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Sample records for high ni-cr alloys

  1. 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.

  2. Evaluation of high Ni-Cr-Mo alloys for the construction of sulfur dioxide scrubber plants

    NASA Astrophysics Data System (ADS)

    Rajendran, N.; Rajeswari, S.

    1996-02-01

    Corrosion in wet lime/limestone systems used for flue gas desulfurization in thermal power plants is of great concern. The frequent variations in acidity and in chloride and fluoride ion concentrations experienced by such systems pose a serious threat to the materials of construction. Currently used materials mostly type 316L stainless steel often fail to meet their life expectancy. The present study evaluates the performance of advanced Ni- Cr- Mo alloys 59 and C- 276 in a simulated sulfur dioxide scrubber environment. Accelerated tests showed that high Ni- Cr- Mo alloys have little tendency to leach metal ions such as chromium, nickel, and molybdenum at different impressed potentials. Scanning electron microscopy was used to examine the morphology of pitting attack.

  3. 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.

  4. Investigation of FeNiCrWMn - a new high entropy alloy

    NASA Astrophysics Data System (ADS)

    Buluc, G.; Florea, I.; Bălţătescu, O.; Florea, R. M.; Carcea, I.

    2015-11-01

    The term of high entropy alloys started from the analysis of multicomponent alloys, which were produced at an experimental level since 1995 by developing a new concept related to the development of metallic materials. Recent developments in the field of high-entropy alloys have revealed that they have versatile properties like: ductility, toughness, hardness and corrosion resistance [1]. Up until now, it has been demonstrated that the explored this alloys are feasible to be synthesized, processed and analyzed contrary to the misunderstanding based on traditional experiences. Moreover, there are many opportunities in this field for academic studies and industrial applications [1, 2]. As the combinations of composition and process for producing high entropy alloys are numerous and each high entropy alloy has its own microstructure and properties to be identified and understood, the research work is truly limitless. The novelty of these alloys consists of chemical composition. These alloys have been named high entropy alloys due to the atomic scale mixing entropies higher than traditional alloys. In this paper, I will present the microscopy and the mechanical properties of high entropy alloy FeNiCrWMn.

  5. Low-cost Fe--Ni--Cr alloys for high temperature valve applications

    DOEpatents

    Muralidharan, Govindarajan

    2017-03-28

    An Fe--Ni--Cr alloy is composed essentially of, in terms of weight percent: 1 to 3.5 Al, up to 2 Co, 15 to 19.5 Cr, up to 2 Cu, 23 to 40 Fe, up to 0.3 Hf, up to 4 Mn, 0.15 to 2 Mo, up to 0.15 Si, up to 1.05 Ta, 2.8 to 4.3 Ti, up to 0.5 W, up to 0.06 Zr, 0.02 to 0.15 C, 0.0001 to 0.007 N, balance Ni, wherein, in terms of atomic percent: 6.5.ltoreq.Al+Ti+Zr+Hf+Ta.ltoreq.10, 0.33.ltoreq.Al/(Al+Ti+Zr+Hf+Ta).ltoreq.0.065, 4.ltoreq.(Fe+Cr)/(Al+Ti+Zr+Hf+Ta).ltoreq.10, the alloy being essentially free of Nb and V.

  6. Corrosion Behavior of NiCrFe Alloy 600 in High Temperature, Hydrogenated Water

    SciTech Connect

    SE Ziemniak; ME Hanson

    2004-11-02

    The corrosion behavior of Alloy 600 (UNS N06600) is investigated in hydrogenated water at 260 C. The corrosion kinetics are observed to be parabolic, the parabolic rate constant being determined by chemical descaling to be 0.055 mg dm{sup -2} hr{sup -1/2}. A combination of scanning and transmission electron microscopy, supplemented by energy dispersive X-ray spectroscopy and grazing incidence X-ray diffraction, are used to identify the oxide phases present (i.e., spinel) and to characterize their morphology and thickness. Two oxide layers are identified: an outer, ferrite-rich layer and an inner, chromite-rich layer. X-ray photoelectron spectroscopy with argon ion milling and target factor analysis is applied to determine spinel stoichiometry; the inner layer is (Ni{sub 0.7}Fe{sub 0.3})(Fe{sub 0.3}Cr{sub 0.7}){sub 2}O{sub 4}, while the outer layer is (Ni{sub 0.9}Fe{sub 0.1})(Fe{sub 0.85}Cr{sub 0.15}){sub 2}O{sub 4}. The distribution of trivalent iron and chromium cations in the inner and outer oxide layers is essentially the same as that found previously in stainless steel corrosion oxides, thus confirming their invariant nature as solvi in the immiscible spinel binary Fe{sub 3}O{sub 4}-FeCr{sub 2}O{sub 4} (or NiFe{sub 2}O{sub 4}-NiCr{sub 2}O{sub 4}). Although oxidation occurred non-selectively, excess quantities of nickel(II) oxide were not found. Instead, the excess nickel was accounted for as recrystallized nickel metal in the inner layer, as additional nickel ferrite in the outer layer, formed by pickup of iron ions from the aqueous phase, and by selective release to the aqueous phase.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Microstructure and thermal stability of a Ni-Cr-Co-Ti-V-Al high-entropy alloy coating by laser surface alloying

    NASA Astrophysics Data System (ADS)

    Cai, Zhaobing; Cui, Xiufang; Jin, Guo; Liu, Zhe; Zheng, Wei; Li, Yang; Wang, Liquan

    2017-09-01

    A Ni-Cr-Co-Ti-V-Al high-entropy alloy (HEA) coating with a BCC phase and (Ni, Co)Ti2 compounds was synthesized successfully by laser surface alloying on a Ti-6Al-4V substrate. The microstructure of as-synthesized coatings is typical, namely, the microstructure from the coating to the substrate changes from equiaxed grains to columnar grains. After remaining at 900 °C for 8 h, the constituent phases remain unchanged. However, owing to the unceasing dissolution of the Ti element, the lattice parameter of the BCC HEA phase changes from 3.06 Å to 3.16 Å. The thermoanalysis results show that the oxidation film on the Ni-Cr-Co-Ti-V-Al HEA coating is mainly composed of TiO2, V2O5, and NiO. The oxidation resistance of this HEA coating may be due to the existence of NiO and the alloying elements Al, Cr, and Co; the oxidation phenomenon should be responsible for the mass increase in the thermogravimetry process. The differential scanning calorimetry and the dynamic differential scanning calorimetry curves show that the synthesized HEA coating is stable below 1005 °C.

  12. 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.

  13. 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.

  14. The hydrogen embrittlement of Ni-Cr-Fe alloys

    SciTech Connect

    Symons, D.M.

    1996-12-31

    It has been proposed that the stress corrosion cracking (SCC) of nickel-based alloys in low-temperature hydrogenated water is due to hydrogen embrittlement. The purpose of this work was to investigate the role of chromium on hydrogen embrittlement of Ni-Cr-Fe alloys and thus develop a better understanding of the low-temperature SCC phenomenon. The effect of chromium on the hydrogen embrittlement was examined using tensile tests followed by material evaluation via scanning electron microscopy and light optical microscopy. Four alloys were prepared with chromium contents ranging from 6 wt. percent to 35 wt. percent. In the noncharged condition, ductility, as measured by the percent elongation or reduction in area, increased as the alloy chromium content increased. Hydrogen appeared to have only minor effects on the mechanical properties of the low chromium alloys. The addition of hydrogen had a marked effect on the ductility of the higher chromium alloys. In the 26% chromium alloy, the elongation to failure was reduced from 53% to 14% with a change in fracture mode from ductile dimple to intergranular failure. A maximum in embrittlement was observed in the 26% Cr alloy. The maximum in embrittlement coincided with the minimum in stacking-fault energy. It is proposed that the increased hydrogen embrittlement in the high-chromium alloys is due to increased slip planarity caused by the low stacking-fault energy. Slip planarity did not appear to affect the fracture of the noncharged specimens.

  15. 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.

  16. Diffusive Interaction Between Ni-Cr-Al Alloys

    NASA Astrophysics Data System (ADS)

    Tkacz-Śmiech, Katarzyna; Danielewski, Marek; Bożek, Bogusław; Berent, Katarzyna; Zientara, Dariusz; Zajusz, Marek

    2017-03-01

    In high-temperature coatings, welded parts, and a range of other applications, components in the contact zone interdiffuse at elevated temperatures and may react to change the phase composition. The diffusion zone can be complex and can consist of sequential layers of intermediate phases, solid solutions, and in the case of multicomponent systems also of multiphase layers. In this work, the interdiffusion in Ni-Cr-Al alloys is studied experimentally and modeled numerically. The diffusion multiples were prepared by hot isostatic pressing and post-annealing at 1473 K (1200 °C). The concentration profiles were measured with wide-line EDS technique which allowed obtaining high-accuracy diffusion paths. The experimental profiles and diffusion paths were compared with numerical results simulated with application of very recent model of interdiffusion in muticomponent-multiphase systems. The calculated and experimental data show good agreement.

  17. Diffusive Interaction Between Ni-Cr-Al Alloys

    NASA Astrophysics Data System (ADS)

    Tkacz-Śmiech, Katarzyna; Danielewski, Marek; Bożek, Bogusław; Berent, Katarzyna; Zientara, Dariusz; Zajusz, Marek

    2017-05-01

    In high-temperature coatings, welded parts, and a range of other applications, components in the contact zone interdiffuse at elevated temperatures and may react to change the phase composition. The diffusion zone can be complex and can consist of sequential layers of intermediate phases, solid solutions, and in the case of multicomponent systems also of multiphase layers. In this work, the interdiffusion in Ni-Cr-Al alloys is studied experimentally and modeled numerically. The diffusion multiples were prepared by hot isostatic pressing and post-annealing at 1473 K (1200 °C). The concentration profiles were measured with wide-line EDS technique which allowed obtaining high-accuracy diffusion paths. The experimental profiles and diffusion paths were compared with numerical results simulated with application of very recent model of interdiffusion in muticomponent-multiphase systems. The calculated and experimental data show good agreement.

  18. [Effect of aurum coating on corrosion resistance of Ni-Cr alloy].

    PubMed

    Chen, Zhi-hong; Liu, Li; Mao, Ying-jie

    2007-02-01

    To evaluate the effect of aurum coating on corrosion resistance of Ni-Cr alloy in artificial saliva environment. The corrosion potential (E(corr)), self-corrosion current density (I(corr)), and polarization resistance (R(p)) of three alloys were measured using electrochemical methods to compare the difference of corrosion resistance between aurum-coated Ni-Cr alloy and Ni-Cr alloy or Au alloy. Meanwhile, microstructural and phase diffraction was examined with field scanning electromicroscopy (FSEM) and surface chemical analysis was performed by energy diffraction X-ray (EDX). The I(corr) of aurum-coated Ni-Cr alloy was (0.70 +/- 0.20) x 10(-6) A/cm2, which was significantly higher than that of Au alloy (P < 0.05) and lower than that of Ni-Cr alloy (P < 0.05). R(p) of aurum-coated Ni-Cr alloy was (34.77 +/- 12.61) KOmega.cm2, which was higher than that of Ni-Cr alloy (P < 0.05) and lower than that of Au alloy (P < 0.05). The results of FSEM showed that the corrosion resistance of Ni-Cr alloy coated with aurum was better than that of Ni-Cr alloy. The results of EDX indicated that released Ni and Cr of Ni-Cr alloy coated with aurum after test were less than those of Ni-Cr alloy (P < 0.05). The corrosion resistance of aurum-coated Ni-Cr alloy is higher than that of Ni-Cr alloy.

  19. Electrodeposition and characterization of NiCr alloy nanowires

    NASA Astrophysics Data System (ADS)

    Maleki, K.; Alemipour, Z.

    2017-06-01

    The NiCr alloy nanowires were electrodeposited from an acidic sulphate baths into nanoporous anodized aluminume oxide (AAO). This template was fabricated by two-step anodization. The NiCr alloy nanowires were synthesized for Cr content up to 0.32% without any significant improvement in magnetic properties. Above this threshold, Cr clusters were formed and magnetic properties were decreased significantly. For Cr content of higher than 2.1% the wires were formed so short and incomplete which were like the nanoparticles. X-ray diffraction patterns revealed changing in the FCC crystal structure of Ni nanowires to an amorphous phase by increasing the Cr content. This leads to a significant decline in the magnetic properties like coercivity and squareness. The effect of thermal annealing on the magnetic properties of the NiCr alloy nanowires, showed that the squareness and the coercivity were improved by enhancing the amount of the temperature to 300 °C and were decreased by enhancing that to 500 °C.

  20. 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.

  1. 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.

  2. Effect of Corrosion Film Composition and Structure on the Corrosion Kinetics of Ni-Cr-Fe Alloys in High Temperature Water

    SciTech Connect

    P.M. Rosecrans; N. Lewis; D.J. Duquette

    2002-02-27

    Nickel alloys such as Alloy 600 undergo Stress Corrosion Cracking (SCC) in pure water at temperatures between about 260 C and the critical point. Increasing the level of Cr in Ni-Fe-Cr alloys increases SCC resistance in aerated and deaerated water. The mechanism is not understood. The effect of Cr composition on oxide microstructure and corrosion kinetics of Ni-Fe-Cr alloys was determined experimentally, to evaluate whether the anodic dissolution model for SCC can account for the effect of Cr on SCC. The alloy corrosion rate and corrosion product oxide microstructure is strongly influenced by the Cr composition. Corrosion kinetics are parabolic and influenced by chromium concentration, with the parabolic constant first increasing then decreasing as Cr increases from 5 to 39%. Surface analyses using Analytical Electron microscopy (AEM) and Auger Electron Spectroscopy (AES) show that the corrosion product film that forms initially on all alloys exposed to high purity high temperature water is a nickel rich oxide. With time, the amount of chromium in the oxide film increases and corrosion proceeds toward the formation of the more thermodynamically stable spinel or hexagonal Cr-rich oxides, similar to high temperature gaseous oxidation. Due to the slower diffusion kinetics at the temperatures of water corrosion compared to those in high temperature gaseous oxidation, however, the films remain as a mixture of NiO, mixed Ni, Fe and Cr spinels, NiCrO{sub 3} and FeCrO{sub 3}. As the amount of Cr in the film increases and the nature of the film changes from NiO to spinel or hexagonal oxides, cation diffusion through the films slows, slowing the corrosion rate. These observations are qualitatively consistent with an anodic dissolution SCC mechanism. However, parametric modeling of the SCC growth process, applying available creep, oxide rupture strain and corrosion kinetics data, indicates that the anodic dissolution mechanism accounts for only a fraction of the effect of Cr

  3. A comparative study of high velocity oxygen fuel, vacuum plasma spray, and axial plasma spray for the deposition of CoNiCrAlY bond coat alloy

    NASA Astrophysics Data System (ADS)

    Scrivani, A.; Bardi, U.; Carrafiello, L.; Lavacchi, A.; Niccolai, F.; Rizzi, G.

    2003-12-01

    In the aerospace field as well as in the stationary gas turbine field, thermally sprayed coatings are used to improve the surface properties of nickel-super-alloys materials. Coatings are commonly used as bond coat and antioxidation materials (mainly MCrAlY alloys) and as thermal barrier coatings (mainly yttria partially stabilized zirconia). The purpose of the current study was to assess the properties of thermally sprayed bond coat CoNiCrAlY alloys comparing the performance of three different techniques: vacuum plasma spray (VPS), high velocity oxygen fuel (HVOF), and axial plasma spray (AxPS). The quality of the deposited films has been assessed and compared from the point of view of microstructural (porosity, oxide concentration, unmelted particles presence) and mechanical (hardness) characteristics. The surface composition and morphology of the coatings were also determined. Specific efficiency tests were performed for the three examined technologies. The highest quality coatings are obtained by VPS, but also high velocity oxygen fuel and AxPS sprayed films have interesting properties, which can make their use interesting for some applications.

  4. Weak-beam imaging of dissociated dislocations in HVEM-irradiated Fe-Ni-Cr alloys

    SciTech Connect

    King, S.L.; Jenkins, M.L.; Kirk, M.A. . Dept. of Materials); English, C.A. . Harwell Lab.)

    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.

  5. Bonding Ni-Cr alloy to tooth structure with adhesive resin cements.

    PubMed

    Penugonda, B; Scherer, W; Cooper, H; Kokoletsos, N; Koifman, V

    1992-01-01

    This study was to determine the shear bond strengths of Ni-Cr alloy to Ni-Cr alloy (Group I), Ni-Cr alloy to enamel (Group II), and Ni-Cr alloy to dentin (Group III) using Imperva Dual, DC Metabond, All-Bond, Geristore, and Panavia. All bonded specimens were thermocycled 2000 x (5 degrees C-55 degrees C) after 24 hours and subjected to shear bond testing on a Universal Instron Testing Machine. In all groups of the study, Imperva Dual and CB Metabond had significantly (p < .05) higher bond values than Panavia.

  6. Field emission properties of carbon nanotubes film grown on NiCr alloy films

    NASA Astrophysics Data System (ADS)

    Chen, T.; Wang, L. L.; Chen, Y. W.; Que, W. X.; Sun, Z.

    2007-06-01

    Carbon nanotubes (CNTs) are prepared on NiCr alloy films by low pressure thermal chemical vapor deposition at 600 °C. NiCr alloy films are deposited by magnetic co-sputtering method, and the various thickness and Ni/NiCr ratios are controlled by sputtering power. The diameter and length of CNTs, as well as the roughness of the CNTs films, mainly depend on the Ni/NiCr ratio. The field emission current density of the CNTs film increases with the increasing Ni/NiCr ratio from 65 wt% to 83 wt%, and decreases when the Ni/NiCr ratio is more than 87 wt% in the alloy film.

  7. Localized Corrosion of a Neutron Absorbing Ni-Cr-Mo-Gd Alloy

    SciTech Connect

    R.E. Mizia; T. E. Lister; P. J. Pinhero; T. L. Trowbridge

    2005-04-01

    The National Spent Nuclear Fuel Program, located at the Idaho National Laboratory (INL), has developed a new nickel-chromium-molybdenum-gadolinium structural alloy for storage and long-term disposal of spent nuclear fuel (SNF). The new alloy will be used for SNF storage container inserts for nuclear criticality control. Gadolinium has been chosen as the neutron absorption alloying element due to its high thermal neutron absorption cross section. This alloy must be resistant to localized corrosion when exposed to postulated Yucca Mountain in-package chemistries. The corrosion resistance properties of three experimental heats of this alloy are presented. The alloys performance are be compared to Alloy 22 and borated stainless steel. The results show that initially the new Ni-Cr-Mo-Gd alloy is less resistant to corrosion as compared to another Ni-Cr-Mo-Gd alloy (Alloy 22); but when the secondary phase that contains gadolinium (gadolinide) is dissolved, the alloy surface becomes passive. The focus of this work is to qualify these gadolinium containing materials for ASME code qualification and acceptance in the Yucca Mountain Repository.

