy, Rene 95, with reference to the effect of crack size on the threshold stress intensity ..delta..K/sub 0/ for no detectable crack growth. Measured threshold ..delta..K/sub 0/ values at low load ratios (R = 0.1) for physically short cracks (0.01 to 0.20 mm) were found to be 60% smaller than the corresponding ..delta..K/sub 0/ values for long cracks (approx. 25 mm). However, short crack threshold values at R = 0.1 were found to be similar to long crack thresholds at R = 0.8. Such behavior is rationalized in terms of fatigue crack closure, specifically involving the role of fracture surface roughness from crystallographic crack growth in Ni-base alloys. The large difference observed in threshold values for long and physically-short cracks serves to illustrate the potential problems in applying conventional (long crack) fatigue data to defect-tolerant lifetime predictions for structural components containing small flaws.

  11. 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.

  12. Investigation on the Microstructure and Ductility-Dip Cracking Susceptibility of the Butt Weld Welded with ENiCrFe-7 Nickel-Base Alloy-Covered Electrodes

    NASA Astrophysics Data System (ADS)

    Qin, Renyao; Wang, Huang; He, Guo

    2015-03-01

    The weld metal of the ENiCrFe-7 nickel-based alloy-covered electrodes was investigated in terms of the microstructure, the grain boundary precipitation, and the ductility-dip cracking (DDC) susceptibility. Besides the dendritic gamma-Ni(Cr,Fe) phase, several types of precipitates dispersed on the austenitic matrix were observed, which were determined to be the Nb-rich MC-type carbides with "Chinese script" morphology and size of approximately 3 to 10 µm, the Mn-rich MO-type oxides with size of approximately 1 to 2 µm, and the spherical Al/Ti-rich oxides with size of less than 1 µm. The discontinuous Cr-rich M23C6-type carbides predominantly precipitate on the grain boundaries, which tend to coarsen during reheating but begin to dissolve above approximately 1273 K (1000 °C). The threshold strain for DDC at each temperature tested shows a certain degree of correlation with the grain boundary carbides. The DDC susceptibility increases sharply as the carbides coarsen in the temperature range of 973 K to 1223 K (700 °C to 950 °C). The growth and dissolution of the carbides during the welding heat cycles deteriorate the grain boundaries and increase the DDC susceptibility. The weld metal exhibits the minimum threshold strain of approximately 2.0 pct at 1323 K (1050 °C) and the DTR less than 873 K (600 °C), suggesting that the ENiCrFe-7—covered electrode has less DDC susceptibility than the ERNiCrFe-7 bare electrode but is comparable with the ERNiCrFe-7A.

  13. Vacuum-Induction, Vacuum-Arc, and Air-Induction Melting of a Complex Heat-Resistant Alloy

    NASA Technical Reports Server (NTRS)

    Decker, R. F.; Rowe, John P.; Freeman, J. W.

    1959-01-01

    The relative hot-workability and creep-rupture properties at 1600 F of a complex 55Ni-20Cr-15Co-4Mo-3Ti-3Al alloy were evaluated for vacuum-induction, vacuum-arc, and air-induction melting. A limited study of the role of oxygen and nitrogen and the structural effects in the alloy associated with the melting process was carried out. The results showed that the level of boron and/or zirconium was far more influential on properties than the melting method. Vacuum melting did reduce corner cracking and improve surface during hot-rolling. It also resulted in more uniform properties within heats. The creep-rupture properties were slightly superior in vacuum heats at low boron plus zirconium or in heats with zirconium. There was little advantage at high boron levels and air heats were superior at high levels of boron plus zirconium. Vacuum heats also had fewer oxide and carbonitride inclusions although this was a function of the opportunity for separation of the inclusions from high oxygen plus nitrogen heats. The removal of phosphorous by vacuum melting was not found to be related to properties. Oxygen plus nitrogen appeared to increase ductility in creep-rupture tests suggesting that vacuum melting removes unidentified elements detrimental to ductility. Oxides and carbonitrides in themselves did not initiate microcracks. Carbonitrides in the grain boundaries of air heats did initiate microcracks. The role of microcracking from this source and as a function of oxygen and nitrogen content was not clear. Oxygen and nitrogen did intensify corner cracking during hot-rolling but were not responsible for poor surface which resulted from rolling heats melted in air.

  14. 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

  15. Influence of Hot-Working Conditions on High-Temperature Properties of a Heat-Resistant Alloy

    NASA Technical Reports Server (NTRS)

    Ewing, John F; Freeman, J W

    1957-01-01

    The relationships between conditions of hot-working and properties at high temperatures and the influence of the hot-working on response to heat treatment were investigated for an alloy containing nominally 20 percent molybdenum, 2 percent tungsten, and 1 percent columbium. Commercially produced bar stock was solution-treated at 2,200 degrees F. to minimize prior-history effects and then rolled at temperatures of 2,200 degrees, 2,100 degrees, 2,000 degrees, 1,800 degrees, and 1,600 degrees F. Working was carried out at constant temperature and with incremental decreases in temperature simulating a falling temperature during hot-working. In addition, a few special repeated cyclic conditions involving a small reduction at high temperature followed by a small reduction at a low temperature were used to study the possibility of inducing very low strengths by the extensive precipitation accompanying such properties. Most of the rolling was done in open passes with a few check tests being made with closed passes. Heat treatments at both 2,050 degrees and 2,200 degrees F. subsequent to working were used to study the influence on response to heat treatment.

  16. 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.

  17. 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.

  18. 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.

  19. {tau} phase formation in a TiC + TiB{sub 2} composite bonded with a nickel based binder alloy

    SciTech Connect

    Ogwu, A.A.; Davies, T.J.

    1999-05-21

    Densification and ductility has been achieved in a TiC + TiB{sub 2} cermet prepared by pressureless sintering using a nickel based binder with an additive, based on their proposed empirical model. In the context of bonding in the binary, Holleck et al have suggested that the structures of TiC and TiB{sub 2} allows coherence to be established between their most densely packed lattice planes. This favorable interfacial match in the TiC + TiB{sub 2} composite is assumed to encourage a high mobility of atoms across the interface, leading to densification during sintering. The fracture toughness of a TiC + TiB{sub 2} composite would also be expected to improve when good interfacial coherence exists between TiC and TiB{sub 2}. In the case of their preferred nickel-based binder, one of the reasons for selecting the additive is to prevent the formation o deleterious grain boundary phases like the {tau} phase which often forms in Ni-TiB{sub 2} systems, with the expectation that if new phases do form they would be soluble in a TiC + TiB{sub 2} matrix. Previous attempts to find suitable sintering additives for TiB{sub 2} revealed that Fe, Co and Ni binders reacted with the TiB{sub 2} at the sintering temperatures forming secondary borides of the type M{sub 2}B. The formation of these undesirable (secondary) borides has been identified to be linked to either the presence of contaminants like oxygen, carbon and nitrogen which react with Ti, leaving behind free boron for reaction with the selected metallic binder, or, a direct reaction between the metal binder and TiB{sub 2}.

