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Sample records for al cr ni

  1. Creep and Toughness of Cryomilled NiAl Containing Cr

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Aikin, Beverly; Salem, Jon

    2000-01-01

    NiAl-AlN + Cr composites were produced by blending cryomilled NiAl powder with approx. 10 vol % Cr flakes. In comparison to the as-consolidated matrices, hot isostatically pressed Cr-modified materials did not demonstrate any significant improvement in toughness. Hot extruded NiAl-AlN+10.5Cr, however, possessed a toughness twice that determine for the base NiAl-AlN alloy. Measurement of the 1200 to 1400 K plastic flow properties revealed that the strength of the composites was completely controlled by the properties of the NiAl-AlN matrices. This behavior could be successfully modeled by the Rule-of-Mixtures, where load is shed from the weak Cr to the strong matrix.

  2. Process development for Ni-Cr-ThO2 and Ni-Cr-Al-ThO2 sheet

    NASA Technical Reports Server (NTRS)

    Cook, R. C.; Norris, L. F.

    1973-01-01

    A process was developed for the production of thin gauge Ni-Cr-ThO2 sheet. The process was based on the elevated temperature deposition of chromium onto a wrought Ni-2%ThO2 sheet and subsequent high temperature diffusion heat treatments to minimize chromium concentration gradients within the sheet. The mechanical properties of the alloy were found to be critically dependent on those of the Ni-2%ThO2 sheet. A similar process for the production of a Ni-Cr-Al-ThO2 alloy having improved oxidation resistance was investigated but the non-reproducible deposition of aluminum from duplex Cr/Al packs precluded successful scale-up. The mechanical properties of the Ni-Cr-Al-ThO2 alloys were generally equivalent to the best Ni-Cr-ThO2 alloy produced in the programme.

  3. A sulfur segregation study of PWA 1480, NiCrAl, and NiAl alloys

    NASA Technical Reports Server (NTRS)

    Jayne, D. T.; Smialek, J. L.

    1993-01-01

    Some nickel based superalloys show reduced oxidation resistance from the lack of an adherent oxide layer during high temperature cyclic oxidation. The segregation of sulfur to the oxide-metal interface is believed to effect oxide adhesion, since low sulfur alloys exhibit enhanced adhesion. X ray Photoelectron Spectroscopy (XPS) was combined with an in situ sample heater to measure sulfur segregation in NiCrAl, PWA 1480, and NiAl alloys. The polished samples with a 1.5 to 2.5 nm (native) oxide were heated from 650 to 1100 C with hold times up to 6 hr. The sulfur concentration was plotted as a function of temperature versus time at temperature. One NiCrAl sulfur study was performed on the same casting used by Browning to establish a base line between previous Auger Electron Spectroscopy (AES) results and the XPS results of this study. Sulfur surface segregation was similar for PWA 1480 and NiCrAl and reached a maximum of 30 at% at 800 to 850 C. Above 900 C the sulfur surface concentration decreased to about 3 at% at 1100 C. These results are contrasted to the minimal segregation observed for low sulfur hydrogen annealed materials which exhibit improved scale adhesion.

  4. Hot Corrosion Performance of AlO-CrO/NiCoCrAlYTa and AlO/NiCoCrAlYTa Coatings Deposited by Atmospheric Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Tao, Chong; Wang, Lei; Cheng, Nailiang; Hu, Hengfa; Liu, Yang; Song, Xiu

    2016-04-01

    AlO-CrO/NiCoCrAlYTa and AlO/NiCoCrAlYTa coatings were deposited on 316L stainless steel substrate using atmospheric plasma spraying, respectively, in order to improve the oxidation and corrosion resistance. The hot corrosion performance of the coatings at 700 and 900 °C were studied, and the detailed microstructures and phase composition of the coatings were analyzed using x-ray diffraction, scanning electron microscope with energy dispersive spectrometer, and transmission electron microscope. The results show that both coatings are structurally featured by slatted layers, consisting of amorphous phase, Cr2O3, Ni3Al, and Al2O3. The hot corrosion resistance of AlO-CrO/NiCoCrAlYTa coating is better than that of AlO/NiCoCrAlYTa coating. This improvement is attributed to lower porosity and more compact Cr2O3 in AlO-CrO/NiCoCrAlYTa coating which performs better than Al2O3 in blocking further inward progress of corrosion and oxidization.

  5. Development and High Temperature Property Evaluation of Ni-Co-Cr-Al Composite Electroforms

    NASA Astrophysics Data System (ADS)

    Srivastava, Meenu; Siju; Balaraju, J. N.; Ravisankar, B.

    2015-05-01

    Ni-Co-Cr-Al composite electroforms were developed with cobalt content of 10 and 40 wt.%. Cr and Al nano-particles were suspended in sulphamate electrolyte and co-deposited in the Ni-Co matrices. The surface morphology was investigated using field emission scanning electron microscope and the composition analyzed by energy-dispersive x-ray analysis. The oxidation resistance of the electroforms was studied from 600 to 1000 °C. The weight gain of Ni-10 wt.%Co-Cr-Al was less (better oxidation resistance) compared to Ni-Cr-Al and Ni-40 wt.%Co-Cr-Al. The x-ray diffraction studies revealed that the oxidation product formed on the surface of Ni-Cr-Al and Ni-10 wt.%Co-Cr-Al consisted of NiO and Al2O3, while Ni-40 wt.%Co-Cr-Al comprised oxides such as NiCo2O4, CrO3, CoO, NiO, and Al2O3. The hot corrosion behavior was investigated in 75%Na2SO4 + 25%NaCl environment at 800 °C. It was found that the hot corrosion resistance of the composite coating improved with increase in cobalt content. The probable composition suitable for high-temperature applications was found to be Ni-10 wt.%Co-Cr-Al.

  6. NiAl-based Polyphase in situ Composites in the NiAl-Ta-X (X = Cr, Mo, or V) Systems

    NASA Technical Reports Server (NTRS)

    Johnson, D. R.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

    1995-01-01

    Polyphase in situ composites were generated by directional solidification of ternary eutectics. This work was performed to discover if a balance of properties could be produced by combining the NiAl-Laves phase and the NiAl-refractory metal phase eutectics. The systems investigated were the Ni-Al-Ta-X (X = Cr, Mo, or V) alloys. Ternary eutectics were found in each of these systems and the eutectic composition, temperature, and morphology were determined. The ternary eutectic systems examined were the NiAl-NiAlTa-(Mo, Ta), NiAl-(Cr, Al) NiTa-Cr, and the NiAl-NiAlTa-V systems. Each eutectic consists of NiAl, a C14 Laves phase, and a refractory metal phase. Directional solidification was performed by containerless processing techniques in a levitation zone refiner to minimize alloy contamination. Room temperature fracture toughness of these materials was determined by a four-point bend test. Preliminary creep behavior was determined by compression tests at elevated temperatures, 1100-l400 K. Of the ternary eutectics, the one in the NiAl-Ta-Cr system was found to be the most promising. The fracture toughness of the NiAl-(Cr, Al)NiTa-Cr eutectic was intermediate between the values of the NiAl-NiAlTa eutectic and the NiAl-Cr eutectic. The creep strength of this ternary eutectic was similar to or greater than that of the NiAl-Cr eutectic.

  7. NiAl(110)/Cr(110) interface: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Liu, W.; Li, J. C.; Zheng, W. T.; Jiang, Q.

    2006-05-01

    The optimal geometries, thermodynamic properties, and electronic structures of NiAl(110)/Cr(110) interface are studied using a first-principle density functional plane-wave ultrasoft pseudopotential method. Surface energies of different NiAl surfaces are compared with those obtained based on the classical broken-bond rule. Simulation results indicate that the structure of Ni and Al placed in the hollow sites of Cr atoms at the interface is more thermodynamically stable, and the NiCr bonding is dominated by 3d electrons of Ni and Cr. It is found that NiAl(110)/Cr(110) alloying could lower brittleness of NiAl compounds. With simulated values of adhesion work and interface energy for NiAl(110)/Cr(110) system, its mechanical and thermodynamic properties are also discussed.

  8. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids have been observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. It was postulated that the voids resulted from an excess number of oxygen vacancies near the oxide-metal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidations of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al,Cr)2O3 and Ni(Al,Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationships between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  9. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids were observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. The voids resulted from an excess number of oxygen vacancies near the oxidemetal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidation of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al, Cr)2O3 and Ni(Al, Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationship between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  10. Adherent Al2O3 scales formed on undoped NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    1987-01-01

    Changes in the spalling behavior of Al2O3 scales formed on an undoped NiCrAl alloy are described. Two samples of Ni-15Cr-13Al (wt pct), one a control and the other sanded, were subjected to 25 oxidation cycles. It is observed that adherent scales formed on the sanded sample; however, the control sample had speckled, spalled scales. The data reveal that the adherent scales are caused by repeated removal of surface layers after each oxidation cycle. It is determined that interfacial segregation of sulfur influences spallation and sulfur removal increases bonding. The effect of moisture on scale adhesions is investigated.

  11. Nanoscale Cellular Structures at Phase Boundaries of Ni-Cr-Al-Ti and Ni-Cr-Mo-Al-Ti Superalloys

    NASA Astrophysics Data System (ADS)

    Wang, Cong; Dunand, David C.

    2015-06-01

    The microstructural evolution of Ni-20 pct Cr wires was studied during pack cementation where Al and Ti, with and without prior cementation with Mo, are deposited to the surface of the Ni-Cr wires and subsequently homogenized in their volumes. Mo deposition promotes the formation of Kirkendall pores and subsequent co-deposition of Al and Ti creates a triple-layered diffusional coating on the wire surface. Subsequent homogenization drives the alloying element to distribute evenly in the wires which upon further heat treatment exhibit the γ + γ' superalloy structure. Unexpectedly, formation of cellular structures is observed at some of the boundaries between primary γ' grains and γ matrix grains. Based on additional features ( i.e., ordered but not perfectly periodic structure, confinement at γ + γ' phase boundaries as a cellular film with ~100 nm width, as well as lack of topologically close-packed phases), and considering that similar, but much larger, microstructures were reported in commercial superalloys, it is concluded that the present cellular structure solidified as a thin film, composed of eutectic γ + γ' and from which the γ' phase was subsequently etched, which was created by incipient melting of a region near the phase boundary with high solute segregation.

  12. High temperature oxidation resistant coatings for the directionally solidified Ni-Nb-Cr-Al eutectic superalloy

    NASA Technical Reports Server (NTRS)

    Strangman, T. E.; Ulion, N. E.; Felten, E. J.

    1977-01-01

    Protective coatings required for the Ni-Nb-Cr-Al directionally solidified eutectic superalloy were developed and evaluated on the basis of oxidation resistance, diffusional stability, thermal fatigue, and creep resistance. NiCrAlY+Pt and NiCrAlY physical vapor-deposition coating systems exhibited the best combination of properties. Burner-rig testing indicated that the useful life of a 127-micron-thick NiCrAlY+Pt coating exceeds 1000 h at 1366 K. Eutectic-alloy creep lives at 1311 K and a stress of 151.7 MN/sq m were greater for NiCrAlY+Pt-coated specimens than for uncoated specimens by a factor of two.

  13. Studies on the Sliding Wear Performance of Plasma Spray Ni-20Cr and Ni3Al Coatings

    NASA Astrophysics Data System (ADS)

    Kaur, Maninder; Singh, Harpreet; Singh, Balraj; Singh, Bhupinder

    2010-01-01

    Two metallic powders namely Ni-20Cr and Ni3Al were coated on AISI 309 SS steel by shrouded plasma spray process. The wear behavior of the bare, Ni-20Cr and Ni3Al-coated AISI 309 SS steel was investigated according to ASTM Standard G99-03 on a Pin-on-Disc Wear Test Rig. The wear tests were carried out at normal loads of 30 and 50 N with a sliding velocity of 1 m/s. Cumulative wear rate and coefficient of friction (μ) were calculated for all the cases. The worn-out surfaces were then examined by scanning electron microscopy analysis. Both the as-sprayed coatings exhibited typical splat morphology. The XRD analysis indicated the formation of Ni phase for the Ni-20Cr coating and Ni3Al phase for the Ni3Al coating. It has been concluded that the plasma-sprayed Ni-20Cr and Ni3Al coatings can be useful to reduce the wear rate of AISI 309 SS steel. The coatings were found to be adherent to the substrate steel during the wear tests. The plasma-sprayed Ni3Al coating has been recommended as a better choice to reduce the wear of AISI 309 SS steel, in comparison with the Ni-20Cr coating.

  14. Diffusional transport during the cyclic oxidation of gamma + beta, Ni-Cr-Al(Y, Zr) alloys

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Heckel, R. W.

    1988-01-01

    The cyclic oxidation behavior of several cast gamma + beta, Ni-Cr-Al(Y, Zr) alloys and one low-pressure plasma spraying gamma + beta, Ni-Co-Cr-Al(Y) alloy was studied. Cyclic oxidation was found to result in a decreasing Al concentration at the oxide-metal interface due to a high rate of Al consumption coupled with oxide scale cracking and spalling. Diffusion paths plotted on the ternary phase diagram showed higher Ni concentrations with increasing cyclic oxidation exposures. The alloy with the highest rate of Al consumption and the highest Al content underwent breakaway oxidation following 500 1-hr cycles at 1200 C.

  15. 1100 to 1500 K Slow Plastic Compressive Behavior of NiAl-xCr Single Crystals

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Darolia, Ram

    2003-01-01

    The compressive properties of near <001> and <111> oriented NiAl-2Cr single crystals and near <011> oriented NiAl-6Cr samples have been measured between 1100 and 1500 K. The 2Cr addition produced significant solid solution strengthening in NiAl, and the <111> and <001> single crystals possessed similar strengths. The 6Cr crystals were not stronger than the 2Cr versions. At 1100 and 1200 K plastic flow in all three Cr-modified materials was highly dependent on stress with exponents > 10. The <011> oriented 6Cr alloy exhibited a stress exponent of about 8 at 1400 and 1500 K; whereas both <001> and <111> NiAl-2Cr crystals possessed stress exponents near 3 which is indicative of a viscous dislocation glide creep mechanism. While the Cottrell-Jaswon solute drag model predicted creep rates within a factor of 3 at 1500 K for <001>-oriented NiAl-2Cr; this mechanism greatly over predicted creep rates for other orientations and at 1400 K for <001> crystals.

  16. Study of the effects of implantation on the high Fe-Ni-Cr and Ni-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Ribarsky, M. W.

    1985-01-01

    A theoretical study of the effects of implantation on the corrosion resistance of Fe-Ni-Cr and Ni-Cr-Al alloys was undertaken. The purpose was to elucidate the process by which corrosion scales form on alloy surfaces. The experiments dealt with Ni implanted with Al, exposed to S at high temperatures, and then analyzed using scanning electron microscopy, scanning Auger spectroscopy and X-ray fluorescence spectroscopy. Pair bonding and tight-binding models were developed to study the compositions of the alloys and as a result, a new surface ordering effect was found which may exist in certain real alloys. With these models, the behavior of alloy constituents in the presence of surface concentrations of O or S was also studied. Improvements of the models to take into account the important effects of long- and short-range ordering were considered. The diffusion kinetics of implant profiles at various temperatures were investigated, and it was found that significant non-equilibrium changes in the profiles can take place which may affect the implants' performance in the presence of surface contaminants.

  17. Microstructure of laser clad Ni- Cr- Al- Hf alloy on a γ' strengthened ni- base superalloy

    NASA Astrophysics Data System (ADS)

    Singh, Jogender; Mazumder, J.

    1988-08-01

    Alloys and coatings for alloys for improved high temperature service life under aggressive atmo-spheres are of great contemporary interest. There is a general consensus that the addition of rare earths such as Hf will provide many beneficial effects for such alloys. The laser cladding technique was used to produce Ni-Cr-AI-Hf alloys with extended solid solution of Hf. A 10 kW CO2 laser with mixed powder feed was used for laser cladding. Optical, scanning electron (SEM) and scanning transmission electron (STEM) microscopy were employed to characterize the microstructure of alloys produced during laser cladding processes. Microstructural studies revealed grain refinement, considerable in-crease in solubility of Hf in the matrix, Hf-rich precipitates, and new metastable phases. The size and morphology of γ' (Ni3Al) phase were discussed in relation to its microchemistry and the laser processing conditions. This paper will report the microstructural development in this laser clad Ni-Cr-AI-Hf alloy.

  18. Hot corrosion of Co-Cr, Co-Cr-Al, and Ni-Cr alloys in the temperature range of 700-750 deg C

    NASA Technical Reports Server (NTRS)

    Chiang, K. T.; Meier, G. H.

    1980-01-01

    The effect of SO3 pressure in the gas phase on the Na2SO4 induced hot corrosion of Co-Cr, Ni-Cr, and Co-Cr-Al alloys was studied in the temperature range 700 to 750 C. The degradation of the Co-Cr and Ni-Cr alloys was found to be associated with the formation of liquid mixed sulfates (CoSO4-Na2SO4 or NiSO4-Na2SO4) which provided a selective dissolution of the Co or Ni and a subsequent sulfidation oxidation mode of attack which prevented the maintenance of a protective Cr2O3 film. A clear mechanism was not developed for the degradation of Co-Cr-Al alloys. A pitting corrosion morphology was induced by a number of different mechanisms.

  19. Modeling degradation and failure of Ni-Cr-Al overlay coatings

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Heckel, R. W.

    1984-01-01

    Degradation of a Ni-16Cr-25Al-0.06Zr overlay coating on a Ni-22Cr substrate was examined after oxidation accompanied by thermal cycling. Concentration/distance profiles were measured in the coating and substrate after various one-hour cycles at 1150 C. A numerical model was developed to simulate coating degradation by simultaneous oxidation and coating/substrate interdiffusion. The validity of the model was confirmed by comparison of predicted and measured concentration/distance profiles. The ability of the model to identify critical system parameters was demonstrated for the case of the initial Al and Cr content of the coating and substrate.

  20. Synthesis and characterization of lamellar and fibre-reinforced NiAl-Mo and NiAl-Cr

    NASA Astrophysics Data System (ADS)

    Haenschke, T.; Gali, A.; Heilmaier, M.; Krüger, M.; Bei, H.; George, E. P.

    2010-07-01

    Directionally solidified (DS) alloys of the eutectic systems NiAl-10Mo and NiAl-34Cr (at.%) are potential candidates for high-temperature structural applications. Here, these alloys were first arc-melted and drop-cast. Thereafter, they were directionally solidified (DS) at growth rates of 20 and 80 mm/h while rotating at a fixed rotation speed of 60 revolutions per minute. Specimens of the DS alloys were tested in three-point-bending and uniaxial compression to obtain mechanical properties, including the ductile to brittle transition temperature (DBTT). For the NiAl-Cr system DBTT was found to be around 300 °C. Microstructural observations revealed that in the section perpendicular to the growth direction a uniform distribution of fibres was observed. The expected decrease of the fibre diameter with increasing growth rate was not observed. Instead, the fibre diameter slightly increased with increasing crystal growth rates. First compression tests were performed to get insights into the creep behaviour of these fibre-reinforced microstructures.

  1. Microstructure evolution during annealing of TiAl/NiCoCrAl multilayer composite prepared by EB-PVD

    SciTech Connect

    Zhang, Rubing; Zhang, Deming; Chen, Guiqing; Wang, Yuesheng

    2014-07-01

    TiAl/NiCoCrAl laminate composite sheet with a thickness of 0.4–0.6 mm as well as a dimension of 150 mm × 100 mm was fabricated successfully by using electron beam physical vapor deposition (EB-PVD) method. The annealing treatment was processed at 1123 and 1323 K for 3 h in a high vacuum atmosphere, respectively. The phase composition and microstructure of TiAl/NiCoCrAl microlaminated sheet have been analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Based on the sheet characterization and results of the microstructure evolution during annealing treatment process, the diffusion mechanism of interfacial reaction in TiAl/NiCoCrAl microlaminate was investigated and discussed.

  2. Effect of Microstructure on Creep in Directionally Solidified NiAl-31Cr-3Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, S. V.; Locci, I. E.

    2001-01-01

    The 1200 to 1400 K slow strain rate characteristics of the directionally solidified (DS) eutectic Ni-33Al-31Cr-3 Mo have been determined as a function of growth rate. While differences in the light optical level microstructure were observed in alloys grown at rates ranging from 7.6 to 508 mm/h, compression testing indicated that all had essentially the same strength. The exception was Ni-33 Al-31Cr-3Mo DS at 25.4 mm/h which was slightly stronger than the other growth velocities; no microstructural reason could be found for this improvement. Comparison of the approximately 1300 K properties revealed that four different DS NiAl-34(Cr,Mo) alloys have a similar creep resistance which suggests that there is a common, but yet unknown, strengthening mechanism.

  3. Effect of Microstructure on Creep in Directionally Solidified NiAl-31Cr-3Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.; Raj, S. V.; Locci, I. E.

    2001-01-01

    The 1200 to 1400 K slow strain rate characteristics of the directionally solidified (DS) eutectic Ni-33Al-31Cr-3 Mo have been determined as a function of growth rate. While differences in the light optical level microstructure were observed in alloys grown at rates ranging from 7.6 to 508 mm/h, compression testing indicated that all had essentially the same strength. The exception was Ni-33Al-31Cr-3Mo DS at 25.4 mm/h which was slightly stronger than the other growth velocities; no microstructural reason could be found for this improvement. Comparison of the approx. 1300 K properties revealed that four different DS NiAl-34(Cr,Mo) alloys have a similar creep resistance which suggests that there is a common, but yet unknown, strengthening mechanism.

  4. Deformation and annealing study of NiCrAlY

    NASA Technical Reports Server (NTRS)

    Ebert, L. J.; Trela, D. M.

    1978-01-01

    The elevated temperature properties (tensile and creep) of NiCrALY, a nickel base alloy containing nominally 16% chromium, 4% aluminum, and 2 to 3% yttria (Y2O3) were evaluated and the optimal combination of thermomechanical treatments for maximum creep resistance was determined. Stored strain energy in as-extruded bars (14:1 extrusion ratio) permitted the development of a large grain size in the material when it was annealed at the maximum safe temperature 2450 F (1343 C). With a one-hour anneal at this temperature, the relatively fine grain size of the as-extruded material was changed to one in which the average grain diameter approached 1 mm, and the aspect ratio was about 10. The material was capable of being cold worked (by rolling) in amounts greater than 30% reduction in area. When the cold worked material was given a relaxation treatment, consisting of heating one hour at 1600 F(871 C), and then a high temperature anneal at 2450 F (1343 C) for one hour, both the high temperature strength and the high temperature creep resistance of the material was further enhanced.

  5. Electrochemical deposition and microstructural characterization of AlCrFeMnNi and AlCrCuFeMnNi high entropy alloy thin films

    NASA Astrophysics Data System (ADS)

    Soare, V.; Burada, M.; Constantin, I.; Mitrică, D.; Bădiliţă, V.; Caragea, A.; Târcolea, M.

    2015-12-01

    Al-Cr-Fe-Mn-Ni and Al-Cr-Cu-Fe-Mn-Ni high entropy alloy thin films were prepared by potentiostatic electrodeposition and the microstructure of the deposits was investigated. The thin films were co-deposited in an electrolyte based on a DMF (N,N-dimethylformamide)-CH3CN (acetonitrile) organic compound. The energy dispersive spectrometry investigation (EDS) indicated that all the five respectively six elements were successfully co-deposited. The scanning electron microscopy (SEM) analysis revealed that the film consists of compact and uniform particles with particle sizes of 500 nm to 4 μm. The X-ray diffractometry (XRD) patterns indicated that the as-deposited thin films were amorphous. Body-centered-cubic (BCC) structures were identified by XRD after the films were annealed at various temperatures under inert Ar atmosphere. The alloys adhesion on the substrate was determined by the scratch-testing method, with higher values obtained for the Al-Cr-Cu-Fe-Mn-Ni alloy.

  6. The effect of yttrium and thorium on the oxidation behavior of Ni-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Kumar, A.; Douglass, D. L.; Nasrallah, M.

    1974-01-01

    The investigation reported included a determination of the optimum composition of a Ni-Cr-Al ternary alloy with respect to oxidation resistance and minimum film-spalling tendencies. Yttrium and thorium in small amounts were added to the ternary alloy and an investigation of the oxidation mechanism and the oxide scale adherence was conducted. It was found that the oxidation mechanism of Ni-Cr-Al ternary alloys depends upon the composition of the alloy as well as the time, oxygen pressure, and temperature of oxidation.

  7. Plasma-Sprayed High Entropy Alloys: Microstructure and Properties of AlCoCrFeNi and MnCoCrFeNi

    NASA Astrophysics Data System (ADS)

    Ang, Andrew Siao Ming; Berndt, Christopher C.; Sesso, Mitchell L.; Anupam, Ameey; S, Praveen; Kottada, Ravi Sankar; Murty, B. S.

    2015-02-01

    High entropy alloys (HEAs) represent a new class of materials that present novel phase structures and properties. Apart from bulk material consolidation methods such as casting and sintering, HEAs can also be deposited as a surface coating. In this work, thermal sprayed HEA coatings are investigated that may be used as an alternative bond coat material for a thermal barrier coating system. Nanostructured HEAs that were based on AlCoCrFeNi and MnCoCrFeNi were prepared by ball milling and then plasma sprayed. Splat studies were assessed to optimise the appropriate thermal spray parameters and spray deposits were prepared. After mechanical alloying, aluminum-based and manganese-based HEA powders revealed contrary prominences of BCC and FCC phases in their X-ray diffraction patterns. However, FCC phase was observed as the major phase present in both of the plasma-sprayed AlCoCrFeNi and MnCoCrFeNi coatings. There were also minor oxide peaks detected, which can be attributed to the high temperature processing. The measured porosity levels for AlCoCrFeNi and MnCoCrFeNi coatings were 9.5 ± 2.3 and 7.4 ± 1.3 pct, respectively. Three distinct phase contrasts, dark gray, light gray and white, were observed in the SEM images, with the white regions corresponding to retained multicomponent HEAs. The Vickers hardness (HV0.3kgf) was 4.13 ± 0.43 and 4.42 ± 0.60 GPa for AlCoCrFeNi and MnCoCrFeNi, respectively. Both type of HEAs coatings exhibited anisotropic mechanical behavior due to their lamellar, composite-type microstructure.

  8. Deformation and fracture of a directionally solidified NiAl-28Cr-6Mo eutectic alloy

    NASA Technical Reports Server (NTRS)

    Chen, X. F.; Johnson, D. R.; Noebe, R. D.; Oliver, B. F.

    1995-01-01

    A directionally solidified alloy based on the NiAl-(Cr, Mo) eutectic was examined by transmission and scanning electron microscopy to characterize the microstructure and room temperature deformation and fracture behavior. The microstructure consisted of a lamellar morphology with a group of zone axes (111) growth direction for both the NiAl and (Cr, Mo) phases. The interphase boundary between the eutectic phases was semicoherent and composed of a well-defined dislocation network. In addition, a fine array of coherent NiAl precipitates was dispersed throughout the (Cr, Mo) phase. The eutectic morphology was stable at 1300 K with only coarsening of the NiAl precipitates occurring after heat treatment for 1.8 ks (500 h). Fracture of the aligned eutectic is characterized primarily by a crack bridging/renucleation mechanism and is controlled by the strength of the semicoherent interface between the two phases. However, contributions to the toughness of the eutectic may arise from plastic deformation of the NiAl phase and the geometry associated with the fracture surface.

  9. Experimental study and thermodynamic modeling of the Al-Co-Cr-Ni system

    NASA Astrophysics Data System (ADS)

    Gheno, Thomas; Liu, Xuan L.; Lindwall, Greta; Liu, Zi-Kui; Gleeson, Brian

    2015-10-01

    A thermodynamic database for the Al-Co-Cr-Ni system is built via the Calphad method by extrapolating re-assessed ternary subsystems. A minimum number of quaternary parameters are included, which are optimized using experimental phase equilibrium data obtained by electron probe micro-analysis and x-ray diffraction analysis of NiCoCrAlY alloys spanning a wide compositional range, after annealing at 900 °C, 1100 °C and 1200 °C, and water quenching. These temperatures are relevant to oxidation and corrosion resistant MCrAlY coatings, where M corresponds to some combination of nickel and cobalt. Comparisons of calculated and measured phase compositions show excellent agreement for the β-γ equilibrium, and good agreement for three-phase β-γ-σ and β-γ-α equilibria. An extensive comparison with existing Ni-base databases (TCNI6, TTNI8, NIST) is presented in terms of phase compositions.

  10. Solute transport during the cyclic oxidation of Ni-Cr-Al alloys. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.

    1982-01-01

    Important requirements for protective coatings of Ni-Cr-Al alloys for gas turbine superalloys are resistance to oxidation accompanied by thermal cycling, resistance to thermal fatigue cracking. The resistance to oxidation accompanied by thermal cycling is discussed. The resistance to thermal fatigue cracking is also considered.

  11. Understanding phase stability of Al-Co-Cr-Fe-Ni high entropy alloys

    DOE PAGESBeta

    Zhang, Chuan; Zhang, Fan; Diao, Haoyan; Gao, Michael C.; Tang, Zhi; Poplawsky, Jonathan D.; Liaw, Peter K.

    2016-07-19

    The concept of high entropy alloy (HEA) opens a vast unexplored composition range for alloy design. As a well-studied system, Al-Co-Cr-Fe-Ni has attracted tremendous amount of attention to develop new-generation low-density structural materials for automobile and aerospace applications. In spite of intensive investigations in the past few years, the phase stability within this HEA system is still poorly understood and needs to be clarified, which poses obstacles to the discovery of promising Al-Co-Cr-Fe-Ni HEAs. In the present work, the CALPHAD approach is employed to understand the phase stability and explore the phase transformation within the Al-Co-Cr-Fe-Ni system. As a result,more » the phase-stability mapping coupled with density contours is then constructed within the composition - temperature space, which provides useful guidelines for the design of low-density Al-Co-Cr-Fe-Ni HEAs with desirable properties.« less

  12. Investigation of heat-resistant layered coating of Al-Cr-Ni

    NASA Astrophysics Data System (ADS)

    Shmorgun, V. G.; Trykov, Y. P.; Bogdanov, A. I.; Taube, A. O.

    2016-02-01

    The paper shows the transformation of the structure and phase composition of the layered coating system Al-Cr-Ni, obtained by the heat treatment of multilayered composite H20N80+AD1, welded by explosion, in the time range 1-300 hours. The cyclic heat resistance of the coating at 1150 ° C is studied.

  13. Phase-Specific Elastic/Plastic Interface Interactions in Layered Cr-NiAl Structures

    SciTech Connect

    Barabash, Rozaliya; Liu, W.; Tischler, Jonathan Zachary; Bei, Hongbin; Budai, John D

    2012-01-01

    The depth-dependent, as-grown and deformation-induced strain and dislocations partitioned through the interfaces in a two-phase layered NiAl-Cr(Mo) structure are directly measured at the mesoscale using 3-D X-ray microdiffraction. It is demonstrated that in the as-grown, undeformed state, neighboring submicron Cr solid solution and NiAl eutectic lamellae (doped with {approx}3% Mo) form a heterointerface with 180{sup o} rotation around a <1 1 2> pole. It is shown that the mechanical response to the indentation of a layered composite with alternating Cr(Mo)-NiAl lamellae is distinct from the response of single-phase materials. In the center of the indent, after the load is released, the NiAl lamellae are under compressive forward stresses (with the same sign as the indentation-induced compression) while Cr solid solution lamellae are under tensile back stresses (with opposite sign from the indentation load). The depth-dependent alternation of compressive/tensile residual strains in the neighboring Cr solid solution and NiAl lamellae is understood in the framework of the Mughrabi's composite model considering two types of structure elements: harder and softer regions. Under indentation, both kinds of lamellae are assumed to deform compatibly. After the load is released, residual forward stresses are formed in the harder lamellae, and back stresses are formed in the mechanically softer lamellae. Line-broadening analysis of the intensity distribution along the diffraction vector reveals a 15-times increase in dislocation density in the near-surface zone in the center of the indent. Such a large increase is typical for severe deformation.

  14. Microstructural observations in rapidly-solidified and heat-treated Ni3Al-Cr alloys

    NASA Technical Reports Server (NTRS)

    Carro, G.; Flanagan, W. F.

    1992-01-01

    The microstructural development following heat treatments of several rapidly-solidified Ni3Al-Cr and Ni3Al-Cr-B alloys is presented. Depending on composition, the as-solidified samples were either 100 percent gamma-prime phase - in the form of fine antiphase domains (APD) - or a mixture of gamma-prime (APDs) and beta phases. Upon annealing, the as-solidified microstructures transform to either APD-free gamma-prime or mixtures of gamma and gamma-prime phases. For those compositions where the quenched microstructures were 100 percent gamma-prime it was observed that APD coarsening followed conventional grain-growth kinetics, but when gamma phase precipitated on the APD boundaries the rate constant changed abruptly while the time exponent remained unaffected. It was also found that alloys containing critical amounts of chromium and boron are susceptible to precipitation of the boride Cr5B3.

  15. Kinetics of borided 31CrMoV9 and 34CrAlNi7 steels

    SciTech Connect

    Efe, Goezde Celebi; Ipek, Mediha; Ozbek, Ibrahim; Bindal, Cuma

    2008-01-15

    In this study, kinetics of borides formed on the surface of 31CrMoV9 and 34CrAlNi7 steels borided in solid medium consisting of Ekabor II at 850-900-950 deg. C for 2, 4, 6 and 8 h were investigated. Scanning electron microscopy and optical microscopy examinations showed that borides formed on the surface of borided steels have columnar morphology. The borides formed in the coating layer confirmed by X-ray diffraction analysis are FeB, Fe{sub 2}B, CrB, and Cr{sub 2}B. The hardnesses of boride layers are much higher than that of matrix. It was found that depending on process temperature and time the fracture toughness of boride layers ranged from 3.93 to 4.48 MPa m{sup 1/2} for 31CrMoV9 and from 3.87 to 4.40 MPa m{sup 1/2} for 34CrAlNi7 steel. Activation energy, growth rate and growth acceleration of boride layer calculated according to these kinetic studies revealed that lower activation energy results in the fast growth rate and high growth acceleration.

  16. Analysis of the microstructure of Cr-Ni surface layers deposited on Fe{sub 3}Al by TIG

    SciTech Connect

    Ma Haijun . E-mail: hjma123@mail.sdu.edu.cn; Li Yajiang; Wang Juan

    2006-12-15

    A series of Cr-Ni alloys were overlaid on a Fe{sub 3}Al surface by tungsten inert gas arc welding (TIG) technology. The microstructure of the Cr-Ni surface layers were analysed by means of optical metallography, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated that when the appropriate TIG parameters were used and Cr25-Ni13 and Cr25-Ni20 alloys were used for the overlaid materials, the Cr-Ni surface layers were crack-free. The matrix of the surface layer was austenite (A), pro-eutectoid ferrite (PF), acicular ferrite (AF), carbide-free bainite (CFB) and lath martensite (LM), distributed on the austenitic grain boundaries as well as inside the grains. The phase constituents of the Cr25-Ni13 surface layer were {gamma}-Fe, Fe{sub 3}Al, FeAl, NiAl, an Fe-C compound and an Fe-C-Cr compound. The microhardness of the fusion zone was lower than that of the Fe{sub 3}Al base metal and Cr25-Ni13 surface layer.

  17. Microstructure and Oxidation Resistance of NiCoCrAlYTa Coating by Low Pressure Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Liang, X.-H.; Zhou, K. S.; Liu, M.; Hong, R. J.; Deng, C. G.; Luo, S.; Chen, Z. K.

    The NiCoCrAlYTa coating was prepared on Ni-based single crystal super-alloys by low pressure plasma spraying (LPPS). The phases and microstructures for the coatings were characterized by X-ray diffraction and scanning electron microscopy, and the fracture toughness and micro-hardness for both coatings and substrate were also investigated. The relationship between coating properties and oxidation was analyzed. The result shows that elementary distribution of NiCoCrAlYTa coatings, which consists of γ-Ni, β-NiAl, γ'-Ni3Al, and CrCoTa phases, is much homogeneous. The composition changes with depth from the surface to substrate for the coatings. The micro-hardness of coatings is 350.8 HV0.3 and fracture toughness is 2.73 MPa m1/2. The oxidation resistance of coatings excelled than Ni-based single crystal super-alloys.

  18. The formation mechanism of eutectic microstructures in NiAl-Cr composites.

    PubMed

    Tang, Bin; Cogswell, Daniel A; Xu, Guanglong; Milenkovic, Srdjan; Cui, Yuwen

    2016-07-20

    NiAl-based eutectic alloys, consisting of an ordered bcc matrix (B2) and disordered bcc fibers (A2), have been a subject of intensive efforts aimed at tailoring the properties of many of the currently used nickel-based superalloys. A thermodynamic phase field model was developed on a thermodynamic foundation and fully integrated with a thermo-kinetic database of the Ni-Al-Cr ternary system to elucidate the resulting peculiar eutectic microstructure. Invoking a variation of the liquid/solid interfacial thickness with temperature, we simulated the characteristic sunflower-like eutectic microstructures in the NiAl-Cr composites, consistent with experimental observations. The mechanism that governs the formation of the peculiar eutectic morphology was envisioned from the modeled evolutions associated with six sequential steps. Our calculations show that the conditional spinodal decomposition occurring in sequence could further trim and revise the microstructure of the eutectics by generating fine-domain structures, thereby providing an additional method to explore the novel NiAl-based eutectic composites with tunable properties at elevated temperatures. PMID:27385194

  19. 1300 K Compressive Properties of Directionally Solidified Ni-33Al-33Cr-1Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, S. V.; Locci, Ivan E.

    2000-01-01

    The Ni-33Al-33Cr-1Mo eutectic has been directionally solidified by a modified Bridgeman technique at growth rates ranging from 7.6 to 508 mm/h to produce grain/cellular microstructures, containing alternating plates of NiAl and Cr alloyed with Mo. The grains had sharp boundaries for slower growth rates (< 12.7 mm/h), while faster growth rates (> 25.4 mm/h) lead to cells bounded by intercellular regions. Compressive testing at 1300 K indicated that alloys DS'ed at rates between 25.4 to 254 mm/h possessed the best strengths which exceed that for the as-cast alloy.

  20. The effect of zirconium on the cyclic oxidation of NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.; Khan, A. S.; Lowell, C. E.

    1981-01-01

    This paper examines results with cyclic oxidation tests of Ni(9-20) Cr(15-30) Al-(x)Zr alloys carried out at 1100 C and 1200 C in static air. The concentration of zirconium varies from 0 to 0.63 atomic percent. Significant aluminum penetration is found in metallographic and electron microscopic examination of oxidized surfaces. Small amounts of zirconium lead to minimal penetration, and with increased zirconium content pronounced oxide penetration is observed.

  1. Effects of ruthenium on phase separation in a model Ni-Al-Cr-Ru superalloy

    NASA Astrophysics Data System (ADS)

    Zhou, Yang; Isheim, Dieter; Hsieh, Gillian; Noebe, Ronald D.; Seidman, David N.

    2013-04-01

    The temporal evolution of a Ni-10.0Al-8.5Cr-2.0Ru (at.%) alloy aged at 1073 K was investigated using transmission electron microscopy (TEM) and atom-probe tomography. The γ‧(L12)-precipitate morphology is spheroidal through 256 h of ageing as a result of adding Ru, which decreases the lattice parameter misfit between the γ‧(L12)- and γ(f.c.c.)-phases. The addition of Ru accelerates the compositional evolution of the γ‧(L12)- and γ(f.c.c.)-phases, which achieve their equilibrium compositions after 0.25 h. Initially, Ru accelerates the partitioning of Ni and Cr to the γ(f.c.c.)-phase, and the partitioning of Al to the γ‧(L12)-phase, but after 0.25 h, Ru, which partitions to the γ(f.c.c.)-phase, decreases the partitioning of Ni and increases the partitioning of Al and Cr. The temporal evolution of the average radius, ⟨R(t)⟩, number density, volume fraction of the γ‧(L12)-precipitates, and the supersaturations of Ni, Al, Cr, and Ru in the γ(f.c.c.)- and γ‧(L12)-phases are compared in detail with predictions of coarsening models and PrecipiCalc simulations. Based on a spline function fitting procedure of the concentration profiles between the γ‧(L12)- and γ(f.c.c.)-phases, it is demonstrated that the temporal evolution of the normalized interfacial width, δ/⟨R(t)⟩ vs. ⟨R(t)⟩, of each element, decreases with increasing ageing time: δ is the interfacial width.

  2. Effects of Solute Concentrations on Kinetic Pathways in Ni-Al-Cr Alloys

    NASA Technical Reports Server (NTRS)

    Booth-Morrison, Christopher; Weninger, Jessica; Sudbrack, Chantal K.; Mao, Zugang; Seidman, David N.; Noebe, Ronald D.

    2008-01-01

    The kinetic pathways resulting from the formation of coherent gamma'-precipitates from the gamma-matrix are studied for two Ni-Al-Cr alloys with similar gamma'-precipitate volume fractions at 873 K. The details of the phase decompositions of Ni-7.5Al-8.5Cr at.% and Ni-5.2Al-14.2Cr at.% for aging times from 1/6 to 1024 h are investigated by atom-probe tomography, and are found to differ significantly from a mean-field description of coarsening. The morphologies of the gamma'-precipitates of the alloys are similar, though the degrees of gamma'-precipitate coagulation and coalescence differ. Quantification within the framework of classical nucleation theory reveals that differences in the chemical driving forces for phase decomposition result in differences in the nucleation behavior of the two alloys. The temporal evolution of the gamma'-precipitate average radii and the gamma-matrix supersaturations follow the predictions of classical coarsening models. The compositional trajectories of the gamma-matrix phases of the alloys are found to follow approximately the equilibrium tie-lines, while the trajectories of the gamma'-precipitates do not, resulting in significant differences in the partitioning ratios of the solute elements.

  3. The effect of ion implantation on the oxidation resistance of vacuum plasma sprayed CoNiCrAlY coatings

    NASA Astrophysics Data System (ADS)

    Jiang, Jie; Zhao, Huayu; Zhou, Xiaming; Tao, Shunyan; Ding, Chuanxian

    2012-11-01

    CoNiCrAlY coatings prepared by vacuum plasma spraying (VPS) were implanted with Nb and Al ions at a fluence of 1017 atoms/cm2. The effects of ion implantation on the oxidation resistance of CoNiCrAlY coatings were investigated. The thermally grown oxide (TGO) formed on each specimen was characterized by XRD, SEM and EDS, respectively. The results showed that the oxidation process of CoNiCrAlY coatings could be divided into four stages and the key to obtaining good oxidation resistance was to remain high enough amount of Al and promote the lateral growth of TGO. The implantation of Nb resulted in the formation of continuous and dense Al2O3 scale to improve the oxidation resistance. The Al implanted coating could form Al2O3 scale at the initial stage, however, the scale was soon broken and TGO transformed to non-protective spinel.

  4. Structure and composition of higher-rhenium-content superalloy based on La-alloyed Ni-Al-Cr

    SciTech Connect

    Kozlov, Eduard V.; Koneva, Nina A.; Nikonenko, Elena L.; Popova, Natalya A.; Fedorischeva, Marina V.

    2015-10-27

    The paper presents the transmission and scanning electronic microscope investigations of Ni-Al-Cr superalloy alloyed with additional Re and La elements. This superalloy is obtained by a directional solidification method. It is shown that such additional elements as Re and La result in formation of new phases in Ni-Al-Cr accompanied by considerable modifications of quasi-cuboid structure in its γ’-phase.

  5. TEM and SNMS studies of protective alumina scales on NiCrAlY-alloys.

    PubMed

    Clemens, D; Vosberg, V; Hobbs, W; Breuer, U; Quadakkers, W J; Nickel, H

    1996-06-01

    The effect of Si addition on the oxidation behaviour of NiCrAlY alloys in the temperature range 950 bis 1100 degrees C has been investigated. During isothermal oxidation oxide growth rates were practically independent of the Si-content. However during cyclic oxidation Si additions were beneficial. Si additions of 1-2(m)/(0) appeared to shift the onset for spallation to longer times. It was found that Si stabilizes the beta-phase and probably it suppresses the formation of metastable Al(2)O(3) modifications. PMID:15045347

  6. The oxidation behavior of Ni-Cr-Al-2ThO2 alloys at 1093 and 1204 C.

    NASA Technical Reports Server (NTRS)

    Seltzer, M. S.; Wilcox, B. A.; Stringer, J.

    1972-01-01

    A pack diffusion process has been developed which permits the introduction of nearly 6 wt % Al into solid solution in the near surface region of TDNiCr (Ni-20 wt % Cr-2 vol % ThO2) and Ni-20Cr. Alumina scales, adherent under cyclic heating and cooling conditions, were produced on TDNiCr-5.86Al upon exposure to an environment of 1330 N/sq m (10 torr) or 101,000 N/sq m (760 torr) air at temperatures of 1093 and 1204 C. While the same oxidation kinetics were observed in isothermal tests for Ni-14.6Cr-5.86Al as were obtained for the TDNiCr-5.86Al, the dispersion-strengthened alloy exhibited superior oxide scale adhesion during cyclic testing. At 1204 C, continuous weight gains were observed under all test conditions for TDNiCr-5.86Al, in contrast to the weight loss with time which occurred several hours after exposure of TDNiCr to an oxidizing environment. TDNiCr with an initial aluminum surface concentration of 4.95 wt % has nearly comparable oxidation resistance to the TDNiCr-5.86Al alloy.

  7. Amorphous structure and properties in laser-clad Ni-Cr-Al coating on Al-Si alloy

    NASA Astrophysics Data System (ADS)

    Liang, Gongying; Wong, T. T.; Su, J. Y.; Woo, C. H.

    1999-09-01

    A Ni-Cr-Al coating was clad by a 5 kW CO2 laser with different laser power on Al-Si alloy. Using transmission electron microscopy, a mixing microstructure containing Ni- based amorphous structures was observed in the laser clad zones. As the uniformity of chemical composition and temperature is poor in the laser cladding, the amorphous structure with some Ni3Al crystals coexisted in the cladding. According to the morphologies of Ni-based amorphous structures, the amorphous structure existed not only in the net-like boundaries surrounding the granular structure but also in the granular structure. The microhardness of the mixture amorphous structure is between HV 600 - 800, which is lower than that of crystal phases in the coating. A differential thermal analysis showed that Ni- based amorphous structure exhibits a higher initial crystallizing temperature (about 588 degree(s)C), which is slightly higher than that of the eutectic temperature of Al- Si alloy. The wear experimental results showed that some amorphous structure exist in the laser cladding can reduce the peeling of the granular phases from matrix, and improve the its wear resistance.

  8. The Temporal Evolution of the Nanostructure of a Model Ni-Al-Cr Superalloy

    NASA Technical Reports Server (NTRS)

    Sudbrack, Chantal K.; Yoon, Kevin E.; Noebe, Ronald D.; Seidman, David N.

    2004-01-01

    The early to the later stages of precipitation of ordered gamma'-precipitates (L1(sub 2)) in Ni-5.2 Al-14.2 Cr (at.%) are studied at 873 K. Precipitates with radii as small as 0.45 nm are characterized fully by three-dimensional atom-probe (3DAP) microscopy. Contrary to what is often assumed by theory or in models, the average precipitate composition is shown to evolve with time, such that solute concentrations decrease toward an equilibrium value given by the solvus lines. Power-law time dependencies of the number density, mean radius, and supersaturations of Al and Cr are discussed in light of theoretical predictions for Ostwald ripening.

  9. Synthesis of Waste Form in the Gd-Fe-Al-Ni-Mn-Cr-O System

    SciTech Connect

    Chae, S.C.; Jang, Y.N.; Bae, I.K.; Ryu, K.W.

    2006-07-01

    Poly-phase waste form which was the mixture of Gd{sub 3}Fe{sub 2}Al{sub 3}O{sub 12} and (Ni{sub x}Mn{sub 1-x})(Fe{sub y}Cr{sub 1-y}){sub 2}O{sub 4} was synthesized. Also, we are intended to examine phase relation and physicochemical properties of coexisted phases in the compositions and to confirm accommodation relation of elements and phases. Two types of phase series were observed: Garnet-perovskite-spinel and Garnet-spinel. The compositions of garnets and spinels were nonstoichiometric, and especially, this poly-phase ceramics may be in a good waste form. The excessive Gd in garnets indicated the immobilization of higher content of actinides. The nonstoichiometric compositions of garnet and spinel were attributed to the formation of perovskite in that perovskite contained Gd, Fe and Al from garnet and Cr from spinel. (authors)

  10. A study of the oxide dispersion and recrystallization in NiCrAl prepared from preoxidized powder

    NASA Technical Reports Server (NTRS)

    Glasgow, T. K.

    1975-01-01

    The sintered aluminum powder (SAP) technique of dispersion strengthening (formation of an oxide dispersion by preoxidation of metal powders) was applied to atomized powder of a nickel alloy containing, by weight, 17% Cr, 5% Al, and 0.2% Y. The SAP-NiCrAl alloy (without the ytterbium removed by oxdation) was worked by extrusion and rod rolling at 1205 C and by swaging at 760 C. Annealing treatments were applied after working to determine the recrystallization response. The NiCrAlY alloy, similarly prepared from atomized powder, but without a preoxidation treatment, was examined for comparison. The SAP-NiCrAl alloy exhibited oxide particle size and spacing much larger than that usually observed in oxide dispersion strengthened alloys; nonetheless, it was possible to achieve abnormal (secondary) recrystallization in the SAP-NiCrAl alloy as has been reported for other oxide dispersion strengthened alloys. In contrast, the unoxidized NiCrAlY alloy exhibited only primary recrystallization.

  11. Interface bonding of NiCrAlY coating on laser modified H13 tool steel surface

    NASA Astrophysics Data System (ADS)

    Reza, M. S.; Aqida, S. N.; Ismail, I.

    2016-06-01

    Bonding strength of thermal spray coatings depends on the interfacial adhesion between bond coat and substrate material. In this paper, NiCrAlY (Ni-164/211 Ni22 %Cr10 %Al1.0 %Y) coatings were developed on laser modified H13 tool steel surface using atmospheric plasma spray (APS). Different laser peak power, P p, and duty cycle, DC, were investigated in order to improve the mechanical properties of H13 tool steel surface. The APS spraying parameters setting for coatings were set constant. The coating microstructure near the interface was analyzed using IM7000 inverted optical microscope. Interface bonding of NiCrAlY was investigated by interfacial indentation test (IIT) method using MMT-X7 Matsuzawa Hardness Tester Machine with Vickers indenter. Diffusion of atoms along NiCrAlY coating, laser modified and substrate layers was investigated by energy-dispersive X-ray spectroscopy (EDXS) using Hitachi Tabletop Microscope TM3030 Plus. Based on IIT method results, average interfacial toughness, K avg, for reference sample was 2.15 MPa m1/2 compared to sample L1 range of K avg from 6.02 to 6.96 MPa m1/2 and sample L2 range of K avg from 2.47 to 3.46 MPa m1/2. Hence, according to K avg, sample L1 has the highest interface bonding and is being laser modified at lower laser peak power, P p, and higher duty cycle, DC, prior to coating. The EDXS analysis indicated the presence of Fe in the NiCrAlY coating layer and increased Ni and Cr composition in the laser modified layer. Atomic diffusion occurred in both coating and laser modified layers involved in Fe, Ni and Cr elements. These findings introduce enhancement of coating system by substrate surface modification to allow atomic diffusion.

  12. High temperature sulfidation of Fe{sub 3}Al and NiCr thermal spray coatings at 600 C

    SciTech Connect

    Luer, K.; DuPont, J.; Marder, A.

    1999-11-01

    Three Fe{sub 3}Al and two Ni45Cr thermal spray coatings were tested in Ar-3.5H{sub 2}-0.1H{sub 2}S for 500h at 600 C and compared to AISI 1008 steel. The three Fe{sub 3}Al-type coatings were processed from the same lot of gas atomized Fe{sub 3}Al powder using a high velocity oxygen fuel (HVOF) thermal spray process and an air plasma spray (APS) process. In general, the Fe{sub 3}Al-type composition displayed excellent resistance to sulfidation corrosion at 600 C which correlated with the reported literature on wrought Fe{sub 3}Al alloys. HVOF processing did not significantly degrade the composition of the consumable and produced coatings with low porosity, low oxide content, high sulfidation resistance, and high resistance to sulfur penetration. In contrast, APS processing caused significant degradation to the particles which reduced the sulfidation resistance of the coating and enabled local sulfidation attack at alloy depleted regions. The APS processed Fe{sub 3}Al coating also contained high porosity which enabled sulfur to fully penetrate the splat boundaries of the coating to the substrate. The two Ni45Cr-type coatings were produced using different processes and different consumables. One of the Ni45Cr coatings was processed using a proprietary wire combustion arc-spray (CAS) process. The second Ni45Cr coating was processed using a HVOF spray process. Both NiCr-type coatings reacted moderately with the sulfidizing gas at 600 C to form a mixed chromium oxide-sulfide scale despite marked differences in coating structure and composition. CAS processing caused significant degradation of the Ni45Cr consumable and produced a coating with low porosity and high oxide content. In contrast, HVOF processing caused negligible degradation of the Ni45Cr consumable and produced a coating with low porosity and moderate oxide content.

  13. Creep-fatigue behavior of NiCoCrAlY coated PWA 1480

    NASA Technical Reports Server (NTRS)

    Miner, R. V.; Gayda, J.; Hebsur, M. G.

    1985-01-01

    This study of high-temperature fatigue and creep-fatigue behavior is part of a program to identify the basic features of the effects of temperature, creep, fatigue, and environment on the behavior of a single crystal superalloy, a bulk coating alloy, and a coated alloy system. A system was selected which has had considerable production experience: the Ni-base superalloy, PWA 1480, and the NiCoCrAlY coating, PWA 276. Isothermal behavior was studied first. A series of fatigue and creep fatigue tests of the types commonly designated as pp, cp, pc and cc were conducted. These tests were conducted at various constant total strain ranges. The creep-fatigue cycles employed constant stress dwells at the maximum and/or minimum load. Test results are given.

  14. Effect of Cr on Microstructure and Properties of a Series of AlTiCr x FeCoNiCu High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Li, Anmin; Ma, Ding; Zheng, Qifeng

    2014-04-01

    A series of AlTiCr x FeCoNiCu ( x: molar ratio, x = 0.5, 1.0, 1.5, 2.0, 2.5) high-entropy alloys (HEAs) were prepared by vacuum arc furnace. These alloys consist of α-phase, β-phase, and γ-phase. These phases are solid solutions. The structure of α-phase and γ-phase is face-centered cubic structure and that of β-phase is body-centered cubic (BCC) structure. There are four typical cast organizations in these alloys such as petal organization (α-phase), chrysanthemum organization (α-phase + β-phase), dendrite (β-phase), and inter-dendrite (γ-phase). The solidification mode of these alloys is affected by Chromium. If γ-phase is not considered, AlTiCr0.5FeCoNiCu and AlTiCrFeCoNiCu belong to hypoeutectic alloys; AlTiCr1.5FeCoNiCu, AlTiCr2.0FeCoNiCu, and AlTiCr2.5FeCoNiCu belong to hypereutectic alloys. The cast organizations of these alloys consist of pro-eutectic phase and eutectic structure (α + β). Compact eutectic structure and a certain amount of fine β-phase with uniform distribution are useful to improve the microhardness of the HEAs. More γ-phase and the microstructure with similar volume ratio values of α-phase and β-phase improve the compressive strength and toughness of these alloys. The compressive fracture of the series of AlTiCr x FeCoNiCu HEAs shows brittle characteristics, suggesting that these HEAs are brittle materials.

  15. Predicting diffusion paths and interface motion in gamma/gamma + beta, Ni-Cr-Al diffusion couples

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Heckel, R. W.

    1987-01-01

    A simplified model has been developed to predict Beta recession and diffusion paths in ternary gamma/gamma + beta diffusion couples (gamma:fcc, beta: NiAl structure). The model was tested by predicting beta recession and diffusion paths for four gamma/gamma + beta, Ni-Cr-Al couples annealed for 100 hours at 1200 C. The model predicted beta recession within 20 percent of that measured for each of the couples. The model also predicted shifts in the concentration of the gamma phase at the gamma/gamma + beta interface within 2 at. pct Al and 6 at. pct Cr of that measured in each of the couples. A qualitative explanation based on simple kinetic and mass balance arguments has been given which demonstrates the necessity for diffusion in the two-phase region of certain gamma/gamma + beta, Ni-Cr-Al couples.

  16. Degradation of a TBC with HVOF-CoNiCrAlY Bond Coat

    NASA Astrophysics Data System (ADS)

    Chen, Weijie R.

    2014-06-01

    Thermal barrier coatings (TBCs) provide both thermal insulation and oxidation and corrosion protection to the substrate metal, and their durability is influenced by delamination near the interface between the ceramic topcoat and the metallic bond coat, where a layer of thermally grown oxide (TGO) forms during service exposure. In the present work, the degradation process of a TBC with an air-plasma-spray ZrO2-8 wt.%Y2O3 topcoat and a high-velocity oxy-fuel CoNiCrAlY bond coat was studied, in terms of TGO growth kinetics and aluminum depletion in the bond coat, as well as cracking behavior. The results show that the TGO growth kinetics can be described by a transient oxidation stage with δ3 = k 1 t followed by a steady-state oxidation stage with δ2 = c + k 2 t. Significant aluminum depletion was observed in the bond coat after extended thermal exposure; however, chemical failure of the bond coat did not occur even after the aluminum content near the TGO/CoNiCrAlY interface decreased to 4.5 at.%. A power-law relationship between the maximum crack length in the TBC and the TGO thickness was observed, which may serve as the basis for TBC life prediction.

  17. Deposition and Oxidation of Oxide-Dispersed CoNiCrAlY Bondcoats

    NASA Astrophysics Data System (ADS)

    Okada, Mitsutoshi; Vassen, Robert; Karger, Matthias; Sebold, Doris; Mack, Daniel; Jarligo, Maria Ophelia; Bozza, Francesco

    2014-01-01

    CoNiCrAlY powder and nano-size alumina powder were milled by a high-energy-attrition ball-mill, and an oxide-dispersed powder was produced with a mixed structure of metal and alumina in each particle. The oxide-dispersed bond coat powder was deposited by HVOF. Pores, however, were observed in the coating since the alumina was deposited without sufficient melting. Isothermal oxidation tests were carried out for the bond coat specimens at a temperature of 1373 K up to 1000 h in air. As a result, oxidation proceeded inside the coating, since oxygen penetrated through pores formed in the dispersed alumina. However, the authors find that another deposition using higher power levels led to a bond coat without pores. A commercially available oxide-dispersed CoNiCrAlY powder was also deposited by HVOF and VPS, and isothermal oxidation tests were performed. The analysis clarifies that the HVOF bond coat exhibited the thinnest thermally grown oxide than those of the VPS bond coat and conventional metallic bond coat. Furnace cycling tests were conducted using the specimens with an additional ceramic thermal-barrier coating. The specimen with the bond coat sprayed by VPS using commercial oxide-dispersed powder showed almost same number of cycles to delamination compared with the specimen with the conventional metal bond coat.

  18. 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.

  19. Comparison of the transformation temperature, microstructure and magnetic properties of Co-Ni-Al and Co-Ni-Al-Cr shape memory alloys

    NASA Astrophysics Data System (ADS)

    Dağdelen, Fethi; Malkoç, Türkan; Kök, Mediha; Ercan, Ercan

    2016-06-01

    In this study, two-phase Co-Ni-Al shape memory alloys that have drawn attention recently due to their technological applications were investigated. Co-Ni-Al and Co-Ni-Al-Cr alloys were produced by melting method in an arc-melter furnace and physical properties between alloys were compared. At the end of experimental measurements it was observed that chromium addition did not change the crystal structure of the Co-Ni-Al alloy, but decreased the martensitic transformation temperature, the most significant property of shape memory alloys. Moreover, there was no significant change in the microstructure of the Co-Ni-Al alloy with chromium addition, and the presence of the two phases determined by X-ray analysis was also determined by optical microscopy. There was no significant change in micro hardness values of the alloys, while important changes in the magnetic properties were determined. It was observed that the Curie temperature decreased by approximately 500 {}^{circ}C with chromium addition and a considerable decrease in the magnetic saturation value was also determined.

  20. Comparison of the transformation temperature, microstructure and magnetic properties of Co-Ni-Al and Co-Ni-Al-Cr shape memory alloys

    NASA Astrophysics Data System (ADS)

    Dağdelen, Fethi; Malkoç, Türkan; Kök, Mediha; Ercan, Ercan

    2016-06-01

    In this study, two-phase Co-Ni-Al shape memory alloys that have drawn attention recently due to their technological applications were investigated. Co-Ni-Al and Co-Ni-Al-Cr alloys were produced by melting method in an arc-melter furnace and physical properties between alloys were compared. At the end of experimental measurements it was observed that chromium addition did not change the crystal structure of the Co-Ni-Al alloy, but decreased the martensitic transformation temperature, the most significant property of shape memory alloys. Moreover, there was no significant change in the microstructure of the Co-Ni-Al alloy with chromium addition, and the presence of the two phases determined by X-ray analysis was also determined by optical microscopy. There was no significant change in micro hardness values of the alloys, while important changes in the magnetic properties were determined. It was observed that the Curie temperature decreased by approximately 500°C with chromium addition and a considerable decrease in the magnetic saturation value was also determined.

  1. Partition coefficients for Al, Ca, Ti, Cr, and Ni in olivine obtained by melting experiment on an LL6 chondrite

    NASA Technical Reports Server (NTRS)

    Miyamoto, M.; Mikouchi, T.; Mckay, G. A.

    1994-01-01

    We report the partition coefficients for Ca, Al, Ti, Cr, and Ni in olivine obtained through a series of melting experiments on an LL6 chondrite under varying conditions of temperature and oxygen fugacity. It is necessary to examine the variation of partition coefficients up to extremely reducing conditions in order to study meteoritic olivines. For Ca, Al, and Cr, the partition coefficients tend to decrease as temperature increases, but do not change even under extremely reducing conditions.

  2. Effect of Strain Rate on Deformation Behavior of AlCoCrFeNi High-Entropy Alloy by Nanoindentation

    NASA Astrophysics Data System (ADS)

    Tian, L.; Jiao, Z. M.; Yuan, G. Z.; Ma, S. G.; Wang, Z. H.; Yang, H. J.; Zhang, Y.; Qiao, J. W.

    2016-05-01

    In this study, nanoindentation tests with continuous stiffness measurement technique were measured to investigate the deformation behavior of a high-entropy alloy AlCoCrFeNi under different indentation strain rates at room temperature. Results suggest that the creep behavior exhibits remarkable strain rate dependence. In-situ scanning images showed a conspicuous pileup around the indents, indicating that an extremely localized plastic deformation occurred during the nanoindentation. Under different strain rates, elastic modulus basically remains unchanged, while the hardness decreases with increasing indentation depth due to the indentation size effect. Furthermore, the modulus and hardness of AlCoCrFeNi HEAs are greater than that of the Al x CoCrFeNi (x = 0.3,0.5) at the strain rate of 0.2 s-1 due to its higher negative enthalpy of mixing related to the atomic binding force, and the solid solution strengthening induced by the lattice distortion, respectively.

  3. Effect of Strain Rate on Deformation Behavior of AlCoCrFeNi High-Entropy Alloy by Nanoindentation

    NASA Astrophysics Data System (ADS)

    Tian, L.; Jiao, Z. M.; Yuan, G. Z.; Ma, S. G.; Wang, Z. H.; Yang, H. J.; Zhang, Y.; Qiao, J. W.

    2016-06-01

    In this study, nanoindentation tests with continuous stiffness measurement technique were measured to investigate the deformation behavior of a high-entropy alloy AlCoCrFeNi under different indentation strain rates at room temperature. Results suggest that the creep behavior exhibits remarkable strain rate dependence. In-situ scanning images showed a conspicuous pileup around the indents, indicating that an extremely localized plastic deformation occurred during the nanoindentation. Under different strain rates, elastic modulus basically remains unchanged, while the hardness decreases with increasing indentation depth due to the indentation size effect. Furthermore, the modulus and hardness of AlCoCrFeNi HEAs are greater than that of the Al x CoCrFeNi ( x = 0.3,0.5) at the strain rate of 0.2 s-1 due to its higher negative enthalpy of mixing related to the atomic binding force, and the solid solution strengthening induced by the lattice distortion, respectively.

  4. Optimization of the NiCrAl-Y/ZrO-Y2O3 thermal barrier system

    NASA Technical Reports Server (NTRS)

    Stecura, S.

    1985-01-01

    The effects of bond and thermal barrier coating compositions, thicknesses, and densities on air plasma spray deposited Ni-Cr-Al-Y/ZrO2-Y2O3 life were evaluated in cyclic furnace oxidation tests at temperatures from 1110 to 1220 C. An empirical relation was developed to give life as a function of the above parameters. The thermal barrier system tested which had the longest life consisted of Ni-35.0 wt% Cr-5.9 wt% Al-0.95 wt% Y bond coating and ZrO2-6.1 wt% Y2O3 thermal barrier coating.

  5. Performance of NiCrAlY Coatings Deposited by Oxyfuel Thermal Spraying in High Temperature Chlorine Environment

    NASA Astrophysics Data System (ADS)

    Habib, K. A.; Damra, M. S.; Carpio, J. J.; Cervera, I.; Saura, J. J.

    2014-10-01

    A microcrystalline Ni-22Cr-10Al-1Y (wt.%) coating was deposited on AISI 304 stainless steel by the oxyfuel thermal spray technique. The deposited coating was subjected to heat treatment to improve the microstructure characteristics and its corresponding high-temperature properties. The isothermal high-temperature corrosion behavior at 650 and 700 °C in synthetic air and in the presence of 1% Cl2 was investigated using thermogravimetric analysis, x-ray diffraction, and scanning electron microscopy with energy-dispersive x-ray spectroscopy. The results indicated that the deposited NiCrAlY coating possessed acceptable oxidation-corrosion resistance at 650 °C owing to the formation of extensive amounts of the protective oxide of Cr2O3; NiO and a lesser amount of a Cr1.12 Ni2,88 metallic phase are also formed. At 700 °C, the coating lost its protective characteristic because of the excessive consumption of thermodynamically stable phases by oxidation-chlorination process. In this case, the steel base and the coating were attacked by chlorine during the exposure time; the mass gain of the NiCrAlY coating was slightly higher and provided only a limited protection up to 11 h; thereafter, breakdown of the layer of oxides occurred and this is attributed to the formation of non-protective oxides mainly β-Fe2O3 and Fe21.33O32 and the depletion of chromium.

  6. Evaluation of Cyclic Oxidation and Hot Corrosion Behavior of HVOF-Sprayed WC-Co/NiCrAlY Coating

    NASA Astrophysics Data System (ADS)

    Somasundaram, B.; Kadoli, Ravikiran; Ramesh, M. R.

    2014-08-01

    Corrosion of metallic structural materials at an elevated temperature in complex multicomponent gas environments are potential problems in many fossil energy systems, especially those using coal as a feedstock. Combating these problems involves a number of approaches, one of which is the use of protective coatings. The high velocity oxy fuel (HVOF) process has been used to deposit WC-Co/NiCrAlY composite powder on two types of Fe-based alloys. Thermocyclic oxidation behavior of coated alloys was investigated in the static air as well as in molten salt (Na2SO4-60%V2O5) environment at 700 °C for 50 cycles. The thermogravimetric technique was used to approximate the kinetics of oxidation. WC-Co/NiCrAlY coatings showed a lower oxidation rate in comparison to uncoated alloys. The oxidation resistance of WC-Co/NiCrAlY coatings can be ascribed to the oxide layer of Al2O3 and Cr2O3 formed on the outermost surface. Coated alloys extend a protective oxide scale composed of oxides of Ni and Cr that are known to impart resistance to the hot corrosion in the molten salt environment.

  7. Influence of Cr and W alloying on the fiber-matrix interfacial shear strength in cast and directionally solidified sapphire NiAl composites

    NASA Technical Reports Server (NTRS)

    Asthana, R.; Tiwari, R.; Tewari, S. N.

    1995-01-01

    Sapphire-reinforced NiAl matrix composites with chromium or tungsten as alloying additions were synthesized using casting and zone directional solidification (DS) techniques and characterized by a fiber pushout test as well as by microhardness measurements. The sapphire-NiAl(Cr) specimens exhibited an interlayer of Cr rich eutectic at the fiber-matrix interface and a higher interfacial shear strength compared to unalloyed sapphire-NiAl specimens processed under identical conditions. In contrast, the sapphire-NiAl(W) specimens did not show interfacial excess of tungsten rich phases, although the interfacial shear strength was high and comparable to that of sapphire-NiAl(Cr). The postdebond sliding stress was higher in sapphire-NiAl(Cr) than in sapphire-NiAl(W) due to interface enrichment with chromium particles. The matrix microhardness progressively decreased with increasing distance from the interface in both DS NiAl and NiAl(Cr) specimens. The study highlights the potential of casting and DS techniques to improve the toughness and strength of NiAl by designing dual-phase microstructures in NiAl alloys reinforced with sapphire fibers.

  8. Wear and Corrosion Behavior of CoNiCrAlY Bond Coats

    NASA Astrophysics Data System (ADS)

    Rathod, W. S.; Khanna, A. S.; Rathod, R. C.; Sapate, S. G.

    2014-07-01

    The present study focusses on the wear and microstructural properties of CoNiCrAlY coatings fabricated on AISI 316L stainless steel substrate by using the (HVOF) and (CGDS) methods. A triobiological test was performed on the samples in order to understand the wear behaviour of thermally sprayed coatings. The microstructures of as-sprayed and worn out coatings were investigated by scanning electron microscopy. Coating hardness measurements were performed with nanoindentation. HVOF coating revealed lower hardness value in comparison with CGDS. Studies depicted better wear resistance of the CGDS sprayed with He, when compared to CGDS N2 and HVOF processing. Potentiodynamic polarization curves and tafel extrapolation experiments were carried at 7.5 pH value using 3.5 % NaCl as an electrolyte. Electrochemical studies depicted better corrosion resistance of the He processed coating when compared to N2 and HVOF processing.

  9. Crystallographic study of fatigue cracking in Ni{sub 3}Al(CrB) single crystal

    SciTech Connect

    Zhang, G.P.; Wang, Z.G.; Li, G.Y.; Wu, S.D.

    1997-03-01

    The effect of crystallographic orientation on the fatigue-crack initiation and propagation in Ni{sub 3}Al(CrB) single crystal was studied using a compact-tension specimen. Stage I crystallographic cracking and cleavage fracture were observed. Crystallographic cracking can occur on two or more {l_brace}111{r_brace} slip planes simultaneously. It was shown that the threshold stress intensity for crack initiation from the notch root exhibits a dependence on crystallographic orientation. In addition, an effect of orientation on microcracking behavior was also shown. The number of {l_brace}111{r_brace} planes intersecting with each other determines the different microscopic features on the cleavage fracture surface.

  10. High temperature damping behavior of plasma sprayed NiCoCrAlY coatings

    NASA Astrophysics Data System (ADS)

    Khor, K. A.; Chia, C. T.; Gu, Y. W.; Boey, F. Y. C.