  8. [Composition and morphology of oxides on porcelain fused to Ni-Cr alloys. Be containing alloys].

    PubMed

    Watanabe, T

    1989-06-01

    Bonding strength between porcelain and Ni-Cr alloy for the porcelain fused-to metal crown in which Be is contained in the alloy is known to be higher than those in which Be is not contained. Since, bonding between porcelain and alloy is the reaction of oxides and porcelain, the bonding is thought to be influenced by the quality the oxides film which forms on the alloy surface. The purpose of this study was to determine the composition and morphology of the oxides formed on both Be containing and non-Be contained Ni-Cr alloys. The oxides analysis was done using an EPMA and Auger analysis. Also, the Porcelain/Ni-Cr alloy interface was observed by a scanning electron microscope (SEM). The following results are indicated from this investigation: 1. The oxides from the alloys not containing Be are corundum type Cr2O3 and spinel type NiCr2O4. These oxide layers are uniform, thick and porous and the adhesion to alloy is poor. 2. The oxides from alloy containing Be is BeO only. The BeO is uniform, thin and condensed. The adhesion to the alloy is good. 3. The oxide layer formed when the porcelain is fused to alloy containing Be is thin (1 micron average) and has good adhesion to alloy. 4. Be is selectively oxidized and controlled the form of Cr2O3 and NiO.

  9. The interaction of point defects with line dislocations in HVEM (high voltage electron microscope) irradiated Fe-Ni-Cr alloys

    SciTech Connect

    King, S.L.; Jenkins, M.L. . Dept. of Materials); Kirk, M.A. ); English, C.A. . Materials Development Div.)

    1990-05-01

    This paper presents results of a study of the interaction of point defects produced by high voltage electron microscope (HVEM) irradiation with pre-existing dislocations in austenitic Fe-15% 25%Ni-17%Cr alloys, aimed at the determination of the mechanisms of climb of dissociated dislocations. Dislocations were initially characterized at sub-threshold voltages (here 200kV) using the weak-beam technique. These dislocations were then irradiated with 1MeV electrons in the Argonne HVEM before being returned to a lower voltage microscope for post-irradiation characterization. Interstitial climb was seen only at particularly favorable sites, such as pre-existing jogs, whilst vacancies clustered near dislocations, forming stacking fault tetrahedra (SFT). Partial separations were also observed to have decreased after irradiation. The post-irradiation configuration was found to depend strongly on both dislocation character and pre-irradiation dislocation configuration. These results, and their relevance to the void swelling problem, are discussed. 52 refs., 8 figs.

  10. 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.

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

    SciTech Connect

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

    1988-02-01

    The cyclic oxidation behavior of several cast {gamma} + {beta}, Ni-Cr-Al(Y, Zr) alloys and one LPPS {gamma} + {beta}, Ni-Co-Cr-Al(Y) alloy was examined ({gamma}, fcc; {beta}, NiAl structure). Cyclic oxidation was performed by cycling between 1200{degree}C and approximately 70{degree}C. Oxide morphologies and microstructural changes during cyclic oxidation were noted. Recession of the high-Al {beta} phase was nonparabolic with time. Kirkendall porosity resulting from diffusional transport within the alloy was observed in the near-surface {gamma}-phase layer of one alloy. Concentration profiles for Ni, Cr, and Al were measured in the {gamma}-phase layer after various cyclic oxidation exposures. It was observed that cyclic oxidation results in a decreasing Al concentration at the oxide-metal interface due to a high demand for Al (a high rate of Al consumption) associated with oxide scale cracking and spalling. In addition, diffusion paths plotted on the ternary phase diagram shifted to higher Ni concentrations with increasing cyclic oxidation exposures. The alloy with the highest rate of Al consumption, and highest Al content, underwent breakway oxidation after 500 1-hr cycles at 1200{degree}C. Breakaway oxidation occurred when the Al concentration at the oxide-metal interface approached zero. The relationship between the Al transport in the alloy and breakaway oxidation is discussed.

  12. 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.

  13. 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.

  14. Effects of Oxide Layer on the Bonding Strength of Ni-Cr Alloys with Porcelain Ceramics.

    PubMed

    Park, W U; Jung, S H; Zhao, Jingming; Hwang, Kyu H; Lee, J K; Mitchell, John C

    2015-08-01

    The metal-ceramic crown restoration was the most actively used at esthetic restoration for its convenience of forming. Due to constant rise of gold price, non-precious metal such as Ni-Cr alloy have been widely used as metal-ceramic restorations. For easy casting and lower melting point Be was added as minor component to Ni-Cr for a long time, but the use of Be was regulated to deteriorate to human lung. In this study, Ni-Cr specimens containing Be (T-3, Ticonium, USA) and non-Be (Bellabond Plus, BEGO, Germany) were fabricated and by heat treatments at 800-1050 0C oxide layer was formed for subsequent bonding to porcelain ceramics. By heat treatment of the non-Be specimens at high temperature more thick oxide layer was formed and showed lower bonding strength due to the debonding at oxide layers. But in the Be-containing specimens debonding was occurred at porcelain layer so that they showed higher bonding strength. So by heat treatment of non-Be specimens at vacuum condition rather thinner oxide film could be formed so that showed higher coupling strength due to the debonding at porcelain layers than oxide layers.

  15. 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.

  16. Dynamic behavior and microstructural evolution during moderate to high strain rate hot deformation of a Fe-Ni-Cr alloy (alloy 800H)

    NASA Astrophysics Data System (ADS)

    Cao, Yu; Di, Hongshuang; Zhang, Jiecen; Yang, Yaohua

    2015-01-01

    The objective of the study is to fundamentally understand the dynamic behavior of alloy 800H at moderate to high strain rate using hot compression tests and propose nucleation mechanism associated with dynamic crystallization (DRX). We firstly investigated the dynamic behavior of alloy 800H with industrial scale strain rates using hot compression tests and adiabatic correction was performed to correct as-measured flow curves. Secondly, a Johnson-Cook model was established by using the corrected data and could give a precise prediction of elevated temperature flow stress for the studied alloy. Finally, the nucleation mechanism of DRX grains at high strain rates was studied. The results showed that the predominant nucleation mechanism for DRX is the formation of "bulge" at parent grain boundary. Additionally, the fragmentation of original grain at low deformation temperatures and the twinning near the bulged regions at high deformation temperatures also accelerate the DRX process.

  17. 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.

  18. 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.

  19. 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.

  20. [The effect on anti-acid corrosion resistance of Ni-Cr alloy coating titanium].

    PubMed

    Hu, Bin; Zhang, Fu-qiang

    2003-04-01

    The aim of this study was to investigate the variation of the corrosion resistance of Ni-Cr alloy in acid environment before and after coating titanium in vitro. 1. Surface treatment using sol-gel technique of coating titanium. The steps were as follows: (1) Pre-treatment: sanding, washing and activation in order to remove the oxidative product; (2) The preparation of sol: some small charged particles produced by the hydrolytic reaction, and formed sol. These particles would congeal into extremely small ones (diameter usually is 5 microns); (3) Coating; (4) Heat treatment: The organism was resolved and volatilizeed at high temperature, and the atoms of Ti were left. These atoms of Ti were very active and could combine firmly with the atoms on the surface awaiting of treatment. 2. artificial saliva; pH = 7.0 and pH = 5.6; temperature: 36.5 degrees C 3. Electrochemical test: polarization curve; instrument: ZF-3 poteniostat. Before coating titanium, when pH was 7.0, the electrode potential of Ni-Cr alloy was -160 mV, and the self-corrosion current density was 0.262 microA cm-2; when pH = 5.6, the data were -182 mV and 0.352 microA cm-2, respectively. This result showed that when pH value reduced, the potential and current density descended, too. This indicated that the material was easy to be corroded. After coating titanium, when pH value was 7.0, the potential was -71 mV, the self-corrosion current density was 0.152 microA cm-2; when pH = 5.6, the data were -89 mV and 0.174 microA cm-2. This indicated that the corrosion rate of material descended evidently after coating titanium in acid environment. (1) Not only before coating Ti but also after coating, the corrosion resistance of Ni-Cr alloy would descend in acid environment;(2) In acid environment, the corrosion resistance of Ni-Cr alloy after coating titanium was superior to that of the material before coating. So was in neutral environment.

  1. Interatomic potential to study the formation of NiCr clusters in high Cr ferritic steels

    NASA Astrophysics Data System (ADS)

    Bonny, G.; Bakaev, A.; Olsson, P.; Domain, C.; Zhurkin, E. E.; Posselt, M.

    2017-02-01

    Under irradiation NiSiPCr clusters are formed in high-Cr ferritic martensitic steels as well as in FeCr model alloys. In the literature little is known about the origin and contribution to the hardening of these clusters. In this work we performed density functional theory (DFT) calculations to study the stability of small substitutional NiCr-vacancy clusters and interstitial configurations in bcc Fe. Based on DFT data and experimental considerations a ternary potential for the ferritic FeNiCr system was developed. The potential was applied to study the thermodynamic stability of NiCr clusters by means of Metropolis Monte Carlo (MMC) simulations. The results of our simulations show that Cr and Ni precipitate as separate fractions and suggest only a limited synergetic effect between Ni and Cr. Therefore our results suggest that the NiCrSiP clusters observed in experiments must be the result of other mechanisms than the synergy of Cr and Ni at thermal equilibrium.

  2. A structural investigation of a plasma sprayed Ni--Cr based alloy coating

    SciTech Connect

    Sampath, S.; Neiser, R.A.; Herman, H. ); Kirkland, J.P.; Elam, W.T. )

    1993-01-01

    A Ni--Cr based hardfacing alloy has been plasma sprayed in ambient and low pressure atmospheres onto mild steel substrates. These coatings exhibit excellent wear and corrosion resistance; however, the significance of microstructure on properties has not been reported. This study relates the structure of the sprayed coatings to the processing conditions. X-ray diffraction results indicate phase separation in air plasma sprayed deposits, while low pressure plasma sprayed deposits exhibit a single supersaturated solid solution. Annealing of the air plasma sprayed coating shows dissolution of the bcc chromium phase, confirming its metastable nature. These results were confirmed using Extended X-ray Absorption Fine Structure (EXAFS) analysis, which further suggests a highly disordered structure, with partial oxidation of selected alloying elements, such as chromium. Transmission electron microscopy indicates a wide variety of microstructures in the air plasma sprayed deposit. In the case of low pressure sprayed deposit, the microstructures are homogeneous and uniform.

  3. Electrochemical methods to detect susceptibility of Ni-Cr-Mo-W alloy 22 to intergranular corrosion

    NASA Astrophysics Data System (ADS)

    Gorhe, D. D.; Raja, K. S.; Namjoshi, S. A.; Radmilovic, Velimir; Tolly, Alfredo; Jones, D. A.

    2005-05-01

    Alloy 22 (UNS N06022), a Ni-Cr-Mo-W based alloy, is a candidate material for the outer wall of nuclear waste package (NWP) containers. Even though the alloy is highly stable at low temperatures, it could undergo microstructural changes during processing such as welding and stress relieving. Formation of topologically close-packed (TCP) phases such as μ, P, σ, etc. and Cr-rich carbides could make the material susceptible to localized corrosion. Hence, it is important to correlate the microstructural changes with the corrosion resistance of the alloy by nondestructive and rapid electrochemical tests. In this investigation, different electrochemical test solutions were used to quantify the microstructural changes associated with aging and welding of the wrought alloy 22. The results of double-loop (DL) electrochemical potentiodynamic reactivation (EPR) tests in 1 M H2SO4+0.5 M NaCl+0.01 M KSCN solution indicated Cr depletion during initial stages of aging of wrought alloy 22. Results of EPR tests in 2 M HCl+0.01 M KSCN solution at 60 °C correlated well with the Mo depletion that occurred near TCP phases formed during aging of both weld and wrought alloy 22 materials. The EPR test results were compared with standard chemical weight loss measurements specified by ASTM standard G-28 methods A and B.

  4. Atomic Mobilities and Interdiffusivities for fcc Ni-Cr-Nb Alloys

    NASA Astrophysics Data System (ADS)

    Xu, Gaochi; Liu, Yajun; Kang, Zhitao

    2016-10-01

    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.

  5. Different Effect of Co on the Formation of Topologically Close-Packed Phases in Ni-Cr-Mo and Ni-Cr-Re Alloys

    NASA Astrophysics Data System (ADS)

    Shi, Qianying; An, Ning; Huo, Jiajie; Ding, Xianfei; Zheng, Yunrong; Feng, Qiang

    2017-09-01

    In current study, two sets of Ni-based alloys (Ni-Cr-Mo and Ni-Cr-Re series) containing 0 to 15 at. pct of Co addition were investigated to understand the formation behavior of TCP phases. Significant difference on the formation behavior of TCP phases and corresponding Co effect was found in two series alloys. TCP precipitates (P and µ phase) were observed in both grain interiors and boundaries in Ni-Cr-Mo series alloys. Higher levels of Co addition increased the supersaturation of Mo in the γ matrix, which explained that Co addition promoted µ phase formation. In contrast, the TCP precipitates (σ phase) formed by the manner of discontinuous precipitation transformation in the grain boundaries in Ni-Cr-Re series alloys. More Co additions suppressed the formation of σ phase, which was mainly attributed to the decreased supersaturation of Re in thermodynamically metastable γ matrix. The information obtained from simplified alloy systems in this study is helpful for the design of multicomponent Ni-based superalloys.

  6. 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.

  7. Some properties of a stir-cast Ni-Cr based dental alloy.

    PubMed

    Boswell, P G; Stevens, L

    1980-06-01

    A Ni-Cr based crown and bridge alloy has been successfully stir-cast into small investment mould spaces using a modified induction melting and casting machine. Stir-casting produced substantial improvements to the mechanical properties of the cast alloy. A model for the development of the stir-cast microstructure is described and the clinical significance of the improvements in the alloy's properties is discussed.

  8. Effects of recasting on the biocompatibility of a Ni-Cr alloy.

    PubMed

    Zhang, Chang Yuan; Cheng, Hui; Lin, Dong Hong; Zheng, Ming; Ozcan, Mutlu; Zhao, Wei; Yu, Hao

    2012-01-01

    To evaluate the effects of recasting on the biocompatibility of a commercially available Ni-Cr alloy. The alloy tested was cast and subsequently recast four more times. For each cast condition, 24 disk shaped specimens were fabricated (5 mm in diameter, 0.5 mm in thickness). All the recasting was performed without adding new alloy. After the first cast and following each recast, the surface composition and microstructure of the alloy were determined using an X-ray fluorescence spectrometer and optical microscope, respectively. The in vitro cytotoxicity and in vivo mucous irritation potential of the cast and recast Ni-Cr alloy were investigated. The results were statistically analysed at the significance level of 0.05. Recasting neither yielded to cytotoxicity or to changes in the surface composition of the Ni-Cr alloy tested. However, an increase in impurities and porosity of the surface structure was observed with recasting. Also, the segregation of the impurities to grain boundaries was evident after multiple castings. After the fourth recast, the alloys showed significantly greater mucosal irritation than the control. After fourth recast, the alloy of this type may contribute to mucosal inflammation. Furthermore, there is a need for diverse methods addressing different biological endpoints for the evaluation of dental alloys.

  9. 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.

  10. Corrosive and cytotoxic properties of compact specimens and microparticles of Ni-Cr dental alloy.

    PubMed

    Ristic, Ljubisa; Vucevic, Dragana; Radovic, Ljubica; Djordjevic, Snezana; Nikacevic, Milutin; Colic, Miodrag

    2014-04-01

    Nickel-chromium (Ni-Cr) dental alloys have been widely used in prosthodontic practice, but there is a permanent concern about their biocompatibility due to the release of metal ions. This is especially important when Ni-Cr metal microparticles are incorporated into gingival tissue during prosthodontic procedures. Therefore, the aim of this study was to examine and compare the corrosion and cytotoxic properties of compact specimens and microparticles of Ni-Cr dental alloy. Ni-Cr alloy, Remanium CSe bars (4 mm diameter), were made by the standard casting method and then cut into 0.5-mm-thick disks. Metal particles were obtained by scraping the bars using a diamond instrument for crown preparation. The microstructure was observed by an optical microscope. Quantitative determination and morphological and dimensional characterization of metal particles were carried out by a scanning electron microscope and Leica Application Suite software for image analysis. Corrosion was studied by conditioning the alloy specimens in the RPMI 1640 medium, containing 10% fetal calf serum in an incubator with 5% CO2 for 72 hours at 37°C. Inductively coupled plasma-optical emission spectrometry was used to assess metal ion release. The cytotoxity of conditioning medium (CM) was investigated on L929 cells using an MTT test. One-way ANOVA was used for statistical analysis. After casting, the microstructure of the Remanium CSe compact specimen composed of Ni, Cr, Mo, Si, Fe, Al, and Co had a typical dendritic structure. Alloy microparticles had an irregular shape with a wide size range: from less than 1 μm to more than 100 μm. The release of metal ions, especially Ni and Mo from microparticles, was significantly higher, compared to the compact alloy specimen. The CM prepared from compact alloy was not cytotoxic at any tested dilutions, whereas CM from alloy microparticles showed dose-dependent cytotoxicity (90% CM and 45% CM versus control; p < 0.005). Ni-Cr microparticles showed less

  11. 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.

  12. Long-term high-velocity oxidation and hot corrosion testing of several NiCrAl and FeCrAl base oxide dispersion strengthened alloys

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    Several oxide dispersion strengthened (ODS) alloys have been tested for cyclic, long-term, high gas-velocity resistance to oxidation at 1100 C and hot corrosion at 900 C. Both nominally Ni-16Cr-4Al and Fe-20Cr-4.5Al ODS alloys were subjected up to about 2500 cycles, where each cycle consisted of 1 hr in a hot, Mach 0.3 combusted gas stream followed by a 3-min quench in an ambient temperature, Mach 0.3 air blast. For comparison to existing technology, a coated superalloy was simultaneously tested. The ODS iron alloy exhibited clearly superior behavior, surviving 3800 oxidation and 2300 hot corrosion cycles essentially unscathed. While the ODS nickel alloys exhibited adequate oxidation resistance, the long-term hot corrosion resistance could be marginal, since the best life for such alloys under these conditions was only about 1100 cycles. However, the hot corrosion resistance of the ODS Ni-base alloys is excellent in comparison to that of traditional superalloys.