  20. Considerations on the performance and fabrication of candidate materials for the Yucca Mountain repository waste packages highly corrosion resistant nickel-base and titanium-base alloys

    SciTech Connect

    Dalder, E; Goldberg, A

    1995-11-30

    Among the metallurgical factors that affect the performance of a material in a given environment are alloy composition, alloy segregation, depletion of alloying elements, non-uniform microstructures, precipitation leading to an increase in susceptibility to corrosion as well as decreases in ductility, residual plastic deformation, and residual stresses. Precipitation often occurs preferentially at grain boundaries, causing depletion of critical elements in regions adjacent to these boundaries. Continuous grain-boundary precipitates can lead to drops in ductility and toughness. The presence of non-metallic inclusions, if excessive and/or segregated, can also cause embrittlement. Segregation of alloying elements can result in localized galvanic action. Depletion of alloying elements as well as segregation can result in reductions in the concentrations of critical elements below those necessary to resist localized corrosion. Segregation and alloy depletion can also facilitate precipitation that could lead to embrittlement.

  1. 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.

  2. Isothermal and cyclic oxidation at 1000 and 1100 deg C of four nickel-base alloys: NASA-TRW VIA, B-1900, 713C, and 738X

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.; Santoro, G. J.; Lowell, C. E.

    1973-01-01

    The isothermal and cyclic oxidation resistance of four cast Ni-base gamma + gamma prime alloys, NASA-TRW Via, B-1900, 713C, and 738X, was determined in still air at 1000 and 1100 C. The oxidation process was evaluated by specific sample weight change with time, sample thickness change, X-ray diffraction of the scales, and sample metallography. The behavior is discussed in terms of the Cr, Al, and refractory metal contents of the alloys.

  3. The role of grain boundary character in the environmentally-assisted integranular cracking mechanism of nickel-base alloys: Progress report, August 1, 1988--July 31, 1989

    SciTech Connect

    Was, G.S.

    1989-07-01

    Over the past year additional experimental results and more accurate modeling were obtained for the grain boundary chemistry and structure of controlled purity alloys 690 and X-750 material as a function of thermal treatment. High purity heats of Ni-30Cr-9Fe (alloy 690) and Ni-16Cr-9Fe-2.5Ti-0.7Al (alloy X-750) were prepared by the Materials Preparation Center, Ames Laboratory, Iowa State University. Each were doped with 0.03 wt % C. The material was delivered in the form of 3.05 mm rods for the convenience of transmission electron microscopy sample preparation. Due to casting defects in the alloys, the base stock materials were purified by electron beam melting before alloying to reduce the levels of any tramp elements that would form these casting defects. Chromium depletion profiling and analysis of precipitate composition were conducted in a JEOL 100CX STEM using energy dispersive x-ray analysis. Precipitate structure was determined by convergent beam electron diffraction in a JEOL 2000 FX STEM in addition to selected area diffraction in the JEOL 100 CX STEM. Computer modeling was done on a Macintosh II computer with the codes operating in the FORTRAN language. 8 refs., 12 figs., 14 tabs.

  4. 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.

  5. Heat resistant protective hand covering

    NASA Technical Reports Server (NTRS)

    Tschirch, R. P.; Sidman, K. R.; Arons, I. J. (Inventor)

    1984-01-01

    A heat-resistant aromatic polyamide fiber is described. The outer surface of the shell is coated with a fire-resistant elastomer and liner. Generally conforming and secured to the shell and disposed inwardly of the shell, the liner is made of a felt fabric of temperature-resistant aromatic polymide fiber.

  6. Directionally solidified eutectic gamma-gamma nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Jackson, M. R. (Inventor)

    1977-01-01

    A directionally solidified multivariant eutectic gamma-gamma prime nickel-base superalloy casting having improved high temperature properties was developed. The alloy is comprised of a two phase eutectic structure consisting essentially of on a weight percent base, 6.0 to 9.0 aluminum, 5.0 to 17.0 tantalum, 0-10 cobalt, 0-6 vanadium, 0-6 rhenium, 2.0-6.0 tungsten, and the balance being nickel, subject to the proviso that the sum of the atomic percentages of aluminum plus tantalum is within the range of from 19-22, and the ratio of atomic percentages of tantalum to aluminum plus tantalum is within the range of from 0.12 to 0.23. Embedded within the gamma nickel-base matrix are aligned eutectic gamma prime phase (primarily nickel-aluminum-tantalum) reinforcing fibers.

  7. Ultra-violet and resonant laser ablation coupled with microwave induced plasma atomic emission spectrometry and determination of tin in nickel based alloys by electrothermal atomizer atomic absorption and laser excited atomic fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Yang, Xiaodong

    Chapter 1 reviews laser ablation in analytical atomic spectrometry. Laser ablation is categorized into two functions: one is used as a sample introduction method, the other function is used as a microprobe analysis method. Both fundamental and applicational aspects are reviewed with the citations of related papers. This chapter also serves as an introduction to the work which is described in chapter 2 and chapter 3 as laser ablation is a relatively new research area for the research group. In chapter 2, instrumentation for excimer (308nm) laser ablation of samples was coupled with a microwave induced plasma (MLP), and evaluated for its potential as an approach to solid sampling for atomic emission spectrometry. Operating parameters were optimized, and the effects of laser repetition rate and number of laser shots on the emission signal were investigated. The UV excimer laser removed more material than would be expected of an infrared laser of similar energy. The chromium detection limit in the solid steel sample was estimated to be about 500 mug/g. In chapter 3, a wavelength tunable optical parametric oscillator (OPO) laser was used to ablate a steel sample into the same apparatus described in chapter 2. The emission signal for the elements was selectively enhanced when the ablation wavelength was tuned to be in resonance with any atomic transition of that element. This was the first report of the observation of resonant ablation by use of optical detection, as prior reports of resonant ablation have used mass spectrometric detectors. Chapter 4 reviews the publications in laser excited atomic fluorescence spectrometry in recent eight years. The focus of the review is on recent development on new instruments and applications of this technique. Chapter 5 studies the determination of tin in nickel-based alloys with laser excited atomic fluorescence in a graphite furnace. Zeeman electrothermal atomizer atomic absorption spectrometry and inductively coupled plasma mass

  8. Hot deformation of heat-resistant superalloys -- An overview

    SciTech Connect

    Chaudhury, P.K.; Zhao, D.; Thirukkonda, M.; Guillard, S.

    1995-12-31

    The hot deformation behavior was investigated for four heat-resistant Ni-, Fe-, and Co-base superalloys: Haynes 188, 230, 556, and HR-160. Compression tests were conducted over a wide range of processing conditions. The flow behavior and deformed microstructures were characterized, while recrystallized grain size and percentage of recrystallization were measured for deformed specimens under selected conditions. From the experimental data, constitutive equations and microstructure maps were constructed. During the high temperature deformation, a number of mutually interacting metallurgical processes, such as dynamic recrystallization and precipitation, occurred. Their influence on hot formability and deformed microstructure have been represented by deformation microstructure maps that can serve as a guideline for hot deformation process design and subsequent heat treatment after hot forming. The workability and deformation behaviors of the heat-resistant alloys are also compared in The light of alloy development to ensure the fabricability of newly developed alloys.

  9. In Situ Micro-mechanical Testing of a PM Nickel-Base Superalloy Weld

    NASA Astrophysics Data System (ADS)

    Oluwasegun, K. M.; Olawale, J. O.; Oyatogun, G. M.; Shittu, M. D.; Ige, O. O.; Malomo, B. O.

    2014-10-01

    Microstructural variations between the bond line and the base alloy of welds have been reported in various nickel-base superalloys that have found their applications as structural materials in aero- and land-based engines. This microstructural variation occurs within 50 to 100 μm of majority of welds. Thus, in order to characterize the strength variations between the weld and the base alloy, mechanical testing at micron level is required. This paper presents the use of a newly developed microtensile testing system for an in situ micro-mechanical testing of a powder metallurgy nickel-base superalloy, RR1000 performed in a focused ion beam scanning electron microscope.