    2002-09-01

    There is a trend to design the turbine coating and the substrate as in integral, layered, engineering assembly. Under the harsh environment of the turbine engine, a failure in one component can quickly lead to failure in other components. Materials that are used in structural applications are prone to mechanical vibration, which, when not attenuated, will lead to fatigue of components and shortening of life cycle. Therefore, it is necessary to examine the thermal stability and dynamic mechanical properties of coatings under dynamic conditions. In addition to these noise reduction and vibration amplitude control motivated objectives, however, mechanical energy dissipation processes also find intrinsic applications in cases for which a thorough understanding of the mechanisms responsible for the damping response of the material is required. This article describes the damping behavior and mechanisms that exist in plasma sprayed NiCoCrAlY coatings.

  11. Microstructure and Properties of FeAlCrNiMo x High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Li, X. C.; Dou, D.; Zheng, Z. Y.; Li, J. C.

    2016-06-01

    FeAlCrNiMo x high-entropy alloys were prepared. The effect of Mo content on the microstructure and the properties of the alloys were investigated. When the Mo content was 0.1, the alloys were composed of single BCC solid solution; when Mo content reaches 0.25, the alloys were composed of BCC solid solution and ordered B2 solid solution. When Mo content is more than 0.75, some σ phases emerged. The volume fraction of the second phase increases with the increasing Mo content, and the crystal grains became coarsening. The yield strength, fracture strength, and hardness increase with the increasing Mo content and reach 2252, 2612 MPa, and 1006 Hv, respectively. The magnetic transformation undergoes from the ferromagnetism to paramagnetism with the increasing Mo content. The saturation intensity and remnant magnetism are decreased with the increasing Mo content.

  12. Temporal Evolution of the Nanostructure and Phase Compositions in a Model Ni-Al-Cr Alloy

    NASA Technical Reports Server (NTRS)

    Sudbrack, Chantal K.; Yoon, Kevin E.; Seidman, David N.; Seidman, David N.

    2006-01-01

    In a Ni-5.2 Al-14.2 Cr at.% alloy with moderate solute supersaturations and a very small gamma/gamma prime lattice parameter misfit, the nanostructural and compositional pathways during gamma prime(L12) precipitation at 873 K are investigated using atom-probe tomography, conventional transmission electron microscopy, and hardness measurements. Nucleation of high number densities (N(sub v) greater than 10(sup 23) per cubic meters) of solute-rich precipitates (mean radius = [R] = 0.75 nm), with a critical nucleus composition of Ni-18.3 plus or minus 0.9 Al-9.3 plus or minus 0.7 Cr at.%, initiates between 0.0833 and 0.167 h. With increasing aging time (a) the solute concentrations decay in spheroidal precipitates ([R] less than 10 nm); (b) the observed early-stage coalescence peaks at maximum N(sub v) in coincidence with the smallest interprecipitate spacing; and (c) the reaction enters a quasi-stationary regime where growth and coarsening operate concomitantly. During this quasi-stationary regime, the c (face-centered cubic)-matrix solute supersaturations decay with a power-law dependence of about -1/3, while the dependencies of [R] and N(sub v) are 0.29 plus or minus 0.05 and -0.64 plus or minus 0.06 at a coarsening rate slower than model predications. Coarsening models allow both equilibrium phase compositions to be determined from the compositional measurements. The observed early-stage coalescence is discussed in further detail.

  13. Pretreatment effects on the morphology and properties of aluminum oxide thermally grown on NiCoCrAlY

    NASA Technical Reports Server (NTRS)

    Prakash, S.; Budhani, R.; Doerr, H. J.; Deshpandey, C. V.; Bunshah, R. F.

    1985-01-01

    The effect of pretreatments on the morphology and properties of aluminum oxide thermally grown from NiCoCrAlY was investigated. The goal was to optimize process steps to produce a highly adherent, continuous, and insulating aluminum oxide. Two pretreatments were carried out, one in vacuum (about 0.0001 Torr) at 1350 K for 5 h, and the other consisting of deposition of a 1-micron thick Al2O3 film by activated reactive evaporation. Samples were subsequently oxidized thermally at 1000 C for 50 h at 0.5 Torr oxygen pressure. The two pretreatments were carried out on electron-beam evaporation NiCoCrAlY, about 120 microns thick, deposited on a superalloy turbine blade substrate. The results showed that the thermally grown oxide was significantly different in microstructure, surface topography and in its adherence to the NiCoCrAlY for the two pretreatments. Optimum results were obtained by combining the two pretreatments to produce an adherent, continuous, and insulating oxide film on the NiCoCrAlY-coated superalloy substrate.

  14. Characterization and oxidation behavior of NiCoCrAlY coating fabricated by electrophoretic deposition and vacuum heat treatment

    NASA Astrophysics Data System (ADS)

    Li, Zhiming; Qian, Shiqiang; Wang, Wei

    2011-03-01

    Electrophoretic deposition (EPD) was showed to be a feasible and convenient method to fabricate NiCoCrAlY coatings on nickel based supperalloys. The microstructure and composition of the NiCoCrAlY coatings after vacuum heat treatment were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDAX). Isothermal-oxidation test was performed at 1100 °C in static air for 100 h. The results show that the major phases in electrophoretic deposited and vacuum heat treated NiCoCrAlY coating are γ-Ni and γ‧-Ni3Al phases, also there is an extremely small quantity of Al2O3 in the coating. Composition fluctuations occur in the coating and a certain amount of titanium diffuse from the superalloy substrate to the top of the coating during vacuum heat treatment. The oxidation test results exhibit that the oxidation kinetics of this coating has two typical stages. The protective oxide layer is mainly formed in the initial linear growth stage and then the oxide layer hinders further oxidation of the coating in the subsequent parabolic growth stage. The coating can effectively protect the superalloy substrate from oxidation. A certain amount of rutile TiO2 is formed in the coating during oxidation and it is adverse to the oxidation resistance of the coating.

  15. A magnetron sputtered microcrystalline β-NiAl coating for SC superalloys. Part I. Characterization and comparison of isothermal oxidation behavior at 1100 °C with a NiCrAlY coating

    NASA Astrophysics Data System (ADS)

    Hou, Shaojun; Zhu, Shenglong; Zhang, Tao; Wang, Fuhui

    2015-01-01

    A microcrystalline β-NiAl coating was prepared on a single-crystal (SC) superalloy substrate via magnetron sputtering and subsequent vacuum annealing. The grain sizes of the coating ranged from about 300 nm to 1 μm. A reference NiCrAlY coating, which was mainly comprised of γ‧-Ni3Al and α-Cr, was prepared by means of vacuum arc evaporation (VAE). Isothermal oxidation tests were carried out at 1100 °C in air for 50 h. Both coatings formed thin and adherent α-Al2O3 scales during tests, while the oxide scales on the bare superalloy primarily consisted of spinel (Ni,Co)Al2O4 with underlying α-Al2O3 scale. The parabolic rate constant of the NiAl-coated specimens was about one order of magnitude lower than that of the NiCrAlY coated specimens. After oxidation tests, only a small amount of γ‧ phase was detected at some columnar boundaries of the β-NiAl coating, and about 2/3 parts of the NiCrAlY coating transformed into γ phase which resolved the α-Cr precipitations, while an Al-depleted zone in thickness of about 10 μm formed beneath the TGO of the bare superalloy. Inter-diffusion zones and secondary reaction zones were observed on the specimens coated by either β-NiAl or NiCrAlY. The oxidation mechanism and microstructure evolvement of the specimens during high temperature exposures were discussed.

  16. A study of interdiffusion in beta + gamma/gamma + gamma prime Ni-Cr-Al. M.S. Thesis. Final Report

    NASA Technical Reports Server (NTRS)

    Carol, L. A.

    1985-01-01

    Ternary diffusion in the NiCrAl system at 1200 C was studied with beta + gamma/gamma + gamma prime infinite diffusion couples. Interdiffusion resulted in the formation of complex, multiphase diffusion zones. Concentration/distance profiles for Cr and Al in the phases present in the diffusion zone were measured after 200 hr. The Ni-rich portion of the NiCrAl phase diagram (1200 C) was also determined. From these data, bulk Cr and Al profiles were calculated and translated to diffusion paths on the ternary isotherm. Growth layer kinetics of the layers present in the diffusion zone were also measured.

  17. Microstructure and Properties of HVOF-Sprayed NiCrAlY Coatings Modified by Rare Earth

    NASA Astrophysics Data System (ADS)

    Chen, S. F.; Liu, S. Y.; Wang, Y.; Sun, X. G.; Zou, Z. W.; Li, X. W.; Wang, C. H.

    2014-06-01

    Rare earth (RE)-modified NiCrAlY powders were prepared by ultrasonic gas atomization and deposited on stainless steel substrate by high-velocity oxygen fuel spraying. The effects of the RE on the microstructure, properties, and thermal shock resistance of the NiCrAlY coatings were investigated. The results showed that the NiCrAlY powders were refined and distributed uniformly after adding RE, while the number of unmelted particles in the coatings was reduced. Moreover, the RE-modified coatings showed improved microhardness and distribution uniformity. The microhardness of the coating reached a maximum after adding 0.9 wt.% RE, being 34.4 % higher than that of coatings without RE. The adhesive strength increased and reached a maximum after adding 0.6 wt.% RE, being 18.8 % higher than that of coatings without RE. Excessive RE decreased the adhesive strength. The thermal cycle life of NiCrAlY coatings increased drastically with RE addition. The coating with 0.9 wt.% RE showed optimum thermal shock resistance, being 21.2 % higher than that of coatings without RE.

  18. Strain rate sensitivity of nanoindentation creep in an AlCoCrFeNi high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Jiao, Z. M.; Wang, Z. H.; Wu, R. F.; Qiao, J. W.

    2016-09-01

    Creep behaviors of an AlCoCrFeNi high-entropy alloy with the body-centered cubic structure were investigated by nanoindentation. The enhanced strain gradient induced by higher strain rate leads to decreased strain rate sensitivity during creep process. The present alloy exhibits excellent creep resistance, mainly due to its large entropy of mixing and highly distorted lattice structure.

  19. Microstructure and mechanical properties of NiCoCrAlYTa alloy processed by press and sintering route

    SciTech Connect

    Pereira, J.C.; Zambrano, J.C.; Afonso, C.R.M.; Amigó, V.

    2015-03-15

    Nickel-based superalloys such as NiCoCrAlY are widely used in high-temperature applications, such as gas turbine components in the energy and aerospace industries, due to their strength, high elastic modulus, and high-temperature oxidation resistance. However, the processing of these alloys is complex and costly, and the alloys are currently used as a bond coat in thermal barrier coatings. In this work, the effect of cold press and sintering processing parameters on the microstructure and mechanical properties of NiCoCrAlY alloy were studied using the powder metallurgy route as a new way to obtain NiCoCrAlYTa samples from a gas atomized prealloyed powder feedstock. High mechanical strength and adequate densification up to 98% were achieved. The most suitable compaction pressure and sintering temperature were determined for NiCoCrAlYTa alloy through microstructure characterization. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive spectroscopy microanalysis (EDS) were performed to confirm the expected γ-Ni matrix and β-NiAl phase distribution. Additionally, the results demonstrated the unexpected presence of carbides and Ni–Y-rich zones in the microstructure due to the powder metallurgy processing parameters used. Thus, microhardness, nanoindentation and uniaxial compression tests were conducted to correlate the microstructure of the alloy samples with their mechanical properties under the different studied conditions. The results show that the compaction pressure did not significantly affect the mechanical properties of the alloy samples. In this work, the compaction pressures of 400, 700 and 1000 MPa were used. The sintering temperature of 1200 °C for NiCoCrAlYTa alloy was preferred; above this temperature, the improvement in mechanical properties is not significant due to grain coarsening, whereas a lower temperature produces a decrease in mechanical properties due to high porosity and

  20. Stepwise Depletion of Coating Elements as a Result of Hot Corrosion of NiCrAlY Coatings

    NASA Astrophysics Data System (ADS)

    Rana, Nidhi; Jayaganthan, R.; Prakash, Satya

    2013-11-01

    Present investigation deals with the hot corrosion behaviour of the NiCrAlY coatings deposited by HVOF technique on Superni76 under cyclic conditions at 900 °C in the presence of Na2SO4 + 60% V2O5 salt. The weight change behaviour of the coatings was followed with time up to 200 cycles and K p value was calculated for the hot corrosion process. Surface and cross-section of the corroded samples were examined by FESEM/EDS and XRD to follow the progress of corrosion up to 200 cycles. In earlier cycles, the corrosive species oxidised top surface of the coatings. With increasing number of cycles, oxidation of the coatings occurred up to 40-μm depth. A Cr-depleted band was seen below the oxide scale. Further increase in number of cycles led to migration and oxidation of Al to form Al2O3 sublayer at coating/scale interface, thereby leading to formation of Al-depleted zone in the coating below the Al2O3 sublayer. The corrosion resistance of the NiCrAlY coatings is attributed to the formation of the continuous and dense Al2O3 sublayer at the coating/scale interface, which acts as barrier to the migration of Cr to the surface. The appearance of Al3Y after 100 and 200 cycles also contributes to the increased corrosion resistance of coatings after 100 and 200 cycles.

  1. Effects of Tantalum on the Temporal Evolution of a Model Ni-Al-Cr Superalloy During Phase Decomposition

    NASA Technical Reports Server (NTRS)

    Booth, Morrison, Christopher; Seidman, David N.; Noebe, Ronald D.

    2009-01-01

    The effects of a 2.0 at.% addition of Ta to a model Ni-10.0Al-8.5Cr (at.%) superalloy aged at 1073 K are assessed using scanning electron microscopy and atom-probe tomography. The gamma'(Ll2)-precipitate morphology that develops as a result of gamma-(fcc)matrix phase decomposition is found to evolve from a bimodal distribution of spheroidal precipitates, to {001}-faceted cuboids and parallelepipeds aligned along the elastically soft {001}-type directions. The phase compositions and the widths of the gamma'-precipitate/gamma-matrix heterophase interfaces evolve temporally as the Ni-Al-Cr-Ta alloy undergoes quasi-stationary state coarsening after 1 h of aging. Tantalum is observed to partition preferentially to the gamma'-precipitate phase, and suppresses the mobility of Ni in the gamma-matrix sufficiently to cause an accumulation of Ni on the gamma-matrix side of the gamma'/gamma interface. Additionally, computational modeling, employing Thermo-Calc, Dictra and PrecipiCalc, is employed to elucidate the kinetic pathways that lead to phase decomposition in this concentrated Ni-Al-Cr-Ta alloy.

  2. Corrosion of NiCoCrAlY Coatings and TBC Systems Subjected to Water Vapor and Sodium Sulfate

    NASA Astrophysics Data System (ADS)

    Eriksson, Robert; Yuan, Kang; Li, Xin-Hai; Lin Peng, Ru

    2015-08-01

    Thermal barrier coating (TBC) systems are commonly used in gas turbines for protection against high-temperature degradation. Penetration of the ceramic top coat by corrosive species may cause corrosion damage on the underlying NiCoCrAlY bond coat and cause failure of the TBC system. In the current study, four oxidation/corrosion conditions were tried: (i) lab air, (ii) water vapor, (iii) sodium sulfate deposited on the specimens, and (iv) water vapor + sodium sulfate. The test was done at 750 °C in a cyclic test rig with 48 h cycles. The corrosion damage was studied on NiCoCrAlY-coated specimens, thin APS TBC specimens, and thick APS TBC specimens. Water vapor was found to have very minor influence on the oxidation, while sodium sulfate increased the TGO thickness both for NiCoCrAlY specimens and TBC-coated specimens; the influence of the TBC thickness was found to be very small. Sodium sulfate promoted thicker TGO; more Cr-rich TGO; the formation of Y oxides, and internally, Y sulfides; pore formation in the coating as well as in the substrate; and the formation of a Cr-depleted zone in the substrate.

  3. Effects of a Tantalum Addition on the Morphological and Compositional Evolutions of a Model Ni-AL-Cr Superalloy

    NASA Technical Reports Server (NTRS)

    Booth-Morrison, Christopher; Seidman, David N.; Noebe, Ronald D.

    2008-01-01

    The effects of a 2.0 at.% addition of Ta to a model Ni-Al-Cr superalloy aged at 1073 K are assessed using scanning electron microscopy and atom-probe tomography. The addition of Ta results in appreciable strengthening, and the morphology is found to evolve from a bimodal distribution of spheroidal precipitates, to cuboidal precipitates aligned along the elastically soft <001>-type directions. Tantalum is observed to partition preferentially to the gamma -precipitate phase and decreases the mobility of Ni in the gamma- matrix sufficiently to cause an accumulation of Ni on the gamma-matrix side of the gamma -precipitate/gamma-matrix heterophase interface.

  4. The effect of zirconium on the isothermal oxidation of nominal Ni-14Cr-24Al alloys

    NASA Technical Reports Server (NTRS)

    Kahn, A. S.; Lowell, C. E.; Barrett, C. A.

    1980-01-01

    The isothermal oxidation of Ni-14Cr-24Al-xZr-type alloys was performed in still air at 1100, 1150, and 1200 C for times up to 200 hr. The zirconium content of the alloys varied from 0-0.63 atom percent (a/o). The oxidized surfaces were studied by optical microscopy, X-ray diffraction, and scanning electron microscopy. The base alloy was an alumina former with the zirconium-containing alloys also developing some ZrO2. The addition of zirconium above 0.066 a/o increased the rate of weight gain relative to the base alloy. Due to oxide penetratio, the weight gain increased with Zr content; however, the scale thickness did not increase. The Zr did increase the adherence of the oxide, particularly at 1200 C. The delta W/A vs. time data fit the parabolic model of oxidation. The specific diffusion mechanism operative could not be identified by analysis of the calculated activation energies. Measurements of the Al2O3 scale lattice constants yielded the same values for all alloys.

  5. Optimization of an oxide dispersion strengthened Ni-Cr-Al alloy for gas turbine engine vanes

    NASA Technical Reports Server (NTRS)

    Klarstrom, D. L.; Grierson, R.

    1975-01-01

    The investigation was carried out to determine the optimum alloy within the Ni-16Cr-Al-Y2O3 system for use as a vane material in advanced aircraft gas turbine engines. Six alloys containing nominally 4%, 5% and 6% Al with Y2O3 levels of 0.8% and 1.2% were prepared by mechanical attrition. Six small-scale, rectangular extrusions were produced from each powder lot for property evaluation. The approximate temperatures for incipient melting were found to be 1658 K (2525 F), 1644 K (2500 F) and 1630 K (2475 F) for the 4%, 5% and 6% aluminum levels, respectively. With the exception of longitudinal crystallographic texture, the eight extrusions selected for extensive evaluation either exceeded or were close to mechanical property goals. Major differences between the alloys became apparent during dynamic oxidation testing, and in particular during the 1366 K (2000 F)/500 hour Mach 1 tests carried out by NASA-Lewis. An aluminum level of 4.75% was subsequently judged to be optimum based on considerations of dynamic oxidation resistance, susceptibility to thermal fatigue cracking and melting point.

  6. Experimental Verification of the Theoretical Prediction of the Phase Structure of a Ni-Al-Ti-Cr-Cu Alloy

    NASA Technical Reports Server (NTRS)

    Wilson, A.; Bozzolo, G.; Noebe, R. D.; Howe, J. M.

    2002-01-01

    The Bozzolo-Ferrante-Smith (BFS) method for alloys was applied to the study of NiAl-based materials to assess the effect of alloying additions on structure. Ternary, quaternary and even pentalloys based on NiAl with additions of Ti, Cr and Cu were studied and experimental verification of the theoretical predictions including the phase structure of a Ni-Al-Ti-Cr-Cu alloy is presented. Two approaches were used, Monte Carlo simulations to determine low energy structures, and analytical calculations of the energy of high symmetry configurations which give physical insight into preferred structures. The energetics for site occupancy in ternary and quaternary systems were calculated leading to an indirect determination of solubility limits at 0 K. Precipitate formation with information concerning structure and lattice parameter were also 'observed' computationally and the general characteristics of a Ni-Al-Ti-Cr-Cu alloy were correctly predicted. The results indicate that the BFS method for alloys can be a useful tool for alloy design and can be used to complement experimental alloy design programs.

  7. Temperature-dependent phase-specific deformation mechanisms in a directionally solidified NiAl-Cr(Mo) lamellar composite

    DOE PAGESBeta

    Yu, Dunji; An, Ke; Chen, Xu; Bei, Hongbin

    2015-10-09

    Phase-specific thermal expansion and mechanical deformation behaviors of a directionally solidified NiAl–Cr(Mo) lamellar in situ composite were investigated by using real-time in situ neutron diffraction during compression at elevated temperatures up to 800 °C. Tensile and compressive thermal residual stresses were found to exist in the NiAl phase and Crss (solid solution) phase, respectively. Then, based on the evolution of lattice spacings and phase stresses, the phase-specific deformation behavior was analyzed qualitatively and quantitatively. Moreover, estimates of phase stresses were derived by Hooke's law on the basis of a simple method for the determination of stress-free lattice spacing in inmore » situ composites. During compressive loading, the NiAl phase yields earlier than the Crss phase. The Crss phase carries much higher stress than the NiAl phase, and displays consistent strain hardening at all temperatures. The NiAl phase exhibits strain hardening at relatively low temperatures and softening at high temperatures. During unloading, the NiAl phase yields in tension whereas the Crss phase unloads elastically. Additionally, post-test microstructural observations show phase-through cracks at room temperature, micro cracks along phase interfaces at 600 °C and intact lamellae kinks at 800 °C, which is due to the increasing deformability of both phases as temperature rises.« less

  8. Temperature-dependent phase-specific deformation mechanisms in a directionally solidified NiAl-Cr(Mo) lamellar composite

    SciTech Connect

    Yu, Dunji; An, Ke; Chen, Xu; Bei, Hongbin

    2015-10-09

    Phase-specific thermal expansion and mechanical deformation behaviors of a directionally solidified NiAl–Cr(Mo) lamellar in situ composite were investigated by using real-time in situ neutron diffraction during compression at elevated temperatures up to 800 °C. Tensile and compressive thermal residual stresses were found to exist in the NiAl phase and Crss (solid solution) phase, respectively. Then, based on the evolution of lattice spacings and phase stresses, the phase-specific deformation behavior was analyzed qualitatively and quantitatively. Moreover, estimates of phase stresses were derived by Hooke's law on the basis of a simple method for the determination of stress-free lattice spacing in in situ composites. During compressive loading, the NiAl phase yields earlier than the Crss phase. The Crss phase carries much higher stress than the NiAl phase, and displays consistent strain hardening at all temperatures. The NiAl phase exhibits strain hardening at relatively low temperatures and softening at high temperatures. During unloading, the NiAl phase yields in tension whereas the Crss phase unloads elastically. Additionally, post-test microstructural observations show phase-through cracks at room temperature, micro cracks along phase interfaces at 600 °C and intact lamellae kinks at 800 °C, which is due to the increasing deformability of both phases as temperature rises.

  9. Influence cobalt on microstructural and hardness property of Al-Zn-Mg-Cu-Fe-Cr-Ni P/ M alloys

    NASA Astrophysics Data System (ADS)

    Naeem, Haider T.; Mohammad, Kahtan S.; Hussin, Kamarudin; Rahmat, Azim; Bashirom, Nurhuda

    2015-05-01

    In this study, influence cobalt additives on the microstructural and hardness properties of an Al-Zn-Mg-Cu-Fe-Cr-Ni PM alloy undergone the retrogression and re-aging treatment were carried out. Green compacts pressed at 370 MPa were then sintered at temperature 650°C in argon atmosphere for two hours. The sintered compacts subjected to a homogenizing treated at 470°C for 1.5 hours then aged at 120°C for 24 hours and retrogressed at 180°C for 30 minutes, and then re-aged at 120°C for 24 hours. Microstructural results of the Al-Zn-Mg-Cu-Fe-Cr-Ni-Co alloys introduced an intermetallics compound in the matrix of alloy, identified as the Al5Co2, Al70Co20Ni10 and Al4Ni3 phases besides to the MgZn2 and Mg2Zn11 phases which produced of the precipitation hardening during heat treatment. These compounds with precipitates provided strengthening of dispersion that led to improved Vickers's hardness and dinsifications properties of the alloy. The highest Vickers hardness of aluminum alloy containing cobalt was gotten after applying the retrogression and re-aging treatment.

  10. Phase Evolution and Properties of Al2CrFeNiMo x High-Entropy Alloys Coatings by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Wu, Wei; Jiang, Li; Jiang, Hui; Pan, Xuemin; Cao, Zhiqiang; Deng, Dewei; Wang, Tongmin; Li, Tingju

    2015-10-01

    A series of Al2CrFeNiMo x ( x = 0 to 2.0 at.%) high-entropy alloys coatings was synthesized on stainless steel by laser cladding. The effect of Mo content on the microstructures and mechanical properties of Al2CrFeNiMo x coatings was studied. The results show that the laser clad layer consists of the cladding zone, bonding zone, and heat-affected zone. The Al2CrFeNiMo x coatings are composed of two simple body-center cubic phases and the cladding zone is mainly composed of equiaxed grains. When the content of Mo reaches 2 at.%, a eutectic structure is found in the interdendritic regions. The surface microhardness of the Al2CrFeNiMo2 coating is 678 HV, which is about three times higher than that of the substrate (243 HV). Compared with stainless steel, the wear resistance of the coatings has been improved greatly. The wear mass loss of the Al2CrFeNiMo alloy is 9.8 mg, which is much less than that of the substrate (18.9 mg) and its wear scar width is the lowest among the Al2CrFeNiMo x coatings, indicating that the wear resistance of the Al2CrFeNiMo is the best.

  11. Perfect cellular eutectic growth in directionally solidified NiAl-Cr(Mo) hypereutectic alloy

    NASA Astrophysics Data System (ADS)

    Shang, Zhao; Shen, Jun; Zhang, Jianfei; Wang, Lei; Fu, Hengzhi

    2012-09-01

    Cellular eutectic microstructures with fully lamellar morphology were observed in the directionally solidified Ni-31Al-32Cr-6Mo (at%) hypereutectic alloy at withdrawal rates of 15, 25 and 50 μm/s, but the morphologies of cellular microstructures did not change consecutively with increasing withdrawal rate. The growth interfaces were deep cellular at withdrawal rates of 15 and 50 μm/s, but it changed to be shallow cellular at rate of 25 μm/s. The reason is that the interface undercooling comes to minimum at the middle rate of 25 μm/s. If the interface undercooling decreases, the tendency of constitutional undercooling will be weaken. The small constitutional undercooling will increase the interface stability, so that the interface morphology changes from deep cellular to shallow cellular. The shallow cellular growth interface led to a perfect cellular eutectic microstructure, which was analogous to the planar eutectic microstructure. In this case, the widths of the intercellular regions were narrowest, no coarse or irregular plates existed at the cell boundaries, and the thicknesses of the lamellae were almost uniform. The properties of the alloy may be markedly improved.

  12. The effect of yttrium and thorium on the oxidation behavior of Ni-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Kumar, A.; Nasrallah, M.; Douglass, D. L.

    1974-01-01

    The effect of quaternary additions of 0.5% Y, 0.5 and 1.0% Th to a base alloy of Ni-10CR-5Al on the oxidation behavior and mechanism was studied during oxidation in air over the range of 1000 to 1200 C. The presence of yttrium decreased the oxidation kinetics slightly, whereas, the addition of thorium caused a slight increase. Oxide scale adherence was markedly improved by the addition of the quaternary elements. Although a number of oxides formed on yttrium containing alloys, quantitative X-ray diffraction clearly showed that the rate-controlling step was the diffusion of aluminum through short circuit paths in a thin layer of alumina that formed parabolically with time. Although the scale adherence of the yttrium containing alloy was considerably better than the base alloys, spalling did occur that was attributed to the formation of the voluminous YAG particles which grew in a mushroom-like manner, lifting the protective scale off the subrate locally. The YAG particles formed primarily at grain boundaries in the substrate in which the yttrium originally existed as YNi9.

  13. Superior Mechanical Properties of AlCoCrFeNiTi x High-Entropy Alloys upon Dynamic Loading

    NASA Astrophysics Data System (ADS)

    Jiao, Z. M.; Ma, S. G.; Chu, M. Y.; Yang, H. J.; Wang, Z. H.; Zhang, Y.; Qiao, J. W.

    2016-02-01

    High-entropy alloys with composition of AlCoCrFeNiTi x ( x: molar ratio; x = 0, 0.2, 0.4) under quasi-static and dynamic compression exhibit excellent mechanical properties. A positive strain-rate sensitivity of yield strength and the strong work-hardening behavior during plastic flows dominate upon dynamic loading in the present alloy system. The constitutive relationships are extracted to model flow behaviors by employing the Johnson-Cook constitutive model. Upon dynamic loading, the ultimate strength and fracture strain of AlCoCrFeNiTi x alloys are superior to most of bulk metallic glasses and in situ metallic glass matrix composites.

  14. Microstructure of Al2O3 scales formed on NiCrAl alloys. Ph.D. Thesis - Case Western Reserve Univ.

    NASA Technical Reports Server (NTRS)

    Smialek, J. L.

    1981-01-01

    The structure of transient scales formed on pure and Y or Zr-doped Ni-15Cr-13Al alloys oxidized for 0.1 hr at 1100 C was studied by the use of transmission electron microscopy. Crystallographically oriented scales were found on all three alloys, but especially for the Zr-doped NiCrAl. The oriented scales consisted of alpha-(Al,Cr)2O3, Ni(Al,Cr)2O4 and gamma-Al2O3. They were often found in intimate contact with each other such that the close-packed planes and directions of one oxide phase were aligned with those of another. The prominent structural features of the oriented scales were approximately equal to micrometer subgrains; voids, antiphase domain boundaries and aligned precipitates were also prevalent. Randomly oriented alpha-Al2O3 was also found and was the only oxide ever observed at the immediate oxide metal interface. These approximately 0.15 micrometer grains were populated by intragranular voids which decreased in size and number towards the oxide metal interface. A sequence of oxidation was proposed in which the composition of the growing scale changed from oriented oxides rich in Ni and Cr to oriented oxides rich in Al. At the same time the structure changed from cubic spinels to hexagonal corundums with apparent precipitates of one phase in the matrix of the other. Eventually randomly oriented pure alpha-Al2O3 formed as the stable oxide with an abrupt transition: there was no gradual loss of orientation, no gradual compositional change or no gradual decrease in precipitate density.

  15. Mechanical properties and permeability of hydrogen isotopes through CrNi35WTiAl alloy, containing radiogenic helium

    SciTech Connect

    Maksimkin, I.P.; Yukhimchuk, A.A.; Boitsov, I.Y.; Malkov, I.L.; Musyaev, R.K.; Baurin, A.Y.; Shevnin, E.V.; Vertey, A.V.

    2015-03-15

    The long-term contact of structural materials (SM) with tritium-containing media makes their properties in terms of kinetic permeability of hydrogen isotopes change. This change is the consequence of the defect formation in SM due to the result of {sup 3}He build-up generated by the radioactive decay of tritium dissolved in SM. This paper presents the experimental results concerning the permeability of hydrogen isotopes through CrNi35WTiAl alloy containing {sup 3}He and the impact of the presence of {sup 3}He and H on its mechanical properties. Tensile tests of cylindrical samples containing various concentrations of {sup 3}He (90, 230 and 560 appm) have been performed in inert and hydrogen atmospheres. The build-up of {sup 3}He has been made using the 'helium trick' technique. The maximal decrease in the plastic characteristics of the CrNi35WTiAl alloy occurs in samples with the highest {sup 3}He (560 appm) content at 873 K. The permeability of deuterium through the CrNi35WTiAl alloy in the initial state and that with 560 appm of {sup 3}He content was explored. The presence of this {sup 3}He concentration has shown an increase in deuterium permeability, evidently due to structural changes in the material under the impact of radiogenic helium.

  16. Development of a CuNiCrAl Bond Coat for Thermal Barrier Coatings in Rocket Combustion Chambers

    NASA Astrophysics Data System (ADS)

    Fiedler, Torben; Rösler, Joachim; Bäker, Martin

    2015-12-01

    The lifetime of rocket combustion chambers can be increased by applying thermal barrier coatings. The standard coating systems usually used in gas turbines or aero engines will fail at the bond coat/substrate interface due to the chemical difference as well as the different thermal expansion between the copper liner and the applied NiCrAlY bond coat. A new bond coat alloy for rocket engine applications was designed previously with a chemical composition and coefficient of thermal expansion more similar to the copper substrate. Since a comparable material has not been applied by thermal spraying before, coating tests have to be carried out. In this work, the new Ni-30%Cu-6%Al-5%Cr bond coat alloy is applied via high velocity oxygen fuel spraying. In a first step, the influence of different coating parameters on, e.g., porosity, amount of unmolten particles, and coating roughness is investigated and a suitable parameter set for further studies is chosen. In a second step, copper substrates are coated with the chosen parameters to test the feasibility of the process. The high-temperature behavior and adhesion is tested with laser cycling experiments. The new coatings showed good adhesion even at temperatures beyond the maximum test temperatures of the NiCrAlY bond coat in previous studies.

  17. Estimation of excess energies and activity coefficients for the penternary Ni-Cr-Co-Al-Mo system and its subsystems

    NASA Astrophysics Data System (ADS)

    Dogan, A.; Arslan, H.; Dogan, T.

    2015-06-01

    Using different prediction methods, such as the General Solution Model of Kohler and Muggianu, the excess energy and activities of molybdenum for the sections of the phase diagram for the penternary Ni-Cr-Co-Al-Mo system with mole ratios xNi/ xMo = 1, xCr/ xMo = 1, xCo/ xMo = 1, and xAl/ xMo = r = 0.5 and 1, were thermodynamically investigated at a temperature of 2000 K, whereas the excess energy and activities of Bi for the section corresponding to the ternary Bi-Ga-Sb system with mole ratio xGa/ xSb = 1/9 were thermodynamically investigated at a temperature of 1073 K. In the case of r = 0.5 and 1 in the alloys Ni-Cr-Co-Al-Mo, a positive deviation in the activity coefficient was revealed, as molybdenum content increased. Moreover, in the calculations performed in Chou's GSM model, the obtained values for excess Gibbs energies are negative in the whole concentration range of bismuth at 1073 K and exhibit the minimum of about -2.2 kJ/mol at the mole ratio xGa/ xSb = 1/9 in the alloy Bi-Ga-Sb.

  18. The Role of Rhenium on the Temporal Evolution of the Nanostructure of a Model Ni-Al-Cr-Re Superalloy

    NASA Technical Reports Server (NTRS)

    Yoon, Kevin E.; Noebe, Ronald D.; Seidman, David N.

    2004-01-01

    Rhenium (2 at.%) additions to a model Ni-8.5 at.% Cr-10 at.% Al alloy are studied with respect to its effects on the temporal evolution of the nanostructure and the partitioning behavior of the four elements between the gamma (fcc) and gamma' (L1(sub 2)) phases. Chemical evolution of this quaternary alloy aged at 1073 K from 0.25 to 264 h, is investigated by three-dimensional atom-probe (3DAP) microscopy. The morphology of gamma'-precipitates remains spheroidal, even at an aging time of 264 h. The results demonstrate that Re slows the coarsening of gamma'-precipitates, in comparison to the ternary Ni-10 at.% A1-8.5 at.% Cr alloy at 1073 K.

  19. Influence of Detonation Gun Spraying Conditions on the Quality of Fe-Al Intermetallic Protective Coatings in the Presence of NiAl and NiCr Interlayers

    NASA Astrophysics Data System (ADS)

    Senderowski, Cezary; Bojar, Zbigniew

    2009-09-01

    The paper presents results of detailed research of the application of detonation gun (D-gun) spraying process for deposition of Fe-Al intermetallic coatings in the presence of NiAl and NiCr interlayers. A number of D-gun experiments have been carried out with significant changes in spraying parameters which define the process energy levels (changes in volumes of the working and fuel gases, and the distance and frequency of spraying). These changes directly influenced the quality of the coatings. The initial results underlay the choice of the process parameters with the view to obtain the most advantageous of geometric and physical-mechanical properties of the coating material, interlayer and substrate. The metallurgical quality of the coatings was considered by taking into account grain morphology, the inhomogeneity of chemical content and phase structure, the cohesive porosity in the coating volume, and adhesive porosity in the substrate/interlayer/coating boundaries. The surface roughness level was also considered. It was found that the D-gun sprayed coatings are in all cases built with flat lamellar splats. The splats develop from powder particles which are D-gun transformed in their plasticity and geometry. A significant result of the optimization of D-gun spraying parameters is the lack of signs of melting of the material (even in microareas) while the geometry of the subsequently deposited grains is considerably changed and the adhesivity and cohesion of the layers proves to be high. This is considered as an undeniable proof of high plasticity of the D-gun formed Fe-Al intermetallic coating.

  20. Hot Corrosion Behavior of Low-Pressure Cold-Sprayed CoNiCrAlY Coatings

    NASA Astrophysics Data System (ADS)

    Zhang, L. W.; Ning, X. J.; Lu, L.; Wang, Q. S.; Wang, L.

    2016-02-01

    CoNiCrAlY coatings were deposited by low-pressure cold spraying and pre-oxidized in a vacuum environment, and its hot corrosion behavior in pure Na2SO4 and 75 wt.% Na2SO4 + 25 wt.% NaCl salts was investigated. The pre-oxidation treatment resulted in the formation of a dense and continuous α-Al2O3 scale on the coating surface. After being corroded for 150 h at 900 °C, the pre-oxidized coating exhibited better corrosion resistance to both salts than the as-sprayed coating. The presence of preformed Al2O3 scale reduced the consumption rate of aluminum, by delaying the formation of internal oxides and sulfides and promoting the formation of a denser and more adherent Al2O3 scale. Moreover, we investigated the corrosion mechanism of cold-sprayed CoNiCrAlY coatings in the two salts and discussed the effect of the pre-oxidation treatment.

  1. Characterization of Oxide Scales Formed on High-Velocity Oxyfuel-Sprayed Ni-Co-Cr-Al-Y + ReTa Coatings

    NASA Astrophysics Data System (ADS)

    Lee, D. B.; Ko, J. H.; Yi, J. H.

    2005-09-01

    A high-velocity oxyfuel-sprayed 30 wt.% Ni-20 wt.% Co-30 wt.% Cr-10 wt.% Al-2 wt.% Y-4 wt.% Re-4 wt.% Ta coating was oxidized between 1000 and 1200 °C for up to 200 h in air, and the oxide scales were examined. The dense, sprayed coating consisted mainly of Cr3Ni2, Ni3Al, Ni3Ta, Ni, NiO, Al5Y3O12, and Cr2O3. Intermetallics and some oxides formed during spraying. During oxidation, mainly αAl2O3, along with some Al5Y3O12, CoAl2O4, CoCr2O4, Ta2O5, and Ta2O2.2 formed on the coating. The preferential oxidation of Al to form the Al-rich scales resulted in the formation of an Al-depleted region beneath the scales. Rhenium, being the most noble element, was distributed throughout the oxide scale and the coating, without forming any independent oxides.

  2. Development and Evaluation of Directionally-Solidified NiAl/(CR,MO)-Based Eutectic Alloys for Airfoil Applications

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Locci, I. E.; Whittenberger, J. D.

    2001-01-01

    The results of recent efforts to develop directionally-solidified alloys based on the Ni-33Al-31Cr-3Mo eutectic composition are discussed. These developmental efforts included studying the effects of macroalloying and growth rates on microstructure formation as well as the elevated temperature compressive and tensile properties of these alloys. These observations revealed that contrary to conventional opinion, the cellular microstructure was stronger and tougher than the planar eutectic microstructure due to a microstructural refinement of the cell size and interlamellar spacing. The high temperature strengths of these alloys are compared with those of commercial superalloys and advanced NiAl single crystals. The implications of this research on airfoil manufacturing and applications are discussed.

  3. High-Temperature Oxidation and Oxide Scale Formation in Plasma-Sprayed CoNiCrAlYRe Coatings

    NASA Astrophysics Data System (ADS)

    Di Girolamo, Giovanni; Brentari, Alida; Blasi, Caterina; Pilloni, Luciano; Serra, Emanuele

    2014-11-01

    MCrAlY coatings are usually adopted to improve the environmental resistance of Ni-based superalloy components of turbine engines against high-temperature oxidation and hot corrosion. In this work, CoNiCrAlYRe coatings were produced by atmospheric plasma spraying. The coatings exhibited relatively low oxygen content and porosity. X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy analyses revealed that the high-temperature exposure at 1383 K (1110 °C) promoted the growth of an oxide scale on the top surface being composed of a continuous and dense Al2O3 inner layer followed by an outer mixed layer (Cr2O3 and spinels). The oxide scale was mainly composed of Al2O3, while the formation of mixed oxides occurred at lesser extent. After high-temperature exposure, the formation of internal oxides in some areas reduced the inter-lamellar cohesion, so that a decrease in microhardness was found.

  4. Effect of Withdrawal Rate and Gd on the Microstructures of Directionally Solidified NiAl-Cr(Mo) Hypereutectic Alloy

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Shen, Jun; Zhang, Yun-Peng; Guo, Lan-Lan

    2016-03-01

    The microstructures of Ni-31Al-32Cr-6Mo- xGd hypereutectic alloy were investigated at the withdrawal rates of 10 μm/s, 30 μm/s, and 90 μm/s. For the Gd-free hypereutectic alloy, the Cr(Mo) primary dendrites appear at the beginning of solidification when the withdrawal rate is 10 μm/s. As the solidification proceeds, the Cr(Mo) primary dendrite is eliminated, and the fully eutectic structure can be obtained in the steady-state zone. With increasing the withdrawal rate, the Cr(Mo) primary dendrites decrease gradually, and vanish at 90 μm/s. In addition, at a moderate withdrawal rate (30 μm/s), an optimum addition of Gd content (0.1 wt.%) results in the refinement of the microstructure, including the refinement of the eutectic cells and the intercellular region. Meanwhile, the new white phase ((Al x Gd1- x )2O3) appears in the boundary of the eutectic cells when the Gd content is not less than 0.1 wt.%.

  5. The effect of sulfur and zirconium co-doping on the oxidation of NiCrAl

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    1988-01-01

    The adhesion behavior of Al2O3 scales formed on NiCrAl+Zr alloys was examined as a function of both sulfur and zirconium doping levels. In general, very high levels of zirconium were required to counteract the detrimental effects of sulfur. A sulfur-zirconium adherence map was constructed, as determined from the oxidation and spalling behavior in 1100 C cyclic tests. For low sulfur alloys (less than 500 ppma), the amount of zirconium required for adherence at any given sulfur level can be described by Zr greater than 600 S(0.2) (in ppma). These results underscore the importance of sulfur to adhesion mechanisms and suggest that sulfur gettering is a first order effect of reactive element additions to MCrAl alloys.

  6. The effect of sulfur and zirconium Co-doping on the oxidation of NiCrAl

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    1987-01-01

    The adhesion behavior of Al2O3 scales formed on NiCrAl+Zr alloys was examined as a function of both sulfur and zirconium doping levels. In general, very high levels of zirconium were required to counteract the detrimental effects of sulfur. A sulfur-zirconium adherence map was constructed, as determined from the oxidation and spalling behavior in 1100 C cyclic tests. For low sulfur alloys, the amount of zirconium required for adherence at any given sulfur level can be described by Zr greater than 600 S sup 0.2 (in ppma). These results underscore the importance of sulfur to adhesion mechanisms and suggests that sulfur gettering is a first order effect of reactive element additions to MCrAl alloys.

  7. Microstructural stability of AlN diffusion barrier for nanocomposite Ni + CrAlYSiHfN coating on single crystal superalloy at high temperatures

    NASA Astrophysics Data System (ADS)

    Ren, Pan; Zhu, Shenglong; Wang, Fuhui

    2015-12-01

    An AlN interlayer was fabricated by filtered vacuum arc evaporation as a diffusion barrier (DB) between Ni + CrAlYSiHfN composite coating and K417G superalloy. Microstructure changes of the AlN DB were investigated after exposure at 1000 and 1100 °C. Amorphous structure was found in the as-deposited AlN DB, which went through crystallization when exposing at high temperature. The AlN DB suppressed interdiffusion between overlayer and substrate effectively after 200 h exposure at both 1000 °C and 1100 °C. A few substrate element precipitates were observed within the grain boundary of the AlN DB after exposure at 1100 °C for 200 h.

  8. Microstructure and properties of the Ti/Al2O3/NiCr composites fabricated by explosive compaction/cladding.

    PubMed

    Wang, Bingfeng; Xie, Fangyu; Wang, Bin; Luo, Xiaozhou

    2015-05-01

    Titanium/aluminum oxide/nickel chromium (Ti/Al2O3/NiCr) composite bar prepared by explosive compaction/cladding technique represents a new kind of sandwich-structural composites for medical application. Formation of the interfaces of Ti/Al2O3 and Al2O3/NiCr govern the properties of the composite material. The electrical resistivity and microstructure of the intermediate layer and the interfaces of the Ti/Al2O3/NiCr explosive compaction/cladding bar are investigated by means of four-point probe analysis, optical microscopy, scanning electron microscopy, electron microprobe analysis, and X-ray diffraction. The Ti/Al2O3/NiCr composite bar is characterized by the consolidated ceramic intermediate layer and the metallurgical bonding interfaces. The intermediate ceramic layer plays a role of insulation and thermal conductance in this composite. The average shear strength of the composite bar is about 9.36 MPa. The heat affected zone characterized by relatively larger sizes of grains is distinguished from the other part of the Ti tube. The intermetallics AlTi3 and Al0.9Ni4.22 are generated at the intermediate ceramic layer. Formation mechanism of the interfaces of the explosive compaction/cladding bar are described. PMID:25746277

  9. High temperature tensile and creep behaviour of low pressure plasma-sprayed Ni-Co-Cr-Al-Y coating alloy

    NASA Technical Reports Server (NTRS)

    Hebsur, M. G.; Miner, R. V.

    1986-01-01

    The high temperature tensile and creep behavior of low pressure plasma-sprayed plates of a typical Ni-Co-Cr-Al-Y alloy has been studied. From room temperature to 800 K, the Ni-Co-Cr-Al-Y alloy studied has nearly a constant low ductility and a high strength. At higher temperatures, it becomes weak and highly ductile. At and above 1123 K, the behavior is highly dependent on strain rate and exhibits classic superplastic characteristics with a high ductility at intermediate strain rates and a strain rate sensitivity of about 0.5. At either higher or lower strain rates, the ductility decreases and the strain rate sensitivities are about 0.2. In the superplastic deformation range, the activation energy for creep is 120 + or - 20 kJ/mol, suggesting a diffusion-aided grain boundary sliding mechanism. Outside the superplastic range, the activation energy for creep is calculated to be 290 + or - 20 kJ/mol.

  10. Tribological Properties of AlCrCuFeNi2 High-Entropy Alloy in Different Conditions

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Ma, Shengguo; Gao, Michael C.; Zhang, Chuan; Zhang, Teng; Yang, Huijun; Wang, Zhihua; Qiao, Junwei

    2016-07-01

    In order to understand the environmental effect on the mechanical behavior of high-entropy alloys, the tribological properties of AlCrCuFeNi2 are studied systematically in dry, simulated rainwater, and deionized water conditions against the Si3N4 ceramic ball at a series of different normal loads. The present study shows that both the friction and wear rate in simulated rainwater are the lowest. The simulated rainwater plays a significant role in the tribological behavior with the effect of forming passive film, lubricating, cooling, cleaning, and corrosion. The wear mechanism in simulated rainwater is mainly adhesive wear accompanied by abrasive wear as well as corrosive wear. In contrast, those in dry condition and deionized water are abrasive wear, adhesive wear, and surface plastic deformation. Oxidation contributes to the wear behavior in dry condition but is prevented in liquid condition. In addition, the phase diagram of Al x CrCuFeNi2 is predicted using CALPHAD modeling, which is in good agreement with the literature report and the present study.

  11. Evaluation of tribological behavior of Al-Co-Cr-Fe-Ni high entropy alloy using molecular dynamics simulation.

    PubMed

    Huang, Jen-Ching

    2012-01-01

    High-entropy alloys have been studied extensively for their excellent properties and performance, including outstanding strength and resistance to oxidation at high temperatures. This study employed molecular dynamics simulation to produce a high-entropy alloy containing an equal molar ratio of Al, Co, Cr, Fe, and Ni and investigated the tribological behavior of the material using a diamond tool in a vacuum environment. We also simulated a AlCoCrFeNi high-entropy alloy cooled from a high temperature molten state to 300 K in a high-speed quenching process to produce an amorphous microstructure. In a simulation of nanoscratching, the cutting force-distance curve of high-entropy alloys was used to evaluate work hardening and stick-slip. An increase in temperature was shown to reduce the scratching force and scratching resistance. Nanoscratching the high-entropy alloy at elevated temperatures provided evidence of work hardening; however, the degree of work hardening decreased with an increase in temperature. And it can also be found that when the temperature is higher, the fluctuation of the cutting force curve is greater. PMID:22549875

  12. Tribological Properties of AlCrCuFeNi2 High-Entropy Alloy in Different Conditions

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Ma, Shengguo; Gao, Michael C.; Zhang, Chuan; Zhang, Teng; Yang, Huijun; Wang, Zhihua; Qiao, Junwei

    2016-02-01

    In order to understand the environmental effect on the mechanical behavior of high-entropy alloys, the tribological properties of AlCrCuFeNi2 are studied systematically in dry, simulated rainwater, and deionized water conditions against the Si3N4 ceramic ball at a series of different normal loads. The present study shows that both the friction and wear rate in simulated rainwater are the lowest. The simulated rainwater plays a significant role in the tribological behavior with the effect of forming passive film, lubricating, cooling, cleaning, and corrosion. The wear mechanism in simulated rainwater is mainly adhesive wear accompanied by abrasive wear as well as corrosive wear. In contrast, those in dry condition and deionized water are abrasive wear, adhesive wear, and surface plastic deformation. Oxidation contributes to the wear behavior in dry condition but is prevented in liquid condition. In addition, the phase diagram of Al x CrCuFeNi2 is predicted using CALPHAD modeling, which is in good agreement with the literature report and the present study.

  13. Significant Improvement of Mechanical Properties in NiAl-Cr(Mo)/Hf Alloy by Suction Casting and Subsequent Hot Isostatic Pressing

    NASA Astrophysics Data System (ADS)

    Guo, J. T.; Huai, K. W.; Li, H. T.

    2007-01-01

    The NiAl-28Cr-5.5Mo-0.5Hf eutectic alloy was prepared by the suction casting (SC) technique and subsequent hot isostatic pressing (HIP) treatment, and tested for compressive strength and fracture behavior in the temperature range of 300 to 1373 K. The microstructure of suction-cast alloy is characterized by fine interlamellar spacing, large area fraction of eutectic cell, and fine Heusler (Ni2AlHf) phase distributed semicontinuously at the cell boundaries. After HIP treatment, Ni2AlHf phase at the cell boundaries is transformed into Hf solid solution phase and distributed homogeneously within the NiAl matrix. Compared with the conventionally cast alloy, the room-temperature compressive strain and elevated temperature strength of suction-cast alloy are enhanced markedly after HIP treatment. The reason is that the HIP treatment causes Hf solid solution phase to distribute homogeneously and then strengthens the NiAl matrix.

  14. Compositional Pathways and Capillary Effects during Early-stage Isothermal Precipitation in a Nondilute Ni-Al-Cr Alloy

    NASA Technical Reports Server (NTRS)

    Sudbrack, Chantal K.; Noebe, Ronald D.; Seidman, David N.

    2006-01-01

    For a Ni-5.2 Al-14.2 Cr at.% alloy with moderate solute supersaturations, the compositional pathways, as measured with atom-probe tomography, during early to later stage y'(LI2)-precipitation (R = 0.45-10 nm), aged at 873 K, are discussed in light of a multi-component coarsening model. Employing nondilute thermodynamics, detailed model analyses during quasistationary coarsening of the experimental data establish that the y/y' interfacial free-energy is 22- 23+/-7 mJ/sq m. Additionally, solute diffusivities are significantly slower than model estimates. Strong quantitative evidence indicates that an observed y'-supersaturation of Al results from the Gibbs-Thomson effect, providing the first experimental verification of this phenomenon. The Gibbs-Thomson relationship, for a ternary system, as well as differences in measured phase equilibria with CALPHAD assessments, are considered in great detail.

  15. Phase Transformation and Aging Behavior of Al0.5CoCrFeNiSi0.2 High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Wu, G. F.; Dai, P. Q.

    2015-05-01

    An Al0.5CoCrFeNiSi0.2 high-entropy alloy was prepared by vacuum arc melting. The alloy was aged from 700 to 1100 °C. The effects of aging on the phase transformation and mechanical performances were explored. The as-cast alloy showed a dendritic (DR) microstructure. The DR region was an Fe,Cr-rich FCC phase, while the interdendritic (ID) region was a spinodal structure composed of Fe,Cr-rich BCC (A2) and Ni,Al-rich BCC (B2) phases. At aging temperatures between 700 and 900 °C, the Fe,Cr-rich BCC (A2) phase in the ID region transformed into σ and Fe,Cr-rich FCC phases. Meanwhile, some Ni,Al-rich FCC phase particles precipitated from the DR region. During aging at 1100 °C, the DR microstructure disappeared, and a microstructure composed of Fe,Cr-rich FCC and Ni,Al-rich BCC (B2) phases both possessing a lamellar shape was developed. The alloy exhibited evident hardening and lower tensile strain when the aging temperature was lower than 1000 °C, which was mainly attributed to the generation of the σ phase in the ID region. However, a contrasting behavior was observed when the aging temperature was higher than 1000 °C, which was attributed to the redissolution of the σ phase and the microstructure coarsening.

  16. Rub tolerance evaluation of two sintered NiCrAl gas path seal materials. [wear tests of gas turbine engine seals

    NASA Technical Reports Server (NTRS)

    Bill, R. C.

    1978-01-01

    Two strength level variations of sintered NiCrAl (about 40 percent dense), candidate high pressure turbine seal materials, were subject to rub tolerance testing against AM 355 steel blade tips. The high strength material (17 N/sq mm tensile strength) showed frictional and radial loads that were 20 to 50 percent higher than those measured for the low strength material (15.5 N/ sq mm tensile strength). Measured wear to the AM 355 blade tips was not significantly different for the two sintered NiCrAl seal materials. Wear of the sintered NiCrAl was characterized by material removal to a depth greater than the depth to which blade tips were driven into the seal, indicating self-erosion effects.

  17. Impact of CrSiTi and NiSi on the Thermodynamics, Microstructure, and Properties of AlCoCuFe-Based High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Rong; Wang, Zhao-Qin; Lin, Tie-Song; He, Peng; Sekulic, Dusan P.

    2016-05-01

    Aiming to solve the problem of spontaneous combustion on titanium via electrospark deposition (ESD), two AlCoCuFe-based high-entropy alloys (HEAs), AlCoCuFe- x ( x = CrSiTi, NiSi), were produced by vacuum arc melting as electrodes in ESD process. The thermodynamic analysis of AlCoCuFe-based HEAs were carried out using the concept of mixing enthalpy matrix and a powerful thermodynamic calculation toolbox (HEA-Thermo-Calcu). The microstructure and mechanical properties of the two alloys were investigated. The AlCoCuFeCrSiTi alloy contains a body-centered cubic (BCC) phase and a face-centered cubic (FCC) phase. The AlCoCuFeNiSi alloy is composed of two BCC phases and an FCC phase. Addition of CrSiTi and NiSi to AlCoCuFe-based alloys makes the enthalpy of mixing to be sizably more negative than for the other AlCoCuFe-based HEAs. Notwithstanding the fact that the thermodynamic parameters do not agree with Yang's proposition, the two alloys form simple solid solutions. The electronegativity difference (Δ χ) favors a formation of the solid solution when Δχ ≤ 14.2. The hardness of AlCoCuFe- x ( x = CrSiTi, NiSi) alloys reaches 935 HV and 688 HV, respectively. The yield strength, fracture strength, and ultimate strain of AlCoCuFeNiSi are larger, i.e., 29, 30, and 45%, respectively, than those of the AlCoCuFeCrSiTi alloy.

  18. Impact of CrSiTi and NiSi on the Thermodynamics, Microstructure, and Properties of AlCoCuFe-Based High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Rong; Wang, Zhao-Qin; Lin, Tie-Song; He, Peng; Sekulic, Dusan P.

    2016-03-01

    Aiming to solve the problem of spontaneous combustion on titanium via electrospark deposition (ESD), two AlCoCuFe-based high-entropy alloys (HEAs), AlCoCuFe-x (x = CrSiTi, NiSi), were produced by vacuum arc melting as electrodes in ESD process. The thermodynamic analysis of AlCoCuFe-based HEAs were carried out using the concept of mixing enthalpy matrix and a powerful thermodynamic calculation toolbox (HEA-Thermo-Calcu). The microstructure and mechanical properties of the two alloys were investigated. The AlCoCuFeCrSiTi alloy contains a body-centered cubic (BCC) phase and a face-centered cubic (FCC) phase. The AlCoCuFeNiSi alloy is composed of two BCC phases and an FCC phase. Addition of CrSiTi and NiSi to AlCoCuFe-based alloys makes the enthalpy of mixing to be sizably more negative than for the other AlCoCuFe-based HEAs. Notwithstanding the fact that the thermodynamic parameters do not agree with Yang's proposition, the two alloys form simple solid solutions. The electronegativity difference (Δχ) favors a formation of the solid solution when Δχ ≤ 14.2. The hardness of AlCoCuFe-x (x = CrSiTi, NiSi) alloys reaches 935 HV and 688 HV, respectively. The yield strength, fracture strength, and ultimate strain of AlCoCuFeNiSi are larger, i.e., 29, 30, and 45%, respectively, than those of the AlCoCuFeCrSiTi alloy.

  19. Galvanomagnetic properties of Fe2YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-01

    The Hall effect and the magnetoresistance of Fe2YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3 d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit ( H > 10 kOe), the value and the sign of the normal ( R 0) and anomalous ( R s ) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R s in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio ( R s ∝ ρ 0 3.1 ), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  20. Galvanomagnetic properties of Fe{sub 2}YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    SciTech Connect

    Kourov, N. I. Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-15

    The Hall effect and the magnetoresistance of Fe{sub 2}YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit (H > 10 kOe), the value and the sign of the normal (R{sub 0}) and anomalous (R{sub s}) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R{sub s} in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio (R{sub s} ∝ ρ{sub 0}{sup 3.1}), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  1. Interaction of a near-{alpha} type titanium alloy with NiCrAlY protective coating at high temperatures

    SciTech Connect

    Liu, H.; Hao, S.; Wang, X.; Feng, Z.

    1998-10-13

    MCrAlY coatings possess the properties of not only excellent oxidation and hot corrosion resistance but also sufficient toughness. This is why they have been commercially used on superalloys for several decades. Nevertheless, investigations revealed that there might be violent interactions between this kind of coating and titanium based alloys at high temperatures. This chemical incompatibility may promote the growth of brittle phases along the substrate/coating interface and thus deteriorates the mechanical properties. An effective barrier layer was desired to be sandwiched between the MCrAlY coating and Ti substrate to weaken the interdiffusion and chemical reactions. Ti60 is a near {alpha} type alloy intended to be used at 600 C. The interaction between this alloy and a NiCrAlY coating has never been investigated. Actually, in addition to the service at high temperature, another high temperature process, i.e., the post heat treatment in vacuum, is generally needed for the MCrAlY coating to eliminate possible defects within the received PVD coatings. Hence, the investigation on the interfacial stability of a Ti60/MCrAlY system at high temperatures is of importance in both theoretical and practical meanings. This paper is aimed at observing the interfacial reactions of this system at various temperatures in excess of 600 C. The obtained data may be useful in further work on optimizing the post treatment parameters and developing new coating systems with barrier interlayer.

  2. Isothermal and bithermal thermomechanical fatigue behavior of a NiCoCrAlY-coated single crystal superalloy

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    Specimens of single crystal PWA 1480 with group of zone axes (100) orientation, bare, or with NiCoCrAlY coating PWA 276, were tested in low cycle fatigue (LCF) at 650, 870, and 1050 C, and in simplified bithermal thermomechanical fatigue (TMF) tests between these temperatures. These tests were examined as a bridge between isothermal LCF and general TMF. In the bithermal test, an inelastic strain is applied at one temperature, T sub max, and reversed at T sub min. The out-of-phase (OP) test type imposing tension at T sub min and compression at T sub max received most study, since it was more damaging than the in-phase type. Specifically investigated were the effects of: inelastic strain range, the coating, delta T, T sub max, T sub min, and the environment.

  3. Isothermal and 'bithermal' thermomechanical fatigue behavior of a NiCoCrAlY-coated single crystal superalloy

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    Specimens of single crystal PWA 1480 with group of zone axes (100) orientation, bare, or with NiCoCrAlY coating PWA 276, were tested in low cycle fatigue (LCF) at 650, 870, and 1050 C, and in simplified bithermal thermomechanical fatigue (TMF) tests between these temperatures. These tests were examined as a bridge between isothermal LCF and general TMF. In the bithermal test, and inelastic strain is applied at one temperature, T sub max, and reversed at T sub min. The out-of-phase (OP) test type imposing tension at T sub min and compression at T sub max received most study, since it was more damaging than the in-phase type. Specifically investigated were the effects of: inelastic strain range, the coating, delta T, T sub max, T sub min, and the environment.

  4. Nanoindentation Creep Behavior of an Al0.3CoCrFeNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Lijun; Yu, Pengfei; Cheng, Hu; Zhang, Huan; Diao, Haoyan; Shi, Yunzhu; Chen, Bilin; Chen, Peiyong; Feng, Rui; Bai, Jie; Jing, Qin; Ma, Mingzhen; Liaw, P. K.; Li, Gong; Liu, Riping

    2016-03-01

    Nanoindentation creep behavior was studied on a coarse-grained Al0.3CoCrFeNi high-entropy alloy with a single face-centered cubic structure. The effects of the indentation size and loading rate on creep behavior were investigated. The experimental results show that the hardness, creep depth, creep strain rate, and stress exponent are all dependent on the holding load and loading rate. The creep behavior shows a remarkable indentation size effect at different maximum indentation loads. The dominant creep mechanism is dislocation creep at high indentation loads and self-diffusion at low indentation loads. An obvious loading rate sensitivity of creep behavior is found under different loading rates for the alloy. A high loading rate can lead to a high strain gradient, and numerous dislocations emerge and entangle together. Then during the holding time, a large creep deformation characteristic with a high stress exponent will happen.

  5. Structure and magnetic properties of a Ni3(Al, Fe, Cr) single crystal subjected to high-temperature deformation

    NASA Astrophysics Data System (ADS)

    Kazantseva, N. V.; Rigmant, M. B.; Stepanova, N. N.; Davydov, D. I.; Shishkin, D. A.; Terent'ev, P. B.; Vinogradova, N. I.

    2016-05-01

    The structure and magnetic properties of the Ni3(Al, Fe, Cr) single crystal subjected to high-temperature tensile deformation to failure at 850-900°C have been studied. No recrystallized grains and metastable phases were found. The rupture zone of the alloy subjected to deformation (at 900°C) to the highest degree demonstrates the fragmentation accompanied by rotation of atomic layers and changes of the chemical composition in the nickel and aluminum sublattices. Magnetic studies of the alloy have shown the existence of two Curie temperatures for samples cut from the rupture zone. Samples cut away from the rupture zone exhibit no additional magnetic transitions; twines and planar stacking faults in the alloy structure. The alloy deformed to the lower degree of deformation (at 850°C) also demonstrates twins; no ferromagnetic state was found to form.

  6. TEMPORAL EVOLUTION OF SUB-NANOMETER COMPOSITIONAL PROFILES ACROSS THE GAMMA/GAMMA' INTERFACE IN A MODEL Ni-Al-Cr SUPERALLOY

    NASA Technical Reports Server (NTRS)

    Sudbrack, Chantal K.; Noebe, Ronald D.; Seidman, David N.

    2005-01-01

    Early-stage phase separation in a Ni-5.2 Al-14.2 Cr at.% superalloy, isothermally decomposing at 873 K, is investigated with atom-probe tomography. Sub-nanometer scale compositional profiles across the gamma/gamma'(L12) interfaces demonstrate that both the gamma-matrix and the gamma'-precipitate compositions evolve with time. Observed chemical gradients of Al depletion and Cr enrichment adjacent to the gamma'-precipitates are transient, consistent with well-established model predictions for diffusion-limited growth, and mark the first detailed observation of this phenomenon. Furthermore, it is shown that Cr atoms are kinetically trapped in the growing precipitates.

  7. Microscopic Morphology and Microstructure of Ti-N and Ti-Ni Phase Between the Dilution Zone and the Clad Zone in Laser Remelting NiCrBSi/TiN Layer on Ti-6Al-4V Alloy Surface

    NASA Astrophysics Data System (ADS)

    Liu, Rongxiang; Guo, Lixin; Lei, Tingquan

    The microscopic morphology and microstructure of Ti-N and Ti-Ni phase between the dilution zone and the clad zone in laser remelting NiCrBSi/TiN layer on a Ti-6Al-4V alloy were characterized using TEM and SEM. The experimental results showed that during laser irradiation heating, TiN particles were partially dissolved into the melted Ni-base alloy, and the dissolved Ti and N atoms were precipitated in the form of TiN, TiN0.3. Ti exhibits height activity, it combines with Ni forming Ti2Ni, TiNi matrix intermetallic during laser remelting, faults exist in the Ti2Ni and TiNi phase, and crystal lattice of TiNi phase is superlattice. Lastly, the cause of the formation of the Ti-N and Ti-Ni phase is discussed.

  8. Influence of transition metals (Cr, Mn, Fe, Co and Ni) on the methane combustion over Pd/Ce-Zr/Al 2O 3 catalyst

    NASA Astrophysics Data System (ADS)

    Yue, Baohua; Zhou, Renxian; Wang, Yuejuan; Zheng, Xiaoming

    2006-06-01

    The effects of transition metals (Cr, Mn, Fe, Co and Ni) on the catalytic properties of Pd/Ce-Zr/Al 2O 3 catalyst for methane combustion have been investigated. The supported Pd catalysts are characterized by BET, XRD, TEM, TPR, TPO and TPSR measurements. Activity tests in methane combustion show that Pd/Ce-Zr-Ni/Al 2O 3 has the highest catalytic activity and thermal stability among all catalysts. The results of TEM show that the addition of Ni to Pd/Ce-Zr/Al 2O 3 increases the dispersion of Pd component and inhibits the site growth. The results of TPO and TPSR show that the addition of Ni inhibits the decomposition of PdO particles and improves the reduction-reoxidation properties of the active PdO species, which increases the catalytic activity and thermal stability of the Pd/Ce-Zr/Al 2O 3 catalyst.

  9. Microstructural evolution and mechanical properties of an Fe-18Ni-16Cr-4Al base alloy during aging at 950°C

    NASA Astrophysics Data System (ADS)

    Wang, Man; Sun, Yong-duo; Feng, Jing-kai; Zhang, Rui-qian; Tang, Rui; Zhou, Zhang-jian

    2016-03-01

    The development of Gen-IV nuclear systems and ultra-supercritical power plants proposes greater demands on structural materials used for key components. An Fe-18Ni-16Cr-4Al (316-base) alumina-forming austenitic steel was developed in our laboratory. Its microstructural evolution and mechanical properties during aging at 950°C were investigated subsequently. Micro-structural changes were characterized by scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. Needle-shaped NiAl particles begin to precipitate in austenite after ageing for 10 h, whereas round NiAl particles in ferrite are coarsened during aging. Precipitates of NiAl with different shapes in different matrices result from differences in lattice misfits. The tensile plasticity increases by 32.4% after aging because of the improvement in the percentage of coincidence site lattice grain boundaries, whereas the tensile strength remains relatively high at approximately 790 MPa.

  10. Atomistic clustering-ordering and high-strain deformation of an Al0.1CrCoFeNi high-entropy alloy

    DOE PAGESBeta

    Sharma, Aayush; Singh, Prashant; Johnson, Duane D.; Liaw, Peter K.; Balasubramanian, Ganesh

    2016-08-08

    Here, computational investigations of structural, chemical, and deformation behavior in high-entropy alloys (HEAs), which possess notable mechanical strength, have been limited due to the absence of applicable force fields. To extend investigations, we propose a set of intermolecular potential parameters for a quinary Al-Cr-Co-Fe-Ni alloy, using the available ternary Embedded Atom Method and Lennard-Jones potential in classical molecular-dynamics simulations. The simulation results are validated by a comparison to first-principles Korringa-Kohn-Rostoker (KKR) - Coherent Potential Approximation (CPA) [KKR-CPA] calculations for the HEA structural properties (lattice constants and bulk moduli), relative stability, pair probabilities, and high-temperature short-range ordering. The simulation (MD)-derived propertiesmore » are in quantitative agreement with KKR-CPA calculations (first-principles) and experiments. We study AlxCrCoFeNi for Al ranging from 0 ≤ x ≤2 mole fractions, and find that the HEA shows large chemical clustering over a wide temperature range for x < 0.5. At various temperatures high-strain compression promotes atomistic rearrangements in Al0.1CrCoFeNi, resulting in a clustering-to-ordering transition that is absent for tensile loading. Large fluctuations under stress, and at higher temperatures, are attributed to the thermo-plastic instability in Al0.1CrCoFeNi.« less

  11. Influence of superalloy substrate roughness on adhesion and oxidation behavior of magnetron-sputtered NiCoCrAlY coatings

    NASA Astrophysics Data System (ADS)

    Li, Zhiming; Qian, Shiqiang; Wang, Wei

    2011-10-01

    The present study has been conducted in order to determine the influence of superalloy substrate roughness on adhesion and oxidation behavior of magnetron-sputtered NiCoCrAlY coatings. Six types of coating samples with different substrate roughness were tested. The surface roughness and real surface area of both the substrates and coatings were studied by atomic force microscopy (AFM) techniques. The scratch tests performed at progressive loads were employed to evaluate the adhesion of the coatings. Cyclic oxidation tests were performed at 1100 °C in air for 50 cycles, each cycle consisting of 1 h heating in the tube furnace followed by 15 min cooling in the open air. The AFM measurements exhibit that the surface roughness of the sputtered NiCoCrAlY coating increases with the increasing of the superalloy substrate roughness. The NiCoCrAlY coatings present slightly lower roughness than the corresponding superalloy substrate. The scratch adhesion tests indicate that the coatings on substrates with a smoother surface possess better adhesion than on those with a rougher surface. Both the real surface area and oxidation weight gain of the coatings decrease with the decreasing of the superalloy substrate roughness. The NiCoCrAlY coating sputtered on the superalloy substrate with lower roughness provides relatively higher antioxidant protection than that provided by the coating with rougher substrate.