  13. Long-term high-velocity oxidation and hot corrosion testing of several NiCrAl and FeCrAl base oxide dispersion strengthened alloys

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    Several oxide dispersion strengthened (ODS) alloys have been tested for cyclic, long-term, high gas-velocity resistance to oxidation at 1100 C and hot corrosion at 900 C. Both nominally Ni-16Cr-4Al and Fe-20Cr-4.5Al ODS alloys were subjected up to about 2500 cycles, where each cycle consisted of 1 hr in a hot, Mach 0.3 combusted gas stream followed by a 3-min quench in an ambient temperature, Mach 0.3 air blast. For comparison to existing technology, a coated superalloy was simultaneously tested. The ODS iron alloy exhibited clearly superior behavior, surviving 3800 oxidation and 2300 hot corrosion cycles essentially unscathed. While the ODS nickel alloys exhibited adequate oxidation resistance, the long-term hot corrosion resistance could be marginal, since the best life for such alloys under these conditions was only about 1100 cycles. However, the hot corrosion resistance of the ODS Ni-base alloys is excellent in comparison to that of traditional superalloys.

  14. Role of lead in electrochemical reaction of alloy 600, alloy 690, Ni, Cr, and Fe in water

    NASA Astrophysics Data System (ADS)

    Hwang, Seong Sik; Kim, Joung Soo; Kim, Ju Yup

    2003-08-01

    It has been reported that lead causes stress corrosion cracking (SCC) in the secondary side of steam generators (SG) in pressurized water reactors (PWR). The materials of SG tubings are alloy 600, alloy 690, or alloy 800, among which the main alloying elements are Ni, Cr, and Fe. The effect of lead on the electrochemical behaviors of alloy 600 and alloy 690 using an anodic polarization technique was evaluated. We also obtained polarization curves of pure Ni, Cr, and Fe in water containing lead. As the amount of lead in the solution increased, critical current densities and passive current densities of alloy 600 and alloy 690 increased, while the breakdown potential of the alloys decreased. Lead increased critical current density and the passive current of Cr in pH 4 and pH 10. The instability of passive film of steam generator tubings in water containing lead might arise from the instability of Cr passivity.

  15. Enhanced Field Emission Properties from Carbon Nanotube Emitters Grown on NiCr Alloy Surfaces with Grain Boundary Effect

    DTIC Science & Technology

    2008-04-01

    NiCr Ni Cr NiCr Cr2O3 Ni O Cr A to m ic C on ce nt ra tio n (% ) Sputter Time (min) (b) (c) 5 μm (a) 384.9 0.0 405.3 7.1 769.5 115.2...Emitters Grown on NiCr Alloy Surfaces with Grain Boundary Effect 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d...Emitters Grown on NiCr Alloy Surfaces with Grain Boundary Effect Setha Yim,1,2 Riichiro Ohta,1,3 Jessie L. Killian,4 Nathaniel B. Zuckerman,1 Emily

  16. Corrosion of Fe, Ni, Cr and their alloys in simulated municipal waste incineration conditions

    SciTech Connect

    Soutrel, F.; Rapin, C.; Steinmetz, P.; Pierotti, G.

    1998-12-31

    One limitation in MSW incineration process is with the degradation of metallic parts (tubes), which can be very severe in the plants, because of the high level of corrosive gases (HCl and SO{sub 2}). Rather than using very resistant but very expensive alloys to make waterwall and superheater tubes, it can be interesting to apply coatings to carbon steels. The problem is however to find the better combination of elements compatible with the substrate and the long term resistance to corrosion. Individual components of coating alloys (Iron, Nickel, Chromium) and also binary alloys (Fe-Cr, Ni-Cr) which can be used to coat metallic parts, have been tested in simulated waste environment (ash, air+HCl+SO{sub 2}, 500 C). Corrosion kinetics and mechanisms could be identified with use of thermogravimetry and with characterization of the corrosion products (XRD, SEM, Electron Microprobe and DSC), Alkaline components present in the ash have a determining influence on the corrosion processes. This result could be correlated to the difference between the thermodynamic properties of complex oxides formed with sodium or potassium (A G, melting temperature, etc...).

  17. The Influence of Composition upon Surface Degradation and Stress Corrosion Cracking of the Ni-Cr-Mo Alloys in Wet Hydrofluoric Acid

    SciTech Connect

    Crook, P; Meck, N S; Rebak, R B

    2006-12-04

    At concentrations below 60%, wet hydrofluoric acid (HF) is extremely corrosive to steels, stainless steels and reactive metals, such as titanium, zirconium, and tantalum. In fact, only a few metallic materials will withstand wet HF at temperatures above ambient. Among these are the nickel-copper (Ni-Cu) and nickel-chromium-molybdenum (Ni-Cr-Mo) alloys. Previous work has shown that, even with these materials, there are complicating factors. For example, under certain conditions, internal attack and stress corrosion cracking (SCC) are possible with the Ni-Cr-Mo alloys, and the Ni-Cu materials can suffer intergranular attack when exposed to wet HF vapors. The purpose of this work was to study further the response of the Ni-Cr-Mo alloys to HF, in particular their external corrosion rates, susceptibility to internal attack and susceptibility to HF-induced SCC, as a function of alloy composition. As a side experiment, one of the alloys was tested in two microstructural conditions, i.e. solution annealed (the usual condition for materials of this type) and long-range ordered (this being a means of strengthening the alloy in question). The study of external corrosion rates over wide ranges of concentration and temperature revealed a strong beneficial influence of molybdenum content. However, tungsten, which is used as a partial replacement for molybdenum in some Ni-Cr-Mo alloys, appears to render the alloys more prone to internal attack. With regard to HF-induced SCC of the Ni-Cr-Mo alloys, this study suggests that only certain alloys (i.e., those containing tungsten) exhibit classical SCC. It was also discovered that high external corrosion rates inhibit HF-induced SCC, presumably due to rapid progression of the external attack front. With regard to the effects of long-range ordering, these were only evident at the highest test temperatures, where the ordered structure exhibited much higher external corrosion rates than the annealed structure.

  18. 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.

  19. 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.

  20. 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.

  1. Growth of Cr-Nitrides on Commercial Ni-Cr and Fe-Cr Base Alloys to Protect PEMFC Bipolar Plates

    SciTech Connect

    Brady, Michael P; Wang, Heli; Yang, Bing; Turner, John; Bordignon, Melanie; Molins, Regine; Abdelhamid, Mahmoud; Lipp, Ludwig; Walker, Larry R

    2007-01-01

    Nitridation of Cr-bearing alloys can yield low interfacial contact resistance (ICR), electrically- conductive and corrosion-resistant CrN or Cr2N base surfaces of interest for a range of electrochemical devices, including fuel cells, batteries, and sensors. This paper presents results of exploratory studies of the nitridation of two high Cr (30-35 wt%) commercially available Ni-Cr alloys and a ferritic high Cr (29 wt.%) stainless steel for proton exchange membrane fuel cell (PEMFC) bipolar plates. A high degree of corrosion resistance in sulfuric acid solutions designed to simulate bipolar plate conditions and low ICR values were achieved via nitridation. Oxygen impurities in the nitriding environment were observed to play a significant role in the nitrided surface structures that formed, with detrimental effects for the Ni-Cr base alloys, but beneficial effects for the stainless steel alloy. Results of single-cell fuel cell testing are also presented.

  2. Magnetic cluster expansion model for random and ordered magnetic face-centered cubic Fe-Ni-Cr alloys

    SciTech Connect

    Lavrentiev, M. Yu. Nguyen-Manh, D.; Dudarev, S. L.; Wróbel, J. S.; Ganchenkova, M. G.

    2016-07-28

    A Magnetic Cluster Expansion model for ternary face-centered cubic Fe-Ni-Cr alloys has been developed, using DFT data spanning binary and ternary alloy configurations. Using this Magnetic Cluster Expansion model Hamiltonian, we perform Monte Carlo simulations and explore magnetic structures of alloys over the entire range of compositions, considering both random and ordered alloy structures. In random alloys, the removal of magnetic collinearity constraint reduces the total magnetic moment but does not affect the predicted range of compositions where the alloys adopt low-temperature ferromagnetic configurations. During alloying of ordered fcc Fe-Ni compounds with Cr, chromium atoms tend to replace nickel rather than iron atoms. Replacement of Ni by Cr in ordered alloys with high iron content increases the Curie temperature of the alloys. This can be explained by strong antiferromagnetic Fe-Cr coupling, similar to that found in bcc Fe-Cr solutions, where the Curie temperature increase, predicted by simulations as a function of Cr concentration, is confirmed by experimental observations. In random alloys, both magnetization and the Curie temperature decrease abruptly with increasing chromium content, in agreement with experiment.

  3. Nickel-based (Ni-Cr and Ni-Cr-Be) alloys used in dental restorations may be a potential cause for immune-mediated hypersensitivity.

    PubMed

    Lu, Yin; Chen, Weiqing; Ke, Wei; Wu, Shaohua

    2009-11-01

    Although nickel-based (Ni-Cr and Ni-Cr-Be) alloy prothesis is widely used in orthodontics, its potential biologic hazards, hypersensitivity in particular, are still uncertain as yet. And only a few studies in vivo have considered the biocompatibility. However, several case reports show adverse effects of immunologic alterations, such as urticaria, respiratory disease, nickel contact dermatitis, microscopic hematuria and proteinuria, and even exacerbated to hepatocyte injury and renal injury. So nickel-based alloy used in dental restorations may be a potential cause for immune-mediated hypersensitivity. The metal surface would occur electrochemical corrosion as metal edge of porcelain-fused-to-nichrome crown exposed to oral cavity rich in electrolytes after restoration, and metal ion would release to oral cavity then come into contact with cells and tissues in the immediate environment, or be distributed throughout the body, mainly to the intestine canal. Once these ions are not biocompatible, the human system may be injured (toxicity and risk of sensitization) if they are absorbed in sufficient quantity. Thus, it is necessary to determine the long-term biocompatibility properties of nickel-based alloy, reduce sensitization, and grasp the information of individual differences in the appearance of adverse reactions in further research.

  4. [Study on postsoldering of Ni-Cr ceramic alloys. Effect of soldering temperature and atmosphere].

    PubMed

    Ishigure, K

    1990-03-01

    The effects of soldering temperatures and atmospheres on tensile strength of solder joints were investigated for two types of Ni-Cr ceramic alloys and one type of gold solder for postsoldering. Each alloy and the gold solder were soldered with fluoride flux in an electric furnace in three different temperatures and four different atmospheres. Of the three different temperatures, one was just over the liquidus point of the solder, another 50 degrees C higher than the liquidus point and the other 100 degrees C higher than the liquidus point. Of the four different atmospheres, one was under vacuum, another under vacuum with a 6 l/h argon gas flow, another under vacuum with a 12 l/h argon gas flow and the other under vacuum with a 24 l/h argon gas flow. Tensile strength testing was performed at the solder joints. The fracture surface was observed by EPMA. Wettability of the liquid solder on each alloy was performed by the sessile drop method in high-purity argon gas. The surface tension and the contact angle of the liquid solder on MgO were determined by the sessile drop method in high-purity argon gas. The soldering was performed in the furnace used for the sessile drop method in high-purity argon gas. The results are summarized as follows. The tensile strength of UNI METAL-solder joints was significantly affected by the soldering temperature (p less than 0.01). However, the effect of the soldering atmosphere on the tensile strength was small. The effect of the soldering temperature and atmosphere on the tensile strength of Victory II-solder joints was small. Each alloy had a different adequate soldering temperature. With the increase in the soldering temperature, the diffusion layer of the solder joint interface increased, but no correlationship between the atmosphere and the diffusion layer thickness was observed. Fracture patterns of UNI METAL-solder joints were mixed adhesive-cohesive fractures with a large cohesive area. Fracture patterns of Victory II

  5. 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.

  6. Comparison of Crevice Corrosion of Fe-Based Amorphous Metal and Crystalline Ni-Cr-Mo Alloy

    SciTech Connect

    Shan, X; Ha, H; Payer, J H

    2008-07-24

    The crevice corrosion behaviors of an Fe-based bulk metallic glass alloy (SAM1651) and a Ni-Cr-Mo crystalline alloy (C-22) were studied in 4M NaCl at 100 C with cyclic potentiodynamic polarization and constant potential tests. The corrosion damage morphologies, corrosion products and the compositions of corroded surfaces of these two alloys were studied with optical 3D reconstruction, Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Auger Electron Spectroscopy (AES). It was found that the Fe-based bulk metallic glass (amorphous alloy) SAM1651 had a more positive breakdown potential and repassivation potential than crystalline alloy C-22 in cyclic potentiodynamic polarization tests and required a more positive oxidizing potential to initiate crevice corrosion in constant potential test. Once crevice corrosion initiated, the corrosion propagation of C-22 was more localized near the crevice border compared to SAM1651, and SAM1651 repassivated more readily than C-22. The EDS results indicated that the corrosion products of both alloys contained high amount of O and were enriched in Mo and Cr. The AES results indicated that a Cr-rich oxide passive film was formed on the surfaces of both alloys, and both alloys were corroded congruently.

  7. Examination of Corrosion Products and the Alloy Surface After Crevice Corrosion of a Ni-Cr-Mo- Alloy

    SciTech Connect

    X. Shan; J.H. Payer

    2006-06-09

    The objective of this study is to investigate the composition of corrosion products and the metal surface within a crevice after localized corrosion. The analysis provides insight into the propagation, stifling and arrest processes for crevice corrosion and is part of a program to analyze the evolution of localized corrosion damage over long periods of time, i.e. 10,000 years and longer. The approach is to force the initiation of crevice corrosion by applying anodic polarization to a multiple crevice assembly (MCA). Results are reported here for alloy C-22, a Ni-Cr-Mo alloy, exposed to a high temperature, concentrated chloride solution. Controlled crevice corrosion tests were performed on C-22 under highly aggressive, accelerated condition, i.e. 4M NaCl, 100 C and anodic polarization to -0.15V-SCE. The crevice contacts were by either a polymer tape (PTFE) compressed by a ceramic former or by a polymer (PTFE) crevice former. Figure 1 shows the polarization current during a crevice corrosion test. After an incubation period, several initiation-stifle-arrest events were indicated. The low current at the end of the test indicated that the metal surface had repassivated.

  8. Chromium Grain-boundary Segregation and Effect of Ion Beam Cleaning on Fe-Ni-Cr Alloys

    SciTech Connect

    Saraf, Laxmikant V.

    2011-04-01

    The grain boundaries play important role to control the mechanical strength of ternary alloys. From spacecrafts to naval vessels to nuclear reactors, stress corrosion cracking, brittleness, oxidation mostly originates at the grain boundaries and cause long term structural stability problems in most of the metallic structures [1]. Fe-Ni-Cr based ternary metal alloys have been widely studied for more than fifty years [2, 3]. Despite of vast amount of research, chromium diffusion in stainless steel or other Ni-Fe-Cr based ternary alloys is still an open scientific problem with challenges in structural stability and corrosion resistance [4]. Particularly, austenite Fe-Ni-Cr is looked upon favorably in space and jet engine industry for their improved resistance to stress corrosion cracking [5]. In solid oxide fuel cells (SOFC), Ni-alloys are frequently used as interconnects and seals [6]. In this communication, simultaneous energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) mapping is utilized to study chemical and structural aspects of chromium segregation in Fe-Ni-Cr alloy. A focused Ga-ion beam is also utilized to study the effect of ion beam cleaning on EBSD image quality (IQ) and inverse pole figure (IPF) maps of Fe-Ni-Cr alloy.

  9. Hot Corrosion Behavior of Arc-Sprayed Highly Dense NiCr-Based Coatings in Chloride Salt Deposit

    NASA Astrophysics Data System (ADS)

    Qin, Enwei; Yin, Song; Ji, Hua; Huang, Qian; Liu, Zekun; Wu, Shuhui

    2017-03-01

    To make cities more environmentally friendly, combustible wastes tend to be incinerated in waste-to-energy power plant boilers. However, release of chlorine gas (Cl2) during incineration causes serious problems related to hot corrosion of boiler tubes and poses a safety threat for such plants. In this study, a pseudo-de Laval nozzle was employed in a twin-wire arc spray system to enhance the velocity of in-flight particles. Highly dense NiCr-based coatings were obtained using the modified nozzle gun. The coating morphology was characterized by optical microscopy and scanning electron microscopy, and hot corrosion testing was carried out in a synthetic molten chloride salt environment. Results showed that the dense NiCr-based coatings exhibited high resistance against corrosion by chlorine, which can be related to the typical splat lamellar microstructure and chemical composition as well as minor alloying elements such as Ti and Mo.

  10. Hot Corrosion Behavior of Arc-Sprayed Highly Dense NiCr-Based Coatings in Chloride Salt Deposit

    NASA Astrophysics Data System (ADS)

    Qin, Enwei; Yin, Song; Ji, Hua; Huang, Qian; Liu, Zekun; Wu, Shuhui

    2017-04-01

    To make cities more environmentally friendly, combustible wastes tend to be incinerated in waste-to-energy power plant boilers. However, release of chlorine gas (Cl2) during incineration causes serious problems related to hot corrosion of boiler tubes and poses a safety threat for such plants. In this study, a pseudo-de Laval nozzle was employed in a twin-wire arc spray system to enhance the velocity of in-flight particles. Highly dense NiCr-based coatings were obtained using the modified nozzle gun. The coating morphology was characterized by optical microscopy and scanning electron microscopy, and hot corrosion testing was carried out in a synthetic molten chloride salt environment. Results showed that the dense NiCr-based coatings exhibited high resistance against corrosion by chlorine, which can be related to the typical splat lamellar microstructure and chemical composition as well as minor alloying elements such as Ti and Mo.

  11. NiCr M ( M = W, Mo, V) ternary alloy tapes as cube-textured substrates for second-generation superconducting cables

    NASA Astrophysics Data System (ADS)

    Rodionov, D. P.; Gervas'eva, I. V.; Khlebnikova, Yu. V.; Kazantsev, V. A.; Sazonova, V. A.

    2012-05-01

    Development of the deformation texture and recrystallization processes have been studied in some ternary nickel-based alloys of the Ni-Cr-W, Ni-Cr-Mo, and Ni-Cr-V systems. An optimum relationship between the amounts of the alloying elements upon the combined alloying of nickel has been found. Problems of the optimization of the regimes of recrystallization annealing have been considered, which are related to an increase in the temperature of the onset of primary recrystallization in ternary nickel alloys after deformation by rolling to large reductions. An analysis of mechanical and magnetic properties of all the alloys has been performed.

  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. Kinetics and Grain Boundary Selectivity of Discontinuous Precipitation in Binary Ni-Cr Alloy

    NASA Astrophysics Data System (ADS)

    Keskar, N.; Pattanaik, A. K.; Mani Krishna, K. V.; Srivastava, D.; Dey, G. K.