  10. Heat resistant process gas line

    SciTech Connect

    Venable, C.R. Jr.

    1987-05-12

    A method is described of forming a heat resistant gas transfer line comprising a tubular metal outer shell, a tubular inner liner formed of prefired refractory rings joined together by shiplap joints having expansion gaps, and an intermediate liner comprising bubble alumina concrete filing the annular space between the inner liner and the outer shell. The method comprises placing on the inside lower surface of the outershell bubble alumina concrete forms capable of supporting the refractory rings in the desired location within the outer shell, securing decomposable rings to the refractory rings in the area where the shiplap joints are to be so that a suitable expansion gap will be provided in the shiplap joints when the combustible rings are destroyed.

  11. Heat resistant protective hand covering

    NASA Technical Reports Server (NTRS)

    Sidman, K. R.; Arons, I. J. (Inventor)

    1984-01-01

    The heat resistant, protective glove is made up of first and second shell sections which define a palm side and a backside, respectively. The first shell section is made of a twill wave fabric of a temperature-resistant aromatic polyamide fiber. The second shell section is made of a knitted fabric of a temperature-resistant aromatic polyamide fiber. The first and second shell sections are secured to one another, e.g., by sewing, to provide the desired glove configuration and an opening for insertion of the wearer's hand. The protective glove also includes a first liner section which is secured to and overlies the inner surface of the first shell section and is made of a felt fabric of a temperature-resistant aromatic polyamide fiber and has a flame resistant, elastomenic coating on the surface facing and overlying the inner surface of the first shell section.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Evaluation of Heat Checking and Washout of Heat Resistant Superalloys and Coatings for Die inserts

    SciTech Connect

    David Schwam; John F. Wallace; Yulong Zhu; Edward Courtright; Harold Adkins

    2005-01-30

    This project had two main objectives: (1) To design, fabricate and run a full size test for evaluating soldering and washout in die insert materials. This test utilizes the unique capabilities of the 350 Ton Squeeze Casting machine available in the Case Meal Casting Laboratory. Apply the test to evaluate resistance of die materials and coating, including heat resistant alloys to soldering and washout damage. (2) To evaluate materials and coatings, including heat resistant superalloys, for use as inserts in die casting of aluminum alloys.

  17. 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.

  18. 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.

  19. Plasma treatment of heat-resistant materials

    NASA Astrophysics Data System (ADS)

    Vlasov, V. A.; Kosmachev, P. V.; Skripnikova, N. K.; Bezukhov, K. A.

    2015-11-01

    Refractory lining of thermal generating units is exposed to chemical, thermal, and mechanical attacks. The degree of fracture of heat-resistant materials depends on the chemical medium composition, the process temperature and the material porosity. As is known, a shortterm exposure of the surface to low-temperature plasma (LTP) makes possible to create specific coatings that can improve the properties of workpieces. The aim of this work is to produce the protective coating on heat-resistant chamotte products using the LTP technique. Experiments have shown that plasma treatment of chamotte products modifies the surface, and a glass-ceramic coating enriched in mullite is formed providing the improvement of heat resistance. For increasing heat resistance of chamotte refractories, pastes comprising mixtures of Bacor, alumina oxide, and chamot were applied to their surfaces in different ratios. It is proved that the appropriate coating cannot be created if only one of heat-resistant components is used. The required coatings that can be used and recommended for practical applications are obtained only with the introduction of powder chamot. The paste composition of 50% chamot, 25% Bacor, and 25% alumina oxide exposed to plasma treatment, has demonstrated the most uniform surface fusion.

  20. 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.

  1. Effects of fabrication practices and techniques on the corrosion and mechanical properties of Ni-Cr-Mo nickel based alloys UNS N10276, N06022, N06686, and N06625

    SciTech Connect

    Hinshaw, E.B.; Crum, J.R.

    1996-11-01

    Ni-Cr-Mo alloys have excellent resistance to both oxidizing and reducing type environments; however, heat treating, surface condition, welding, and type of welding consumable can have a significant affect on the corrosion resistance and mechanical properties of these alloys. It is also important when performing standard ASTM intergranular corrosion tests on welded test coupons to make an accurate comparison of alloys being tested. A standard weld procedure and consistent post-weld sample conditioning method should be incorporated into the comparison test program. An evaluation of the effect of various fabrication practices on the corrosion resistance of the alloy was performed using accelerated corrosion tests ASTM G28B. The fabrication conditions examined were as-welded, welded-pickled, welded-annealed-pickled, welded annealed ground, welded-ground, using over matching filler metals, and various levels of heat input. In addition to fabrication techniques, the effect of ASTM G28B test duration on corrosion rates of UNS N10276, N06022, N06686, and N06625 was evaluated. ASTM G28A intergranular corrosion and mechanical testing using welded coupons of UNS N06625 were also performed to determine the affect of post-weld annealing and aging heat treatments on the corrosion resistance and mechanical properties of UNS N06625.

  2. 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.

  3. Near-Surface Residual Stress Assessment in Inhomogeneous Nickel-Base Superalloys

    NASA Astrophysics Data System (ADS)

    Yu, F.; Nagy, P. B.

    2006-03-01

    Recently, it has been shown that shot-peened nickel-base superalloys exhibit an approximately 1% increase in apparent eddy current conductivity at high inspection frequencies, which can be exploited for nondestructive subsurface residual stress assessment. Unfortunately, microstructural inhomogeneity in certain as-forged and precipitation hardened nickel-base superalloys, like Waspaloy, can lead to significantly larger electrical conductivity variations of as much as 4-6%. This intrinsic conductivity variation adversely affects the accuracy of residual stress evaluation in shot-peened and subsequently thermal-relaxed specimens, but does not completely prevent it. Experimental results are presented to demonstrate that the conductivity variation resulting from volumetric inhomogeneities in as-forged engine alloys do not display significant frequency dependence. This characteristic independence of frequency can be exploited to distinguish these inhomogeneities from near-surface residual stress and cold work effects caused by surface treatment, which, in contrast, are strongly frequency-dependent.

  4. Near-Surface Residual Stress Assessment in Inhomogeneous Nickel-Base Superalloys

    SciTech Connect

    Yu, F.; Nagy, P. B.

    2006-03-06

    Recently, it has been shown that shot-peened nickel-base superalloys exhibit an approximately 1% increase in apparent eddy current conductivity at high inspection frequencies, which can be exploited for nondestructive subsurface residual stress assessment. Unfortunately, microstructural inhomogeneity in certain as-forged and precipitation hardened nickel-base superalloys, like Waspaloy, can lead to significantly larger electrical conductivity variations of as much as 4-6%. This intrinsic conductivity variation adversely affects the accuracy of residual stress evaluation in shot-peened and subsequently thermal-relaxed specimens, but does not completely prevent it. Experimental results are presented to demonstrate that the conductivity variation resulting from volumetric inhomogeneities in as-forged engine alloys do not display significant frequency dependence. This characteristic independence of frequency can be exploited to distinguish these inhomogeneities from near-surface residual stress and cold work effects caused by surface treatment, which, in contrast, are strongly frequency-dependent.

  5. Method for producing heat-resistant semi-inorganic compounds

    NASA Technical Reports Server (NTRS)

    Yajima, S.; Okamura, K.; Shishido, T.; Hasegawa, Y.

    1983-01-01

    The method for producing a heat resistant, semi-inorganic compound is discussed. Five examples in which various alcohols, phenols, and aromatic carbonic acids are used to test heat resistance and solubility are provided.