  12. Atomistic clustering-ordering and high-strain deformation of an Al0.1CrCoFeNi high-entropy alloy

    PubMed Central

    Sharma, Aayush; Singh, Prashant; Johnson, Duane D.; Liaw, Peter K.; Balasubramanian, Ganesh

    2016-01-01

    Computational investigations of structural, chemical, and deformation behavior in high-entropy alloys (HEAs), which possess notable mechanical strength, have been limited due to the absence of applicable force fields. To extend investigations, we propose a set of intermolecular potential parameters for a quinary Al-Cr-Co-Fe-Ni alloy, using the available ternary Embedded Atom Method and Lennard-Jones potential in classical molecular-dynamics simulations. The simulation results are validated by a comparison to first-principles Korringa-Kohn-Rostoker (KKR) - Coherent Potential Approximation (CPA) [KKR-CPA] calculations for the HEA structural properties (lattice constants and bulk moduli), relative stability, pair probabilities, and high-temperature short-range ordering. The simulation (MD)-derived properties are in quantitative agreement with KKR-CPA calculations (first-principles) and experiments. We study AlxCrCoFeNi for Al ranging from 0 ≤ x ≤2 mole fractions, and find that the HEA shows large chemical clustering over a wide temperature range for x < 0.5. At various temperatures high-strain compression promotes atomistic rearrangements in Al0.1CrCoFeNi, resulting in a clustering-to-ordering transition that is absent for tensile loading. Large fluctuations under stress, and at higher temperatures, are attributed to the thermo-plastic instability in Al0.1CrCoFeNi. PMID:27498807

  13. Atomistic clustering-ordering and high-strain deformation of an Al0.1CrCoFeNi high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Sharma, Aayush; Singh, Prashant; Johnson, Duane D.; Liaw, Peter K.; Balasubramanian, Ganesh

    2016-08-01

    Computational investigations of structural, chemical, and deformation behavior in high-entropy alloys (HEAs), which possess notable mechanical strength, have been limited due to the absence of applicable force fields. To extend investigations, we propose a set of intermolecular potential parameters for a quinary Al-Cr-Co-Fe-Ni alloy, using the available ternary Embedded Atom Method and Lennard-Jones potential in classical molecular-dynamics simulations. The simulation results are validated by a comparison to first-principles Korringa-Kohn-Rostoker (KKR) - Coherent Potential Approximation (CPA) [KKR-CPA] calculations for the HEA structural properties (lattice constants and bulk moduli), relative stability, pair probabilities, and high-temperature short-range ordering. The simulation (MD)-derived properties are in quantitative agreement with KKR-CPA calculations (first-principles) and experiments. We study AlxCrCoFeNi for Al ranging from 0 ≤ x ≤2 mole fractions, and find that the HEA shows large chemical clustering over a wide temperature range for x < 0.5. At various temperatures high-strain compression promotes atomistic rearrangements in Al0.1CrCoFeNi, resulting in a clustering-to-ordering transition that is absent for tensile loading. Large fluctuations under stress, and at higher temperatures, are attributed to the thermo-plastic instability in Al0.1CrCoFeNi.

  14. Effect of Water Vapor on the 1100oC Oxidation Behavior of Plasma-Sprayed TBCs with HVOF NiCoCrAlX Bond Coatings

    SciTech Connect

    Haynes, James A; Unocic, Kinga A; Pint, Bruce A

    2013-01-01

    With the goal of investigating the reported detrimental effect of water vapor on thermal barrier coating (TBC) performance, furnace cycle experiments were conducted in dry O2 and air with 10 and 50% water vapor at 1100 C. The TBC systems evaluated were air plasma-sprayed (APS), yttria-stabilized zirconia (YSZ) top coatings with high velocity oxy fuel (HVOF)-deposited NiCoCrAlY or NiCoCrAlYHfSi bond coating. Average TBC lifetime was reduced by ~30% in air with 10% water vapor compared to cycling in dry O2, using 1h cycle durations. Superalloy substrates with Y and La additions also were investigated but showed no statistical change in the average TBC lifetime compared to the base CMSX4 superalloy. In all cases, the bond coating with Hf and Si additions increased YSZ lifetime by 20% or more. Experiments that increased water vapor to 50% showed no further decrease in TBC lifetime. Increasing the cycle frequency to 100h resulted in a large increase in TBC lifetime, especially for the NiCoCrAlYHfSi bond coatings. Co-doping the NiCoCrAl bond coat with Y and Hf was beneficial to TBC lifetime, but did not mitigate the detrimental impact of water vapor.

  15. Atomistic clustering-ordering and high-strain deformation of an Al0.1CrCoFeNi high-entropy alloy.

    PubMed

    Sharma, Aayush; Singh, Prashant; Johnson, Duane D; Liaw, Peter K; Balasubramanian, Ganesh

    2016-01-01

    Computational investigations of structural, chemical, and deformation behavior in high-entropy alloys (HEAs), which possess notable mechanical strength, have been limited due to the absence of applicable force fields. To extend investigations, we propose a set of intermolecular potential parameters for a quinary Al-Cr-Co-Fe-Ni alloy, using the available ternary Embedded Atom Method and Lennard-Jones potential in classical molecular-dynamics simulations. The simulation results are validated by a comparison to first-principles Korringa-Kohn-Rostoker (KKR) - Coherent Potential Approximation (CPA) [KKR-CPA] calculations for the HEA structural properties (lattice constants and bulk moduli), relative stability, pair probabilities, and high-temperature short-range ordering. The simulation (MD)-derived properties are in quantitative agreement with KKR-CPA calculations (first-principles) and experiments. We study AlxCrCoFeNi for Al ranging from 0 ≤ x ≤2 mole fractions, and find that the HEA shows large chemical clustering over a wide temperature range for x < 0.5. At various temperatures high-strain compression promotes atomistic rearrangements in Al0.1CrCoFeNi, resulting in a clustering-to-ordering transition that is absent for tensile loading. Large fluctuations under stress, and at higher temperatures, are attributed to the thermo-plastic instability in Al0.1CrCoFeNi. PMID:27498807

  16. Microstructure, Mechanical Properties, and Two-Body Abrasive Wear Behavior of Cold-Sprayed 20 vol.% Cubic BN-NiCrAl Nanocomposite Coating

    NASA Astrophysics Data System (ADS)

    Luo, Xiao-Tao; Yang, Er-Juan; Shang, Fu-Lin; Yang, Guan-Jun; Li, Chen-Xin; Li, Chang-Jiu

    2014-10-01

    20 vol.% cubic boron nitride (cBN) dispersoid reinforced NiCrAl matrix nanocomposite coating was prepared by cold spray using mechanically alloyed nanostructured composite powders. The as-sprayed nanocomposite coating was annealed at a temperature of 750 °C to enhance the inter-particle bonding. Microstructure of spray powders and coatings was characterized. Vickers microhardness of the coatings was measured. Two-body abrasive wear behavior of the coatings was examined on a pin-on-disk test. It was found that, in mechanically alloyed composite powders, nano-sized and submicro-sized cBN particles are uniformly distributed in nanocrystalline NiCrAl matrix. Dense coating was deposited by cold spray at a gas temperature of 650 °C with the same phases and grain size as those of the starting powder. Vickers hardness test yielded a hardness of 1063 HV for the as-sprayed 20 vol.% cBN-NiCrAl coating. After annealed at 750 °C for 5 h, unbonded inter-particle boundaries were partially healed and evident grain growth of nanocrystalline NiCrAl was avoided. Wear resistance of the as-sprayed 20 vol.% cBN-NiCrAl nanocomposite coating was comparable to the HVOF-sprayed WC-12Co coating. Annealing of the nanocomposite coating resulted in the improvement of wear resistance by a factor of ~33% owing to the enhanced inter-particle bonding. Main material removal mechanisms during the abrasive wear are also discussed.

  17. Laser cladding of Ni-Cr-Al-Hf on inconel 718 for improved high-temperature oxidation resistance

    SciTech Connect

    Singh, J.; Nagarathnam, K.; Mazumder, J.

    1987-08-03

    In-situ Ni-Cr-Al-Hf alloy was developed by laser surface cladding with a mixed-powder feed for improved high-temperature oxidation resistance. Oxidation-resistant materials for operation at elevated temperatures must satisfy two requirements: diffusion through the oxide scale must occur at the lowest possible rate, and the oxide scale must resist spallation. Formation of an Al/sub 2/O/sub 3/ protective scale fulfills the former requirement but its adherence is poor. A reactive metal such as Hf is added to improve adhesion. A 10-kW CO/sub 2/ laser was used for laser cladding. Optical, SEM and STEM microanalysis techniques were employed to characterize the different phases produced during the cladding process. Microstructural studies showed a high degree of grain refinement, increased solid solubility of Hf in the matrix and the formation of Hf-rich precipitates. A thermogravimetric analysis was carried out to determine the oxidation properties of these clad alloys with an extended solid solution of Hf. Considerable improvement over the base metal was observed. This paper discusses microstructural development in this laser-clad alloy and its effect on oxidation.

  18. APS TBC performance on directionally-solidified superalloy substrates with HVOF NiCoCrAlYHfSi bond coatings

    DOE PAGESBeta

    Lance, Michael J.; Unocic, Kinga A.; Haynes, James A.; Pint, Bruce A.

    2015-09-04

    Directionally-solidified (DS) superalloy components with advanced thermal barrier coatings (TBC) to lower the metal operating temperature have the potential to replace more expensive single crystal superalloys for large land-based turbines. In order to assess relative TBC performance, furnace cyclic testing was used with superalloys 1483, X4 and Hf-rich DS 247 substrates and high velocity oxygen fuel (HVOF)-NiCoCrAlYHfSi bond coatings at 1100 °C with 1-h cycles in air with 10% H2O. With these coating and test conditions, there was no statistically-significant effect of substrate alloy on the average lifetime of the air plasma sprayed (APS) yttria-stabilized zirconia (YSZ) top coatings onmore » small coupons. Using photo-stimulated luminescence piezospectroscopy maps at regular cycling intervals, the residual compressive stress in the α-Al2O3 scale underneath the YSZ top coating and on a bare bond coating was similar for all three substrates and delaminations occurred at roughly the same rate and frequency. As a result, x-ray fluorescence (XRF) measurements collected from the bare bond coating surface revealed higher Ti interdiffusion occurring with the 1483 substrate, which contained the highest Ti content.« less

  19. APS TBC performance on directionally-solidified superalloy substrates with HVOF NiCoCrAlYHfSi bond coatings

    SciTech Connect

    Lance, Michael J.; Unocic, Kinga A.; Haynes, James A.; Pint, Bruce A.

    2015-09-04

    Directionally-solidified (DS) superalloy components with advanced thermal barrier coatings (TBC) to lower the metal operating temperature have the potential to replace more expensive single crystal superalloys for large land-based turbines. In order to assess relative TBC performance, furnace cyclic testing was used with superalloys 1483, X4 and Hf-rich DS 247 substrates and high velocity oxygen fuel (HVOF)-NiCoCrAlYHfSi bond coatings at 1100 °C with 1-h cycles in air with 10% H2O. With these coating and test conditions, there was no statistically-significant effect of substrate alloy on the average lifetime of the air plasma sprayed (APS) yttria-stabilized zirconia (YSZ) top coatings on small coupons. Using photo-stimulated luminescence piezospectroscopy maps at regular cycling intervals, the residual compressive stress in the α-Al2O3 scale underneath the YSZ top coating and on a bare bond coating was similar for all three substrates and delaminations occurred at roughly the same rate and frequency. As a result, x-ray fluorescence (XRF) measurements collected from the bare bond coating surface revealed higher Ti interdiffusion occurring with the 1483 substrate, which contained the highest Ti content.

  20. Interdiffusion in the Ni/TD-NiCr and Cr/TD-NiCr systems

    NASA Technical Reports Server (NTRS)

    Pawar, A. V.; Tenney, D. R.

    1974-01-01

    The diffusion of Ni and Cr into TD-NiCr has been studied over the 900 to 1100 C temperature range. The diffusion couples were prepared by electroplating Cr and Ni on polished TD-NiCr wafers. Concentration profiles produced as a result of isothermal diffusion at 905, 1000, and 1100 C were determined by electron microprobe analysis. The Boltzmann-Matano analysis was used to determine concentration-dependent diffusion coefficients which were found to compare favorably with previously reported values. These data suggest that 2 vol % ThO2 distribution has no appreciable effect on the rates of diffusion in TD-NiCr with a large grain size. This supports the view that an inert dispersoid in an alloy matrix will not in itself lead to enhanced diffusion unless a short-circuit diffusion structure is stabilized.

  1. The Influence of Tungsten on the Chemical Composition of a Temporally Evolving Nanostructure of a Model Ni-Al-Cr Superalloy

    NASA Technical Reports Server (NTRS)

    Sudbrack, Chantal K.; Isheim, Dieter; Noebe, Ronald D.; Jacobson, Nathan S.; Seidman, David N.

    2004-01-01

    The influence of W on the temporal evolution of gamma' precipitation toward equilibrium in a model Ni-Al-Cr alloy is investigated by three-dimensional atom-probe (3DAP) microscopy and transmission electron microscopy (TEM). We report on the alloys Ni-10 Al-8.5 Cr (at.%) and Ni-10 Al-8.5 Cr-2 W (at.%), which were aged isothermally in the gamma + gamma' two-phase field at 1073 K, for times ranging from 0.25 to 264 h. Spheroidal-shaped gamma' precipitates, 5-15 nm diameter, form during quenching from above the solvus temperature in both alloys at a high number density (approx. 10(exp 23/cu m). As gamma' precipitates grow with aging at 1073 K, a transition from spheriodal- to cuboidal-shaped precipitates is observed in both alloys. The elemental partitioning and spatially resolved concentration profiles across the gamma' precipitates are obtained as a function of aging time from three-dimensional atom-by-atom reconstructions. Proximity histogram concentration profiles of the quaternary alloy demonstrate that W concentration gradients exist in gamma' precipitates in the as-quenched and 0.25-h aging states, which disappear after 1 h of aging. The diffusion coefficient of W in gamma' is estimated to be 6.2 x 10(exp -20) sq m/s at 1073 K. The W addition decreases the coarsening rate constant, and leads to stronger partitioning of Al to gamma' and Cr to gamma.

  2. Microstructure and mechanical properties of Fe-Ni-Cr-Al steel wires produced by in-rotating-water spinning method

    NASA Astrophysics Data System (ADS)

    Inoue, A.; Tomioka, H.; Masumoto, T.

    1985-02-01

    Nonequilibrium austenite, γ, or duplex austenite + lath martensite,γ + α' L, phase wires with high strengths and large elongation have been produced in Fe-Ni-Cr-Al-C alloy system by the in-rotating-water spinning method in which a melt stream is ejected into a rotating water layer. These wires have a circular cross section and a white luster, and the wire diameter is in the range of 80 to 180 µm. The γ phase has a grain size as small as about 1 to 4 µm. The yield strength, Σy, tensile fracture strength, ay, and elongation, ɛp, are about 340 to 655 MPa, 440 to 975 MPa, and 12 to 22 pct for the γ single phase wires and about 465 to 865 MPa, 640 to 1350 MPa, and 2 to 18 pct for the α'L+ γ duplex phase wires. A cold drawing causes significant increases in Σy and Σf, and the attained values are about 3200 MPa and 4030 MPa for Fe-8Ni-12.5Cr-2.5Al-3C wire drawn to about 95 pct reduction in area owing to the formation of a strain-induced α'L phase and a remarkable work-hardening ability of γ and α'L phases. On the subsequent low-temperature annealing around 673 K, the Σy and Σf increase further to 4000 MPa and 4240 MPa, respectively, probably because of the enhancement of the interaction between dislocations and interstitial carbon atoms. Around the temperature (≃800 K) where the γ phase decomposes into a stable mixed structure of α + ordered bec compound + M7C3 on annealing, the ɛp decreases drastically and the fracture surface morphology changes from a dimple pattern to a cleavage pattern. It has been therefore inferred that the high strengths and good ductility of the melt-quenched y and γ + α'L wires are due to the suppression of the phase transformation of y to a mixed structure of γ + ordered bec compound + M7C3 carbide by the melt-quenching technique.

  3. Microstructure And Oxidation Properties Of Laser Clad Ni70AL20Cr7Hf3 Alloys With Extended Solid Solution Of Hf

    NASA Astrophysics Data System (ADS)

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

    1989-01-01

    Alloys coatings for superalloys for improved higher temperature (1200°C) service life under aggressive atmospheres are of great interest at present. There is a general consensus that addition of rare earths such as hafnium (Hf) to these alloys has a pronounced effect on the oxidation resistance properties at high temperatures. In situ laser cladding technique was used to produce Ni-Al-Cr-Hf alloys with extended solid solution of Hf in a near stoichiometric Ni3Al matrix. A 10 kW CW CO2 laser was used in conjunction with a screw-feed powder dispenser to perform the in situ cladding process.

  4. Creep-fatigue behavior of NiCoCrAlY coated PWA 1480 superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Miner, R. V.; Gayda, J.; Hebsur, M. G.

    1985-01-01

    Single crystal specimens of a Ni base superalloy, PWA 1480, with a low pressure plasma sprayed NiCoCrAlY coating were tested in various 0.1 Hz fatigue and creep fatigue cycles both at 1015 and 1050 C. Creep fatigue tests of the cp, pc, and cc types were conducted with various constant total strain ranges employing creep dwells at various constant stresses. Considerable cyclic softening occurred as was evidenced particularly by rapidly increasing creep rates in the creep fatigue tests. The cycle time in the creep fatigue tests typically decreased by more than 80 percent at 0.5 N sub f. Though cyclic life did correlate with delta epsilon sub in a better correlation existed with sub f for both the fatigue and creep fatigue tests, and poor correlations were observed with either sigma sub max or the average cycle time. A model containing both delta sigma and delta sigma (sub in), N sub f = alpha delta sigma (sub in) beta delta sigma gamma, with best fit values of sigma for each cycle type, but the same values of beta and gamam, was found to provide good correlations. Life lines were not greatly different among the cycle types, differing only by a factor of about three. The cp cycle life line was lowest for both test temperatures, however among the other three cycle types there was no consistent ranking. For all test types failure occurred predominately by multiple internal cracking originating at pores. The strong correlation of life with delta sigma may reflect a significant crack growth period in the life of the specimens.

  5. Effect of HVOF Processing Parameters on the Properties of NiCoCrAlY Coatings by Design of Experiments

    NASA Astrophysics Data System (ADS)

    Ruiz-Luna, H.; Lozano-Mandujano, D.; Alvarado-Orozco, J. M.; Valarezo, A.; Poblano-Salas, C. A.; Trápaga-Martínez, L. G.; Espinoza-Beltrán, F. J.; Muñoz-Saldaña, J.

    2014-08-01

    The effect of three principal, independent, high-velocity oxygen fuel (HVOF)-processing parameters on the properties of NiCoCrAlY coatings deposited using commercial powders is reported here. The design of experiments (DoE) technique at a two-level factorial and a central composite rotatable design was used to analyze and optimize the HVOF spraying process. The deposition parameters investigated were (1) fuel flow, (2) oxygen flow, and (3) stand-off distance. The effect of these processing variables was evaluated using selected responses, including porosity and oxide content, residual stresses, and deposition efficiency. Coatings with low porosity as well as with low residual stress were obtained using high fuel-rich conditions at a stand-off distance between 250 and 300 mm. At shorter and longer stand-off distances, respectively, either excessive flattening of splats or un-molten condition occurred, resulting in high levels of porosity and residual stress. The response surface, the empirical relationships among the variables, and the response parameters allowed the selection of optimum deposition parameters and the improvement of coating properties.

  6. Bithermal low-cycle fatigue behavior of a NiCoCrAlY-coated single crystal superalloy

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    Specimens of a single crystal superalloy, PWA 1480, both bare and coated with a NiCoCrAlY alloy, PWA 276, were tested in low-cycle fatigue at 650 and 1050 C, and in bithermal thermomechanical fatigue tests. In the two bithermal test types, tensile strain was imposed at one of the two temperatures and reversed in compression at the other. In the high-strain regime, lives for both bithermal test types approached that for the 650 C isothermal test on an inelastic strain basis, all being controlled by the low ductility of the superalloy at 650 C. In the low-strain regime, coating cracking reduced life in the 650 C isothermal test. The bithermal test imposing tension at 650 C, termed out-of-phase, also produced rapid surface cracking, but in both coated and bare specimens. Increased crack growth rates also occurred for the out-of-phase test. Increased lives in vacuum suggested that there is a large environmental contribution to damage in the out-of-phase test due to the 1050 C exposure followed by tensile straining at the low temperature.

  7. Bithermal Low-Cycle Fatigue Behavior of a NiCoCrAlY-Coated Single Crystal Superalloy

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    Specimens of a single crystal superalloy, PWA 1480, both bare and coated with a NiCoCrAlY alloy, PWA 276, were tested in low-cycle fatigue at 650 and 1050 C, and in bithermal thermomechanical fatigue tests. In the two bithermal test types, tensile strain was imposed at one of the two temperatures and reversed in compression at the other. In the high-strain regime, lives for both bithermal test types approached that for the 650 C isothermal test on an inelastic strain basis, all being controlled by the low ductility of the superalloy at 650 C. In the low-strain regime, coating cracking reduced life in the 650 C isothermal test. The bithermal test imposing tension at 650 C, termed out-of-phase, also produced rapid surface cracking, but in both coated and bare specimens. Increased crack growth rates also occurred for the out-of-phase test. Increased lives in vacuum suggested that there is a large environmental contribution to damage in the out-of-phase test due to the 1050 C exposure followed by tensile straining at the low temperature.

  8. Laser surface forming of AlCoCrCuFeNi particle reinforced AZ91D matrix composites

    NASA Astrophysics Data System (ADS)

    Meng, Guanghui; Yue, T. M.; Lin, Xin; Yang, Haiou; Xie, Hui; Ding, Xu

    2015-07-01

    Traditionally, the laser melt injection (LMI) technique can only be used for forming ceramic particles reinforced metal matrix composites (MMCs) for enhancing surface properties of lightweight engineering materials. In this research, the LMI method was employed to form metal particles reinforced MMCs on AZ91D instead. This was viable because of the unique properties of the AlCoCrCuFeNi high-entropy alloy (HEA) metal particles used. The large difference in melting point between the HEA and the substrate material (AZ91D), and the limited reaction and the lack of fusion between the HEA and Mg have made it possible that a metal particles reinforced AZ91D composite material was produced. The reason of limited reaction was considered mainly due to the relatively high mixing enthalpy between the HEA constituent elements and Mg. Although there was some melting occurred at the particles surface with some solute segregation found in the vicinity close to the surface, intermetallic compounds were not observed. With regard to the wear resistance of the MMCs, it was found that when the volume fraction of the reinforcement phase, i.e. the HEA particles, reached about 0.4, the wear volume loss of the coating was only one-seventh of that of the substrate material.

  9. Effects of Minor Alloying Additions on the Microstructure, Toughness, and Creep Strength of Directionally Solidified NiAl-31Cr-3Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.; Raj, S. V.; Locci, I. E.; Salem, J. A.

    2001-01-01

    A study of the effects of small (0.25 to 1.0 at%) fifth element additions to the structure and mechanical properties of directionally solidified (DS) NiAl-31Cr-3Mo has been undertaken. Essentially all the additions changed the as-DS'ed microstructure from lamellar eutectic grains to cells and, in some cases, introduced NiAl dendrites and/or third phases. In general the alloying additions did not improve strength or toughness over that possessed by the base composition; only Hf and, perhaps Ti, gave a minor increase in elevated temperature creep resistance. The lack of improvement in creep properties is probably due to inability to precipitation harden NiAl.

  10. Effects of Microalloying on the Microstructures and Mechanical Properties of Directionally Solidified Ni-33(at.%)Al-31Cr-3Mo Eutectic Alloys Investigated

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, Sai V.; Locci, Ivan E.; Salem, Jonathan A.

    2002-01-01

    Despite nickel aluminide (NiAl) alloys' attractive combination of oxidation and thermophysical properties, their development as replacements for superalloy airfoils in gas turbine engines has been largely limited by difficulties in developing alloys with an optimum combination of elevated-temperature creep resistance and room-temperature fracture toughness. Alternatively, research has focused on developing directionally solidified NiAl-based in situ eutectic composites composed of NiAl and (Cr,Mo) phases in order to obtain a desirable combination of properties a systematic investigation was undertaken at the NASA Glenn Research Center to examine the effects of small additions of 11 alloying elements (Co, Cu, Fe, Hf, Mn, Nb, Re, Si, Ta, Ti, and Zr) in amounts varying from 0.25 to 1.0 at.% on the elevated-temperature strength and room-temperature fracture toughness of directionally solidified Ni-33Al-31Cr-3Mo eutectic alloy. The alloys were grown at 12.7 mm/hr, where the unalloyed eutectic base alloy exhibited a planar eutectic microstructure. The different microstructures that formed because of these fifth-element additions are included in the table. The additions of these elements even in small amounts resulted in the formation of cellular microstructures, and in some cases, dendrites and third phases were observed. Most of these elemental additions did not improve either the elevated-temperature strength or the room-temperature fracture toughness over that of the base alloy. However, small improvements in the compression strength were observed between 1200 and 1400 K when 0.5 at.% Hf and 0.25 at.% Ti were added to the base alloy. The results of this study suggest that the microalloying of Ni-33Al-31Cr-3Mo will not significantly improve either its elevatedtemperature strength or its room-temperature fracture toughness. Thus, any improvements in these properties must be acquired by changing the processing conditions.

  11. Luminescence, magnetic and vibrational properties of novel heterometallic niccolites [(CH3)2NH2][CrIIIMII(HCOO)6] (MII=Zn, Ni, Cu) and [(CH3)2NH2][AlIIIZnII(HCOO)6]:Cr3+

    NASA Astrophysics Data System (ADS)

    Mączka, Mirosław; Pietraszko, Adam; Pikul, Adam; Hermanowicz, Krzysztof

    2016-01-01

    We report synthesis of three novel heterometallic MOFs, [(CH3)2NH2][CrIIIMII(HCOO)6] with M=Zn (DMCrZn), Ni (DMCrNi) and Cu (DMCrCu), crystallizing in the niccolite type structure. We also successfully synthesized [(CH3)2NH2][AlCu(HCOO)6] (DMAlCu) and [(CH3)2NH2][AlZn(HCOO)6] doped with 5.8 mol% of Cr3+ (DMAlZn: Cr). X-ray diffraction shows that DMCrZn, DMCrNi and DMAlZn: Cr3+ crystallize in the trigonal structure (space group P 3 bar1c) while DMCrCu and DMAlCu crystallize in the monoclinic structure (space group C2/c). Magnetic investigation of the chromium-based niccolites reveals no magnetic order in DMCrZn and ferromagnetic order in DMCrNi and DMCrCu below 23 and 11 K, respectively. Optical studies show that DMCrZn and DMAlZn: Cr samples exhibit efficient emission typical for chromium ions located at sites of strong crystal field with the Dq/B values 2.62 and 2.67, respectively. We also discuss role of geometrical parameters in stability of the perovskite and niccolite structures.

  12. Combination Effect of Dry-Ice Blasting and Substrate Preheating on Plasma-Sprayed CoNiCrAlY Splats

    NASA Astrophysics Data System (ADS)

    Dong, Shujuan; Song, Bo; Hansz, Bernard; Liao, Hanlin; Coddet, Christian

    2013-02-01

    CoNiCrAlY splats were plasma-sprayed on the stainless steel substrate which was pretreated by dry-ice blasting. Only impact marks were distinguished on the glycerol-polluted substrate, while halo donut splats formed on the pretreated substrate because of the cleaning effect of dry-ice blasting on this organic substance. The proportions of different splat types vary as a function of the treatment time of dry-ice blasting. The condensation phenomenon was also detected on the substrate surface accompanying the cleaning effect after the pretreatment of dry-ice blasting. In this study, dry-ice blasting was investigated to be coupled with substrate preheating to control the substrate temperature. It was found that a regular disk-like CoNiCrAlY splat can be obtained as the substrate temperature is higher than dew point temperature.

  13. Effect of Growth Rate on Elevated Temperature Plastic Flow and Room Temperature Fracture Toughness of Directionally Solidified NiAl-31Cr-3Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, S. V.; Locci, I. E.; Salem, J. A.

    1999-01-01

    The eutectic system Ni-33Al-31Cr-3Mo was directionally solidified at rates ranging from 7.6 to 508 mm/h. Samples were examined for microstructure and alloy chemistry, compression tested at 1200 and 1300 K, and subjected to room temperature fracture toughness measurements. Lamellar eutectic grains were formed at 12.7 mm/h; however cellular structures with a radial eutectic pattern developed at faster growth rates. Elevated temperature compression testing between 10(exp -4) to 10(exp -7)/s did not reveal an optimum growth condition, nor did any single growth condition result in a significant fracture toughness advantage. The mechanical behavior, taken together, suggests that Ni-33Al-31Cr-3Mo grown at rates from 25.4 to 254 mm/h will have nominally equivalent properties.

  14. Stress rupture and creep behavior of a low pressure plasma-sprayed NiCoCrAlY coating alloy in air and vacuum

    NASA Technical Reports Server (NTRS)

    Hebsur, M. G.; Miner, R. V.

    1987-01-01

    The creep behavior of a NiCoCrAlY coating alloy in air and vacuum at 660 and 850 C is studied. The microstructure of the coating alloy is described. Analysis of the creep curves reveal that the secondary creep rates, the transition from secondary to tertiary creep, and the strain-to-failure are affected by the environment, preexposure, stress, and temperature. It is observed that the rupture lives of the NiCoCrAlY alloy at 660 and 850 C are greater in air than in vacuum. Several mechanisms that may explain the lack of crack growth from surface-connected pores during tests in air are proposed.

  15. Fabrication and Wear Behavior Analysis on AlCrFeNi High Entropy Alloy Coating Under Dry Sliding and Oil Lubrication Test Conditions

    NASA Astrophysics Data System (ADS)

    Tang, Yipin; Wang, Shouren; Sun, Bin; Wang, Yan; Qiao, Yang

    2016-03-01

    In this paper, AlCrFeNi high entropy alloy coating was fabricated on the surface of Q235 steel using hot pressing sintering process. The coating has the controlled thickness size and excellent mechanical properties. Scanning electron microscopy (SEM), XRD and hardness testing method were used to study the morphology, phase structure and hardness of high entropy alloys coating. The lattice distortion plays a significant role in increasing the hardness. Coating formation mechanism caused by the element diffusion under the hot pressing effect is also discussed in the paper. Simultaneously, the dry sliding and oil lubrication wear tests, wear morphology observation and wear mechanism discussion were completed. As the result shows, AlCrFeNi high entropy alloys coating exhibits superior wear resistance either at dry sliding or oil lubrication tests owing to its hard high entropy solid solution structure.

  16. High-field magnetization of heusler alloys Fe2 XY ( X = Ti, V, Cr, Mn, Fe, Co, Ni; Y = Al, Si)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Korolev, A. V.; Belozerova, K. A.; Weber, H. W.

    2015-10-01

    The magnetization curves of ferromagnetic Heusler alloys Fe2 XY (where X = Ti, V, Cr, Mn, Fe, Co, Ni are transition 3 d elements and Y = Al, Si are the s and p elements of the third period of the Periodic Table) have been measured at T = 4.2 K in the field range H ≤ 70 kOe. It has been shown that the high-field ( H ≥ 20 kOe) magnetization is described within the Stoner model.

  17. Effects of Withdrawal Rate and Temperature Gradient on the Microstructure Evolution in Directionally Solidified NiAl-36Cr-6Mo Hypereutectic Alloy

    NASA Astrophysics Data System (ADS)

    Shang, Zhao; Shen, Jun; Zhang, Jian-Fei; Wang, Lei; Qin, Ling; Fu, Heng-Zhi

    2014-09-01

    The effects of withdrawal rate and temperature gradient on the microstructure and growth interface morphology in directionally solidified Ni-29Al-36Cr-6Mo(at.%) hypereutectic alloy were investigated. Under the temperature gradient of 250 K/cm, well-aligned eutectic microstructure with lamellar morphology was obtained at the withdrawal rate of 6 μm/s. When the withdrawal rate was 10 μm/s, the microstructure changed to Cr(Mo) dendrites + eutectic lamellae. With the increasing withdrawal rate, the interdendritic eutectic growth interface changed from planar to cellular, the number of primary Cr(Mo) dendrites became greater, and the microstructure was refined. When the temperature gradient increased to 600 K/cm, the coupled eutectic growth zone of NiAl-Cr(Mo) alloy was expanded; a well-aligned eutectic microstructure could be obtained at higher rate of 10 μm/s. Furthermore, the planar/cellular transition rate of the interdendritic eutectic growth interface increased. Even at the same withdrawal rate, the number of primary Cr(Mo) dendrites was less and the microstructure was finer under the temperature gradient of 600 K/cm.

  18. Electrolyte loss in corrosion of 30Cr-45Ni-1Al-0.03 Y-Fe alloy for MCFC separator

    SciTech Connect

    Masamura, Katsumi; Ohe, Koichiro; Takemura, Masahiro

    1996-12-31

    To establish high performance of MCFC, a new high corrosion resistant alloy (30%Cr-45%Ni-1 %Al-0.03%Y-Fe) for MCFC separator has been developed. The developed alloy has good corrosion resistance for both anode and cathode environments. On the other hand, one of the main factors to determine the life time of MCFC stack is electrolyte loss. A potential danger of electrolyte loss cased by corrosion of metal components is pointed out. Basic mechanism of electrolyte loss is proposed according to following reactions. High Cr content alloy such as type 310S(25%Cr-20%Ni) has disadvantages in view of electrolyte loss in spite of high corrosion resistance. It is said that the dissolution of Cr ion into electrolyte is detrimental for electrolyte loss, because a mole of CrO{sub 4}{sup 2+} ion combines 2 moles of K{sup +} ions as K{sub 2}CrO{sub 4}, while a mole of Fe{sup 3+} ion combine a mole of Li{sup +} ion as LiFeO{sub 2}. To understand the mechanism of electrolyte loss due to corrosion of metal component, the distribution of metal ions in oxide and molten salt were studied.

  19. A Successful Synthesis of the CoCrFeNiAl0.3 Single-Crystal, High-Entropy Alloy by Bridgman Solidification

    SciTech Connect

    Ma, S. G.; Zhang, S. F.; Gao, M. C.; Liaw, P. K.; Zhang, Y.

    2013-08-22

    For the first time, a face-centered-cubic, single-crystal CoCrFeNiAl{sub 0.3} (designated as Al0.3), high-entropy alloy (HEA) was successfully synthesized by the Bridgman solidification (BS) method, at an extremely low withdrawal velocity through a constant temperature gradient, for which it underwent two BS steps. Specially, at the first BS step, the alloy sample underwent several morphological transitions accompanying the crystal growth from the melt. This microstructure evolves from as-cast dendrites, to equiaxed grains, and then to columnar crystals, and last to the single crystal. In particular, at the equiaxed-grain region, some visible annealing twins were observed, which indicates a low stacking fault energy of the Al0.3 alloy. Although a body-centered- cubic CoCrFeNiAl (Al1) HEA was also prepared under the same conditions, only a single columnar-crystal structure with instinctively preferential crystallographic orientations was obtained by the same procedure. A similar morphological transition from dendrites to equiaxed grains occurred at the equiaxed-grain region in Al1 alloy, but the annealing twins were not observed probably because a higher Al addition leads to a higher stacking fault energy for this alloy.

  20. Microstructural Characterization of a Directionally-Solidified Ni-33 (at. %)Al-31Cr-3Mo Eutectic Alloy as a Function of Withdrawal Rate

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Locci, I. E.; Whittenberger, J. D.; Salem, J. A.

    2000-01-01

    The Ni-33 (at. %)Al-3lCr-3Mo eutectic alloy was directionally-solidified (DS) at different rates, V(sub I), varying between 2.5 to 508 mm/ h. Detailed qualitative and quantitative metallographic and chemical analyses were conducted on the directionally-solidified rods. The microstructures consisted of eutectic colonies with parallel lamellar NiAl/(Cr,Mo) plates for solidification rates at and below 12.7 mm/ h. Cellular eutectic microstructures were observed at higher solidification rates, where the plates exhibited a radial pattern. The microstructures were demonstrated to be fairly uniform throughout a 100 mm length of the DS zone by quantitative metallography. The average cell size, bar-d, decreased with increasing growth rate to a value of 125 microns at 508 mm/ h according to the relation bar-d (microns) approx. = 465 V(sup -0.22, sub I), where V(sub I) is in mm/ h. Both the average NiAl plate thickness, bar-Delta(sub NiAl), and the interlamellar spacing, bar-lambda, were observed to be constant for V(sub I) less than or = 50.8 mm/ h but decreased with increasing growth rate above this value as 0.93 bar-Delta(sub NiAl)(microns) = 61.2 V(sup -0.93, sub I) and bar-lambda (microns) = 47.7 V(sup -0.64, sub I), respectively. The present results are detailed on a microstructural map. Keywords Optical microscopy, microstructure, compounds intermetallic, directional solidification

  1. Surface characteristics and protein adsorption on combinatorial binary Ti-M (Cr, Al, Ni) and Al-M (Ta, Zr) library films.

    PubMed

    Bai, Zhijun; Filiaggi, M J; Sanderson, R J; Lohstreter, L B; McArthur, M A; Dahn, J R

    2010-02-01

    Systematic studies of protein adsorption onto metallic biomaterial surfaces are generally lacking. Here, combinatorial binary library films with compositional gradients of Ti(1-x)Cr(x), Ti(1-x)Al(x), Ti(1-x)Ni(x) and Al(1-x)Ta(x), (0 Al(1-y)Zr(y) (0 < y <0.5) as well as corresponding pure metal films were sputtered onto clean Si surfaces. Bulk and surface chemistry, film microstructure, and surface roughness were subsequently correlated to fibrinogen or albumin adsorption measured using a high throughput wavelength dispersive spectroscopy technique. X-ray diffraction revealed these binary films to have crystalline phases present primarily at either extreme of the compositional library and an amorphous zone dominating along the gradient. These mirror-like films were generally found by atomic force microscopy to have a roughness of less than 8 nm, with any relative increases in roughness consistent with the development of crystalline phases. Surface chemistry by quantitative high-resolution X-ray photoelectron spectroscopy differed significantly from bulk film composition as measured by electron microprobe, with TiO(2) and Al(2)O(3) preferentially forming on the binary film surfaces. Correspondingly, protein adsorption onto these films closely correlated with their surface oxide fractions. Aluminum deposited as either a constant-composition film or as part of a binary library consistently adsorbed the least amount of albumin and fibrinogen, with alumina-enrichment of the surface oxide correlating with this adsorption. Overall, this combinatorial materials approach coupled with high-throughput surface analytical methods provides an efficient method of screening potential metallic biomaterials that may enable as well systematic studies of surface properties driving protein adsorption on these metal / metal oxide systems. PMID:19235218

  2. Erosion-corrosion of as-plasma-sprayed and laser-remelted NiCrAlY bond coats in working conditions of a coal-fired boiler

    SciTech Connect

    Sidhu, B.S.; Prakash, S.

    2008-01-15

    Ni-22Cr-10Al-1Y plasma spray coating has been formulated on boiler tube steels. namely, low-carbon steel ASTM SA210-Grade A1. 1Cr-0.5Mo steel ASTM SA213-T-11, and 2.25Cr-1Mo steel ASTM SA213-T-22. The coated steels also have been laser-remelted using a Nd:YAG laser. The degradation behavior of as-sprayed and laser-remelted coatings have been evaluated in actual conditions in a coal-fired boiler for 1,000 h at 755{sup o}C. The laser remelting has been found to be effective to increase the degradation resistance of plasma-sprayed boiler steels. ASTM SA213-T-22-coated and laser-remelted steel has proved to be most effective in resistance to degrading species.

  3. Effect of scanning speeds on microstructure and wear behavior of laser-processed NiCr-Cr3C2-MoS2-CeO2 on 38CrMoAl steel

    NASA Astrophysics Data System (ADS)

    Sun, Guifang; Tong, Zhaopeng; Fang, Xiaoyu; Liu, Xiaojun; Ni, Zhonghua; Zhang, Wei

    2016-03-01

    Self-lubricating wear-resistant NiCr-Cr3C2-MoS2-CeO2 layers were fabricated on 38CrMoAl extruder screws by laser processing. The effect of scanning speeds on microstructure, phases, microhardness, and wear behavior was investigated. The obtained results indicate that the laser-processed layers had fine and nonuniform microstructures with undissolved MoS2 particles distributed on the matrix. With an increase of the laser-scanning speeds, the microstructures changed from hypoeutectic to hypereutectic, volume fraction of martensite increased, microhardness increased, and thickness and friction coefficients of the layers decreased. Wear resistance of the optimized layer was increased by 29.76 times compared with that of the substrate. The undissolved MoS2 was separated from the matrix on loading. In addition to the grain-refining and solution-strengthening effects, oxide films formed on the surface of the layers shielded them and enhanced their wear resistance. The crack or fracture behavior of the laser-processed layers on loading was determined by its toughness, which also had an important effect on the wear behavior of the processed layers.

  4. Microstructures and Mechanical Performance of Plasma-Nitrided Al0.3CrFe1.5MnNi0.5 High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Tang, Wei-Yeh; Chuang, Ming-Hao; Lin, Su-Jien; Yeh, Jien-Wei

    2012-07-01

    This study investigates the effect of plasma nitriding at 798 K (525 °C) on microstructures and the mechanical performance of Al0.3CrFe1.5MnNi0.5 high-entropy alloys (HEAs) obtained using different cast and wrought processing. All the alloys can be well nitride, with a thickness of around 80 μm, and attain a peak hardness level around Hv 1300 near the surface. The main nitride phases are CrN, AlN, and (Mn, Fe)4N. Those of the substrates are bcc, fcc, Al-, and Ni-rich B2 precipitates, and ρ phase. Their relative amounts depend on the prior processing and also change under the heat treatment during nitriding. The formation of ρ phase during nitriding could in-situ harden the substrate to attain the suitable level required for wear applications. This gives the advantage in simplifying the processing for making a wear-resistance component or a mold since austenitizing, quench hardening, and tempering required for steels such as SACM and SKD steels are no longer required and final finishing can be accomplished before nitriding. Nitrided Al0.3CrFe1.5MnNi0.5 samples have much better wear resistance than un-nitrided ones by 49 to 80 times and also exhibit superior adhesive wear resistance to conventional nitrided alloys: nitriding steel SACM-645 (AISI 7140), 316 stainless steel, and hot-mold steel SKD-61 (AISI H13) by 22 to 55 times depending on prior processing. The superiority is due to the fact that the present nitrided alloys possess a much thicker highly hardened layer than the conventional alloys.

  5. Diffusion and phase transformation on interface between substrate and NiCrAlY in Y-PSZ thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Chen, H.; Jin, Z.; Liu, C.; Zhou, K.

    2004-12-01

    NiCrAlY/Y2O3-Y-PSZ (yttria-partially stabilized zirconia) thermal barrier coatings were developed on a superalloy (Ni-10Co-9Cr-7W-5Al, wt.%) surface. The superalloys were first coated with a bond coat of Ni-19Cr-8Al-0.5Y (wt.%) alloy that was deposited by low-pressure plasma spraying and then covered with a top coat of ZrO2-8wt.%Y2O3 by air plasma spraying. The microstructure near the interface was analyzed using an optical microscope, a scanning electron microscope, microhardness measurements, and x-ray diffraction, and the phases of composition were measured using an electron probe microanalyzer after exposure at 1100°C for different times in air or a vacuum. The reaction processes also were simulated using diffusion-controlled transformation (DICTRA) software in which diffusion was considered as being only the γ phase, and the γ‧ phase was treated as spheroidal particles in γ. From the authors’ results, it can be concluded that a γ‧-phase layer is observed at the interface between substrate and bond coat, and its thickness increases with increasing exposure times in air at 1100 °C. This layer showed good cohesion with the substrate and bond coat. It can also be concluded that the formation of the γ‧-phase layer can be predicted from DICTRA simulation. The simulation also shows the same trend of the composition profiles as experimental data.

  6. High-Temperature Oxidation and Hot Corrosion Studies on NiCrAlY Coatings Deposited by Flame-Spray Technique

    NASA Astrophysics Data System (ADS)

    Rana, Nidhi; Mahapatra, Manas Mohan; Jayaganthan, R.; Prakash, Satya

    2015-06-01

    The NiCrAlY coatings deposited by flame-spray technique on the superalloy substrate were oxidized in the presence of air and Na2SO4 + V2O5 salt at 900 °C for 100 cycles. The kinetics of oxidation showed that the coatings deposited by flame-spray technique possess better oxidation resistance compared with coatings deposited by high-velocity oxy fuel (HVOF)-sprayed technique. The oxidized coatings were further characterized by XRD, FESEM/EDS, and x-ray mapping techniques. The mechanisms of the oxidation and hot corrosion were substantiated by analyzing the results obtained from the various characterization techniques.

  7. An investigation of environmental influence on the creep behavior of a low pressure plasma sprayed NiCoCrAlY alloy

    NASA Technical Reports Server (NTRS)

    Hebsur, M. G.; Miner, R. V.

    1985-01-01

    Low pressure sprayed MCrAlY overlay coatings are currently being used on advanced single crystal superalloy blades for gas turbine engines. Many studies were made on the influence of coatings on the mechanical properties of superalloys in oxidizing or hot-corroding environments, but very few on the properties of the bulk coating alloy itself. The creep behavior of a typical NiCoCrAlY alloyd (PWA 276) was studied in air and vacuum. The as-received low pressure plasma sprayed NiCoCrAlY plates were heat treated for 4 h at 1080 C followed by 32 h at 870 C, the heat treatment applied to coated superalloy parts. Standard creep specimens 12.7 mm long and 3.2 mm in diameter were then machined. Constant load creep-rupture tests were performed in air and vacuum at 650, 850, and 1050 C and various initial stresses. In addition, some specimens were preoxidized at 1050 C for 100 h prior to testing. Results are briefly discussed.

  8. High-temperature tribological properties of NiCoCrAlY-WSe2-BaF2·CaF2 solid lubricant coatings prepared by plasma spraying

    NASA Astrophysics Data System (ADS)

    Chen, X. H.; Yuan, X. J.; Xia, J.; Yu, Z. H.

    2015-12-01

    In this paper, NiCoCrAlY-WSe2-BaF2·CaF2 solid lubricant coatings were produced on a substrate by plasma spray and investigated at the high temperature, such as 500 °C and 800 °C. The structure of the coatings was characterized using XRD pattern and scanning electron microscopy. The TC1 (83wt% NiCoCrAlY) coating has a low friction coefficient at 500C, where the WSe2 is a good solid lubricant. The TC2 (65wt% NiCoCrAlY) coating has the low friction coefficient (0.279) at 800°C, due to the formation of BaCrO4 on the surfaces. As a result, the TC2 coating has the optimal tribological property in the wide temperature.

  9. Magnetic properties of the mixed spinel NiAl 2 xCr xFe 2-3 xO 4

    NASA Astrophysics Data System (ADS)

    Chhaya, Urvi V.; Trivedi, Bimal S.; Kulkarni, R. G.

    1999-01-01

    The crystal and magnetic properties of the Al and Cr co-substituted disordered spinel series NiAl 2 xCr xFe 2-3 xO 4 ( x=0.1-0.6) are investigated by means of X-ray diffraction, magnetization, Mössbauer effect and AC susceptibility measurements. The lattice constants are determined and the applicability of Vegards law has been tested. The variation of the saturation magnetic moment per formula unit measured at 77 K with the Al-Cr content is satisfactorily explained on the basis of Néel's collinear spin ordering model for x=0.1-0.2. The Mössbauer spectra at 300 K have been fitted with two sextets in the ferrimagnetic state corresponding to Fe 3+ at tetrahedral (A) and octahedral (B) sites for x⩽0.4. Mössbauer results confirm a collinear ferrimagnetic structure for x=0.1-0.2. The nB values obtained from magnetization and Mössbauer data for x=0.3-0.6 display a discrepancy between them, thus exhibiting a significant canting on the B-site which is explained satisfactorily on the basis of the non-collinear spin ordering model of random canting.The Curie temperature obtained from AC susceptibility decreases nearly linear with x from x=0.1-0.4 and it shows a sudden change near x⩾0.4 indicating a change in magnetic structure.

  10. Microstructure Investigation of Directionally Solidified NiAl-Cr(Mo)- xDy ( x = 0, 0.1 wt.%) Hypereutectic Alloys at Different Withdrawal Rates

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Shen, Jun; Shang, Zhao; Zhang, Jian-Fei; Du, Yu-Jun; Fu, Heng-Zhi

    2013-11-01

    The microstructures of directionally solidified Ni-31Al-32Cr-6Mo (at.%)- xDy ( x = 0, 0.1 wt.%) hypereutectic alloys were studied at different withdrawal rates. The results show that the microstructure changes from the planar eutectic to the cellular eutectic and the volume fraction of the primary Cr(Mo) dendrites decreases for the Dy-free alloy with the withdrawal rate varying from 6 μm/s to 30 μm/s. The addition of 0.1 wt.% Dy promotes the planar-to-cellular transition. Moreover, the white Dy-containing phase does not form in the alloy for the planar interface growth (6 μm/s), but it can occur in the boundary of eutectic cells for the cellular interface growth (30 μm/s). A sketchy model of the planar and cellular growth is supposed to interpret it.

  11. Trace element (Al, As, B, Ba, Cr, Mo, Ni, Se, Sr, Tl, U and V) distribution and seasonality in compartments of the seagrass Cymodocea nodosa.

    PubMed

    Malea, Paraskevi; Kevrekidis, Theodoros

    2013-10-01

    Novel information on the biological fate of trace elements in seagrass ecosystems is provided. Al, As, B, Ba, Cr, Mo, Ni, Se, Sr, Tl, U and V concentrations in five compartments (blades, sheaths, vertical rhizomes, main axis plus additional branches, roots) of the seagrass Cymodocea nodosa, as well as in seawater and sediments from the Thessaloniki Gulf, Greece were determined monthly. Uni- and multivariate data analyses were applied. Leaf compartments and roots displayed higher Al, Mo, Ni and Se annual mean concentrations than rhizomes, B was highly accumulated in blades and Cr in sheaths; As, Ba, Sr and Tl contents did not significantly vary among plant compartments. A review summarizing reported element concentrations in seagrasses has revealed that C. nodosa sheaths display a high Cr accumulation capacity. Most element concentrations in blades increased in early mid-summer and early autumn with blade size and age, while those in sheaths peaked in late spring-early summer and autumn when sheath size was the lowest; elevated element concentrations in seawater in late spring and early-mid autumn, possibly as a result of elevated rainfall and associated run-off from the land, may have also contributed to the observed variability. Element concentrations in rhizomes and roots generally displayed a temporary increase in late autumn, which was concurrent with high rainfall, low wind speed associated with reduced hydrodynamism, and elevated sediment element levels. The bioaccumulation factor based on element concentrations in seagrass compartments and sediments was lower than 1 except for B, Ba, Mo, Se and Sr in all compartments, Cr in sheaths and U in roots. Blade V concentration positively correlated with sediment V concentration, suggesting that C. nodosa could be regarded as a bioindicator for V. Our findings can contribute to the design of biomonitoring programs and the development of predictive models for rational management of seagrass meadows. PMID:23838054

  12. Microstructure studies of air-plasma-spray-deposited CoNiCrAlY coatings before and after thermal cyclic loading for high-temperature application

    NASA Astrophysics Data System (ADS)

    Kumar, Dipak; Pandey, K. N.; Das, Dipak Kumar

    2016-08-01

    In the present study, bond-coats for thermal barrier coatings were deposited via air plasma spraying (APS) techniques onto Inconel 800 and Hastelloy C-276 alloy substrates. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and atomic force microscopy (AFM) were used to investigate the phases and microstructure of the as-sprayed, APS-deposited CoNiCrAlY bond-coatings. The aim of this work was to study the suitability of the bond-coat materials for high temperature applications. Confirmation of nanoscale grains of the γ/γ'-phase was obtained by TEM, high-resolution TEM, and AFM. We concluded that these changes result from the plastic deformation of the bond-coat during the deposition, resulting in CoNiCrAlY bond-coatings with excellent thermal cyclic resistance suitable for use in high-temperature applications. Cyclic oxidative stability was observed to also depend on the underlying metallic alloy substrate.

  13. Investigation on the Interactions of NiCR and NiCR-2H with DNA

    PubMed Central

    Chitranshi, Priyanka; Chen, Chang-Nan; Jones, Patrick R.; Faridi, Jesika S.; Xue, Liang

    2010-01-01

    We report here a biophysical and biochemical approach to determine the differences in interactions of NiCR and NiCR-2H with DNA. Our goal is to determine whether such interactions are responsible for the recently observed differences in their cytotoxicity toward MCF-7 cancer cells. Viscosity measurement and fluorescence displacement titration indicated that both NiCR and NiCR-2H bind weakly to duplex DNA in the grooves. The coordination of NiCR-2H with the N-7 of 2′-deoxyguanosine 5′-monophosphate (5′-dGMP) is stronger than that of NiCR as determined by 1H NMR. NiCR-2H, like NiCR, can selectively oxidize guanines present in distinctive DNA structures (e.g., bulges), and notably, NiCR-2H oxidizes guanines more efficiently than NiCR. In addition, UV and 1H NMR studies revealed that NiCR is oxidized into NiCR-2H in the presence of KHSO5 at low molar ratios with respect to NiCR (≤4). PMID:20671951

  14. The effects of Ni, Mo, Ti and Si on the mechanical properties of Cr free Mn steel (Fe-25Mn-5Al-2C)

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.

    1982-01-01

    The FeMnAlC alloys may hold potential as Cr-free replacements for high strategic material iron base superalloys, but little is known about their intermediate temperature (650 C to 870 C) mechanical properties. The effects of alloying elements on the mechanical properties of model FeMnAlC alloys were studied. Results showed that modified FeMnAlC alloys had promising short term, intermediate temperature properties but had relatively poor stress rupture lives at 172 MPa and 788 C. Room temperature and 788 C tensile strength of FeMnAlC alloys were better than common cast stainless steels. Changes in room temperature tensile and 788 C tensile strength and ductility, and 788 C stress rupture life were correlated with changes in Ni, Mo, Ti, and Si levels due to alloying effects on interstitial carbon levels and carbide morphology. Fe-25Mn-5Al-2C had a very poor stress rupture life at 172 MPa and 788 C. Addition of carbide-forming elements improved the stress rupture life.

  15. The Mechanical and Corrosion Behaviors of As-cast and Re-melted AlCrCuFeMnNi Multi-Component High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Soare, Vasile; Mitrica, Dumitru; Constantin, Ionut; Popescu, Gabriela; Csaki, Ioana; Tarcolea, Mihai; Carcea, Ioan

    2015-04-01

    A multi-component AlCrCuFeMnNi high-entropy alloy, prepared by vacuum induction melting, was investigated for structural, mechanical, and corrosion characteristics, before and after the re-melting process. Optical microscopy analysis revealed a dendritic solidification behavior. The interdendritic area contains two main phases and occasionally small hard phases. The re-melting process produced a finer dendritic structure, with rounded dendrites and reduced interdendritic hard phases. The SEM-EDAX analysis showed that the dendrite region contains a Widmanstatten type of structure and are composed of Cr-Fe rich phases, whereas the interdendrite region contains Cu and Mn rich phases. XRD analysis revealed two disordered BCC type A2 structures with high Cr and Fe content and an FCC A12 type of structure for the Cu and Mn rich interdendritic phase. The lattice constants, determined by X-ray diffraction, are 2.87 and 2.91 Å for the A2 phases and 3.67 Å for A1 phase. The Vickers micro hardness increased with the homogeneity of the alloy, having a maximum value of 4370 MPa for the re-melted sample. Corrosion tests carried out in 3.5 wt pct sodium chloride aerated solution indicated that the corrosion resistance improved with the re-melting process, being 1.5 to 2 times better than that of 304 stainless steel.

  16. Cyclic and isothermal oxidation behavior at 1100 and 1200 C of Ni-20Cr, Ni-20Cr-3Mn, Ni-20Cr-3Si, and Ni-40Cr alloys

    NASA Technical Reports Server (NTRS)

    Lowell, C. E.

    1973-01-01

    Alloys of Ni-20Cr, Ni-20Cr-3Mn, Ni-20Cr-3Si, and Ni-40Cr were cyclically oxidized at 1100 and 1200 C for up to 100 hours. Oxidation behavior was judged by sample thickness and weight change, metallography, diffraction, and microprobe analysis. The least attacked were Ni-40Cr and Ni-20Cr-3Si. The alloy Ni-20Cr-3Mn was much less attacked than Ni-20Cr, but more than the other alloys. The formation of Cr2O3 accounted for the increased resistance of Ni-Cr and Ni-20Cr-3Si, and the formation of MnCr2O4 accounts for the improvement in Ni-20Cr-3mn over Ni-20Cr.

  17. The effects of Cr, Co, Al, Mo and Ta on the cyclic oxidation behavior of a prototype cast Ni-base superalloy based on a 2(5) composite statistically designed experiment

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.

    1984-01-01

    A series of cast Ni-base superalloys were systematically varied at selected levels of Co, Cr, Mo, Ta, and Al. The elemental levels varied were Mo, 0 to 4 percent; Cr, 6 to 18 percent; Co, 0 to 20 percent, Ta, 0 to 8 percent; and Al, 3.25 to 6.25 percent. The cyclic oxidation resistance was determined from specific weight change data as a function of time for 1 hr cycles in static air at 1100 C. The significant terms in decreasing order of their importance were Al, Ta, Cr2, Al-Cr, Cr-Co, Co2, Al-Mo, Cr-Mo, Al-Al, and Mo-Ta. The Al term alone accounted for close to 82 percent of the explained variability. The estimating equation showed that the Al level was the most important and should be at its 6.25 wt % maximum value. The Mo and Ta levels should also be at their maximum 4 and 8 wt % respectively. The cobalt composition should be as low as possible, i.e., 0 wt%. The Cr level optimum varies depending on the other 4 levels. The X-ray diffaction results indicate the most protective scales are alumina/aluminate spinel stabilizized with a tri-rutile oxide high in Ta and Mo.

  18. Laser-clad Ni70Al20Cr7Hf3 alloys with extended solid solution of Hf: Part I. Microstructure evolution

    NASA Astrophysics Data System (ADS)

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

    1989-11-01

    Coatings for superalloys for extended service in atmospheres at high temperature are of great interest at present. The addition of reactive elements (RE’s) such as Hf to these coatings has a pronounced effect on their high-temperature oxidation resistance. A laser-cladding technique was used to produce Ni-Al-Cr-Hf alloys with an extended solid solution of Hf in a nearstoichiometric Ni3Al matrix. A 10 kW CO2 laser with mixed powder feed was used for the cladding process. Scanning electron microscope (SEM), transmission electron microscope (TEM), and scanning transmission electron microscope (STEM) were employed for studies of microstructural evolution of alloys produced during the laser-cladding process. Microstructural studies reveal the formation of dendrites with a solid solubility of about 11 to 14 wt pct Hf and also a eutectic structure. Convergent-beam techniques and X-ray spectroscopy have been applied to characterize the phases formed during the cladding process.

  19. High-Temperature Tensile Strength of Al10Co25Cr8Fe15Ni36Ti6 Compositionally Complex Alloy (High-Entropy Alloy)

    NASA Astrophysics Data System (ADS)

    Daoud, H. M.; Manzoni, A. M.; Wanderka, N.; Glatzel, U.

    2015-06-01

    Homogenizing at 1220°C for 20 h and subsequent aging at 900°C for 5 h and 50 h of a novel Al10Co25Cr8Fe15Ni36Ti6 compositionally complex alloy (high-entropy alloy) produces a microstructure consisting of an L12 ordered γ' phase embedded in a face-centered cubic solid-solution γ matrix together with needle-like B2 precipitates (NiAl). The volume fraction of γ' phase is ~46% and of needle-like B2 precipitates <5%, which is in accordance with the prediction of calculation of phase diagram method (CALPHAD using Thermo-Calc software with TTNi7 database; Thermo-Calc Software, Stockholm, Sweden). The high-temperature tensile tests were carried out at room temperature, 600°C, 700°C, 800°C, and 1000°C. The tensile strength as well as the elongation to failure of both heat-treated specimens is very high at all tested temperatures. The values of tensile strength has been compared with literature data of well-known Alloy 800H and Inconel 617, and is discussed in terms of the observed microstructure.

  20. Influence of deformation on the structure and the mechanical properties of a high-entropy Fe25Cr20Ni20Co10Mn15Al10 alloy

    NASA Astrophysics Data System (ADS)

    Gorban', B. F.; Nazarenko, V. A.; Danilenko, N. I.; Karpets, M. V.; Krapivka, N. A.; Firstov, S. A.; Makarenko, E. S.

    2014-10-01

    The phase composition, the hardness, and the elasticity modulus of a high-entropy Fe25Cr20Ni20Co10Mn15Al10 alloy have been studied in the as-cast state, after rolling deformation, and after subsequent high-temperature annealing. The alloy consists of the following two phases: solid substitutional solutions with bcc and fcc crystal lattices; in the as-cast state and after annealing the bcc solid solution is ordered according to B2 type (CsCl). The mixture rule is applied for the calculation of the electron density, the atomic radius, and the melting point at grain boundaries and in the grain volume of the alloy after deformation and annealing. The obtained data demonstrate that the alloy is thermally stable.

  1. Microstructure and Tensile Behavior of Al8Co17Cr17Cu8Fe17Ni33 (at.%) High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Daoud, H. M.; Manzoni, A.; Völkl, R.; Wanderka, N.; Glatzel, U.

    2013-12-01

    Microstructure evolution and tensile behavior of the high-entropy alloy Al8Co17Cr17Cu8Fe17Ni33 (at.%) are investigated at room temperature and at 500°C in the as-cast state and under different heat-treatment conditions. Detailed microstructural characterizations are carried out using optical microscopy, scanning electron microscopy, and transmission electron microscopy. The equilibrium phase evolution as a function of temperature was calculated using the Thermo-Calc software (Thermo-Calc Software, Stockholm, Sweden) integrated with TTNi-7 database. The observed majority phase is a face-centered cubic solid solution for all tested specimens. Tensile ductility at room temperature and at elevated temperature is enhanced by heat treatment at 1150°C. An embrittlement phenomenon has been observed after a heat treatment at 700°C resulting in significant degradation in tensile properties.

  2. The effect of anti-phase domain size on the ductility of a rapidly solidified Ni3Al-Cr alloy

    NASA Technical Reports Server (NTRS)

    Carro, G.; Bertero, G. A.; Wittig, J. E.; Flanagan, W. F.

    1989-01-01

    Tensile tests on splat-quenched Ni3Al-Cr alloys showed a sharp decrease in ductility with long-time annealing. The growth of the initially very-fine-size anti-phase domains showed a tenuous correlation with ductility up to a critical size, where ductility was lost. The grain size was relatively unaffected by these annealing treatments, but the grain-boundary curvature decreased, implying less toughness. An important observation was that, for the longest annealing time, a chromium-rich precipitate formed, which the data indicate could be a boride. Miniaturized tensile tests were performed on samples which were all obtained from the same splat-quenched foil, and the various domain sizes were controlled by subsequent annealing treatments.

  3. Effects of Rhenium Addition on the Temporal Evolution of the Nanostructure and Chemistry of a Model Ni-Cr-Al Superalloy. 2; Analysis of the Coarsening Behavior

    NASA Technical Reports Server (NTRS)

    Yoon, Kevin E.; Noebe, Ronald D.; Seidman, David N.

    2007-01-01

    The temporal evolution of the nanostructure and chemistry of a model Ni-8.5 at.% Cr-10 at.% Al alloy with the addition of 2 at.% Re was studied using transmission electron microscopy and atom-probe tomography in order to measure the number density and mean radius of the y' (LIZ) precipitates and the chemistry of the y'-precipitates and the y (fcc)-matrix. In this article, the coarsening behavior of the y'-precipitates is discussed in detail and compared with the Umantsev-Olson model for multi-component alloys. In addition, the experimental results are evaluated with PrecipiCalc(TradeMark) simulations. The results show that the diffusivities of the solute elements play a major role in the coarsening behavior of the y'-precipitates and that the addition of Re retards the coarsening kinetics and stabilizes the spheroidal morphology of the precipitates by reducing the interfacial energy.

  4. Effects of Rhenium Addition on the Temporal Evolution of the Nanostructure and Chemistry of a Model Ni-Cr-Al Superalloy. 1; Experimental Observations

    NASA Technical Reports Server (NTRS)

    Yoon, Kevin E.; Noebe, Ronald D.; Seidman, David N.

    2006-01-01

    The temporal evolution of the nanostructure and chemistry of a model Ni-8.5 at.% Cr-10 at. % Al alloy, with the addition of 2 at.% Re, aged at 1073 K from 0.25 to 264 h, was studied. Transmission electron microscopy and atom-probe tomography were used to measure the number density and mean radius of the gamma prime (L1(sub 2) structure)-precipitates and the chemistry of the gamma prime-precipitates and the gamma (face-centered cubic)-matrix, including the partitioning behavior of all alloying elements between the gamma- and gamma prime-phases and the segregation behavior at gamma/gamma prime interfaces. The precipitates remained spheroidal for an aging time of up to 264 h and, unlike commercial nickel-based superalloys containing Re, there was not confined (nonmonotonic) Re segregation at the gamma/gamma prime interfaces.

  5. Effects of temperature on serrated flows of Al0.5CoCrCuFeNi high-entropy alloy

    DOE PAGESBeta

    Chen, Shuying; Xie, Xie; Chen, Bilin; Qiao, Junwei; Zhang, Yong; Ren, Yang; Dahmen, Karin A.; Liaw, Peter K.

    2015-08-14

    Compression behavior of the Al0.5CoCrCuFeNi high-entropy alloy (HEA) was studied at different temperatures from 673K to 873K at a low strain rate of 5 x 10-5/s to investigate the temperature effect on the mechanical properties and serration behavior. The face-centered cubic (FCC) structure is confirmed at the lower temperature of 673 K and 773 K, and a structure of mixed FCC and body-centered cubic (BCC) is identified at a higher temperature of 873 K after compression tests using high-energy synchrotron X-ray diffraction. As a result, by comparing the stress-strain curves at different temperatures, two opposite directions of serrations types weremore » found, named upward serrations appearing at 673 K and 773 K and downward serrations at 873 K, which may be due to dynamic strain aging.« less

  6. Effects of temperature on serrated flows of Al0.5CoCrCuFeNi high-entropy alloy

    SciTech Connect

    Chen, Shuying; Xie, Xie; Chen, Bilin; Qiao, Junwei; Zhang, Yong; Ren, Yang; Dahmen, Karin A.; Liaw, Peter K.

    2015-08-14

    Compression behavior of the Al0.5CoCrCuFeNi high-entropy alloy (HEA) was studied at different temperatures from 673K to 873K at a low strain rate of 5 x 10-5/s to investigate the temperature effect on the mechanical properties and serration behavior. The face-centered cubic (FCC) structure is confirmed at the lower temperature of 673 K and 773 K, and a structure of mixed FCC and body-centered cubic (BCC) is identified at a higher temperature of 873 K after compression tests using high-energy synchrotron X-ray diffraction. As a result, by comparing the stress-strain curves at different temperatures, two opposite directions of serrations types were found, named upward serrations appearing at 673 K and 773 K and downward serrations at 873 K, which may be due to dynamic strain aging.

  7. The structure and physical-mechanical properties of the heat-resistant Ni-Co-Cr-Al-Y intermetallic coating obtained using rebuilt plasma equipment

    NASA Astrophysics Data System (ADS)

    Tarasenko, Yu. P.; Tsareva, I. N.; Berdnik, O. B.; Fel, Ya. A.; Kuzmin, V. I.; Mikhalchenko, A. A.; Kartaev, E. V.

    2014-12-01

    Results of a study of the structure, physico-mechanical properties, and the resistance to heat of Ni-Co-Cr-Al-Y intermetallic coatings obtained by powder spraying on the standard UPU-3D plasma spray facility (plasmatron with self-establishing arc length) and on the rebuilt facility equipped with the enhanced-power PNK-50 plasmatron with sectionalized inter-electrode insert, are reported. Coatings of higher density ( ρ = 7.9 g/cm3) and higher microhardness (H μ = 770 kg-force/mm2) with lower porosity values ( P = 5.7 %, P c = 5.1 %, and P 0 = 0.6 %) and high resistance to heat ((M - M0)/M0 = 1.2) were obtained. The developed coating is intended for protection of the working surfaces of turbine engine blades in gas-turbine power plants.

  8. A NiCrAl pressure cell up to 4.6 GPa and its application to cuprate and pnictide superconductors

    NASA Astrophysics Data System (ADS)

    Fujiwara, Naoki; Uwatoko, Yoshiya; Matsumoto, Takehiko

    2013-06-01

    A NiCrAl-CuBe hybrid cell has been paid much attention because its maximum pressure goes beyond 3 GPa despite its large sample space. In the previous pressurizing trials for this pressure cell, we reached 4.0 GPa under a steady load of 15 ton. In the present trial, we have succeeded in reaching 4.6 GPa by using a short Teflon capsule as a pressure-mediation-liquid container. The pressure efficiency at 15 ton was 75 %. The maximum expansion of the inner diameter of the NiCrAl cylinder was 5 %, suggesting that 4.6 GPa is the upper limit of pressure. To keep high pressure above 4 GPa, a steady load control is needed: a pressure of 4.0 GPa under a steady load decreased to 3.7 GPa after the pressure cell was clamped and the steady load was released. The pressure cell is available to various experiments that need a large sample space. We have applied this pressure cell to nuclear magnetic resonance (NMR) measurements on cuprate and pnictide superconductors, such as Sr2Ca12Cu24O41, LaFeAsO1-xFx, and CaFe1-xCoxAsF. These compounds have superconducting layers, and Tcs of these compounds are enhanced by pressure application. We review what happens at optimal pressure in electric and/or magnetic properties on a microscopic level. Grant-in-Aid (Grant No. 23340101) from the Ministry of Education, Science and Culture, Japan.

  9. NiAl-base composite containing high volume fraction of AlN for advanced engines

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan (Inventor); Whittenbeger, John D. (Inventor); Lowell, Carl F. (Inventor)

    1994-01-01

    A particulate reinforced NiAl-AlN composite alloy has a NiAl matrix and greater than about 13 volume percent fine particles of AlN within the matrix. The particles preferably have a diameter from about 15 nanometers to about 50 nanometers. The particulate reinforced NiAl-AlN composite alloy may be prepared by cryomilling prealloyed NiAl in liquid nitrogen using grinding media having a diameter of from about 2 to 6 mm at an impeller speed of from about 450 RPM to about 800 RPM. The cryomilling may be done for a duration of from about 4 hours to about 20 hours to obtain a cryomilled powder. The cryomilled powder may be consolidated to form the particulate reinforced NiAl-AlN composite alloy. The particulate reinforced alloy can further include a toughening alloy. The toughening alloy may include NiCrAlY, FeCrAlY, and FeAl.