    2017-06-01

    A supersaturated Ni-Cr alloy (42 wt pct Cr) was subjected to a series of aging heat treatments in the two-phase region in the temperature range of 923 K to 1123 K (650 °C to 850 °C) for different time periods. The resultant microstructures were seen to be composed of varying volume fractions of continuous (CP) and discontinuous precipitation (DP). The DP dominated at lower temperatures, while CP dominated at higher temperatures and the expected DP termination temperature was estimated to be 1138 K (865 °C). The kinetics of DP followed the Turnbull model at lower temperatures and the Aaronson-Liu model at higher temperatures. The nucleation and growth of DP cells, which occurred via the `precipitate driven grain boundary migration,' was seen to be a strong function of the nature of the participating grain boundaries.

  14. Development of dispersion-strengthened Ni-Cr-ThO2 alloys for the space shuttle thermal protection system.

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    An improved manufacturing process has been developed for TD-NiCr that provides sheet of improved quality, better gage control, and reproducible properties. A standard manufacturing process has been developed for the alternate alloy, DS-NiCr, produced by pack-chromizing Ni-2ThO2 sheet. Extension of forming and joining technology for TD-NiCr is in process. Formability criteria are being established for basic sheet forming processes related to the manufacture of Shuttle TPS panels. They include brake forming, corrugation forming, joggling, dimpling, and beading. Joining processes applicable to TPS panels are being optimized with emphasis on establishment of joint efficiencies. Resistance spot welding (fusion and solid state), resistance seam welding, solid-state diffusion welding, and brazing are included in the joining programs. Development of improved manufacturing technology for TD-NiCr fasteners is also being accomplished. Mechanical and physical properties of TD-NiCr are being characterized to provide design-allowable data.

  15. Microstructure and Oxidation Behavior of Al and Al/NiCrAlY Coatings on Pure Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Gong, Xue; Zhang, Nannan; Zhang, Zhongli; Chen, Ruirun; Lin, Danyang

    2017-06-01

    To improve the oxidation resistance of Ti alloys, a NiCrAlY coating was deposited as diffusion barrier between aluminum overlay coating and pure Ti substrate by air plasma spraying method. The microstructure and oxidation behavior of Al coatings with and without NiCrAlY diffusion barrier were investigated in isothermal oxidation tests at 800 °C for 100 h. The results indicate that the weight gain of the Al/NiCrAlY coating was 4.16 × 10-5 mg2 cm-4 s-1, whereas that of the single Al coating was 9.52 × 10-5 mg2 cm-4 s-1 after 100 h oxidation. As compared with single Al coating, the Al/NiCrAlY coating revealed lower oxidation rate and excellent oxidation resistance by forming thin Al2O3 + NiO scales at overlaying coating/diffusion barrier and diffusion barrier/substrate interfaces. Meanwhile, the inward diffusion of Al and the outward diffusion of Ti were inhibited effectively by the NiCrAlY diffusion barrier.

  16. Preparation and Oxidation Performance of Y and Ce-Modified Cr Coating on open-cell Ni-Cr-Fe Alloy Foam by the Pack Cementation

    NASA Astrophysics Data System (ADS)

    Pang, Q.; Hu, Z. L.; Wu, G. H.

    2016-12-01

    Metallic foams with a high fraction of porosity, low density and high-energy absorption capacity are a rapidly emerging class of novel ultralight weight materials for various engineering applications. In this study, Y-Cr and Ce-Cr-coated Ni-Cr-Fe alloy foams were prepared via the pack cementation method, and the effects of Y and Ce addition on the coating microstructure and oxidation performance were analyzed in order to improve the oxidation resistance of open-cell nickel-based alloy foams. The results show that the Ce-Cr coating is relatively more uniform and has a denser distribution on the surface of the nickel-based alloy foam. The surface grains of the Ce-Cr-coated alloy foam are finer compared to those of the Y-Cr-coated alloy foam. An obvious Ce peak appears on the interface between the coating and the alloy foam strut, which gives rise to a "site-blocking" effect for the short-circuit transport of the cation in the substrate. X-ray diffraction analysis shows that the Y-Cr-coated alloy foam mainly consists of Cr, (Fe, Ni) and (Ni, Cr) phases in the surface layer. The Ce-Cr-coated alloy foam is mainly composed of Cr and (Ni, Cr) phases. Furthermore, the addition of Y and Ce clearly lead to an improvement in the oxidation resistance of the coated alloy foams in the temperature range of 900-1000 °C. The addition of Ce is especially effective in enhancing the diffusion of chromium to the oxidation front, thus, accelerating the formation of a Cr2O3 layer.

  17. Electrochemical corrosion and surface analyses of a ni-cr alloy in bleaching agents.

    PubMed

    Tamam, Evşen; Aydın, A Kevser; Bilgiç, Semra

    2014-10-01

    The aim of this study was to evaluate the corrosion behavior of a Ni-Cr dental casting alloy subjected to 10% hydrogen peroxide (HP) and 10% carbamide peroxide (CP) bleaching solutions and to determine the composition of the surface oxide layer formed on the alloy specimens. Ten cylindrical specimens (4 mm in diameter × 25 mm in height) were cast from a Ni-Cr alloy (Wiron 99) and divided into two groups (n = 5). A potentiodynamic polarization test was used to compare the corrosion rates of specimens in HP and CP (pH = 6.5). Before cyclic polarization tests, all alloy specimens were allowed to reach a steady open circuit potential (Ecorr ) for a period of 1 hour. Then tests were initiated at 100 mV versus standard calomel electrode (SCE) below Ecorr and scanned at a rate of 1 mV/s in the anodic direction until reaching 1000 mV over the Ecorr value. The scan then was reversed back to the Ecorr of the specimens. The open circuit potentials (Ecorr ) and the current densities (Icorr ) were determined using the anodic Tafel regions extrapolating from the curves. Differences in Ecorr and Icorr were determined using one-way ANOVA (α = 0.05). In addition, corrosion rates were calculated from these curves. Before and after polarization tests, a scanning electron microscope (SEM) examination accompanied by energy dispersive X-ray spectroscopy (EDS) was used to analyze the surface morphology. The surface characterization of the passive film formed on alloy specimens was also performed by using X-ray photoelectron spectroscopy (XPS). In this study, bleaching agents had an effect on the anodic process for two groups. Although no statistical difference was identified between the groups for both corrosion parameters, results indicated that the effect of CP on the corrosion behavior was less than that of HP. These results agreed with the SEM observations. XPS data showed that oxide layers formed on all groups contained mainly Cr2 O3 , NiO, and MoO3 , and the amounts of oxides

  18. The effects of sulfate reducing bacteria on stainless steel and Ni-Cr-Mo alloy weldments

    SciTech Connect

    Petersen, T.A.; Taylor, S.R.

    1995-10-01

    Previous research in this laboratory demonstrated a direct correlation between alloy composition and corrosion susceptibility of stainless steel and Ni-Cr-Mo alloy weldments exposed to lake water augmented with sulfate reducing bacteria (SRB). It was shown that lake water containing an active SRB population reduced the polarization resistance (R{sub p}) on all alloys studied including those with 9% Mo. In addition, preliminary evidence indicated that edge preparation and weld heat input were also important parameters in determining corrosion performance. This prior research, however, looked at ``doctored`` weldments in which the thermal oxide in the heat affected zone was removed. The objectives of the research presented here are to further confirm these observations using as-received welds. The materials examined (listed in increasing alloy content) are 1/4 inch thick plates of 316L, 317L, AL6XN (6% Mo), alloy 625 clad steel, alloy 625, and alloy 686. Materials were welded using the tungsten inert gas (TIG) process in an argon purged environment. In addition, 317L was welded in air to test oxide effects. All samples were prepared for welding by grinding to a V-edge, except the 625 clad steel samples which were prepared using a J-edge. Electrochemical performance of welded samples was monitored in four glass cells which could each allow exposure of 8 samples to the same environment. Two cells contained lake water inoculated with SRS, and two cells contained sterilized lake water. The open circuit potential (E{sub oc}) and R{sub p} was used to correlate corrosion susceptibility and bacterial activity with alloy composition and welding parameters.

  19. Stress Intensity Effect on Solid State Oxidation of Ni-Cr Alloy with Different Chromium Concentrates

    NASA Astrophysics Data System (ADS)

    Tirtom, Ismail; Das, Nishith Kumar; Shoji, Tetsuo

    Ni-base alloy is widely used in light water reactor component and the recent study has shown stress corrosion cracking (SCC). Over the years various attempts have been made to obtain mechanism of SCC but it still require more fundamental study to understand clearly. This study presents an approach based on the multiscale modeling, to assess the influence of alloy composition and stress intensity on the initial stage of solid state oxidation of the Ni-Cr alloy. The multiscale modeling considers different length scales such as finite element method (FEM) / quasi-continuum (QC) / quantum chemical molecular dynamics (QCMD), for analyzing crack tip molecular domain. The compact tension (CT) specimen of alloy 600 has been loaded for stress intensity, after that the micro region has chosen for the QC model which is a combination of continuum and atomic method. Finally, the deformed atomic position has picked for the QCMD simulation with some water molecules. The simulated results show that the chromium segregates faster than nickel atoms from the surface and make preferential bonding with oxygen. The preferential bonding forms a passive film. Applied stress intensity deformed the structure which may increase the atomic distance. As distance increases the absorption of water molecule or OH or oxygen into lattice increases. The stress intensity raises the crack tip solid state oxidation that may enhance SCC initiation.

  20. Atomic scale study of grain boundary segregation before carbide nucleation in Ni-Cr-Fe Alloys

    NASA Astrophysics Data System (ADS)

    Li, Hui; Xia, Shuang; Liu, Wenqing; Liu, Tingguang; Zhou, Bangxin

    2013-08-01

    Three dimensional chemical information concerning grain boundary segregation before carbide nucleation was characterized by atom probe tomography in two Ni-Cr-Fe alloys which were aged at 500 °C for 0.5 h after homogenizing treatment. B, C and Si atoms segregation at grain boundary in Alloy 690 was observed. B, C, N and P atoms segregation at grain boundary in 304 austenitic stainless steel was observed. C atoms co-segregation with Cr atoms at the grain boundaries both in Alloy 690 and 304 austenitic stainless steel was found, and its effect on the carbide nucleation was discussed. The amount of each segregated element at grain boundaries in the two Ni-Cr-Fe alloys were analyzed quantitatively. Comparison of the grain boundary segregation features of the two Ni-Cr-Fe alloys were carried out based on the experimental results. The impurity and solute atoms segregate inhomogeneously in the same grain boundary both in 304 SS and Alloy 690. The grain boundary segregation tendencies (Sav) are B (11.8 ± 1.4) > P (5.4 ± 1.4) > N (4.7 ± 0.3) > C (3.7 ± 0.4) in 304 SS, and B (6.9 ± 0.9) > C (6.7 ± 0.4) > Si (1.5 ± 0.2) in Alloy 690. Cr atoms may co-segregate with C atoms at grain boundaries before carbide nucleation at the grain boundaries both in 304 SS and Alloy 690. Ni atoms generally deplete at grain boundary both in 304 SS and Alloy 690. The literature shows that the Ni atoms may co-segregate with P atoms at grain boundaries [28], but the P atoms segregation do not leads to Ni segregation in the current study. In the current study, Fe atoms may segregate or deplete at grain boundary in Alloy 690. But Fe atoms generally deplete at grain boundary in 304 SS. B atoms have the strongest grain boundary segregation tendency both in 304 SS and Alloy 690. The grain boundary segregation tendency and Gibbs free energy of B in 304 SS is higher than in Alloy 690. C atoms are easy to segregate at grain boundaries both in 304 SS and Alloy 690. The grain boundary segregation

  1. Observations of defect structure evolution in proton and Ni ion irradiated Ni-Cr binary alloys

    NASA Astrophysics Data System (ADS)

    Briggs, Samuel A.; Barr, Christopher M.; Pakarinen, Janne; Mamivand, Mahmood; Hattar, Khalid; Morgan, Dane D.; Taheri, Mitra; Sridharan, Kumar

    2016-10-01

    Two binary Ni-Cr model alloys with 5 wt% Cr and 18 wt% Cr were irradiated using 2 MeV protons at 400 and 500 °C and 20 MeV Ni4+ ions at 500 °C to investigate microstructural evolution as a function of composition, irradiation temperature, and irradiating ion species. Transmission electron microscopy (TEM) was applied to study irradiation-induced void and faulted Frank loops microstructures. Irradiations at 500 °C were shown to generate decreased densities of larger defects, likely due to increased barriers to defect nucleation as compared to 400 °C irradiations. Heavy ion irradiation resulted in a larger density of smaller voids when compared to proton irradiations, indicating in-cascade clustering of point defects. Cluster dynamics simulations were in good agreement with the experimental findings, suggesting that increases in Cr content lead to an increase in interstitial binding energy, leading to higher densities of smaller dislocation loops in the Ni-18Cr alloy as compared to the Ni-5Cr alloy.

  2. Effect of Nd:YAG laser parameters on the penetration depth of a representative Ni-Cr dental casting alloy.

    PubMed

    Al Jabbari, Youssef S; Koutsoukis, Theodoros; Barmpagadaki, Xanthoula; El-Danaf, Ehab A; Fournelle, Raymond A; Zinelis, Spiros

    2015-02-01

    The effects of voltage and laser beam (spot) diameter on the penetration depth during laser beam welding in a representative nickel-chromium (Ni-Cr) dental alloy were the subject of this study. The cast alloy specimens were butted against each other and laser welded at their interface using various voltages (160-390 V) and spot diameters (0.2-1.8 mm) and a constant pulse duration of 10 ms. After welding, the laser beam penetration depths in the alloy were measured. The results were plotted and were statistically analyzed with a two-way ANOVA, employing voltage and spot diameter as the discriminating variables and using Holm-Sidak post hoc method (a = 0.05). The maximum penetration depth was 4.7 mm. The penetration depth increased as the spot diameter decreased at a fixed voltage and increased as the voltage increased at a fixed spot diameter. Varying the parameters of voltage and laser spot diameter significantly affected the depth of penetration of the dental cast Ni-Cr alloy. The penetration depth of laser-welded Ni-Cr dental alloys can be accurately adjusted based on the aforementioned results, leading to successfully joined/repaired dental restorations, saving manufacturing time, reducing final cost, and enhancing the longevity of dental prostheses.

  3. Corrosion Behavior of Thermally Sprayed NiCrBSi Coating on 16MnR Low-Alloy Steel in KOH Solution

    NASA Astrophysics Data System (ADS)

    Zeng, Q.; Sun, J.; Emori, W.; Jiang, S. L.

    2016-05-01

    NiCrBSi coatings were selected as protective material and air plasma-sprayed on 16MnR low-alloy steel substrates. Corrosion behavior of 16MnR substrates and NiCrBSi coatings in KOH solution were evaluated by polarization resistance ( R p), potentiodynamic polarization curves, electrochemical impedance spectroscopy, and immersion corrosion tests. Electrolytes were solutions with different KOH concentrations. NiCrBSi coating showed superior corrosion resistance in KOH solution compared with the 16MnR. Corrosion current density of 16MnR substrate was 1.7-13.0 times that of NiCrBSi coating in the given concentration of KOH solution. By contrast, R p of NiCrBSi coating was 1.2-8.0 times that of the substrate, indicating that the corrosion rate of NiCrBSi coating was much lower than that of 16MnR substrate. Capacitance and total impedance value of NiCrBSi coating were much higher than those of 16MnR substrate in the same condition. This result indicates that corrosion resistance of NiCrBSi coating was better than that of 16MnR substrate, in accordance with polarization results. NiCrBSi coatings provided good protection for 16MnR substrate in KOH solution. Corrosion products were mainly Ni/Fe/Cr oxides.

  4. 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.

  5. [Corrosion resistance and wear resistance of Ni-Cr alloy after coating titanium nitride (TiN) in oral containing fluorine environment].

    PubMed

    Weng, Wei-Min; Yu, Wei-Qiang; Shan, Wei-Lan; Zhang, Fu-Qiang

    2010-12-01

    The aim of this study was to evaluate the corrosion resistance and wear resistance of Ni-Cr alloy after coating titanium nitride (TiN) in oral containing fluorine environment. Physical vapor deposition was established to coat titanium nitride (TiN) on the surface of dental cast Ni-Cr alloy to form TiN/Ni-Cr compound. Both Ni-Cr alloy and TiN/Ni-Cr compound were exposed to 37 degrees centigrade, artificial saliva containing 0.24% NaF. The polarization curves of the specimens were measured by PARSTAT 2273 electrochemical station to investigate its corrosion resistance. Vicker's hardness was measured by HXD-1000TMC/LCD micro-hardness tester to investigate its wear resistance. Statistical analysis was performed by SAS 8.2 software package for Student's t methods. The corrosion potential of Ni-Cr alloy was -362.407 mV, the corrosion current density was 1.568μAcm(-2),the blunt-breaking potential was 426 mV bofor TiN coating. The corrosion potential of TiN/Ni-Cr compound was -268.638 mV, the corrosion current density was 0.114μAcm(-2),the blunt-breaking potential was 1142 mV after TiN coating. Polarization curves showed TiN/Ni-Cr compound improved the corrosion potential and blunt-breaking potential, decreased the corrosion current density. The Vicker's hardness of Ni-Cr alloy was 519.75±27.27 before TiN coating, the Vicker's hardness of TiN/Ni-Cr compound was 803.24±24.64, the D-value between them was 283.49±39.34. The difference of Vicker's harnesses between Ni-Cr alloy and TiN/Ni-Cr compound had significant (P<0.01). The results demonstrate that the TiN coating can improve the corrosion resistant to F-and the surface hardness of Ni-Cr alloy. Supported by Research Fund of Science and Technology Commission of Shanghai Municipality (Grant No.08DZ2271100), Shanghai Leading Academic Discipline Project (Grant No.S30206 ) and Research Fund of Health Bureau of Shanghai Municipality (Grant No.2009074).

  6. Interdiffusion in ? (fcc) Ni-Cr-X (X=Al, Si, Ge or Pd) Alloys at 900?C

    SciTech Connect

    Garimella, N; Brady, Michael P; Sohn, Yong Ho

    2006-01-01

    Interdiffusion in Ni-Cr (fcc phase) alloys with small additions of Al, Si, Ge, or Pd was investigated using solid-to-solid diffusion couples. Ni-Cr-X alloys having compositions of Ni- 22at.%Cr, Ni-21at.%Cr-6.2at.%Al, Ni-22at.%Cr-4.0at.%Si, Ni-22at.%Cr-1.6at.%Ge and Ni- 22at.%Cr-1.6at.%Pd were manufactured by arc-casting. The diffusion couples were assembled in an Invar steel jig, encapsulated in Ar after several hydrogen purges, and annealed at 900 C in a three-zone tube furnace for 168 hours. Experimental concentration profiles were determined from polished cross-section of these couples by using electron probe microanalysis with pure element standards. Interdiffusion fluxes of individual components were calculated directly from the experimental concentration profiles, and the moments of interdiffusion fluxes were examined to determine average ternary interdiffusion coefficients. Effects of ternary alloying additions on the diffusional behavior of Ni-Cr-X alloys are presented in the light of the diffusional interactions and the formation of a protective Cr2O3 scale

  7. Corrosion behaviour and surface analysis of a Co-Cr and two Ni-Cr dental alloys before and after simulated porcelain firing.