  6. Effects of cobalt in nickel-base superalloys

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    A study has been carried out to assess the role of cobalt in Udimet 700, a representative nickel-base superalloy containing 17 percent or more cobalt. The study spans the spectrum of microstructural, microchemical, and mechanical behavior aspects which together form a basis for superalloy performance in jet engines. The results suggest that cobalt affects the solubility of elements in the gamma matrix, which leads to enhanced gamma-prime volume fraction and to the stabilization of MC-type carbides and sigma phase. However, these microstructural and microchemical changes are too slight to significantly affect the strength and ductile properties. Depending on the heat treatment, the creep and stress rupture resistance can be cobalt-sensitive. In the coarse-grained, fully solutioned and aged condition, all of the alloy's 17 percent Co can be replaced by nickel without decreasing the creep and stress rupture resistance. These findings are discussed with reference to existing theories and experimental data obtained by other workers.

  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. 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.

  9. 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.

  10. 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.

  11. Nondestructive evaluation of near-surface residual stress in shot-peened nickel-base superalloys

    NASA Astrophysics Data System (ADS)

    Yu, Feng

    Surface enhancement methods, which produce beneficial compressive residual stresses and increased hardness in a shallow near-surface region, are widely used in a number of industrial applications, including gas-turbine engines. Nondestructive evaluation of residual stress gradients in surface-enhanced materials has great significance for turbine engine component life extension and their reliability in service. It has been recently found that, in sharp contrast with most other materials, shot-peened nickel-base superalloys exhibit an apparent increase in electrical conductivity at increasing inspection frequencies, which can be exploited for nondestructive residual stress assessment. The primary goal of this research is to develop a quantitative eddy current method for nondestructive residual stress profiles in surface-treated nickel-base superalloys. Our work have been focused on five different aspects of this issue, namely, (i) validating the noncontacting eddy current technique for electroelastic coefficients calibration, (ii) developing inversion procedures for determining the subsurface residual stress profiles from the measured apparent eddy current conductivity (AECC), (iii) predicting the adverse effect of surface roughness on the eddy current characterization of shot-peened metals, (iv) separating excess AECC caused by the primary residual stress effect from intrinsic conductivity variations caused by material inhomogeneity, and (v) investigating different mechanisms through which cold work could influence the AECC in surface-treated nickel-base superalloys. The results of this dissertation have led to a better understanding of the underlying physical phenomenon of the measured excess AECC on nickel-base engine alloys, and solved a few critical applied issues in eddy current nondestructive residual stress assessment in surface-treated engine components and, ultimately, contributed to the better utilization and safer operation of the Air Force's aging

  12. Heat resistance poly(vinyl alcohol) hydrogel

    NASA Astrophysics Data System (ADS)

    Yoshii, F.; Makuuchi, K.; Darwis, D.; Iriawan, T.; Razzak, M. T.; Rosiak, Janusz M.

    1995-08-01

    Six methods were used to evaluate the heat resistance of poly(vinyl alcohol) (PVA) hydrogel prepared by a combination of electron beam irradiation and acetalization of PVA. The physical properties of the hydrogel depended on the degree of acetilization which was affected by content of water in PVA sheet of acetalization in formaldehyde solution at 60°C. It was found that the optimum water content was 20-30%. The acetalized PVA sheet gave maximum tensile strength in electron beams irradiation at 100 kGy. The tensile strength of the hydrogel film increased to 20 MPa from 14 MPa by the irradiation. Heat resistance of the hydrogel was evaluated by measuring the mechanical properties after sterilization in a steam autoclave at 121°C for 90 min. The tensile strength decreased to 10 MPa whereas the elongation at break increased to 300%. The tackiness of the hydrogel was improved by radiation grafting of acrylic acid. Wholesomeness of the hydrogel as a wound dressing was evaluated by attaching to a burn or wound of the back skin of marmots. Advantages of the hydrogel over a gauze dressing were homogeneous adhesion to the affected parts, easy removal without damage to renewed skin and slightly faster rate of reconstruction of the injured skin.

  13. Spore heat resistance and specific mineralization.

    PubMed Central

    Bender, G R; Marquis, R E

    1985-01-01

    Spores of Bacillus megaterium ATCC 19213, Bacillus subtilis niger and Bacillus stearothermophilus ATCC 7953 were converted to fully demineralized, but viable, H forms by controlled acid titration. H forms were more heat sensitive than were native forms, but z values were greater for killing of H spores than those for native spores. Therefore, the differences in heat sensitivity between native and H forms decreased with increasing killing temperature. The increase in heat sensitivity associated with demineralization did not appear to be due to damage to cortex lytic enzymes of the germination system because it could not be moderated by decoating heated H spores and plating them on medium with added lysozyme. H spores could be remineralized by means of back titration with appropriate base solutions. The remineralized spores, except for the Na form, were then more heat resistant than were H spores. Ca and Mn were more effective in restoring resistance than were Mg and K. Generally, the remineralized forms (except for the Na form) had z values greater than those of the native forms but still less than those of the H forms. At lower killing temperatures, the reinstatement of resistance could be related to the extent of remineralization. However, at higher killing temperatures, only a fraction of the mineral was effective in restoring resistance, and higher levels of remineralization did not result in greater resistance. Mineralization is clearly an important factor in spore heat resistance, but the relationship between resistance and mineralization is complex and dependent on killing temperature. PMID:3937495

  14. Gamma prime shape changes during creep of a nickel-base superalloy

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

    Changes in the shape of the gamma-prime phase in the single-crystal nickel base alloy NASAIR 100 during tensile and compressive creep have been investigated experimentally by Laue X-ray diffractometry. It is found that under tensile loading, gamma-prime changes from the initial cubic shape to plates perpendicular to the applied stress. This change occurs during primary creep at 1000 C, 148 MPa. Prolonged creep exposures result in a thickening of the gamma-prime plates that is similar to Ostwald ripening often observed in other superalloys during creep. Under compressive loading, two sets of gamma-prime plates parallel to the applied stress are formed.

  15. 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.

  16. Directionally solidified eutectic gamma plus beta nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Jackson, M. R. (Inventor)

    1977-01-01

    A directionally solidified multivariant eutectic gamma + beta nickel-base superalloy casting having improved high temperature strength and oxidation resistance properties is provided. This comprises a two phase eutectic structure containing, on a weight percent basis, 5.0-15.0 tungsten, 8.5-14.5 aluminum, 0.0-35.0 cobalt and the balance being nickel. Embedded within the gamma phase nickel-base matrix are aligned eutectic beta phase (primarily (NiCo)Al reinforcing lamellae.

  17. Microstructure of the Nickel-Base Superalloy CMSX-4 Fabricated by Selective Electron Beam Melting

    NASA Astrophysics Data System (ADS)

    Ramsperger, Markus; Singer, Robert F.; Körner, Carolin

    2016-03-01

    Powder bed-based additive manufacturing (AM) processes are characterized by very high-temperature gradients and solidification rates. These conditions lead to microstructures orders of magnitude smaller than in conventional casting processes. Especially in the field of high performance alloys, like nickel-base superalloys, this opens new opportunities for homogenization and alloy development. Nevertheless, the high susceptibility to cracking of precipitation-hardenable superalloys is a challenge for AM. In this study, electron beam-based AM is used to fabricate samples from gas-atomized pre-alloyed CMSX-4 powder. The influence of the processing strategy on crack formation is investigated. The samples are characterized by optical and SEM microscopy and analyzed by microprobe analysis. Differential scanning calorimetry is used to demonstrate the effect of the fine microstructure on characteristic temperatures. In addition, in situ heat treatment effects are investigated.