  10. Elevated-Temperature Corrosion of CoCrCuFeNiAl0.5Bx High-Entropy Alloys in Simulated Syngas Containing H2S

    SciTech Connect

    Dogan, Omer N; Nielsen, Benjamin C; Hawk, Jeffrey A

    2013-08-01

    High-entropy alloys are formed by synthesizing five or more principal elements in equimolar or near equimolar concentrations. Microstructure of the CoCrCuFeNiAl{sub 0.5}B{sub x} (x = 0, 0.2, 0.6, 1) high-entropy alloys under investigation is composed of a mixture of disordered bcc and fcc phases and borides. These alloys were tested gravimetrically for their corrosion resistance in simulated syngas containing 0, 0.01, 0.1, and 1 % H{sub 2}S at 500 °C. The exposed coupons were characterized using XRD and SEM. No significant corrosion was detected at 500 °C in syngas containing 0 and 0.01 % H{sub 2}S while significant corrosion was observed in syngas containing 0.1 and 1 % H{sub 2}S. Cu{sub 1.96}S was the primary sulfide in the external corrosion scale on the low-boron high-entropy alloys, whereas FeCo{sub 4}Ni{sub 4}S{sub 8} on the high-boron high-entropy alloys. Multi-phase Cu-rich regions in the low-B high-entropy alloys were vulnerable to corrosive attack.

  11. Processing and Mechanical Properties of NiAl-Based In-Situ Composites. Ph.D. Thesis Final Report

    NASA Technical Reports Server (NTRS)

    Johnson, David Ray

    1994-01-01

    In-situ composites based on the NiAl-Cr eutectic system were successfully produced by containerless processing and evaluated. The NiAl-Cr alloys had a fibrous microstructure while the NiAl-(Cr,Mo) alloys containing 1 at. percent or more molybdenum exhibited a lamellar structure. The NiAl-28Cr-6Mo eutectic displays promising high temperature strength while still maintaining a reasonable room temperature fracture toughness when compared to other NiAl-based materials. The Laves phase NiAlTa was used to strengthen NiAl and very promising creep strengths were found for the directionally solidified NiAl-NiAlTa eutectic. The eutectic composition was found to be near NiAl-15.5Ta (at. percent) and well aligned microstructures were produced at this composition. An off-eutectic composition of NiAl-14.5Ta was also processed, consisting of NiAl dendrites surrounded by aligned eutectic regions. The room temperature toughness of these two phase alloys was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa. Polyphase in-situ composites were generated by directional solidification of ternary eutectics. The systems investigated were the Ni-Al-Ta-X (X=Cr, Mo, or V) alloys. Ternary eutectics were found in each of these systems and both the eutectic composition and temperature were determined. Of these ternary eutectics, the one in the NiAl-Ta-Cr system was found to be the most promising. The fracture toughness of the NiAl-(Cr,Al)NiTa-Cr eutectic was intermediate between those of the NiAl-NiAlTa eutectic and the NiAl-Cr eutectic. The creep strength of this ternary eutectic was similar to or greater than that of the NiAl-Cr eutectic.

  12. Effect of cold rolling on the microstructure and mechanical properties of Al0.25CoCrFe1.25Ni1.25 high-entropy alloy

    SciTech Connect

    Wang, Z.; Gao, M. C.; Ma, S. G.; Yang, H. J.; Wang, Z. H.; Ziomek-Moroz, M.; Qiao, J. W.

    2015-08-05

    Cold rolling can break down the as-cast dendrite microstructure and thus may have pronounced impact on the mechanical behavior of the alloy. In the present study, the effect of cold rolling on the microstructure and mechanical properties of Al0.25CoCrFe1.25Ni1.25 high-entropy alloy in the face-centered cubic structure was investigated. With increasing the thickness reduction from cold rolling, the hardness, the yield strength, and the fracture strength increased at the cost of reducing ductility. At the thickness reduction of 80%, the tensile strength (hardness) was 702 MPa (406 MPa), 1.62 (2.43) times that in the as-cast condition. Compared to traditional alloys, Al0.25CoCrFe1.25Ni1.25 has the highest hardening rate with respect to CR thickness reduction. Lastly, the phase relation and the mixing properties of Gibbs free energy, enthalpy and entropy of AlxCoCrFe1.25Ni1.25 were predicted using the CALPHAD method.

  13. Oxidation resistant and low coefficient of thermal expansion NiA1-CoCrAly alloy

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G. (Inventor)

    2002-01-01

    A bond coat composition for use in thermal barrier coatings comprises a NiAl--CoCrAlY matrix containing particles of AlN dispersed therein. The bond coat composition is prepared by croymilling NiAl and CoCrAlY in liquid nitrogen.

  14. Dislocations and deformation microstructure in a B2-ordered Al28Co20Cr11Fe15Ni26 high-entropy alloy

    PubMed Central

    Feuerbacher, Michael

    2016-01-01

    High-entropy alloys are multicomponent metallic materials currently attracting high research interest. They display a unique combination of chemical disorder and crystalline long-range order, and due to their attractive properties are promising candidates for technological application. Many high-entropy alloys possess surprisingly high strength, occasionally in combination with high ductility and low density. The mechanisms effecting these attractive mechanical properties are not understood. This study addresses the deformation mechanism of a Al28Co20Cr11Fe15Ni26 high-entropy alloy, which is a two-phase material, consisting of a B2-ordered matrix and disordered body-centred inclusions. We quantitatively analyse the microstructure and dislocations in deformed samples by transmission-electron-microscopic methods including weak-beam imaging and convergent-beam electron diffraction. We find that the deformation process in the B2 phase is dominated by heterogeneous slip of screw dislocations gliding on planes. The dislocations are perfect superdislocations of the B2 lattice and show no dissociation. This indicates that the antiphase-boundary energy in the structure is very high, inhibiting spread of the dislocation core. Along with the observation of a widely extending strain field associated to the dislocations, our results provide a possible explanation for the high strength of this high-entropy alloy as a direct consequence of its dislocation structure. PMID:27430993

  15. Dislocations and deformation microstructure in a B2-ordered Al28Co20Cr11Fe15Ni26 high-entropy alloy.

    PubMed

    Feuerbacher, Michael

    2016-01-01

    High-entropy alloys are multicomponent metallic materials currently attracting high research interest. They display a unique combination of chemical disorder and crystalline long-range order, and due to their attractive properties are promising candidates for technological application. Many high-entropy alloys possess surprisingly high strength, occasionally in combination with high ductility and low density. The mechanisms effecting these attractive mechanical properties are not understood. This study addresses the deformation mechanism of a Al28Co20Cr11Fe15Ni26 high-entropy alloy, which is a two-phase material, consisting of a B2-ordered matrix and disordered body-centred inclusions. We quantitatively analyse the microstructure and dislocations in deformed samples by transmission-electron-microscopic methods including weak-beam imaging and convergent-beam electron diffraction. We find that the deformation process in the B2 phase is dominated by heterogeneous slip of screw dislocations gliding on planes. The dislocations are perfect superdislocations of the B2 lattice and show no dissociation. This indicates that the antiphase-boundary energy in the structure is very high, inhibiting spread of the dislocation core. Along with the observation of a widely extending strain field associated to the dislocations, our results provide a possible explanation for the high strength of this high-entropy alloy as a direct consequence of its dislocation structure. PMID:27430993

  16. Band alignment at the interface between Ni-doped Cr2O3 and Al-doped ZnO: implications for transparent p-n junctions

    NASA Astrophysics Data System (ADS)

    Arca, Elisabetta; McInerney, Michael A.; Shvets, Igor V.

    2016-06-01

    The realization of transparent electronic and optoelectronic devices requires the use of transparent p-n junctions. In this context, understanding the band alignment at the interface between the p- and n-components represents a fundamental step towards the realization of high performance devices. In this work, the band alignment at the interface between Al-doped ZnO (AZO) and Ni-doped Cr2O3 has been analysed. The formation and evolution of the core levels as the interface progressively forms have been followed by means of x-ray Photoelectron Spectroscopy, x-ray diffraction and x-ray reflectivity. A type two (staggered) band alignment was identified, with the valence band offset and conduction band offset found to be 2.6 eV and 2.5 eV, respectively. The electrical behaviour will be discussed in terms of the position of the bands, the presence of band bending and the expected built-in potential and how these can be engineered in order to achieve the maximum performance for this hetero-structure.

  17. The Influence of Temperature on Frictional Behavior of Plasma-Sprayed NiAl-Cr2O3 Based Self-Adaptive Nanocomposite Coatings

    NASA Astrophysics Data System (ADS)

    Ramazani, M.; Ashrafizadeh, F.; Mozaffarinia, R.

    2013-10-01

    Frictional behavior of nano and hybrid-structured NiAl-Cr2O3-Ag-CNT-WS2 adaptive self-lubricant coatings was evaluated at a range of temperatures, from room temperature to 700 °C. For this purpose, hybrid structured (HS) and nanostructured (NS) composite powders with the same nominal compositions were prepared by spray drying and heat treatment techniques. A series of HS and NS coating samples were deposited on steel substrate by an atmospheric plasma spraying process. The tribological behavior of both coatings was studied from room temperature to 700 °C at 100° intervals using a custom designed high temperature wear test machine. Scanning electron microscopy was employed for the evaluation of the composite coatings and worn surfaces. Experimental results indicated that the hybrid coating had inferior tribological properties when compared to the nanostructured coating, showing the attractive frictional behavior on the basis of low friction and high wear resistance; the NS coating possessed a more stable friction coefficient in the temperature range of 25-700 °C against alumina counterface. Microstructural examinations revealed more uniformity in NS plasma-sprayed coatings.

  18. Dislocations and deformation microstructure in a B2-ordered Al28Co20Cr11Fe15Ni26 high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Feuerbacher, Michael

    2016-07-01

    High-entropy alloys are multicomponent metallic materials currently attracting high research interest. They display a unique combination of chemical disorder and crystalline long-range order, and due to their attractive properties are promising candidates for technological application. Many high-entropy alloys possess surprisingly high strength, occasionally in combination with high ductility and low density. The mechanisms effecting these attractive mechanical properties are not understood. This study addresses the deformation mechanism of a Al28Co20Cr11Fe15Ni26 high-entropy alloy, which is a two-phase material, consisting of a B2-ordered matrix and disordered body-centred inclusions. We quantitatively analyse the microstructure and dislocations in deformed samples by transmission-electron-microscopic methods including weak-beam imaging and convergent-beam electron diffraction. We find that the deformation process in the B2 phase is dominated by heterogeneous slip of screw dislocations gliding on planes. The dislocations are perfect superdislocations of the B2 lattice and show no dissociation. This indicates that the antiphase-boundary energy in the structure is very high, inhibiting spread of the dislocation core. Along with the observation of a widely extending strain field associated to the dislocations, our results provide a possible explanation for the high strength of this high-entropy alloy as a direct consequence of its dislocation structure.

  19. Band alignment at the interface between Ni-doped Cr2O3 and Al-doped ZnO: implications for transparent p-n junctions.

    PubMed

    Arca, Elisabetta; McInerney, Michael A; Shvets, Igor V

    2016-06-01

    The realization of transparent electronic and optoelectronic devices requires the use of transparent p-n junctions. In this context, understanding the band alignment at the interface between the p- and n-components represents a fundamental step towards the realization of high performance devices. In this work, the band alignment at the interface between Al-doped ZnO (AZO) and Ni-doped Cr2O3 has been analysed. The formation and evolution of the core levels as the interface progressively forms have been followed by means of x-ray Photoelectron Spectroscopy, x-ray diffraction and x-ray reflectivity. A type two (staggered) band alignment was identified, with the valence band offset and conduction band offset found to be 2.6 eV and 2.5 eV, respectively. The electrical behaviour will be discussed in terms of the position of the bands, the presence of band bending and the expected built-in potential and how these can be engineered in order to achieve the maximum performance for this hetero-structure. PMID:26952763

  20. Effect of cold rolling on the microstructure and mechanical properties of Al0.25CoCrFe1.25Ni1.25 high-entropy alloy

    DOE PAGESBeta

    Wang, Z.; Gao, M. C.; Ma, S. G.; Yang, H. J.; Wang, Z. H.; Ziomek-Moroz, M.; Qiao, J. W.

    2015-08-05

    Cold rolling can break down the as-cast dendrite microstructure and thus may have pronounced impact on the mechanical behavior of the alloy. In the present study, the effect of cold rolling on the microstructure and mechanical properties of Al0.25CoCrFe1.25Ni1.25 high-entropy alloy in the face-centered cubic structure was investigated. With increasing the thickness reduction from cold rolling, the hardness, the yield strength, and the fracture strength increased at the cost of reducing ductility. At the thickness reduction of 80%, the tensile strength (hardness) was 702 MPa (406 MPa), 1.62 (2.43) times that in the as-cast condition. Compared to traditional alloys, Al0.25CoCrFe1.25Ni1.25more » has the highest hardening rate with respect to CR thickness reduction. Lastly, the phase relation and the mixing properties of Gibbs free energy, enthalpy and entropy of AlxCoCrFe1.25Ni1.25 were predicted using the CALPHAD method.« less

  1. Influence of W, Mo and Ti trace elements on the phase separation in Al8Co17Cr17Cu8Fe17Ni33 based high entropy alloy.

    PubMed

    Manzoni, Anna M; Daoud, Haneen M; Voelkl, Rainer; Glatzel, Uwe; Wanderka, Nelia

    2015-12-01

    Compositionally complex alloys, also called high entropy alloys, have been investigated for over a decade in view of different applications, but so far only a small number of alloys can be considered as presenting good enough properties for industrial application. The most common family of elements is Al-Co-Cr-Cu-Fe-Ni. The equiatomic alloy having 5 phases and being too brittle, the composition has been modified in order to improve the mechanical properties. Different compositions have been tested and as a first result ductile Al8Co17Cr17Cu8Fe17Ni33 has been chosen for deeper investigation. It shows a dendritic segregation into Co-Cr-Fe rich cores and Al-Cu-Ni rich interdendritic sites. The as-cast state is characterized mainly by two phases, namely Al-Cu-Ni rich precipitates of L12 structure inside a solid solution matrix. After homogenization both alloys consists of a single solid solution phase. Results are compared to calculations by ThermoCalc. In order to further improve the properties of the alloy the Cr content has been decreased and replaced by trace elements W, Mo and Ti, which, according to ThermoCalc, increase the melting point and the phase transition temperature which leads to the formation of the L12 phase. As-cast and heat treated samples of the base and the modified alloy have been investigated by transmission electron microscopy and three dimensional atom probe. Results of the investigations will be discussed in terms of microstructure, hardness and coherence with Thermo Calc predictions. PMID:26159736

  2. Corrosion performance of bi-layer Ni/Cr2C3-NiCr HVAF thermal spray coating

    NASA Astrophysics Data System (ADS)

    Sadeghimeresht, E.; Markocsan, N.; Nylén, P.; Björklund, S.

    2016-04-01

    The corrosion behavior of three HVAF thermal spray coating systems (A: single-layer Ni, B: single-layer Cr2C3-NiCr coatings, and C: bi-layer Ni/Cr2C3-NiCr coating) was comparatively studied using immersion, salt spray, and electrochemical tests. Polarization and EIS results showed that the corrosion behavior of Cr2C3-NiCr coatings in 3.5 wt.% NaCl solution was significantly improved by adding the intermediate layer of Ni. It was illustrated that the polarization resistance of the bi-layer Ni/Cr2C3-NiCr and single-layer Cr2C3-NiCr coatings were around 194 and 38 kΩ cm2, respectively. Microstructure analysis revealed that the bond coating successfully prevented the corrosion propagation toward the coating.

  3. The 1200 C cyclic oxidation behavior of two nickel-aluminum alloys (Ni3AL and NiAl) with additions of chromium, silicon, and titanium

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    The alloys Ni3Al and NiAl with and without 1 and 3 atomic percent chromium, silicon, and titanium replacing the aluminum were cyclically oxidized at 1200 C for times to 200 hours, and the results were compared with those obtained with the alloy B-1900 subjected to the same oxidation process. The evaluation was based on metal recession, specific weight change, metallography, electron microprobe analysis, and X-ray diffraction. The oxidation resistance of Ni3Al was improved by Si, unaffected by Ti, and degraded by Cr. The oxidation resistance of NiAl was slightly improved by Ti, unaffected by Si, and degraded by Cr. The oxidation resistance of Ni3Al with 1 atomic percent Si was nearly equal to that of NiAl. Alloy B-1900 exhibited oxidation resistance comparable to that of Ni3Al + Cr compositions.

  4. The erosion-oxidation behavior of HVOF Cr{sub 3}C{sub 2}-NiCr cermet coating

    SciTech Connect

    Wang, B.Q.; Luer, K.

    1994-12-31

    DenSys DS-200 coating is a proprietary HVOF Cr{sub 3}C{sub 2}-NiCr cermet coating used in elevated temperature service environments including fluidized bed boilers, coal-fired boilers and municipal waste incinerators. The elevated temperature erosion-corrosion (oxidation) behavior of this HVOF Cr{sub 3}C{sub 2}-NiCr coating was investigated using a range of test temperatures, impact angles, erodents, and particle velocities. The erosion-corrosion behavior of HVOF Cr{sub 3}C{sub 2}-NiCr coatings was compared with 1018 steel and other thermal-spray coatings including FeCrSiB (Armacor M), Ni-base, Cr{sub 2}O{sub 3}-6SiO{sub 2}-4Al{sub 2}O{sub 3} (Rokide C), Cr{sub 2}O{sub 3}-12SiO{sub 2}-2Al{sub 2}O{sub 3}-4MgO (Rokide MBC), and WC-NiCrCo (SMI 712). It was found that the erosion-oxidation resistance of HVOF Cr{sub 3}C{sub 2}-NiCr coating was higher than 1018 steel and other coatings at both impact angles 30{degree} and 90{degree}. The erosion-oxidation behavior of coatings was well related to their morphology. The high erosion-oxidation resistance of the HVOF Cr{sub 3}C{sub 2}-NiCr coating was attributed to its low porosity, fine grain structure and homogeneous distribution of hard carbides/oxides which form a skeletal network within a ductile and corrosion-resistant metal binder.

  5. Film Thickness Influences on the Thermoelectric Properties of NiCr/NiSi Thin Film Thermocouples

    NASA Astrophysics Data System (ADS)

    Chen, Y. Z.; Jiang, H. C.; Zhang, W. L.; Liu, X. Z.; Jiang, S. W.

    2013-06-01

    NiCr/NiSi thin film thermocouples (TFTCs) with a multi-layer structure were fabricated on Ni-based superalloy substrates (95 mm × 35 mm × 2 mm) by magnetron sputtering and electron beam evaporation. The five-layer structure is composed of NiCrAlY buffer layer (2 μm), thermally grown Al2O3 bond layer (200 nm), Al2O3 insulating layer (10 μm), NiCr/NiSi TFTCs (1 μm), and Al2O3 protective layer (500 nm). Influences of thermocouple layer thickness on thermoelectric properties were investigated. Seebeck coefficient of the samples with the increase in thermocouple layer thickness from 0.5 μm to 1 μm increased from 27.8 μV/°C to 33.8 μV/°C, but exhibited almost no change with further increase in thermocouple layer thickness from 1 μm to 2 μm. Dependence on temperature of the thermal electromotive force of the samples almost followed standard thermocouple characteristic curves when the thickness of the thermocouple layer was 1 μm and 2 μm. Sensitive coefficient K of the samples increased greatly with the increase in thickness of the thermocouple layer from 0.5 μm to 1 μm, but decreased insignificantly with the increase in thermocouple layer thickness from 1 μm to 2 μm, and continuously decreased with the increase in temperature. The sensitive coefficient and the stability of NiCr/NiSi TFTCs were both improved after annealing at 600°C.

  6. The oxidation of Ni-rich Ni-Al intermetallics

    NASA Technical Reports Server (NTRS)

    Doychak, J.; Smialek, J. L.; Barrett, C. A.

    1989-01-01

    The oxidation of Ni-Al intermetallic alloys in the beta-NiAl phase field and in the two phase beta-NiAl/gamma'-Ni3Al phase field has been studied between 1000 and 1400 C. The stoichiometric beta-NiAl alloy doped with Zr was superior to other alloy compositions under cyclic and isothermal oxidation. The isothermal growth rates did not increase monotonically as the alloy Al content was decreased. The characteristically ridged alpha-Al203 scale morphology, consisting of cells of thin, textured oxide with thick growth ridges at cell boundaries, forms on oxidized beta-NiAl alloys. The correlation of scale features with isothermal growth rates indicates a predominant grain boundary diffusion growth mechanism. The 1200 C cyclic oxidation resistance decreases near the lower end of the beta-NiAl phase field.

  7. The oxidation of Ni-rich Ni-Al intermetallics

    NASA Technical Reports Server (NTRS)

    Doychak, Joseph; Smialek, James L.; Barrett, Charles A.

    1988-01-01

    The oxidation of Ni-Al intermetallic alloys in the beta-NiAl phase field and in the two phase beta-NiAl/gamma'-Ni3Al phase field has been studied between 1000 and 1400 C. The stoichiometric beta-NiAl alloy doped with Zr was superior to other alloy compositions under cyclic and isothermal oxidation. The isothermal growth rates did not increase monotonically as the alloy Al content was decreased. The characteristically ridged alpha-Al2O3 scale morphology, consisting of cells of thin, textured oxide with thick growth ridges at cell boundaries, forms on oxidized beta-NiAl alloys. The correlation of scale features with isothermal growth rates indicates a predominant grain boundary diffusion growth mechanism. The 1200 C cyclic oxidation resistance decreases near the lower end of the beta-NiAl phase field.

  8. Electrochemical and corrosion properties of YNi{sub 2.5}M{sub 0.5} (M = Ni, Al, Fe, Cr, Cu, Co, Mn) hybride-forming alloys

    SciTech Connect

    Korobov, I.I.; Vasina, S.Ya.; Petrii, O.A.

    1995-06-01

    Hydrogen sorption by electrode materials based on YNi{sub 2.5}M{sub 0.5} (M = Ni, Al, Fe, Cr, Co, Cu, Mn) intermetallic compounds (IMC) with Cu and PTFE binders is studied in 1 M NaOH solution. The obtained reversible electrochemical capacities correspond to YNi{sub 2.5}M{sub 0.5}H{sub 1.3-1.7} hybrides which are stable at room temperature and atmospheric pressure. The application of Cu binder allows one to more completely use the material sorption capacity and promotes both extraction and sorption of hydrogen by IMC.

  9. Fabrication of CuAl{sub 1−x}M{sub x}O{sub 2} (M = Fe, Cr)/Ni film delafossite compounds using spin coating and their microstructure and dielectric constant

    SciTech Connect

    Diantoro, Markus Yuwita, Pelangi Eka Olenka, Desyana Nasikhudin

    2014-09-25

    The discovery of delafossite compound has encouraged more rapid technological developments particularly in transparent electronic devices. Copper oxide-based transparent thin films delafossite semiconductor recently give much attention in the field of optoelectronic technology, after the discovery of p-type CuAlO{sub 2}. The potential applications of a p-type semiconductor transparent conductive oxides (TCO) have been applied in broad field of optoelectronics. To explore a broad physical properties interms of magnetic conducting subtitution is understudied. In this work we report the fabrication of delafossite film on Ni substrate and their characterization of CuAl{sub 1−x}M{sub x}O{sub 2} delafossite compounds doped with Cr{sup 3+} and Fe{sup 3+} from the raw material of Cu(NO{sub 3}){sub 2}@@‡3H{sub 2}O, Al(NO{sub 3}){sub 3}@@‡9H{sub 2}O, Fe(NO{sub 3}){sub 3}@@‡9H{sub 2}O and Cr(NO{sub 3}){sub 3}@@‡9H{sub 2}O. The films were prepared using spin coating through a sol-gel technique at various concentrations of x = 0, 0.03, 0.04, and 0.05 for chromium and x = 0, 0.02, 0.04, 0.06, and 0.08 for iron doped. Crystal and microstructure were characterized by means of Cu-Kα Bragg-Brentano X-RD followed by High Score Plus and SEM-EDAX. The dielectric constants of the films were characterized using LCR meter. It was found that the CuAl{sub 1−x}M{sub x}O{sub 2}/Ni delafossite films were successfully fabricated. The CuAl{sub 1−x}Fe{sub x}O{sub 2} compound crystallized with lattice parameters of a = b ranged from 2.8603 Å to 2.8675 Å and c ranged from 16.9576 to 17.0763 Å. The increase of the dopant give rise to the increase of the lattice parameters. Since iron has bigger ionic radius (69 pm) than original site of Al{sup 3+} with radius of 53 pm the crystal volume lattice also increase. Further analyses of increasing volume of the crystal, as expected, affected to the decreasing of its dielectric constant. The similar trends also shown by Cr{sup 3+} doped of

  10. Precipitation in 9Ni-12Cr-2Cu maraging steels

    SciTech Connect

    Stiller, K.; Haettestrand, M.; Danoix, F.

    1998-11-02

    Two maraging steels with the compositions 9Ni-12Cr-2Cu-4Mo (wt%) and 9Ni-12Cr-2Cu and with small additions of Al and Ti were investigated using atom probe field ion microscopy. Tomographic atom probe investigations were performed to clarify the spatial distribution of elements in and close to the precipitates. Materials heat treated at 475 C for 5, 25 min, 1, 2, 4 and 400 h were analyzed. Precipitates in the Mo-rich material were observed already after 5 min of aging, while in the material without MO, precipitation started later. In both materials precipitation begins with the formation of Cu-rich particles which work as nucleation sites for a Ni-rich phase of type Ni{sub 3}(Ti,Al). A Mo-rich phase was detected in the Mo-rich steel after 2 h of aging. The distribution of alloying elements in the precipitates, their role in the precipitation process, and the mechanism of hardening in the two materials are discussed.

  11. The Effects of Composition and gamma'/gamma Lattice Parameter Mismatch on the Critical Resolved Shear Stresses for Octahedral and Cube Slip in NiAlCrX Alloys

    NASA Technical Reports Server (NTRS)

    Miner, R. V.

    1997-01-01

    Prototypical single-crystal NiAlCrX superalloys were studied to examine the effects of the common major alloying elements, Co, Mo, Nb, Ta, Ti, and W, on yielding behavior. The alloys contained about 10 at. pct Cr, 60 vol pct of the gamma' phase, and about 3 at. pct of X in the gamma'. The critical resolved shear stresses (CRSSs) for octahedral and primary cube slip were measured at 760 C, which is about the peak strength temperature. The CRSS(sub oct) and CRSS(sub cube) are discussed in relation to those of Ni, (Al, X) gamma' alloys taken from the literature and the gamma'/gamma lattice mismatch. The CRSS(sub oct) of the gamma + gamma' alloys reflected a similar compositional dependence to that of both the CRSS(sub cube) of the gamma' phase and the gamma'/gamma lattice parameter mismatch. The CRSS(sub cube) of the gamma + gamma' alloys also reflected the compositional dependence of the gamma'/gamma mismatch, but bore no similarity to that of CRSS(sub cube) for gamma' alloys since it is controlled by the gamma matrix. The ratio of CRSS(sub cube)/CRSS(sub oct) was decreased by all alloying elements except Co, which increased the ratio. The decrease in CRSS(sub cube)/CRSS(sub oct) was related to the degree in which elements partition to the gamma' rather than the gamma phase.

  12. Enhanced diffusion welding of TD-NiCr sheet.

    NASA Technical Reports Server (NTRS)

    Holko, K. H.; Moore, T. J.

    1972-01-01

    A method termed 'enhanced diffusion welding' has been developed to produce solid-state welds in TD-NiCr (Ni-20Cr-2ThO2) alloy sheet with weld strengths of 100% of the parent metal strength. Diffusion welded joints were made in specially processed TD-NiCr that equaled the tensile-shear and creep-rupture shear strengths of the parent material at 1090 deg C. The following observations have been made: specially processed TD-NiCr is preferred over commercial TD-NiCr for diffusion welding; the weld line can be eliminated when joining specially processed TD-NiCr by 600-grit sanding and electropolishing the faying surfaces prior to welding; and, a two-step weld cycle is preferred for diffusion welding of this alloy.

  13. Temperature Dependent Electrical Transport Properties of Ni-Cr and Co-Cr Binary Alloys

    NASA Astrophysics Data System (ADS)

    Thakore, B. Y.; Suthar, P. H.; Khambholja, S. G.; Gajjar, P. N.; Bhatt, N. K.; Jani, A. R.

    2011-12-01

    The temperature dependent electrical transport properties viz. electrical resistivity and thermal conductivity of Ni10Cr90 and Co20Cr80 alloys are computed at various temperatures. The electrical resistivity has been calculated according to Faber-Ziman model combined with Ashcroft-Langreth partial structure factors. In the present work, to include the ion-electron interaction, we have used a well tested local model potential. For exchange-correlation effects, five different forms of local field correction functions due to Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Farid et al (F) and Sarkar et al (S) are used. The present results due to S function are in good agreement with the experimental data as compared to results obtained using other four functions. The S functions satisfy compressibility sum rule in long wave length limit more accurately as compared to T, IU and F functions, which may be responsible for better agreement of results, obtained using S function. Also, present result confirms the validity of present approach in determining the transport properties of alloys like Ni-Cr and Co-Cr.

  14. Temperature Dependent Electrical Transport Properties of Ni-Cr and Co-Cr Binary Alloys

    SciTech Connect

    Thakore, B. Y.; Khambholja, S. G.; Bhatt, N. K.; Jani, A. R.; Suthar, P. H.; Gajjar, P. N.

    2011-12-12

    The temperature dependent electrical transport properties viz. electrical resistivity and thermal conductivity of Ni{sub 10}Cr{sub 90} and Co{sub 20}Cr{sub 80} alloys are computed at various temperatures. The electrical resistivity has been calculated according to Faber-Ziman model combined with Ashcroft-Langreth partial structure factors. In the present work, to include the ion-electron interaction, we have used a well tested local model potential. For exchange-correlation effects, five different forms of local field correction functions due to Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Farid et al (F) and Sarkar et al (S) are used. The present results due to S function are in good agreement with the experimental data as compared to results obtained using other four functions. The S functions satisfy compressibility sum rule in long wave length limit more accurately as compared to T, IU and F functions, which may be responsible for better agreement of results, obtained using S function. Also, present result confirms the validity of present approach in determining the transport properties of alloys like Ni-Cr and Co-Cr.

  15. The effect of Cr, Co, Al, Mo and Ta on a series of cast Ni-base superalloys on the stability of an aluminide coating during cyclic oxidation in Mach 0.3 burner rig

    NASA Technical Reports Server (NTRS)

    Zaplatynsky, I.; Barrett, C. A.

    1986-01-01

    The influence of varying the content of Co, Cr, Mo, Ta, and Al in a series of cast Ni-based gamma/gamma'superalloys on the behavior of aluminide coatings was studied in burner rig cyclic oxidation tests at 1100 C. The alloys had nominally fixed levels of Ti, W, Cb, Zr, C, and B. The alloy compositions were based on a full 2(sup 5)-fractional statistical design supplemented by 10 star point alloys and a center point alloy. This full central composite design of 43 alloys plus two additional alloys with extreme Al levels allowed a complete second degree estimating equation to be derived from the 5-compositional variables. The weight change/time data for the coated samples fitted well to the paralinear oxidation model and enabled a modified oxidation attack parameter, K'(sub a) to be derived to rank the alloys and log K' (sub a ) to be used as the dependent variable in the estimating equation to determine the oxidation resistance of the coating as a function of the underlying alloy content. The most protective aluminide coatings are associated with the highest possible base ally contents of CR and Al and at a 4 percent Ta level. The Mo and Co effects interact but at fixed levels of 0, 5, or 10% Co. A 4% Mo level is optimum.

  16. Structure and physical properties of RT{sub 2}Cd{sub 20} (R=rare earth, T=Ni, Pd) compounds with the CeCr{sub 2}Al{sub 20}-type structure

    SciTech Connect

    Burnett, V.W.; Yazici, D.; White, B.D.; Dilley, N.R.; Friedman, A.J.; Brandom, B.; Maple, M.B.

    2014-07-01

    Eleven new compounds, R Ni{sub 2}Cd{sub 20} (R=Y, La–Nd, Sm, Gd, Tb) and R Pd{sub 2}Cd{sub 20} (R=Ce, Pr, Sm), were grown as single crystals in high temperature cadmium-rich solutions. They crystallize in the cubic CeCr{sub 2}Al{sub 20}-type structure (Fd3{sup ¯}m, Z=8) as characterized by measurements of powder X-ray diffraction. Electrical resistivity, magnetization, and specific heat measurements were performed on R Ni{sub 2}Cd{sub 20} (R=Y, La–Nd, Sm, Gd, Tb) single crystals. Whereas YNi{sub 2}Cd{sub 20} and LaNi{sub 2}Cd{sub 20} exhibit unremarkable metallic behavior, when magnetic moments from localized 4f electron states (Gd{sup 3+}–Tb{sup 3+}) are embedded into this host, they exhibit ferromagnetic order with values of the Curie temperature T{sub C} for R Ni{sub 2}Cd{sub 20} (R=Gd, and Tb) which scale with the de Gennes factor. - Graphical abstract: Specific heat divided by temperature C/T vs. T for single crystals of R Ni{sub 2}Cd{sub 20} (R=Y, La–Nd, Gd, and Tb). Left inset: Low temperature C/T vs. T{sup 2} for LaNi{sub 2}Cd{sub 20}. The solid line represents a linear fit of the data. Right inset: Low-temperature C/T data vs. T for R=Ce–Nd, Gd, and Tb; magnetic ordering temperatures are indicated by arrows. - Highlights: • R Ni{sub 2}Cd{sub 20} (R=Y, La–Nd, Sm, Gd, Tb) single crystals synthesized for the first time. • R Pd{sub 2}Cd{sub 20} (R=Ce, Pr, Sm) single crystals synthesized for the first time. • Single crystals are of good metallurgical quality (large RRR values). • NdNi{sub 2}Cd{sub 20} orders antiferromagnetically at T{sub N}=1.5 K. • R Ni{sub 2}Cd{sub 20} (R=Sm, Gd, Tb) order ferromagnetically.

  17. Transient oxidation of multiphase Ni-Cr base alloys

    SciTech Connect

    Baran, G.; Meraner, M.; Farrell, P.

    1988-06-01

    Four commercially available Ni-Cr-based alloys used with porcelain enamels were studied. Major alloying elements were Al, Be, Si, B, Nb, and Mo. All alloys were multiphase. During heat treatments simulating enameling conditions, phase changes occurred in most alloys and were detected using hardness testing, differential thermal analysis (DTA), and microscopy. Oxidation of these alloys at 1000/degrees/C for 10 min produced an oxide layer consisting principally of chromium oxide, but the oxide morphology varied with each alloy depending on the alloy microstructure. Controlling alloy microstructure while keeping the overall composition unchanged may be a means of preventing wrinkled poorly adherent scales from forming.

  18. Chromium and Tantalum Site Substitution Patterns in Ni3Al (L1(sub 2))gamma(prime)- Precipitates

    NASA Technical Reports Server (NTRS)

    Booth-Morrison, Christopher; Mao, Zugang; Seidman, David N.; Noebe, Ronald D.

    2008-01-01

    The site substitution behavior of Cr and Ta in the Ni3Al (Ll2)-type gamma'-precipitates of a Ni-Al-Cr-Ta alloy is investigated by atom-probe tomography (APT) and first-principles calculations. Measurements of the gamma'-phase composition by APT suggest that Al, Cr, and Ta share the Al sublattice sites of the gamma'-precipitates. The calculated substitutional energies of the solute atoms at the Ni and Al sublattice sites indicate that Ta has a strong preference for the Al sites, while Cr has a weak Al site preference. Furthermore, Ta is shown to replace Cr at the Al sublattice sites of the gamma'-precipitates, altering the elemental phase partitioning behavior of the Ni-Al-Cr-Ta alloy.

  19. Diffusional creep and creep degradation in the dispersion-strengthened alloy TD-NiCr

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1972-01-01

    Dispersoid-free regions were observed in TD-NiCr (Ni-20Cr-2ThO2) after slow strain rate testing in air from 1145 to 1590 K. Formation of the dispersoid-free regions appears to be the result of diffusional creep. The net effect of this creep is the degradation of TD-NiCr to a duplex microstructure. Degradation is further enhanced by the formation of voids and integranular oxidation in the thoria-free regions. These regions apparently provided sites for void formation and oxide growth since the strength and oxidation resistance of Ni-20Cr is much less than Ni-20Cr-2ThO2. This localized oxidation does not appear to reduce the static load bearing capacity of TD-NiCr since long stress rupture lives were observed even with heavily oxidized microstructures. But this oxidation does significantly reduce the ductility and impact resistance of the material. Dispersoid-free bands and voids were also observed for two other dispersion strengthened alloys, TD-NiCrAl and IN-853. Thus, it appears that diffusional creep is charactertistic of dispersion-strengthened alloys and can play a major role in the creep degradation of these materials.

  20. Processing and Mechanical Properties of Directionally Solidified NiAl/NiAlTa Alloys

    NASA Technical Reports Server (NTRS)

    Johnson, D. R.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

    1994-01-01

    Promising creep strengths were found for a directionally solidified NiAl-NiAlTa alloy when compared to other NiAl based intermetallics. The directionally solidified alloy had an off-eutectic composition that resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The room temperature toughness of the two phase alloy was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa. Alloying additions that may improve the room temperature toughness by producing multiphase alloys are discussed.

  1. Interdiffusion behavior of Pt-modified γ-Ni + γ'-Ni3Al alloys coupled to Ni-Al-based alloys

    NASA Astrophysics Data System (ADS)

    Hayashi, Shigenari; Wang, Wen; Sordelet, Daniel J.; Gleeson, Brian

    2005-07-01

    The effect of platinum addition on the interdiffusion behavior of γ-Ni + γ'-Ni3Al alloys was studied by using diffusion couples comprised of a Ni-Al-Pt alloy mated to a Ni-Al, Ni-Al-Cr, or Ni-based commercial alloy. The commercial alloys studied were CMSX-4 and CMSX-10. Diffusion annealing was at 1150 °C for up to 100 hours. An Al-enriched γ'-layer often formed in the interdiffusion zone of a given couple during diffusion annealing due to the uphill diffusion of Al. This uphill diffusion was ascribed to Pt addition decreasing the chemical activity of aluminum in the γ + γ' alloys. For a given diffusion couple end member, the thickening kinetics of the γ' layer that formed increased with increasing Pt content in the Ni-Al-Pt γ + γ' alloy. The γ'-layer thickening kinetics in diffusion couples with Cr showed less of a dependence on Pt concentration. Inference of a negative effect of Pt and positive effect of Cr on the Al diffusion in this system enabled explanation of the observed interdiffusion behaviors. There was no or minimal formation of detrimental topologically close-packed (TCP) phases in the interdiffusion zone of the couples with CMSX-4 or CMSX-10. An overlay Pt-modified γ + γ' coating on CMSX-4 showed excellent oxidation resistance when exposed to air for 1000 hours at 1150 °C. Moreover, the Al content in the coating was maintained at a relatively high level due to Al replenishment from the CMSX-4 substrate.

  2. IR spectroscopic and thermal desorption studies of the interaction of the SO2 + O2 mixture with the 9% Ni-Cu-Cr/2% Ce/(θ + α)-Al2O3 catalyst

    NASA Astrophysics Data System (ADS)

    Dosumov, K.; Popova, N. M.; Umbetkaliev, A. K.; Brodskii, A. R.; Tungatarova, S. A.; Zheksenbaeva, Z. T.

    2012-10-01

    Data on the formation of surface structures during the adsorption of sulfur dioxide on alumina-supported metal and oxide catalysts in the presence of oxygen were reviewed. The results of our IR spectroscopic and thermal desorption studies of the interaction of the SO2+O2 mixture with the 9% Ni-Cu-Cr/2% Ce/(θ + α)-Al2O3 catalyst are presented. At 673 K chemisorption of SO2 takes place (absorption band 1165 cm-1, T {des/m} = 673 K), and SO2 is oxidized to form sulfate structures (absorption bands 1235, 1140, 1100, 985, and 615 cm-1, T {des/m} = 973 K), which decompose into SO2 and O2 at 973 K and decay when reduced in H2.

  3. Oxygen potentials in Ni + NiO and Ni + Cr[sub 2]O[sub 3] + NiCr[sub 2]O[sub 4] systems

    SciTech Connect

    Kale, G.M.; Fray, D.J. . Dept. of Mining and Mineral Engineering)

    1994-06-01

    The chemical potential of O for the coexistence of Ni + NiO and Ni + Cr[sub 2]O[sub 3] + NiCr[sub 2]O[sub 4] equilibria has been measured employing solid-state galvanic cells, (+) Pt, Cu + Cu[sub 2]O [vert bar][vert bar] (Y[sub 2]O[sub 3])ZrO[sub 2] [vert bar][vert bar] Ni + NiO, Pt (-) and (+) Pt, Ni + NiO [vert bar][vert bar] (Y[sub 2]O[sub 3])ZrO[sub 2] [vert bar][vert bar] Ni + Cr[sub 2]O[sub 3] + NiCr[sub 2]O[sub 4], Pt (-) in the temperature range of 800 to 1,300 K and 1,100 to 1,460 K, respectively. The electromotive force (emf) of both he cells was reversible, reproducible on thermal cycling, and varied linearly with temperature. for the coexistence of the two-phase mixture of Ni + NiO, [Delta][mu][sub O[sub 2

  4. Rapidly solidified NiAl and FeAl

    NASA Technical Reports Server (NTRS)

    Gaydosh, D. J.; Crimp, M. A.

    1984-01-01

    Melt spinning was used to produce rapidly solidified ribbons of the B2 intermetallics NiAl and FeAl. Both Fe-40Al and Fe-45Al possessed some bend ductility in the as spun condition. The bend ductility of Fe-40Al, Fe-45Al, and equiatomic NiAl increased with subsequent heat treatment. Heat treatment at approximately 0.85 T (sub m) resulted in significant grain growth in equiatomic FeAl and in all the NiAl compositions. Low bend ductility in both FeAl and NiAl generally coincided with intergranular failure, while increased bend ductility was characterized by increasing amounts of transgranular cleavage fracture.

  5. Heat-to-Heat Variation in Creep Life and Fundamental Creep Rupture Strength of 18Cr-8Ni, 18Cr-12Ni-Mo, 18Cr-10Ni-Ti, and 18Cr-12Ni-Nb Stainless Steels

    NASA Astrophysics Data System (ADS)

    Abe, Fujio

    2016-06-01

    Metallurgical factors causing the heat-to-heat variation in time to rupture have been investigated for 300 series stainless steels for boiler and heat exchanger seamless tubes, 18Cr-8Ni (JIS SUS 304HTB), 18Cr-12Ni-Mo (JIS SUS 316HTB), 18Cr-10Ni-Ti (JIS SUS321 HTB), and 18Cr-12Ni-Nb (JIS SUS 347HTB), at 873 K to 1023 K (600 °C to 750 °C) using creep rupture data for nine heats of the respective steels in the NIMS Creep Data Sheets. The maximum time to rupture was 222,705.3 hours. The heat-to-heat variation in time to rupture of the 304HTB and 316HTB becomes more significant with longer test durations at times above ~10,000 hours at 973 K (700 °C) and reaches to about an order of magnitude difference between the strongest and weakest heats at 100,000 hours, whereas that of the 321HTB and 347HTB is very large of about an order of magnitude difference from a short time of ~100 hours to long times exceeding 100,000 hours at 873 K to 973 K (600 °C to 700 °C). The heat-to-heat variation in time to rupture is mainly explained by the effect of impurities: Al and Ti for the 304HTB and 316HTB, which reduces the concentration of dissolved nitrogen available for the creep strength by the formation of AlN and TiN during creep, and boron for the 347HTB, which enhances fine distributions of M23C6 carbides along grain boundaries. The heat-to-heat variation in time to rupture of the 321HTB is caused by the heat-to-heat variation in grain size, which is inversely proportional to the concentration of Ti. The fundamental creep rupture strength not influenced by impurities is estimated for the steels. The 100,000 hours-fundamental creep rupture strength of the 347HTB steel is lower than that of 304HTB and 316HTB at 873 K and 923 K (600 °C and 650 °C) because the slope of stress vs time to rupture curves is steeper in the 347HTB than in the 304HTB and 316HTB. The 100,000 hours-fundamental creep rupture strength of the 321HTB exhibits large variation depending on grain size.

  6. Heat-to-Heat Variation in Creep Life and Fundamental Creep Rupture Strength of 18Cr-8Ni, 18Cr-12Ni-Mo, 18Cr-10Ni-Ti, and 18Cr-12Ni-Nb Stainless Steels

    NASA Astrophysics Data System (ADS)

    Abe, Fujio

    2016-09-01

    Metallurgical factors causing the heat-to-heat variation in time to rupture have been investigated for 300 series stainless steels for boiler and heat exchanger seamless tubes, 18Cr-8Ni (JIS SUS 304HTB), 18Cr-12Ni-Mo (JIS SUS 316HTB), 18Cr-10Ni-Ti (JIS SUS321 HTB), and 18Cr-12Ni-Nb (JIS SUS 347HTB), at 873 K to 1023 K (600 °C to 750 °C) using creep rupture data for nine heats of the respective steels in the NIMS Creep Data Sheets. The maximum time to rupture was 222,705.3 hours. The heat-to-heat variation in time to rupture of the 304HTB and 316HTB becomes more significant with longer test durations at times above ~10,000 hours at 973 K (700 °C) and reaches to about an order of magnitude difference between the strongest and weakest heats at 100,000 hours, whereas that of the 321HTB and 347HTB is very large of about an order of magnitude difference from a short time of ~100 hours to long times exceeding 100,000 hours at 873 K to 973 K (600 °C to 700 °C). The heat-to-heat variation in time to rupture is mainly explained by the effect of impurities: Al and Ti for the 304HTB and 316HTB, which reduces the concentration of dissolved nitrogen available for the creep strength by the formation of AlN and TiN during creep, and boron for the 347HTB, which enhances fine distributions of M23C6 carbides along grain boundaries. The heat-to-heat variation in time to rupture of the 321HTB is caused by the heat-to-heat variation in grain size, which is inversely proportional to the concentration of Ti. The fundamental creep rupture strength not influenced by impurities is estimated for the steels. The 100,000 hours-fundamental creep rupture strength of the 347HTB steel is lower than that of 304HTB and 316HTB at 873 K and 923 K (600 °C and 650 °C) because the slope of stress vs time to rupture curves is steeper in the 347HTB than in the 304HTB and 316HTB. The 100,000 hours-fundamental creep rupture strength of the 321HTB exhibits large variation depending on grain size.

  7. Effects of Cr and Ni on Interdiffusion and Reaction between U and Fe-Cr-Ni Alloys

    SciTech Connect

    K. Huang; Y. Park; L. Zhou; K.R. Coffey; Y.H. Sohn; B.H. Sencer; J. R. Kennedy

    2014-08-01

    Metallic U-alloy fuel cladded in steel has been examined for high temperature fast reactor technology wherein the fuel cladding chemical interaction is a challenge that requires a fundamental and quantitative understanding. In order to study the fundamental diffusional interactions between U with Fe and the alloying effect of Cr and Ni, solid-to-solid diffusion couples were assembled between pure U and Fe, Fe–15 wt.%Cr or Fe–15 wt.%Cr–15 wt.%Ni alloy, and annealed at high temperature ranging from 580 to 700 °C. The microstructures and concentration profiles that developed from the diffusion anneal were examined by scanning electron microscopy, and X-ray energy dispersive spectroscopy (XEDS), respectively. Thick U6Fe and thin UFe2 phases were observed to develop with solubilities: up to 2.5 at.% Ni in U6(Fe,Ni), up to 20 at.%Cr in U(Fe, Cr)2, and up to 7 at.%Cr and 14 at.% Ni in U(Fe, Cr, Ni)2. The interdiffusion and reactions in the U vs. Fe and U vs. Fe–Cr–Ni exhibited a similar temperature dependence, while the U vs. Fe–Cr diffusion couples, without the presence of Ni, yielded greater activation energy for the growth of intermetallic phases – lower growth rate at lower temperature but higher growth rate at higher temperature.

  8. Development of dispersion-strengthened Ni-Cr-ThOz alloys for the space shuttle thermal protection system

    NASA Technical Reports Server (NTRS)

    Blankenship, C. P.; Saunders, N. T.

    1972-01-01

    Manufacturing processes were developed for TD-NiCr providing small sheet (45 x 90 cm), and larger sheet (60 x 150 cm) and foil. The alternate alloy, DS-NiCr, was produced by pack-chromizing Ni-ThO2 sheet. Formability criteria are being established for basic sheet forming processes, which are brake forming, corrugation forming, joggling, dimpling, and beading. Resistance spot welding (fusion and solid state), resistance seam welding, solid state diffusion welding, and brazing are included in the joining programs. Major emphasis is centered on an Al-modified Ni-Cr-ThO2 alloy development. These alloys, containing 3 to 5% Al, form the protective Al2O3 scale. This enhances oxidation resistance under reentry conditions. Both TD-NiCrAl and DS-NiCrAl alloys are included. A tentative composition of Ni-16Cr-3.5Al-2ThO2 was selected based on oxidation resistance and fabricability.

  9. NiAl alloys for structural uses

    NASA Technical Reports Server (NTRS)

    Koss, D. A.

    1991-01-01

    Alloys based on the intermetallic compound NiAl are of technological interest as high temperature structural alloys. These alloys possess a relatively low density, high melting temperature, good thermal conductivity, and (usually) good oxidation resistance. However, NiAl and NiAl-base alloys suffer from poor fracture resistance at low temperatures as well as inadequate creep strength at elevated temperatures. This research program explored macroalloying additions to NiAl-base alloys in order to identify possible alloying and processing routes which promote both low temperature fracture toughness and high temperature strength. Initial results from the study examined the additions of Fe, Co, and Hf on the microstructure, deformation, and fracture resistance of NiAl-based alloys. Of significance were the observations that the presence of the gamma-prime phase, based on Ni3Al, could enhance the fracture resistance if the gamma-prime were present as a continuous grain boundary film or 'necklace'; and the Ni-35Al-20Fe alloy was ductile in ribbon form despite a microstructure consisting solely of the B2 beta phase based on NiAl. The ductility inherent in the Ni-35Al-20Fe alloy was explored further in subsequent studies. Those results confirm the presence of ductility in the Ni-35Al-20Fe alloy after rapid cooling from 750 - 1000 C. However exposure at 550 C caused embrittlement; this was associated with an age-hardening reaction caused by the formation of Fe-rich precipitates. In contrast, to the Ni-35Al-20Fe alloy, exploratory research indicated that compositions in the range of Ni-35Al-12Fe retain the ordered B2 structure of NiAl, are ductile, and do not age-harden or embrittle after thermal exposure. Thus, our recent efforts have focused on the behavior of the Ni-35Al-12Fe alloy. A second parallel effort initiated in this program was to use an alternate processing technique, mechanical alloying, to improve the properties of NiAl-alloys. Mechanical alloying in the

  10. Structural and magnetic properties of Cu Ni Cr spinel oxides

    NASA Astrophysics Data System (ADS)

    Tovar, M.; Torabi, R.; Welker, C.; Fleischer, F.

    2006-11-01

    The compounds CuCr 2O 4 and NiCr 2O 4 crystallize at room temperature in a tetragonal distorted spinel structure, s.g. I4 1/amd, with axes ratio c/ a<1 and >1, respectively. The distortion is caused by the Jahn-Teller ions Cu 2+ and Ni 2+ which flatten or elongate their surrounding oxygen tetrahedron. CuCr 2O 4 and NiCr 2O 4 form a complete solid solution series Cu 1-xNi xCr 2O 4 where for 0.825< x<0.875 members with orthorhombic symmetry were found. Using neutron powder diffraction and thermal analysis methods several members of the solid solution series were investigated. On cooling, all samples showed a temperature-dependent crystallographic phase transition from cubic to tetragonal symmetry between 865 K (CuCr 2O 4) and 310 K (NiCr 2O 4). The phase Cu 0.15Ni 0.85Cr 2O 4 undergoes a second crystallographic transition to orthorhombic symmetry, space group Fddd, at T=300 K. The neutron diffraction experiments as well as SQUID measurements reveal magnetic ordering of the ions between 150 and 50 K which partially occurs as a two-step mechanism.

  11. Al/sub 2/O/sub 3/ adherence on CoCrAl alloys

    SciTech Connect

    Kingsley, L.M.

    1980-04-01

    Adherence of protective oxides on NiCrAl and CoCrAl superalloys has been promoted by a dispersion of a highly oxygen reactive element or its oxide being produced within the protection system. Two aspects of this subject are investigated here: the use of Al/sub 2/O/sub 3/ as both the dispersion and protective oxide; and the production of an HfO/sub 2/ dispersion while simultaneously aluminizing the alloy. It was found that an Al/sub 2/O/sub 3/ dispersion will act to promote the adherence of an external scale of Al/sub 2/O/sub 3/ to a degree comparable to previously tested dispersions and an HfO/sub 2/ dispersion comparable to that produced by a Rhines pack treatment is produced during aluminization.

  12. NiCr etching in a reactive gas

    SciTech Connect

    Ritter, J.; Boucher, R.; Morgenroth, W.; Meyer, H. G.

    2007-05-15

    The authors have etched NiCr through a resist mask using Cl/Ar based chemistry in an electron cyclotron resonance etch system. The optimum gas mixture and etch parameters were found for various ratios of Ni to Cr, based on the etch rate, redeposits, and the etch ratio to the mask. The introduction of O{sub 2} into the chamber, which is often used in the etching of Cr, served to both increase and decrease the etch rate depending explicitly on the etching parameters. Etch rates of >50 nm min{sup -1} and ratios of >1 (NiCr:Mask) were achieved for NiCr (80:20). Pattern transfer from the mask into the NiCr was achieved with a high fidelity and without redeposits for a Cl/Ar mix of 10% Ar (90% Cl{sub 2}) at an etch rate of {approx_equal}50 nm min{sup -1} and a ratio of 0.42 (NiCr:ZEP 7000 e-beam mask)

  13. The influence of Cr and Al pack cementation on low carbon steel to improve oxidation resistance

    NASA Astrophysics Data System (ADS)

    Prasetya, Didik; Sugiarti, Eni; Destyorini, Fredina; Thosin, Kemas Ahmad Zaini

    2012-06-01

    Pack chromizing and aluminizing has been widely used for many years to improve hot temperature oxidation and corrosion resistance of metals. The coating process involves packing the steel in a powder mixture which contain aluminum and chromium source, and inert filler (usually alumina), and halide activator NH4Cl. Al and Cr were deposited onto carbon steel by pack cementation process using elemental Al and Cr powder as Al and Cr source, whereas NiCo alloys codeposited by electrodeposition. The position of Al and Cr could be under or over Ni-Co alloys deposited. Pack cementation was heated on dry inert gas at temperature 800 °C about 5 hours and 20 minute for Cr and Al respectively. Al and Cr was successfully deposited. Laying down effect of Al and Cr onto carbon steel whether up and down toward NiCo alloys coating have affected to oxidation resistance. The pack aluminizing as top layer given best resitance to restrain excessive oxide scale, in contrast pack chromizing reveal bad oxidation resistance, moreover occured spallation on layer.

  14. Cyclic creep and fatigue of TD-NiCr (thoria-dispersion-strengthened nickel-chromium), TD-Ni, and NiCr sheet at 1200 C

    NASA Technical Reports Server (NTRS)

    Hirschberg, M. H.; Spera, D. A.; Klima, S. J.

    1972-01-01

    The resistance of thin TD-NiCr sheet to cyclic deformation was compared with that of TD-Ni and a conventional nickel-chromium alloy. Strains were determined by a calibration technique which combines room-temperature strain gage and deflection measurements with high-temperature deflection measurements. Analyses of the cyclic tests using measured tensile and creep-rupture data indicated that the TD-NiCr and NiCr alloy specimens failed by a cyclic creep mechanism. The TD-Ni specimens, on the other hand, failed by a fatigue mechanism.

  15. Microstructure and Properties of HVOF-Sprayed Ni-50Cr Coatings

    SciTech Connect

    Joel A. Simpson; Terry C. Totemeier; Richard N. Wright

    2006-06-01

    Thermal spray coatings represent a potential cost-effective means of protecting structural components in advanced fossil energy systems. Previous work at the INL has focused on relationships between thermal spray processing conditions, structure, and properties in alumina- and silica-forming coatings, namely Fe3Al, FeAl, and Mo-Si-B alloys. This paper describes the preparation and characterization of chromia-forming Ni-50%Cr coatings, an alloy similar to the INCOCLAD 671 cladding, which has shown excellent performance in the Niles Plant service tests. The structure and properties of Ni-50Cr coatings are similar to other HVOF-sprayed metallic coatings: a typical lamellar microstructure is observed with essentially no porosity and little oxide. The microhardness and compressive residual stress both increase with increased spray particle velocity. Corrosion tests were performed on a variety of free-standing coatings (removed from the substrate, wrought Fe3Al alloy, and Grade 91 steel in a simulated coal combustion gas (N2-10%CO-5%CO2-2%H2O-0.12%H2S) and gas-slag environments (same gas, with iron sulfide powder in contact with the coating surface). The coatings tested included Fe3Al, FeAl, and Ni-50Cr alloys sprayed at different velocities. In these tests the iron aluminides in wrought and coating form showed the best performance, with Ni-50Cr coatings slightly worse; the Grade 91 steel was severely attacked.

  16. Ni{sub 3}Al aluminide alloys

    SciTech Connect

    Liu, C.T.

    1993-10-01

    This paper provides a brief review of the recent progress in research and development of Ni{sub 3}Al and its alloys. Emphasis has been placed on understanding low ductility and brittle fracture of Ni{sub 3}Al alloys at ambient and elevated temperatures. Recent studies have resulted in identifying both intrinsic and extrinsic factors governing the fracture behavior of Ni{sub 3}Al alloys. Parallel efforts on alloy design using physical metallurgy principles have led to properties for structural use. Industrial interest in these alloys is high, and examples of industrial involvement in processing and utilization of these alloys are briefly mentioned.

  17. Microhardness of Ni-Cr alloys under different casting conditions.

    PubMed

    Bauer, José Roberto de Oliveira; Loguercio, Alessandro Dourado; Reis, Alessandra; Rodrigues Filho, Leonardo Eloy

    2006-01-01

    This study evaluated the microhardness of Ni-Cr alloys used in fixed prosthodontics after casting under different conditions. The casting conditions were: (1-flame/air torch) flame made of a gas/oxygen mixture and centrifugal casting machine in a non-controlled casting environment; (2-induction/argon) electromagnetic induction in an environment controlled with argon; (3-induction/vacuum) electromagnetic induction in a vacuum environment; (4-induction/air) electromagnetic induction in a non-controlled casting environment. The 3 alloys used were Ni-Cr-Mo-Ti, Ni-Cr-Mo-Be, and Ni-Cr-Mo-Nb. Four castings with 5 cylindrical, 15 mm-long specimens (diameter: 1.6 mm) in each casting ring were prepared. After casting, the specimens were embedded in resin and polished for Vickers microhardness (VH) measurements in a Shimadzu HMV-2 (1,000 g for 10 s). A total of 5 indentations were done for each ring, one in each specimen. The data was subjected to two-way ANOVA and Tukey's multiple comparison tests (alpha = 0.05). The VH values of Ni-Cr-Mo-Ti (422 +/- 7.8) were statistically higher (p < 0.05) than those of Ni-Cr-Mo-Nb (415 +/- 7.6). The lowest VH values were found for Ni-Cr-Mo-Be (359 +/- 10.7). The VH values obtained in the conditions induction/argon and induction/vacuum were similar (p > 0.05) and lower than the values obtained in the conditions induction/air and flame/air torch (p < 0.05). The VH values in the conditions induction/air and flame/air were similar (p > 0.05). The microhardness of the alloys is influenced by their composition and casting method. The hardness of the Ni-Cr alloys was higher when they were cast with the induction/air and flame/air torch methods. PMID:16729173

  18. Local structure of NiAl compounds investigated by extended X-ray absorption fine-structure spectroscopy.

    PubMed

    Tian, J S; Han, G M; Wei, H; Jin, T; Dargusch, M S

    2012-07-01

    The local structures of pure NiAl and Ti-, Co-doped NiAl compounds have been obtained utilizing extended X-ray absorption fine-structure (EXAFS) spectroscopy. The results provide experimental evidence that Ni antisite defects exist in the Ni-rich NiAl compounds. The site preference of Ti and Co has been confirmed. Ti occupies the Al sublattice, while Co occupies the Ni sublattice. The structure parameters obtained by EXAFS were consistent with the X-ray diffraction results. Owing to the precipitation of α-Cr, the local structure of NiAl-Cr has not been obtained, making the site preference of Cr unclear. PMID:22713881

  19. Composite Ni/NiO-Cr2O3 Catalyst for Alkaline Hydrogen Evolution Reaction

    SciTech Connect

    Bates, MK; Jia, QY; Ramaswamy, N; Allen, RJ; Mukerjee, S

    2015-03-12

    We report a Ni-Cr/C electrocatalyst with unpreeedented massactivity for the hydrogen evolution reaction (HER). in alkaline electrolyte. The HER Oietics of numerous binary and ternary Ni-alloys and composite Ni/metal-euride/C samples were evaluated in aquebus 0.1 M KOH electrolyte. The highest HER mass-activity was observed for Ni-Cr materials which exhibit metallic Ni as well as NiOx and Cr2O3 phases as determined by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) analysis. The onset of the HER is significantly improved compared to munerous binary dor ternary Ni-alloys, inCluding Ni Mg materials. It is likely that at adjacent Ni/NiOx sites, the oxide acts as a sink for OHads, while the metallic Ni acts as a, sink for the H-ads, intermediate of the HER, thus minimizing the high activation energy of hydrogen evolution via water reduction. This is confirmed by in situ XAS studies that show that the synergistic HER enhancement is due to NiO content and that the Cr2O3 appears to stabilize the composite NiO component-under HER conditions (where NiOx would typically be reduced to metallic Ni-0). Furthermore, in contrast to Pt, the Ni(O-x)/Cr2O3 catalyst appears resistant to poisoning by the anion.exchange ionomer (AEI), a serloua consideration when applied to an anionic polymer electrolyte interface. Furthermore, we report a: detailed model of the double layer interface which helps explain the observed ensemble effect in the presence of AEI.

  20. Tribological properties of rare earth oxide added Cr 3C 2-NiCr coatings

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenyu; Lu, Xinchun; Luo, Jianbin

    2007-02-01

    A novel supersonic plasma spraying was used to prepare rare earth oxide added Cr 3C 2-NiCr coatings. X-ray diffractometer, contact surface profiler, hardness tester, micro-friction and -wear tester, environmental scanning electron microscope equipped with energy dispersive spectroscopy were employed to investigate the phase structure, surface morphology, microhardness, and friction properties of deposited coatings, respectively. The results show that surface roughness, microhardness, brittle fracture, friction extent and wear resistance of rare earth oxide added Cr 3C 2-NiCr coatings are effectively improved compared with that of unadded one. The friction and friction mechanism are also discussed.

  1. K-italic-shell ionization cross sections for Al, Ti, V, Cr, Fe, Ni, Cu, and Ag by protons and oxygen ions in the energy range 0. 3--6. 4 MeV

    SciTech Connect

    Geretschlaeger, M.; Benka, O.

    1986-08-01

    Absolute K-italic-shell ionization cross sections have been measured for thin targets of Al, Ti, and Cu for protons in the energy range 0.3--2.0 MeV and for thin targets of Ti, V, Cr, Fe, Ni, Cu, and Ag for oxygen ions in the energy range 1.36--6.4 Mev. The experimental results are compared to the perturbed-stationary-state (PSS) approximation with energy-loss (E), Coulomb (C), and relativistic (R) corrections, i.e., the ECPSSR approximation (Brandt and Lapicki), to the semiclassical approximation (Laegsgaard, Andersen, and Lund), and to a theory for direct Coulomb ionization of the 1s-italicsigma molecular orbital (Montenegro and Sigaud (MS)). The proton results agree within 3% with empirical reference cross sections. Also, the ECPSSR provides best overall agreement for protons. For oxygen ions, ECPSSR and MS predict experimental results satisfactorily for scaled velocities xi> or =0.4. For lower scaled velocities, the experimental cross sections become considerably higher than theoretical predictions for Coulomb ionization. This deviation increases with increasing Z-italic/sub 1//Z/sub 2/; it cannot be explained by electron transfer to the projectile or by ionization due to target recoil atoms.

  2. Microstructure of Ni-Al powder and Ni-Al composite coatings prepared by twin-wire arc spraying

    NASA Astrophysics Data System (ADS)

    Wang, Ji-xiao; Wang, Gui-xian; Liu, Jing-shun; Zhang, Lun-yong; Wang, Wei; Li, Ze; Wang, Qi-xiang; Sun, Jian-fei

    2016-07-01

    Ni-Al powder and Ni-Al composite coatings were fabricated by twin-wire arc spraying (TWAS). The microstructures of Ni-5wt%Al powder and Ni-20wt%Al powder were characterized by scanning electronic microscopy (SEM) and energy dispersive spectroscopy (EDS). The results showed that the obtained particle size ranged from 5 to 50 μm. The morphology of the Ni-Al powder showed that molten particles were composed of Ni solid solution, NiAl, Ni3Al, Al2O3, and NiO. The Ni-Al phase and a small amount of Al2O3 particles changed the composition of the coating. The microstructures of the twin-wire-arc-sprayed Ni-Al composite coatings were characterized by SEM, EDS, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results showed that the main phase of the Ni-5wt%Al coating consisted of Ni solid solution and NiAl in addition to a small amount of Al2O3. The main phase of the Ni-20wt%Al coating mainly consisted of Ni solid solution, NiAl, and Ni3Al in addition to a small amount of Al and Al2O3, and NiAl and Ni3Al intermetallic compounds effectively further improved the final wear property of the coatings. TEM analysis indicated that fine spherical NiAl3 precipitates and a Ni-Al-O amorphous phase formed in the matrix of the Ni solid solution in the original state.

  3. Mechanical and Tribological Properties of HVOF-Sprayed (Cr3C2-NiCr+Ni) Composite Coating on Ductile Cast Iron

    NASA Astrophysics Data System (ADS)

    Ksiazek, Marzanna; Boron, Lukasz; Radecka, Marta; Richert, Maria; Tchorz, Adam

    2016-06-01

    The aim of the investigations was to compare the microstructure, mechanical, and wear properties of Cr3C2-NiCr+Ni and Cr3C2-NiCr coatings deposited by HVOF technique (the high-velocity oxygen fuel spray process) on ductile cast iron. The effect of nickel particles added to the chromium carbide coating on mechanical and wear behavior in the system of Cr 3 C 2 -NiCr+Ni/ductile cast iron was analyzed in order to improve the lifetime of coated materials. The structure with particular emphasis of characteristic of the interface in the system of composite coating (Cr 3 C 2 -NiCr+Ni)/ductile cast iron was studied using the optical, scanning, and transmission electron microscopes, as well as the analysis of chemical and phase composition in microareas. Experimental results show that HVOF-sprayed Cr3C2-NiCr+Ni composite coating exhibits low porosity, high hardness, dense structure with large, partially molten Ni particles and very fine Cr3C2 and Cr7C3 particles embedded in NiCr alloy matrix, coming to the size of nanocrystalline. The results were discussed in reference to examination of bending strength considering cracking and delamination in the system of composite coating (Cr 3 C 2 -NiCr+Ni)/ductile cast iron as well as hardness and wear resistance of the coating. The composite structure of the coating provides the relatively good plasticity of the coating, which in turn has a positive effect on the adhesion of coating to the substrate and cohesion of the composite coating (Cr3C2-NiCr+Ni) in wear conditions.

  4. Mechanical and Tribological Properties of HVOF-Sprayed (Cr3C2-NiCr+Ni) Composite Coating on Ductile Cast Iron

    NASA Astrophysics Data System (ADS)

    Ksiazek, Marzanna; Boron, Lukasz; Radecka, Marta; Richert, Maria; Tchorz, Adam

    2016-07-01

    The aim of the investigations was to compare the microstructure, mechanical, and wear properties of Cr3C2-NiCr+Ni and Cr3C2-NiCr coatings deposited by HVOF technique (the high-velocity oxygen fuel spray process) on ductile cast iron. The effect of nickel particles added to the chromium carbide coating on mechanical and wear behavior in the system of Cr 3 C 2 -NiCr+Ni/ductile cast iron was analyzed in order to improve the lifetime of coated materials. The structure with particular emphasis of characteristic of the interface in the system of composite coating (Cr 3 C 2 -NiCr+Ni)/ductile cast iron was studied using the optical, scanning, and transmission electron microscopes, as well as the analysis of chemical and phase composition in microareas. Experimental results show that HVOF-sprayed Cr3C2-NiCr+Ni composite coating exhibits low porosity, high hardness, dense structure with large, partially molten Ni particles and very fine Cr3C2 and Cr7C3 particles embedded in NiCr alloy matrix, coming to the size of nanocrystalline. The results were discussed in reference to examination of bending strength considering cracking and delamination in the system of composite coating (Cr 3 C 2 -NiCr+Ni)/ductile cast iron as well as hardness and wear resistance of the coating. The composite structure of the coating provides the relatively good plasticity of the coating, which in turn has a positive effect on the adhesion of coating to the substrate and cohesion of the composite coating (Cr3C2-NiCr+Ni) in wear conditions.

  5. Measured Activities of Al and Ni in gamma-(Ni) and gamma'-(Ni)3Al in the Ni-Al-Pt System

    NASA Technical Reports Server (NTRS)

    Copland, Evan

    2007-01-01

    Adding Pt to Ni-Al coatings is critical to achieving the required oxidation protection of Ni-based superalloys, but the nature of the Pt effect remains unresolved. This research provides a fundamental part of the answer by measuring the influence of Pt on the activities of Al and Ni in gamma-(Ni), gamma prime-(Ni)3Al and liquid in the Ni-Al-Pt system. Measurements have been made at 25 compositions in the Ni-rich corner over the temperature range, T = 1400-1750 K, by the vapor pressure technique with a multiple effusion-cell mass spectrometer (multi-cell KEMS). These measurements clearly show adding Pt (for X(sub Pt) less than 0.25) decreases a(Al) while increasing a(Ni). This solution behavior supports the idea that Pt increases Al transport to an alloy / Al2O3 interface and also limits the interaction between the coating and substrate alloys in the gamma-(Ni) + gamma prime-(Ni)3Al region. This presentation will review the progress of this study.

  6. High-temperature nitridation of Ni-Cr alloys

    NASA Astrophysics Data System (ADS)

    Kodentsov, A. A.; Gülpen, J. H.; Cserháti, C.; Kivilahti, J. K.; van Loo, F. J. J.

    1996-01-01

    The nitriding behavior of nickel-chromium alloys was investigated at 1398 K over the range 1 to 6000 bar of external nitrogen pressure. The morphology of the nitrided zone depends on the concentration of chromium in the initial alloy and the N2 pressure (fugacity) applied upon the system. The transition from CrN to Cr2N precipitation was observed within the reaction zone after nitriding at 100 to 6000 bar of N2 when the chromium content in the initial alloys was 28.0 at. pct or higher. It is shown that the ternary phase π (Cr10Ni7N3) is formed in this system at 1273 K. through a peritectoid reaction between Cr2N and nickel solid solution and becomes unstable above 1373 K. The thermodynamic evaluation of the Ni-Cr-N system was performed and phase equilibria calculated. Evidence for “up hill” diffusion of nitrogen near the reaction front during the internal nitridation of Ni-Cr alloys at 1398 K was found. It was attributed to the relative instability of chromium nitrides and strong Cr-N interaction in the matrix of the Ni-based solid solution within the nitrided zone.