    PubMed

    Qiu, Jing; Yu, Wei-Qiang; Zhang, Fu-Qiang; Smales, Roger J; Zhang, Yi-Lin; Lu, Chun-Hui

    2011-02-01

    This study evaluated the corrosion behaviour and surface properties of a commercial cobalt-chromium (Co-Cr) alloy and two nickel-chromium (Ni-Cr) alloys [beryllium (Be)-free and Be-containing] before and after a simulated porcelain-firing process. Before porcelain firing, the microstructure, surface composition and hardness, electrochemical corrosion properties, and metal-ion release of as-cast alloy specimens were examined. After firing, similar alloy specimens were examined for the same properties. In both as-cast and fired conditions, the Co-Cr alloy (Wirobond C) showed significantly more resistance to corrosion than the two Ni-Cr alloys. After firing, the corrosion rate of the Be-free Ni-Cr alloy (Stellite N9) increased significantly, which corresponded to a reduction in the levels of Cr, molybdenum (Mo), and Ni in the surface oxides and to a reduction in the thickness of the surface oxide film. The corrosion properties of the Co-Cr alloy and the Be-containing Ni-Cr alloy (ChangPing) were not significantly affected by the firing process. Porcelain firing also changed the microstructure and microhardness values of the alloys, and there were increases in the release of Co and Ni ions, especially for Ni from the Be-free Ni-Cr alloy. Thus, the corrosion rate of the Be-free Ni-Cr alloy increased significantly after porcelain firing, whereas the firing process had little effect on the corrosion susceptibility of the Co-Cr alloy and the Be-containing Ni-Cr alloy.

  8. [The effect of bacteria reaction time on corrosion properties of Ni-Cr alloys pretreated with different proteins].

    PubMed

    Qi, Han-quan; Zhang, Song-mei; Qian, Chao; Yuan-Li, Zheng

    2015-12-01

    To evaluate the corrosion properties of absorbed protein on the surface of NiCr alloys, and provide experimental base for corrosion resistance of dental casting alloys. NiCr alloy specimens were divided into 3 groups: one group was exposed to the artificial saliva(control group), and the other 2 groups were exposed to the artificial saliva with 1% bovine serum albumin(BSA), or 0.22% lysozyme(LSZ). Group of BSA and group of LSZ were the experimental group. Specimens in 3 groups were cultured in solution of Streptococcus mutans for 12 h, 24 h, 36 h and 48h, and investigated with electrochemical impedance spectroscopy measurement(EIS) and potentiodynamic polarization measurement(POT) to determine the corrosion resistance of the alloys. The data was analyzed with SPSS 17.0 software package. The results indicated that the corrosion resistance of both BSA group and LSZ group were higher than that of the control group (P<0.05) and LSZ group was superior to BSA group cultured in the solution of Streptococcus mutans for 12 h. When cultured for 24 h, the corrosion resistance of BSA group and LSZ group had no significant difference (P>0.05), but was still higher than that of the control group. After 36 h culture time, the control group and the BSA group had no statistical difference in corrosion resistance (P>0.05), while the LSZ group had the poorest corrosion resistance. When the culture time extended to 48 h, the control group had a better corrosion resistance compared with the BAS group and the LSZ group(P<0.05), but BSA group had displayed lower corrosion properties than LSZ group. The potentiodynamic polarization curve and electrochemical impedance spectroscopy had similar results. The adhesion of BSA and LSZ on the surface of the NiCr alloys in the early time could effectively inhibit the corrosive effect of Streptococcus mutans. The LSZ had better effect than BSA. With the continuing role of bacteria and the consumption of the absorb protein, the corrosion

  9. [Effect of different heat treatment on mechanical properties and microstructure of laser welding CoCr-NiCr dissimilar alloys].

    PubMed

    Liang, Rui-ying; Li, Chang-yi; Han, Ya-jing; Hu, Xin; Zhang, Lian-yun

    2008-11-01

    To evaluate the effect of heat treatment and porcelain-fused-to-metal (PFM) processing on mechanical properties and microstructure of laser welding CoCr-NiCr dissimilar alloys. Samples of CoCr-NiCr dissimilar alloys with 0.5 mm thickness were laser-welded single-side under the setting parameters of 280 V, 10 ms pulse duration. After being welded, samples were randomly assigned to three groups, 10 each. Group1 and 2 received heat treatment and PFM processing, respectively. Group 3 was control group without any treatment. Tensile strength, microstructure and element distribution of samples in the three groups were tested and observed using tensile test, metallographic examinations, scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS) analysis. After heat treatment and PFM processing, tensile strength of the samples were (537.15 +/- 43.91) MPa and (534.58 +/- 48.47) MPa respectively, and elongation rates in Group 1 and 2 were (7.65 +/- 0.73)% and (7.40 +/- 0.45)%. Ductile structure can be found on tensile fracture surface of samples and it was more obvious in heat treatment group than in PFM group. The results of EDS analysis indicated that certain CoCr alloy diffused towards fusion zone and NiCr side after heat treatment and PFM processing. Compared with PFM processing group, the diffusion in the heat treatment group was more obvious. Heat treatment and PFM processing can improve the mechanical properties and microstructure of welded CoCr-NiCr dissimilar alloy to a certain degree. The improvements are more obvious with heat treatment than with porcelain treatment.

  10. Study of magnetism in Ni-Cr hardface alloy deposit on 316LN stainless steel using magnetic force microscopy

    NASA Astrophysics Data System (ADS)

    Kishore, G. V. K.; Kumar, Anish; Chakraborty, Gopa; Albert, S. K.; Rao, B. Purna Chandra; Bhaduri, A. K.; Jayakumar, T.

    2015-07-01

    Nickel base Ni-Cr alloy variants are extensively used for hardfacing of austenitic stainless steel components in sodium cooled fast reactors (SFRs) to avoid self-welding and galling. Considerable difference in the compositions and melting points of the substrate and the Ni-Cr alloy results in significant dilution of the hardface deposit from the substrate. Even though, both the deposit and the substrate are non-magnetic, the diluted region exhibits ferromagnetic behavior. The present paper reports a systematic study carried out on the variations in microstructures and magnetic behavior of American Welding Society (AWS) Ni Cr-C deposited layers on 316 LN austenitic stainless steels, using atomic force microscopy (AFM) and magnetic force microscopy (MFM). The phase variations of the oscillations of a Co-Cr alloy coated magnetic field sensitive cantilever is used to quantitatively study the magnetic strength of the evolved microstructure in the diluted region as a function of the distance from the deposit/substrate interface, with the spatial resolution of about 100 nm. The acquired AFM/MFM images and the magnetic property profiles have been correlated with the variations in the chemical compositions in the diluted layers obtained by the energy dispersive spectroscopy (EDS). The study indicates that both the volume fraction of the ferromagnetic phase and its ferromagnetic strength decrease with increasing distance from the deposit/substrate interface. A distinct difference is observed in the ferromagnetic strength in the first few layers and the ferromagnetism is observed only near to the precipitates in the fifth layer. The study provides a better insight of the evolution of ferromagnetism in the diluted layers of Ni-Cr alloy deposits on stainless steel.

  11. Corrosion in artificial saliva of a Ni-Cr-based dental alloy joined by TIG welding and conventional brazing.

    PubMed

    Matos, Irma C; Bastos, Ivan N; Diniz, Marília G; de Miranda, Mauro S

    2015-08-01

    Fixed prosthesis and partial dental prosthesis frameworks are usually made from welded Ni-Cr-based alloys. These structures can corrode in saliva and have to be investigated to establish their safety. The purpose of this study was to evaluate the corrosion behavior of joints joined by tungsten inert gas (TIG) welding and conventional brazing in specimens made of commercial Ni-Cr alloy in Fusayama artificial saliva at 37°C (pH 2.5 and 5.5). Eighteen Ni-Cr base metal specimens were cast and welded by brazing or tungsten inert gas methods. The specimens were divided into 3 groups (base metal, 2 welded specimens), and the composition and microstructure were qualitatively evaluated. The results of potential corrosion and corrosion current density were analyzed with a 1-way analysis of variance and the Tukey test for pairwise comparisons (α=.05). Base metal and tungsten inert gas welded material showed equivalent results in electrochemical corrosion tests, while the air-torched specimens exhibited low corrosion resistance. The performance was worst at pH 2.5. These results suggest that tungsten inert gas is a suitable welding process for use in dentistry, because the final microstructure does not reduce the corrosion resistance in artificial saliva at 37°C, even in a corrosion-testing medium that facilitates galvanic corrosion processes. Moreover, the corrosion current density of brazed Ni-Cr alloy joints was significantly higher (P<.001) than the base metal and tungsten inert gas welded joints. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  12. Shear bond strength of aesthetic materials bonded to Ni-Cr alloy.

    PubMed

    Almilhatti, Hercules Jorge; Giampaolo, Eunice Teresinha; Vergani, Carlos Eduardo; Machado, Ana Lúcia; Pavarina, Ana Cláudia

    2003-03-01

    This study was undertaken to evaluate the shear bond strength of four materials used as aesthetic material bonded to Ni-Cr alloy. Sixty-eight alloy discs were prepared and divided equally into four groups, and received four treatments for veneering: conventional feldspathic porcelain (Noritake EX-3) and three light-cured prosthodontic composite resins (Artglass, Solidex and Targis). The aesthetic materials were applied after metal structure conditioning in accordance with the manufacturers' recommendations. The specimens were stored in distilled water at 37 degrees C for 7 days. A universal testing machine was used to measure the shear bond strength of the specimens at a cross head speed of 0.5 mm/min. Fractured specimens were examined by using both optical and scanning electron microscope. The analysis of variance and Tukey's test showed that the strongest mean shear bond was obtained with Noritake EX-3 (mean shear bond strength 42.90+/-7.82 MPa). For composites, the highest mean shear bond strength was observed for Targis (12.30+/-1.57 MPa); followed by Solidex (11.94+/-1.04 MPa) and Artglass (10.04+/-0.75 MPa). Optical analysis of the fractured surfaces indicated that for Targis and Noritake EX-3 all failures were a mixture of both cohesive and adhesive patterns. As for Artglass and Solidex, the fractures were mainly adhesive in nature. The Solidex system was equivalent to the Targis system in bond strength and exhibited greater strength than the Artglass system. The porcelain fused-to-metal showed considerably higher shear bond strength than the three metal-resin bonding techniques.

  13. Effects of point defect concentrations of the reactive element oxides on the oxidation kinetics of pure Ni and Ni-Cr alloys

    NASA Astrophysics Data System (ADS)

    Yan, Ruey-Fong

    The addition of some reactive element oxides, e.g. Ysb2Osb3 or ZrOsb2, has significant effects, e.g. improvement in scale adhesion and reduction in oxidation rate, on the oxidation behavior of chromia and alumina scale forming alloys at high temperatures. However, there is little agreement about how a small addition of an oxygen-active element can cause such profound effects. It was the goal of this project to study the growth kinetics of an oxide scale when different reactive-element oxides were added to pure Ni and Ni-Cr alloys and, consequently, to aid in clarifying the mechanism of reactive element effects. The oxidation kinetics were measured using a thermogravimetric analysis (TGA) method and the material characterization of oxide scale was conducted. The relationship between point defect structures and oxidation kinetics was discussed. The results in this research showed that Ysb2Osb3 and ZrOsb2 exhibited the reactive element effects on the oxidation behaviors of Ni and Ni-Cr alloys. In addition, the point defect concentrations of the reactive element oxide, Ysb2Osb3, were changed by doping of different valent oxides. The modification of point defect concentrations of the reactive element oxide dispersed phases did change the oxidation kinetics of the pure Ni and Ni-Cr alloys containing Ysb2Osb3. These results indicate that the transport properties of the reactive element oxide dispersed phases are one of the important factors in determining the growth rate of an oxide scale.

  14. 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.

  15. 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.

  16. Interfacial segregation in oxide scales on NiCrAl-based alloys

    SciTech Connect

    Pruessner, K.; Alexander, K.B.; Pint, B.A.; Tortorelli, P.F.; Wright, I.G.

    1997-04-01

    Previous studies addressing the segregation of reactive elements in protective oxide scales and their beneficial effect on scale adhesion have primarily concentrated on primary alumina-formers. In this study the isothermal oxidation behavior of three NiCrAl alloys, which form complex oxide scales was studied in air at 1,473 K for 100 hrs. The resulting oxide scales were characterized by scanning electron microscopy (SEM) and cross=sectional transmission electron microscopy (TEM) techniques. Segregation at internal interfaces was analyzed in the STEM mode on a Philips CM200 FEG-TEM, operated at 200 kV and equipped with a Link ultrathin-window EDS detector. The probe size of the electron beam was about 1.5 nm. Spectra were recorded with grain boundaries oriented parallel to the electron beam. The oxide scale on Rene N5 ({approximately}5 {micro}m) consists of columnar {alpha}-Al{sub 2}O{sub 3} at the bottom ({approximately}4 {micro}m) and a mixed layer of spinel (Ni, Co, Ta) (Al,Cr){sub 2}O{sub 4} and {alpha}-Al{sub 2}O{sub 3} ({approximately}1 {micro}m) at the top. On Ni-7Cr-6.5Al+Y, the scale ({approximately}9 {micro}m) consists mainly of columnar Cr-doped {alpha}-Al{sub 2}O{sub 3}. Ni-10Cr-10Al+Y forms an oxide scale ({approximately}8 {micro}m) that consists mainly of columnar Cr-doped {alpha}-Al{sub 2}O{sub 3}. The results are consistent with previous results on primary alumina-formers.

  17. Interdiffusion in (fcc) Ni-Cr-X (X = Al, Si, Ge or Pd) Alloys at 700?aC

    SciTech Connect

    Garimella, N; Brady, Michael P; Sohn, Yong Ho

    2007-01-01

    Interdiffusion at 700 aC for Ni-22at.%Cr (fcc ^ phase) alloys with small additions of Al, Si, Ge, or Pd was examined using solid-to-solid diffusion couples. Rods of Ni-22at.%Cr, Ni-21at.%Cr-6.2at.%Al, Ni-22at.%Cr-4.0at.%Si, Ni-22at.%Cr-1.6at.%Ge and Ni-22at.%Cr-1.6at.%Pd alloys were cast using arc-melt and homogenized at 900 aC for 168 hours. The diffusion couples were assembled with alloy disks in Invar steel jig, encapsulated in Argon after several hydrogen flushes, and annealed at 700 XC for 720 hours. Experimental concentration profiles were determined from polished cross-sections by using electron probe microanalysis with pure standards of Ni, Cr, Al, Si, Ge and Pd. Interdiffusion fluxes of individual components were calculated directly from the experimental concentration profiles, and the moments of interdiffusion fluxes were examined to determine average ternary interdiffusion coefficients. Effects of ternary alloying additions on the interdiffusional behavior of Ni-Cr-X alloys at 700 XC are presented in the light of the diffusional interactions and the formation of protective Cr2O3 scale.

  18. Ternary and Quaternary Interdiffusion in ? (fcc) Fe-Ni-Cr-X (X = Si, Ge) Alloys at 900?C

    SciTech Connect

    Garimella, N; Brady, Michael P; Sohn, Yong Ho

    2008-01-01

    Interdiffusion in Fe-Ni-Cr (fcc phase) alloys with small additions of Si and Ge at 900 C was studied using solid-to-solid diffusion couples. Alloy rods of Fe-24 at.%Ni, Fe-24 at.%Ni- 22at.%Cr, Fe-24 at.%Ni-22at.%Cr-4at.%Si and Fe-24 at.%Ni-22at.%Cr-1.7at.%Ge were cast using arc-melt, and homogenized at 900 C for 168 hours. Sectioned alloy disks from the rods were polished, and diffusion couples were assembled with in Invar steel jig, encapsulated in Argon after several hydrogen flushes, and annealed atz 900 C for 168 hours. Polished cross-sections of the diffusion couples were characterized to determine experimental concentration profiles using electron probe microanalysis with pure elemental standards. Interdiffusion fluxes of individual components were calculated directly from the experimental concentration profiles, and the moments of interdiffusion flux profiles were examined to determine the average ternary and quaternary interdiffusion coefficients. Effects of alloying additions on the interdiffusional behavior of Fe-Ni- Cr-X alloys at 900 C are presented with due consideration for the formation of protective Cr2O3 scale.

  19. The effect of Mn on the activities of Fe, Ni, and Cr in an Fe-Ni-Cr base alloy

    SciTech Connect

    Lee, M.C.Y. . Div. of Mineral Commodities)

    1993-11-01

    A combination Knudsen cell-mass spectrometer apparatus developed by the Bureau of Mines is accurate enough to permit the activity of many alloy components to be measured directly as the ratio of the ion currents of an appropriate isotope evaporated from the alloy and from the pure component. This apparatus has been used to determine the activities of Fe, Ni, and Cr as functions of temperature in 71Fe-20Ni-6Cr-3Mn (at. pct). A comparison of the data with data obtained earlier from other Fe-Ni-Cr base alloys indicates that partial substitution of Mn for Cr causes the activity coefficient of Fe to decrease and to deviate negatively above 1,550 K. The activity coefficient of Ni is markedly increased by the substitution decreases both the activity coefficient of Cr and the temperature dependence of this coefficient. The oxidation behavior of Fe-Ni-Cr base alloys, the stability of the austenitic phase in such alloys, and the Ni equivalent of Mn are discussed in light of these changes in activity coefficient.

  20. A Comparison between Shear Bond Strength of VMK Master Porcelain with Three Base-metal Alloys (Ni-cr-T3, VeraBond, Super Cast) and One Noble Alloy (X-33) in Metal-ceramic Restorations

    PubMed Central

    Ahmadzadeh, A; Neshati, A; Mousavi, N; Epakchi, S; Dabaghi Tabriz, F; Sarbazi, AH

    2013-01-01

    Statement of Problem: The increase in the use of metal-ceramic restorations and a high prevalence of porcelain chipping entails introducing an alloy which is more compatible with porcelain and causes a stronger bond between the two. This study is to compare shear bond strength of three base-metal alloys and one noble alloy with the commonly used VMK Master Porcelain. Materials and Method: Three different groups of base-metal alloys (Ni-cr-T3, Super Cast, and VeraBond) and one group of noble alloy (X-33) were selected. Each group consisted of 15 alloy samples. All groups went through the casting process and change from wax pattern into metal disks. The VMK Master Porcelain was then fired on each group. All the specimens were put in the UTM; a shear force was loaded until a fracture occurred and the fracture force was consequently recorded. The data were analyzed by SPSS Version 16 and One-Way ANOVA was run to compare the shear strength between the groups. Furthermore, the groups were compared two-by-two by adopting Tukey test. Results: The findings of this study revealed shear bond strength of Ni-Cr-T3 alloy was higher than the three other alloys (94 MPa or 330 N). Super Cast alloy had the second greatest shear bond strength (80. 87Mpa or 283.87 N). Both VeraBond (69.66 MPa or 245 N) and x-33 alloys (66.53 MPa or 234 N) took the third place. Conclusion: Ni-Cr-T3 with VMK Master Porcelain has the greatest shear bond strength. Therefore, employment of this low-cost alloy is recommended in metal-ceramic restorations. PMID:24724144

  1. Thoria stability in TD-NiCr at high temperatures in the presence of chromium in solution.

    NASA Technical Reports Server (NTRS)

    Dalal, H.; Grant, N. J.