  18. 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.

  19. Corrosion resistance of sodium sulfate coated cobalt-chromium-aluminum alloys at 900 C, 1000 C, and 1100 C

    NASA Technical Reports Server (NTRS)

    Santoro, G. J.

    1979-01-01

    The corrosion of sodium sulfate coated cobalt alloys was measured and the results compared to the cyclic oxidation of alloys with the same composition, and to the hot corrosion of compositionally equivalent nickel-base alloys. Cobalt alloys with sufficient aluminum content to form aluminum containing scales corrode less than their nickel-base counterparts. The cobalt alloys with lower aluminum levels form CoO scales and corrode more than their nickel-base counterparts which form NiO scales.

  20. Nucleation in a nickel-based superalloy utilizing computational thermodynamics and diffusion kinetics

    NASA Astrophysics Data System (ADS)

    Boutwell, Brett Allen Rohrer

    A model for predicting nucleation kinetics of coherent, homogeneous precipitates using thermodynamic and diffusion kinetic data calculated by computer modeling software was developed. The nucleation model incorporated classical nucleation theory along with derivations of the incubation time using the theory of time reversal symmetry. An atomic mobility database was developed for a seven-element nickel-based superalloy to allow for the calculation of multicomponent diffusivities to be used in the incubation time calculations. The seven elements modeled in the database were: nickel (Ni), iron (Fe), chromium (Cr), niobium (Nb), titanium (Ti), aluminum (Al), and carbon (C). The process of assessing an atomic mobility database is discussed, and the difficulties of assembling such a database are reviewed. The nucleation model and atomic mobility database were then applied to modeling the nucleation kinetics of gamma' in two nickel-aluminum binary alloys. The results of the nucleation model were in good agreement with one binary alloy but did not agree well with the results for the second alloy. Enhanced diffusion due to excess vacancy concentrations was identified as the most probable reason for the discrepancy with the second nickel-aluminum alloy. The nucleation model and atomic mobility database were then tested on an industrial, multicomponent nickel-based superalloy, Inconel alloy 706. The precipitation kinetics of two coherent precipitates, gamma' and gamma'', were modeled and compared to Time-Temperature-Transformation diagrams and Time-Temperature-Hardness diagrams for the alloy. The calculated incubation times for gamma ' and gamma'' were faster than the experimentally observed transformation start times. The results of the gamma' incubation time calculations were in close approximation to the experimental data at higher temperatures. The results of the gamma'' calculations did not agree well with the experimental data.

  1. Genetic determinants of heat resistance in Escherichia coli

    PubMed Central

    Mercer, Ryan G.; Zheng, Jinshui; Garcia-Hernandez, Rigoberto; Ruan, Lifang; Gänzle, Michael G.; McMullen, Lynn M.

    2015-01-01

    Escherichia coli AW1.7 is a heat resistant food isolate and the occurrence of pathogenic strains with comparable heat resistance may pose a risk to food safety. To identify the genetic determinants of heat resistance, 29 strains of E. coli that differed in their of heat resistance were analyzed by comparative genomics. Strains were classified as highly heat resistant strains, exhibiting a D60-value of more than 6 min; moderately heat resistant strains, exhibiting a D60-value of more than 1 min; or as heat sensitive. A ~14 kb genomic island containing 16 predicted open reading frames encoding putative heat shock proteins and proteases was identified only in highly heat resistant strains. The genomic island was termed the locus of heat resistance (LHR). This putative operon is flanked by mobile elements and possesses >99% sequence identity to genomic islands contributing to heat resistance in Cronobacter sakazakii and Klebsiella pneumoniae. An additional 41 LHR sequences with >87% sequence identity were identified in 11 different species of β- and γ-proteobacteria. Cloning of the full length LHR conferred high heat resistance to the heat sensitive E. coli AW1.7ΔpHR1 and DH5α. The presence of the LHR correlates perfectly to heat resistance in several species of Enterobacteriaceae and occurs at a frequency of 2% of all E. coli genomes, including pathogenic strains. This study suggests the LHR has been laterally exchanged among the β- and γ-proteobacteria and is a reliable indicator of high heat resistance in E. coli. PMID:26441869

  2. Micrographic detection of plastic deformation in nickel-base alloys

    DOEpatents

    Steeves, A.F.; Bibb, A.E.

    1980-09-20

    A method for detecting low levels of plastic deformation in metal articles comprising electrolytically etching a flow free surface of the metal article with nital at a current density of less than about 0.1 amp/cm/sup 2/ and microscopically examining the etched surface to determine the presence of alternating striations. The presence of striations indicates plastic deformation in the article.

  3. Micrographic detection of plastic deformation in nickel base alloys

    DOEpatents

    Steeves, Arthur F.; Bibb, Albert E.

    1984-01-01

    A method for detecting low levels of plastic deformation in metal articles comprising electrolytically etching a flow free surface of the metal article with nital at a current density of less than about 0.1 amp/cm.sup.2 and microscopically examining the etched surface to determine the presence of alternating striations. The presence of striations indicates plastic deformation in the article.

  4. The effect of interface properties on nickel base alloy composites

    NASA Technical Reports Server (NTRS)

    Groves, M.; Grossman, T.; Senemeier, M.; Wright, K.

    1995-01-01

    This program was performed to assess the extent to which mechanical behavior models can predict the properties of sapphire fiber/nickel aluminide matrix composites and help guide their development by defining improved combinations of matrix and interface coating. The program consisted of four tasks: 1) selection of the matrices and interface coating constituents using a modeling-based approach; 2) fabrication of the selected materials; 3) testing and evaluation of the materials; and 4) evaluation of the behavior models to develop recommendations. Ni-50Al and Ni-20AI-30Fe (a/o) matrices were selected which gave brittle and ductile behavior, respectively, and an interface coating of PVD YSZ was selected which provided strong bonding to the sapphire fiber. Significant fiber damage and strength loss was observed in the composites which made straightforward comparison of properties with models difficult. Nevertheless, the models selected generally provided property predictions which agreed well with results when fiber degradation was incorporated. The presence of a strong interface bond was felt to be detrimental in the NiAI MMC system where low toughness and low strength were observed.

  5. Elevated temperature deformation of TD-nickel base alloys

    NASA Technical Reports Server (NTRS)

    Petrovic, J. J.; Kane, R. D.; Ebert, L. J.

    1972-01-01

    Sensitivity of the elevated temperature deformation of TD-nickel to grain size and shape was examined in both tension and creep. Elevated temperature strength increased with increasing grain diameter and increasing L/D ratio. Measured activation enthalpies in tension and creep were not the same. In tension, the internal stress was not proportional to the shear modulus. Creep activation enthalpies increased with increasing L/D ratio and increasing grain diameter, to high values compared with that of the self diffusion enthalpy. It has been postulated that two concurrent processes contribute to the elevated temperature deformation of polycrystalline TD-nickel: (1) diffusion controlled grain boundary sliding, and (2) dislocation motion.

  6. 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.

  7. 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.