  7. Uptake of Al, As, Cr, Cd, Cu, Fe, Mn, Ni, Pb, Sr, and Zn in native wheatgrasses, wildryes, and bluegrass on three metal-contaminated soils from Montana

    Technology Transfer Automated Retrieval System (TEKTRAN)

    One of the biggest challenges to successfully phytoremediate contaminated mineland soils is the identification of native plants that possess a broad adaptation to ecological sites and either exclude or uptake heavy metals of interest. This study evaluated forage concentrations of aluminum (Al), ars...

  8. The new structure type Gd3Ni7Al14.

    PubMed

    Pukas, Svitlana; Gladyshevskii, Roman

    2015-11-01

    The crystal structure of Gd3Ni7Al14 (trigadolinium heptanickel tetradecaaluminide) belongs to a family of two-layer structures and can be described as an assembly of interpenetrating centred straight prisms. For the Ni atoms, trigonal prisms (Al4Gd2 and Al6) are observed, the Al atoms are inside tetragonal (Ni2Al2Gd4, Ni2Al4Gd2, Al4Gd4, Ni4Al4 and Al8) and pentagonal (Ni4Al6 and Al10) prisms, while the Gd atoms are at the centres of pentagonal (Ni4Al6) and hexagonal (Ni4Al8) prisms. In each case, the true coordination polyhedron is a capped prism, also including atoms from the same layer. The structural features of Gd3Ni7Al14 are similar to those of the intermetallides PrNi2Al3 and ZrNiAl. In all these structures, Ni-centred trigonal prisms form infinite columns via common triangular faces. The columns share prism edges and form a three-dimensional framework with six-membered rings in the (001) plane in the case of the PrNi2Al3 and ZrNiAl types. In the case of Gd3Ni7Al14, six-membered rings are also observed, but only two-thirds of the rings are interconnected via prism edges. PMID:26524174

  9. Directional Solidification and Mechanical Properties of NiAl-NiAlTa Alloys

    NASA Technical Reports Server (NTRS)

    Johnson, D. R.; Chen, X. F.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

    1995-01-01

    Directional solidification of eutectic alloys is a promising technique for producing in-situ composite materials exhibiting a balance of properties. Consequently, the microstructure, creep strength and fracture toughness of directionally solidified NiAl-NiAlTa alloys were investigated. Directional solidification was performed by containerless processing techniques to minimize alloy contamination. The eutectic composition was found to be NiAl-15.5 at% Ta and well-aligned microstructures were produced at this composition. A near-eutectic alloy of NiAl-14.5Ta was also investigated. Directional solidification of the near-eutectic composition resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The off-eutectic alloy exhibited promising compressive creep strengths compared to other NiAl-based intermetallics, while preliminary testing indicated that the eutectic alloy was competitive with Ni-base single crystal superalloys. The room temperature toughness of these two-phase alloys was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa.

  10. Microstructure and Fracture Toughness of FeNiCr-TiC Composite Produced by Thermite Reaction

    NASA Astrophysics Data System (ADS)

    Xi, Wenjun; Shi, Chaoliang

    The microstructures of the FeNiCr-TiC composite produced by the rapid solidification thermite process were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The effects of aging treatment on the microstructure and fracture toughness of the composite were examined. Results showed that the FeNiCr-TiC composite was composed of ferrite (α-FeNiCr), TiC and NiAl (β phase). TiC particles in the matrix were in the shape of polygon and uniformly distributed, and their size was less than 3 µm. The β phase was coherent with the ferrite matrix, and its average size was about 50 nm. The fracture toughness of composite was 22 MPa·m1/2 without aging. When the aging temperature was below 600°C, the fracture toughness of the composite had higher plateau values and reached the maximum of 32 MPa·m1/2 at aging temperature 500°C due to the precipitation of NiAl phase on the nanometer scale. The fracture toughness decreased rapidly aged at 650°C, and then kept homology value in the range of 700 to 900°C, which was attributed to the precipitation of needle-shaped carbide (Cr/Fe)7C3 at the grain boundaries.

  11. Eutectic superalloys strengthened by sigma, Ni3CB lamellae and gamma prime, Ni3Al precipitates

    NASA Technical Reports Server (NTRS)

    Lemkey, F. D.

    1973-01-01

    By means of a screening and solidification optimization study of certain alloys located on the gamma-sigma liquidus surface within the Ni-Cb-Cr-Al system, alloys with high temperature properties superior to those of all known superalloys were defined. One alloy, Ni - 19.7w/o Cb - 6.0w/o Cr - 2.5w/o Al, directionally solidified at 3 cm/hr met or exceeded each program goal. A second alloy, Ni-21.75 w/o Cb-2.55 w/o Al, although deficient in its inherent oxidation resistance, met the other program goals and combined a remarkable insensitivity of composite microstructure to solidification parameters with excellent low temperature toughness. This investigation demonstrated that useful properties for gas turbine airfoil application have been achieved by reinforcing a strong and tough gamma solid solution matrix containing precipitated gamma prime by a lamellar intermetallic compound Ni3 Cb having greater strength at elevated temperature.

  12. Sputter-deposited metallic and ceramic coatings for heat engines. Work performed from October 1980 to September 1983. [CoCrAlY; ZrO/sub 2/; Al/sub 2/O/sub 3/; Ni-SiC; quartz-SiC

    SciTech Connect

    Prater, J.T.; Moss, R.W.

    1984-04-01

    Progress in the development of metallic and ceramic coatings with improved high-temperature corrosion and erosion/wear resistance is reported. The objective was to develop coatings that would insure that future heat engines, notably gas turbines and diesels, would be able to operate efficiently on degraded fuel supplies. The majority of coatings investigated were prepared by sputter deposition. Research on sputter-deposited CoCrAlY coatings was directed at improving their low-temperature, hot corrosion resistance by introducing composition gradients and adding platinum. Studies on sputter-deposited ZrO/sub 2/ and Al/sub 2/O/sub 3/ coatings were conducted to improve the thermal cycling resistance of ceramic deposits on metal substrates by using combinations of graded transition layers, columnar ceramic structures, and dense sealing layers. Preliminary results on plasma-sprayed Ni-SiC and quartz-SiC coatings that showed good wear and oxidation resistance are also reported.

  13. Modulus measurements in ordered Co-Al, Fe-Al, and Ni-Al alloys

    NASA Technical Reports Server (NTRS)

    Harmouche, M. R.; Wolfenden, A.

    1985-01-01

    The composition and/or temperature dependence of the dynamic Young's modulus for the ordered B2 Co-Al, Fe-Al, and Ni-Al aluminides has been investigated using the piezoelectric ultrasonic composite oscillator technique (PUCOT). The modulus has been measured in the composition interval 48.49 to 52.58 at. pct Co, 50.87 to 60.2 at. pct Fe, and 49.22 to 55.95 at. pct Ni for Co-Al, Fe-Al, and Ni-Al, respectively. The measured values for Co-Al are in the temperature interval 300 to 1300 K, while those for the other systems are for ambient temperature only. The data points show that Co-Al is stiffer than Fe-Al, which is stiffer than Ni-Al. The data points for Fe-Al and Ni-Al are slightly higher than those reported in the literature.

  14. Composite Ni/NiO-Cr2O3 Catalyst for Alkaline Hydrogen Evolution Reaction

    PubMed Central

    Bates, Michael K.; Jia, Qingying; Ramaswamy, Nagappan; Allen, Robert J.; Mukerjee, Sanjeev

    2015-01-01

    We report a Ni–Cr/C electrocatalyst with unprecedented mass-activity for the hydrogen evolution reaction (HER) in alkaline electrolyte. The HER kinetics of numerous binary and ternary Ni-alloys and composite Ni/metal-oxide/C samples were evaluated in aqueous 0.1 M KOH electrolyte. The highest HER mass-activity was observed for Ni–Cr materials which exhibit metallic Ni as well as NiOx and Cr2O3 phases as determined by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) analysis. The onset of the HER is significantly improved compared to numerous binary and ternary Ni-alloys, including Ni–Mo materials. It is likely that at adjacent Ni/NiOx sites, the oxide acts as a sink for OHads, while the metallic Ni acts as a sink for the Hads intermediate of the HER, thus minimizing the high activation energy of hydrogen evolution via water reduction. This is confirmed by in situ XAS studies that show that the synergistic HER enhancement is due to NiOx content and that the Cr2O3 appears to stabilize the composite NiOx component under HER conditions (where NiOx would typically be reduced to metallic Ni0). Furthermore, in contrast to Pt, the Ni(Ox)/Cr2O3 catalyst appears resistant to poisoning by the anion exchange ionomer (AEI), a serious consideration when applied to an anionic polymer electrolyte interface. Furthermore, we report a detailed model of the double layer interface which helps explain the observed ensemble effect in the presence of AEI. PMID:26191118

  15. Erosion Performance of HVOF-Sprayed Cr3C2-NiCr Coatings

    NASA Astrophysics Data System (ADS)

    Ji, Gang-Chang; Li, Chang-Jiu; Wang, Yu-Yue; Li, Wen-Ya

    2007-12-01

    Cr3C2-NiCr coatings were deposited by high-velocity oxygen fuel (HVOF) spraying process under spray conditions of different flows of oxygen and propane gases, and spray distances. The orthogonal regression experimental design method was used for systematic investigation of the influence of spray parameters on the erosion performance of Cr3C2-NiCr coatings. Erosion tests were performed at different jet angles of abrasive particles. The erosion mechanism of Cr3C2-NiCr coatings was examined through the surface morphology and cross-sectional microstructure of the eroded coatings. The correlations of the carbide particle size and carbide content with the erosion rate were examined. It was found that the erosion occurred dominantly by spalling of splats from the lamellar interfaces. The spalling resulted from the propagation of cracks parallel to the interfaces between the lamellae exposed to the surface and underlying coating. The carbide particle size and content in the coating influenced significantly the erosion performance of Cr3C2-NiCr coatings.

  16. Effect of Slag Composition on Inclusions in Si-Deoxidized 18Cr-8Ni Stainless Steels

    NASA Astrophysics Data System (ADS)

    Ren, Ying; Zhang, Lifeng; Fang, Wen; Shao, Shijie; Yang, Jun; Mao, Weidong

    2016-04-01

    Laboratory experiments and thermodynamic calculation for the Si-deoxidized 18Cr-8Ni stainless steel with CaO-Al2O3-SiO2-CaF2-MgO-MnO slag were performed to investigate the effect of slag composition on inclusions in Si-deoxidized 18Cr-8Ni stainless steels. A high-basicity slag improved the cleanness of stainless steel, while a low basicity slag lowered the Al2O3 content in inclusions, lowering the melting temperature of inclusions and improving the deformability of inclusions. Approximately, 15 pct content of MgO in the initial slag was beneficial to reduce the corrosion of refractory and would not influence the composition of inclusions. The Al2O3 in slag should be lowered to a minimum to reduce the Al2O3 content in inclusions in Si-deoxidized 18Cr-8Ni stainless steel. The log X_{{{{Al}}_{ 2} {{O}}_{ 3} }}i + log X_{{MgO}}i - log X_{MnO}i - log X_{{{{SiO}}2 }}i of inclusions was expressed as a linear function of log a_{{{{Al}}_{ 2} {{O}}_{ 3} }}^{{s}} + log a_{{CaO}}^{{s}} - log a_{MnO}^{{s}} - log a_{{{{SiO}}2 }}^{{s}} of the slag, which was used to predict the composition of inclusions based on the activity of Al2O3, CaO, SiO2, and MnO in the slag. Moreover, the equilibrium curve of Al-O and the stability diagram of inclusions in Si-deoxidized 18Cr-8Ni stainless steel at 1873 K (1600 °C) were calculated.

  17. Electronic circuits having NiAl and Ni.sub.3 Al substrates

    DOEpatents

    Deevi, Seetharama C.; Sikka, Vinod K.

    1999-01-01

    An electronic circuit component having improved mechanical properties and thermal conductivity comprises NiAl and/or Ni.sub.3 Al, upon which an alumina layer is formed prior to applying the conductive elements. Additional layers of copper-aluminum alloy or copper further improve mechanical strength and thermal conductivity.

  18. Electrochemical Behavior of CoNiCrAlY/ZrO2-Y2O3 Coated Layers with Atmospheric Pressure Plasma Technology in Seawater

    NASA Astrophysics Data System (ADS)

    Kim, Seong-Jong; Woo, Yong-Bin; Lee, Seung-Jun; Jeong, Jae-Yong

    2013-11-01

    Application of surface treatment has become common for protecting machine parts from oxidation, abrasion and corrosion induced by external environment. In particular, thermal spraying techniques are widely employed to improve wear, corrosion and thermal resistance. And compared to other methods they are simple and cost effective. However, the presence of porosity in the thermal spray coating can be highly detrimental because it provides access to penetration of corrosive matters, lowering corrosion resistance. Therefore, this research evaluate the electrochemical behavior under marine environment for aluminum-bronze alloy coated with MCrAlY and yttria-stabillized zirconia (YSZ) by atmospheric pressure plasma (APP) coating technology. Further application of carbon-based sealer removed voids and defects in the coating. The result reveled that, in case the voids and defects are completely removed, excellent corrosion resistance can be archived by application of good coating material along with formation of compact sealing layer.

  19. Dimensional effects in Ni-Cr multilayered thin films

    NASA Astrophysics Data System (ADS)

    Stearns, M. B.; Lee, C. H.

    1987-04-01

    The dimensionality of Ni-Cr multilayered structures (MLS) was studied from the variation of the temperature dependence of the saturation magnetization Ms with the Ni layer thickness. Since NiCr alloys containing more than 12% Cr are nonmagnetic the thickness of the interfaces and pure Ni regions can be obtained from the measured value of Ms by modeling the MLS and determining the thickness of the pure Ni regions. Assuming that the pure Ni regions are isolated sufficiently to behave independently, comparison was made with several theories. It was found that the observed behavior is similar to that described by the theory of Davis and Keffer with a surface anisotropy energy of about 0.1 that of the exchange energy. This theory uses nonperiodic boundary conditions and assumes a surface anisotropy field which causes the partial pinning of the surface spins. The magnetization decrease calculated with this theory falls off less rapidly with film thickness than other theories. At high fields the magnetization and Curie temperatures of the MLS having 20 Å or less of Ni is found to be field dependent. This is indicative that a considerable amount of the magnetic moments arise from itinerant d electrons.

  20. Cyanide-bridged NiCr and alternate NiFe-NiCr magnetic ultrathin films on functionalized Si(100) surface.

    PubMed

    Tricard, Simon; Costa-Coquelard, Claire; Mazerat, Sandra; Rivière, Eric; Huc, Vincent; David, Christophe; Miserque, Frédéric; Jegou, Pascale; Palacin, Serge; Mallah, Talal

    2012-04-21

    Sequential growth in solution (SGS) was performed for the magnetic cyanide-bridged network obtained from the reaction of Ni(H(2)O)(2+) and Cr(CN)(6)(3-) (referred to as NiCr) on a Si(100) wafer already functionalized by a Ni(II) complex. The growth process led to isolated dots and a low coverage of the surface. We used the NiFe network as a template to improve the growth of the magnetic network. We elaborated alternate NiFe (paramagnetic)-NiCr (ferromagnetic) ultrathin films around 6 nm thick. The magnetic behaviour confirmed the alternate structure with the ferromagnetic zones isolated between the paramagnetic ones since the evolution of the blocking temperature is consistent with the evolution of the layers' thickness expected from the SGS process. PMID:22344390

  1. Hydrogen-Resistant Fe/Ni/Cr-Base Superalloy

    NASA Technical Reports Server (NTRS)

    Bhat, Biliyar N.; Chen, Po-Shou; Panda, Binayak

    1994-01-01

    Strong Fe/Ni/Cr-base hydrogen- and corrosion-resistant alloy developed. Superalloy exhibits high strength and exceptional resistance to embrittlement by hydrogen. Contains two-phase microstructure consisting of conductivity precipitated phase in conductivity matrix phase. Produced in wrought, weldable form and as castings, alloy maintains high ductility and strength in air and hydrogen. Strength exceeds previously known Fe/Cr/Ni hydrogen-, oxidation-, and corrosion-resistant alloys. Provides higher strength-to-weight ratios for lower weight in applications as storage vessels and pipes that must contain hydrogen.

  2. An improved diffusion welding technique for TD-NiCr

    NASA Technical Reports Server (NTRS)

    Holko, K. H.

    1973-01-01

    An improved diffusion welding technique has been developed for TD-NiCr sheet. In the most preferred form, the improved technique consists of diffusion welding 320-grit sanded plus chemically polished surfaces of unrecrystallized TD-NiCr at 760 C under 140 MN/m2 pressure for 1hr followed by postheating at 1180 C for 2hr. Compared to previous work, this improved technique has the advantages of shorter welding time, lower welding temperature, lower welding pressure, and a simpler and more reproducible surface preparation procedure. Weldments were made that had parent-metal creep-rupture shear strength at 1100 C.

  3. Oxidation and Hot Corrosion Behavior of Plasma-Sprayed MCrAlY-Cr2O3 Coatings

    NASA Astrophysics Data System (ADS)

    Zhang, Tiantian; Huang, Chuanbing; Lan, Hao; Du, Lingzhong; Zhang, Weigang

    2016-08-01

    The oxidation and hot corrosion behavior of two atmospheric plasma-sprayed NiCoCrAlY-Cr2O3 and CoNiCrAlY-Cr2O3 coatings, which are primarily designed for wear applications at high temperature, were investigated in this study. The two coatings were exposed to air and molten salt (75%Na2SO4-25%NaCl) environment at 800 °C under cyclic conditions. Oxidation and hot corrosion kinetic curves were obtained by thermogravimetric technique. X-ray diffraction analysis and scanning electron microscopy with energy-dispersive x-ray spectrometry were employed to characterize the coatings' microstructure, surface oxides, and composition. The results showed that both coatings provided the necessary oxidation resistance with oxidation rates of about 1.03 × 10-2 and 1.36 × 10-2 mg/cm2 h, respectively. The excellent oxidation behavior of these two coatings is attributed to formation of protective (Ni,Co)Cr2O4 spinel on the surface, while as-deposited Cr2O3 in the coatings also acted as a barrier to diffusion of oxidative and corrosive substances. The greater presence of Co in the CoNiCrAlY-Cr2O3 coating restrained internal diffusion of sulfur and slowed down the coating's degradation. Thus, the CoNiCrAlY-Cr2O3 coating was found to be more protective than the NiCoCrAlY-Cr2O3 coating under hot corrosion condition.

  4. The effect of interstitial carbon on the mechanical properties and dislocation substructure evolution in Fe40.4Ni11.3Mn34.8Al7.5Cr6 high entropy alloys

    DOE PAGESBeta

    Wang, Zhangwei; Baker, Ian; Cai, Zhonghou; Chen, Si; Poplawsky, Jonathan D.; Guo, Wei

    2016-09-01

    A systematic study of the effects of up to 1.1 at. % carbon on the mechanical properties and evolution of the dislocation substructure in a series of a high entropy alloys (HEA) based on Fe40.4Ni11.3Mn34.8Al7.5Cr6 is presented. Transmission electron microscopy (TEM), synchrotron X-ray diffraction (XRD) and atom probe tomography (APT) were used to show that all the alloys are single-phase f.c.c. random solid solutions. The lattice constant, determined from synchrotron XRD measurements, increases linearly with increasing carbon concentration, which leads to a linear relationship between the yield strength and the carbon concentration. The dislocation substructures, as determined by a TEM,more » show a transition from wavy slip to planar slip and, at higher strains, and from cell-forming structure (dislocations cells, cell blocks and dense dislocation walls) to non-cell forming structure (Taylor lattice, microbands and domain boundaries) with the addition of carbon, features related to the increase in lattice friction stress. The stacking fault energy (measured via weak-beam imaging of the separation of dislocation partials) decreases with increasing carbon content, which also contributes to the transition from wavy slip to planar slip. The formation of non-cell forming structure induced by carbon leads to a high degree of strain hardening and a substantial increase in the ultimate tensile strength. In conclusion, the consequent postponement of necking due to the high strain hardening, along with the plasticity accommodation arising from the formation of microbands and domain boundaries, result in an increase of ductility due to the carbon addition.« less

  5. TEM studies of oxidized NiAl and Ni3Al cross sections

    NASA Technical Reports Server (NTRS)

    Doychak, J.; Ruhle, M.

    1989-01-01

    Cross sections of oxide scale/(Ni-Al) intermetallics were prepared by a new method and studied using primarily TEM. The cross sections were prepared by encasing an oxidized metal specimen sandwich in a low-melting-temperature zinc alloy. Observations of oxidized zirconium-doped beta-NiAl cross sections revealed crystallographic voids beneath an adherent Al2O3 scale. The oxide-metal interface was incoherent, but a high dislocation density in the metal near the interface suggested that a large tensile stress was induced by the attached oxide scale. A duplex Al2O3-NiAl2O4 scale formed on zirconium-doped and zirconium/boron-doped gamma-prime-Ni3Al alloys. Additional results are presented involving oxidation mechanisms and oxide-metal interface structures.

  6. Ferromagnetic Fe2CrAl Nanowires

    NASA Astrophysics Data System (ADS)

    Dulal, Rajendra; Dahal, Bishnu; Pegg, Ian L.; Philip, John

    Heusler alloy Fe2CrAl (FCA) nanowires were grown on silicon substrates. Nanowires have diameters in the range 50 to 200 nm and lengths up to 100 µm. They exhibit cubic L21 and A2 type structure with a space group, Pm m. Magnetic characterization reveals that they display ferromagnetic behavior and has a Curie temperature above 400 K. Magnetic behavior of FCA nanowires is different from the reported bulk behavior. Bulk FCA with L21 structure has a Curie temperature around 274 K. National Science Foundation under ECCS-0845501 and NSF-MRI, DMR-0922997.

  7. Evaporative segregation in 80% Ni-20% Cr and 60% Fe-40% Ni alloys

    NASA Technical Reports Server (NTRS)

    Gupta, K. P.; Mukherjee, J. L.; Li, C. H.

    1974-01-01

    An analytical approach is outlined to calculate the evaporative segregation behavior in metallic alloys. The theoretical predictions are based on a 'normal' evaporation model and have been examined for Fe-Ni and Ni-Cr alloys. A fairly good agreement has been found between the predicted values and the experimental results found in the literature.

  8. Microstructure and crack resistance of low carbon Cr-Ni and Cr-Ni-W steel after austempering

    NASA Astrophysics Data System (ADS)

    Avdjieva, Tatyana B.; Tsutsumanova, Gichka G.; Russev, Stoyan N.; Staevski, Konstantin G.

    2013-09-01

    The microstructure of the low carbon Cr-Ni steel after slow cooling from austenization temperature represents a mix of granulated bainite with islands from carbon-rich martensite and carbon-poor austenite. After quick cooling throwing in salt bath from austenization temperature the microstructure is lath bainite. However, in the same treatment conditions, the microstructure of the low carbon Cr-Ni-W steel is different — clusters consist from lath ferrite and retained austenite, disposed in the frame of parent's austenite grains. The cooling velocity has no effect upon the structure making. The impact toughness of the steel with tungsten content is bigger than the steel without tungsten.

  9. First-principles studies of Al-Ni intermetallic compounds

    SciTech Connect

    Shi Dongmin; Wen Bin; Melnik, Roderick; Yao Shan; Li Tingju

    2009-10-15

    The structural properties, heats of formation, elastic properties, and electronic structures of Al-Ni intermetallic compounds are analyzed here in detail by using density functional theory. Higher calculated absolute values of heats of formation indicate a very strong chemical interaction between Al and Ni for all Al-Ni intermetallic compounds. According to the computational single crystal elastic constants, all the Al-Ni intermetallic compounds considered here are mechanically stable. The polycrystalline elastic modulus and Poisson's ratio have been deduced by using Voigt, Reuss, and Hill (VRH) approximations, and the calculated ratio of shear modulus to bulk modulus indicated that AlNi, Al{sub 3}Ni, AlNi{sub 3} and Al{sub 3}Ni{sub 5} compounds are ductile materials, but Al{sub 4}Ni{sub 3} and Al{sub 3}Ni{sub 2} are brittle materials. With increasing Ni concentration, the bulk modulus of Al-Ni intermetallic compounds increases in a linear manner. The electronic energy band structures confirm that all Al-Ni intermetallic compounds are conductors. - Graphical abstract: Calculated bulk modulus compared to experimental and other theoretical values for the Al-Ni intermetallic compounds.

  10. Effect of alloying elements on <1 1 1> dislocation in NiAl: A first-principles study

    NASA Astrophysics Data System (ADS)

    Lin Lü, Bai; Qing Chen, Guo; Qu, Shen; Su, Hui; Long Zhou, Wen

    2013-05-01

    The calculation of the ductility criterion, the antiphase boundary energy and the Peierls stress indicate that compared with Cr, Au, Fe and Mn are better alloying elements improving the room-temperature ductility of polycrystalline NiAl. If the site preference behavior of Re, Os, Ir, Pt and Co can be reversed, these elements will also become better ductility elements and the Ni antisite at Al site is beneficial to the ductility of NiAl polycrystalline.

  11. Radiation resistance of (Ni,Fe)Cr2O4 spinels by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Van Brutzel, Laurent; Alvarez, Pierre; Chartier, Alain

    2014-05-01

    Molecular dynamics simulations are carried out to study primary radiation damage in NiCr2O4 and FeCr2O4 spinels, which are part of the corrosion layer of the vapour generators used in nuclear reactors. The radiation resistance of both spinels is evaluated by studying point defect recombination processes, threshold displacement energies, and 20 keV displacement cascades initiated with different PKA masses. Results are mainly in agreement with previous studies involving MgAl2O4 showing that radiation facilitates the transition to inverse spinel structure or NaCl structure. However, we find some differences between the two studied spinels indicating that NiCr2O4 is more sensitive to radiation.

  12. Structure and Tribological Characteristics of HVOF Coatings Sprayed from Powder Blends of Cr3C2-25NiCr and NiCrBSi Alloy

    NASA Astrophysics Data System (ADS)

    Määttä, A.; Kanerva, U.; Vuoristo, P.

    2011-01-01

    HVOF spraying was used to prepare coatings from mechanical blends of Cr3C2-25NiCr and NiCrBSi powders. The aim of this study is to study the tribological behavior of coatings prepared from such powder blends. The coatings were studied under dry sliding conditions particularly at high temperatures. Tribological properties of the coatings were characterized using a specific hot-button tribological tester at the temperature of 300 °C in air, and a pin-on-disk test at room temperature. Addition of NiCrBSi resulted in coatings, which showed low coefficient of friction in high temperatures, and in high levels of contact pressure and sliding speed.

  13. Transformation to Ni5Al3 in a 63.0 at. pct Ni-Al alloy

    NASA Technical Reports Server (NTRS)

    Khadkikar, P. S.; Locci, I. E.; Vedula, K.; Michal, G. M.

    1993-01-01

    Microstructures of 63 at. pct P/M Ni-Al alloys with a composition close to the stoichiometry of the Ni5Al3 phase were investigated using homogenized and quenched specimens aged at low temperatures for various times. Results of analyses of XRD data and electron microscopy observations were used for quantitative phase analysis, performed to calculate the (NiAl + Ni5Al3)/Ni5Al3 phase boundary locations. The measured lattice parameters of Ni5Al3 phase formed at 823, 873, and 923 K indicated an increase in tetragonality of the phase with increasing nickel content.

  14. Order-disorder transitions in NiCr 2S 4

    NASA Astrophysics Data System (ADS)

    Vaqueiro, P.; Powell, A. V.; Lebech, B.

    2000-03-01

    Order-disorder transitions in NiCr 2S 4 have been investigated by high-temperature powder neutron diffraction. At 835(5)°C, NiCr 2S 4 transforms from the monoclinic Cr 3S 4 structure to a hexagonal cation-deficient NiAs structure.

  15. WC-Co and Cr3C2-NiCr Coatings in Low- and High-Stress Abrasive Conditions

    NASA Astrophysics Data System (ADS)

    Kašparová, Michaela; Zahálka, František; Houdková, Šárka

    2011-03-01

    The article deals with the evaluation of abrasive wear resistance and adhesive strength of thermally sprayed coatings. The main attention was paid to differences between low- and high-stress abrasive conditions of the measuring. Conclusions include the evaluation of specific properties of the WC-Co and the Cr3C2-NiCr High Velocity Oxygen Fuel coatings and the evaluation of the changes in the behavior of the abrasive media. Mainly, the relationship between the low- and high-stress abrasion conditions and the wear mechanism in the tested materials was described. For the wear test, the abrasive media of Al2O3 and SiO2 sands were chosen. During wear tests, the volume loss of the tested materials and the surface roughness of the wear tracks were measured. The wear tracks on the tested materials and abrasive sands' morphologies were observed using Scanning Electron Microscopy. It was found that high-stress abrasive conditions change the coatings' behavior very significantly, particularly that of the Cr3C2-NiCr coating. Adhesive-cohesive properties of the coatings and relationships among individual structure particles were evaluated using tensile testing. It was found that the weak bond strength among the individual splats, structure particles, and phases plays a role in the poor wear resistance of the coatings.

  16. Blending Cr2O3 into a NiO-Ni electrocatalyst for sustained water splitting.

    PubMed

    Gong, Ming; Zhou, Wu; Kenney, Michael James; Kapusta, Rich; Cowley, Sam; Wu, Yingpeng; Lu, Bingan; Lin, Meng-Chang; Wang, Di-Yan; Yang, Jiang; Hwang, Bing-Joe; Dai, Hongjie

    2015-10-01

    The rising H2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr2 O3 -blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr2 O3 triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr2 O3 is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalyst enables an alkaline electrolyzer operating at 20 mA cm(-2) at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. The non-precious metal catalysts afford a high efficiency of about 15 % for light-driven water splitting using GaAs solar cells. PMID:26307213

  17. Blending Cr2O3 into a NiO-Ni electrocatalyst for sustained water splitting

    DOE PAGESBeta

    Gong, Ming; Zhou, Wu; Kenney, Michael James; Kapusta, Rich; Cowley, Sam; Wu, Yingpeng; Lu, Bingan; Lin, Meng -Chang; Wang, Di -Yan; Yang, Jiang; et al

    2015-08-24

    The rising H2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr2O3-blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr2O3 triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr2O3 is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalyst enables an alkaline electrolyzer operating at 20more » mA cm–2 at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. Thus, the non-precious metal catalysts afford a high efficiency of about 15 % for light-driven water splitting using GaAs solar cells.« less

  18. Ni-Al2O3 and Ni-Al composite high-aspect-ratio microstructures

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Sorrell, Melford; Kelly, Kevin W.; Ma, Evan

    1998-09-01

    High-aspect-ratio microstructures (HARMs) have a variety of potential applications in heat transfer, fluid mechanics, catalysts and other microelectromechanical systems (MEMS). The aim of this work is to demonstrate the feasibility to fabricate high performance particulate metal-matrix composite and intermetallic micromechanical structures using the LIGA process. Well-defined functionally graded Ni-Al2O3 and Ni-Al high-aspect-ratio microposts were electroformed into lithographically patterned PMMA holes from a nickel sulfamate bath containing submicron alumina and a diluted Watts bath containing microsized aluminum particles, respectively. SEM image analysis showed that the volume fraction of the alumina reached up to around 30% in the Ni-Al2O3 deposit. The Vickers microhardness of these composites is in the range of 418 through 545, which is higher than those of nickel microstructures from a similar particle-free bath and other Ni-based electrodeposits. In the work on Ni-Al electroplating, a newly developed diluted Watts bath was used to codeposit micron-sized aluminum particles. The intermetallic compound Ni3Al was formed by the reaction of nickel matrices and aluminum particles through subsequent annealing at 630 degrees Celsius. WDS and XRD analyses confirmed that the annealed coating is a two-phase (Ni-Ni3Al) composite. The maximum aluminum volume fraction reached 19% at a cathode current density of 12 mA cm-2, and the Vickers microhardness of the as-deposited coatings is in the range 392 - 515 depending on the amount of aluminum incorporated.

  19. Ni{sub 3}Al technology transfer

    SciTech Connect

    Sikka, V.K.; Viswanathan, S.; Santella, M.L.

    1997-04-01

    Ductile Ni{sub 3}Al and Ni{sub 3}Al-based alloys have been identified for a range of applications. These applications require the use of material in a variety of product forms such as sheet, plate, bar, wire, tubing, piping, and castings. Although significant progress has been made in the melting, casting, and near-net-shape forming of nickel aluminides, some issues still remain. These include the need for: (1) high-strength castable composition for many applications that have been identified; (2) castability (mold type, fluidity, hot-shortness, porosity, etc.); (3) weld reparability of castings; and (4) workability of cast or powder metallurgy product to sheet, bar, and wire. The four issues listed above can be {open_quotes}show stoppers{close_quotes} for the commercial application of nickel aluminides. This report describes the work completed to address some of these issues during FY 1996.

  20. Ni{sub 3}Al technology transfer

    SciTech Connect

    Sikka, V.K.; Santella, M.L.; Alexander, D.J.

    1995-05-01

    Ductile Ni{sub 3}Al and Ni{sub 3}Al-based alloys have been identified for a range of applications. These applications require the use of material in a variety of product forms such as sheet, plate, bar, tubing, piping, and castings. Although significant progress has been made in the melting, casting, and near-net-shape forming of nickel aluminides, some issues still remain. These include the need for (1)high-strength castable composition for turbochargers, furnace furniture, and hot-die applications; (2) castability (fluidity, hot-shortness, porosity, etc.); (3) weld reparability of castings; and (4) hot fabricability of cast ingots. All of the issues listed above can be {open_quotes}show stoppers{close_quotes} for the commercial application of nickel aluminides. This report describes work completed to address some of these issues during the fourth quarter of FY 1994.

  1. Oxidation behavior of single-crystal Al2O3-fiber-reinforced Ni3Al-based composites

    NASA Astrophysics Data System (ADS)

    Nourbakhsh, S.; Rhee, W. H.; Sahin, O.; Margolin, H.

    1994-07-01

    A series of single-crystal Al2O3-fiber-reinforced Ni3Al-based intermetallic matrix composites were fabricated by pressure casting. The matrices employed were binary Ni3Al, Ni3Al-0.5 at. pct Cr, and Ni3Al-0.34 at. pct Zr. The development of microstructure upon oxidation in air at either 1100 °C or 1200 °C was investigated by optical, scanning, and transmission electron microscopy. In air-oxidized binary Ni3Al, some of the fibers were fully or partially covered with a layer of oxide. A weak fiber/matrix bond in this system, which led to fiber debonding during composite processing, is believed to be responsible for the ingress of O into the composite and oxidation of the matrix in the debonded regions at the fiber/matrix interface. Addition of Cr to Ni3Al resulted in an almost threefold increase in fiber/matrix bond strength. No oxidation of the interface was observed. A thick layer of oxide was formed around all the fibers when the composite was thermally cycled prior to isothermal annealing. Addition of Zr to Ni3Al resulted in the formation of a layer of ZrO2 on the surface of the fibers during composite processing. The ZrO2 layer provided a fast path for the diffusion of O, which led to the formation of a rootlike oxide structure around the fibers. The rootlike structure consisted of a network of Al2O3-covered ZrO2.

  2. Examination of Multiphase (Zr,Ti)(V,Cr,Mn,Ni)2 Ni-MH Electrode Alloys: Part II. Solid-State Transformation of the Interdendritic B2 Phase

    NASA Astrophysics Data System (ADS)

    Bendersky, L. A.; Wang, K.; Boettinger, W. J.; Newbury, D. E.; Young, K.; Chao, B.

    2010-08-01

    Solidification microstructure of multicomponent (Zr,Ti)-Ni-(V,Cr,Mn,Co) alloys intended for use as negative electrodes in Ni-metal hydride (Ni-MH) batteries was studied in Part I of this series of articles. Part II of the series examines the complex internal structure of the interdendritic grains formed by solid-state transformation and believed to play an important role in the electrochemical charge/discharge characteristics of the overall alloy composition. By studying one alloy, Zr21Ti12.5V10Cr5.5Mn5.1Co5.0Ni40.2Al0.5Sn0.3, it is shown that the interdendritic grains solidify as a B2 (Ti,Zr)44(Ni,TM)56 phase, and then undergo transformation to Zr7Ni10-type, Zr9Ni11-type, and martensitic phases. The transformations obey orientation relationships between the high-temperature B2 phase and the low-temperature Zr-Ni-type intermetallics, and consequently lead to a multivariant structure. The major orientation relationship for the orthorhombic Zr7Ni10 type is [011]Zr7Ni10//[001]B2; (100)Zr7Ni10//(100)B2. The orientation relationship for the tetragonal Zr9Ni11 type is [001]Zr9Ni11//[001]B2; (130)Zr9Ni11//(100)B2. Binary Ni-Zr and ternary Ti-Ni-Zr phase diagrams were used to rationalize the formation of the observed domain structure.

  3. Role of oxygen diffusion at Ni/Cr2O3 interface in intergranular oxidation of Ni-Cr alloy

    NASA Astrophysics Data System (ADS)

    Medasani, Bharat; Sushko, Maria; Schreiber, Daniel; Rosso, Kevin; Bruemmer, Stephen

    Certain Ni-Cr alloys used in nuclear systems experience intergranular oxidation and stress corrosion cracking when exposed to high-temperature water leading to their degradation and unexpected failure. To develop a mechanistic understanding of grain boundary oxidation processes, we proposed a mesoscale metal alloy oxidation model that combines quantum Density Functional Theory (DFT) with mesoscopic Poisson-Nernst-Planck/classical DFT. This framework encompasses the chemical specificity of elementary diffusion processes and mesoscale reactive dynamics, and allows modeling oxidation processes on experimentally relevant length scales from first principles. As a proof of concept, a preliminary model was previously employed that limited oxygen diffusion pathways to those through the oxide phase and did not allow oxygen diffusion in the alloy or across oxide/alloy interfaces. In this work, we expand the model to include oxygen diffusion pathways along Ni/Cr2O3 interfaces and demonstrate the increasing importance of such pathways for intergranular oxidation of Ni-Cr alloys with high Cr content. This work is supported by the U.S. Dept. of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. Simulations are performed using PNNL Institutional Computing facility.

  4. Preparation of Al-Cr-Fe Coatings by Heat Treatment of Electrodeposited Cr/Al Composite Coatings

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Chen, Chang'an; Zhang, Guikai; Rao, Yongchu; Ling, Guoping

    Al-Cr-Fe coatings have been widely used in the surface engineering field of materials, due to their excellent corrosion resistance to water vapor and fused salt deposits. In this study, a new two-step approach was developed to prepare Al-Cr-Fe coatings on surfaces of SUS430 stainless steels. First, the Cr/Al composite coatings were prepared by electrodepositing Cr from aqueous solution then electrodepositing Al from AlCl3-1-ethyl-3-methyl-imidazolium chloride (AlCl3-EMIC) ionic liquid on SUS430 stainless steel substrate. In the second, heat treatment of the Cr/Al composite coatings was carried out to acquire Al-Cr-Fe coatings. Effects of the thickness of Cr/Al composite coatings, the time and temperature of heat treatment on composition and phase structure of alloy layers were studied by using scanning electron microscope (SEM), backscattered electron (BSE), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The structure transformation process and formation mechanism of Al-Cr-Fe coatings were discussed.

  5. Ordering reactions in an Ni-25Mo-8Cr alloy

    SciTech Connect

    Kumar, M.; Vasudevan, V.K.

    1996-04-01

    The transformations from short- to long-range order in Haynes{reg_sign} Alloy 242, a nominal Ni-25Mo-8Cr (in wt%) alloy, during isothermal aging at temperatures between 550 and 750 C are reported using microhardness measurements, and optical and transmission electron microscopy. Aging below the critical transformation temperature ({approximately} 775 C) led to considerable hardening; this hardening was associated with the formation of a very high volume fraction of Ni{sub 2} (Mo,Cr) domains/precipitates. The transformation from short- to long-range order was observed to proceed by a mechanism of continuous ordering at temperatures {le} 700 C, whereas at temperatures (750 C) close to the critical temperature a first order nucleation and growth mechanism appeared to be operative. The sequence of transformations are correlated with the associated diffraction effects and discussed in terms of theoretical formulations and experimental observations of other studies.

  6. Creep in Directionally Solidified NiAl-Mo Eutectics

    SciTech Connect

    Dudova, Marie; Kucharova, Kveta; Bartak, Tomas; Bei, Hongbin; George, Easo P; Somsen, Ch.; Dlouhy, A.

    2011-01-01

    A directionally solidified NiAl-Mo eutectic and an NiAl intermetallic, having respective nominal compositions Ni-45.5Al-9Mo and Ni-45.2Al (at.%), were loaded in compression at 1073 and 1173 K. Formidable strengthening by regularly distributed Mo fibres (average diameter 600 nm, volume fraction 14%) was observed. The fibres can support compression stresses transferred from the plastically deforming matrix up to a critical stress of the order of 2.5 GPa, at which point they yield. Microstructural evidence is provided for the dislocation-mediated stress transfer from the NiAl to the Mo phase.

  7. Preparation and properties of the Ni-Al/Fe-Al intermetallics composite coating produced by plasma cladding

    NASA Astrophysics Data System (ADS)

    Zhang, Li-Min; Liu, Bang-Wu; Sun, Dong-Bai

    2011-12-01

    A novel approach to produce an intermetallic composite coating was put forward. The microstructure, microhardness, and dry-sliding wear behavior of the composite coating were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrum (EDS) analysis, microhardness test, and ball-on-disc wear experiment. XRD results indicate that some new phases FeAl, Fe0.23Ni0.77Al, and Ni3Al exit in the composite coating with the Al2O3 addition. SEM results show that the coating is bonded with carbon steel metallurgically and exhibits typical rapid directional solidification structures. The Cr7C3 carbide and intermetallic compounds co-reinforced composite coating has a high average hardness and exhibits an excellent wear resistance under dry-sliding wear test compared with the Cr7C3 carbide-reinforced composite coating. The formation mechanism of the intermetallic compounds was also investigated.

  8. Directionally solidified pseudo-binary eutectics of Ni-Cr-(Hf, Zr)

    NASA Technical Reports Server (NTRS)

    Kim, Y. G.; Ashbrook, R. L.

    1975-01-01

    A pseudo-binary eutectic, in which the intermetallic Ni7Hf2 reinforces the Ni-Cr solid solution phase, was previously predicted in the Ni-Cr-Hf system by a computer analysis. The experimental determination of pseudo binary eutectic compositions and the directional solidification of the Ni-Cr-Hf, Zr, and Ni-Cr-Zr eutectic alloys are discussed. To determine unknown eutectics, chemical analyses were made of material bled from near eutectic ingots during incipient melting. Nominal compositions in weight percent of Ni-18.6Cr-24.0HF, Ni19.6Cr-12.8Zr-2.8Hf, and Ni-19.2Cr-14.8Zr formed aligned pseudo-binary eutectic structures. The melting points were about 1270 C. The reinforcing intermetallic phases were identified as noncubic (Ni,Cr)7Hf2 and (Ni,Cr)7(Hf,Zr)2, and face centered cubic (Ni,Cr)5Zr. The volume fraction of the reinforcing phases were about 0.5.

  9. Precipitation behavior of AlxCoCrFeNi high entropy alloys under ion irradiation.

    PubMed

    Yang, Tengfei; Xia, Songqin; Liu, Shi; Wang, Chenxu; Liu, Shaoshuai; Fang, Yuan; Zhang, Yong; Xue, Jianming; Yan, Sha; Wang, Yugang

    2016-01-01

    Materials performance is central to the satisfactory operation of current and future nuclear energy systems due to the severe irradiation environment in reactors. Searching for structural materials with excellent irradiation tolerance is crucial for developing the next generation nuclear reactors. Here, we report the irradiation responses of a novel multi-component alloy system, high entropy alloy (HEA) AlxCoCrFeNi (x = 0.1, 0.75 and 1.5), focusing on their precipitation behavior. It is found that the single phase system, Al0.1CoCrFeNi, exhibits a great phase stability against ion irradiation. No precipitate is observed even at the highest fluence. In contrast, numerous coherent precipitates are present in both multi-phase HEAs. Based on the irradiation-induced/enhanced precipitation theory, the excellent structural stability against precipitation of Al0.1CoCrFeNi is attributed to the high configurational entropy and low atomic diffusion, which reduces the thermodynamic driving force and kinetically restrains the formation of precipitate, respectively. For the multiphase HEAs, the phase separations and formation of ordered phases reduce the system configurational entropy, resulting in the similar precipitation behavior with corresponding binary or ternary conventional alloys. This study demonstrates the structural stability of single-phase HEAs under irradiation and provides important implications for searching for HEAs with higher irradiation tolerance. PMID:27562023

  10. Precipitation behavior of AlxCoCrFeNi high entropy alloys under ion irradiation

    PubMed Central

    Yang, Tengfei; Xia, Songqin; Liu, Shi; Wang, Chenxu; Liu, Shaoshuai; Fang, Yuan; Zhang, Yong; Xue, Jianming; Yan, Sha; Wang, Yugang

    2016-01-01

    Materials performance is central to the satisfactory operation of current and future nuclear energy systems due to the severe irradiation environment in reactors. Searching for structural materials with excellent irradiation tolerance is crucial for developing the next generation nuclear reactors. Here, we report the irradiation responses of a novel multi-component alloy system, high entropy alloy (HEA) AlxCoCrFeNi (x = 0.1, 0.75 and 1.5), focusing on their precipitation behavior. It is found that the single phase system, Al0.1CoCrFeNi, exhibits a great phase stability against ion irradiation. No precipitate is observed even at the highest fluence. In contrast, numerous coherent precipitates are present in both multi-phase HEAs. Based on the irradiation-induced/enhanced precipitation theory, the excellent structural stability against precipitation of Al0.1CoCrFeNi is attributed to the high configurational entropy and low atomic diffusion, which reduces the thermodynamic driving force and kinetically restrains the formation of precipitate, respectively. For the multiphase HEAs, the phase separations and formation of ordered phases reduce the system configurational entropy, resulting in the similar precipitation behavior with corresponding binary or ternary conventional alloys. This study demonstrates the structural stability of single-phase HEAs under irradiation and provides important implications for searching for HEAs with higher irradiation tolerance. PMID:27562023

  11. Microstructure of the Native Oxide Layer on Ni and Cr-doped Ni Nanoparticles

    SciTech Connect

    Wang, Chong M.; Baer, Donald R.; Bruemmer, Stephen M.; Engelhard, Mark H.; Bowden, Mark E.; Sundararajan, J. A.; Qiang, You

    2011-10-01

    Metallic or alloy nanoparticles exposed to air at room temperature will be instantaneously oxidized and covered by an oxide layer. However, for most cases, the true structural nature of the oxide layer formed at this stage is hard to determine. In this paper, we report the structure, morphology, and electronic structure (the density of state of both valence and conduction bands measured by a combination of XPS and EELS) of pure Ni and Cr-doped Ni nanoparticles synthesized using a cluster deposition process. Structural characterization carried out at the atomic level using aberration corrected high resolution transmission electron microscopy (HRTEM) in combination with electron and x-ray diffractions reveals that both pure Ni and Cr-doped Ni particles exposed to air at room temperature similarly possesses a core-shell structure of metal core covered by an oxide layer of typically 1.6 nm in thickness. There exists a critical size of ~ 6 nm, below which the particle is fully oxidized. The oxide particle corresponds to the rock-salt structured NiO and is faceted on the (001) planes. XPS of O-1s shows a strong peak that is attributed to (OH)-, which in combination with the atomic level HRTEM imaging indicates that the very top layer of the oxide is hydrolyzed as Ni(OH)2. Chemical composition analysis using EDS, EELS, and XPS indicates that the Cr dopant at the level of ~ 5at% forms solid solution with the Ni lattice. The Cr shows no segregation on the surface or preferential oxidation during the initial oxidation.

  12. Laser ablation of Al-Ni alloys and multilayers

    NASA Astrophysics Data System (ADS)

    Roth, Johannes; Trebin, Hans-Rainer; Kiselev, Alexander; Rapp, Dennis-Michael

    2016-05-01

    Laser ablation of Al-Ni alloys and multilayers has been studied by molecular dynamics simulations. The method was combined with a two-temperature model to describe the interaction between the laser beam, the electrons, and the atoms. As a first step, electronic parameters for the alloys had to be found and the model developed originally for pure metals had to be generalized to multilayers. The modifications were verified by computing melting depths and ablation thresholds for pure Al and Ni. Here known data could be reproduced. The improved model was applied to the alloys Al_3Ni, AlNi and AlNi_3. While melting depths and ablation thresholds for AlNi behave unspectacular, sharp drops at high fluences are observed for Al_3Ni and AlNi_3. In both cases, the reason is a change in ablation mechanism from phase explosion to vaporization. Furthermore, a phase transition occurs in Al_3Ni. Finally, Al layers of various thicknesses on a Ni substrate have been simulated. Above threshold, 8 nm Al films are ablated as a whole while 24 nm Al films are only partially removed. Below threshold, alloying with a mixture gradient has been observed in the thin layer system.

  13. Characterization of nanoscale NiAl-type precipitates in a ferritic steel by electron microscopy and atom probe tomography

    SciTech Connect

    Teng, Zhenke; Miller, Michael K; Ghosh, Gautam; Liu, Chain T; Huang, Shenyan; Russell, Kaye F; Fine, Morris E; Liaw, Peter K

    2010-01-01

    The microstructure of NiAl-type ({beta}{prime}) precipitates in an aged ferritic steel (Fe-12.7Al-9Ni-10.2Cr-1.9Mo, at.%) is characterized by transmission and analytical electron microscopy (AEM) and atom probe tomography (APT). The alloy shows a duplex precipitation of {beta}{prime} particles: primary with an average diameter of 130 nm and secondary with an average diameter of 3 nm. Based on APT, the primary and secondary {beta}{prime} have compositions of Ni{sub 41.2}Al{sub 43.6}Fe{sub 12.7}Cr{sub 0.8}Mo{sub 1.4} and Ni{sub 26.3}Al{sub 41.6}Fe{sub 26.9}Cr{sub 3.3}Mo{sub 1.7}, respectively.

  14. Correlation of the thermodynamic calculation and the experimental observation of Ni-Mo-Cr low alloy steel changing Ni, Mo, and Cr contents

    NASA Astrophysics Data System (ADS)

    Park, Sang-Gyu; Kim, Min-Chul; Lee, Bong-Sang; Wee, Dang-Moon

    2010-12-01

    SA508 Gr.4N Ni-Mo-Cr low alloy steel has improved fracture toughness and strength compared to commercial low alloy steels such as SA508 Gr.3 Mn-Mo-Ni low alloy steel, which has less than 1% Ni. Higher strength and fracture toughness of low alloy steels can be achieved by increasing the Ni and Cr contents. In this study, the effects of the alloying elements of Ni and Cr on the microstructural characteristics and mechanical properties of SA508 Gr.4N Ni-Mo-Cr low alloy steel are evaluated. Changes in the stable phases of SA508 Gr.4N low alloy steel with these alloying elements were evaluated using thermodynamic calculation software. These values were then compared with the observed microstructural results. Additionally, tensile tests and Charpy impact test were carried out to evaluate the mechanical properties. The thermodynamic calculations show that Ni mainly affects the change of the matrix phase of γ and α rather than the carbide phase. Contrary to the Ni effect, Cr and Mo primarily affect the precipitation behavior of the carbide phases of Cr 23C 6, Cr 7C 3 and Mo 2C. In the microscopic observations, the lath martensitic structure becomes finer as the Ni content increases without affecting the carbides. When the Cr content decreases, the Cr carbide becomes unstable and carbide coarsening occurs. Carbide Mo 2C in the form of fine needles were observed in the high-Mo alloy. Greater strength was obtained after additions of Ni and Mo and the transition properties were improved as the Ni and Cr contents increased. These results were correlated with the thermodynamic calculation results.

  15. Solidification Behavior of gamma'-Ni3Al Containing Alloys in the Ni-Al-O System

    NASA Technical Reports Server (NTRS)

    Copland, Evan

    2007-01-01

    The chemical activities of Al and Ni in gamma(prime)-Ni3Al-containing systems were measured using the multi-cell Knudsen effusion-cell mass spectrometry technique (multi-cell KEMS), over the composition range 8 - 32 at.%Al and temperature range T = 1400 - 1750 K. From these measurements a better understanding of the equilibrium solidification behaviour of gamma(prime)-Ni3Al-containing alloys in the Ni-Al-O system was established. Specifically, these measurements revealed that (1) gamma(prime)-Ni3Al forms via the peritectiod reaction, gamma + Beta (+ A12O3) = gamma (prime) (+ Al2O3), at 1633 +/- 1 K, (2) the {gamma + Beta + Al2O3} phase field is stable over the temperature range 1633 through 1640 K, and (3) equilibrium solidification occurs by the eutectic reaction, L (+ Al2O3) = gamma + Beta (+ Al2O3), at 1640 +/- 1 K and a liquid composition of 24.8 +/- 0.2 at.%Al (at an unknown oxygen content). When projected onto the Ni-Al binary, this behaviour is inconsistent with the current Ni-Al phase diagram and a new diagram is proposed. This new Ni-Al phase diagram explains a number of unusual steady-state solidification structures reported previously and provides a much simpler reaction scheme in the vicinity of the gamma(prime)-Ni3Al phase field.

  16. Effect of Bimetallic Ni-Cr Catalysts for Steam-CO2 Reforming of Methane at High Pressure.

    PubMed

    Choi, Bong Kwan; Park, Yoon Hwa; Moon, Dong Ju; Park, Nam Cook; Kim, Young Chul

    2015-07-01

    The present work was to carry out the development of high performance Ni-based catalyst for Steam-CO2 reforming of methane (SCR) which is suitable for Fischer-Tropsch synthesis of GTL- FPSO (floating, production, storage and offloading) process. The bimetallic Ni-Cr catalysts were prepared by co-impregnation method. The Ni and Cr loading amount were fixed at 12 wt% and 3~7 wt%, respectively. The catalytic reaction was conducted at 900 °C and 20 bar with reactant feed ratio of CH4:CO2:H2O:Ar = 1:0.8:1.3:1 and GHSV = 25,000 h(-1). The Cr-modified Ni/γ-Al2O3 catalyst was characterized by BET surface area analysis, X-ray diffraction (XRD), H2-temperature programmed reduction (TPR), H2-chmisorption, CO2-temperature programmed desorption (TPD) and Transmission electron microscopy(TEM). To confirm the amount and type of the carbon deposition, the used catalysts were examined by Thermogravitic analysis (TGA) and Field emission-scanning microscopy/Energy dispersive X-ray analysis (FE-SEM/EDX). It was found that the bimetallic Ni-Cr catalyst exhibits highly dispersed Ni particles with strong metal-to-support interaction (SMSI) as well as excellent catalytic activity, resulting in the suppression of Ni sintering and carbon deposition. PMID:26373119

  17. The electrodeposition of FeCrNi stainless steel: microstructural changes induced by anode reactions.

    PubMed

    Hasegawa, Madoka; Yoon, Songhak; Guillonneau, Gaylord; Zhang, Yucheng; Frantz, Cédric; Niederberger, Christoph; Weidenkaff, Anke; Michler, Johann; Philippe, Laetitia

    2014-12-21

    The FeCrNi alloy, whose composition is close to that of stainless steel 304, was prepared by electrodeposition and characterized. Nanocrystalline FeCrNi (nc-FeCrNi) was obtained by employing a double-compartment cell where the anode is separated from the cathode compartment, while amorphous FeCrNi (a-FeCrNi) was deposited in a conventional single electrochemical cell. The carbon content of nc-FeCrNi was found to be significantly lower than that of a-FeCrNi, suggesting that carbon inclusion is responsible for the change in the microstructure. The major source of carbon is associated with the reaction compounds at the anode electrode, presumably decomposed glycine. Crystal structure analysis by XRD and TEM revealed that the as-deposited nc-FeCrNi deposits consist of α-Fe which transforms to γ-Fe upon thermal annealing. Nanoindentation tests showed that nc-FeCrNi exhibits higher hardness than a-FeCrNi, which is consistent with the inverse Hall-Petch behavior. PMID:25367332

  18. Ni.sub.3 Al-based intermetallic alloys having improved strength above 850.degree. C.

    DOEpatents

    Liu, Chain T.

    2000-01-01

    Intermetallic alloys composed essentially of: 15.5% to 17.0% Al, 3.5% to 5.5% Mo, 4% to 8% Cr, 0.04% to 0.2% Zr, 0.04% to 1.5% B, balance Ni, are characterized by melting points above 1200.degree. C. and superior strengths at temperatures above 1000.degree. C.

  19. Interface stability in the Ni-Cr-AI system: Part I. morphological stability of β-γ diffusion couple interfaces at 1150°C

    NASA Astrophysics Data System (ADS)

    Merchant, Sailesh M.; Notis, Michael R.; Goldstein, Joseph I.

    1990-07-01

    Aluminide coatings on Ni-base superalloys offer resistance to oxidation and hot corrosion at elevated temperatures. Complex depositional and subsequent diffusional interactions of the coating with the substrate result in a multiphase product consisting primarily of β-NiAl and γ'-Ni3Al intermediate phases. An understanding of interfacial stability between the coating and the substrate is therefore necessary in order to explain the formation of such phases. The Ni-Cr-AI system serves to simplify the complex chemistry of most Ni-base superalloys. In this study, reaction diffusion and interfacial stability were investigated in solid-solid diffusion couples, consisting of a common β-Ni50Al end-member and a series of γ-pure Ni, binary Ni-Cr, and ternary Ni-Cr-Al alloys, isothermally annealed at 1150 °C for 49 hours. The morphological development of the interface was examined using optical metallography and quantitative information obtained using electron-probe microanalysis. A transition from a stable or planar to an unstable or nonplanar interface in the β-γ diffusion couples was observed with the systematic variation in Cr content of the γ end-member. Interface breakdown in the β-γ couples was explained by means of microstructural information gathered about interfaces, measured diffusion paths, and a knowledge of phase constitution relationships.

  20. Stratification Mechanism and Interface Characterization of (TiN), (TiC)/NiCrBSi Composite Coatings Synthesized by Laser Remelting

    NASA Astrophysics Data System (ADS)

    Liu, Rongxiang; Lei, Tingquan; Guo, Lixin

    TiC/TiN-reinforced composite coatings were fabricated on the substrate of Ti-6Al-4V alloy using laser remelting. X-ray diffraction (XRD) was used to identify the phases in the laser-clad composite coating; the interface characterization of the dilution zone-clad zone (IDC) and the dilution zone-heat-affected zone (IDH) was observed with a scanning electron microscope (SEM). The results show that the microstructure of a cross-section has stratification characterization, and consists of the clad zone (CZ), the dilution zone (DZ), the diffusion layer (DL) and the heat-affected zone (HAZ). The layer-by-layer microstructure results from the boundary layer phenomenon of viscous melt-fluid and diffusion. The kind of reinforced particle has an effect on the interface morphology, microstructure and flow characterization of the melt-fluid. The phase constitution in the clad zone consists of (Cr-Ni-Fe), TiC, Ni4B3, Ti2Ni, Cr2B and M23C6 for TiC+NiCrBSi coating, and (Cr-Ni-Fe), TiN, NiB, Cr2Ti and Ti2Ni for TiN+NiCrBSi coating. The interfaces of the IDC in the NiCrBSi-clad layer is clear and clean; those of TiC+NiCrBSi and TiN+NiCrBSi are illegible. Ti-Ni phases with acicular microstructure link dilution zone and clad zone, and two kinds of phase with acicular microstructure, are similar in composition and shape.

  1. Microstructure characterization and room temperature deformation of a rapidly solidified NiAl-based eutectic alloy containing trace Dy

    NASA Astrophysics Data System (ADS)

    Li, Hutian; Guo, Jianting; Huai, Kaiwen; Ye, Hengqiang

    2006-04-01

    The microstructure and room temperature compressive deformation behavior of a rapidly solidified NiAl-Cr(Mo)-Dy eutectic alloy fabricated by water-cooled copper mold method were studied by a combination of SEM, EDS and compressive tests. The morphology stability after hot isostatic pressing (HIP) treatment was evaluated. Rapid solidification resulted in a shift in the coupled zone for the eutectic growth towards the Cr(Mo) phase, indicating a hypoeutectic composition, hence increasing the volume fraction of primary dendritic NiAl. Meanwhile, significantly refined microstructure and lamellar/rod-like Cr(Mo) transition were observed due to trace rare earth (RE) element Dy addition and rapid solidification effects. Compared with the results in literature [H.E. Cline, J.L. Walter, Metall. Trans. 1(1970)2907-2917; P. Ferrandini, W.W. Batista, R. Caram, J. Alloys Comp. 381(2004)91-98], an interesting phenomenon, viz., NiAl halos around the primary Cr(Mo) dendrites in solidified NiAl-Cr(Mo) hypereutectic alloy, was not observed in this study. This difference was interpreted in terms of their different reciprocal nucleation ability. In addition, it was proposed that the localized destabilization of morphology after HIP treatment is closely related to the presence of primary NiAl dendrites. The improved mechanical properties can be attributed to the synergistic effects of rapid solidification and Dy addition, which included refined microstructure, suppression of the crack development along eutectic grain boundaries, enhancement of density of geometrically necessary dislocations located at NiAl/Cr(Mo) interfaces and the Cr solubility extension in NiAl.

  2. Strain hardening mechanisms in a Ni-Mo-Cr alloy

    SciTech Connect

    Dymek, S. ); Dollar, M. ); Klarstrom, D.L. )

    1991-01-01

    HAYNES 242 alloy has been recently developed for gas turbine components applications. This age-hardenable alloy, consisting essentially of Ni-25%Mo-8%Cr, utilizes a long-range-ordering reaction to form uniformly sized and distributed, extremely small (on the order of 10nm), ordered particles. Excellent strength and ductility at elevated temperatures, low thermal expansion characteristics and good oxidation resistance of Haynes 242 alloy has encouraged a number of studies designed to characterize its properties. What is lacking is an attempt to understand the fundamentals of the deformation and strengthening mechanisms in this alloy. This on-going research has been undertaken to explore deformation mechanisms in unaged and aged Haynes 242 alloy. The emphasis has been put on the effects of initial precipitation structure on the development of deformation structure and how it controls selected mechanical properties. This paper presents selected results and reports a change in the deformation mode from crystallographic glide in an unaged alloy into twinning in the presence of ordered particles. Deformation twinning in Ni-Mo and Ni-Mo-Cr alloys was reported earlier but was not discussed in detail. This research sheds light on possible origins of particle-induced twinning in alloys strengthened by small ordered particles.

  3. Ti-Cr-Al-O Thin Film Resistors

    SciTech Connect

    Jankowski, A F; Hayes, J P

    2002-03-21

    Thin films of Ti-Cr-Al-O are produced for use as an electrical resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O{sub 2}. Vertical resistivity values from 10{sup 4} to 10{sup 10} Ohm-cm are measured for Ti-Cr-Al-O films. The film resistivity can be design selected through control of the target composition and the deposition parameters. The Ti-Cr-Al-O thin film resistor is found to be thermally stable unlike other metal-oxide films.

  4. Oxidation of Fe-Cr-Al and Fe-Cr-Al-Y Single Crystals

    NASA Astrophysics Data System (ADS)

    Grabke, H. J.; Siegers, M.; Tolpygo, V. K.

    1995-03-01

    Single crystal samples of the alloy Fe-20%Cr-5%Al with and without Y-doping were used to study the "reactive element" (RE) effect, which causes improved oxidation behaviour and formation of a protective Al2O3 layer on this alloy. The oxidation was followed by AES at 10-7 mbar O2 up to about 1000 °C. Most observations were peculiar for this low pO2 environment, but yttrium clearly favors the formation of Al-oxide and stabilizes it also under these conditions, probably by favoring its nucleation. The oxides formed are surface compounds of about monolayer thickness, not clearly related to bulk oxides. Furthermore, the morphologies of oxide scales were investigated by SEM, after oxidation at 1000°C for 100 h at 133 mbar O2. On Fe-Cr-Al the scale is strongly convoluted and tends to spalling, whereas the presence of Y leads to flat scales which are well adherent. This difference is explained by a change in growth mechanism. The tendency for separation of oxide and metal was highest for the samples with low energy metal surface, i.e. (100) and (110), the scale was better adherent on the (111) oriented surface and on the polycrystalline specimen, since in the latter cases the overall energy for scale/metal separation is higher. All observations, from the low and from the high pO2 experiments, are discussed in relation to the approximately ten mechanisms proposed in the literature for explanation of the RE effects.

  5. The Al-Al3Ni Eutectic Reaction: Crystallography and Mechanism of Formation

    NASA Astrophysics Data System (ADS)

    Fan, Yangyang; Makhlouf, Makhlouf M.

    2015-09-01

    The characteristics of the Al-Al3Ni eutectic structure are examined with emphasis on its morphology and crystallography. Based on these examinations, the mechanism of formation of this technologically important eutectic is postulated. It is found that a thin shell of α-Al forms coherently around each Al3Ni fiber. The excellent thermal stability of the Al-Al3Ni eutectic may be attributed to the presence of this coherent layer.

  6. Control of Surface Segregation in Bimetallic NiCr Nanoalloys Immersed in Ag Matrix.

    PubMed

    Bohra, Murtaza; Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Toulkeridou, Evropi; Diaz, Rosa E; Bobo, Jean-François; Sowwan, Mukhles

    2016-01-01

    Cr-surface segregation is a main roadblock encumbering many magneto-biomedical applications of bimetallic M-Cr nanoalloys (where M = Fe, Co and Ni). To overcome this problem, we developed Ni95Cr5:Ag nanocomposite as a model system, consisting of non-interacting Ni95Cr5 nanoalloys (5 ± 1 nm) immersed in non-magnetic Ag matrix by controlled simultaneous co-sputtering of Ni95Cr5 and Ag. We employed Curie temperature (TC) as an indicator of phase purity check of these nanocomposites, which is estimated to be around the bulk Ni95Cr5 value of 320 K. This confirms prevention of Cr-segregation and also entails effective control of surface oxidation. Compared to Cr-segregated Ni95Cr5 nanoalloy films and nanoclusters, we did not observe any unwanted magnetic effects such as presence Cr-antiferromagnetic transition, large non-saturation, exchange bias behavior (if any) or uncompensated higher TC values. These nanocomposites films also lose their unique magnetic properties only at elevated temperatures beyond application requirements (≥800 K), either by showing Ni-type behavior or by a complete conversion into Ni/Cr-oxides in vacuum and air environment, respectively. PMID:26750659

  7. Control of Surface Segregation in Bimetallic NiCr Nanoalloys Immersed in Ag Matrix

    NASA Astrophysics Data System (ADS)

    Bohra, Murtaza; Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Toulkeridou, Evropi; Diaz, Rosa E.; Bobo, Jean-François; Sowwan, Mukhles

    2016-01-01

    Cr-surface segregation is a main roadblock encumbering many magneto-biomedical applications of bimetallic M-Cr nanoalloys (where M = Fe, Co and Ni). To overcome this problem, we developed Ni95Cr5:Ag nanocomposite as a model system, consisting of non-interacting Ni95Cr5 nanoalloys (5 ± 1 nm) immersed in non-magnetic Ag matrix by controlled simultaneous co-sputtering of Ni95Cr5 and Ag. We employed Curie temperature (TC) as an indicator of phase purity check of these nanocomposites, which is estimated to be around the bulk Ni95Cr5 value of 320 K. This confirms prevention of Cr-segregation and also entails effective control of surface oxidation. Compared to Cr-segregated Ni95Cr5 nanoalloy films and nanoclusters, we did not observe any unwanted magnetic effects such as presence Cr-antiferromagnetic transition, large non-saturation, exchange bias behavior (if any) or uncompensated higher TC values. These nanocomposites films also lose their unique magnetic properties only at elevated temperatures beyond application requirements (≥800 K), either by showing Ni-type behavior or by a complete conversion into Ni/Cr-oxides in vacuum and air environment, respectively.

  8. Control of Surface Segregation in Bimetallic NiCr Nanoalloys Immersed in Ag Matrix

    PubMed Central

    Bohra, Murtaza; Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Toulkeridou, Evropi; Diaz, Rosa E.; Bobo, Jean-François; Sowwan, Mukhles

    2016-01-01

    Cr-surface segregation is a main roadblock encumbering many magneto-biomedical applications of bimetallic M-Cr nanoalloys (where M = Fe, Co and Ni). To overcome this problem, we developed Ni95Cr5:Ag nanocomposite as a model system, consisting of non-interacting Ni95Cr5 nanoalloys (5 ± 1 nm) immersed in non-magnetic Ag matrix by controlled simultaneous co-sputtering of Ni95Cr5 and Ag. We employed Curie temperature (TC) as an indicator of phase purity check of these nanocomposites, which is estimated to be around the bulk Ni95Cr5 value of 320 K. This confirms prevention of Cr-segregation and also entails effective control of surface oxidation. Compared to Cr-segregated Ni95Cr5 nanoalloy films and nanoclusters, we did not observe any unwanted magnetic effects such as presence Cr-antiferromagnetic transition, large non-saturation, exchange bias behavior (if any) or uncompensated higher TC values. These nanocomposites films also lose their unique magnetic properties only at elevated temperatures beyond application requirements (≥800 K), either by showing Ni-type behavior or by a complete conversion into Ni/Cr-oxides in vacuum and air environment, respectively. PMID:26750659

  9. Characterizations and hot corrosion resistance of Cr3C2-NiCr coating on Ni-base superalloys in an aggressive environment

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

    In the current study, Cr3C2-NiCr coating was deposited on the Ni-base superalloys by using high velocity oxyfuel (HVOF) process for high temperature corrosive environment applications. Optical microscopy (OM), x-ray diffraction (XRD), scanning electron microscopy/energy-dispersive analysis (SEM/EDAX), microhardness tester, and electro probe microanalyzer (EMPA) techniques were used to characterize the coating with regard to coating thickness, porosity, microhardness, and microstructure. The thermogravimetric technique was used to establish kinetics of corrosion. The hot corrosion behaviors of the bare and Cr3C2-NiCr coated superalloys were studied after exposure to aggressive environment of Na2SO4-60% V2O5 salt mixture at 900 °C under cyclic conditions. The structure of the as-sprayed Cr3C2-NiCr coating mainly consisted of γ-nickel solid solution along with minor phases of Cr7C3 and Cr2O3. Coating has porosity less than 1.5% and microhardness in the range of 850-900 Hv (Vickers hardness). Some inclusions, unmelted and semimelted powder particles were observed in the structure of the coatings. The Cr3C2-NiCr coating has imparted necessary resistance to hot corrosion, which has been attributed to the formation of oxides of nickel and chromium, and spinel of nickel-chromium.

  10. Cyclic oxidation resistance of a reaction milled NiAl-AlN composite

    NASA Technical Reports Server (NTRS)

    Lowell, Carl E.; Barrett, Charles A.; Whittenberger, J. D.