    1973-01-01

    Study of the influence of chromium in solid solution on the coarsening of ThO2 in TD-NiCr. Comparisons were made of ThO2 coarsening in chromium-free TD-Ni and in TD-NiCr, which is known to be low in Cr2O3 as a contaminant. The results of these comparisons indicate that the presence of 20% Cr in solid solution in a nickel-base alloy does not lead to a more rapid coarsening of ThO2 at temperatures of at least 2462 deg F (1350 deg C).

  2. Thoria stability in TD-NiCr at high temperatures in the presence of chromium in solution.

    NASA Technical Reports Server (NTRS)

    Dalal, H.; Grant, N. J.

    1973-01-01

    Study of the influence of chromium in solid solution on the coarsening of ThO2 in TD-NiCr. Comparisons were made of ThO2 coarsening in chromium-free TD-Ni and in TD-NiCr, which is known to be low in Cr2O3 as a contaminant. The results of these comparisons indicate that the presence of 20% Cr in solid solution in a nickel-base alloy does not lead to a more rapid coarsening of ThO2 at temperatures of at least 2462 deg F (1350 deg C).

  3. [Study on grinding of base metal alloys. 4. Constant pressure grinding of a Ni-Cr alloy with vitrified wheels].

    PubMed

    Miyakawa, O; Watanabe, K; Okawa, S; Nakano, S; Shiokawa, N; Kobayashi, M; Tamura, H

    1989-09-01

    The grinding techniques and the constituent element of vitrified wheels suitable for a 13% Cr-Ni dental casting alloy were determined. The lever-type grinding test machine used in the previous study was modified so that a work might be ground under a constant pressure as it moved reciprocally within a short stroke along the tangential direction of a rotating wheel. The grinding performance of two marketed wheels and eleven experimental wheels with different constituent elements was tested. Abrasive grains on the working surface of alumina wheel wore extremely due to abrasive attrition. Carborundum wheels proved to be more suitable for grinding of the comparatively soft Ni-Cr alloy. Not only depressing a wheel against a work but also moving the wheel over it with heavier pressure should be desired for the maximal grinding efficiency. The experimental carborundum wheels exhibited much the same performance as the marketed carborundum wheel under a less grinding pressure that 100 gf. Only the wheel of grain size #150 bonded with 19% binder wore obviously under the pressure of 150 or 200 gf and provided about two times the performance of the marketed wheel.

  4. Evaluation of marginal and internal gaps of Ni-Cr and Co-Cr alloy copings manufactured by microstereolithography

    PubMed Central

    Kim, Dong-Yeon; Kim, Chong-Myeong; Kim, Hae-Young

    2017-01-01

    PURPOSE The purpose of this study was to evaluate the marginal and internal gaps of Ni-Cr and Co-Cr copings, fabricated using the dental µ-SLA system. MATERIALS AND METHODS Ten study dies were made using a two-step silicone impression with a dental stone (type IV) from the master die of a tooth. Ni-Cr (NC group) and Co-Cr (CC group) alloy copings were designed using a dental scanner, CAD software, resin coping, and casting process. In addition, 10 Ni-Cr alloy copings were manufactured using the lost-wax technique (LW group). The marginal and internal gaps in the 3 groups were measured using a digital microscope (160 ×) with the silicone replica technique, and the obtained data were analyzed using the non-parametric Kruskal-Wallis H test. Post-hoc comparisons were performed using Bonferroni-corrected Mann-Whitney U tests (α=.05). RESULTS The mean (±standard deviation) values of the marginal, chamfer, axial wall, and occlusal gaps in the 3 groups were as follows: 81.5±73.8, 98.1±76.1, 87.1±44.8, and 146.8±78.7 µm in the LW group; 76.8±48.0, 141.7±57.1, 80.7±47.5, and 194.69±63.8 µm in the NC group; and 124.2±52.0, 199.5±71.0, 67.1±37.6, and 244.5±58.9 µm in the CC group. CONCLUSION The marginal gap in the LW and NC groups were clinically acceptable. Further improvement is needed for CC group to be used clinical practice. PMID:28680548

  5. Evaluation of marginal and internal gaps of Ni-Cr and Co-Cr alloy copings manufactured by microstereolithography.

    PubMed

    Kim, Dong-Yeon; Kim, Chong-Myeong; Kim, Ji-Hwan; Kim, Hae-Young; Kim, Woong-Chul

    2017-06-01

    The purpose of this study was to evaluate the marginal and internal gaps of Ni-Cr and Co-Cr copings, fabricated using the dental µ-SLA system. Ten study dies were made using a two-step silicone impression with a dental stone (type IV) from the master die of a tooth. Ni-Cr (NC group) and Co-Cr (CC group) alloy copings were designed using a dental scanner, CAD software, resin coping, and casting process. In addition, 10 Ni-Cr alloy copings were manufactured using the lost-wax technique (LW group). The marginal and internal gaps in the 3 groups were measured using a digital microscope (160 ×) with the silicone replica technique, and the obtained data were analyzed using the non-parametric Kruskal-Wallis H test. Post-hoc comparisons were performed using Bonferroni-corrected Mann-Whitney U tests (α=.05). The mean (±standard deviation) values of the marginal, chamfer, axial wall, and occlusal gaps in the 3 groups were as follows: 81.5±73.8, 98.1±76.1, 87.1±44.8, and 146.8±78.7 µm in the LW group; 76.8±48.0, 141.7±57.1, 80.7±47.5, and 194.69±63.8 µm in the NC group; and 124.2±52.0, 199.5±71.0, 67.1±37.6, and 244.5±58.9 µm in the CC group. The marginal gap in the LW and NC groups were clinically acceptable. Further improvement is needed for CC group to be used clinical practice.

  6. Effect of minor alloying elements La, C and B on the cyclic oxidation behavior of Ni-Cr-W-Mo superalloys

    NASA Astrophysics Data System (ADS)

    Yun, Dae Won; Seo, Seong Moon; Jeong, Hi Won; Yoo, Young Soo

    2017-09-01

    The cyclic oxidation behavior of Ni-Cr-W-Mo base alloys with various La, C and B contents is investigated at 1150 °C in ambient air with 15 min of high-temperature exposure and 5 min of air cooling. Oxidation resistance is evaluated by the weight change during cyclic oxidation. The cross-section of the oxide scale is observed by scanning electron microscopy after the cyclic oxidation test. The oxide scale mainly consists with spinels and a chromia layer. NiWO4 oxide particles and NiO are also observed in some areas. The addition of La improves the cyclic oxidation resistance significantly. However, the addition of 0.03 wt% B reduces the beneficial effect of La. The additions of B and C increase the spallation at the initial stage such that severe weight loss is observed. However, the spallation is reduced at the later stage. The addition of a proper amounts of B and C can be beneficial to improve the cyclic oxidation resistance of Ni-Cr-W-Mo alloys.

  7. Trace element effects on ductility and fracture of Ni-Cr-Ce alloys

    NASA Astrophysics Data System (ADS)

    Cosandey, F.; Kandra, J.

    1987-07-01

    The effect of trace additions of Ce, ranging from Oto 180 at. ppm, on the tensile behavior of a Ni-20Cr alloy is presented. For alloys without Ce a transition from ductile transgranular to brittle intergranular fracture mode is observed at high temperatures and for low strain-rate tests. Additions of Ce suppress this transition with a resulting increase in ductility. Maximum effects are observed for temperature and strain rate values where fracture in Ce-free alloys occurs via grain boundary cavitation. The reduced cavitation rate of Ce-containing alloys is suggested to be the result of an increase in both interfacial energy and grain boundary mobility.

  8. [Study on grinding of base metal alloys. 5. Constant pressure grinding of a Ni-Cr alloy with electro-deposited wheels].

    PubMed

    Miyakawa, O; Watanabe, K; Okawa, S; Nakano, S; Shiokawa, N; Kobayashi, M; Tamura, H

    1989-09-01

    The grinding techniques and electro-deposited wheels suitable for a 13% Cr-Ni dental casting alloy were determined. The lever-type grinding test machine modified in the previous study was used to investigate the grinding performance of experimental wheels of CBN- and diamond-particles. Depression of the diamond wheel against the work yielded unfavorable grinding results. Not only depression of the wheel against it but also moving the wheel over it with a heavier pressure is desired for higher grinding efficiency and its durability. Probably, the undurability of this wheel is associated with abrasive attrition due to oxidation or some chemical reaction with the work. The CBN wheel had not been suitable for the Co-Cr alloy tested in the third paper, but it exhibited very excellent performance for grinding of the Ni-Cr alloy, even without being moved over the work. Although being high in cost, the CBN wheel may pay for the very high performance and its durability.

  9. Supersonic Plasma Spray Deposition of CoNiCrAlY Coatings on Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Caliari, F. R.; Miranda, F. S.; Reis, D. A. P.; Essiptchouk, A. M.; Filho, G. P.

    2017-06-01

    Plasma spray is a versatile technology used for production of environmental and thermal barrier coatings, mainly in the aerospace, gas turbine, and automotive industries, with potential application in the renewable energy industry. New plasma spray technologies have been developed recently to produce high-quality coatings as an alternative to the costly low-pressure plasma-spray process. In this work, we studied the properties of as-sprayed CoNiCrAlY coatings deposited on Ti-6Al-4V substrate with smooth surface ( R a = 0.8 μm) by means of a plasma torch operating in supersonic regime at atmospheric pressure. The CoNiCrAlY coatings were evaluated in terms of their surface roughness, microstructure, instrumented indentation, and phase content. Static and dynamic depositions were investigated to examine their effect on coating characteristics. Results show that the substrate surface velocity has a major influence on the coating properties. The sprayed CoNiCrAlY coatings exhibit low roughness ( R a of 5.7 μm), low porosity (0.8%), excellent mechanical properties ( H it = 6.1 GPa, E it = 155 GPa), and elevated interface toughness (2.4 MPa m1/2).

  10. Effect of Chemistry Variations in Plate and Weld Filler Metal on the Corrosion Performance of Ni-Cr-Mo Alloys

    SciTech Connect

    Fix, D V; Rebak, R B

    2006-02-05

    The ASTM standard B 575 provides the requirements for the chemical composition of Nickel-Chromium-Molybdenum (Ni-Cr-Mo) alloys such as Alloy 22 (N06022) and Alloy 686 (N06686). The compositions of each element are given in a range. For example, the content of Mo is specified from 12.5 to 14.5 weight percent for Alloy 22 and from 15.0 to 17.0 weight percent for Alloy 686. It was important to determine how the corrosion rate of welded plates of Alloy 22 using Alloy 686 weld filler metal would change if heats of these alloys were prepared using several variations in the composition of the elements even though still in the range specified in B 575. All the material used in this report were especially prepared at Allegheny Ludlum Co. Seven heats of plate were welded with seven heats of wire. Immersion corrosion tests were conducted in a boiling solution of sulfuric acid plus ferric sulfate (ASTM G 28 A) using both as-welded (ASW) coupons and solution heat-treated (SHT) coupons. Results show that the corrosion rate was not affected by the chemistry of the materials in the range of the standards.

  11. Numerical simulation of temperature distribution and TiC growth kinetics for high power laser clad TiC/NiCrBSiC composite coatings

    NASA Astrophysics Data System (ADS)

    Lei, Yiwen; Sun, Ronglu; Tang, Ying; Niu, Wei

    2012-06-01

    A three dimensional model was proposed to simulate high power laser clad TiC/NiCrBSiC composite coatings on Ti6Al4V alloys. The temperature distribution, temperature curves on different nodes, three dimensional shape and size of TiC melting region, molten pool and heat affected zone (HAZ) of the substrate were obtained. To have a clear physical insight into the phase transformation and microstructure evolution in the coatings during laser cladding process, a theoretical kinetic analysis was performed to elucidate the nucleation, growth velocity, and size of TiC particles on the basis of simulated temperature curves of the molten pool. A good quality TiC/NiCrBSiC composite coating with low dilution rate and excellent metallurgical bond was fabricated under optimal processing parameters using powder mixture of TiC and NiCrBSiC as clad material and cuboid of Ti6Al4V alloys as substrate. To validate the reliability of the proposed model, the theoretical results were compared with the microstructure of the coatings. It shows that these theoretical results are in excellent agreement with the experiment cases.

  12. O-18 tracer studies of Al2O3 scale formation on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Reddy, K. P. R.; Cooper, A. R.; Smialek, J. L.

    1982-01-01

    Diffusion processes in Al2O3 scales formed on NiCrAl + Zr alloys were studied by the proton activation technique employing the O-18 isotope as a tracer. The O-18 profiles identified a zone of oxide penetration beneath the external scale. Both this subscale formation and the outer Al2O3 scale thickness were shown by this technique to increase with Zr content in the alloy. Estimated kp's from scale thicknesses were in agreement with gravimetric measurements for various Zr levels. Alternate exposures in O-16 and O-18 revealed that oxygen inward transport was the primary growth mechanism. A qualitative analysis of these O-18 profiles indicated that the oxygen transport was primarily via short-circuit paths, such as grain boundaries.

  13. Thermally activated dislocation creep model for primary water stress corrosion cracking of NiCrFe alloys

    SciTech Connect

    Hall, M.M., Jr

    1995-12-31

    There is a growing awareness that awareness that environmentally assisted creep plays an important role in integranular stress corrosion cracking (IGSCC) of NiCrFe alloys in the primary coolant water environment of a pressurized water reactor (PWR). The expected creep mechanism is the thermally activated glide of dislocations. This mode of deformation is favored by the relatively low temperature of PWR operation combined with the large residual stresses that are most often identified as responsible for the SCC failure of plant components. Stress corrosion crack growth rate (CGR) equations that properly reflect the influence of this mechanism of crack tip deformation are required for accurate component life predictions. A phenomenological IGSCC-CGR model, which is based on an apriori assumption that the IGSCC-CGR is controlled by a low temperature dislocation creep mechanism, is developed in this report. Obstacles to dislocation creep include solute atoms such as carbon, which increase the lattice friction force, and forest dislocations, which can be introduced by cold prestrain. Dislocation creep also may be environmentally assisted due to hydrogen absorption at the crack tip. The IGSCC-CGR model developed here is based on an assumption that crack growth occurs by repeated fracture events occurring within an advancing crack-tip creep-fracture zone. Thermal activation parameters for stress corrosion cracking are obtained by fitting the CGR model to IGSCC-CGR data obtained on NiCrFe alloys, Alloy X-750 and Alloy 600. These IGSCC-CGR activation parameters are compared to activation parameters obtained from creep and stress relaxation tests. Recently reported CGR data, which exhibit an activation energy that depends on yield stress and the applied stress intensity factor, are used to benchmark the model. Finally, the effects of matrix carbon concentration, grain boundary carbides and absorbed hydrogen concentration are discussed within context of the model.

  14. Interdiffusion in Ni-rich, Ni-Cr-Al alloys at 1100 and 1200 C. I - Diffusion paths and microstructures. II - Diffusion coefficients and predicted concentration profiles

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    Interdiffusion in Ni-rich Ni-Cr-Al alloys is investigated experimentally after annealing at 1100 and 1200 C using gamma/gamma, gamma/gamma+beta, gamma/gamma+gamma prime, and gamma/gamma+alpha diffusion couples. The amount and location of Kirkendall porosity suggests that Al diffuses more rapidly than Cr which diffuses more rapidly than Ni in the gamma phase of Ni-Cr-Al alloys. The location and extent of maxima and minima in the concentration profiles of the diffusion couples indicate that both cross-term diffusion coefficients are positive. Measurements are also presented of the ternary interdiffusion coefficients of the gamma phase in the Ni-Cr-Al system. It is shown that the interdiffusion coefficients can be accurately predicted by using a ternary finite-difference interdiffusion model.

  15. Interdiffusion in Ni-rich, Ni-Cr-Al alloys at 1100 and 1200 C. I - Diffusion paths and microstructures. II - Diffusion coefficients and predicted concentration profiles

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    Interdiffusion in Ni-rich Ni-Cr-Al alloys is investigated experimentally after annealing at 1100 and 1200 C using gamma/gamma, gamma/gamma+beta, gamma/gamma+gamma prime, and gamma/gamma+alpha diffusion couples. The amount and location of Kirkendall porosity suggests that Al diffuses more rapidly than Cr which diffuses more rapidly than Ni in the gamma phase of Ni-Cr-Al alloys. The location and extent of maxima and minima in the concentration profiles of the diffusion couples indicate that both cross-term diffusion coefficients are positive. Measurements are also presented of the ternary interdiffusion coefficients of the gamma phase in the Ni-Cr-Al system. It is shown that the interdiffusion coefficients can be accurately predicted by using a ternary finite-difference interdiffusion model.

  16. The Effect of Manganese Additions on the Reactive Evaporation of Chromium in Ni-Cr Alloys

    SciTech Connect

    Holcomb, Gordon R.; Alman, David E.

    2004-10-20

    Chromium is used as an alloy addition in stainless steels and nickel-chromium alloys to form protective chromium oxide scales. Chromium oxide undergoes reactive evaporation in high temperature exposures in the presence of oxygen and/or water vapor. The deposition of gaseous chromium species onto solid oxide fuel cell electrodes can reduce the efficiency of the fuel cell. Manganese additions to the alloy can reduce the activity of chromium in the oxide, either from solid solution replacement of chromium with manganese (at low levels of manganese) or from the formation of manganese-chromium spinels (at high levels of manganese). This reduction in chromium activity leads to a predicted reduction in chromium evaporation by as much as a factor of 35 at 800 C and 55 at 700 C. The results of evaporation loss measurements on nickel-chromium-manganese alloys are compared with the predicted reduction. Quantifying the effects of manganese additions on chromium evaporation should aid alloy development of metallic interconnects and balance-of-plant alloys.