  8. Resonance ultrasound spectroscopy forward modeling and inverse characterization of nickel-based superalloys

    NASA Astrophysics Data System (ADS)

    Biedermann, Eric; Jauriqui, Leanne; Aldrin, John C.; Goodlet, Brent; Pollock, Tresa; Torbet, Chris; Mazdiyasni, Siamack

    2015-03-01

    The objective of this paper is to investigate Resonance Ultrasound Spectroscopy (RUS) measurement models to more precisely connect changes in the resonance frequencies of nickel-based super-alloy material to the macro/microscopic state. RUS models using analytical solutions and the finite element method (FEM) were developed to address varying elastic properties, grain structures and creep. Experimental studies were performed investigating the effect of exposure to high temperatures and stress for varying part shape and three grain structure classes: single crystals, directionally-solidified and polycrystalline structures. Inversion using both traditional analytical models was enhanced in order to simultaneously estimate varying material properties and changes in part geometry due to creep. Inversion using surrogate models from FEM simulations was also developed, addressing varying crystal orientation and complex geometries. Results are presented comparing the forward model trends and inversion results with nickel alloy parts under various test conditions.

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

    SciTech Connect

    ME Petrichek

    2005-12-16

    Prior to the restructuring of the Prometheus Program, the NRPCT was tasked with delivering a nuclear space reactor. Potential NRPCT nuclear space reactor designs for the Prometheus Project required dissimilar materials to be in contact with each other while operating at extreme temperatures under irradiation. As a result of the high reactor core temperatures, refractory metals were the primary candidates for many of the reactor structural and cladding components. They included the tantalum-base alloys ASTAR-811C and Ta-10W, the niobium-base alloy FS-85, and the molybdenum base alloys Moly 41-47.5 Rhenium. The refractory metals were to be joined to candidate nickel base alloys such as Haynes 230, Alloy 617, or Nimonic PE 16 either within the core if the nickel-base alloys were ultimately selected to form the outer core barrel, or at a location exterior to the core if the nickel-base alloys were limited to components exterior to the core. To support the need for dissimilar metal joints in the Prometheus Project, a co-extrusion experiment was proposed. There are several potential methods for the formation of dissimilar metal joints, including explosive bonding, friction stir welding, plasma spray, inertia welding, HIP, and co-extrusion. Most of these joining methods are not viable options because they result in the immediate formation of brittle intermetallics. Upon cooling, intermetallics form in the weld fusion zone between the joined metals. Because brittle intermetallics do not form during the initial bonding process associated with HIP, co-extrusion, and explosive bonding, these three joining procedures are preferred for forming dissimilar metal joints. In reference to a Westinghouse Astronuclear Laboratory report done under a NASA sponsored program, joints that were fabricated between similar materials via explosive bonding had strengths that were directly affected by the width of the diffusion barrier. It was determined that the diffusion zone should not exceed

  10. 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.

  11. Some Properties of Heat-Resistant and Heat-Sensitive Strains of Clostridium perfringens I. Heat Resistance and Toxigenicity1

    PubMed Central

    Weiss, Karl F.; Strong, Dorothy H.

    1967-01-01

    Heat resistance at 100 C (D-values), sporulating ratios, toxigenicity for mice, and lecithinase activity (as micrograms per milliliter of enzyme, ascertained by the lecithovitellin reaction) were determined for four strains of Clostridium perfringens. A definite inverse relationship between thermal resistance and toxigenicity was found. The D-values ranged from 17.6 for the most heat-resistant strain to 0.3 for the strain possessing the least heat resistance, with corresponding lecithinase activities from 25 to 133 μg/ml of enzyme. The sporulating ratios did not differ greatly between the strains. The heat stability of the toxin was greater at 100 C than at 75 C. There was a noticeable difference between the heat stabilities of the toxin in the culture fluids of the heat-sensitive and heat-resistant strains at pH 7.0 when the toxic filtrates were held at 100 C. At a holding temperature of 75 C, a similar but lesser difference was observed at pH 5.5. Heat resistance and lecithinase activity did not change when a substrain of the least heat-resistant parent strain was obtained through heat selection by a single transfer, or when the most heat-resistant strain was transferred serially 12 times. PMID:4289809

  12. COATED ALLOYS

    DOEpatents

    Harman, C.G.; O'Bannon, L.S.

    1958-07-15

    A coating is described for iron group metals and alloys, that is particularly suitable for use with nickel containing alloys. The coating is glassy in nature and consists of a mixture containing an alkali metal oxide, strontium oxide, and silicon oxide. When the glass coated nickel base metal is"fired'' at less than the melting point of the coating, it appears the nlckel diffuses into the vitreous coating, thus providing a closely adherent and protective cladding.

  13. 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.

  14. Oxidation of a Commercial Nickel-Based Superalloy under Static Loading

    NASA Astrophysics Data System (ADS)

    Foss, B. J.; Hardy, M. C.; Child, D. J.; McPhail, D. S.; Shollock, B. A.

    2014-12-01

    The current demands of the aviation industry for increased gas-turbine efficiency necessitate higher turbine entry temperatures, requiring that alloys exhibit superior oxidation resistance. The synergistic effects of oxidation and mechanical stresses pose a complex issue. The purpose of the current research was to examine the effects of stress on the oxidation and oxygen transport in a commercial nickel-based superalloy. Fine grain RR1000 in both polished and shot-peened conditions was studied for classic (zero load) and statically loaded conditions using integrated two-stage isotopic tracing combined with focused-ion-beam secondary ion mass spectrometry (FIB-SIMS). Cr2O3 external oxide formed with semicontinuous TiO2 above and below. Preferential grain boundary Al2O3 internal oxide formation, γ'-dissolution, and recrystallization occurred subsurface. Oxidation mechanisms were dominated by anionic/cationic growth in the external oxide with inward oxygen transport, initially through the partially unprotective external oxide, then along internal oxide/alloy interfaces. Loading did not influence the oxidation products formed but did bring about expedited oxidation kinetics and changes to the oxide morphology. The oxygen diffusivity D {O/ * } (×10-13 cm2s-1) ranged from 0.39 for the polished alloy to 3.7 for the shot-peened condition under compressive stress. Arguably, the most significant effects took place in the subsurface regions. Increased oxidation kinetics were attributed to the development of fast cation diffusion paths as the alloy deformed by creep.

  15. 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.

  16. 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.

  17. On the Detection of Creep Damage in a Directionally Solidified Nickel Base Superalloy Using Nonlinear Ultrasound

    NASA Astrophysics Data System (ADS)

    Kang, Jidong; Qu, Jianmin; Saxena, Ashok; Jacobs, Larry

    2004-02-01

    A limited experimental study was conducted to investigate the feasibility of using nonlinear ultrasonic technique for assessing the remaining creep life of a directionally solidified (DS) nickel base superalloy. Specimens of this alloy were subjected to creep testing at different stress levels. Creep tests were periodically interrupted at different creep life fractions to conduct transmission ultrasonic tests to explore if a correlation exists between the higher order harmonics and the accumulated creep damage in the samples. A strong and unique correlation was found between the third order harmonic of the transmitted wave and the exhausted creep life fraction. Preliminary data also show an equally strong correlation between plastic deformation accumulated during monotonic loading and the second harmonic of the transmitted ultrasonic wave while no correlation was found between plastic strain and the third order harmonic. Thus, the nonlinear ultrasonic technique can potentially distinguish between damage due to plastic deformation and creep deformation.

  18. Microstructure and residual stress of laser rapid formed Inconel 718 nickel-base superalloy

    NASA Astrophysics Data System (ADS)

    Liu, Fencheng; Lin, Xin; Yang, Gaolin; Song, Menghua; Chen, Jing; Huang, Weidong

    2011-02-01

    The microstructure and residual stress of laser rapid formed (LRFed) nickel-base superalloy Inconel 718 was investigated. The as-deposited microstructure of an LRFed Inconel 718 alloy is composed of columnar dendrites growing epitaxially along the deposition direction, and the columnar dendrites transformed to unevenly distributed equiaxed grains after annealing treatment at high temperature. Residual stress evaluation in microstructure scale by Vickers micro-indentation method indicates that the residual thermal stress is unevenly distributed in the LRFed sample, and it has a significant effect on the recrystallization during solution annealing treatment. The residual stress is introduced by rapid heating and cooling during laser rapid forming. There is an alternative distribution between high residual stress regions and low residual stress regions, within a single deposited layer, resulting in a similar distribution of recrystallized grain size.