    1990-01-01

    Based upon recent mechanical property tests a NiAl-AlN composite produced by cryomilling has very attractive high temperature strength. This paper focuses on the oxidation resistance of the NiAl-AlN composite at 1473 and 1573 K as compared to that of Ni-47Al-0.15Zr, one of the most oxidation resistant intermetallics. The results of cyclic oxidation tests show that the NiAl-AlN composite has excellent properties although not quite as good as those of Ni-47Al-0.15Zr. The onset of failure of the NiAl-AlN was unique in that it was not accompanied by a change in scale composition from alumina to less protective oxides. Failure in the composite appears to be related to the entrapment of AlN particles within the alumina scale.

  11. Investigation of the mechanical properties of FeNiCrMnSi high entropy alloy wear resistant

    NASA Astrophysics Data System (ADS)

    Buluc, G.; Florea, I.; Chelariu, R.; Popescu, G.; Carcea, I.

    2016-06-01

    In this paper we investigated microstructure, hardness and wear resistance for FeNiCrMnAl, high entropy alloy. The FeNiCrMnSi, high entropy alloy was elaborated in a medium induction furnace, by choosing the silicon, as an alliance element within the equi- atomic high entropy alloy, we managed to obtain a dendritic structure, the formation of intermetallic compounds or separated silicon. The medium hardness value of the investigated alloy was 948.33 HV and the medium value of the friction coefficient was 0.6655 in the first 20 seconds and 0.5425 for 1667 seconds. The volume loss of the high entropy alloy FeNiCrMnSi was 0.0557 mm3.

  12. Development of forming and joining technology for TD-NiCr sheet

    NASA Technical Reports Server (NTRS)

    Torgerson, R. T.

    1973-01-01

    Forming joining techniques and properties data were developed for thin-gage TD-NiCr sheet in the recrystallized and unrecrystallized conditions. Theoretical and actual forming limit data are presented for several gages of each type of material for five forming processes: brake forming, corrugation forming, joggling, dimpling and beading. Recrystallized sheet can be best formed at room temperature, but unrecrystallized sheet requires forming at elevated temperature. Formability is satisfactory with most processes for the longitudinal orientation but poor for the transverse orientation. Dimpling techniques require further development for both material conditions. Data on joining techniques and joint properties are presented for four joining processes: resistance seam welding (solid-state), resistance spot welding (solid-state), resistance spot welding (fusion) and brazing. Resistance seam welded (solid-state) joints with 5t overlap were stronger than parent material for both material conditions when tested in tensile-shear and stress-rupture. Brazing studies resulted in development of NASA 18 braze alloy (Ni-16Cr-15Mo-8Al-4Si) with several properties superior to baseline TD-6 braze alloy, including lower brazing temperture, reduced reaction with Td-Ni-Cr, and higher stress-rupture properties.

  13. Quasicrystalline and crystalline precipitation during isothermal tempering in a 12Cr-9Ni-4Mo maraging stainless steel

    SciTech Connect

    Liu, P.; Stigenberg, A.H.; Nilsson, J.O.

    1995-07-01

    A thorough microstructural investigation has been performed on a high strength maraging steel of the type 12%Cr-9%Ni-4%Mo-2%Cu-1%Ti. The major precipitate formed during isothermal aging at 475 C is a quasicrystalline phase possessing icosahedral symmetry termed R{prime}-phase with a typical chemical composition of 48%Mo-33%Fe-13%Cr-2%Ni-4%Si. At 550 C the major precipitate is trigonal R-phase with a typical composition of 45%Mo-31%Fe-18%Cr-4%Ni-2%Si. At 550 C also Laves phase with a composition of 48%Mo-35%Fe-13%Cr-2%Ni-2%Si could be observed. At both 475 and 550 C an ordered phase termed L-phase precipitated. This minority phase has an ordered face centered cubic (f.c.c.) structure of type L1{sub 0}. Its composition is typically 9%Fe-4%Cr-52%Ni-15%Mo.-16%Ti-4%Al. R{prime}-phase formed at 475 C transformed to R-phase and Laves phase during aging at 550 C. In an analogous manner, R-phase and Laves phase formed at 550 C transformed to R{prime}-phase during subsequent aging at 475 C. This transformation was rationalized by a strong similarity in crystal structure between quasicrystalline R{prime}-phase of icosahedral symmetry and Frank-Kasper phases such as R-phase and Laves phase.

  14. Shock induced reaction of Ni/Al nanopowder mixture.

    PubMed

    Meng, C M; Wei, J J; Chen, Q Y

    2012-11-01

    Nanopowder Ni/Al mixture (mixed in Al:Ni = 2:1 stoichiometry) was shock compressed by employing single and two-stage light gas gun. The particle size of Al and Ni are 100-200 nm and 50-70 nm respectively, morphologies of Al and Ni are sphere like either. Recovered product was characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. According to the XRD spectrum, the mixed powder undergo complete reaction under shock compression, reaction product consist of Ni2Al3, NiAl and corundum structure Al2O3 compound. Grain size of Ni-Al compound is less than 100 nm. With the shock pressure increasing, the ratio of Ni2Al3 decreased obviously. The corundum crystal size is 400-500 nm according to the SEM observation. The results of shock recovery experiments and analysis show that the threshold pressure for reaction of nano size powder Ni/Al mixture is much less than that of micro size powder. PMID:23421276

  15. Hybrid Co-Cr/W-WC and Ni-W-Cr-B/W-WC Coating Systems

    NASA Astrophysics Data System (ADS)

    Vernhes, L.; Azzi, M.; Bousser, E.; Schmitt, T.; Lamarre, J. M.; Klemberg-Sapieha, J. E.

    2016-01-01

    The aim of this study was to investigate the effects of subsurface materials on the performance of a wear-resistant thin film. The mechanical, tribological, and corrosion properties were assessed for two hybrid coating systems: (1) W-WC thin film and a laser cladded Co-Cr interlayer applied to a 316 stainless steel substrate and (2) the same W-WC thin film and a spray-and-fused Ni-W-Cr-B interlayer applied to an Inconel® 718 substrate. They were then compared to the same systems without an interlayer. The microstructures were analyzed by XRD, EDS, and SEM. The hardness and surface load-carrying capacity of the coating systems were determined by micro- and macrohardness testing. Rockwell indentation was used to assess coating adhesion (CEN/TS 1071-8). Tribological properties were assessed with a reciprocating tribometer, and corrosion resistance was determined by potentiodynamic polarization and electrochemical impedance spectroscopy. The originality of this work lies in the finding that, except for the Inconel 718/Ni-W-Cr-B/W-WC system, the wear rate decreases with decreasing hardness of the subsurface materials carrying the thin film due to the decreasing contact pressure for a given load. Another novel finding is the stress-induced phase transformation of the Co-Cr interlayer, which occurs beneath the thin film under high load.

  16. Mechanical Characterization of CrN/CrAlN Multilayer Coatings Deposited by Magnetron Sputtering System

    NASA Astrophysics Data System (ADS)

    Kaouther, Khlifi; Hafedh, Dhiflaoui; Lassaad, Zoghlami; Ahmed, Ben Cheikh Larbi

    2015-10-01

    Chromium-based coatings are deposited on a 100Cr6 (AISI 52100) substrate by a physical vapor deposition magnetron sputtering system. The coatings have different structures, such as a CrN monolayer and CrAlN multilayer. The structural and morphological compositions of the coatings were evaluated using glow discharge optical emission spectroscopy, atomic force microscopy, and cross-sectional scanning electron microscopy. Nano-indentation tests were performed to investigate the mechanical properties. Domes and craters are shown to be uniformly distributed over the entire surfaces of the two coatings. Additionally, the CrN/CrAlN multilayer coating exhibits a rough surface, attractive mechanical properties, a high compressive stress, and a high plastic and elastic deformation resistance. The improvement of the mechanical properties of the CrN/CrAlN coating is mainly attributed to a reduction in the crystallite size. We found that this reduction was related to three factors: (1) the compositional change resulting from the substitution of aluminum for chromium, which can produce a decrease in the interatomic distance; (2) the structure of CrN/CrAlN, which was characterized by grain size refinement; and (3) the high number of interfaces, which explains the widely accepted concept of dislocation blocking by the layer interfaces.

  17. Effect of Cr/C Ratio on Microstructure and Corrosion Performance of Cr3C2-NiCr Composite Fabricated by Laser Processing

    NASA Astrophysics Data System (ADS)

    Lou, Deyuan; Liu, Dun; He, Chunlin; Bennett, Peter; Chen, Lie; Yang, Qibiao; Fearon, Eamonn; Dearden, Geoff

    2016-01-01

    The present study focuses on the effect of different Cr/C ratios on the microstructure, microhardness, and corrosion resistance of Ni-based laser clad hardfacings, reinforced by in situ synthesized chromium carbide particles. Cr3C2-NiCr composites have been laser processed with graphite/Cr/Ni powder blends with varying Cr/C ratios. Following phase analysis (x-ray diffraction) and microstructure investigation (scanning electron microscopy; energy dispersive x-ray analysis; transmission electron microscopy), the solidification of laser melt pool is discussed, and the corrosion resistances are examined. Several different zones (planar, dendritic, eutectic and re-melt zone) were formed in these samples, and the thicknesses and shapes of these zones vary with the change of Cr/C ratio. The sizes and types of carbides and the content of reserved graphite in the composites change as the Cr/C ratio varies. With the content of carbides (especially Cr3C2) grows, the microhardness is improved. The corrosive resistance of the composites to 0.2M H2SO4 aqueous solution decreases as the Cr/C ratio reduces owing to not only the decreasing Cr content in the NiCr matrix but also the galvanic corrosion formed within the carbide and graphite containing Ni matrix.

  18. Spin-driven ordering of Cr in the equiatomic high entropy alloy NiFeCrCo

    NASA Astrophysics Data System (ADS)

    Niu, C.; Zaddach, A. J.; Oni, A. A.; Sang, X.; Hurt, J. W.; LeBeau, J. M.; Koch, C. C.; Irving, D. L.

    2015-04-01

    Spin-driven ordering of Cr in an equiatomic fcc NiFeCrCo high entropy alloy (HEA) was predicted by first-principles calculations. Ordering of Cr is driven by the reduction in energy realized by surrounding anti-ferromagnetic Cr with ferromagnetic Ni, Fe, and Co in an alloyed L12 structure. The fully Cr-ordered alloyed L12 phase was predicted to have a magnetic moment that is 36% of that for the magnetically frustrated random solid solution. Three samples were synthesized by milling or casting/annealing. The cast/annealed sample was found to have a low temperature magnetic moment that is 44% of the moment in the milled sample, which is consistent with theoretical predictions for ordering. Scanning transmission electron microscopy measurements were performed and the presence of ordered nano-domains in cast/annealed samples throughout the equiatomic NiFeCrCo HEA was identified.

  19. Spin-driven ordering of Cr in the equiatomic high entropy alloy NiFeCrCo

    SciTech Connect

    Niu, C.; Zaddach, A. J.; Oni, A. A.; Sang, X.; LeBeau, J. M.; Koch, C. C.; Irving, D. L.; Hurt, J. W.

    2015-04-20

    Spin-driven ordering of Cr in an equiatomic fcc NiFeCrCo high entropy alloy (HEA) was predicted by first-principles calculations. Ordering of Cr is driven by the reduction in energy realized by surrounding anti-ferromagnetic Cr with ferromagnetic Ni, Fe, and Co in an alloyed L1{sub 2} structure. The fully Cr-ordered alloyed L1{sub 2} phase was predicted to have a magnetic moment that is 36% of that for the magnetically frustrated random solid solution. Three samples were synthesized by milling or casting/annealing. The cast/annealed sample was found to have a low temperature magnetic moment that is 44% of the moment in the milled sample, which is consistent with theoretical predictions for ordering. Scanning transmission electron microscopy measurements were performed and the presence of ordered nano-domains in cast/annealed samples throughout the equiatomic NiFeCrCo HEA was identified.

  20. TI--CR--AL--O thin film resistors

    DOEpatents

    Jankowski, Alan F.; Schmid, Anthony P.

    2000-01-01

    Thin films of Ti--Cr--Al--O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti--Cr--Al--O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti--Cr--Al--O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti--Cr--Al--O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

  1. Nonequilibrium grain-boundary cosegregation of nitrogen and chromium in NiCrMoV steel

    NASA Astrophysics Data System (ADS)

    Zheng, Lei; Xu, Tingdong

    2005-12-01

    It is concluded in this article that nonequilibrium grain-boundary cosegregation (NCGS) of nitrogen and chromium occurs in NiCrMoV steel. That conclusion is reached from experimental observations of the parallel segregation isotherms and the maximum coverage of Cr and N at grain boundaries during the isotherms. This means that the nonequilibrium segregation of Cr induces that of N, in NiCrMoV steel.

  2. Interdiffusion and intrinsic diffusion in the NiAl /delta/ phase of the Al-Ni system

    NASA Technical Reports Server (NTRS)

    Shankar, S.; Seigle, L. L.

    1978-01-01

    Interdiffusion coefficients at 950 to 1150 C and the ratio of intrinsic diffusion coefficients at 1100 C were measured as functions of composition in the NiAl (delta) phase of the Al-Ni system, using a vapor-solid technique. Diffusivity values were also obtained for the Ni3Al (epsilon) and Ni (Al) solid solution (zeta) phases from 950 to 1150 C. The interdiffusion coefficient in NiAl (delta) varies several orders of magnitude over the delta phase field with a deep minimum in the diffusivity-composition curve at 48 to 49 at% Al. The ratio of intrinsic diffusion coefficients DNi/DAl, in the delta phase also varies with composition from a value of 3 to 3.5 below 50 at% Al to 0.1 or less above 50 at% Al.

  3. Boron-modified Ni3Al intermetallic compound formed by spark plasma sintering of mechanically activated Ni and Al powders

    NASA Astrophysics Data System (ADS)

    Shevtsova, L. I.; Ogneva, T. S.; Mul, D. O.; Esikov, M. A.; Larichkin, A. Yu; Malikov, V. N.

    2016-04-01

    A Ni3Al intermetallic compound was obtained by spark plasma sintering of mechanically activated Ni and Al powders in atomic ratio 3:1 respectively. Samples with boron addition of 0.1 and 0.2% (wt.) and samples without boron were obtained. The maximum value of the relative density (~99 %) has been obtained for the material by sintering of mechanically activated mixture powders modified with 0.1% of boron. No differences have been found between the structure of boron-modified Ni3Al and Ni3Al without boron addition. The maximum level of bending strength (2200 MPa) has been achieved for Ni3Al with 0.1% (wt.) of boron. This value is almost 3 times the bending strength of the sample of Ni3Al sintered without boron addition.

  4. Fretting Wear of Ti-48Al-2Cr-2Nb

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Lerch, Bradley A.; Draper, Susan L.

    2001-01-01

    An investigation was conducted to examine the wear behavior of gamma titanium aluminide (Ti-48Al-2Cr-2Nb in atomic percent) in contact with a typical nickel-base superalloy under repeated microscopic vibratory motion in air at temperatures from 296-823 K. The surface damage observed on the interacting surfaces of both Ti-48Al-2Cr-2Nb and superalloy consisted of fracture pits, oxides, metallic debris, scratches, craters, plastic deformation, and cracks. The Ti-48Al-2Cr-2Nb transferred to the superalloy at all fretting conditions and caused scuffing or galling. The increasing rate of oxidation at elevated temperatures led to a drop in Ti-48Al-2Cr-2Nb wear at 473 K. Mild oxidative wear was observed at 473 K. However, fretting wear increased as the temperature was increased from 473-823 K. At 723 and 823 K, oxide disruption generated cracks, loose wear debris, and pits on the Ti-48Al-2Cr-2Nb wear surface. Ti-48Al-2Cr-2Nb wear generally decreased with increasing fretting frequency. Both increasing slip amplitude and increasing load tended to produce more metallic wear debris, causing severe abrasive wear in the contacting metals. Keywords

  5. Neutron diffraction studies of the Na-ion battery electrode materials NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3

    NASA Astrophysics Data System (ADS)

    Yahia, H. Ben; Essehli, R.; Avdeev, M.; Park, J.-B.; Sun, Y.-K.; Al-Maadeed, M. A.; Belharouak, I.

    2016-06-01

    The new compounds NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 were synthesized by sol-gel method and their crystal structures were determined by using neutron powder diffraction data. These compounds were characterized by galvanometric cycling and cyclic voltammetry. NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 crystallize with a stuffed α-CrPO4-type structure. The structure consists of a 3D-framework made of octahedra and tetrahedra that are sharing corners and/or edges generating channels along [100] and [010], in which the sodium atoms are located. Of significance, in the structures of NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 a statistical disorder Ni2+/Cr3+ was observed on both the 8g and 4a atomic positions, whereas in NaCoCr2(PO4)3 the statistical disorder Co2+/Cr3+ was only observed on the 8g atomic position. When tested as negative electrode materials, NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 delivered specific capacities of 352, 385, and 368 mA h g-1, respectively, which attests to the electrochemical activity of sodium in these compounds.

  6. Environmentally Assisted Cracking of Commercial Ni-Cr-Mo Alloys - A Review

    SciTech Connect

    Rebak, R B

    2004-11-09

    Nickel-Chromium-Molybdenum alloys (Ni-Cr-Mo) are highly resistant to general corrosion, localized corrosion and environmentally assisted cracking (EAC). Cr acts as a beneficial element under oxidizing acidic conditions and Mo under reducing conditions. All three elements (Ni, Cr and Mo) act synergistically to provide resistance to EAC in environments such as hot concentrated chloride solutions. Ni-Cr-Mo alloys may suffer EAC in environments such as hot caustic solutions, hot wet hydrofluoric acid (HF) solutions and in super critical water oxidation (SCWO) applications. Not all the Ni-Cr-Mo alloys have the same susceptibility to cracking in the mentioned environments. Most of the available data regarding EAC is for the oldest Ni-Cr-Mo alloys such as N10276 and N06625.

  7. Microstructure and mechanical behavior of Fe30Ni 20Mn35Al15 and modified Fe30Ni 20Mn35Al15 alloys

    NASA Astrophysics Data System (ADS)

    Meng, Fanling

    A novel alloy with nominal composition Fe30Ni 20Mn35Al15 has been found to show good room-temperature strength and significant ductility. The current project is to study the wear properties of as-cast Fe30Ni20Mn35Al 15 and discuss the possibility of further improving the mechanical properties of this alloy. The dry sliding wear of as-cast Fe30Ni20Mn 35Al15 was studied in in four different environments, i.e. air, dry oxygen, dry argon and a 4% hydrogen/nitrogen mixture. Two-body and three-body abrasive wear mechanism was found for tests in oxygen-containing environments, while plastic flow mechanisms dominated the wear behavior for tests in argon. Hydrogen embrittlement led to 1000% increase of wear loss by causing more rapid crack nucleation of the asperities. The effects of different additions of chromium (≤ 8 at. %) on both microstructure and fracture behavior of Fe30Ni20Mn 35Al15 were investigated. All alloys consisted of (Ni, Al)-rich B2 and (Fe, Mn)-rich f.c.c. phases with most of the Cr residing in the f.c.c. phase. The addition of 6 at. % Cr not only increased the room temperature ductility, but also completely suppressed the environmental embrittlement observed in the Cr-free alloy at low strain rates. The effects of varying the Al concentration on the microstructures and tensile properties of six two-phase FeNiMnAl alloys with a composition close to Fe30Ni20Mn35Al15 were studied. The increase in f.c.c. volume fraction and f.c.c. lamellar width led to an increase in ductility and a decrease in yield strength. The correlation between the yield stress and f.c.c. lamellar spacing lambda obeyed a Hall-Petch-type relationship, i.e. sigmay=252+0.00027lambda-1, where the units for sigmay and lambda are MPa and meter, respectively. FeNiMnAl alloy with B2 and f.c.c. phases aligned along was reported to show high strength at room temperature. The mechanical properties of Fe 28Ni18Mn33Al21, consisting of (Ni, Al)-enriched B2 and (Fe, Mn)-enriched f.c.c. phases with

  8. LiCaAl/sub 6/:Cr/sup 3+/

    SciTech Connect

    Payne, S.A.; Chase, L.L.; Newkirk, H.W.; Smith, L.K.; Krupke, W.F. )

    1988-11-01

    The authors report the discovery of a new laser, LiCaAIF/sub 6/:Cr/sup 3/ (Cr/sup 3+/ :LiCAF). The intrinsic (extrapolated maximum) slope efficiency was found to be 67 percent. For comparison, they also measured the intrinsic slope efficiencies of BeAl/sub 2/O/sub 4/:Cr/sup 3+/ (alexandrite), Na/sub 3/Ga/sub 2/Li/sub 3/F/sub 12/:Cr/sup 3+/, and ScBO/sub 3/:Cr/sup 3+/, and obtained values of 65,28, and 26 percent, respectively. The tuning range of LiCaAIF/sub 6/:Cr/sup 3+/ was determined to be at least 720-840 nm. The conventional spectroscopic properties, such as the absorption, emission, and emission lifetimes as a function of temperature, are reported as well.

  9. Joining of Ni-TiC FGM and Ni-Al Intermetallics by Centrifugal Combustion Synthesis

    NASA Astrophysics Data System (ADS)

    Ohmi, Tatsuya; Mizuma, Kiminori; Matsuura, Kiyotaka; Iguchi, Manabu

    2008-02-01

    A centrifugal combustion synthesis (CCS) process has been investigated to join a Ni-Al intermetallic compound and a Ni-TiC cermet. The cermet, a tubular graphite mold, and a green compact of reactants consisting of Al, Ni and NiO were set in a centrifugal caster. When the combustion synthesis reaction was induced in the centrifugal force field, a synthesized molten Ni-Al alloy flowed into the graphite mold and joined to the cermet. The soundness of the joint interface depended on the volume percentage of TiC phase in the cermet. A lot of defects were formed near the interface between the Ni-TiC cermet and the cast Ni-Al alloy when the volume percentage of TiC was 50% or higher. For this kind of cermet system, using a functionally graded cermet such as Ni-10 vol.%TiC/Ni-25 vol.%TiC/Ni-50 vol.%TiC overcame this difficulty. The four-point bending strength of the joined specimen consisting of the three-layered FGM cermet and cast Ni-29 mol%Al alloy was 1010 MPa which is close to the result for a Ni-29 mol%Al alloy specimen.

  10. Joining of Ni-TiC FGM and Ni-Al Intermetallics by Centrifugal Combustion Synthesis

    SciTech Connect

    Ohmi, Tatsuya; Matsuura, Kiyotaka; Iguchi, Manabu; Mizuma, Kiminori

    2008-02-15

    A centrifugal combustion synthesis (CCS) process has been investigated to join a Ni-Al intermetallic compound and a Ni-TiC cermet. The cermet, a tubular graphite mold, and a green compact of reactants consisting of Al, Ni and NiO were set in a centrifugal caster. When the combustion synthesis reaction was induced in the centrifugal force field, a synthesized molten Ni-Al alloy flowed into the graphite mold and joined to the cermet. The soundness of the joint interface depended on the volume percentage of TiC phase in the cermet. A lot of defects were formed near the interface between the Ni-TiC cermet and the cast Ni-Al alloy when the volume percentage of TiC was 50% or higher. For this kind of cermet system, using a functionally graded cermet such as Ni-10 vol.%TiC/Ni-25 vol.%TiC/Ni-50 vol.%TiC overcame this difficulty. The four-point bending strength of the joined specimen consisting of the three-layered FGM cermet and cast Ni-29 mol%Al alloy was 1010 MPa which is close to the result for a Ni-29 mol%Al alloy specimen.

  11. High-performance Ni3Al synthesized from composite powders

    NASA Astrophysics Data System (ADS)

    Chiou, Wen-Chih; Hu, Chen-Ti

    1994-05-01

    Specimens of Ni3Al + B of high density (>99.3 Pct RD) and relatively large dimension have been synthesized from composite powders through processes of replacing plating and electroless Ni-B plating on Al powder, sintering, and thermal-mechanical treatment. The uniformly coated Ni layer over fine Al or Ni core particles constituting these coating/core composite powders has advantages such as better resistance to oxidation relative to pure Al powder, a greater green density as a compacted powder than prealloyed powder, the possibility of atomically added B to the material by careful choice of a suitable plating solution, and avoidance of the expensive powder metallurgy (PM) equipment such as a hot isostatic press (HIP), hot press (HP), etc. The final Ni3Al + B product is made from Ni-B-Al and Ni-B-Ni mixed composite powders by means of traditional PM processes such as compacting, sintering, rolling, and annealing, and therefore, the dimensions of the product are not constrained by the capacity of an HIP or HP. The properties of Ni3Al composite powder metallurgy (CPM) specimens tested at room temperature have been obtained, and comparison with previous reports is conducted. A tensile elongation of about 16 Pct at room temperature was attained.

  12. Point defects in the NiAl(100) surface.

    PubMed

    Lerch, D; Dössel, K; Hammer, L; Müller, S

    2009-04-01

    The stability of various point defects in NiAl(100) has been investigated by first-principles calculations. For Al-rich surfaces, Ni vacancies within the first Al layer are energetically most favourable. For Ni-rich surfaces, so-called double defects, consisting of both Ni-antisite atom in the first Al layer and a Ni vacancy within the second Ni layer, form the configuration of lowest energy, superior to singular Ni antisites. An additional and significant energy gain is found in both cases by mutual lateral interaction of the defects, when they are arranged in the diagonal direction. Respective [Formula: see text] ordered configurations were found as the most stable structures. A 50:50 mixture of both defect types turns out to be even lower in energy than the ideal Al-terminated NiAl(100) surface, proving the latter to be metastable only. This is in line with the often reported inability in experiments to prepare ideal NiAl(100) surfaces. PMID:21817482

  13. Investigation of superplastic behavior of NiAl and Ni{sub 3}Al duplex alloy

    SciTech Connect

    Liu Zhenyun; Lin Dongliang; Gu Yuefeng; Shan Aidang

    1997-12-31

    The superplastic behavior of a NiAl and Ni{sub 3}Al duplex alloy was investigated. It was found that the alloy exhibits superplastic behavior over a narrow temperature range, from 975 C to 1,025 C at the strain rate of 1.52 {times} 10{sup {minus}4}s{sup {minus}1}. A maximum tensile elongation of 149% was obtained at 1,000 C with the strain rate sensitivity up to 0.375. The superplastic deformation of the duplex alloy can be approximately described by an empirical equation of the form: {dot {var_epsilon}} = Ao{sup 2.67} exp({minus}303,000/RT). Optical microstructure and TEM observation show that the superplastic behavior mechanism of the investigated alloy is a process of continuous recovery and recrystallization during deformation.

  14. Single-Crystal NiAl-X Alloys Tested for Hot Corrosion

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.

    1999-01-01

    Single-crystal nickel aluminide (NiAl) has been investigated extensively throughout the last several years as a potential structural material in aero-gas turbine engines. The attractive features of NiAl in comparison to Ni-base superalloys include a higher melting point, lower density, higher thermal conductivity, and excellent oxidation resistance. However, NiAl suffers from a lack of ductility and fracture toughness at low temperatures and a low creep strength at high temperatures. Alloying additions of hafnium (Hf), gallium (Ga), titanium (Ti), and chromium (Cr) have each shown some benefit to the mechanical properties over that of the binary alloy. However, the collective effect of these alloying additions on the environmental resistance of NiAl-X was unclear. Hence, the present study was undertaken to examine the hot corrosion behavior of these alloys. A companion study examined the cyclic oxidation resistance of these alloys. Several single-crystal NiAl-X alloys (where X is Hf, Ti, Cr, or Ga) underwent hot corrosion testing in a Mach 0.3 burner rig at the NASA Lewis Research Center. Samples were tested for up to 300 1-hr cycles at a temperature of 900 C. It was found that increasing the Ti content from 1 to 5 at.% degraded the hot corrosion behavior. This decline in the behavior was reflected in high weight gains and large corrosion mound formation during testing (see the figures). However, the addition of 1 to 2 at.% Cr to alloys containing 4 to 5 at.% Ti appeared to greatly reduce the susceptibility of these alloys to hot corrosion attack and negated the deleterious effect of the increased Ti addition.

  15. Irradiation-enhanced reactivity of multilayer Al/Ni nanomaterials.

    PubMed

    Manukyan, Khachatur V; Tan, Wanpeng; deBoer, Richard J; Stech, Edward J; Aprahamian, Ani; Wiescher, Michael; Rouvimov, Sergei; Overdeep, Kyle R; Shuck, Christopher E; Weihs, Timothy P; Mukasyan, Alexander S

    2015-06-01

    We have investigated the effect of accelerated ion beam irradiation on the structure and reactivity of multilayer sputter deposited Al/Ni nanomaterials. Carbon and aluminum ion beams with different charge states and intensities were used to irradiate the multilayer materials. The conditions for the irradiation-assisted self-ignition of the reactive materials and corresponding ignition thresholds for the beam intensities were determined. We discovered that relatively short (40 min or less) ion irradiations enhance the reactivity of the Al/Ni nanomaterials, that is, significantly decrease the thermal ignition temperatures (Tig) and ignition delay times (τig). We also show that irradiation leads to atomic mixing at the Al/Ni interfaces with the formation of an amorphous interlayer, in addition to the nucleation of small (2-3 nm) Al3Ni crystals within the amorphous regions. The amorphous interlayer is thought to enhance the reactivity of the multilayer energetic nanomaterial by increasing the heat of the reaction and by speeding the intermixing of the Ni and the Al. The small Al3Ni crystals may also enhance reactivity by facilitating the growth of this Al-Ni intermetallic phase. In contrast, longer irradiations decrease reactivity with higher ignition temperatures and longer ignition delay times. Such changes are also associated with growth of the Al3Ni intermetallic and decreases in the heat of reaction. Drawing on this data set, we suggest that ion irradiation can be used to fine-tune the structure and reactivity of energetic nanomaterials. PMID:25915560

  16. Lanthanide Al-Ni base Ericsson cycle magnetic refrigerants

    DOEpatents

    Gschneidner, K.A. Jr.; Takeya, Hiroyuki

    1995-10-31

    A magnetic refrigerant for a magnetic refrigerator using the Ericsson thermodynamic cycle comprises DyAlNi and (Gd{sub 0.54}Er{sub 0.46})AlNi alloys having a relatively constant {Delta}Tmc over a wide temperature range. 16 figs.

  17. Phase competition in ternary Ti-Ni-Al system

    NASA Astrophysics Data System (ADS)

    Wierzba, Bartek

    2016-07-01

    In this paper the reactive diffusion in Ti-Ni-Al system is discussed at 1173 K. The calculation method based on the binary approach is presented. The key kinetic parameter is Wagner integral diffusion coefficient. The experimental and simulation results of reactive diffusion between pure Ti and β-NiAl are compared at 1173 K after 100 h.

  18. Lanthanide Al-Ni base Ericsson cycle magnetic refrigerants

    DOEpatents

    Gschneidner, Jr., Karl A.; Takeya, Hiroyuki

    1995-10-31

    A magnetic refrigerant for a magnetic refrigerator using the Ericsson thermodynamic cycle comprises DyAlNi and (Gd.sub.0.54 Er.sub.0.46)AlNi alloys having a relatively constant .DELTA.Tmc over a wide temperature range.

  19. The formation of twinned austenite in Fe-10Cr-10Ni-2W maraging steel

    SciTech Connect

    Suk, J.I.; Hong, S.H.; Nam, S.W. )

    1991-12-01

    The precipitation hardening mechanisms in high strength maraging steels have been studied in detail by many investigators, but limited information is available on the formation of austenite during aging. Some investigations have been concerned with the understanding of the effect of reverted austenite formed during aging on the mechanical properties. However, only a few investigations have been reported on the morphology and crystallographic feature of austenite. Shiang and Wayman first reported the twin-related and coupled morphology of Widmanstatten austenite plates which were frequently observed in maraging steel. In addition, Ameyama et al. reported the morphology and crystallographic features of austenite formed in ferrite grain during aging in a two-phase stainless steel, and found that each side of the austenite pair of twins satisfies the Kurdjumov-Sachs (K-S) orientation relationship with the parent phase. The morphology and crystallographic features of the reverted austenite formed during aging of Fe-10Cr-10Ni-2W stainless maraging steel have been investigated in this paper. The major strengthening precipitate in Fe-10Cr-10Ni-2W maraging steels has been identified as the rod-shaped {eta}-Ni{sub 3}Ti phase in our previous study. The peculiar morphology of the austenite, i.e., twinned austenite, also has been found in our studies of maraging steel in the Fe-10Cr-10Ni-2W lath martensite. In addition, computer simulation of the diffraction pattern is used to confirm the orientation relationships, such as the Kurdjumov-Sachs (K-S) relationship, the Nishiyama-Wasserman (N-W) relationship and the twin relationship by comparisons with the experimentaly observed results.

  20. Influence of FeCrAl Content on Microstructure and Bonding Strength of Plasma-Sprayed FeCrAl/Al2O3 Coatings

    NASA Astrophysics Data System (ADS)

    Zhou, Liang; Luo, Fa; Zhou, Wancheng; Zhu, Dongmei

    2016-02-01

    Low-power plasma-sprayed FeCrAl/Al2O3 composite coatings with 1.5 mm thickness have been fabricated for radar absorption applications. The effects of FeCrAl content on the coating properties were studied. The FeCrAl presents in the form of a few thin lamellae and numerous particles, demonstrating relatively even distribution in all the coatings. Results show that the micro-hardness and porosity decrease with the increase in FeCrAl content. With FeCrAl content increasing from 28 to 47 wt.%, the bonding strength of the coatings with 1.5 mm thickness increases from 10.5 to 27 MPa, and the failure modes are composed of cohesive and adhesive failure, which are ascribed to the coating microstructure and the residual stress, respectively.

  1. Physical and mechanical metallurgy of NiAl

    NASA Technical Reports Server (NTRS)

    Noebe, Ronald D.; Bowman, Randy R.; Nathal, Michael V.

    1994-01-01

    Considerable research has been performed on NiAl over the last decade, with an exponential increase in effort occurring over the last few years. This is due to interest in this material for electronic, catalytic, coating and especially high-temperature structural applications. This report uses this wealth of new information to develop a complete description of the properties and processing of NiAl and NiAl-based materials. Emphasis is placed on the controlling fracture and deformation mechanisms of single and polycrystalline NiAl and its alloys over the entire range of temperatures for which data are available. Creep, fatigue, and environmental resistance of this material are discussed. In addition, issues surrounding alloy design, development of NiAl-based composites, and materials processing are addressed.

  2. Influence of fatigue on the nanohardness of NiTiCr-wires

    SciTech Connect

    Frotscher, M.; Young, M. L.; Bei, Hongbin; George, Easo P; Neuking, K.; Eggeler, G.

    2009-01-01

    Testing parameters, such as rotational speed and bending radius, have a strong influence on the fatigue life of pseudoelastic NiTi shape-memory alloys during bending rotation fatigue (BRF) experiments [M. F. X. Wagner, Int. J. Mat. Res. 97 (2006), p. 1687-1696. and M. Frotscher, et al., Thermomechanical processing, microstructure and bending rotation fatigue of ultra-fine grained NiTiCr-wires, Proceedings of the International Conference for Shape Memory and Superelastic Technologies (SMST 2007), Tsukuba, Japan, ASM International, (2008), p. 149-158.]. Previous studies showed a decrease in the fatigue life for smaller bending radius (i.e. higher equivalent strain) and larger rotational speed. This observation is associated with an increase of dislocation density, the stabilization of stressinduced martensite during cycling, and an increase of the plateau stresses due to self-heating. In the present study, we examine the influence of these fatigue parameters on the nanohardness and shape recovery of pseudoelastic NiTiCr shape-memory alloy wires by nanoindentation. We show that nanoindentation is a suitable method for the characterization of fatigue-related microstructural changes, which affect the mechanical properties.

  3. Microstructural studies of nanocomposite thin films of Ni/CrN prepared by reactive magnetron sputtering.

    PubMed

    Kuppusami, P; Thirumurugesan, R; Divakar, R; Kataria, S; Ramaseshan, R; Mohandas, E

    2009-09-01

    Synthesis and characterization of nanocomposites of Ni/CrN thin films prepared by DC magnetron sputtering from a target of 50 wt.%Ni-50 wt.%Cr is investigated. The films prepared as a function of nitrogen flow rate and substrate temperature showed that the films contained Ni and CrN phases with crystallite sizes in the nanometer range. Measurement of nanomechanical properties of the composite films exhibited a significant decrease in the values of hardness and Young's modulus than those of pure CrN films. PMID:19928270

  4. Diffusional creep and creep-degradation in dispersion-strengthened Ni-Cr base alloys.

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1973-01-01

    Dispersoid-free regions were observed in the dispersion-strengthened alloy TD-NiCr (Ni-20 Cr-2 ThO2) after slow strain rate testing (stress rupture, creep, and fatigue) in air from 1145 to 1590 K. Formation of the dispersoid-free regions appears to be the result of diffusional creep. The net effect of creep in TD-NiCr is the degradation of the alloy to a duplex microstructure. Creep degradation of TD-NiCr is further enhanced by the formation of voids and intergranular oxidation in the dispersoid-free bands. Void formation was observed after as little as 0.13% creep deformation at 1255 K. The dispersoid-free regions apparently provide sites for void formation and oxide growth since the strength and oxidation resistance of Ni-20 Cr-2 ThO2.

  5. Oxidation behavior of TD-NiCr in a dynamic high temperature environment

    NASA Technical Reports Server (NTRS)

    Tenney, D. R.; Young, C. T.; Herring, H. W.

    1974-01-01

    The oxidation behavior of TD-NiCr has been studied in static and high-speed flowing air environments at 1100 and 1200 C. It has been found that the stable oxide morphologies formed on the specimens exposed to the static and dynamic environments were markedly different. The faceted crystal morphology characteristic of static oxidation was found to be unstable under high-temperature, high-speed flow conditions and was quickly replaced by a porous NiO 'mushroom' type structure. Also, it was found that the rate of formation of CrO3 from Cr2O3 was greatly enhanced by high gas velocity conditions. The stability of Cr2-O3 was found to be greatly improved by the presence of an outer NiO layer, even though the NiO layer was very porous. An oxidation model is proposed to explain the observed microstructures and overall oxidation behavior of TD-NiCr alloys.

  6. Effects of Additives and Impurity on the Adhesive Behavior of the NiAl(110)/Al2O3 (0001) Interface: An Ab Initio Study

    NASA Astrophysics Data System (ADS)

    Ozfidan, Isil; Chen, Kuiying; Fu, Ming

    2011-12-01

    Using ab initio density functional theory (DFT), the adhesive behavior of NiAl(110)/Al2O3(0001) interface in thermal barrier coatings was systematically studied with an emphasis on the effects of alloying additives and impurity elements. To reveal possible atomic-scale mechanisms, the separations between certain atoms at the interface, the electron localization function (ELF), and the electron density of states (DOS) are thoroughly investigated. First, effects of individual elements such as S, Pt, and Cr, and reactive elements (REs) Hf, Zr, and Y, on the work of separation, W sep, of the interface were examined. As expected, the segregation of S to the interface significantly degrades the adhesion, while the substitution of Pt for Ni adjacent to the interface does not enhance the W sep. Cr and RE addition to the interface individually result in a considerable increase of W sep. Second, the addition of Pt, Hf, and Cr to the S containing interface is shown to mitigate the detrimental effect of sulfur to some extent. Co doping the interface with a selected combination of (Pt, Hf), (Pt, Cr), (Cr, Hf), (Cr, Y), (Hf, Y), and (Y, Zr) was implemented to probe possible synergistic interactions between elements on W sep. Synergistic effects are detected on increasing W sep for (Hf, Y), (Hf, Zr) combinations. Co doping the interface with (Cr, Y) and (Cr, Hf), however, is found to weaken the adhesion. Through a detailed analysis of electronic structures in terms of ELF and DOS, four dominant bonds across the interface, RE-O, RE-Ni, Aloxide-Ni, and AlNiAl-O, are identified to play a decisive role in governing the adhesive strength of the interface.

  7. Microstructure of the Al-La-Ni-Fe system

    SciTech Connect

    Vasil’ev, A. L.; Ivanova, A. G.; Bakhteeva, N. D.; Kolobylina, N. N.; Orekhov, A. S.; Presnyakov, M. Yu.; Todorova, E. V.

    2015-01-15

    The microstructure of alloys based on the Al-La-Ni-Fe system, which are characterized by a unique ability to form metal glasses and nanoscale composites in a wide range of compositions, has been investigated. Al{sub 85}Ni{sub 7}Fe{sub 4}La{sub 4} and Al{sub 85}Ni{sub 9}Fe{sub 2}La{sub 4} alloys have been analyzed by electron microscopy (including high-resolution scanning transmission electron microscopy), energy-dispersive X-ray microanalysis, electron diffraction (ED), and X-ray diffraction (XRD). It is found that, along with fcc Al and Al{sub 4}La (Al{sub 11}La{sub 3}) particles, these alloys contain a ternary phase Al{sub 3}Ni{sub 1−x}Fe{sub x} (sp. gr. Pnma) isostructural to the Al{sub 3}Ni phase and a quaternary phase Al{sub 8}Fe{sub 2−x}Ni{sub x}La isostructural to the Al{sub 8}Fe{sub 2}Eu phase (sp. gr. Pbam). The unit-cell parameters of the Al{sub 3}Ni{sub 1−x}Fe{sub x} and Al{sub 8}Fe{sub 2−x}Ni{sub x}La compounds, determined by ED and refined by XRD, are a = 0.664(1) nm, b = 0.734(1) nm, and c = 0.490(1) nm for Al{sub 3}Ni{sub 1−x}Fe{sub x} and a = 1.258(3) nm, b = 1.448(3) nm, and c = 0.405(8) nm for Al{sub 8}Fe{sub 2−x}Ni{sub x}La. In both cases Ni and Fe atoms are statistically arranged, and no ordering is found. Al{sub 8}Fe{sub 2−x}Ni{sub x}La particles contain inclusions in the form of Al{sub 3}Fe δ layers.

  8. Atomistic Modeling of RuAl and (RuNi) Al Alloys

    NASA Technical Reports Server (NTRS)

    Gargano, Pablo; Mosca, Hugo; Bozzolo, Guillermo; Noebe, Ronald D.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Atomistic modeling of RuAl and RuAlNi alloys, using the BFS (Bozzolo-Ferrante-Smith) method for alloys is performed. The lattice parameter and energy of formation of B2 RuAl as a function of stoichiometry and the lattice parameter of (Ru(sub 50-x)Ni(sub x)Al(sub 50)) alloys as a function of Ni concentration are computed. BFS based Monte Carlo simulations indicate that compositions close to Ru25Ni25Al50 are single phase with no obvious evidence of a miscibility gap and separation of the individual B2 phases.

  9. Magnetic structures of nanometer scale Dy, Cr and Ni

    SciTech Connect

    Fitzsimmons, M.R.; Robinson, R.A.; Lawson, A.C.; Kwei, G.H.; Sickafus, K.E.; Eastman, J.A.; Burkel, E.

    1992-10-01

    Materials composed of nanometer-sized structures are becoming technologically relevant as the sizes of electronic devices approach the nanometer scale. Questions as to the performance and durability of these devices can be partially addressed through the characterization and understanding of the magnetic structures and properties of nanometer-sized materials. The purpose of the present work is to understand the relationship between the microstructure of nanocrystalline materials and their magnetic structures and properties. This paper summarizes three separate experiments: (1) an X-ray diffraction and anomalous absorption (XANES) study of nanocrystalline Dy, (2) neutron diffraction measurements of the magnetic structure of nanocrystalline Cr, and (3) the measurement of the magnetization density of a single twist grain boundary in Ni.

  10. Synthesis of nanostructured Cr{sub 3}C{sub 2}-25(Ni20Cr) coatings

    SciTech Connect

    He, J.; Ice, M.; Lavernia, E.J.

    2000-02-01

    On the basis of the nanocrystalline Cr{sub 3}C{sub 2}-25 (Ni20 Cr) feedstock powders produced by mechanical milling, a nanostructured coating has been synthesized using high velocity oxygen fuel (HVOF) thermal spraying. The properties of the nanostructured coating were compared to those of the conventional coating of the same composition using scanning electron microscope (SEM), transmission electron microscope (TEM), and microhardness tests. The nanostructured Cr{sub 3}C{sub 2}-25 (Ni20Cr) coating synthesized in this study had an average carbide particle size of 24 nm. Discontinuous elongated amorphous phases were observed in the nanostructured coating. The conventional Cr{sub 3}C{sub 2}-25 (Ni20Cr) coatings produced using blended elemental powders exhibited an inhomogeneous microstructure. The observed homogeneity of the nanostructured coating is attributed, in part, to the microstructural improvement of the starting powder. The nanostructured Cr{sub 3}C{sub 2}-25 (Ni20Cr) coating yielded an average microhardness value of 1020 DPH{sub 300}, which corresponds to a 20 pct increase in microhardness over that of the conventional coating. The nanostructured cr{sub 3}C{sub 2}-25 (Ni20Cr) coating also exhibited a higher apparent fracture toughness relative to that of the conventional coating. The apparent mechanical property improvements in the nanostructured coating were though to result from the uniformity of the microstructure and the high performance associated with a nanostructured structure. In addition, the mechanism that is present during the milling of a system containing nondeformable particles is discussed in light of the TEM observations.

  11. A ternary Ni-Al-W EAM potential for Ni-based single crystal superalloys

    NASA Astrophysics Data System (ADS)

    Fan, Qin-Na; Wang, Chong-Yu; Yu, Tao; Du, Jun-Ping

    2015-01-01

    Based on experiments and first-principles calculations, a ternary Ni-Al-W embedded-atom-method (EAM) potential is constructed for the Ni-based single crystal superalloys. The potential predicts that W atoms do not tend to form clusters in γ(Ni), which is consistent with experiments. The impurity diffusion of W in γ(Ni) is investigated using the five-frequency model. The diffusion coefficients and the diffusion activation energy of W are in reasonable agreement with the data in literatures. By W doping, the lattice misfit between the two phases decreases and the elastic constants of γ‧(Ni3Al) increase. As for alloyed elements Co, Re and W, the pinning effect of solute atom on the γ(Ni)/γ‧(Ni3Al) misfit dislocation increases with the increasing of the atomic radius.

  12. Hot Corrosion Behavior of Bare, Cr3C2-(NiCr) and Cr3C2-(NiCr) + 0.2wt.%Zr Coated SuperNi 718 at 900 °C

    NASA Astrophysics Data System (ADS)

    Mudgal, Deepa; Singh, Surendra; Prakash, Satya

    2015-01-01

    Corrosion in incinerators, power plants, and chemical industries are frequently encountered due to the presence of salts containing sodium, sulphur, and chlorine. To obviate this problem, bare and coated alloys were tested under environments simulating the conditions present inside incinerators and power plants. 0.2 wt.% zirconium powder was incorporated in the Cr3C2-(NiCr) coating powder. The original powder and Zr containing powder was sprayed on Superni 718 alloy by D-gun technique. The bare and coated alloys were tested under Na2SO4 + K2SO4 + NaCl + KCl and Na2SO4 + NaCl environment. The corrosion rate of specimens was monitored using weight change measurements. Characterization of the corrosion products has been done using FE-SEM/EDS and XRD techniques. Bare and coated alloys showed very good corrosion resistance under given molten salt environments. Addition of 0.2wt.%Zr in Cr3C2-25%(NiCr) coating further greatly reduced the oxidation rate as well as improved the adherence of oxide scale to the coating surface during the time of corrosion.

  13. Modeling of Ternary Element Site Substitution in NiAl

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Honecy, Frank

    2000-01-01

    It is well recognized that ternary alloying additions can have a dramatic impact on the behavior of ordered intermetallic alloys such as nickel aluminides. Properties as diverse as yield strength, fracture strength, fracture mode, cyclic oxidation resistance, creep strength, and thermal and electrical diffusivity can change by orders of magnitude when a few percent or less of a ternary element is added. Yet our understanding of the resulting point defect structures and the simple site preferences of ternary alloying additions is poor because these are extremely difficult characteristics to determine. This disconnection between the understanding of the structure and properties in ordered alloys is at least in part responsible for the limited development and commercialization of these materials. Theoretical methods have provided useful but limited insight in this area, since most techniques suffer from constraints in the type of elements and the crystallographic structures that can be modeled. In an effort to overcome these limitations, the Bozzolo-Ferrante-Smith (BFS) method for alloys was designed. After a brief description of this approximate quantum mechanical approach, we use BFS to investigate the energetics of Si, Ti, V, Cr, Fe, Co, Cu, Zr, Nb, Mo, Ru, Hf, Ta and W additions to B2-ordered, stoichiometric NiAl. In addition to determining the site preference for these alloying additions over a range of compositions, we include results for the concentration dependence of the lattice parameter. In this introductory paper, we performed our analyses in the absence of constitutional and thermal vacancies for alloys of the form Ni50(Al,X)50. Where data exist, a comparison between experimental, theoretical, and BFS results is also included.

  14. TDNiCr (ni-20Cr-2ThO2) forging studies

    NASA Technical Reports Server (NTRS)

    Filippi, A. M.

    1974-01-01

    Elevated temperature tensile and stress rupture properties were evaluated for forged TDNiCr (Ni-20Cr-2ThO2) and related to thermomechanical history and microstructure. Forging temperature and final annealed condition had pronounced influences on grain size which, in turn, was related to high temperature strength. Tensile strength improved by a factor of 8 as grain size changed from 1 to 150 microns. Stress-rupture strength was improved by a factor of 3 to 5 by a grain size increase from 10 to 1000 microns. Some contributions to the elevated temperature strength of very large grain material may also occur from the development of a strong texture and a preponderance of small twins. Other conditions promoting the improvement of high temperature strength were: an increase of total reduction, forging which continued the metal deformation inherent in the starting material, a low forging speed, and prior deformation by extrusion. The mechanical properties of optimally forged TDNiCr compared favorably to those of high strength sheet developed for space shuttle application.

  15. Point defect processes in neutron irradiated Ni, Fe-15Cr-16Ni and Ti-added modified SUS316SS

    NASA Astrophysics Data System (ADS)

    Horiki, M.; Yoshiie, T.; Sato, K.; Xu, Q.

    2013-05-01

    The defect structures in Ni, Fe-15Cr-16Ni and Ti-added modified SUS316SS (modified SUS316) were examined after neutron irradiation below 0.3 dpa by the Japan Materials Testing Reactor and Belgian Reactor 2 to compare their defect structural evolution. The growth behaviour of interstitial-type dislocation loops (I-loops), stacking fault tetrahedra (SFTs) and voids was found to be quite different among these specimens. I-loops developed at lower temperatures in Ni than in Fe-15Cr-16Ni and modified SUS316, and more swelling occurred in Ni than in Fe-15Cr-16Ni. Finally, there were no voids in modified SUS316. These results were analysed in terms of the I-loop energy. A large discrepancy was found between the analytical results and experimental observations for Ni and modified SUS316, which suggests the formation of unfaulted I-loops directly from collision cascades. The growth of SFTs was detected in Fe-15Cr-16Ni and modified SUS316, and can be explained by a change in the dislocation bias of SFTs resulting from the absorption of alloying elements.

  16. Behavior of Ni, Zn and Cr during low temperature aqueous Fe oxidation processes on Mars

    NASA Astrophysics Data System (ADS)

    Zhao, Yu-Yan S.; McLennan, Scott M.

    2013-05-01

    The behavior of Ni(II), Zn(II) and Cr(III) during the melanterite (FeSO4·7H2O) to hematite (α-Fe2O3) oxidative transformations involving evolution pathways via jarosite ((H3O,K)Fe3(OH)6(SO4)2), schwertmannite (Fe8O8(OH)6(SO4)) and goethite (α-FeOOH) were investigated in an acidic saturated MgSO4 matrix. Results provide important clues about how elevated levels of trace elements are incorporated into the secondary Fe mineralogy assemblages found on Mars and the mechanism for formation of hematitic concretions at Meridiani Planum on Mars. Our results demonstrate that starting at the same concentrations in the initial solution, final amounts of Ni, Zn and Cr in hematite via different pathways are very different. In Path 1 (melanterite → jarosite → hematite), partitioning of Ni, Zn and Cr into jarosite and hematite (formed through dissolution of jarosite) is most likely in the order: Cr > Zn > Ni. In Path 2 (melanterite → schwertmannite → goethite → hematite), schwertmannite and goethite exhibited strong affinities for divalent Ni and Zn. During such a pathway, Ni should accumulate more than Zn by at least a factor of two, and partitioning of Ni, Zn and Cr to the hematite is most likely in the order: Cr > Ni > Zn. Therefore, our results suggest that the high Ni and moderate Zn distribution pattern observed in Meridiani hematitic spherule-bearing samples can be explained best by the schwertmannite-goethite to hematite pathway (Path 2), without need for an additional high Ni source in this region. Although the lack of goethite at Meridiani renders it uncertain if goethite ever served as a precursor to facilitate hematite formation, dehydration of nano-crystalline goethite is thermodynamically favored and cannot be ruled out. On the other hand, if hematitic concretions were formed by dissolution of jarosite (Path 1), then much higher initial Ni/Zn ratios than 1 in initial diagenetic fluids may be necessary to explain the elevated levels of Ni in the spherules

  17. Synthesis, characterization and mechanical properties of nanocrystalline NiAl

    SciTech Connect

    Choudry, M. |; Eastman, J.A.; DiMelfi, R.J.; Dollar, M.

    1996-11-01

    Nanocrystalline NiAl was produced from pre-cast alloys using an electron beam inert gas condensation system. In-situ compaction was carried out at 100-300 C under vacuum conditions. Energy dispersive spectroscopy was used to determine chemical composition and homogeneity. Average grain sizes in the range 4-10 nm were found from TEM dark field analyses. A compression-cage fixture was designed to perform disk bend tests. These tests revealed substantial room temperature ductility in nanocrystalline NiAl, while coarse grained NiAl showed no measurable room temperature ductility.

  18. Powder processing of NiAl for elevated temperature strength

    SciTech Connect

    Whittenberger, J.D.; Hebsur, M.; Grahle, P.; Arzt, E.; Behr, R.; Zoeltzer, K.

    1997-12-31

    In an effort to superimpose two different elevated temperature strengthening mechanisms in NiAl, one lot of an oxide dispersion strengthened (ODS) NiAl powder has been milled in liquid nitrogen (cryomilled) to introduce AlN particles at the grain boundaries, and a second lot of ODS powder was simply roasted in gaseous nitrogen as an alternative means to produce AlN reinforced grain boundaries. Powder from both of these lots as well as the starting material have been consolidated by hot extrusion and tested at 1,300 K. Both nitrogen roasting and cryomilling produced AlN within the ODS NiAl matrix which strengthened the alloy; however, based on the AlN content, cryomilling is more effective.

  19. Reaction synthesis of Ni-Al based particle composite coatings

    SciTech Connect

    SUSAN,DONALD F.; MISIOLEK,WOICECK Z.; MARDER,ARNOLD R.

    2000-02-11

    Electrodeposited metal matrix/metal particle composite (EMMC) coatings were produced with a nickel matrix and aluminum particles. By optimizing the process parameters, coatings were deposited with 20 volume percent aluminum particles. Coating morphology and composition were characterized using light optical microscopy (LOM), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Differential thermal analysis (DTA) was employed to study reactive phase formation. The effect of heat treatment on coating phase formation was studied in the temperature range 415 to 1,000 C. Long-time exposure at low temperature results in the formation of several intermetallic phases at the Ni matrix/Al particle interfaces and concentrically around the original Al particles. Upon heating to the 500--600 C range, the aluminum particles react with the nickel matrix to form NiAl islands within the Ni matrix. When exposed to higher temperatures (600--1,000 C), diffusional reaction between NiAl and nickel produces ({gamma})Ni{sub 3}Al. The final equilibrium microstructure consists of blocks of ({gamma}{prime})Ni{sub 3}Al in a {gamma}(Ni) solid solution matrix, with small pores also present. Pore formation is explained based on local density changes during intermetallic phase formation and microstructural development is discussed with reference to reaction synthesis of bulk nickel aluminides.

  20. MODELING OF NI-CR-MO BASED ALLOYS: PART II - KINETICS

    SciTech Connect

    Turchi, P A; Kaufman, L; Liu, Z

    2006-07-07

    The CALPHAD approach is applied to kinetic studies of phase transformations and aging of prototypes of Ni-Cr-Mo-based alloys selected for waste disposal canisters in the Yucca Mountain Project (YMP). Based on a previous study on alloy stability for several candidate alloys, the thermodynamic driving forces together with a newly developed mobility database have been used to analyze diffusion-controlled transformations in these Ni-based alloys. Results on precipitation of the Ni{sub 2}Cr-ordered phase in Ni-Cr and Ni-Cr-Mo alloys, and of the complex P- and {delta}-phases in a surrogate of Alloy 22 are presented, and the output from the modeling are compared with experimental data on aging.

  1. Bond strength of three dental porcelains to Ni-Cr and Co-Cr-Ti alloys.

    PubMed

    Fernandes Neto, Alfredo Julio; Panzeri, Heitor; Neves, Flavio Domingues; Prado, Ricardo Alves do; Mendonça, Gustavo

    2006-01-01

    Ceramometal bond strength has played an important role for the replacement of gold alloys by nickel-chromium alloys in dentistry. This study evaluated the metal/porcelain bond strength of three ceramic systems (Vita VMK 88, Williams and Duceram) associated with three nickel-chromium alloys (Durabond, Lite Cast B and Resistal P) and one experimental cobalt-chromium-titanium alloy. Thirty cast cylinder specimens (15 mm in height; 6 mm in diameter) were obtained for each alloy, in away that 10 specimens of each alloy were tested with each porcelain. Bond strength was measured with an Emic screw-driven mechanical testing machine by applying parallel shear forces to the specimens until fracture. Kruskal-Wallis and Mann-Whitney U tests were used for statistical analysis of the alloy/ceramic combinations (p<0.05). Resistal P/Duceram had significantly higher bond strength (44.38+/-9.12 MPa) (p<0.05) than the other combinations, except for Co-Cr-Ti alloy/Vita VMK 88 (38.41+/-12.64 MPa). The association of the experimental Co-Cr-Ti alloy with Williams porcelain had significantly higher bond strength (28.20+/-3.86 MPa) than the combination of other alloys with the same porcelain (p<0.05). Based of these results and within the limitations of an in vitro study, it may be concluded that the bond strength of the three ceramic systems to the Ni-Cr and Co-Cr-Ti alloys varied significantly, indicating that metal/ceramic compatibility was very important to the bond strength. PMID:16721460

  2. High temperature stability, interface bonding, and mechanical behavior in (beta)-NiAl and Ni3Al matrix composites with reinforcements modified by ion beam enhanced deposition

    NASA Astrophysics Data System (ADS)

    Grummon, D. S.

    1992-01-01

    In preparation for experiments with surface modified Al2O3 reinforcements in (beta)NiAl, diffusion bonding experiments were conducted. FP alumina fibers were prepared with ion sputtered surface films (Al2O3, Al, Ni) and then composited with (beta)NiAl slabs and hot pressed. After 70 thermal cycles, interfacial shear strength was measured. A roughness mechanism is proposed for the observed increased strength of the coated fibers. Creep in Ni3Al was studied.

  3. Directionally Solidified NiAl-Based Alloys Studied for Improved Elevated-Temperature Strength and Room-Temperature Fracture Toughness

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, Sai V.; Locci, Ivan E.; Salem, Jonathan A.

    2000-01-01

    Efforts are underway to replace superalloys used in the hot sections of gas turbine engines with materials possessing better mechanical and physical properties. Alloys based on the intermetallic NiAl have demonstrated potential; however, they generally suffer from low fracture resistance (toughness) at room temperature and from poor strength at elevated temperatures. Directional solidification of NiAl alloyed with both Cr and Mo has yielded materials with useful toughness and elevated-temperature strength values. The intermetallic alloy NiAl has been proposed as an advanced material to extend the maximum operational temperature of gas turbine engines by several hundred degrees centigrade. This intermetallic alloy displays a lower density (approximately 30-percent less) and a higher thermal conductivity (4 to 8 times greater) than conventional superalloys as well as good high-temperature oxidation resistance. Unfortunately, unalloyed NiAl has poor elevated temperature strength (approximately 50 MPa at 1027 C) and low room-temperature fracture toughness (about 5 MPa). Directionally solidified NiAl eutectic alloys are known to possess a combination of high elevated-temperature strength and good room-temperature fracture toughness. Research has demonstrated that a NiAl matrix containing a uniform distribution of very thin Cr plates alloyed with Mo possessed both increased fracture toughness and elevated-temperature creep strength. Although attractive properties were obtained, these alloys were formed at low growth rates (greater than 19 mm/hr), which are considered to be economically unviable. Hence, an investigation was warranted of the strength and toughness behavior of NiAl-(Cr,Mo) directionally solidified at faster growth rates. If the mechanical properties did not deteriorate with increased growth rates, directional solidification could offer an economical means to produce NiAl-based alloys commercially for gas turbine engines. An investigation at the NASA Glenn

  4. Naturally Occurring Cr and Ni in the Sacramento Valley: II. Mn Oxides and the Mobility of Cr(VI) and Ni

    NASA Astrophysics Data System (ADS)

    Mills, C. T.; Morrison, J. M.; Goldhaber, M. B.; Foster, A. L.; Wolf, R. E.; Wanty, R. B.

    2007-12-01

    Soil manganese oxides can strongly affect the mobility and redox state of several toxic trace metals. We are studying the biogeochemical origin of Mn oxides and their association with Cr and Ni in soils of the Sacramento Valley, California. Both Cr and Ni are likely derived from ultramafic rocks that underlie Coast Range drainages to the west of the study area. The impact of weathering and erosion of these rocks is evident in the high levels of total Cr (80 to 1420 μg g-1) and nickel (65 to 224 μg g-1) that occur broadly in western Sacramento Valley soils. Although much of the Cr is bound in refractory spinels as Cr(III), some mobilization of Cr is apparent in the coincidence of enriched soils with high contents of Cr(VI) in ground water. Data from the National Water Information System (NWIS) shows 7 of 12 sampled wells within a 600 km2 area in the Sacramento Valley having Cr(VI) concentrations between 60 and 100% of the CA maximum contaminant level for drinking water (50 μg l-1). A 3-meter depth soil profile collected within the lower Putah Creek watershed was examined to investigate processes contributing to the oxidation and mobilization of natural Cr(III). Hydroxylamine hydrochloride-reducible Mn was determined for 8 depth intervals as a measure of manganese oxide occurrence. Concentrations of reducible Mn varied between 360 and 690 μg g-1 with depth and peaked at 2.7 m below the surface. Concentrations of anion exchangeable Cr(VI) were as high as 6 ng g-1 and were positively correlated (r2=0.59; p=0.07) with reducible Mn. Scanning electron microscopy of soil minerals from the 2.9 to 3.0 m interval showed Cr-bearing spinel grains enclosed within Mn oxide micro concretions suggesting a potential mechanism for the oxidation of natural Cr(III) to mobile Cr(VI). Consistent with the known tendency of Ni to sorb on Mn oxides, substantial Ni (13 to 45 μg g-1) was released in the reducible Mn fraction and it strongly correlates (r2=0.76; p=0.005) with reducible Mn

  5. Austenite precipitation during tempering in 16Cr-2Ni martensitic stainless steels

    SciTech Connect

    Balan, K.P.; Reddy, A.V.; Sarma, D.S.

    1998-09-04

    The 16Cr-2Ni steel when quenched from austenitizing temperature of 1,323K results in the formation of a complex microstructure consisting of the inherited {delta}-ferrite, martensite and retained austenite with a few undissolved M{sub 23}C{sub 6} carbides. There do not appear to be many reports on tempering behavior of 16Cr-2Ni steel through microstructural characterization using transmission electron microscopy. A comprehensive study is under progress to examine the structure-fracture-property relationship on 16Cr-2Ni steel and the microstructural changes that occur on tempering the steel are dealt with in this paper.

  6. Microstructure and strengthening of creep-tested cryomilled NiAl-AlN

    SciTech Connect

    Garg, A.; Whittenberger, J.D.; Luton, M.J.

    1997-12-31

    The B2 intermetallic NiAl is considered to be a prime candidate material for use as very high temperature structural components in gas turbine engines. The mechanical grinding of prealloyed NiAl powder in liquid nitrogen (cryomilling) results in an intermetallic matrix composite where micron sized particle free aluminide cores (grains) are surrounded by thin mantles comprised of nanometer sized AlN particles and NiAl grains. Under high temperature, slow strain rate conditions both compressive and tensile creep testing have shown that the mechanical strength of hot extruded cryomilled NiAl approaches the levels exhibited by advanced NiAl-based single crystals and simple Ni-based superalloys. Transmission electron microscopy of cryomilled materials tested between 1,100 and 1,300 K revealed little, if any, dislocation structure within the mantle regions, while the NiAl cores contained subgrains and dislocation networks after testing at all strain rates between 10{sup {minus}4} and 10{sup {minus}8} s{sup {minus}1}. These and other microstructural observations suggest that creep strength is the result of a fine NiAl grain/subgrain size, the inability of dislocations to move through the mantle and stabilization of the microstructure by the AlN particles.

  7. Effects of hydrogen absorption in TbNiAl and UNiAl

    SciTech Connect

    Bordallo, H.N.; Nakotte, H.; Schultz, A.; Kolomiets, A.V.; Havela, L.; Andreev, A.V.

    1998-12-31

    Although hydrides of intermetallic compounds are used extensively as hydrogen-storage media, little is known about the exact nature of metal-hydrogen interactions. However, this knowledge is of essential importance for the understanding of thermodynamics and other properties. Hydrides (deuterides) of TbNiAl and UNiAl have been widely studied because of drastic increase of magnetic ordering temperature under hydrogenation. Here the authors report neutron-diffraction results of the three deuterides, TbNiAlD{sub 1.28}, TbNiAlD{sub 0.8}a nd UNiAlD{sub 2.23}.

  8. Ultrahigh strength of dislocation-free Ni3Al nanocubes.

    PubMed

    Maaß, Robert; Meza, Lucas; Gan, Bin; Tin, Sammy; Greer, Julia R

    2012-06-25

    Individual Ni(3) Al nanocubes under pressure are investigated by comparing the compressive strength of both dislocation-free and irradiated Ni(3) Al nanocubes. The results are dicussed in light of the size-dependent and size-independent strength of face-centered cubic (fcc) nanocrystals in the framework of dislocation nucleation at free surfaces. This study sheds more light on the understanding of fundamental deformation mechanisms and size-affected strength in dislocation-free metallic nanocrystals. PMID:22454244

  9. Ni-Cr based dental alloys; Ni release, corrosion and biological evaluation.

    PubMed

    Reclaru, L; Unger, R E; Kirkpatrick, C J; Susz, C; Eschler, P-Y; Zuercher, M-H; Antoniac, I; Lüthy, H

    2012-08-01

    In the last years the dental alloy market has undergone dramatic changes for reasons of economy and biocompatibility. Nickel based alloys have become widely used substitute for the much more expensive precious metal alloys. In Europe the prevalence of nickel allergy is 10-15% for female adults and 1-3% for male adults. Despite the restrictions imposed by the EU for the protection of the general population in contact dermatitis, the use of Ni-Cr dental alloys is on the increase. Some questions have to be faced regarding the safety risk of nickel contained in dental alloys. We have collected based on many EU markets, 8 Ni-Cr dental alloys. Microstructure characterization, corrosion resistance (generalized, crevice and pitting) in saliva and the quantities of cations released in particular nickel and CrVI have been evaluated. We have applied non parametric classification tests (Kendall rank correlation) for all chemical results. Also cytotoxicity tests and an evaluation specific to TNF-alpha have been conducted. According to the obtained results, it was found that their behavior to corrosion was weak but that nickel release was high. The quantities of nickel released are higher than the limits imposed in the EU concerning contact with the skin or piercing. Surprisingly the biological tests did not show any cytotoxic effect on Hela and L929 cells or any change in TNF-alpha expression in monocytic cells. The alloys did not show any proinflammatory response in endothelial cells as demonstrated by the absence of ICAM-1 induction. We note therefore that there is really no direct relationship between the in vitro biological evaluation tests and the physico-chemical characterization of these dental alloys. Clinical and epidemiological studies are required to clarify these aspects. PMID:24364945

  10. Crack Free Tungsten Carbide Reinforced Ni(Cr) Layers obtained by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Amado, J. M.; Tobar, M. J.; Yáñez, A.; Amigó, V.; Candel, J. J.

    The development of hardfacing coatings has become technologically significant in many industries A common approach is the production of metal matrix composites (MMC) layers. In this work NiCr-WC MMC hardfacing layers are deposited on C25 steel by means of laser cladding. Spheroidal fused tungsten carbides is used as reinforcement phase. Three different NiCr alloys with different Cr content were tested. Optimum conditions to obtain dense, uniform carbide distribution and hardness close to nominal values were defined. The effect of Cr content respect to the microstructure, susceptibility for cracking and the wear rate of the resulting coating will also be discussed.

  11. Hydrogen permeation characteristics of some Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Van Deventer, E. H.; Maroni, V. A.

    1983-01-01

    Hydrogen permeation data are reported for two Fe-Cr-Al alloys, Type-405 SS (Cr 14-A1 0.2) and a member of the Fecralloy family of alloys (Cr 16-A1 5). The hydrogen permeability of each alloy (in a partially oxidized condition) was measured over a period of several weeks at randomly selected temperatures (between 150 and 850°C) and upstream H 2 pressures (between 2 and 1.5 × 10 4 Pa). The permeabilities showed considerable scatter with both time and temperature and were 10 2 to 10 3 times lower than those of pure iron, even in strongly reducing environments. The exponent, n, for the relationship between upstream H 2 pressure, P, and permeability, φ, ( φ ~ Pn) was closer to 0.7 than to the expected 0.5, indicating a process limited by surface effects (e.g., surface oxide films) as opposed to bulk material effects. Comparison of these results with prior permeation measurements on other Fe-Cr-Al alloys, on Fe-Cr alloys, and on pure iron shows that the presence of a few weight percent aluminum offers the best prospects for achieving low tritium permeabilities with martensitic and ferritic steels used in fusion-reactor first wall and blanket applications.

  12. High Temperature Behavior of Cr3C2-NiCr Coatings in the Actual Coal-Fired Boiler Environment

    NASA Astrophysics Data System (ADS)

    Bhatia, Rakesh; Sidhu, Hazoor Singh; Sidhu, Buta Singh

    2015-03-01

    Erosion-corrosion is a serious problem observed in steam-powered electricity generation plants, and industrial waste incinerators. In the present study, four compositions of Cr3C2-(Ni-20Cr) alloy coating powder were deposited by high-velocity oxy-fuel spray technique on T-91 boiler tube steel. The cyclic studies were performed in a coal-fired boiler at 1123 K ± 10 K (850 °C ± 10 °C). X-ray diffraction, scanning electron microscopy/energy dispersive X-ray analysis and elemental mapping analysis techniques were used to analyze the corrosion products. All the coatings deposited on T-91 boiler tube steel imparted hot corrosion resistance. The 65 pctCr3C2 -35 pct (Ni-20Cr)-coated T-91 steel sample performed better than all other coated samples in the given environment.