  17. Growth of Ni and Ni-Cr alloy thin films on MgO(001): Effect of alloy composition on surface morphology

    NASA Astrophysics Data System (ADS)

    Ramalingam, Gopalakrishnan; Reinke, Petra

    2016-12-01

    The effects of substrate treatment, growth temperature, and composition on the surface morphology of Ni-Cr thin films grown on MgO(001) are studied by scanning tunneling microscopy and atomic force microscopy. We demonstrate that a combination of acid-etched substrates and high temperature deposition (400 °C) will result in smooth films with well-defined terraces (up to 30 nm wide) that are suitable for the study of progression of chemical reactions on the surface. Two different treatments are used to prepare the MgO substrates for deposition and they introduce characteristic differences in film surface morphology. Thin films that are grown on the phosphoric acid-treated substrates present reduced nucleation density during the initial stages of film growth which results in long and wide terraces. Due to the ≈16% lattice mismatch in the Ni(001)/MgO(001) system, film growth at 400 °C yields discontinuous films and a two-step growth process is necessary to obtain a continuous layer. Ni films are deposited at 100 °C and subjected to a post-growth annealing at 300 °C for 2 h to obtain a smoother surface. The addition of just 5 wt. % Cr drastically changes the film growth processes and yields continuous films at 400 °C without de-wetting in contrast to pure Ni films. With increasing Cr content, the films become progressively smoother with wider terraces. Ni5Cr alloy thin films have an rms surface roughness of 3.63 ± 0.75 nm, while Ni33Cr thin film is smoother with an rms roughness of only 0.29 ± 0.13 nm. The changes in film growth initiated by alloying with Cr are due to changes in the interfacial chemistry which favorably alters the initial adsorption of the metal atoms on MgO surface and suggests a reduction of the Ehrlich-Schwoebel barrier. The growth of smooth Ni-Cr thin films with a well-defined surface structure opens up a new pathway for a wide range of surface science studies related to alloy performance.

  18. High Temperature Mechanical Properties of Free-Standing HVOF CoNiCrAlY Coatings by Lateral Compression of Circular Tube

    NASA Astrophysics Data System (ADS)

    Waki, Hiroyuki; Nakamura, Kyousuke; Yamaguchi, Itsuki; Kobayashi, Akira

    MCrAlY, M means Co and/or Ni, sprayed coating is used to protect a super alloy substrate from corrosion or oxidation in a gas turbine blade. However, the mechanical properties are not well-known, because there are few proper measurement methods for a thin coating at high temperature. Authors have developed the new easy method to measure the mechanical properties using the lateral compression of a circular tube. The method is useful to apply to a thin coating because it does not need chucking and manufacturing a test piece is very easy. The method is also easily applicable to high temperature measurement. In this study, high temperature mechanical properties, Young's modulus, bending strength and fracture strain, of CoNiCrAlY coatings by HVOF were systematically measured. The results obtained were as follows: Young's modulus and bending strength suddenly decreased beyond 400˜450°C. The Young's modulus and bending strength thermally treated at higher than 1050°C was significantly higher than that of virgin CoNiCrAlY coating. It was found that higher thermal treatment in atmosphere was the most effective in increasing the Young's modulus and bending strength. It was also found that the improvement of Young's modulus was primarily caused by not the effect of TGO but the sintering and diffusion of unfused particles. On the contrary, the fracture strain increased beyond 400°C differently from the bending strength. The fracture strains of CoNiCrAlY thermally treated in vacuum were higher than those of CoNiCrAlY treated in atmosphere. It was found that higher thermal treatment in vacuum was the most effective in increasing the fracture strain.

  19. Environmentally assisted cracking of 3.5NiCrMoV low alloy steel under cyclic straining

    SciTech Connect

    Kondo, Yoshiyuki; Bodai, Masaru; Takei, Mao; Sugita, Yuji; Inagaki, Hironobu

    1997-12-01

    Environmentally assisted cracking of 3.5NiCrMoV low alloy steel under cyclic straining was investigated in water environments at 60 C. Effects of strain range, strain rate, strain hold tie and impurities in the water on the crack initiation life were investigated. The effects of long strain hold time up to 100 hours were studied and found to be especially significant. Lower strain rate, longer strain hold time and higher electric conductivity resulted in shorter crack initiation life. The corrosion current from the strained metal was measured in a simulated electrochemical system to clarify the root cause of the life reduction. Test results showed that higher strain range, lower strain rate, longer strain hold time and higher electric conductivity caused increased charge transfer, which caused shorter crack initiation life. A prediction model for the crack initiation life was proposed based on the charge transfer.

  20. Effect of soldering techniques and gap distance on tensile strength of soldered Ni-Cr alloy joint

    PubMed Central

    Lee, Sang-Yeob

    2010-01-01

    PURPOSE The present study was intended to evaluate the effect of soldering techniques with infrared ray and gas torch under different gap distances (0.3 mm and 0.5 mm) on the tensile strength and surface porosity formation in Ni-Cr base metal alloy. MATERIALS AND METHODS Thirty five dumbbell shaped Ni-Cr alloy specimens were prepared and assigned to 5 groups according to the soldering method and the gap distance. For the soldering methods, gas torch (G group) and infrared ray (IR group) were compared and each group was subdivided by corresponding gap distance (0.3 mm: G3 and IR3, 0.5 mm: G5, IR5). Specimens of the experimental groups were sectioned in the middle with a diamond disk and embedded in solder blocks according to the predetermined distance. As a control group, 7 specimens were prepared without sectioning or soldering. After the soldering procedure, a tensile strength test was performed using universal testing machine at a crosshead speed 1 mm/min. The proportions of porosity on the fractured surface were calculated on the images acquired through the scanning electronic microscope. RESULTS Every specimen of G3, G5, IR3 and IR5 was fractured on the solder joint area. However, there was no significant difference between the test groups (P > .05). There was a negative correlation between porosity formation and tensile strength in all the specimens in the test groups (P < .05). CONCLUSION There was no significant difference in ultimate tensile strength of joints and porosity formations between the gas-oxygen torch soldering and infrared ray soldering technique or between the gap distance of 0.3 mm and 0.5 mm. PMID:21264189

  1. 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.

  2. Processes leading to formation of cube texture in cold-rolled Ni-Cr-W alloy

    NASA Astrophysics Data System (ADS)

    Dosovitskiy, G. A.; Mudretsova, S. N.; Garshev, A. V.; Amelichev, V. A.; Samoilenkov, S. V.; Gervasieva, I. V.; Khlebnikova, Yu. V.; Rodionov, D. P.; Kaul, A. R.

    2014-01-01

    Behavior of cold-rolled fcc Ni88.4Cr9.2W2.4 alloy during heating has been studied. Two consecutive exothermic processes were detected using differential scanning calorimetry, high-temperature X-ray diffraction, and dilatometry. The processes were identified as polygonization and recrystallization, which lead to cube texture formation, as was shown by X-ray diffraction and electron backscatter diffraction. The heat effects of these processes were determined.

  3. Effectiveness of silica-lasing method on the bond strength of composite resin repair to Ni-Cr alloy.

    PubMed

    Madani, Azam S; Astaneh, Pedram Ansari; Nakhaei, Mohammadreza; Bagheri, Hossein G; Moosavi, Horieh; Alavi, Samin; Najjaran, Niloufar Tayarani

    2015-04-01

    The aim of this study was to evaluate the effectiveness of silica-lasing method for improving the composite resin repair of metal ceramic restorations. Sixty Ni-Cr cylindrical specimens were fabricated. The bonding surface of all specimens was airborne-particle abraded using 50 μm aluminum oxide particles. Specimens were divided into six groups that received the following surface treatments: group 1-airborne-particle abrasion alone (AA); group 2-Nd:YAG laser irradiation (LA); group 3-silica coating (Si-CO); group 4-silica-lasing (metal surface was coated with slurry of opaque porcelain and irradiated by Nd:YAG laser) (Si-LA); group 5-silica-lasing plus etching with HF acid (Si-LA-HF); group 6-CoJet sand lased (CJ-LA). Composite resin was applied on metal surfaces. Specimens were thermocycled and tested in shear mode in a universal testing machine. The shear bond strength values were analyzed using ANOVA and Tukey's tests (α = 0.05). The mode of failure was determined, and two specimens in each group were examined by scanning electron microscopy and wavelength dispersive X-ray spectroscopy. Si-CO showed significantly higher shear bond strength in comparison to other groups (p < 0.001). The shear bond strength values of the LA group were significantly higher than those of the AA group (p < 0.05). No significant difference was found among lased groups (LA, Si-LA, Si-LA-HF, CJ-LA; p > 0.05). The failure mode was 100% adhesive for AA, Si-LA, Si-LA-HF, and CJ-LA. LA and Si-CO groups showed 37.5% and 87.5% cohesive failure, respectively. Silica coating of Ni-Cr alloy resulted in higher shear bond strength than those of other surface treatments. © 2014 by the American College of Prosthodontists.

  4. Point defect evolution in Ni, NiFe and NiCr alloys from atomistic simulations and irradiation experiments

    SciTech Connect

    Aidhy, Dilpuneet S.; Lu, Chenyang; Jin, Ke; Bei, Hongbin; Zhang, Yanwen; Wang, Lumin; Weber, William J.

    2015-08-08

    Using molecular dynamics simulations, we elucidate irradiation-induced point defect evolution in fcc pure Ni, Ni0.5Fe0.5, and Ni0.8Cr0.2 solid solution alloys. We find that irradiation-induced interstitials form dislocation loops that are of 1/3 <111>{111}-type, consistent with our experimental results. While the loops are formed in all the three materials, the kinetics of formation is considerably slower in NiFe and NiCr than in pure Ni, indicating that defect migration barriers and extended defect formation energies could be higher in the alloys than pure Ni. As a result, while larger size clusters are formed in pure Ni, smaller and more clusters are observed in the alloys. The vacancy diffusion occurs at relatively higher temperatures than interstitials, and their clustering leads to formation of stacking fault tetrahedra, also consistent with our experiments. The results also show that the surviving Frenkel pairs are composition-dependent and are largely Ni dominated.

  5. Point defect evolution in Ni, NiFe and NiCr alloys from atomistic simulations and irradiation experiments

    DOE PAGES

    Aidhy, Dilpuneet S.; Lu, Chenyang; Jin, Ke; ...

    2015-08-08

    Using molecular dynamics simulations, we elucidate irradiation-induced point defect evolution in fcc pure Ni, Ni0.5Fe0.5, and Ni0.8Cr0.2 solid solution alloys. We find that irradiation-induced interstitials form dislocation loops that are of 1/3 <111>{111}-type, consistent with our experimental results. While the loops are formed in all the three materials, the kinetics of formation is considerably slower in NiFe and NiCr than in pure Ni, indicating that defect migration barriers and extended defect formation energies could be higher in the alloys than pure Ni. As a result, while larger size clusters are formed in pure Ni, smaller and more clusters are observedmore » in the alloys. The vacancy diffusion occurs at relatively higher temperatures than interstitials, and their clustering leads to formation of stacking fault tetrahedra, also consistent with our experiments. The results also show that the surviving Frenkel pairs are composition-dependent and are largely Ni dominated.« less

  6. Evaluation and comparison of castability between an indigenous and imported Ni-Cr alloy.

    PubMed

    Ramesh, Ganesh; Padmanabhan, T V; Ariga, Padma; Subramanian, R

    2011-01-01

    Since 1907 casting restorations have been in use in dentistry. Numerous companies have been manufacturing and marketing base metal alloys. Gold was a major component of casting alloys. But alloys with less than 65% gold tarnished easily and the increase in cost of gold post-1970s lead to the revival of base metal alloys such as nickel-chromium and cobalt-chromium alloys which were in use since 1930s. This study was conducted to evaluate and compare the castability between an indigenous alloy and an imported alloy, as imported base metal alloys are considered to be expensive for fabrication of crowns and bridges. This study was conducted to evaluate and compare the castability (for the accurate fabrication of crowns and bridges) between an indigenous base metal alloy-Non-ferrous Materials Technology Development Centre (NFTDC), Hyderabad (Alloy A) -and an imported base metal alloys (Alloy B). Castability measurement was obtained by counting the number of completely formed line segments surrounding the 81 squares in the pattern and later calculating the percentage values. The percentage obtained was taken as the castability value for a particular base metal alloy. The percentage of castability was determined by counting only the number of completely cast segments in a perfect casting (81 × 2 = 162), and then multiplying the resulting fraction by 100 to give the percentage completeness. The Student t-test was used. When the castability of alloys A and B was compared, the calculated value was less than the tabular value (1.171 < 2.048) leading to the conclusion that castability between alloys A and B is insignificant. Therefore we conclude that both the alloys have the same castability. Using the above-mentioned materials and following the method to test castability, we were able to derive favorable results. As the results were satisfactory, we can conclude that the castability of the indigenous alloy is on par with the imported alloy.

  7. 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.

  8. Reduced Pressure Electron Beam Welding Evaluation Activities on a Ni-Cr-Mo Alloy for Nuclear Waste Packages

    SciTech Connect

    Wong, F; Punshon, C; Dorsch, T; Fielding, P; Richard, D; Yang, N; Hill, M; DeWald, A; Rebak, R; Day, S; Wong, L; Torres, S; McGregor, M; Hackel, L; Chen, H-L; Rankin, J

    2003-09-11

    The current waste package design for the proposed repository at Yucca Mountain Nevada, USA, employs gas tungsten arc welding (GTAW) in fabricating the waste packages. While GTAW is widely used in industry for many applications, it requires multiple weld passes. By comparison, single-pass welding methods inherently use lower heat input than multi-pass welding methods which results in lower levels of weld distortion and also narrower regions of residual stresses at the weld TWI Ltd. has developed a Reduced Pressure Electron Beam (RPEB) welding process which allows EB welding in a reduced pressure environment ({le} 1 mbar). As it is a single-pass welding technique, use of RPEB welding could (1) achieve a comparable or better materials performance and (2) lead to potential cost savings in the waste package manufacturing as compared to GTAW. Results will be presented on the initial evaluation of the RPEB welding on a Ni-Cr-Mo alloy (a candidate alloy for the Yucca Mountain waste packages) in the areas of (a) design and manufacturing simplifications, (b) material performance and (c) weld reliability.

  9. Influence of the thermodynamic parameters on the temper embrittlement of SA508 Gr.4N Ni-Cr-Mo low alloy steel with variation of Ni, Cr and Mn contents

    NASA Astrophysics Data System (ADS)

    Park, Sang-Gyu; Lee, Ki-Hyoung; Min, Ki-Deuk; Kim, Min-Chul; Lee, Bong-Sang

    2012-07-01

    It is well known that SA508 Gr.4N low alloy steel offers improved fracture toughness and strength compared to commercial low alloy steels such as SA508 Gr.3 Mn-Mo-Ni low alloy steel. In this study, the effects of Cr, Mn, and Ni on temper embrittlement in SA508 Gr.4N low alloy steel were evaluated from the viewpoint of thermodynamic parameters such as P diffusivity and C activity. The changes of the ductile-brittle transition temperatures before and after aging were correlated with varying alloying element content, and the diffusivity of P and the activity of C were calculated and correlated with the transition behaviors. The addition of Ni, Cr, and Mn reduce the resistance to temper embrittlement, showing increased Transition-Temperature Shift (TTS) and an increased fraction of intergranular fracture. Although the diffusivity of P is changed by the addition of alloying elements, it does not considerably affect the temper embrittlement. The Mn and Cr content in the matrix significantly reduce the C activity, with showing an inversely proportional relationship to TTS. The change of susceptibility to temper embrittlement caused by Cr and Mn addition could be explained by the variation of C activity. Unlike Cr and Mn, Ni has little effect on the temper embrittlement and C activity.

  10. 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.

  11. Transient Liquid Phase Bonding of Nickel-Base Single Crystal Alloy with a Novel Ni-Cr-Co-Mo-W-Ta-Re-B Amorphous Interlayer

    NASA Astrophysics Data System (ADS)

    Guo, Wei; Wang, Haiyan; Jia, Qiang; Peng, Peng; Zhu, Ying

    2017-07-01

    A novel Ni-Cr-Co-W-Mo-Ta-Re-B alloy consisting of plate γ and M23B6 phases was prepared as interlayer for the transient liquid phase (TLP) bonding of Rene' N5 nickel-base single crystal superalloy. The molten Ni-Cr-Co-W-Mo-Ta-Re-B alloy exhibited an excellent wettability on the nickel-base superalloy. The TLP bonding experiment has been carried out in vacuum furnace at 1,240 ° for 12 h and followed by post-weld heat treatment (PWHT) at 1,305 ° for 4 h. PWHT eliminated the intermetallic compounds and promoted the formation of γ´ precipitates in the bonding region. A more uniform microhardness profile of TLP joint was found after PWHT. The shear strength of the joint after PWHT significantly increased to 533.4 MPa compared with the value of 437.2 MPa without PWHT.

  12. Fractal study of Ni Cr Mo alloy for dental applications: effect of beryllium

    NASA Astrophysics Data System (ADS)

    Eftekhari, Ali

    2003-12-01

    Different Ni-based alloys with various compositions were prepared by varying the amounts of beryllium. Effect of the amount of beryllium added to the alloy on its corrosion in an electrolyte solution of artificial saliva was investigated. Fractal dimension was used as a quantitative factor for surface analysis of the alloys before and after storage in the artificial salvia. The fractal dimensions of the electrode surfaces were determined by means of the most reliable method in this context viz. time dependency of the diffusion-limited current for a system involving "diffusion towards electrode surface". The results showed that increase of the beryllium amount in the alloy composition significantly increases the alloy corrosion. It is accompanied by increase of the fractal dimension and roughness of the electrode surface, whereas a smooth and shiny surface is required for dentures. From the methodology point of view, the approach utilized for fractal analysis of the alloy surfaces (Au-masking of metallic surfaces) is a novel and efficient method for study of denture surfaces. Generally, this approach is of interest for corrosion studies of different metals and alloys, particularly where changes in surface structure have a significant importance.

  13. Optimization of Arc-Sprayed Ni-Cr-Ti Coatings for High Temperature Corrosion Applications

    NASA Astrophysics Data System (ADS)

    Matthews, S.; Schweizer, M.

    2013-04-01

    High Cr content Ni-Cr-Ti arc-spray coatings have proven successful in resisting the high temperature sulfidizing conditions found in black liquor recovery boilers in the pulp and paper industry. The corrosion resistance of the coatings is dependent upon the coating composition, to form chromium sulfides and oxides to seal the coating, and on the coating microstructure. Selection of the arc-spray parameters influences the size, temperature and velocity of the molten droplets generated during spraying, which in turn dictates the coating composition and formation of the critical coating microstructural features—splat size, porosity and oxide content. Hence it is critical to optimize the arc-spray parameters in order to maximize the corrosion resistance of the coating. In this work the effect of key spray parameters (current, voltage, spray distance and gas atomizing pressure) on the coating splat thickness, porosity content, oxide content, microhardness, thickness, and surface profile were investigated using a full factorial design of experiment. Based on these results a set of oxidized, porous and optimized coatings were prepared and characterized in detail for follow-up corrosion testing.