  19. 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.

  20. 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

  1. Neutron Absorbing Alloys

    DOEpatents

    Mizia, Ronald E.; Shaber, Eric L.; DuPont, John N.; Robino, Charles V.; Williams, David B.

    2004-05-04

    The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.

  2. 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.

  3. Tensile Behavior of Long-term Aged Nickel-base Superalloy

    NASA Astrophysics Data System (ADS)

    Xia, P. C.; Chen, F. W.; Xie, K.; Yu, J. J.

    2015-07-01

    The microstructural change of directionally solidified nickel-base superalloy which was aged at 900 °C for 1500 hours and tensile behavior at different temperatures were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM). γ' phase of the alloy coarsens and rafts in the course of aged treatment. The driving force of rafting is the decrease of interface energy and elastic strain energy. The stress of aged alloy increases slightly with the testing temperature. This arises from a few dislocations shearing the γ' precipitates. There is a peak stress value at 760 °C, which is attributed to the high strength of the γ' phase, the homogeneous deformation structure, and dislocation-γ' precipitate and dislocation-dislocation interactions. The stress then decreases rapidly with increased temperature. The low stress of the γ' phase and γ' rafting at high temperature contribute to the drop of alloy strength. The change of elongation is inverse to that of the stress.

  4. 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.

  5. 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.

  6. Mechanical properties of white layers formed by different machining processes on nickel-based superalloy

    NASA Astrophysics Data System (ADS)

    Proust, Edouard

    Nickel-based superalloys are widely used in the aerospace industry in the production of turbine discs and blades because of their good mechanical properties and great corrosion resistance at high temperature. Although very useful, these alloys are hard to machine. Their structure is responsible for rapid wear of cutting tools. Moreover, under certain machining conditions, near-surface regions of the material undergo a phase transformation resulting in the formation of a thin layer called "white etching layer" at the surface of the machined workpiece. Because turbine discs are safety critical components, no defects can be tolerated on the workpiece. Therefore, efforts should be made to ensure that this white etching layer can't influence the operating life of the workpiece and make its operation unsafe. Even if the existence of the white etching layer is well known, its mechanical properties have never been assessed in detail. In this thesis, we present a study of the mechanical (hardness and Young's modulus) and microstructural properties of white etching layers formed at the surface of nickel-based superalloy IN100 turbine discs fabricated by different machining processes. This work aims at evaluating the impact of the machining process and of fatigue on the properties of the white etching layers under study. The originality of this study primarily lies in the employed characterization technique. Using nanoindentation has allowed us to very precisely assess the variations of both the hardness and the Young's modulus along the white etching layers. Also, the use of a sophisticated indentation system has enabled the acquisition of very precise surface images of the samples and therefore to study the microstructure of the white etching layers. This research has demonstrated that the mechanical and microstructural properties of the white etching layers are closely linked to the machining conditions of the material. Therefore, our study will help researchers gain a

  7. Sporulation, Heat Resistance, and Biological Properties of Clostridium perfringens

    PubMed Central

    Nishida, S.; Seo, N.; Nakagawa, M.

    1969-01-01

    A sporulation medium for 134 Clostridium perfringens strains, including types A, B, C, D, E, and F, was devised according to Grelet's observation that sporulation occurred when cultural environment became limited in any nutritional requirement indispensable for the growth of the organism. Sporulation took place most prominently when 10% cooked-meat broth (pH 7.2) containing 3% Proteose Peptone and 1% glucose was used for the preculture and 2% Poli Peptone medium (pH 7.8) was used for the subculture medium. Sometimes, terminal spores could be observed. A correlation between sporulation and heat resistance was examined by use of C. perfringens strains isolated from samples heated at different temperatures. Almost all strains isolated from unheated samples and from those heated at lower temperatures gave rise to spores in our sporulation medium, but the spores were weakly heat-resistant, whereas strains isolated from samples heated at 100 C for 60 min were highly heat-resistant but sporulated poorly. A majority of these heat-resistant strains were non-gelatinolytic and definitely salicin-fermenting. Images PMID:4304763

  8. Protoplast dehydration correlated with heat resistance of bacterial spores.

    PubMed Central

    Nakashio, S; Gerhardt, P

    1985-01-01

    Water content of the protoplast in situ within the fully hydrated dormant bacterial spore was quantified by use of a spore in which the complex of coat and outer (pericortex) membrane was genetically defective or chemically removed, as evidenced by susceptibility of the cortex to lysozyme and by permeability of the periprotoplast integument to glucose. Water content was determined by equilibrium permeability measurement with 3H-labeled water (confirmed by gravimetric measurement) for the entire spore, with 14C-labeled glucose for the integument outside the inner (pericytoplasm) membrane, and by the difference for the protoplast. The method was applied to lysozyme-sensitive spores of Bacillus stearothermophilus, B. subtilis, B. cereus, B. thuringiensis, and B. megaterium (four types). Comparable lysozyme-resistant spores, in which the outer membrane functioned as the primary permeability barrier to glucose, were employed as controls. Heat resistances were expressed as D100 values. Protoplast water content of the lysozyme-sensitive spore types correlated with heat resistance exponentially in two distinct clusters, with the four B. megaterium types in one alignment, and with the four other species types in another. Protoplast water contents of the B. megaterium spore types were sufficiently low (26 to 29%, based on wet protoplast weight) to account almost entirely for their lesser heat resistance. Corresponding values of the other species types were similar or higher (30 to 55%), indicating that these spores depended on factors additional to protoplast dehydration for their much greater heat resistance. PMID:3988704

  9. Effects of Cobalt on Structure, Microchemistry and Properties of a Wrought Nickel-Base Superalloy

    NASA Astrophysics Data System (ADS)

    Jarrett, Robert N.; Tien, John K.

    1982-06-01

    Cobalt in a 17 pct cobalt containing wrought nickel-base superalloy is systematically substituted for by nickel in order to determine the role of cobalt. The eventual goal is to reduce the levels of cobalt, a critical strategic element, in superalloys. It is found that the strengthening γ microstructure is highly heat treatment sensitive. Reducing cobalt did not result in a reduction of the fine γ precipitates after a coarse grain type (blading) heat treatment, but did after a fine grain type (disk) heat treatment. Representative mechanical properties were determined for each case to isolate microstructural and microchemistry effects. Ambient yield strength and tensile strength were seen to decrease by no more than 15 pct and 7 pct, respectively, even when all the cobalt was removed. The decrease in strength is quantitatively discussed and shown to be consistent with the observed microstructural results and microchemistry results obtained using STEM/EDS. Elevated temperature creep and stress rupture resistances were concluded to be affected by alloy cobalt content through its effect on strengthening γ volume fraction. Significant decreases in these properties were observed for the lower cobalt content alloys. Long term aging, precipitate coarsening, and carbide stability results are also presented and discussed.

  10. 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.

  11. 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.

  12. 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.

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

    SciTech Connect

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

    1985-10-01

    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.