  13. Researching for Corrosion-Resistance Performance of Laser-Hybrid Plasma Spraying NiCr-Cr3C2 Coating

    NASA Astrophysics Data System (ADS)

    Li, Shu-qing; Li, Qi-lian; Gong, Shui-li; Wang, Chun

    In this paper, the NiCr-Cr3C2 coating was prepared by laser-hybrid plasma spraying (LHPS)technology, the NSS (Neutral Salt Spraying) test results showed that the LHPS NiCr-Cr3C2 coating had good corrosion-resistance performance comparing with the base material and the APS (air plasma spraying) coating. A SEM (scanning electron microscope) was used to analyze corrosion morphology of the samples, The LHPS coating overcame many shortcomings of the conventional spraying coatings such as poor bonding strength, many porosities, many cracks and so on. LHPS is able to improve the bonding strength as the interfaces are melted and joined by the laser simultaneously with plasma spraying. The coating achieves metallurgy bonding and its microstructure becomes more compact and therefore its corrosion-resistance performance is greatly improved.

  14. Alloying of cold-sprayed Al Ni composite coatings by post-annealing

    NASA Astrophysics Data System (ADS)

    Lee, Ha Yong; Jung, Se Hun; Lee, Soo Yong; Ko, Kyung Hyun

    2007-01-01

    A new cold spray coating technique for thick Al coating with finely dispersed Al-Ni intermetallic compounds was tested. For easy powder preparation and high yield, rather than using of Al/compound mixture feed stock, the spraying of pure Al and Ni powders mixture followed by post-annealing was suggested. The powder composition of Al and Ni was 75:25, and 90:10 (wt.%) to expect full consumption of pure Ni into intermetallic compounds. After Al-Ni composite coatings, the Ni particles were finely dispersed and embedded in the Al matrix with a good coating yield. Above 450 °C of post-annealing temperature, the Al 3Ni and Al 3Ni 2 phases were observed in the cold-sprayed Al-Ni coatings. The Ni particles in the Al matrix were fully consumed via compounding reaction with Al at 550 °C of the annealing temperature.

  15. Physicochemical investigation of NiAl with small molybdenum additions

    NASA Technical Reports Server (NTRS)

    Troshkina, V. A.; Kucherenko, L. A.; Fadeeva, V. I.; Aristova, N. M.

    1982-01-01

    Specimens of four cast NiAl alloys, three of them containing 0.5, 1.0 and 1.5 at. % Mo., were homogenized for 10, 10, and 140 hr at 1373, 1523 and 1273 K, respectively, then kept at 1073, 1173 and 1323 K for 60, 120 and 3 hr, respectively, and quenched in icy water. The precipitation of a metastable Ni3Mo phase was observed at temperatures between 1073 and 1523 K. Molybdenum substituted for nickel was found to inhibit the lattice disordering in NiAl at 1073 and 1523 K.

  16. Electrochemical Testing of Ni-Cr-Mo-Gd Alloys

    SciTech Connect

    T. E. Lister; R. E. Mizia; H. Tian

    2005-10-01

    The waste package site recommendation design specified a boron-containing stainless steel, Neutronit 976/978, for fabrication of the internal baskets that will be used as a corrosion-resistant neutron-absorbing material. Recent corrosion test results gave higher-than-expected corrosion rates for this material. The material callout for these components has been changed to a Ni-Cr-Mo-Gd alloy (ASTM-B 932-04, UNS N06464) that is being developed at the Idaho National Laboratory. This report discusses the results of initial corrosion testing of this material in simulated in-package environments that could contact the fuel baskets after breach of the waste package outer barrier. The corrosion test matrix was executed using the potentiodynamic and potentiostatic electrochemical test techniques. The alloy performance shows low rates of general corrosion after initial removal of a gadolinium-rich second phase that intersects the surface. The high halide-containing test solutions exhibited greater tendencies toward initiation of crevice corrosion.

  17. Analysis of NiAlTa precipitates in beta-NiAl + 2 at. pct Ta alloy

    NASA Technical Reports Server (NTRS)

    Pathare, V.; Michal, G. M.; Vedula, K.; Nathal, M. V.

    1987-01-01

    Results are reported from experiments performed to identify the precipitates, and their orientation in the matrix, in a beta-NiAl alloy containing 2 at. pct. Ta after undergoing creep test at 1300 K. Test specimens formed by extruding hot powders were compressed at 1300 K for about 50 hr at a strain rate averaging 6/1 million per sec. The specimens were then thinned and examined under an electron microscope and by X-ray diffractometry. An intermetallic NiAlTa compound with a hexagonal Cl4 structure appeared as second phase precipitates in the samples, exhibiting plate-like shapes and a habit plane close to (012). The prism planes of the hexagonal NiAlTa precipitates paralleled the closest packed planes in the cubic beta-NiAl matrix.

  18. Structure, stability and magnetic properties of (NiAl)n(n≤6) clusters

    NASA Astrophysics Data System (ADS)

    Wen, Jun-Qing; Zhang, Jian-Min; Chen, Guo-Xiang; Zhang, Xiao-Zhen; Wen, Zhen-Yi

    2016-09-01

    In this paper, density functional theory with generalized gradient approximation (GGA) for the exchange-correlation potential has been used to calculate the energetically global-minimum geometries and electronic states of (NiAl)n(n≤6) clusters. Full structural optimizations, analysis of energy and frequency calculation are performed. The most stable structures of (NiAl)n clusters are all three-dimensional structures except NiAl. The average bond lengths of (NiAl)n clusters are larger than that of Ni2n, and are smaller than that of Al2n. The binding energy per atom of Ni2n and (NiAl)n has the same change trend, and that are larger than that of Al2n. Stability analysis shows that Ni8, (NiAl)2 and Al10 clusters have higher relative stability than other clusters. Mulliken analysis indicates that charges always transfer from Al atoms to Ni atoms, and the average charges of transfer from Al atoms to Ni atoms have a maximum at (NiAl)6, implying the strong interaction between Al and Ni atoms in (NiAl)6. The average atomic magnetic moments of (NiAl)n are smaller than that of true Ni2n. The analysis of the static polarizability shows that the electronic structures of (NiAl)n clusters tend to be compact with the increase of atoms.

  19. Hybrid Al + Al3Ni metallic foams synthesized in situ via laser engineered net shaping

    NASA Astrophysics Data System (ADS)

    Zheng, Baolong; Li, Ying; Smugeresky, John E.; Zhou, Yizhang; Baker, Dean; Lavernia, Enrique J.

    2011-09-01

    A hybrid, Al + Al3Ni metallic foam was synthesized in situ via laser engineered net shaping (LENS®) of Ni-coated 6061 Al powder in the absence of a foaming agent. During LENS® processing, the Ni coating reacted with the Al matrix, resulting in the simultaneous formation of a fine dispersion of Al3Ni, and a high volume fraction of porosity. As a reinforcement phase, the intermetallic compound formed particles with a size range of 1-5 µm and a volume fraction of 63%, with accompanying 35-300 µm pores with a 60% volume fraction. The microstructure of the as-deposited Al + Al3Ni composite foams was characterized using SEM, EDS, XRD and TEM/HRTEM techniques. The evolution of the microstructure was analyzed on the basis of the thermal field present during deposition, paying particular attention to the thermodynamics of the Al3Ni intermetallic compound formation as well as discussing the mechanisms that may be responsible for the observed porosity. The mechanical behavior of the as-deposited material was characterized using compression and microhardness testing, indicating that the yield strength and hardness are 190 MPa and 320 HV, respectively, which represents an increase of over three times higher than that of annealed Al6061, or similar to heat-treated Al6061 fully dense matrix, and much higher than those of traditional Al alloy foams, and with a low density of 1.64 g/m3.

  20. Anti-wear properties of Cr C and Ni Co alloy coatings as substitutes for conventional nanocrystalline Cr coatings

    NASA Astrophysics Data System (ADS)

    Zeng, Zhixiang; Zhang, Junyan

    2008-09-01

    Nanocrystalline Ni-Co, amorphous Cr-C alloy and nanocrystalline Cr-C coatings were electrodeposited from 'environmentally acceptable' electrolytes as potential substitutes for conventional nanocrystalline Cr coatings electrodeposited from noxious hexavalent chromium. The structure, morphology and hardness of coatings are investigated using a transmission electron microscope, a scanning electronic microscope and a Vickers hardness tester, respectively. Anti-wear properties are tested on a pin-on-plate vibrant wear tester. The correlation between the wear resistance, hardness, brittleness and the lubricated state is investigated. The results show that the wear behaviour of specimens significantly depends on their lubricated state, hardness and brittleness. Under the lubricated sliding condition, abrasive wear is the primary wear mechanism for all specimens. With respect to the abrasive wear mechanism, both the elastic and plastic deformations play important roles during the lubricated sliding process. Thus, the amorphous and nanocrystalline Cr-C alloy coatings, with both high brittleness and high hardness, exhibit a lower wear rate than the conventional Cr and Ni-Co coatings. On the other hand, under the dry sliding condition, the annealed Ni-Co coating, with an excellent compromise between high hardness and toughness, exhibits an abrasive wear mechanism and a relatively low wear rate; in contrast, the brittle Cr-matrix coatings exhibit a severe fatigue/delamination wear mechanism and high wear rate.

  1. Surface Modification of Cr3C2-NiCr Cermet Coatings by Direct Diode Laser Remelting Process

    NASA Astrophysics Data System (ADS)

    Abe, Nobuyuki; Morimoto, Junji; Fukuhra, Shinji; Yamada, Katsuhiro; Tsukamoto, Masahiro

    Thermal spraying technology has been used for the improvement of wear resistance, erosion resistance, heat resistance and corrosion resistance. Corrosion, wear and abrasion resistance of the substrate materials were significantly improved by the paint coatings. These organic paint coatings, however, did not endure high temperatures and did not adhere well. Modern high performance machinery parts subjected to the extremes of temperature and mechanical stress, needs surface protection against high temperature corrosive media, and mechanical wear and tear. Chromium carbide based materials are commonly used for high temperature wear applications. In this study, we treated Cr3C2-NiCr coatings by laser irradiation treatment and examined its hardness in comparison with that formed by HVOF process. Consequently, the average hardness of laser irradiated Cr3C2-NiCr coating was found out to be higher than that of HVOF coating. The laser-treated Cr3C2-35%NiCr coating further improved the solid particle erosion resistance by a factor of almost twice.

  2. NiAl-Based Approach For Rocket Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Nathal, Michael V. (Inventor); Gayda, John (Inventor); Noebe, Ronald D. (Inventor)

    2005-01-01

    A multi-layered component, such as a rocket engine combustion chamber, includes NiAl or NiAl-based alloy as a structural layer on the hot side of the component. A second structural layer is formed of material selected form Ni-based superalloys, Co-based alloys, Fe-based alloys, Cu, and Cu-based alloys. The second material is more ductile than the NiAl and imparts increased toughness to the component. The second material is selected to enhance one or more predetermined physical properties of the component. Additional structural layers may be included with the additional material(s) being selected for their impact on physical properties of the component.

  3. NiAl-based approach for rocket combustion chambers

    NASA Technical Reports Server (NTRS)

    Nathal, Michael V. (Inventor); Gayda, John (Inventor); Noebe, Ronald D. (Inventor)

    2005-01-01

    A multi-layered component, such as a rocket engine combustion chamber, includes NiAl or NiAl-based alloy as a structural layer on the hot side of the component. A second structural layer is formed of material selected from Ni-based superalloys, Co-based alloys, Fe-based alloys, Cu, and Cu-based alloys. The second material is more ductile than the NiAl and imparts increased toughness to the component. The second material is selected to enhance one or more predetermined physical properties of the component. Additional structural layers may be included with the additional material(s) being selected for their impact on physical properties of the component.

  4. Atomistic Simulations of Ti Additions to NiAl

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Garg, Anita; Ferrante, John; Amador, Carlos

    1997-01-01

    The development of more efficient engines and power plants for future supersonic transports depends on the advancement of new high-temperature materials with temperature capabilities exceeding those of Ni-based superalloys. Having theoretical modelling techniques to aid in the design of these alloys would greatly facilitate this development. The present paper discusses a successful attempt to correlate theoretical predictions of alloy properties with experimental confirmation for ternary NiAl-Ti alloys. The B.F.S. (Bozzolo-Ferrante-Smith) method for alloys is used to predict the solubility limit and site preference energies for Ti additions of 1 to 25 at.% to NiAl. The results show the solubility limit to be around 5% Ti, above which the formation of Heusler precipitates is favored. These results were confirmed by transmission electron microscopy performed on a series of NiAl-Ti alloys.

  5. Atomistic simulations of Ti additions to NiAl

    SciTech Connect

    Bozzolo, G.; Noebe, R.D.; Garg, A.; Ferrante, J.; Amador, C.

    1997-12-31

    The development of more efficient engines and power plants for future supersonic transports depend on the advancement of new high-temperature materials with temperature capabilities exceeding those of Ni-based superalloys. Having theoretical modelling techniques to aid in the design of these alloys would greatly facilitate this development. The present paper discusses a successful attempt to correlate theoretical predictions of alloy properties with experimental confirmation for ternary NiAl-Ti alloys. The B.F.S. (Bozzolo- Ferrante-Smith) method for alloys is used to predict the solubility limit and site preference energies for Ti additions of 1 to 25 at. % to NiAl. The results show the solubility limit to be around 5% Ti, above which the formation of Heusler precipitates is favored. These results were confirmed by transmission electron microscopy performed on a series of NiAl-Ti alloys.

  6. Reliability analysis of single crystal NiAl turbine blades

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan; Noebe, Ronald; Wheeler, Donald R.; Holland, Fred; Palko, Joseph; Duffy, Stephen; Wright, P. Kennard

    1995-01-01

    As part of a co-operative agreement with General Electric Aircraft Engines (GEAE), NASA LeRC is modifying and validating the Ceramic Analysis and Reliability Evaluation of Structures algorithm for use in design of components made of high strength NiAl based intermetallic materials. NiAl single crystal alloys are being actively investigated by GEAE as a replacement for Ni-based single crystal superalloys for use in high pressure turbine blades and vanes. The driving force for this research lies in the numerous property advantages offered by NiAl alloys over their superalloy counterparts. These include a reduction of density by as much as a third without significantly sacrificing strength, higher melting point, greater thermal conductivity, better oxidation resistance, and a better response to thermal barrier coatings. The current drawback to high strength NiAl single crystals is their limited ductility. Consequently, significant efforts including the work agreement with GEAE are underway to develop testing and design methodologies for these materials. The approach to validation and component analysis involves the following steps: determination of the statistical nature and source of fracture in a high strength, NiAl single crystal turbine blade material; measurement of the failure strength envelope of the material; coding of statistically based reliability models; verification of the code and model; and modeling of turbine blades and vanes for rig testing.

  7. High temperature deformation of NiAl and CoAl

    NASA Technical Reports Server (NTRS)

    Nix, W. D.

    1982-01-01

    The high temperature mechanical properties of the aluminides are reviewed with respect to their potential as high temperature structural materials. It is shown that NiAl and CoAl are substantially stronger than the pure metals Ni and Co at high temperatures and approach the strength of some superalloys, particularly when those superalloys are tested in "weak" directions. The factors that limit and control the high temperature strengths of NiAl and CoAl are examined to provide a basis for the development of intermetallic alloys of this type.

  8. PVD synthesis and high-throughput property characterization of NiFeCr alloy libraries

    SciTech Connect

    Rar, A.; Frafjord, J. J.; Fowlkes, Jason D.; Specht, E. D.; Rack, P. D.; Santella, M. L.; Bei, H.; George, E. P.; Pharr, G. M.

    2004-12-16

    Three methods of alloy library synthesis, thick-layer deposition followed by interdiffusion, composition-spread codeposition and electron-beam melting of thick deposited layers, have been applied to Ni-Fe-Cr ternary and Ni-Cr binary alloys. Structural XRD mapping and mechanical characterization by means of nanoindentation have been used to characterize the properties of the libraries. The library synthesis methods are compared from the point of view of the structural and mechanical information they can provide.

  9. Heat treatment of NiCrFe alloy 600 to optimize resistance to intergranular stress corrosion

    DOEpatents

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

    A process of producing a NiCrFe alloy having a high resistance to stress corrosion cracking comprises heating a NiCrFe alloy to a temperature sufficient to enable the carbon present in the alloy body in the form of carbide deposits to enter into solution, rapidly cooling the alloy body, and heating the cooled body to a temperature between 1100 to 1500/sup 0/F for about 1 to 30 hours.

  10. Heat treatment of NiCrFe alloy to optimize resistance to intergrannular stress corrosion

    DOEpatents

    Steeves, Arthur F.; Bibb, Albert E.

    1984-01-01

    A process of producing a NiCrFe alloy having a high resistance to stress corrosion cracking comprising heating a NiCrFe alloy to a temperature sufficient to enable the carbon present in the alloy body in the form of carbide deposits to enter into solution, rapidly cool the alloy body, and heat the cooled body to a temperature between 1100.degree. to 1500.degree. F. for about 1 to 30 hours.

  11. Degradation behavior of Ni3Al plasma-sprayed boiler tube steels in an energy generation system

    NASA Astrophysics Data System (ADS)

    Sidhu, Buta Singh; Prakash, S.

    2005-06-01

    Boiler steels, namely, low-C steel, ASTM-SA210-Grade A1 (GrA1), 1Cr-0.5Mo steel, ASTM-SA213-T-11 (T11) and 2.25Cr-1Mo steel, ASTM-SA213-T-22 (T22) were plasma sprayed with Ni3Al. The alloy powder was prepared by mixing Ni and Al in the stoichiometric ratio of 3 to 1. The Ni-22Cr-10Al-1Y alloy powder was used as a bond coat, with a 150 µm thick layer sprayed onto the surface before applying the 200 µm coating of Ni3Al. Exposure studies have been performed in the platen superheater zone of a coal-fired boiler at around 755 °C for 10 cycles, each of 100 h duration. The protection to the base steel was minimal for the three steels. Scale spallation and the formation of a porous and nonadherent NiO scale were probably the main reasons for the lack of protection. In the case of T22-coated steel, cracks in the coatings have been observed after the first 100 h exposure cycle.

  12. Dynamic oxidation behavior of TD-NiCr alloy with different surface pretreatments

    NASA Technical Reports Server (NTRS)

    Young, C. T.; Tenney, D. R.; Herring, H. W.

    1975-01-01

    Oxidation tests of TD-NiCr alloy with different surface pretreatments were conducted in a Mach-5 arc-jet at 1200 C and 0.002 lb/sec flowing air environment. The mechanisms responsible for the observed oxidation behavior are examined. The presence of atomic oxygen in the air stream plays a significant role in determining the oxidation characteristic of the alloy. The rate of Cr2O3 vaporization by formation of volatile CrO3 is greatly enhanced by the flowing conditions. The typical microstructure of oxides formed in the dynamic tests consists of an external layer of NiO with a porous mushroom-type morphology, an intermediate layer of NiO and Cr2O3 oxide mixture, and a continuous inner layer of Cr2O3 in contact with the Cr-depleted alloy substrate. Three basic processes underlying the formation of mushroom-type NiO are identified and discussed. The oxidation rate is determined by the rate of vaporization of NiO. Surface pretreatment has a significant effect on the oxidation behavior of the alloy in the early stage of oxidation, but becomes less important as exposure time increases. Mechanical polishing induces surface recrystallization, but promotes the concurrence of external growth of NiO and internal oxidation of the alloy in the dynamic atmosphere.

  13. High-Power Diode Laser-Treated 13Cr4Ni Stainless Steel for Hydro Turbines

    NASA Astrophysics Data System (ADS)

    Mann, B. S.

    2014-06-01

    The cast martensitic chromium nickel stainless steels such as 13Cr4Ni, 16Cr5Ni, and 17Cr4Ni PH have found wide application in hydro turbines. These steels have adequate corrosion resistance with good mechanical properties because of chromium content of more than 12%. The 13Cr4Ni stainless steel is most widely used among these steels; however, lacks silt, cavitation, and water impingement erosion resistances (SER, CER, and WIER). This article deals with characterizing 13Cr4Ni stainless steel for silt, cavitation, and water impingement erosion; and studying its improved SER, CER, and WIER behavior after high-power diode laser (HPDL) surface treatment. The WIER and CER have improved significantly after laser treatment, whereas there is a marginal improvement in SER. The main reason for improved WIER and CER is due to its increased surface hardness and formation of fine-grained microstructure after HPDL surface treatment. CER and WIER of HPDL-treated 13Cr4Ni stainless steel samples have been evaluated as per ASTM G32-2003 and ASTM G73-1978, respectively; and these were correlated with microstructure and mechanical properties such as ultimate tensile strength, modified ultimate resilience, and microhardness. The erosion damage mechanism, compared on the basis of scanning electron micrographs and mechanical properties, is discussed and reported in this article.

  14. Response of Pistia stratiotes to heavy metals (Cr, Ni, and Zn) and phosphorous.

    PubMed

    Mufarrege, M M; Hadad, H R; Maine, M A

    2010-01-01

    The effects of Cr, Ni, Zn, and P exposure on the root anatomic structure, growth, and chlorophyll a concentration of Pistia stratiotes L. were studied. Plastic aquaria containing 50 g of wet plants and 5 L of pond water added with the contaminant(s) were disposed. The treatments were: (1) Cr, (2) Ni, (3) Zn, (4) P, (5) Cr + Ni + Zn, (6) Cr + Ni + Zn + P, and (7) control. Contaminant additions were done seven times. In each addition, concentrations of 1 mg of metals or 5 mg of P per liter of water were added. Chlorophyll a was an indicator more sensitive to Zn and Cr toxicity than the relative growth rate. Ni and Cr + Ni + Zn treatments were the most toxic ones, in which biomass and the root anatomical parameters (root length, cross-sectional areas [CSAs] of root, stele, and metaxylem vessels) decreased significantly. The addition of P to the treatment with combined metals attenuated the decrease in plant growth and root length, and caused a significant increase in CSAs of total metaxylem vessels, suggesting that P increased the tolerance of P. stratiotes to metals. This fact has important implications for the use of this macrophyte in constructed wetlands for industrial wastewater treatment. PMID:19506937

  15. Temporal evolution of ion energy distribution functions and ion charge states of Cr and Cr-Al pulsed arc plasmas

    SciTech Connect

    Tanaka, Koichi; Anders, André

    2015-11-15

    To study the temporal evolution of ion energy distribution functions, charge-state-resolved ion energy distribution functions of pulsed arc plasmas from Cr and Cr-Al cathodes were recorded with high time resolution by using direct data acquisition from a combined energy and mass analyzer. The authors find increases in intensities of singly charged ions, which is evidence that charge exchange reactions took place in both Cr and Cr-Al systems. In Cr-Al plasmas, the distributions of high-charge-state ions exhibit high energy tails 50 μs after discharge ignition, but no such tails were observed at 500 μs. The energy ratios of ions of different charge states at the beginning of the pulse, when less neutral atoms were in the space in front of the cathode, suggest that ions are accelerated by an electric field. The situation is not so clear after 50 μs due to particle collisions. The initial mean ion charge state of Cr was about the same in Cr and in Cr-Al plasmas, but it decreased more rapidly in Cr-Al plasmas compared to the decay in Cr plasma. The faster decay of the mean ion charge state and ion energy caused by the addition of Al into a pure Cr cathode suggests that the mean ion charge state is determined not only by ionization processes at the cathode spot but also by inelastic collision between different elements.

  16. Corrosion Behavior of Al-Al3Ni and Al-Al2Cu Functionally Graded Materials Fabricated by a Centrifugal Method

    NASA Astrophysics Data System (ADS)

    Noda, Kazuhiko; Miyahara, Keita; Watanabe, Yoshimi

    2008-02-01

    Intermetallic compounds, such as Al3Ni and Al2Cu, are effective for enhancing the mechanical properties of an alloy. Al-Al3Ni and Al-Al2Cu functionally graded materials (FGMs) might be attractive materials for advanced materials. Al-Al3Ni and Al-Al2Cu FGMs were fabricated by a centrifugal method; the centrifugal method is an extremely effective method for fabricating FGMs. Al-Al3Ni and Al-Al2Cu FGMs that had a graded distribution of intermetallic compounds could be produced by this in-situ centrifugal method. Particle size, particle shape and the distribution of intermetallic compounds were controlled by varying the content of the alloy element (Ni, Cu) in the master alloy, the cooling rate in casting and the gravity number. The casting mechanism is explained in terms of the microstructures of the Al-Al3Ni and Al-Al2Cu FGMs fabricated by this method. The corrosion behavior of the FGMs was investigated by electrochemical analysis. Polarization curves of the FGMs in a borate solution were measured by a potentiodynamic method. The presence of Al2Cu exerted a larger effect on the corrosion behavior of the FGMs than Al3Ni. Analysis of the polarization curve parameters was effective for evaluating the corrosion resistance of the FGMs.

  17. Equilibrium point defects in intermetallics with the [ital B]2 structure: NiAl and FeAl

    SciTech Connect

    Fu, C.L.; Ye, Y.; Yoo, M.H. ); Ho, K.M. )

    1993-09-01

    Equilibrium point defects and their relation to the contrasting mechanical behavior of NiAl and FeAl are investigated. For NiAl, the defect structure is dominated by two types of defects---monovacancies on the Ni sites and substitutional antisite defects on the Al sites. The defect structure of FeAl differs from that of NiAl in the occurrence of antisite defects at the transition-metal sites for Al-rich alloys and the tendency for vacancy clustering. The strong ordering (and brittleness) of NiAl is attributed mainly to the difference in atomic size between constituent atoms.

  18. Phase Separation kinetics in an Fe-Cr-Al alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Chao, J.

    2012-01-01

    The {alpha}-{alpha}{prime} phase separation kinetics in a commercial Fe-20 wt.% Cr-6 wt.% Al oxide dispersion-strengthened PM 2000{trademark} steel have been characterized with the complementary techniques atom probe tomography and thermoelectric power measurements during isothermal aging at 673, 708, and 748 K for times up to 3600 h. A progressive decrease in the Al content of the Cr-rich {alpha}{prime} phase was observed at 708 and 748 K with increasing time, but no partitioning was observed at 673 K. The variation in the volume fraction of the {alpha}{prime} phase well inside the coarsening regime, along with the Avrami exponent 1.2 and activation energy 264 kJ mol{sup -1}, obtained after fitting the experimental results to an Austin-Rickett type equation, indicates that phase separation in PM 2000{trademark} is a transient coarsening process with overlapping nucleation, growth, and coarsening stages.

  19. Microstructural Investigations On Ni-Ta-Al Ternary Alloys

    SciTech Connect

    Negache, M.; Souami, N.

    2010-01-05

    The Ni-Al-Ta ternary alloys in the Ni-rich part present complex microstructures. They are composed of multiple phases that are formed according to the nominal composition of the alloy, primary Ni(gamma), Ni{sub 3}Al(gamma'), Ni{sub 6}AlTa(tau{sub 3}), Ni{sub 3}Ta(delta) or in equilibrium: two solid phases (gamma'-tau{sub 3}), (tau{sub 3}-delta), (tau{sub 3}-gamma), (gamma-delta) or three solid phases (gamma'-tau{sub 3}-delta). The nature and the volume fraction of these phases give these alloys very interesting properties at high temperature, and this makes them attractive for specific applications. We have developed a series of ternary alloys in electric arc furnace, determining their solidification sequences using Differential Thermal Analysis (DTA), characterized by SEM-EDS, X-ray diffraction and by a microhardness tests. The follow-up results made it possible to make a correlation between the nature of the formed phases and their solidifying way into the Ni{sub 75}Al{sub x}Ta{sub y} (x+y = 25at.%) system, which are varied and complex. In addition to the solid solution Ni (gamma), the formed intermetallics compounds (gamma', tau{sub 3} and delta) has been identified and correlated with a complex balance between phases.We noticed that the hardness increases with the tantalum which has a hardening effect and though the compound Ni{sub 3}Ta(delta) is the hardest. The below results provide a better understanding of the complex microstructure of these alloys.

  20. A comparison of the bonding in Cr(NO)4 and Ni(CO)4

    NASA Technical Reports Server (NTRS)

    Bauschlicher, C. W., Jr.; Siegbahn, P. E. M.

    1986-01-01

    The bonding in Cr(NO)4 is very ionic, with about 1.5 electrons donated from the Cr to the NO 2pi orbitals. There is also a NO sigma donation of about 0.5 electrons to the Cr, yielding a net charge of Cr of about 1. A large MCSCF expansion is needed to describe both the ionic and covalent contributions to the Cr 3d-NO 2pi bonding. This bonding is compared to that in the isoelectronic Ni(CO)4.

  1. A comparison of the bonding in Cr(NO)4 and Ni(CO)4

    NASA Astrophysics Data System (ADS)

    Bauschlicher, Charles W., Jr.; Siegbahn, Per E. M.

    1986-09-01

    The bonding in Cr(NO)4 is very ionic, with about 1.5 electrons donated from the Cr to the NO 2π orbitals. There is also a NO σ donation of about 0.5 electrons to the Cr, yielding a net charge on Cr of about 1. A large MCSCF expansion is needed to describe both the ionic and covalent contributions to the Cr 3d-NO 2π bonding. This bonding is compared to that in the isoelectronic Ni(CO)4.

  2. Initial evaluation of continuous fiber reinforced NiAl composites

    NASA Technical Reports Server (NTRS)

    Noebe, R. D.; Bowman, R. R.; Eldridge, J. I.

    1990-01-01

    NiAl is being evaluated as a potential matrix material as part of an overall program to develop and understand high-temperature structural composites. Currently, continuous fiber composites have been fabricated by the powder cloth technique incorporating either W(218) or single crystal Al2O3 fibers as reinforcements in both binary NiAl and a solute strengthened NiAl(.05 at. pct Zr) matrix. Initial evaluation of these composite systems have included: fiber push-out testing to measure matrix/fiber bond strengths, bend testing to determine strength as a function of temperature and composite structure, and thermal cycling to establish the effect of matrix and fiber properties on composite life. The effect of matrix/fiber bond strength and matrix strength on several composite properties will be discussed.

  3. Thermomechanical Processing and Roll Bonding of Tri-Layered Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn Composite

    NASA Astrophysics Data System (ADS)

    Kim, Hobyung; Kang, Gyeong Tae; Hong, Sun Ig

    2016-05-01

    Tri-layered Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn composite was processed by roll bonding and the effect of thermomechanical processing on the mechanical performance and electrical conductivity was studied. Roll-bonded composite exhibited the brief work hardening and subsequent rapid work softening because of the high stored deformation energy, leading to failure at the plastic strain of 8 to 10 pct. The mechanical instability of as-roll-bonded composites was abated by heat treatment (HT) at 723 K (450 °C) and the extended work hardening with enhanced ductility compared to that of the as-roll-bonded composites was observed after HT. The strength and electrical conductivity of clad composite is dependent on the precipitation strengthening of Cu-Cr and recovery softening of Cu-Ni-Zn during post-roll-bonding HT. The increase of roll-bonding temperature enhances the precipitation kinetics and it takes shorter time to reach maximum hardness in Cu-Cr layer during post-roll-bonding HT. The toughness of as-roll-bonded Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn clad composite at 773 K (500 °C) [42 MJ/mm3] is greater than those at 723 K (450 °C) [24 MJ/mm3] and 823 K (550 °C) [38 MJ/mm3]. The maximum toughness [100 MJ/mm3] with the electrical conductivity of 68 pct IACS was obtained in the Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn clad composite roll-bonded at 773 K (500 °C) and subsequently heat-treated at 723 K (450 °C).

  4. Ring head recording on perpendicular media: Output spectra for CoCr and CoCr/NiFe media

    NASA Astrophysics Data System (ADS)

    Stubbs, D. P.; Whisler, J. W.; Moe, C. D.; Skorjanec, J.

    1985-04-01

    The recording density response for sputtered CoCr (thickness=0.5 μm) and CoCr/NiFe (t=0.25 μm/0.5 μm) as well as evaporated CoNi (t=0.12 μm) and Co surface-doped iron oxide particulate media has been measured by reading and writing with Mn-Zn ferrite heads (gap length=0.375 μm, track width=37 μm) in contact with the media. Measurements to 200 kfc/i (thousand flux changes per inch) show a gap null around 115 kfc/i. The data have been normalized by dividing out the head sensitivity to obtain the value of spacing plus transition width (d+a) for the various media. For the CoCr media this value varied from 0.075-0.088 μm; for CoNi, 0.100 μm, and for the particulate medium, 0.163 μm. In addition, testing with a larger gapped Mn-Zn ferrite head (g=2.43 μm) shows that the head fields are distorted by the soft magnetic underlayer in dual layer CoCr/NiFe samples when the gap length is large compared to the distance to the underlayer.

  5. Recent advances in alloy design of Ni{sub 3}Al alloys for structural use

    SciTech Connect

    Liu, C.T.; George, E.P.

    1996-12-31

    This is a comprehensive review of recent advances in R&D of Ni{sub 3}Al-based alloys for structural use at elevated temperatures in hostile environments. Recent studies indicate that polycrystalline Ni{sub 3}Al is intrinsically quite ductile at ambient temperatures, and its poor tensile ductility and brittle grain-boundary fracture are caused mainly by moisture-induced hydrogen embrittlement when the aluminide is tested in moisture- or hydrogen-containing environments. Tensile ductility is improved by alloying with substitutional and interstitial elements. Among these additives, B is most effective in suppressing environmental embrittlement and enhancing grain-boundary cohesion, resulting in a dramatic increase of tensile ductility at room temperature. Both B-doped and B-free Ni{sub 3}Al alloys exhibit brittle intergranular fracture and low ductility at intermediate temperatures (300-850 C) because of oxygen-induced embrittlement in oxidizing environments. Cr is found to be most effective in alleviating elevated-temperature embrittlement. Parallel efforts on alloy development using physical metallurgy principles have led to development of several Ni{sub 3}Al alloys for industrial use. The unique properties of these alloys are briefly discussed. 56 refs, 15 figs, 3 tabs.

  6. Two-Phase (TiAl+TiCrAl) Coating Alloys for Titanium Aluminides

    NASA Technical Reports Server (NTRS)

    Brady, Michael P. (Inventor); Smialek, James L. (Inventor); Brindley, William J. (Inventor)

    1998-01-01

    A coating for protecting titanium aluminide alloys, including the TiAl gamma + Ti3Al (alpha(sub 2)) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C. is disclosed. This protective coating consists essentially of titanium, aluminum. and chromium in the following approximate atomic ratio: Ti(41.5-34.5)Al(49-53)Cr(9.5-12.5)

  7. Structure and wear behavior of AlCrSiN-based coatings

    NASA Astrophysics Data System (ADS)

    Chen, Yun; Du, Hao; Chen, Ming; Yang, Jun; Xiong, Ji; Zhao, Haibo

    2016-05-01

    AlCrN, AlCrSiCN, AlCrSiN/MoN, and AlCrSiN/NbN coatings have been deposited on high-polished WC-Co cemented carbide substrate and tools by mid-frequency magnetron sputtering in Ar/N2 mixtures. Al0.6Cr0.4, Al0.6Cr0.3Si0.1, and C/Mo/Nb targets were used during the deposition. The microstructure and mechanical properties of as-deposited coatings were investigated. Investigations of the wear behaviors of coated tools were also performed. The results showed that cubic structure was formed in the coatings. Broader CrAlN (1 1 1) and (2 0 0) peaks without SiNx peak were formed in the AlCrSiN/MexN coatings, which showed a nanocomposited structure. Meanwhile, according to SEM micrographs, AlCrN exhibited a columnar structure, while, AlCrSiCN, AlCrSiN/MoN, and AlCrSiN/NbN coatings showed nanocrystalline morphology. The nano-multilayered coatings performed higher hardness, H/E, and H3/E2 ratios compared with AlCrN coating. Through the Rockwell adhesion test, all the coatings exhibited adhesion strength quality HF1. After turning Inconel 718 under dry condition, the nano-multilyered coatings showed better wear resistance than AlCrN coating. Due to the molybdenum and niobium in the coating, AlCrSiN/MoN and AlCrSiN/NbN coatings showed the best wear resistance.

  8. Practical design of Ni{sub 3}Al with high hot workability

    SciTech Connect

    Wang, Y.; Lin, D.; Zhang, Y.

    1997-12-31

    From the previous work, Ni{sub 3}Al polycrystals with combined addition of magnesium and silicon kept high values of compressive strain at rupture (CSR) when the strain rate rose. In order to further improve hot workability of Ni{sub 3}Al, 7.9 wt.% Cr was added. The compressive tests showed that 30%--40% CSR values of the alloy had been kept in a wide temperature range of 1,173 K--1373 K at strain rates of 10{sup {minus}2}sec{sup {minus}1} and 10{sup {minus}1}sec{sup {minus}1} in contrast with 15%--25% CSR values of the alloy without Cr addition. In practical hot rolling process, at initial deformation temperature of 1,373 K, strain rate of 1.0 sec{sup {minus}1} and by controlling reduction within 10--15% each rolling pass, Ni{sub 3}Al ingots were successfully hot-rolled into polycrystals with different deformations, the maximum of which was 55%. The deformed alloys had manifestly enhanced mechanical properties shown by tensile tests. The dislocation configurations of deformed alloys have been investigated by using transmission electron microscope (TEM).

  9. Effect of prior oxidation on the creep behavior of NiAl-hardened austenitic steel

    NASA Astrophysics Data System (ADS)

    Satyanarayana, D. V. V.; Malakondaiah, G.; Sarma, D. S.

    2003-11-01

    The effect of prior oxidation at 1473 K on the creep behavior of an Fe-Ni-Cr-Al alloy, hardened by ordered NiAl precipitates, has been investigated at 873 K over a stress range of 275 to 450 MPa. The alloy in the as-electroslag remelted (ESR) as well as the ESR-plus-hot-worked conditions was considered. Prior oxidation causes creep strengthening in the Fe-Ni-Cr-Al alloy, resulting in a decrease in minimum creep rate and increase in time to rupture, in contrast to the observations reported on nickel-based superalloys. Creep strengthening is, however, accompanied by a significant reduction in creep ductility. Oxidation-induced creep strengthening in the current alloy can be attributed to the improved adherence of surface oxide caused by the presence of yttrium. An effective stress that incorporates the contributions of load transfer as well as substructural strengthening is used to account for the observed oxidation-induced creep strengthening. While creep strengthening is more pronounced in the ESR cast alloy, the loss in creep ductility is more intense in the ESR wrought alloy. Increasing the oxidation time beyond 1 hour has a minimal effect on creep strengthening of both the alloys, though it lowers significantly the creep ductility of the wrought alloy. The observed differences in creep behavior of the alloy in the two different conditions could be attributed to the differences in grain size as well as morphology and related oxidation-induced damage.

  10. Comparison of AlCrN and AlCrTiSiN coatings deposited on the surface of plasma nitrocarburized high carbon steels

    NASA Astrophysics Data System (ADS)

    Chen, Wanglin; Zheng, Jie; Lin, Yue; Kwon, Sikchol; Zhang, Shihong

    2015-03-01

    The AlCrN and AlCrTiSiN coatings were produced on the surface of plasma nitrocarburized T10 steels by multi-arc ion plating. The comparison of the microstructures and mechanical properties of the duplex coatings were investigated by means of X-ray diffraction, optical microscope, scanning electron microscope and transmission electron microscope, in association with mechanical property measurement. The results show that the AlCrN coatings with columnar grown are mainly composed of nanocrytalline fcc-(Cr,Al)N phases with {111} preferred orientation, whereas the superlattice and nanocomposite AlCrTiSiN coatings with planar growth mainly consist of nanocrystalline fcc-(Cr,Al)N phases with {100} perfected orientation, hcp-AlN and Si3N4 amorphous phases. The AlCrTiSiN duplex coating with the compound layer reveals higher hardness, adhesion strength, load capacity and lower friction coefficient when compared with the other duplex coatings, which is due to its superlattice and nanocomposite structure. Additionally, these improved properties are related to the appearance of the γ‧-phase which plays the nucleation sites for the coating nitrides and provides a strong supporting effect for the AlCrN and AlCrTiSiN coatings. The main wear mechanism of the duplex coatings without compound layer is spalling and chipping wear as well as tribooxidation wear, whereas the main wear mechanism of the duplex coatings with compound layer is tribooxidation wear.

  11. Cd, Ni, Cr and Pb distribution in biosolid pellets used as soil amendment

    NASA Astrophysics Data System (ADS)

    Jordán, Manuel M.; Rincón-Mora, Beatriz; Belén Almendro-Candel, María; Navarro Pedreño, Jose; Gómez Lucas, Ignacio; Bech, Jaume; Roca, Nuria; Pardo, Francisco

    2016-04-01

    The application of biosolids to a soil is a method that offers important benefits (Navarro et al. 2003). The transport and application costs are quite low (mostly if they are dehydrated biosolids or pellets) if soils are located near a wastewater treatment plant. It is possible to recycle nutrients (N, P, and K) and organic matter by improving the physical and chemical characteristics of the soil and by reducing the fertilizer costs. However, the use of biosolids may also has several problems, such as the presence of quantities of metals that could be toxic for plants or could contaminate ground-waters after being leached. Heavy metals are one of the most serious environmental pollutants because of its high toxicity, abundance and easy accumulation by plant (Soriano-Disla et al. 2014; Rosen and Chen 2014). Contamination of soils by potentially toxic elements (e.g. Cd, Ni, Cr, Pb) from amendments of biosolids is subject to rigorous controls within the European Union. The present study was designed to examine the partition of selected heavy metals in biosolid pellets, and also to relate the distribution patterns of these metals. Samples were collected from the treatment of urban wastewater at the drying grounds of a wastewater processing plant. The samples correspond to biosolids with humidities below 20% and are representative of the three horizons within the pile: the isolation surface (H1), the mesophilous area (H2), and the thermophilous area (H3). Biosolid aggregates were placed in a pellet press and then compacted. Total content of metals was determined following microwave digestion and analysed by ICP/MS. Triplicate samples were weighed in polycarbonate centrifuge tubes and sequentially extracted. The distribution of chemical forms of Cd, Ni, Cr, and Pb in the biosolids was studied using a sequential extraction procedure that fractionates the metal into soluble-exchangeable, specifically sorbed-carbonate bound, oxidizable, reducible, and residual forms. The

  12. Supercoducting property of Zr-Cu-Al-Ni-Nb alloys

    NASA Astrophysics Data System (ADS)

    Okai, D.; Motoyama, G.; Kimura, H.; Inoue, A.

    The superconducting property of Zr55Cu(30-X)Al10Ni5NbX alloys prepared by arc melting and liquid quenching methods was investigated by magnetic susceptibility measurements. The crystalline alloys with X = 0∼25 at.% prepared by arc melting method exhibited superconductivity with maximum Tc,on of 10.1 K. The alloys (X = 10∼23 at.%) with crystalline particles embedded in an amorphous structure, which were fabricated by melt spinning method, showed superconductivity with Tc,on of less than 4.0 K. The superconducting property of the Zr-Cu-Al-Ni-Nb alloys was attributed to superconducting phases of Zr2Cu, Zr2Ni, Zr65Al10Nb25 and Zr-Nb contained in the Zr-Cu-Al-Ni-Nb alloys. The melt-spun Zr55Cu(30-X)Al10Ni5NbX (X = 10∼20 at.%) alloys exhibited glass transition at 718∼743 K and were found to be superconducting metallic glasses.

  13. CVD Fiber Coatings for Al2O3/NiAl Composites

    NASA Technical Reports Server (NTRS)

    Boss, Daniel E.

    1995-01-01

    While sapphire-fiber-reinforced nickel aluminide (Al2O3/NiAl) composites are an attractive candidate for high-temperature structures, the significant difference in the coefficient of thermal expansion between the NiAl matrix and the sapphire fiber creates substantial residual stresses in the composite. This study seeks to produce two fiber-coating systems with the potential to reduce the residual stresses in the sapphire/NiAl composite system. Chemical vapor deposition (CVD) was used to produce both the compensating and compliant-fiber coatings for use in sapphire/NiAl composites. A special reactor was designed and built to produce the FGM and to handle the toxic nickel precursors. This process was successfully used to produce 500-foot lengths of fiber with coating thicknesses of approximately 3 microns, 5 microns, and 10 microns.

  14. Silicon's role in determining swelling in neutron-irradiated Fe-Cr-Ni-Si alloys

    SciTech Connect

    Sekimura, N. ); Garner, F. A. ); Newkirk, J.W. )

    1991-11-01

    Two silicon-modified alloy series, one based on Fe-15Cr-20Ni and another based on Fe-15Cr-25Ni were irradiated at target temperatures between 399 and 649{degree}C in EBR-II. The influence of silicon on swelling is more complex than previously envisioned and indicates that silicon plays two or more competing roles while in solution. Radiation-induced formation of {gamma}{prime} (Ni{sub 3}Si) precipitates is dependent on silicon and nickel content, as well as temperature. Precipitation of {gamma}{prime} appears to play only a minor role in void formation.

  15. Oxidation of Al2O3 continuous fiber-reinforced/NiAl composites

    NASA Technical Reports Server (NTRS)

    Doychak, J.; Nesbitt, J. A.; Noebe, R. D.; Bowman, R. R.

    1992-01-01

    The 1200 C and 1300 C isothermal and cyclic oxidation behavior of Al2O3 continuous fiber-reinforced/NiAl composites were studied. Oxidation resulted in formation of Al2O3 external scales in a similar manner as scales formed on monolithic NiAl. The isothermal oxidation of an Al2O3/NiAl composite resulted in oxidation of the matrix along the fiber/matrix interface near the fiber ends. This oxide acted as a wedge between the fiber and the matrix, and, under cyclic oxidation conditions, led to further oxidation along the fiber lengths and eventual cracking of the composite. The oxidation behavior of composites in which the Al2O3 fibers were sputter coated with nickel prior to processing was much more severe. This was attributed to open channels around the fibers which formed during processing, most likely as a result of the diffusion of the nickel coating into the matrix.

  16. Experimental evidence of Cr magnetic moments at low temperature in Cr2A(A=Al, Ge)C.

    PubMed

    Jaouen, M; Bugnet, M; Jaouen, N; Ohresser, P; Mauchamp, V; Cabioc'h, T; Rogalev, A

    2014-04-30

    From x-ray magnetic circular dichroism experiments performed at low temperature on Cr2AlC and Cr2GeC thin films, it is evidenced that Cr atoms carry a net magnetic moment in these ternary phases. It is shown that the Cr magnetization of the Al-based compound nearly vanished at 100 K in agreement with what has been recently observed on bulk. X-ray linear dichroism measurements performed at various angles of incidence and temperatures clearly demonstrate the existence of a charge ordering along the c axis of the structure of Cr2AlC. All these experimental observations support, in part, theoretical calculations claiming that Cr dd correlations have to be considered to correctly describe the structure and properties of these Cr-based ternary phases. PMID:24721758

  17. Effect of CeO2 on Cyclic Hot-Corrosion Behavior of Detonation-Gun Sprayed Cr3C2-NiCr Coatings on Ni-Based Superalloy

    NASA Astrophysics Data System (ADS)

    Saladi, Sekar; Menghani, Jyoti; Prakash, Satya

    2015-03-01

    The hot-corrosion behavior of detonation-gun sprayed Cr3C2-NiCr coatings with and without 0.4 wt.% CeO2 additive on Ni-based superalloy inconel-718 is comparatively discussed in the present study. Hot-corrosion studies were carried out at 900 °C for 100 cycles in Na2SO4-60%V2O5 molten salt environment under cyclic heating and cooling conditions on bare and coated superalloys. The thermo-gravimetric technique was used to establish kinetics of hot-corrosion. XRD, FESEM/EDAX, and EDX mapping techniques were used to analyze the corrosion products of bare and coated samples. The results indicate that Cr3C2-NiCr-CeO2-coated superalloy showed better hot-corrosion resistance as compared to bare and Cr3C2-NiCr-coated superalloys. The addition of CeO2 has improved micro-hardness, porosity, and surface roughness values of Cr3C2-NiCr-CeO2 coating. The overall weight gain and parabolic rate constant of Cr3C2-NiCr-CeO2-coated superalloy were found to be lowest in the present study signifying that the addition of CeO2 in Cr3C2-NiCr powder has contributed to the development of adherent and dense oxide scale on the coating at elevated temperature.

  18. Alloying effect of Ni and Cr on irradiated microstructural evolution of type 304 stainless steels

    NASA Astrophysics Data System (ADS)

    Tan, L.; Busby, J. T.

    2013-11-01

    Life extension of the existing nuclear power plants imposes significant challenges to core structural materials that suffer increased fluences. This paper presents the microstructural evolution of a type 304 stainless steel and its variants alloyed with extra Ni and Cr under neutron irradiation at ˜320 °C for up to 10.2 dpa. Similar to the reported data of type 304 variants, a large amount of Frank loops, ultrafine G-phase/M23C6 particles, and limited amount of cavities were observed in the irradiated samples. The irradiation promoted the growth of pre-existing M23C6 at grain boundaries and resulted in some phase transformation to CrC in the alloy with both extra Ni and Cr. A new type of ultrafine precipitates, possibly (Ti,Cr)N, was observed in all the samples, and its amount was increased by the irradiation. Additionally, α-ferrite was observed in the type 304 steel but not in the Ni or Ni + Cr alloyed variants. The effect of Ni and Cr alloying on the microstructural evolution is discussed.

  19. Modification of tribology and high-temperature behavior of Ti 48Al 2Cr 2Nb intermetallic alloy by laser cladding

    NASA Astrophysics Data System (ADS)

    Liu, Xiu-Bo; Wang, Hua-Ming

    2006-06-01

    In order to improve the tribology and high-temperature oxidation properties of the Ti-48Al-2Cr-2Nb intermetallic alloy simultaneously, mixed NiCr-Cr 3C 2 precursor powders had been investigated for laser cladding treatment to modify wear and high-temperature oxidation resistance of the material. The alloy samples were pre-placed with NiCr-80, 50 and 20%Cr 3C 2 (wt.%), respectively, and laser treated at the same parameters, i.e., laser output power 2.8 kW, beam scanning speed 2.0 mm/s, beam dimension 1 mm × 18 mm. The treated samples underwent tests of microhardness, wear and high-temperature oxidation. The results showed that laser cladding with different constitution of mixed precursor NiCr-Cr 3C 2 powders improved surface hardness in all cases. Laser cladding with NiCr-50%Cr 3C 2 resulted in the best modification of tribology and high-temperature oxidation behavior. X-ray diffraction (XRD), optical microscope (OM), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS) analyses indicated that the formation of reinforced Cr 7C 3, TiC and both continuous and dense Al 2O 3, Cr 2O 3 oxide scales were supposed to be responsible for the modification of the relevant properties. As a result, the present work had laid beneficial surface engineering foundation for TiAl alloy applied as future light weight and high-temperature structural candidate materials.

  20. Atomic Mobilities and Interdiffusivities for fcc Ni-Cr-Nb Alloys

    NASA Astrophysics Data System (ADS)

    Xu, Gaochi; Liu, Yajun; Kang, Zhitao

    2016-06-01

    The atomic mobilities and diffusion characteristics for fcc Ni-Cr-Nb alloys are explored by diffusion couples annealed at 1273 K (1000 °C) for 200 hours. The interdiffusion coefficients are extracted from intersection points of two diffusion paths, after which the atomic mobilities of Ni, Cr, and Nb in fcc Ni-Cr-Nb alloys are inversely obtained within the CALPHAD framework with the aid of related thermodynamic descriptions. In order to verify the quality of obtained kinetic parameters so that an accurate Ni-based atomic mobility database can be established, the composition profiles in diffusion couples and the diffusion paths superimposed upon Gibbs triangle are explored, where the experimentally measured and calculated values show good agreement.

  1. Improving the low temperature ductility of NiAl

    NASA Technical Reports Server (NTRS)

    Guha, Sumit; Munroe, Paul R.; Baker, Ian

    1989-01-01

    As part of a study aimed at developing a ductile NiAl-based alloy, ingots of Ni-Fe-Al alloys were cast and hot extruded to rods. The purpose of the iron additions was two-fold viz; to produce a change in the slip vector from 001 to 111 line and, in one alloy, to add a L1(2)-structured ductile second phase. Extruded Ni-20Al-30Fe was two-phase, containing a pro-eutectic B2 phase in a fine lamellar structure of B2+L1(2) phases. Room temperature tensile testing of both single extruded and double extruded alloys resulted in 8-percent and 22-percent plastic elongation and yield stresses of 850 and 760 MPa, respectively. Fracture in both cases occurred by ductile tearing of the eutectic and transgranular cleavage of the proeutectic phase at 1350 MPa. The ductility in double extruded condition is higher than that reported earlier in rapidly solidified wires by Inoue et al. (1984). By comparison, extruded single-phase B2-structured Ni-30Al-20Fe exhibited a fracture strength of 780 MPa, no plasticity, and a mixture of intergranular fracture and transgranular cleavage. This is contrast to earlier work by Inoue et al. where a yield stress of 400 MPa, 5 percent plastic strain, and a mixture of dimple and intergranular fracture was reported.

  2. The Behavior of Gas Powder Laser Clad NiCrBSi Coatings Under Contact Loading

    NASA Astrophysics Data System (ADS)

    Savrai, R. A.; Makarov, A. V.; Soboleva, N. N.; Malygina, I. Yu.; Osintseva, A. L.

    2016-03-01

    The behavior of NiCrBSi coatings obtained by laser cladding from powders with various chromium, carbon and boron contents has been investigated under contact loading through microindentation using a Vickers indenter and via non-impact cyclic loading as per "sphere-to-surface" contact scheme. The phase composition of the coating containing 0.48% C, 14.8% Cr, 2.1% B is γ + Ni3B + Cr23C6 and that of the coating containing 0.92% C, 18.2% Cr, 3.3% B is γ + Ni3B + Cr7C3 + CrB. The established restrictions of the processes of plastic deformation and cracking for the more heavily alloyed and harder coating under contact fatigue loading are substantially due to its increased ability to deform predominantly in the elastic region under the used cyclic loading conditions. This is indicated by the obtained microindentation data and, therefore, the microindentation method (one-time indentation) can be used to assess the ability of the laser clad NiCrBSi coatings to withstand repeated contact loads.

  3. Synthesis of Bimetallic Ni-Cr Nano-Oxides as Catalysts for Methanol Oxidation in NaOH Solution.

    PubMed

    Gu, Yingying; Luo, Jing; Liu, Yicheng; Yang, Haihong; Ouyang, Ruizhou; Miao, Yuqing

    2015-05-01

    Bimetallic Ni-Cr nano-oxide catalysts were synthesized by thermal decomposition method and were investigated as the anode electrocatalysts for the oxidation of methanol. The catalysts were characterized by X-ray diffraction and transmission electron microscopy. The electroactivity of the catalysts towards methanol oxidation in a solution containing 0.25 M NaOH and 1.0 M MeOH was examined using cyclic voltammetry and chronoamperometry. The results indicate that a mixture of rhombohedral-structured NiO and Cr2O3 nanocrystals generated at the calcination temperature of 500-700 degrees C while octahedral-structured spinel NiCr2O4 formed at higher temperature. The influence of metallic molar ratio on the electrocatalytic performance of the catalysts was studied. The Ni-Cr nano-oxides prepared at comparatively low temperature displayed significantly higher catalytic activity and durability in alkaline solution toward electrooxidation of methanol compared with the pure nano NiO. The results indicate a synergy effect between NiO and Cr2O3 enhancing the electrocatalytic properties of the bimetallic Ni-Cr nano-oxide catalysts. Meanwhile, NiCr2O4 hardly increased the activity and durability of the catalyst. In addition, the Ni-Cr catalyst also exhibited excellent stability and good reproducibility. Therefore, Ni-Cr nano-oxide catalyst may be a suitable and cheap electrocatalyst for methanol oxidation in alkaline medium. PMID:26505000

  4. High-Temperature Oxidation-Resistant and Low Coefficient of Thermal Expansion NiAl-Base Bond Coat Developed for a Turbine Blade Application

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Many critical gas turbine engine components are currently made from Ni-base superalloys that are coated with a thermal barrier coating (TBC). The TBC consists of a ZrO2-based top coat and a bond coat that is used to enhance the bonding between the superalloy substrate and the top coat. MCrAlY alloys (CoCrAlY and NiCrAlY) are currently used as bond coats and are chosen for their very good oxidation resistance. TBC life is frequently limited by the oxidation resistance of the bond coat, along with a thermal expansion mismatch between the metallic bond coat and the ceramic top coat. The aim of this investigation at the NASA Glenn Research Center was to develop a new longer life, higher temperature bond coat by improving both the oxidation resistance and the thermal expansion characteristics of the bond coat. Nickel aluminide (NiAl) has excellent high-temperature oxidation resistance and can sustain a protective Al2O3 scale to longer times and higher temperatures in comparison to MCrAlY alloys. Cryomilling of NiAl results in aluminum nitride (AlN) formation that reduces the coefficient of thermal expansion (CTE) of the alloy and enhances creep strength. Thus, additions of cryomilled NiAl-AlN to CoCrAlY were examined as a potential bond coat. In this work, the composite alloy was investigated as a stand-alone substrate to demonstrate its feasibility prior to actual use as a coating. About 85 percent of prealloyed NiAl and 15 percent of standard commercial CoCrAlY alloys were mixed and cryomilled in an attritor with stainless steel balls used as grinding media. The milling was carried out in the presence of liquid nitrogen. The milled powder was consolidated by hot extrusion or by hot isostatic pressing. From the consolidated material, oxidation coupons, four-point bend, CTE, and tensile specimens were machined. The CTE measurements were made between room temperature and 1000 C in an argon atmosphere. It is shown that the CTE of the NiAl-AlN-CoCrAlY composite bond coat

  5. Ductility enhancement in NiAl (B2)-base alloys by microstructural control

    NASA Astrophysics Data System (ADS)

    Ishida, K.; Kainuma, R.; Ueno, N.; Nishizawa, T.

    1991-02-01

    An attempt to improve ductility of NiAl (B2)-base alloys has been made by the addition of alloying elements and the control of microstructure. It has been found that a small amount of fcc γ phase formed by the addition of Fe, Co, and Cr has a drastic effect not only on the hot workability but also on the tensile ductility at room temperature. The enhancement in ductility is mainly due to the modification of Β-phase grains by the coexistence of γ phase. The effect of alloying elements on the hot forming ability is strongly related to the phase equilibria and partition behavior among γ, γ' (L12 structure), and Β phases in the Ni-Al-X alloy systems. The ductility-enhancement method shows promise for expanding the practical application of nickel aluminide.

  6. Defect and solute properties in dilute Fe-Cr-Ni austenitic alloys from first principles

    NASA Astrophysics Data System (ADS)

    Klaver, T. P. C.; Hepburn, D. J.; Ackland, G. J.

    2012-05-01

    We present results of an extensive set of first-principles density functional theory calculations of point defect formation, binding, and clustering energies in austenitic Fe with dilute concentrations of Cr and Ni solutes. A large number of possible collinear magnetic structures were investigated as appropriate reference states for austenite. We found that the antiferromagnetic single- and double-layer structures with tetragonal relaxation of the unit cell were the most suitable reference states and highlighted the inherent instabilities in the ferromagnetic states. Test calculations for the presence and influence of noncollinear magnetism were performed but proved mostly negative. We calculate the vacancy formation energy to be between 1.8 and 1.95 eV. Vacancy cluster binding was initially weak at 0.1 eV for divacancies but rapidly increased with additional vacancies. Clusters of up to six vacancies were studied and a highly stable octahedral cluster and stacking fault tetrahedron were found with total binding energies of 2.5 and 2.3 eV, respectively. The <100> dumbbell was found to be the most stable self-interstitial with a formation energy of between 3.2 and 3.6 eV and was found to form strongly bound clusters, consistent with other fcc metals. Pair interaction models were found to be capable of capturing the trends in the defect cluster binding energy data. Solute-solute interactions were found to be weak in general, with a maximal positive binding of 0.1 eV found for Ni-Ni pairs and maximum repulsion found for Cr-Cr pairs of -0.1 eV. Solute cluster binding was found to be consistent with a pair interaction model, with Ni-rich clusters being the most stable. Solute-defect interactions were consistent with Ni and Cr being modestly oversized and undersized solutes, respectively, which is exactly opposite to the experimentally derived size factors for Ni and Cr solutes in type 316 stainless steel and in the pure materials. Ni was found to bind to the vacancy and

  7. Importance of doping and frustration in itinerant Fe-doped Cr2Al

    DOE PAGESBeta

    Susner, M. A.; Parker, D. S.; Sefat, A. S.

    2015-05-12

    We performed an experimental and theoretical study comparing the effects of Fe-doping of Cr2Al, an antiferromagnet with a N el temperature of 670 K, with known results on Fe-doping of antiferromagnetic bcc Cr. (Cr1-xFex)2Al materials are found to exhibit a rapid suppression of antiferromagnetic order with the presence of Fe, decreasing TN to 170 K for x=0.10. Antiferromagnetic behavior disappears entirely at x≈0.125 after which point increasing paramagnetic behavior is exhibited. Moreover, this is unlike the effects of Fe doping of bcc antiferromagnetic Cr, in which TN gradually decreases followed by the appearance of a ferromagnetic state. Theoretical calculations explainmore » that the Cr2Al-Fe suppression of magnetic order originates from two effects: the first is band narrowing caused by doping of additional electrons from Fe substitution that weakens itinerant magnetism; the second is magnetic frustration of the Cr itinerant moments in Fe-substituted Cr2Al. In pure-phase Cr2Al, the Cr moments have an antiparallel alignment; however, these are destroyed through Fe substitution and the preference of Fe for parallel alignment with Cr. This is unlike bulk Fe-doped Cr alloys in which the Fe anti-aligns with the Cr atoms, and speaks to the importance of the Al atoms in the magnetic structure of Cr2Al and Fe-doped Cr2Al.« less

  8. Interstitial precipitation in Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Spear, W. S.; Polonis, D. H.

    1994-06-01

    Two separate stages of precipitation have been identified during the aging of ternary Fel8Cr3Al and Fel8Cr5Al alloys at temperatures in the vicinity of 475 °C. The first stage involves the formation of interstitial precipitates resulting from C and N impurities; the second and slower stage is the formation of the Cr-rich α' phase. Transmission electron microscopy (TEM) results show that carbonitride precipitation occurs preferentially at dislocations, stacking faults, and grain boundaries, and also uniformly through the matrix. Aging for times in excess of 400 hours at 475 °C promotes coarsening of the heterogeneous precipitates and dissolution of the uniformly distributed matrix particles. A resistometric analysis shows that the kinetics of the initial stages of precipitation can be described by a (time)2/3 relation. This kinetic behavior is explained in terms of stress-assisted diffusion in the highly stressed matrix resulting from coherency strains accompanying carbonitride precipitation. Experimental values of the activation energy for the first stage reaction correlate closely with those reported for the interstitial diffusion of C and N in alpha iron.

  9. Selective Internal Oxidation as a Mechanism for Intergranular Stress Corrosion Cracking of Ni-Cr-Fe Alloys

    NASA Astrophysics Data System (ADS)

    Capell, Brent M.; Was, Gary S.

    2007-06-01

    The mechanism of selective internal oxidation (SIO) for intergranular stress corrosion cracking (IGSCC) of nickel-base alloys has been investigated through a series of experiments using high-purity alloys and a steam environment to control the formation of NiO on the surface. Five alloys (Ni-9Fe, Ni-5Cr, Ni-5Cr-9Fe, Ni-16Cr-9Fe, and Ni-30Cr-9Fe) were used to investigate oxidation and intergranular cracking behavior for hydrogen-to-water vapor partial pressure ratios (PPRs) between 0.001 and 0.9. The Ni-9Fe, Ni-5Cr, and Ni-5Cr-9Fe alloys formed a uniform Ni(OH)2 film at PPRs less than 0.09, and the higher chromium alloys formed chromium-rich oxide films over the entire PPR range studied. Corrosion coupon results show that grain boundary oxides extended for significant depths (>150 nm) below the sample surface for all but the highest Cr containing alloy. Constant extension rate tensile (CERT) test results showed that intergranular cracking varied with PPR and cracking was more pronounced at a PPR value where nonprotective Ni(OH)2 was able to form and a link between the nonprotective Ni(OH)2 film and the formation of grain boundary oxides is suggested. The observation of grain boundary oxides in stressed and unstressed samples as well as the influence of alloy content on IG cracking and oxidation support SIO as a mechanism for IGSCC.

  10. The effects of reactive-element, ion-implantation-induced amorphous layers on the oxidation of Co-12Cr and Ni-12Cr alloys

    SciTech Connect

    Hampikian, J.M.

    1998-08-01

    Nickel-chromium (Ni-12Cr, wt.%) and cobalt-chromium (Co-12Cr, wt.%) alloys were ion implanted with 150 keV yttrium to fluences that ranged between 2 {times} 10{sup 16} and 1 {times} 0{sup 17} ions/cm{sup 2}. The influence of the implantation on the microstructure of the alloy was determined. The effect of the highest dose implantation on the alloys` oxidation response at 1,000 C, 48 hr was measured. Both alloys contained an amorphous surface phase as a result of this fluence and one of the effects of oxidation was to recrystallize the amorphized alloy in the first few minutes of oxidation. The lower doses of 2 {times} 10{sup 16} ions/cm{sup 2} were sufficient to cause amorphization of both the Ni-12Cr and the Co-12Cr. The implantation reduced the isothermal mass gain by a factor of 25% for the Ni-12Cr, but had a negligible effect on the Co-12Cr alloy. Short-term oxidation of experiments at 600 C showed via transmission electron microscopy that, in the absence of the yttrium implant, the Ni-12Cr alloy forms NiO in the first minute of oxidation and the Co-12Cr alloy forms CoO and CoCr{sub 2}O{sub 4}. The implanted Ni-12Cr, on the other hand (1 {times} 10{sup 17} Y{sup +}/cm{sup 2}), forms recrystallized Ni-Cr, Y{sub 2}O{sub 3}, and NiO in the near-surface region, while the implanted Co-12Cr alloy forms CoO, CoCr{sub 2}O{sub 4}, and a recrystallized intermetallic alloy from the amorphized region.

  11. Normal and excess nitrogen uptake by iron-based Fe-Cr-Al alloys: the role of the Cr/Al atomic ratio

    NASA Astrophysics Data System (ADS)

    Jung, K. S.; Schacherl, R. E.; Bischoff, E.; Mittemeijer, E. J.

    2011-06-01

    Upon nitriding ferritic iron-based Fe-Cr-Al alloys, containing a total of 1.50 at. % (Cr + Al) alloying elements with varying Cr/Al atomic ratio (0.21-2.00), excess nitrogen uptake occurred, i.e. more nitrogen was incorporated in the specimens than compatible with only inner nitride formation and equilibrium nitrogen solubility of the unstrained ferrite matrix. The amount of excess nitrogen increased with decreasing Cr/Al atomic ratio. The microstructure of the nitrided zone was investigated by X-ray diffraction, electron probe microanalysis, transmission electron microscopy and electron energy loss spectroscopy. Metastable, fine platelet-type, mixed Cr1- x Al x N nitride precipitates developed in the nitrided zone for all of the investigated specimens. The degree of coherency of the nitride precipitates with the surrounding ferrite matrix is discussed in view of the anisotropy of the misfit. Analysis of nitrogen-absorption isotherms, recorded after subsequent pre- and de-nitriding treatments, allowed quantitative differentiation of different types of nitrogen taken up. The amounts of the different types of excess nitrogen as function of the Cr/Al atomic ratio are discussed in terms of the nitride/matrix misfit and the different chemical affinities of Cr and Al for N. The strikingly different nitriding behaviors of Fe-Cr-Al and Fe-Cr-Ti alloys could be explained on this basis.

  12. Carbon Nanostructures Grown on Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Čaplovičová, Mária; Čaplovič, Ľubomír; Búc, Dalibor; Vinduška, Peter; Janík, Ján

    2010-11-01

    The morphology and nanostructure of carbon nanotubes (CNTs), synthesized directly on Fe-Cr-Al-based alloy substrate using an alcohol catalytic chemical vapour deposition method (ACCVD), were examined by transmission electron microscopy (TEM). The grown CNTs were entangled with chain-like, bamboo-like, and necklace-like morphologies. The CNT morphology was affected by the elemental composition of catalysts and local instability of deposition process. Straight and bended CNTs with bamboo-like nanostructure grew mainly on γ-Fe and Fe3C particles. The synthesis of necklace-like nanostructures was influenced by silicon oxide, and growth of chain-like nanostructures was supported by a catalysts consisting of Fe, Si, oxygen and trace of Cr. Most of nanotubes grew according to base growth mechanism.

  13. He self-pumping by tokamak pump limiter materials: Al, V, Ni, and Ni/Al alloys

    SciTech Connect

    Outten, C.A. ); Barbour, J.C.; Doyle, B.L. ); Walsh, D.S. )

    1991-01-01

    An ECR plasma and Colutron ion gun were used to study He self-pumping by several possible pump-limiter materials: Ni, V, Al, and Ni/Al multi-layers. Ni and V exhibited similar pumping capacities (6 {times} 10{sup 15} He/cm{sup 2}, 200 eV) whereas Al showed a reduced capacity (6 {times} 10{sup 14} He/cm{sup 2}, 200 eV) due to increased sputtering. A He retention model based upon ion implantation ranges and sputtering rates agreed with the experimental data. The pumping efficiency increased significantly with ion energy. A new multilayer/bilayer pumping concept showed improved pumping above that for single element films. 4 refs., 5 figs.

  14. Mössbauer Investigation of Electrodeposited Sn-Zn, Sn-Cr, Sn-Cr-Zn and Fe-Ni-Cr Coatings

    NASA Astrophysics Data System (ADS)

    Kuzmann, E.; Stichleutner, S.; El-Sharif, M.; Chisholm, C. U.; Sziráki, L.; Homonnay, Z.; Vértes, A.

    2002-06-01

    57Fe and 119Sn CEMS, XRD and electrochemical measurements were used to investigate the effect of the preparation parameters and the components on the structure and phase composition of electrodeposited Fe-Ni-Cr alloys in connection with their corrosion behavior. XRD of the electrodeposits reflect an amorphous-like character. 57Fe CEM spectra of Fe-Ni-Cr electrodeposited samples, prepared in a continuous flow plating plastic circulation cell with variation of current density, electrolyte velocity and temperature, can be evaluated as a doublet associated with a highly disordered paramagnetic solid solution phase. This phase was identified earlier in Fe-Ni-Cr electrodeposits that were prepared by another plating method and contained both ferromagnetic and paramagnetic metastable phases [1]. This is the first time that we have succeeded to prepare Fe-Ni-Cr alloys containing only the metastable paramagnetic phase. The effect of the plating parameters on the structure is also analysed by the quadrupole splitting distribution method. 119Sn CEM spectra of all Sn-containing plated alloys show a broad line envelop which can be decomposed at least into two components. One can be associated with β-tin. The other one can be assigned to an alloy phase. The structure and distribution of microenvironments of these phases depends on the plating parameters especially on the parameters of the reverse pulse applied.

  15. Thermal evolution of vacancy-type defects in quenched FeCrNi alloys

    NASA Astrophysics Data System (ADS)

    Zhang, C. X.; Cao, X. Z.; Li, Y. H.; Jin, S. X.; Lu, E. Y.; Tian, H. W.; Zhang, P.; Wang, B. Y.