  14. Corrosion Behavior of Arc Sprayed Nickel-Base Coatings

    NASA Astrophysics Data System (ADS)

    He, Dingyong; Dong, Na; Jiang, Jianmin

    2007-12-01

    In this study, nickel-base cored wires were prepared by using NiCr strip to wrap metal powders of nickel (Ni), chromium (Cr), molybdenum (Mo), and chromium boron (CrB). Nickel-base coatings were prepared by electric arc spraying. Microstructures of Ni-Cr-Mo and Ni-Cr-B coatings were investigated using scanning electron microscopy (SEM), energy-dispersive analysis (EDAX), and x-ray diffraction (XRD) analysis. The coatings have a compact surface and presented a bonding strength higher than 40 MPa. Potentiodynamic polarization measurements and salt-spray test were carried out to determine the corrosion behavior of the coatings. The results showed that Ni-base coatings containing Mo (5%) or B (2-4%) had better antichlorine ion corrosion performance than that of Ni-base coatings without Mo element, and PS45 (Ni-Cr-Ti) coating. The antichlorine ion corrosion coatings could be used for resolving the corrosion protection problem of the equipment and piping contacting sour, alkali, salt liquid in petrochemical engineering applications.

  15. Fatigue and creep-fatigue deformation of several nickel-base superalloys at 650 °c

    NASA Astrophysics Data System (ADS)

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

    1982-10-01

    Specimens of seven nickel-base superalloys for gas turbine disk application that had been failed in fatigue and creep-fatigue at 650 °C were examined by transmission electron microscopy to observe the effects of composition and microstructure on the deformation characteristics of the alloys. The alloys were Waspaloy, HIP Astroloy, H+F Astroloy, H+F René 95, IN 100, MERL 76, and NASA IIB-7. The amount of bulk deformation observed in all the alloys was low. At inelastic strain amplitudes less than about 10-3 only favorably oriented grains exhibited yielding, and the majority of those had <110> near the tensile axis. Deformation occurred on octahedral systems for all the alloys except MERL 76, which also exhibited primary cube slip. The difference in slip behavior between MERL 76 and its parent composition, IN 100, was attributed to the addition of Nb. Deformation occurred in well-defined slip bands in the alloys that contained only fine aging γ', 0.01 to 0.06 μm in size. Alloys which also contained a population of larger aging γ' particles, 0.1 to 0.3 μm, exhibited more homogeneous deformation. Deformation in the creep-fatigue cycle, which employed a 15 minute dwell at the maximum tensile strain of the cycle, was not greatly different from fatigue deformation except that a few extended faults were formed.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Properties of Nickel-Based Hydrogen-Turbine Blades

    NASA Technical Reports Server (NTRS)

    Deluca, D. P.; Warren, J. P.; Cowles, B. A.; Shoemaker, D.; Teel, J. R. J.; Pearson, D. L.; Annis, C. G. J.; Wilson, D. A.; Schwartz, B. J.

    1983-01-01

    120 page report presents data on mechanical properties of cast nickelbased alloys for turbine blades operating in hydrogen and steam at high temperatures. Tests on alloys for hydrogen-burning engines of future are described.

  1. 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

  2. Fiber laser welding of nickel based superalloy Inconel 625

    NASA Astrophysics Data System (ADS)

    Janicki, Damian M.

    2013-01-01

    The paper describes the application of single mode high power fiber laser (HPFL) for the welding of nickel based superalloy Inconel 625. Butt joints of Inconel 625 sheets 0,8 mm thick were laser welded without an additional material. The influence of laser welding parameters on weld quality and mechanical properties of test joints was studied. The quality and mechanical properties of the joints were determined by means of tensile and bending tests, and micro hardness tests, and also metallographic examinations. The results showed that a proper selection of laser welding parameters provides non-porous, fully-penetrated welds with the aspect ratio up to 2.0. The minimum heat input required to achieve full penetration butt welded joints with no defect was found to be 6 J/mm. The yield strength and ultimate tensile strength of the joints are essentially equivalent to that for the base material.

  3. Leather Coated with Mixtures of Humectant and Antioxidants to Improve UV and Heat Resistance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ultraviolet (UV) and heat resistance are very important qualities for leather products. We recently developed an environmentally friendly finishing process for improving the UV- and heat resistance of automobile upholstery leather. We previously reported and demonstrated some promising results fro...

  4. 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

  5. Testing Method for Heat Resistance Under Temperature Gradient

    NASA Astrophysics Data System (ADS)

    Takagi, K.; Kawasaki, A.; Itoh, Y.; Harada, Y.; Ono, F.

    2007-12-01

    “Testing Method for Heat Resistance under Temperature Gradient” is a Japanese Industrial Standard (JIS) newly established by the Minister of Economy, Trade and Industry, after deliberations by the Japanese Industrial Standards Committee, in accordance with the Industrial Standardization Law. This standard specified the testing method for heat resistance under temperature gradient of materials and coated members of equipment exposed to high temperature, such as aircraft engines, gas turbines, and so on. This paper introduces the principle and overview of the established standard. In addition, taking the heat cycle test using the burner rig for instance, we specifically illustrate the acquirable data and their analysis in the standard. Monitoring of the effective thermal conductivity and acoustic emission particularly enables to the non-destructive evaluation of failure cycle.

  6. Elevated temperature creep-rupture behavior of the single crystal nickel-base superalloy NASAIR 100

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    The creep and rupture behavior of 001-line-oriented single crystals of the nickel-base superalloy NASAIR 100 was investigated at temperatures of 925 and 1000 C. In the stress and temperature ranges studied, the steady state creep rate, time to failure, time to the onset of secondary creep, and the time to the onset of tertiary creep all exhibited power law dependencies on the applied stress. The creep rate exponents for this alloy were between seven and eight, and the modulus-corrected activation energy for creep was approximately 350 kjoule/mole, which was comparable to the measured activation energy for Ostwald ripening of the gamma-prime precipitates. Oriented gamma-prime coarsening to form lamellae perpendicular to the applied stress was very prominent during creep. At 1000 C, the formation of a continuous gamma-gamma-prime lamellar structure was completed during the primary creep stage. Shear through the gamma-gamma-prime interface is considerd to be the rate limiting step in the deformation process. Gradual thickening of the lamellae appeared to be the cause of the onset of tertiary creep. At 925 C, the fully developed lamellar structure was not achieved until the secondary or tertiary creep stages. At this temperature, the gamma-gamma-prime lamellar structure did not appear to be as beneficial for creep resistance as at the higher temperature.

  7. 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

  8. 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.

  9. 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.

  10. Effects of composition and testing conditions on oxidation behavior of four cast commercial nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Lowell, C. E.; Probst, H. B.

    1974-01-01

    Four cast nickel-base superalloys were oxidized at 1000 and 1100 C for times up to 100 hr in static air and a Mach 1 gas stream. The oxidation resistance was judged by weight change, metal thickness loss, depletion-zone formation, and oxide formation and morphology. The alloys which formed mostly nickel aluminate (NiAl2O4) and aluminum oxide (Al2O3) (B-1900, VIA, and to a lesser extent 713C) were more oxidation resistant. Poorer oxidation resistance was associated with the appearance of chromium sesquioxide (Cr2O3) and chromite spinel (738X). Refractory metal content had little effect on oxidation resistance. Refractory metals appeared in the scale as tapiolite (NiM2O6, where M represents the refractory metal). Thermal cycling in static air appeared to supply sufficient data for the evaluation of oxidation resistance, especially for alloys which form oxides of low volatility. For alloys of higher chromium levels with high propensities toward forming a chromium-bearing scale of higher volatility, testing under conditions of high gas velocity is necessary to assess fully the behavior of the alloy.