    2015-06-01

    The effect of isochronal annealing on vacancy-type defects in quenched FeCrNi alloys and SUS316 was investigated via positron annihilation technique. Vacancy-type defects clustered and grew with increasing annealing temperatures of up to 523 K and, in FeCrNi alloys, were gradually annihilated with increasing temperature. The annihilation temperature was relatively insensitive to the addition of Mo and nonmetal elements, and after annealing at 673 K, the vacancy-type defects were annihilated and dislocation-type defects were formed in all of the alloys. In addition, due to the formation of Mo-vacancy complexes, the density of defects in the Mo-diluted FeCrNi model alloy was lower than that in the FeCrNi model alloy. The long lifetime of vacancy-type defects in commercial stainless steel SUS316 was smaller than that in the FeCrNi model alloys due to the nonmetal-element-induced change in mobility of the defects. Moreover, the vacancy-type and dislocation-type defects contributed to the S and W parameters of positron annihilation during the entire annealing treatment.

  16. Production of Ni-Cr-Ti-natural fibres composite and investigation of mechanical properties

    SciTech Connect

    Pesmen, G.; Erol, A.

    2015-03-30

    Intermetallic materials such as Ni{sub 2}Ti, Cr{sub 2}Ti are among advanced technology materials that have outstanding mechanical and physical properties for high temperature applications. Especially creep resistance, low density and high hardness properties stand out in such intermetallics. The microstructure, mechanical properties of (%50Ni-%48Cr-%2Ti)-%10Naturel Fibres and (%64Ni-%32Cr-%4Ti)-%10Naturel Fibres powders were investigated using specimens produced by tube furnace sintering at 1000-1200-1400°C temperature. A composite consisting of ternary additions, a metallic phase, Ti,Cr and Ni have been prepared under Ar shroud and then tube furnace sintered. XRD, SEM (Scanning Electron Microscope), were investigated to characterize the properties of the specimens. Experimental results carried out for composition (%64Ni-%32Cr-%4Ti)-%10Naturel at 1400°C suggest that the best properties as 112.09HV and 5,422g/cm{sup 3} density were obtained at 1400°C.

  17. Evolution of cavity microstructure in ion-irradiated 316 SS and Fe-20Ni-15Cr alloy. [Fe-20Ni-15Cr

    SciTech Connect

    Kohyama, A.; Loomis, B.; Ayrault, G.; Igata, N.

    1984-04-01

    The effect of helium implantation schedule on the evolution of the cavity microstructure in 316 SS and Fe-20Ni-15Cr alloy during heavy-ion irradiation was investigated for damage levels up to 100 dpa with three helium injection schedules, i.e., 15 appm He/dpa, 50 appm He/dpa and 15 appm He preinjected prior to Ni/sup +/ ion irradiation. In the case of the dual-ion irradiated specimens, there was a trend towards a saturation of the swelling with increasing damage level that was closely related to the saturation and subsequent decrease of the number density of the small cavities (<8 nm diameter for 316 SS and <4 nm for Fe-20Ni-15Cr) and the dislocation density. The bi-model cavity size distribution that was determined for the Fe-20Ni-15Cr alloy at 40 dpa changed to uni-modal distribution at 65 and 100 dpa. Radiation-induced segregation was high and this was related to the saturation tendency for the swelling.

  18. Characterization of Cold-Sprayed IN625 and NiCr Coatings

    NASA Astrophysics Data System (ADS)

    Srinivasan, Dheepa; Chandrasekhar, Vighnesh; Amuthan, Ramar; Lau, Y. C.; Calla, Eklavya

    2016-04-01

    Ni-based coatings IN625® and Ni20%Cr were cold sprayed on a low-alloy steel (AISI 4130) substrate, using Helium as the process gas. Dense coatings up to 3-mm thickness were deposited, having a hardness of 500-550 HV. The coatings showed a hardness maximum, with heat treatment, before dropping to a lower value. The coating microstructure revealed two distinct types of regions, comprising grains with a high dislocation density and elongated shear bands having twins. Heat treatment led to 30-50 nm grains in the IN625 coating, and >1-2 μm grains for NiCr. Both coatings showed a compressive residual stress in the as-sprayed condition, which relaxed to a zero residual stress, at 650 °C. The NiCr coatings showed a much higher compressibility, as compared to IN625. The IN625 coatings induced a much larger deformation on the 4130 steel. Overall, while both types of Ni-based alloy coatings showed similarities in terms of hardness and microstructure, they revealed distinct differences in their deformability, thermal stability, and substrate deformation, indicating a different behavior between a binary solid solution (NiCr) as compared to a multielement solid solution (IN625), as elucidated via a detailed characterization of these coatings.

  19. Evaluation of Ni-Cr-Base Alloys for SOFC Interconnect Applications

    SciTech Connect

    Yang, Z Gary; Xia, Gordon; Stevenson, Jeffry W.

    2006-10-06

    To further understand the suitability of Ni-Cr-base alloys for solid oxide fuel cell (SOFC) interconnect applications, three commercial Ni-Cr-base alloys, Haynes 230, Hastelloy S and Haynes 242 were selected and evaluated for oxidation behavior under different exposure conditions, scale conductivity and thermal expansion. Haynes 230 and Hastelloy S, which have a relatively high Cr content, formed a thin scale mainly comprised of Cr2O3 and (Mn,Cr,Ni)3O4 spinels under SOFC operating conditions, demonstrating excellent oxidation resistance and a high scale electrical conductivity. In contrast, a thick double-layer scale with a NiO outer layer above a chromia-rich substrate was grown on Haynes 242 in moist air or at the air side of dual exposure samples, indicating limited oxidation resistance for the interconnect application. With a face-centered-cubic (FCC) substrate, all three alloys possess a coefficient of thermal expansion (CTE) that is higher than that of candidate ferritic stainless steels, e.g. Crofer22 APU. Among the three alloys, Haynes 242, which is heavily alloyed with W and Mo and contains a low Cr content, demonstrated the lowest average CTE at 13.1x10-6 K-1 from room temperature to 800oC, but it was also observed that the CTE behavior of Haynes 242 was very nonlinear.

  20. Evaluation of Ni-Cr-base alloys for SOFC interconnect applications

    NASA Astrophysics Data System (ADS)

    Yang, Zhenguo; Xia, Guan-Guang; Stevenson, Jeffry W.

    To further understand the suitability of Ni-Cr-base alloys for solid oxide fuel cell (SOFC) interconnect applications, three commercial Ni-Cr-base alloys, Haynes 230, Hastelloy S and Haynes 242 were selected and evaluated for oxidation behavior under different exposure conditions, scale conductivity and thermal expansion. Haynes 230 and Hastelloy S, which have a relatively high Cr content, formed a thin scale mainly comprised of Cr 2O 3 and (Mn,Cr,Ni) 3O 4 spinels under SOFC operating conditions, demonstrating excellent oxidation resistance and a high scale electrical conductivity. In contrast, a thick double-layer scale with a NiO outer layer above a chromia-rich substrate was grown on Haynes 242 in moist air or at the air side of dual exposure samples, indicating limited oxidation resistance for the interconnect application. With a face-centered-cubic (FCC) substrate, all three alloys possess a coefficient of thermal expansion (CTE) that is higher than that of candidate ferritic stainless steels, e.g. Crofer22 APU. Among the three alloys, Haynes 242, which is heavily alloyed with W and Mo and contains a low Cr content, demonstrated the lowest average CTE at 13.1 × 10 -6 K -1 from room temperature to 800 °C, but it was also observed that the CTE behavior of Haynes 242 was very non-linear.

  1. Zener Relaxation Peak in an Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Zhou, Zheng-Cun; Cheng, He-Fa; Gong, Chen-Li; Wei, Jian-Ning; Han, Fu-Sheng

    2002-11-01

    We have studied the temperature spectra of internal friction and relative dynamic modulus of the Fe-(25 wt%)Cr-(5 wt%)Al alloy with different grain sizes. It is found that a peak appears in the internal friction versus temperature plot at about 550°C. The peak is of a stable relaxation and is reversible, which occurs not only during heating but also during cooling. Its activation energy is 2.5 (+/- 0.15) eV in terms of the Arrhenius relation. In addition, the peak is not obvious in specimens with a smaller grain size. It is suggested that the peak originates from Zener relaxation.

  2. Preparation, structure and mechanical properties of RuAl and (Ru,Ni)Al alloys

    SciTech Connect

    Sabariz, A.L.R.; Taylor, G.

    1997-12-31

    The intermetallic compound, RuAl with B2 CsCl type structure, has been shown to possess room-temperature toughness and plasticity. NiAl also forms a B2 compound and it is claimed that a pseudo-binary compound, (Ru,Ni)Al, may be formed because the difference in lattice parameter between the two binary phases is slight. In this work a study has been made of the mechanical properties of some polycrystalline compounds, across the RuAl-(Ru,Ni)Al pseudo-binary, prepared from high-purity elemental powders. Compressive yield stresses were measured between room-temperature and 900 C, and the mechanisms of plastic flow are discussed in relation to the dislocation structures observed by TEM. Hot-microhardness tests were made to provide an indication of the effect of solid-solution hardening.

  3. 1300 K compressive properties of a reaction milled NiAl-AlN composites

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Arzt, Eduard; Luton, Michael J.

    1990-01-01

    When B2 crystal-structure nickel aluminide is subjected to high-intensity mechanical ball milling in a liquid nitrogen bath, or 'cryomilling', an NiAl composite is obtained which contains about 10 vol pct AlN particles. This composition arises from the incorporation of N during cryomilling; during subsequent thermomechanical processing, the N reacts with Al. While compressive testing of extruded or isostatically pressed specimens at 1300 K indicated that strength at relatively fast strain rates is slightly dependent on consolidation method, slower strain rates indicate no clear dependency on densification technique: four different consolidation methods were found to yield similar creep strengths. The creep properties of NiAl-AlN are similar to those of the single-crystal Ni-base superalloy NASAIR 100.

  4. Temperature dependence of the activity of Al in dilute Ni(Al) solid solutions

    SciTech Connect

    Jiang Yong; Smith, J. R.; Evans, A. G.

    2006-12-01

    Activities of dilute Al solid solutions in Ni are determined from a first-principles approach. Both thermal lattice vibration and electronic contributions to free energies are considered and compared. Vibrational contributions tend to dominate the temperature dependencies of the free energies, though electron thermal effects are significant. Calculations show opposing temperature trends for the formation enthalpies and entropies, leading to a partial cancellation of their role in the overall energetics. Nevertheless, their remaining temperature effects are strong. Over the temperature range, 400 KAl activity coefficient varies by 15 orders of magnitude, due to the relative strength of Al-Ni and Al-Al bonds. The Ni activity coefficient only varies less than 4% over the same range. Calculational results compare well with available experimental data. The thermodynamic principles elucidated from the calculations are used to provide a fundamental interpretation.

  5. Tensile Creep of Polycrystalline Near-Stoichiometric NiAl

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.

    2002-01-01

    Long term tensile creep studies were conducted on binary NiAl in the temperature range 700-1200 K with the objectives of characterizing and understanding the creep mechanisms. Inverse and normal primary creep curves were observed depending on stress and temperature. It was concluded that the creep of NiAl is limited by dislocation mobility. The stress exponent for creep, n, increased from 5.5 at 1200 K to 13.9 at 700 K. The true activation energy for creep, Qc, was constant and equal to about 400 kJ per mole between 20 and 50 MPa but decreased to a constant value of 250 kJ per mole between 50 and 110 MPa. The activation energy was observed to be stress dependent above 110 MPa. The tensile creep results reported in this investigation were compared with compression creep data reported in the literature. A detailed discussion of the probable dislocation creep mechanisms governing compressive and tensile creep of NiAl is presented. It is concluded that the non-conservative motion of jogs on screw dislocations influenced the nature of the primary creep curves, where the climb of these jogs involves either the next nearest neighbor or the six-jump cycle vacancy diffusion mechanism. The probable nature of the atom vacancy exchange that occur within the core of an edge dislocation undergoing climb in NiAl are schematically examined.

  6. Directional solidification studies in Ni-Al alloys

    SciTech Connect

    Lee, Je-hyun

    1993-05-01

    Three solid phases are involved in the phase equilibria of the intermetallic compound Ni{sub 3}Al near its melting point, {beta}, {gamma}{prime}(Ni{sub 3}Al), and {gamma}. The generally-accepted phase diagram involves a eutectic reaction between {beta}{prime} and {gamma}, but some recent studies agree with an older diagram due to Schramm, which has a eutectic reaction between the {beta} and {gamma}{prime} phases. The phase equilibria near Ni{sub 3}Al compositions was evaluated using quenched directional solidification experiments, that preserve the microstructures tonned at the solidification front, and using diffusion couple experiments. These experiments show that eutectic forms between {beta} and {gamma}{prime} phases, as in the Schramm diagram. Growth and phase transformations of these three phases are also studied in the directional solidification experiments. Microstructure analysis shows that etching of Ni{sub 3}Al({gamma}{prime}) is very sensitive to small composition variations and crystallographic orientation changes. The eutectic solidification study confirms that the equilibrium eutectic is {gamma}{prime}+{beta}, and that the metastable {gamma}+{beta} eutectic might be also produced in this system according to the impurities, solidification rates, and composition variations.

  7. High temperature stability, interface bonding, and mechanical behavior in. beta. -NiAl and Ni sub 3 Al matrix composites with reinforcements modified by ion beam enhanced deposition

    SciTech Connect

    Grummon, D.S.

    1992-01-22

    In preparation for experiments with surface modified Al{sub 2}O{sub 3} reinforcements in {beta}NiAl, diffusion bonding experiments were conducted. FP alumina fibers were prepared with ion sputtered surface films (Al{sub 2}O{sub 3}, Al, Ni) and then composited with {beta}NiAl slabs and hot pressed. After 70 thermal cycles, interfacial shear strength was measured. A roughness mechanism is proposed for the observed increased strength of the coated fibers. Creep in Ni{sub 3}Al was studied. 3 figs, 1 tab. (DLC)

  8. Growth and characterization of TiAlN/CrAlN superlattices prepared by reactive direct current magnetron sputtering

    SciTech Connect

    Barshilia, Harish C.; Deepthi, B.; Rajam, K. S.; Bhatti, Kanwal Preet; Chaudhary, Sujeet

    2009-01-15

    TiAlN and CrAlN coatings were prepared using a reactive direct current magnetron sputtering system from TiAl and CrAl targets. Structural characterization of the coatings using x-ray diffraction (XRD) revealed the B1 NaCl structure of TiAlN and CrAlN coatings with a prominent reflection along the (111) plane. The XPS data confirmed the bonding structures of TiAlN and CrAlN single layer coatings. Subsequently, nanolayered multilayer coatings of TiAlN/CrAlN were deposited on silicon and mild steel (MS) substrates at different modulation wavelengths ({lambda}) with a total thickness of approximately 1.0 {mu}m. The modulation wavelengths were calculated from the x-ray reflectivity data using modified Bragg's law. TiAlN/CrAlN multilayer coatings were textured along (111) for {lambda}<200 A and the XRD patterns showed the formation of superlattice structure for coatings deposited at {lambda}=102 A. The x-ray reflectivity data showed reflections of fifth and seventh orders for multilayer coatings deposited at {lambda}=102 and 138 A, respectively, indicating the formation of sharp interfaces between TiAlN and CrAlN layers. The cross-sectional scanning electron microscopy image of TiAlN/CrAlN multilayer coatings indicated a noncolumnar and dense microstructure. A maximum hardness of 39 GPa was observed for TiAlN/CrAlN multilayer coatings deposited at {lambda}=93 A, which was higher than the rule-of-mixture value (30 GPa) for TiAlN and CrAlN. Study of thermal stability of the coatings in air using micro-Raman spectroscopy indicated that the TiAlN/CrAlN multilayer coatings were stable up to 900 deg. C in air. TiAlN/CrAlN multilayer coatings also exhibited improved corrosion resistance when compared to the MS substrate.

  9. HYDROGEN ADSORPTION ON β-TiAl (001) AND Ni/TiAl (001) SURFACES

    NASA Astrophysics Data System (ADS)

    Mubarak, A. A. Karim; Alelaimi, Mahmoud

    2014-04-01

    In this paper, we present first principles calculations of the energetic, electronic and magnetic properties of the variant termination of TiAl (001) and Ni/TiAl (001) surfaces with and without hydrogen atoms. The calculations have been performed within the density functional theory using full-potential linearized augmented plane wave method. The generalized gradient approximation (GGA) is utilized as the exchange-correlation energy. The octahedral site is the stable absorption site of H atom in the β-TiAl system. This absorption reduces the cohesive energy of β-TiAl system due to increase in the lattice constant. The surface energy for both TiAl (001) terminations is calculated. The stable adsorption site of H atoms on the variant termination of TiAl (001) surface is performed. The adsorption energy of hydrogen on Ti is more energetic than that on Al. The adsorption of H atom on both terminations of H/Ni/TiAl (001) is more preferable at the bridge site. The adsorption energies are enhanced on Ni atom due to the contraction between d-Ni bands and TiAl substrate band.

  10. Spectroscopy and atomic physics of highly ionized Cr, Fe, and Ni for tokamak plasmas

    NASA Technical Reports Server (NTRS)

    Feldman, U.; Doschek, G. A.; Cheng, C.-C.; Bhatia, A. K.

    1980-01-01

    The paper considers the spectroscopy and atomic physics for some highly ionized Cr, Fe, and Ni ions produced in tokamak plasmas. Forbidden and intersystem wavelengths for Cr and Ni ions are extrapolated and interpolated using the known wavelengths for Fe lines identified in solar-flare plasmas. Tables of transition probabilities for the B I, C I, N I, O I, and F I isoelectronic sequences are presented, and collision strengths and transition probabilities for Cr, Fe, and Ni ions of the Be I sequence are given. Similarities of tokamak and solar spectra are discussed, and it is shown how the atomic data presented may be used to determine ion abundances and electron densities in low-density plasmas.

  11. Corrosion resistance of stainless steels and high Ni-Cr alloys to acid fluoride wastes

    SciTech Connect

    Smith, H.D.; Mackey, D.B.; Pool, K.H. ); Schwenk, E.B. )

    1992-04-01

    TRUEX processing of Hanford Site waste will utilize potentially corrosive acid fluoride processing solutions. Appropriate construction materials for such a processing facility need to be identified. Toward this objective, candidate stainless steels and high Ni-Cr alloys have been corrosion tested in simulated acid fluoride process solutions at 333K. The high Ni-Cr alloys exhibited corrosion rates as low as 0.14 mm/y in a solution with an HF activity of about 1.2 M, much lower than the 19 to 94 mm/y observed for austenitic stainless steels. At a lower HF activity (about 0.008 M), stainless steels display delayed passivation while high Ni-Cr alloys display essentially no reaction.

  12. Synthesis of NiCr2O4 spinel coatings with high emissivity by plasma spraying

    NASA Astrophysics Data System (ADS)

    Zhu, Zhen-Qi; Cheng, Xu-Dong; Ye, Wei-Ping; Min, Jie

    2012-03-01

    Air plasma spraying (APS) was used to produce high emissivity coatings with a NiCr2O4 spinel structure. The relationship between the emissivity and the crystal structure was investigated. X-ray diffraction (XRD) analyses show that NiCr2O4 spinel has been fabricated with the space group Fd3 m. Scanning electron microscope (SEM) photographs show that the coating consists of a laminated structure with homogeneous grains and high porosity because of the unique feature of plasma spraying. The emissivity measurement and Fourier transformation infrared radiation (FT-IR) spectra show that NiCr2O4 has a high emissivity of about 0.91 because of its special spinel structure. APS is a suitable method to produce high emissivity coatings.

  13. Experimental Study on Dynamic Mechanical Properties of 30CrMnSiNi2A Steel.

    NASA Astrophysics Data System (ADS)

    Huang, Fenglei; Yao, Wei; Wu, Haijun; Zhang, Liansheng

    2009-06-01

    Under dynamic conditions, the strain-rate dependence of material response and high levels of hydrostatic pressure cause the material behavior to be significantly different from what is observed under quasi-static condition. The curves of stress and strain of 30CrMnSiNi2A steel in different strain rates are obtained with SHPB experiments. Metallographic analyses show that 30CrMnSiNi2A steel is sensitive to strain rate, and dynamic compression leads to shear failure with the angle 45^o as the small carbide which precipitates around grain boundary changes the properties of 30CrMnSiNi2A steel. From the SHPB experiments and quasi-static results, the incomplete Johnson-Cook model has been obtained: σ=[1587+382.5(ɛ^p)^0.245][1+0.017ɛ^*], which can offer parameters for theory application and numerical simulation.

  14. Corrosion and oxidation properties of NiCr coatings sprayed in presence of gas shroud system

    NASA Astrophysics Data System (ADS)

    Morks, M. F.; Berndt, C. C.

    2010-04-01

    The oxidation of a NiCr bond coat during air plasma spraying was controlled by designing a gas shroud system attached to the plasma torch nozzle. Two nozzles, termed as "normal" and "high-speed" nozzles examined the effect of nozzle internal design on the microstructure and phase structure of coatings. X-ray diffraction and SEM morphologies showed that the shroud system reduced the oxidation of NiCr particles during the spray process. Compared with conventional air plasma spraying, the argon gas shroud reduced the coating hardness because the volume fraction of partially melted particles increased. The high-speed nozzle reduced the oxidation and hardness of NiCr coatings due to the increase of partially melted particles in the coatings.

  15. The evolution of phase transformation in Ni/Ni3Al laminated composite under high temperature treatments

    NASA Astrophysics Data System (ADS)

    Shmorgun, V.; Gurevich, L.; Bogdanov, A.; Trunov, M.

    2016-02-01

    In this study the impact of isothermal annealing on the phase transformation rate in laminated Ni/Ni2Al3 composite was investigated. The method of nickel-aluminide coatings of the required chemical composition fabrication was proposed.

  16. Host Atom Diffusion in Ternary Fe-Cr-Al Alloys

    NASA Astrophysics Data System (ADS)

    Rohrberg, Diana; Spitzer, Karl-Heinz; Dörrer, Lars; Kulińska, Anna J.; Borchardt, Günter; Fraczkiewicz, Anna; Markus, Torsten; Jacobs, Michael H. G.; Schmid-Fetzer, Rainer

    2014-01-01

    In the Fe-rich corner of the Fe-Cr-Al ternary phase diagram, both interdiffusion experiments [1048 K to 1573 K (775 °C to 1300 °C)] and 58Fe tracer diffusion experiments [873 K to 1123 K (600 °C to 850 °C)] were performed along the Fe50Cr50-Fe50Al50 section. For the evaluation of the interdiffusion data, a theoretical model was used which directly yields the individual self-diffusion coefficients of the three constituents and the shift of the original interface of the diffusion couple through inverse modeling. The driving chemical potential gradients were derived using a phenomenological Gibbs energy function which was based on thoroughly assessed thermodynamic data. From the comparison of the individual self-diffusivities of Fe as obtained from interdiffusion profiles and independent 58Fe tracer diffusivities, the influence of the B2-A2 order-disorder transition becomes obvious, resulting in a slightly higher activation enthalpy for the bcc-B2 phase and a significantly lower activation entropy for this phase.

  17. Lattice dynamics in austenitic stainless steels Fe 18Cr 12Ni 2Mo and Fe 18Cr 16Ni 10Mn

    NASA Astrophysics Data System (ADS)

    Rajevac, V.; Hoelzel, M.; Danilkin, S. A.; Hoser, A.; Fuess, H.

    2004-04-01

    Phonon dispersion curves of austenitic stainless steels Fe-18Cr-16Ni-10Mn and Fe-18Cr-12Ni-2Mo have been measured by triple-axis neutron spectroscopy. The data were analysed using Born-von Karman interactions as well as calculations including the contribution of conduction electrons on the lattice dynamics. An appropriate description of the experimental data was obtained by taking into account two-neighbour shells plus the contribution of the electron gas. The elastic constants and moduli obtained are close to reported results by ultrasonic studies on polycrystalline samples. The phonon densities of states in both systems calculated from the dispersion curves agree well with results obtained by time-of-flight neutron spectroscopy on polycrystalline samples. The Debye temperature THgr(T) shows a minimum around 40 K, similar to copper and nickel.

  18. Low temperature spin dynamics in Cr7Ni-Cu-Cr7Ni coupled molecular rings

    SciTech Connect

    Bordonali, L; Furukawa, Y; Mariani, M; Sabareesh, K P; Garlatti, E; Carretta, S; Lascialfari, A; Timco, G; Winpenny, R E; Borsa, F

    2014-05-07

    Proton Nuclear Magnetic Resonance (NMR) relaxation measurements have been performed down to very low temperature (50 mK) to determine the effect of coupling two Cr7 Ni molecular rings via a Cu2+ ion. No difference in the spin dynamics was found from nuclear spin lattice relaxation down to 1.5 K. At lower temperature, the 1H-NMR line broadens dramatically indicating spin freezing. From the plot of the line width vs. magnetization, it is found that the freezing temperature is higher (260 mK) in the coupled ring with respect to the single Cr7 Ni ring (140 mK).

  19. Precipitation Strengthening in Al-Ni-Mn Alloys

    NASA Astrophysics Data System (ADS)

    Fan, Yangyang; Huang, Kai; Makhlouf, Makhlouf M.

    2015-12-01

    Precipitation hardening of eutectic and hypoeutectic Al-Ni alloys by 2 to 4 wt pct. manganese is investigated with focus on the effect of the alloys' chemical composition and solidification cooling rate on microstructure and tensile strength. Within the context of the investigation, mathematical equations based on the Orowan Looping strengthening mechanism were used to calculate the strengthening increment contributed by each of the phases present in the aged alloy. The calculations agree well with measured values and suggest that the larger part of the alloy's yield strength is due to the Al3Ni eutectic phase, this is closely followed by contribution from the Al6Mn particles, which precipitate predominantly at grain boundaries.

  20. First-principles investigations of Ni3Al(111) and NiAl(110) surfaces at metal dusting conditions

    SciTech Connect

    Saadi, Souheil

    2011-03-01

    We investigate the structure and surface composition of the {gamma}{prime}-Ni{sub 3}Al(111) and {beta}-NiAl(110) alloy surfaces at conditions relevant for metal dusting corrosion related to catalytic steam reforming of natural gas. In regular service as protective coatings, nickel-aluminum alloys are protected by an oxide scale, but in case of oxide scale spallation, the alloy surface may be directly exposed to the reactive gas environment and vulnerable to metal dusting. By means of density functional theory and thermochemical calculations for both the Ni{sub 3}Al and NiAl surfaces, the conditions under which CO and OH adsorption is to be expected and under which it is inhibited, are mapped out. Because CO and OH are regarded as precursors for nucleating graphite or oxide on the surfaces, phase diagrams for the surfaces provide a simple description of their stability. Specifically, this study shows how the CO and OH coverages depend on the steam to carbon ratio (S/C) in the gas and thereby provide a ranking of the carbon limits on the different surface phases.

  1. Neutron cross section covariances in the resonance region: 52Cr, 56Fe, 58Ni

    SciTech Connect

    Oblozinsky, P.; Cho, Y.-S.; Mattoon, C.M.; Mughabghab, S.F.

    2010-08-03

    We evaluated covariances for neutron capture and elastic scattering cross sections on major structural materials, {sup 52}Cr, {sup 56}Fe and {sup 58}Ni, in the resonance region which extends beyond 800 keV for each of them. Use was made of the recently developed covariance formalism based on kernel approximation along with data in the Atlas of Neutron Resonances. The data of most interest for AFCI applications, elastic scattering cross section uncertainties at energies above about few hundred keV, are on the level of about 12% for {sup 52}Cr, 7-8% for {sup 56}Fe and 5-6% for {sup 58}Ni.

  2. Magnetic Structure of NiCr2O4 Studied by Neutron Scattering and Magnetization Measurements

    NASA Astrophysics Data System (ADS)

    Tomiyasu, Keisuke; Kagomiya, Isao

    2004-09-01

    The magnetic ordering of the normal spinel ferrimagnet NiCr2O4 below TC = 74 K was reinvestigated by neutron scattering and magnetization measurements on a powder specimen. We found another magnetic transition at TS = 31 K besides TC in both experiments. The ordering of a ferrimagnetic (longitudinal) component and that of an antiferromagnetic (transverse) component occur at TC and TS, separately. A new magnetic structure model of NiCr2O4 below TS with a spontaneous magnetization of about 0.3 μB/formula is proposed based on experimental neutron scattering intensity.

  3. Mechanical properties and strengthening of a Ni-25Mo-8Cr alloy containing Ni{sub 2}(Mo,Cr) precipitates

    SciTech Connect

    Kumar, M.; Vasudevan, V.K.

    1996-12-01

    The mechanical properties and mechanisms of deformation and strengthening of Haynes Alloy 242{sup tm}, a nominal Ni-25Mo-8Cr (in wt%) containing Ni{sub 2}(Mo,Cr) precipitates in a face-centered cubic matrix, are reported. Both solution treated, as well as aged samples (550--750 C, 1--1,200 h) were deformed to permanent strains of 1 and 6% in compression and to failure in tension. The deformation structures were observed by transmission electron microscopy. A two-fold increase in strength and tremendous strain hardening are observed as the short-range (SRO) to long-range ordering (LRO) transformation proceeds, although ductility remains high even in well-aged samples. Major contribution to strengthening and strain hardening comes from the precipitation of a high volume fraction of Ni{sub 2}(Mo,Cr) precipitates, with hardening in the solution treated samples and those aged for short periods being associated with the presence of SRO in the matrix. A transition in deformation mode, from glide of unit dislocations in planar arrays to profuse twinning, is observed as a function of aging time and imposed strain, twinning being observed in samples containing Ni{sub 2}(Mo,Cr) precipitates. A semi-quantitative model developed on the basis of precipitate size and mode of deformation (shearing, twinning, bypassing) is able to satisfactorily account for this transition. A presentation and discussion of these results, as well as those of the mechanisms of strengthening and strain hardening, are provided.

  4. Effect of Cr and Cu addition on corrosion behavior of Ni-Ti alloys.

    PubMed

    Iijima, M; Endo, K; Ohno, H; Mizoguchi, I

    1998-03-01

    The corrosion behavior of three Ni-Ti alloys with compositions as commercial super-elastic orthodontic wires was investigated using polished plate specimens. Corrosion resistance was estimated by potentiodynamic polarization measurement in 0.9% NaCl and 1% lactic acid solutions and analysis of released metals by atomic absorption spectrophotometry. The influence of Cr and Cu addition on the structure of the surface oxide film was examined by X-ray photoelectron spectroscopy (XPS). Addition of 0.19 at% Cr had little effect on the structure of the oxide films and the corrosion resistance of the Ni-Ti alloys. For Ni-Ti-5Cu-0.3Cr alloy, the metallic Cu was enriched at the alloy/oxide film interface, resulting in increased susceptibility to pitting corrosion above +1000 mV. However, the passive current density and the amount of released Ni were not significantly increased by the addition of Cu. The study showed that small amounts of Cr and Cu added to change the super-elastic characteristics do not change the corrosion resistance of the Ni-Ti alloy freely immersed in simulated physiological environments. PMID:9663060

  5. Optimizing NiCr and FeCr HVOF Coating Structures for High Temperature Corrosion Protection Applications

    NASA Astrophysics Data System (ADS)

    Oksa, M.; Metsäjoki, J.

    2015-02-01

    In order to achieve a desired dense structure for coatings employed in high temperature corrosion conditions, thermal spray process optimization with diagnostic tools can be applied. In this study, NiCr (51Ni-46Cr-2Si-1Fe) and FeCr (Fe-19Cr-9W-7Nb-4Mo-5B-2C-2Si-1Mn) powders were sprayed with HVOFGF (gas-fueled) and HVOFLF (liquid-fueled) systems, and the spray processes were monitored with diagnostic tools, including SprayWatch for measuring the temperature and velocity of the spray stream, and in situ coating property (ICP measurement) for measuring the stress state. Various spray parameters were applied to attain the best coating characteristics for high temperature applications. Selected coatings were exposed to high temperature corrosion conditions both in laboratory and actual power plant. The coatings were analyzed by microscopic means and mechanical testing. The application of process-structure-properties-performance methodology with the process monitoring, analysis of the coating characteristics, and results of corrosion performance are presented in this paper.

  6. Radiation effects on interface reactions of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni)

    NASA Astrophysics Data System (ADS)

    Shao, Lin; Chen, Di; Wei, Chaochen; Martin, Michael S.; Wang, Xuemei; Park, Youngjoo; Dein, Ed; Coffey, Kevin R.; Sohn, Yongho; Sencer, Bulent H.; Rory Kennedy, J.

    2015-01-01

    We study the effects of radiation damage on interdiffusion and intermetallic phase formation at the interfaces of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni) diffusion couples. Magnetron sputtering is used to deposit thin films of Fe, Fe + Cr, or Fe + Cr + Ni on U substrates to form the diffusion couples. One set of samples are thermally annealed under high vacuum at 450 °C or 550 °C for one hour. A second set of samples are annealed identically but with concurrent 3.5 MeV Fe++ ion irradiation. The Fe++ ion penetration depth is sufficient to reach the original interfaces. Rutherford backscattering spectrometry analysis with high fidelity spectral simulations is used to obtain interdiffusion profiles, which are used to examine differences in U diffusion and intermetallic phase formation at the buried interfaces. For all three diffusion systems, Fe++ ion irradiations enhance U diffusion. Furthermore, the irradiations accelerate the formation of intermetallic phases. In U/Fe couples, for example, the unirradiated samples show typical interdiffusion governed by Fick's laws, while the irradiated ones show step-like profiles influenced by Gibbs phase rules.

  7. Radiation effects on interface reactions of U/Fe, U/(Fe+Cr), and U/(Fe+Cr+Ni)

    SciTech Connect

    Shao, Lin; Chen, Di; Wei, Chaochen; Martin, Michael S.; Wang, Xuemei; Park, Youngjoo; Dein, Ed; Coffey, Kevin R.; Sohn, Yongho; Sencer, Bulent H.; Rory Kennedy, J.

    2014-10-01

    We study the effects of radiation damage on interdiffusion and intermetallic phase formation at the interfaces of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni) diffusion couples. Magnetron sputtering is used to deposit thin films of Fe, Fe + Cr, or Fe + Cr + Ni on U substrates to form the diffusion couples. One set of samples are thermally annealed under high vacuum at 450 C or 550 C for one hour. A second set of samples are annealed identically but with concurrent 3.5 MeV Fe++ ion irradiation. The Fe++ ion penetration depth is sufficient to reach the original interfaces. Rutherford backscattering spectrometry analysis with high fidelity spectral simulations is used to obtain interdiffusion profiles, which are used to examine differences in U diffusion and intermetallic phase formation at the buried interfaces. For all three diffusion systems, Fe++ ion irradiations enhance U diffusion. Furthermore, the irradiations accelerate the formation of intermetallic phases. In U/Fe couples, for example, the unirradiated samples show typical interdiffusion governed by Fick’s laws, while the irradiated ones show step-like profiles influenced by Gibbs phase rules.

  8. Radiation effects on interface reactions of U/Fe, U/(Fe+Cr), and U/(Fe+Cr+Ni)

    DOE PAGESBeta

    Shao, Lin; Chen, Di; Wei, Chaochen; Martin, Michael S.; Wang, Xuemei; Park, Youngjoo; Dein, Ed; Coffey, Kevin R.; Sohn, Yongho; Sencer, Bulent H.; et al

    2014-10-01

    We study the effects of radiation damage on interdiffusion and intermetallic phase formation at the interfaces of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni) diffusion couples. Magnetron sputtering is used to deposit thin films of Fe, Fe + Cr, or Fe + Cr + Ni on U substrates to form the diffusion couples. One set of samples are thermally annealed under high vacuum at 450 C or 550 C for one hour. A second set of samples are annealed identically but with concurrent 3.5 MeV Fe++ ion irradiation. The Fe++ ion penetration depth is sufficient to reachmore » the original interfaces. Rutherford backscattering spectrometry analysis with high fidelity spectral simulations is used to obtain interdiffusion profiles, which are used to examine differences in U diffusion and intermetallic phase formation at the buried interfaces. For all three diffusion systems, Fe++ ion irradiations enhance U diffusion. Furthermore, the irradiations accelerate the formation of intermetallic phases. In U/Fe couples, for example, the unirradiated samples show typical interdiffusion governed by Fick’s laws, while the irradiated ones show step-like profiles influenced by Gibbs phase rules.« less

  9. Fabrication and properties of functionally graded NiAl/Al2O3 composites

    NASA Technical Reports Server (NTRS)

    Miller, D. P.; Lannutti, J. J.; Noebe, R. D.

    1993-01-01

    A modified sedimentation process was used in the production of a functionally gradient material (FGM), NiAl/Al2O3. A simple finite element model was used to guide our design and fabrication efforts by estimating residual stress states as a function of composite structure. This approach could lead to tailored designs that enhance or avoid specific residual stress states. Thermal cycling tests were factored into the model to predict time dependent or steady-state internal temperature and stress profiles. Four-point bend tests were conducted to establish the mechanical load-displacement behavior of a single interlayer FGM at room temperature, 800 and 1000 K. Room temperature bend strength of the FGM was 3-4 times that of the base NiAl. At elevated temperatures, composite fracture occurred in a gradual, noncatastrophic mode involving NiAl retardation of a succession of cracks originating in the alumina face.

  10. Chemical separation and mass spectrometry of Cr, Fe, Ni, Zn, and Cu in terrestrial and extraterrestrial materials using thermal ionization mass spectrometry.

    PubMed

    Yamakawa, Akane; Yamashita, Katsuyuki; Makishima, Akio; Nakamura, Eizo

    2009-12-01

    A sequential chemical separation technique for Cr, Fe, Ni, Zn, and Cu in terrestrial and extraterrestrial silicate rocks was developed for precise and accurate determination of elemental concentration by the isotope dilution method (ID). The technique uses a combination of cation-anion exchange chromatography and Eichrom nickel specific resin. The method was tested using a variety of matrixes including bulk meteorite (Allende), terrestrial peridotite (JP-1), and basalt (JB-1b). Concentrations of each element was determined by thermal ionization mass spectrometry (TIMS) using W filaments and a Si-B-Al type activator for Cr, Fe, Ni, and Zn and a Re filament and silicic acid-H3PO4 activator for Cu. The method can be used to precisely determine the concentrations of these elements in very small silicate samples, including meteorites, geochemical reference samples, and mineral standards for microprobe analysis. Furthermore, the Cr mass spectrometry procedure developed in this study can be extended to determine the isotopic ratios of 53Cr/52Cr and 54Cr/52Cr with precision of approximately 0.05epsilon and approximately 0.10epsilon (1epsilon = 0.01%), respectively, enabling cosmochemical applications such as high precision Mn-Cr chronology and investigation of nucleosynthetic isotopic anomalies in meteorites. PMID:19886654

  11. Cyclic Oxidation of Single-Crystal NiAl-X Alloys

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.; Barrett, Charles A.; Darolia, Ram

    1999-01-01

    Several single-crystal NiAl-X alloys (X = Hf, Ti, Cr, Ga) were cyclically oxidized at 1000 C for up to 1000 1-hr cycles. The alloys all showed protective, adherent alpha-Al2O3 scale formation with positive weight change behavior throughout the test. There was no clear correlation between the composition of the various alloys and the specific weight gain although the ranking by weight change was relatively consistent for two duplicate series of samples. The presence of Hf (0.5 - 0.8 at.%) resulted in the internal formation of Al2O3/HfO2 "stringers." Diffusion of Hf to the growing oxide stringers resulted in the development of a near-surface layer depleted of these precipitates.

  12. Exploring artificial layered heterostructures of LaM'O3/LaM''O3 (M'M''= NiCr, FeCr and NiV).

    NASA Astrophysics Data System (ADS)

    Liu, J.; Kareev, M.; Freeland, J. W.; Kareev, A.; Lee, H. N.; Chakhalian, J.

    2008-03-01

    Digital synthesis of atomically sharp interfaces between strongly correlated electron systems can provide a template to build completely new materials. Here we present our results on magnetism and electronic structure in LaM'O3/LaM''O3 (M'M''= NiCr, FeCr and NiV) superlattices by using polarized X-ray spectroscopies. Using laser MBE, the (111) and (100) oriented ultra-thin superlattices were grown with alternating layer thicknesses of 1 unit cell. In the bulk, LaMO3 (M=Cr,Fe,V) are antiferromagnetic insulators while LaNiO3 is a paramagnetic metal. The evolution of element specific magnetism and charge at the interface of LFO/LCO, LNO/LVO and LNO/LCO superlattices with temperature and an applied magnetic field will be discussed in detail. The superlattice results will be contrasted to the bulk magnetic properties of the constituent layers. The work has been supported by U.S. DOD-ARO under Contract No. 0402-17291.

  13. Al-augite and Cr-diopside ultramafic xenoliths in basaltic rocks from western United States

    USGS Publications Warehouse

    Wilshire, H.G.; Shervais, J.W.

    1975-01-01

    Ultramafic xenoliths in basalts from the western United States are divided into Al-augite and Cr-diopside groups. The Al-augite group is characterized by Al, Ti-rich augites, comparatively Fe-rich olivine and orthopyroxene, and Al-rich spinel, the Cr-diopside group by Cr-rich clinopyroxene and spinel and by Mg-rich olivine and pyroxenes. Both groups have a wide range of subtypes, but the Al-augite group is dominated by augite-rich varieties, and the Cr-diopside group by olivine-rich lherzolites. ?? 1975.

  14. Effects of hBN Content on the Microstructure and Properties of Atmospheric Plasma-Sprayed NiCr/Cr3C2-hBN Composite Coatings

    NASA Astrophysics Data System (ADS)

    Cao, Yuxia

    2016-04-01

    NiCr/Cr3C2-hBN composite coatings with different contents of hBN were prepared by atmospheric plasma-spray technology. The microstructural, mechanical, and tribological properties of the coatings were systematically investigated. The results show that the flowability and apparent density of NiCr/Cr3C2-hBN composite powders, as well as the microhardness and tensile strength of the NiCr/Cr3C2-hBN composite coating, gradually decrease with the increase of hBN in the composite powders. The addition of hBN is benefit to the friction coefficient of the coatings, but it is positive to the wear rate. When the content of hBN is up to 20%, the friction coefficient of the composite coating is lowest, but the wear rate of the composite coating is highest.

  15. Role of defect coordination environment on point defects formation energies in Ni-Al intermetallic alloys

    NASA Astrophysics Data System (ADS)

    Tennessen, Emrys; Rondinelli, James

    We present a relationship among the point defect formation energies and the bond strengths, lengths, and local coordination environment for Ni-Al intermetallic alloys based on density functional calculations, including Ni3Al, Ni5Al3, NiAl,Ni3Al4, Ni2Al3 and NiAl3. We find the energetic stability of vacancy and anti-site defects for the entire family can be attributed primarily to changes in interactions among first nearest neighbors, owing to spatially localized charge density reconstructions in the vicinity of the defect site. We also compare our interpretation of the local coordination environment with a DFT-based cluster expansion and discuss the performance of each approach in predicting defect stability in the Ni-Al system.

  16. Study on Optical Properties of Nanostructured NiCr Film Prepared by Magnetron Sputtering and RIE for Terahertz Applications

    NASA Astrophysics Data System (ADS)

    Gou, Jun; Wang, Jun; Li, Weizhi; Gu, Deen; Jiang, Yadong

    2015-09-01

    Nanoscale NiCr thin film has been proven to be an effective metallic terahertz (THz) absorption layer. To prepare NiCr film with a small thickness and enhanced THz absorption, a combined process of magnetron sputtering and reactive ion etching (RIE) is suggested to obtain nanostructured NiCr film with different thicknesses by precise control of process parameters and etch time. Optical characteristics tests show that both transmission and reflection of NiCr film are weakened by the RIE treatment. NiCr absorption layer is prepared in 80 × 60 infrared focal plane arrays (IRFPAs) by a combination of substrate modification process and RIE thinning process. THz absorption is effectively enhanced by RIE processes applied to the dielectric substrate and NiCr film, which generates nanoscale structures on upper and lower surfaces of NiCr absorption film for an increased specific surface area. The noise equivalent power (NEP) of the THz detection unit achieves 162.8 pW/Hz1/2, which is suitable for the application of active THz imaging. The results indicate that nanostructured NiCr film is an effective THz absorption layer for applications in thermal sensing and its absorption performance can be further improved by RIE.

  17. A Study on the Cyclic Oxidation Behavior of Detonation-Gun-Sprayed Ni-5Al Coatings on Inconel-718 at 900 °C

    NASA Astrophysics Data System (ADS)

    Saladi, Sekar; Menghani, Jyoti; Prakash, Satya

    2014-12-01

    Cyclic oxidation behavior of detonation-gun-sprayed Ni-5Al coating on Inconel-718 is discussed in the present study. Oxidation studies were carried out on both bare and coated superalloy substrates in air at 900 °C for 100 cycles. The thermogravimetric technique was used to establish kinetics of oxidation. X-ray diffraction, FESEM/EDAX, and x-ray mapping techniques were used to analyze the oxidation products of bare and coated samples. The weight gain of bare superalloy was higher than the Ni-5Al-coated superalloy. Both bare and Ni-5Al-coated superalloys followed nearly parabolic oxidation behavior. The Ni-5Al coating was able to reduce the overall weight gain by 26.2% in comparison with bare superalloy in the given environment. The better oxidation resistance of Ni-5Al coating may be due the formation of protective oxides phases such as NiO, Al2O3, and NiAl2O4 on the oxidized coating and Cr2O3 at the coating-substrate interface. The Ni-5Al coatings obtained from detonation-gun-spraying process showed very little porosity and low surface roughness values.

  18. Local structure study of Fe dopants in Ni-deficit Ni3Al alloys

    DOE PAGESBeta

    V. N. Ivanovski; Umicevic, A.; Belosevic-Cavor, J.; Lei, Hechang; Li, Lijun; Cekic, B.; Koteski, V.; Petrovic, C.

    2015-08-24

    We found that the local electronic and magnetic structure, hyperfine interactions, and phase composition of polycrystalline Ni–deficient Ni 3-x FexAl (x = 0.18 and 0.36) were investigated by means of 57 Fe Mössbauer spectroscopy. The samples were characterized by X–ray diffraction and magnetization measurements. The ab initio calculations performed with the projector augmented wave method and the calculations of the energies of iron point defects were done to elucidate the electronic structure and site preference of Fe doped Ni 3 Al. Moreover, the value of calculated electric field gradient tensor Vzz=1.6 1021Vm-2 matches well with the results of Mössbauer spectroscopymore » and indicates that the Fe atoms occupy Ni sites.« less

  19. Electron energy loss spectroscopy of CH/sub 3/N/sub 2/CH/sub 3/ adsorbed on Ni(100), Ni(111), Cr(100), Cr(111)

    SciTech Connect

    Schulz, M.A.

    1985-07-01

    A study of the adsorption of CH/sub 3/N/sub 2/CH/sub 3/ on Ni(100), Ni(111), Cr(100), and Cr(111) using high resolution electron energy loss spectroscopy (EELS) is presented. Under approximately the same conditions of coverage, the vibrational spectra of CH/sub 3/N/sub 2/CH/sub 3/ on these four surfaces are quite distinct from one another, implying that the CH/sub 3/N/sub 2/CH/sub 3/-substrate interaction is very sensitive to the physical and electronic structure of each surface. In addition to the room temperature studies, the evolution of surface species on the Ni(100) surface in the temperature range 300 to 425 K was studied. Analysis of the Ni(100) spectra indicates that molecular adsorption, probably through the N lone pair, occurs at room temperature. Spectra taken after annealing the CH/sub 3/N/sub 2/CH/sub 3/-Ni(100) surfaces indicate that CH and CN bond scission occurred at the elevated temperatures. Decomposition of CH/sub 3/N/sub 2/CH/sub 3/ takes place on the Ni(111), Cr(100), and Cr(111) surfaces at room temperature, as evidenced by the intensity of the carbon-metal stretch in the corresponding spectra. Possible identities of coadsorbed dissociation products are considered. The stable coverage of surface species on all four surfaces at 300 K is less than one monolayer. A general description of an electron energy loss (EEL) spectrometer is given. Followed by a more specific discussion of some recent modifications to the EEL monochromator assembly used in this laboratory. Both the previous configuration of our monochromator and the new version are briefly described, as an aid to understanding the motivation for the changes as well as the differences in operation of the two versions. For clarity, the new monochromator design is referred to as variable pass, while the previous design is referred to as double pass. A modified tuning procedure for the new monochromator is also presented. 58 refs., 11 figs.

  20. Microstructure and mechanical properties of sputter deposited Ni/Ni3Al multilayer films at elevated temperature

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Feng, Kai; Li, Zhuguo; Lu, Fenggui; Huang, Jian; Wu, Yixiong

    2016-08-01

    Nano-structured Ni/Ni3Al multilayer was prepared by magnetron sputtering, with individual layer thicknesses h varying from 10 to 160 nm. The microstructure and hardness of Ni/Ni3Al multilayer were investigated by X-ray diffraction, transmission electron microscopy and nanoindentation. The results show that the hardness increases with decreasing h for as-deposited and 500 °C annealed multilayers. When annealed at 700 °C, the hardness approach a peak value at h = 40 nm with followed by softening at smaller h. The influence of individual layer thickness, grain size as well as formation of ordered Ni3Al on strengthening mechanisms of Ni/Ni3Al multilayers at elevated temperature are discussed.

  1. Discontinuous coarsening behavior of Ni(2)MnAl intermetallic compound during isothermal aging treatment of Fe-Mn-Ni-Al alloys.

    PubMed

    Heo, Yoon-Uk; Takeguchi, Masaki; Furuya, Kazuo; Lee, Hu-Chul

    2010-08-01

    The discontinuous reaction of the Ni(2)MnAl intermetallic phase was investigated during the aging of a solution-treated Fe-8.3Mn-8.2Ni-4.2Al alloy. During aging, Ni(2)MnAl lamellae formed at the prior austenite grain boundaries and twin boundaries and grew into the neighboring grains. The presence of continuously precipitated fine Ni(2)MnAl particles before the growth of the discontinuously precipitated lamellae was confirmed by dark-field transmission electron microscopy, and it was concluded that the present reaction is a type of discontinuous coarsening process, alpha' + Ni(2)MnAl (continuous precipitation) --> alpha + Ni(2)MnAl (discontinuous coarsening). The chemical driving force and the reduction of the total coherent strain energy were suggested to be the driving force for the discontinuous coarsening reaction. PMID:20551447

  2. High-temperature oxidation behavior of a wrought Ni-Cr-W-Mn-Si-La alloy

    SciTech Connect

    Tawancy, H.M.

    1996-04-01

    An investigation was carried out to study the kinetics and products of oxidation of a wrought Ni-Cr-W-Mn-Si-La alloy at temperatures in the range of 950 to 1150{degrees}C. Oxidation kinetics were evaluated from measurements of weight change, metal loss, and internal penetration. Analytical electron microscopy, scanning electron microscopy, electron probe microanalysis, and X-ray diffraction were used to characterize the scale microstructure. Initially, La was observed to segregate within a surface layer of about 5 {mu}m thick, which promoted selective oxidation of Cr and Mn. Oxidation kinetics were found to follow a parabolic-rate law with an activation energy of about 232 kJ/mol. During steady-state oxidation, the scale consisted of an inner adherent layer of {alpha}-Cr{sub 2}O{sub 3} modified by the presence of La and Si, and shielded by an outer layer of MnCr{sub 2}O{sub 4}. Most of the La was segregated to grain boundaries of the {alpha}-Cr{sub 2}O{sub 3} scale, however, Si was homogeneously distributed. It was concluded that the characteristic oxidation resistance of the alloy was related to the synergistic effects of Ni and Cr and to the effective minor additions of La, Si, and Mn; however, the useful life of the scale was limited by rupture and surface depletion in Cr, leading to accelerated internal oxidation.

  3. Microstructure and phase evolution in laser clad chromium carbide-NiCrMoNb

    NASA Astrophysics Data System (ADS)

    Venkatesh, L.; Samajdar, I.; Tak, Manish; Doherty, Roger D.; Gundakaram, Ravi C.; Prasad, K. Satya; Joshi, S. V.

    2015-12-01

    Microstructural development in laser clad layers of Chromium carbide (CrxCy)-NiCrMoNb on SA 516 steel has been investigated. Although the starting powder contained both Cr3C2 and Cr7C3, the clad layers showed only the presence of Cr7C3. Microtexture measurements by electron back scattered diffraction (EBSD) revealed primary dendritic Cr7C3 with Ni rich FCC metallic phase being present in the interdendritic spaces. Further annealing of the laser clad layers and furnace melting of the starting powder confirmed that Cr7C3 is the primary as well as stable carbide phase in this multi component system. Increase in laser power and scanning speed progressively reduced carbide content in the laser clad layers. Increased scanning speed, which enhances the cooling rate, also led to reduction in the secondary arm spacing (λ2) of the Cr7C3 dendrites. The clad layer hardness increased with carbide content and with decreased dendrite arm spacing.

  4. Numerical Prediction of the Thermodynamic Properties of Ternary Al-Ni-Pd Alloys

    NASA Astrophysics Data System (ADS)

    Zagula-Yavorska, Maryana; Romanowska, Jolanta; Kotowski, Sławomir; Sieniawski, Jan

    2016-01-01

    Thermodynamic properties of ternary Al-Ni-Pd system, such as exGAlNPd, µAl(AlNiPd), µNi(AlNiPd) and µPd(AlNiPd) at 1,373 K, were predicted on the basis of thermodynamic properties of binary systems included in the investigated ternary system. The idea of predicting exGAlNiPd values was regarded as calculation of values of the exG function inside a certain area (a Gibbs triangle) unless all boundary conditions, that is values of exG on all legs of the triangle are known (exGAlNi, exGAlPd, exGNiPd). This approach is contrary to finding a function value outside a certain area, if the function value inside this area is known. exG and LAl,Ni,Pd ternary interaction parameters in the Muggianu extension of the Redlich-Kister formalism were calculated numerically using the Excel program and Solver. The accepted values of the third component xx differed from 0.01 to 0.1 mole fraction. Values of LAlNiPd parameters in the Redlich-Kister formula are different for different xx values, but values of thermodynamic functions: exGAlNiPd, µAl(AlNiPd), µNi(AlNiPd) and µPd(AlNiPd) do not differ significantly for different xx values. The choice of xx value does not influence the accuracy of calculations.

  5. Kinetics of NiO and NiCl2 hydrogen reduction as precursors and properties of produced Ni/Al2O3 and Ni-Pd/Al2O3 catalysts.

    PubMed

    Sokić, Miroslav; Kamberović, Željko; Nikolić, Vesna; Marković, Branislav; Korać, Marija; Anđić, Zoran; Gavrilovski, Milorad

    2015-01-01

    The objects of this investigation were the comparative kinetic analysis of the NiO and NiCl2 reduction by hydrogen during an induction period and elimination of the calcination during the synthesis of Ni/Al2O3 catalysts. The effect of temperature and time on NiO and NiCl2 reduction degrees was studied. Avrami I equation was selected as the most favorable kinetic model and used to determine activation energy of the NiO and NiCl2 reduction for the investigated temperature range (623-923 K) and time intervals (1-5 minutes). The investigation enabled reaching conclusions about the reaction ability and rate of the reduction processes. Afterward, Ni/Al2O3 catalysts were obtained by using oxide and chloride precursor for Ni. The catalysts were supported on alumina-based foam and prepared via aerosol route. Properties of the samples before and after low-temperature hydrogen reduction (633 K) were compared. Obtained results indicated that the synthesis of Ni/Al2O3 catalysts can be more efficient if chloride precursor for Ni is directly reduced by hydrogen during the synthesis process, without the calcination step. In addition, Ni-Pd/Al2O3 catalysts with different metal content were prepared by using chloride precursors. Lower reduction temperature was utilized and the chlorides were almost completely reduced at 533 K. PMID:25789335

  6. Kinetics of NiO and NiCl2 Hydrogen Reduction as Precursors and Properties of Produced Ni/Al2O3 and Ni-Pd/Al2O3 Catalysts

    PubMed Central

    Sokić, Miroslav; Kamberović, Željko; Nikolić, Vesna; Marković, Branislav; Korać, Marija; Anđić, Zoran; Gavrilovski, Milorad

    2015-01-01

    The objects of this investigation were the comparative kinetic analysis of the NiO and NiCl2 reduction by hydrogen during an induction period and elimination of the calcination during the synthesis of Ni/Al2O3 catalysts. The effect of temperature and time on NiO and NiCl2 reduction degrees was studied. Avrami I equation was selected as the most favorable kinetic model and used to determine activation energy of the NiO and NiCl2 reduction for the investigated temperature range (623–923 K) and time intervals (1–5 minutes). The investigation enabled reaching conclusions about the reaction ability and rate of the reduction processes. Afterward, Ni/Al2O3 catalysts were obtained by using oxide and chloride precursor for Ni. The catalysts were supported on alumina-based foam and prepared via aerosol route. Properties of the samples before and after low-temperature hydrogen reduction (633 K) were compared. Obtained results indicated that the synthesis of Ni/Al2O3 catalysts can be more efficient if chloride precursor for Ni is directly reduced by hydrogen during the synthesis process, without the calcination step. In addition, Ni-Pd/Al2O3 catalysts with different metal content were prepared by using chloride precursors. Lower reduction temperature was utilized and the chlorides were almost completely reduced at 533 K. PMID:25789335

  7. Gain measurements and average power capabilities of Cr(3+):LiSrAlF6

    NASA Astrophysics Data System (ADS)

    Hanson, F.; Bendall, C.; Poirier, P.

    1993-09-01

    Gain for flash-lamp-pumped Cr:LiSrAlF6 and Cr:Li(Sr(1-x),Ca(x))AlF6 from 790 to 1000 nm is reported. For Cr:LiSrAlF6 thermal fracture occurred at heat loadings of 4.5 W/cm and about 6 W/sq cm in the rod and slab geometry, respectively. Excited-state upconversion losses were evident in the slabs at high pump energy.

  8. on the High-Temperature Performance of Ni-Based Welding Material NiCrFe-7

    NASA Astrophysics Data System (ADS)

    Mo, Wenlin; Lu, Shanping; Li, Dianzhong; Li, Yiyi

    2014-10-01

    The effects of M 23C6 ( M = Cr, Fe) on the high-temperature performance of the NiCrFe-7 welding rods and weld metals were studied by high-temperature tensile tests and microstructure analysis. M 23C6 at the grain boundaries (GBs) has a cube-on-cube coherence with one grain in the NiCrFe-7 weld metals, and the adjacent M 23C6 has the coherence relationship with the same grain. The grain with a coherent M 23C6 has a Cr-depletion region. The number and size of M 23C6 particles can be adjusted by heat treatment and alloying. There are two temperatures [ T E1: 923 K to 1083 K (650 °C to 810 °C) and T E2: 1143 K to 1203 K (870 °C to 930 °C)] at which the GBs and grains of the NiCrFe-7 welding rod have equal strength during the high-temperature tensile test. When the temperatures are between T E1 and T E2, the strength of the GBs is lower than that of the grains, and the tensile fractures are intergranular. When the temperatures are below T E1 or over T E2, the strength of the GBs is higher than that of the grains, and the tensile fractures are dimples. M 23C6 precipitates at the GBs, which deteriorates the ductility of the welding rods at temperature between T E1 and T E2. M 23C6 aggravates ductility-dip-cracking (DDC) in the weld metals. The addition of Nb and Ti can form MX ( M = Ti, Nb, X = C, N), fix C in grain, decrease the initial precipitation temperature of M 23C6, and mitigate the precipitation of M 23C6, which is helpful for minimizing DDC in the weld.

  9. Immiscibility in the NiFe2O4-NiCr2O4 Spinel Binary

    SciTech Connect

    S Ziemniak

    2004-08-13

    The solid solution behavior of the Ni(Fe{sub 1-n}Cr{sub n}){sub 2}O{sub 4} spinel binary is investigated in the temperature range 400-1200 C. Non-ideal solution behavior, as exhibited by non-linear changes in lattice parameter with changes in n, is observed in a series of single-phase solids air-cooled from 1200 C. Air-annealing for one year at 600 C resulted in partial phase separation in a spinel binary having n = 0.5. Spinel crystals grown from NiO, Fe{sub 2}O{sub 3} and Cr{sub 2}O{sub 3} reactants, mixed to give NiCrFeO{sub 4}, by Ostwald ripening in a molten salt solvent, exhibited single phase stability down to about 750 C (the estimated consolute solution temperature, T{sub cs}). A solvus exists below T{sub cs}. The solvus becomes increasingly asymmetric at lower temperatures and extrapolates to n values of 0.2 and 0.7 at 300 C. The extrapolated solvus is shown to be consistent with that predicted using a primitive regular solution model in which free energies of mixing are determined entirely from changes in configurational entropy at room temperature.

  10. Evaluation of Ceria-Added Cr3C2-25(NiCr) Coating on Three Superalloys under Simulated Incinerator Environment

    NASA Astrophysics Data System (ADS)

    Mudgal, Deepa; Singh, Surendra; Prakash, Satya

    2015-02-01

    Cr3C2-25(NiCr) coating is widely used in wear, erosion and corrosion applications. In the present study, D-gun-sprayed Cr3C2-25(NiCr) coatings with and without 0.4 wt.% ceria incorporated were deposited on Superni 718, Superni 600 and Superco 605 substrates. Hot-corrosion runs were conducted in 40 %Na2SO4-40 %K2SO4-10 %NaCl-10 %KCl environment at 900 °C for 100 cycles. Corrosion kinetics was monitored using weight gain measurements. Characterization of corrosion products was carried out by field-emission scanning electron microscopy (FESEM)/energy-dispersive spectroscopy (EDS) and x-ray diffraction (XRD) techniques. It was observed that Cr3C2-25(NiCr) coating with and without added ceria deposited on both of the Ni-based alloys showed resistance to corrosion under the given environment. Addition of ceria enhanced the adherence of the oxide to the coating during the corrosion run and reduced the overall weight gain. However, Cr3C2-25(NiCr)-coated Superco 605 did not perform satisfactorily under this environment.

  11. Monitoring of deformation induced microcracking in polycrystalline NiAl

    SciTech Connect

    Wanner, A.; Schietinger, B.; Bidlingmaier, T.; Zalkind, H.; Arzt, E.

    1995-08-01

    Microcracking in polycrystalline near-stoichiometric NiAl produced by room temperature plastic deformation under uniaxial compression was investigated by means of optical microscopy, velocity of sound measurements, and acoustic emission monitoring. Results show that strains greater than 2% are required to produce microcrack populations which can be evaluated by microscopical investigation or velocity of sound measurements. However, acoustic emission monitoring during compression testing indicates that microcracking starts at about 0.7% compressive plastic strain which is identical with the typical tensile fracture strain for NiAl. Thus it is concluded that there is little or no stable microcracking prior to failure in tension. Acoustic emission results show also that the process of microcracking does not primarily occur during the applied compressive deformation. A considerable fraction of the microcracking takes place during the quasi-elastic unloading following deformation.

  12. Weak-beam imaging of dissociated dislocations in HVEM-irradiated Fe-Ni-Cr alloys

    SciTech Connect

    King, S.L.; Jenkins, M.L.; Kirk, M.A.; English, C.A.

    1992-06-01

    We report here on studies by weak-beam electron microscopy of the evolution of microstructures at and near preexisting line dislocations in a number of Fe-Ni-Cr alloys under electronirradiation in a high-voltage electron microscope (HVEM). The detailed observations are discussed in terms of dislocation climb mechanisms in these materials and a model based on interstitial pipe diffusion.

  13. Characterization of Ni-Cr alloys using different casting techniques and molds.

    PubMed

    Chen, Wen-Cheng; Teng, Fu-Yuan; Hung, Chun-Cheng

    2014-02-01

    This study differentiated the mechanical properties of nickel-chromium (Ni-Cr) alloys under various casting techniques (different casting molds and casting atmospheres). These techniques were sampled by a sand mold using a centrifugal machine in ambient air (group I) and electromagnetic induction in an automatic argon castimatic casting machine (group II). The specimen casting used a graphite mold by a castimatic casting machine (group III). The characteristics of the Ni-Cr alloys, yield and ultimate tensile strength, bending modulus, microhardness, diffraction phase, grindability, ability to spring back, as well as ground microstructure and pattern under different casting conditions were evaluated. The group III specimens exhibited the highest values in terms of strength, modulus, hardness, and grindability at a grind rate of 500 rpm. Moreover, group III alloys exhibited smaller grain sizes, higher ability to spring back, and greater ductility than those casted by sand investment (groups I and II). The main factor, "casting mold," significantly influenced all mechanical properties. The graphite mold casting of the Ni-Cr dental alloys in a controlled atmosphere argon casting system provided an excellent combination of high mechanical properties and good ability to spring back, and preserved the ductile properties for application in Ni-Cr porcelain-fused system. The results can offer recommendations to assist a prosthetic technician in selecting the appropriate casting techniques to obtain the desired alloy properties. PMID:24411373

  14. [Ultra-structural study of Ni-Cr alloys used in joint prosthesis].

    PubMed

    Bennani, A; Amine, M; Ezzahi, A; Chafii, A; Eladioui, S

    2014-12-01

    Ni-Cr alloys used in denture set, which have excellent mechanical properties, have a chemical and electrochemical inertia that depends on their composition and their microstructure. The objective of our work was to study the ultrastructure of the Ni-Cr alloy exposed to a free corrosion and a chemical analysis of surface depending on its composition. For this, five electrodes Ni-Cr alloy were prepared at the prosthesis laboratory by varying their composition. An analysis of the ultrastructure of the samples made by Scanning Electron Microscopy (SEM) samples was performed as well as a chemical analysis of their spectra. Prior to any manipulation, analysis by SEM of electrode number 5 (100% new metal) shows an altered surface. The electrode 3 (75% new metal) also presents an uneven surface. After a week in a free corrosion in Meyer solution at pH = 6.5, the electrode 5 shows a widespread intergranular and pitting corrosion. The same electrode 3 (75% new metal) after one week immersion in Ringer's solution at pH 7.9, shows a widespread intergranular and pitting corrosion. After electrochemical testing in Ringer's solution at pH 5, the SEM for electrode 1 (100% recovered metal) shows a very rugged structure with an important crevice corrosion. The composition and terms of shaping the Ni-Cr alloy influence its microstructure and at the same time its electrochemical behavior. PMID:25980097

  15. Chemical compatibility of uranium carbides with Cr-Fe-Ni alloys

    SciTech Connect

    Beahm, E.C.; Culpepper, C.A.

    1981-08-01

    This paper discusses the chemical compatibility of uranium carbides and Cr-Fe-Ni alloys, which has been evaluated by thermodynamic modeling and experimental phase studies. Two reaction temperatures, 973 and 1273 K, were used to simulate normal and overtemperature operation of advanced liquid-metal fast breeder reactor fuel-cladding couples. 27 refs.

  16. Evolution of oxide scale on a Ni-Mo-Cr alloy at 900 deg. C

    SciTech Connect

    Ul-Hamid, A. . E-mail: anwar@kfupm.edu.sa; Mohammed, A.I.; Al-Jaroudi, S.S.; Tawancy, H.M.; Abbas, N.M.

    2007-01-15

    The cyclic oxidation behavior of a Ni-Mo-Cr alloy was studied in air at 900 deg. C for exposure periods of up to 1000 h. The morphology, microstructure and composition of the oxide scale was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. Oxidation kinetics was determined by weight gain measurements. The results show that steady state oxidation was achieved within 1 h of exposure. During transient oxidation, the alloy grain boundaries intersecting the alloy surface became depleted in Ni and enriched in Mo and Cr. The scale initially formed at the surface was NiO which grew outwardly. However, a protective Cr{sub 2}O{sub 3} layer developed, rapidly retarding the rate of oxidation. Formation of NiMoO{sub 4} was also observed. The presence of Mo in the alloy facilitated the formation of a Cr{sub 2}O{sub 3} layer at an early stage of oxidation. The alloy exhibited considerable oxide spalling during prolonged exposure.

  17. Structural transition of spinel compound NiCr2O4 at ferrimagnetic transition temperature

    NASA Astrophysics Data System (ADS)

    Ishibashi, H.; Yasumi, T.

    Magnetic properties and crystal structure of spinel compound NiCr2O4 have been investigated by magnetization and high-resolution X-ray powder diffraction measurements. The structural transition from tetragonal to orthorhombic symmetry was observed at ferrimagnetic transition temperature. This crystal distortion is related to the magnetic ordering of ferrimagnetic component.

  18. Systematics of Ni, Co, Cr and V in Olivine from Planetary Melt Systems: Martian Basalts

    NASA Technical Reports Server (NTRS)

    Herd, C. D. K.; Jones, J. H.; Shearer, C. K.; Papike, J. J.

    2001-01-01

    Secondary Ion Mass Spectrometry (SIMS) data for Ni, Co, Cr, and V in olivine in martian basalts is compared to data from lunar and terrestrial basalts. We use experimentally-derived and published D values to calculate as-yet unsampled, olivine-bearing, non-cumulus melt compositions. Additional information is contained in the original extended abstract.

  19. Third element effect in the surface zone of Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Airiskallio, E.; Nurmi, E.; Heinonen, M. H.; Väyrynen, I. J.; Kokko, K.; Ropo, M.; Punkkinen, M. P. J.; Pitkänen, H.; Alatalo, M.; Kollár, J.; Johansson, B.; Vitos, L.

    2010-01-01

    The third element effect to improve the high temperature corrosion resistance of the low-Al Fe-Cr-Al alloys is suggested to involve a mechanism that boosts the recovering of the Al concentration to the required level in the Al-depleted zone beneath the oxide layer. We propose that the key factor in this mechanism is the coexistent Cr depletion that helps to maintain a sufficient Al content in the depleted zone. Several previous experiments related to our study support that conditions for such a mechanism to be functional prevail in real oxidation processes of Fe-Cr-Al alloys.

  20. Compression and Tensile Creep of Binary NiAl

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.

    2005-01-01

    Compression creep and long term tensile creep studies were conducted on cast and extruded binary NiAl in the temperature range 700-1200 K with the objectives of characterizing and understanding the creep mechanisms. Inverse and normal primary creep curves were observed in both compression and tension creep depending on stress and temperature although an asymmetrical response was observed under these two stress states. It was concluded that the primary creep of NiAl is limited by dislocation mobility. The stress exponents, n, for compression and tensile creep were similar varying between about 5 and 14. However, there were significant differences in the stress dependence of the activation energies for compression and tensile creep. The true activation energy for tensile creep, Q(sub c), was constant and equal to about 400 kJ/mol between 20 and 50 MPa but decreased to a constant value of 250 kJ/mol between 50 and 110 MPa. The activation energy was observed to be inversely stress dependent above 110 MPa. In contrast, Q(sub c) = 300 kJ/mol for compression creep was constant between 25 and 70 MPa and inversely dependent on the true stress above 70 MPa. A detailed discussion of the probable dislocation creep mechanisms governing compressive and tensile creep of NiAl is presented. It is concluded that the non-conservative motion of jogs on screw dislocations influenced the nature of the primary creep curves, where the climb of these jogs involves either the next nearest neighbor or the six-jump cycle vacancy diffusion mechanism. The probable natures of the atom-vacancy exchange that occur within the core of an edge dislocation undergoing climb in NiAl are schematically examined.