  14. Observation of changes in the metallurgical characteristics of Ni-Cr alloys using Nd:YAG laser welding.

    PubMed

    Hong, Mh; Choi, Sm

    2014-01-01

    This study aimed to determine the effect of hardness change according to penetration depth in the laser fusing zone and observed the correlation of the microstructure as an Nd:YAG laser was irradiated to Ni-Cr alloy for dental use by setting the spot diameter size to various conditions. In all groups, the hardness depth profiles in the laser fusing zone and heat-affected zone (HAZ) had larger values than those of the base metal. In addition, the hardness values in places beyond the fusing zone and the HAZ were measured as being quantitatively lower. The observation result of the diffusion of the constituent elements and microstructure using field emission scanning electron microscopy, energy-dispersive spectroscopy, and electron probe microanalyzer showed that the fusing zone revealed a much finer dendritic form than the base metal due to the self-quenching effect after welding, while no change in constituent elements was found although some evaporation of the main elements was observed. In addition, Mo- and Si-combined intermetallic compounds were formed on the interdendritic area. Through this study, the laser fusing zone had better hardenability due to the intermetallic compound and grain refinement effect.

  15. Observation of changes in the metallurgical characteristics of Ni-Cr alloys using Nd:YAG laser welding

    PubMed Central

    Choi, SM

    2014-01-01

    This study aimed to determine the effect of hardness change according to penetration depth in the laser fusing zone and observed the correlation of the microstructure as an Nd:YAG laser was irradiated to Ni-Cr alloy for dental use by setting the spot diameter size to various conditions. In all groups, the hardness depth profiles in the laser fusing zone and heat-affected zone (HAZ) had larger values than those of the base metal. In addition, the hardness values in places beyond the fusing zone and the HAZ were measured as being quantitatively lower. The observation result of the diffusion of the constituent elements and microstructure using field emission scanning electron microscopy, energy-dispersive spectroscopy, and electron probe microanalyzer showed that the fusing zone revealed a much finer dendritic form than the base metal due to the self-quenching effect after welding, while no change in constituent elements was found although some evaporation of the main elements was observed. In addition, Mo- and Si-combined intermetallic compounds were formed on the interdendritic area. Through this study, the laser fusing zone had better hardenability due to the intermetallic compound and grain refinement effect. PMID:25342985

  16. Modeling of Crevice Corrosion Stability of a NiCrMo Alloy and Stainless Steel

    SciTech Connect

    F.J. Presuel-Moreno; F. Bocher; J.R. Scully; R.G. Kelly

    2006-05-19

    Damage of structural significance from crevice corrosion of corrosion resistant alloys requires that at least a portion of the creviced area remain active over a sufficiently long period. Stifling results shen the aggressive chemistry required inside the crevice to keep the material depassivated, i.e., actively corroding, cannot be maintained. This loss of critical chemistry occurs when the rate of mass transport out of the crevice exceeds the rate of dissolution and subsequent hydrolysis of metal ions inside the crevice. For the treatment considered here, the mass transport conditions are constant for a given geometry and potential. What then controls the stability of the internal chemistry is the interaction between the electrochemical kinetics at the interface and the crevice chemistry composition. This work focuses on the parameters that control the stability of crevice corrosion by modeling the evolution of the chemical and electrochemical conditions within a crevice open only at one end (e.g. the mouth) in which the entire crevice is initially filled with the Critical Chemistry Solution (CCS) or filled with chemistries slightly less or more aggressive than the CCS. The crevice mouth is in contact with a weak acid solution (pH 3) that provides the boundary conditions at the crevice mouth. The potential at the mouth was held constant at +0.1 V{sub sce} in most instances with selected cases held at 0.0 V{sub sce}. The material selected was Ni-22Cr-6Mo alloy. The electrochemical kinetics at the pH values of interest have been recently characterized via potentiodynamic polarization. Figure 1 shows the polarization curves for Ni-22Cr-6Mo samples tested at room temperature in various HCl solutions. These data were used in all calculations. That is as the pH changed, a new polarization curve was applied to the position in the crevice. E, pH was calculated at each position and from this data, current at each position was determined. The effects of the crevice gap and

  17. Cryo-quenched Fe-Ni-Cr alloy single crystals: A new decorative steel

    SciTech Connect

    Boatner, Lynn A.; Kolopus, James A.; Lavrik, Nicolay V.; Phani, P. Sudharshan

    2016-08-31

    In this paper, a decorative steel is described that is formed by a process that is unlike that of the fabrication methods utilized in making the original Damascus steels over 2000 years ago. The decorative aspect of the steel arises from a three-dimensional surface pattern that results from cryogenically quenching polished austenitic alloy single crystals into the martensitic phase that is present below 190 K. No forging operations are involved – the mechanism is entirely based on the metallurgical phase properties of the ternary alloy. The symmetry of the decorative pattern is determined and controlled by the crystallographic orientation and symmetry of the 70%Fe,15%Ni,15%Cr alloy single crystals. Finally, in addition to using “cuts” made along principal crystallographic surface directions, an effectively infinite number of other random-orientation “cuts” can be utilized to produce decorative patterns where each pattern is unique after the austenitic-to-martensitic phase transformation.

  18. Cryo-quenched Fe-Ni-Cr alloy single crystals: A new decorative steel

    SciTech Connect

    Boatner, Lynn A.; Kolopus, James A.; Lavrik, Nicolay V.; Phani, P. Sudharshan

    2016-08-31

    In this paper, a decorative steel is described that is formed by a process that is unlike that of the fabrication methods utilized in making the original Damascus steels over 2000 years ago. The decorative aspect of the steel arises from a three-dimensional surface pattern that results from cryogenically quenching polished austenitic alloy single crystals into the martensitic phase that is present below 190 K. No forging operations are involved – the mechanism is entirely based on the metallurgical phase properties of the ternary alloy. The symmetry of the decorative pattern is determined and controlled by the crystallographic orientation and symmetry of the 70%Fe,15%Ni,15%Cr alloy single crystals. Finally, in addition to using “cuts” made along principal crystallographic surface directions, an effectively infinite number of other random-orientation “cuts” can be utilized to produce decorative patterns where each pattern is unique after the austenitic-to-martensitic phase transformation.

  19. 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.

  20. Theoretical study of the Pb adsorption on Ni, Cr, Fe surfaces and on Ni based alloys

    NASA Astrophysics Data System (ADS)

    Bonnet, Marie-Laure; Costa, Dominique; Protopopoff, Elie; Marcus, Philippe

    2017-12-01

    Adsorption of Pb atoms on the Ni(111), Ni(100), Fe(110), and Cr(110) metallic surfaces was studied theoretically within an ab initio density functional theory approach (DFT). (√3 × √3)R30° super structures for Ni(111), and (2 × 2) for the other surfaces, corresponding to the saturation state, were considered. The preferred adsorption sites are found to be ternary sites for Ni(111), Fe(110), Cr(110) and quaternary sites for Ni(100). Adsorption on Fe and Cr is less exothermic than on Ni, by 0.16 and 0.33 eV/mol respectively. Adsorption on model surfaces of Ni based alloys was also investigated. It was found that the energy of adsorption depends mostly on the chemical composition of the ternary site, and can be described by a linear combination of the energies of adsorption on the pure metals. The nature of the second nearest neighbour of the adsorbed Pb atom has no significant influence on the adsorption energy. Average energies of adsorption were calculated in two cases: the limit of low coverage, and the saturation. The energies of adsorption of Pb at saturation on nickel base alloy surface representative of alloy 600 (Ni-15Cr-8Fe) and alloy 690 (Ni-30Cr-8Fe) were calculated to be 0.07 and 0.11 eV lower than on pure Ni respectively.

  1. 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.

  2. 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.

  3. 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.

  4. Cryo-quenched Fe-Ni-Cr alloy single crystals: A new decorative steel

    DOE PAGES

    Boatner, Lynn A.; Kolopus, James A.; Lavrik, Nicolay V.; ...

    2016-08-31

    In this paper, a decorative steel is described that is formed by a process that is unlike that of the fabrication methods utilized in making the original Damascus steels over 2000 years ago. The decorative aspect of the steel arises from a three-dimensional surface pattern that results from cryogenically quenching polished austenitic alloy single crystals into the martensitic phase that is present below 190 K. No forging operations are involved – the mechanism is entirely based on the metallurgical phase properties of the ternary alloy. The symmetry of the decorative pattern is determined and controlled by the crystallographic orientation andmore » symmetry of the 70%Fe,15%Ni,15%Cr alloy single crystals. Finally, in addition to using “cuts” made along principal crystallographic surface directions, an effectively infinite number of other random-orientation “cuts” can be utilized to produce decorative patterns where each pattern is unique after the austenitic-to-martensitic phase transformation.« less

  5. Stabilization of nickel-laden sludge by a high-temperature NiCr2O4 synthesis process.

    PubMed

    Li, Nien-Hsun; Chen, Yen-Hsin; Hu, Ching-Yao; Hsieh, Ching-Hong; Lo, Shang-Lien

    2011-12-30

    The feasibility of stabilizing nickel-laden sludge by a high-temperature NiCr(2)O(4) synthesis process was investigated with different sintering temperatures, salt contents, molar ratios, and reaction atmospheres. The crystalline phases of species were investigated by using an X-ray diffraction, and the surface characteristics of particles were observed by scanning electron microscopy. The leaching behavior of the stabilized sludge was evaluated by Toxicity Characteristic Leaching Procedure (TCLP) test. The results indicated that NiCr(2)O(4) was formed at around 800°C by transforming NiO and Cr(2)O(3) into a spinel structure. Leaching concentrations of both nickel and chromium decreased with an increase in the sintering temperature. The existence of salt in the sludge disturbed the formation of spinel, but a moderate salt content contributed to stabilization efficiency. A Cr/Ni molar ratio >2 also contributed to the stabilization efficiency of heavy metals after the thermal process. NiCr(2)O(4) was transformed from simulated sludge under both an N(2) and air atmosphere. The sintering strategy designed for nickel-laden sludge was proven to be beneficial in stabilizing nickel and chromium.

  6. Flexural strength of pure Ti, Ni-Cr and Co-Cr alloys submitted to Nd:YAG laser or TIG welding.

    PubMed

    Rocha, Rick; Pinheiro, Antônio Luiz Barbosa; Villaverde, Antonio Balbin

    2006-01-01

    Welding of metals and alloys is important to Dentistry for fabrication of dental prostheses. Several methods of soldering metals and alloys are currently used. The purpose of this study was to assess, using the flexural strength testing, the efficacy of two processes Nd:YAG laser and TIG (tungsten inert gas) for welding of pure Ti, Co-Cr and Ni-Cr alloys. Sixty cylindrical specimens were prepared (20 of each material), bisected and welded using different techniques. Four groups were formed (n=15). I: Nd:YAG laser welding; II- Nd:YAG laser welding using a filling material; III- TIG welding and IV (control): no welding (intact specimens). The specimens were tested in flexural strength and the results were analyzed statistically by one-way ANOVA. There was significant differences (p<0.001) among the non-welded materials, the Co-Cr alloy being the most resistant to deflection. Comparing the welding processes, significant differences (p<0.001) where found between TIG and laser welding and also between laser alone and laser plus filling material. In conclusion, TIG welding yielded higher flexural strength means than Nd:YAG laser welding for the tested Ti, Co-Cr and Ni-Cr alloys.

  7. Integrated environmental degradation model for Fe-Ni-Cr alloys in irradiated aqueous solutions

    SciTech Connect

    Pleune, T.T.

    1999-09-01

    Environmentally assisted cracking (EAC) is the most problematic form of localized corrosion in irradiated areas of nuclear power plants. EAC is any phenomenon where a combination of environment, material, and tensile stress result in cracking, including stress corrosion cracking (SCC), and hydrogen embrittlement. For this project an integrated EAC model based on first-principles electrochemistry and physical metallurgy was developed. The effect of neutron and gamma radiation dose is included explicitly so that irradiation-assisted SCC can be studied. The primary dependent variable in the model is the environmentally assisted crack growth rate as a function of chemical and mechanical parameters. The model integrates bulk and local chemistry models with the mechanical and chemical (alloy) behavior of the metal to allow the study of EAC in general. The model evaluates the water chemistry including radiolysis and hydrogen water chemistry and metal properties including radiation-induced segregation, radiation hardening, and the crack tip strain rate of a growing crack. The model inputs include thermal-hydraulic data such as flow rate, temperature, power level, dose, pressure, and initial water chemistry throughout the reactor, as well as dimension, stress/strain conditions, and initial sensitization data for reactor components.

  8. Effect of Specimen Thickness on Microstructural Changes During Oxidation of the NiCrW Alloy 230 at 950–1050°C

    DOE PAGES

    Jalowicka, A.; Duan, R.; Huczkowski, P.; ...

    2015-09-25

    An accurate procedure for predicting oxidation-induced damage and lifetime limits is crucial for the reliable operation of high-temperature metallic components in practical applications. In order to develop a predictive oxidation lifetime model for Ni–Cr alloys, specimens of wrought NiCrW alloy 230 with different thicknesses were cyclically oxidized in air at 950–1050°C for up to 3000 h. After prolonged exposure, two types of carbides as well as a Cr-rich nitride (π-phase) precipitated in the γ-Ni matrix. In the case of oxidation-induced loss of Cr from the alloy resulted in the formation of subscale zones, which were free of the Cr-rich carbidemore » and nitride but also of the Ni-W rich M6C. The width of the M6C-free zone was smaller than that free of the Cr-rich precipitates. Thermodynamic and diffusion calculations of the observed time- and temperature-dependent Cr depletion processes identified that back diffusion of C occurred which resulted in an increased volume fraction of M23C6 in the specimen core. Moreover, with increasing time and temperature, the amount of π-phase in the specimen core increased. The subscale depletion of the initially present Cr-nitrides and the formation of Cr-nitrides in the specimen center is believed to be related to a mechanism which is qualitatively similar to that described for the Cr carbide enrichment. However, with increasing time and decreasing specimen thickness, N uptake from the atmosphere becomes apparent. As a result, the precipitates present in the specimen center eventually consisted almost exclusively of nitrides.« less

  9. Effect of Specimen Thickness on Microstructural Changes During Oxidation of the NiCrW Alloy 230 at 950–1050°C

    SciTech Connect

    Jalowicka, A.; Duan, R.; Huczkowski, P.; Chyrkin, A.; Grüner, D.; Pint, B. A.; Unocic, K. A.; Quadakkers, W. J.

    2015-09-25

    An accurate procedure for predicting oxidation-induced damage and lifetime limits is crucial for the reliable operation of high-temperature metallic components in practical applications. In order to develop a predictive oxidation lifetime model for Ni–Cr alloys, specimens of wrought NiCrW alloy 230 with different thicknesses were cyclically oxidized in air at 950–1050°C for up to 3000 h. After prolonged exposure, two types of carbides as well as a Cr-rich nitride (π-phase) precipitated in the γ-Ni matrix. In the case of oxidation-induced loss of Cr from the alloy resulted in the formation of subscale zones, which were free of the Cr-rich carbide and nitride but also of the Ni-W rich M6C. The width of the M6C-free zone was smaller than that free of the Cr-rich precipitates. Thermodynamic and diffusion calculations of the observed time- and temperature-dependent Cr depletion processes identified that back diffusion of C occurred which resulted in an increased volume fraction of M23C6 in the specimen core. Moreover, with increasing time and temperature, the amount of π-phase in the specimen core increased. The subscale depletion of the initially present Cr-nitrides and the formation of Cr-nitrides in the specimen center is believed to be related to a mechanism which is qualitatively similar to that described for the Cr carbide enrichment. However, with increasing time and decreasing specimen thickness, N uptake from the atmosphere becomes apparent. As a result, the precipitates present in the specimen center eventually consisted almost exclusively of nitrides.

  10. Modified section method for laser-welding of ill-fitting cp Ti and Ni-Cr alloy one-piece cast implant-supported frameworks.

    PubMed

    Tiossi, R; Falcão-Filho, H; Aguiar Júnior, F A; Rodrigues, R C; Mattos, M da G; Ribeiro, R F

    2010-05-01

    This study aimed to verify the effect of modified section method and laser-welding on the accuracy of fit of ill-fitting commercially pure titanium (cp Ti) and Ni-Cr alloy one-piece cast frameworks. Two sets of similar implant-supported frameworks were constructed. Both groups of six 3-unit implant-supported fixed partial dentures were cast as one-piece [I: Ni-Cr (control) and II: cp Ti] and evaluated for passive fitting in an optical microscope with both screws tightened and with only one screw tightened. All frameworks were then sectioned in the diagonal axis at the pontic region (III: Ni-Cr and IV: cp Ti). Sectioned frameworks were positioned in the matrix (10-Ncm torque) and laser-welded. Passive fitting was evaluated for the second time. Data were submitted to anova and Tukey-Kramer honestly significant difference tests (P < 0.05). With both screws tightened, one-piece cp Ti group II showed significantly higher misfit values (27.57 +/- 5.06 microm) than other groups (I: 11.19 +/- 2.54 microm, III: 12.88 +/- 2.93 microm, IV: 13.77 +/- 1.51 microm) (P < 0.05). In the single-screw-tightened test, with readings on the opposite side to the tightened side, Ni-Cr cast as one-piece (I: 58.66 +/- 14.30 microm) was significantly different from cp Ti group after diagonal section (IV: 27.51 +/- 8.28 microm) (P < 0.05). On the tightened side, no significant differences were found between groups (P > 0.05). Results showed that diagonally sectioning ill-fitting cp Ti frameworks lowers misfit levels of prosthetic implant-supported frameworks and also improves passivity levels of the same frameworks when compared to one-piece cast structures.

  11. Effects of Mn, Si, and purity on the design of 3.5NiCrMoV, 1CrMoV, and 2.25Cr-1Mo bainitic alloy steels

    NASA Astrophysics Data System (ADS)

    Bodnar, R. L.; Ohhashi, T.; Jaffee, R. I.

    1989-08-01

    Three high-temperature bainitic alloy steels were evaluated in the laboratory to determine the effects of Mn, Si, and impurities ( i.e., S, P, Sn, As, and Sb) on microstructure and mechanical properties. The alloy steels were 3.5NiCrMoV and CrMoV, which are used for turbine rotors, and 2.25Cr-1Mo, which is used in pressure vessel applications. The important effects of Mn, Si, and impurities, which should control the design of these high-temperature bainitic steels, are presented. Key results are used to illustrate the influence of these variables on cleanliness, overheating, austenitizing, hardenability, tempering, ductility, toughness, temper embrittlement, creep rupture, and low-cycle fatigue. Low levels of Mn, Si, and impurities not only result in improved temper embrittlement resistance in these steels but also lead to an improvement in creep rupture properties ( i.e., improved strength and ductility). These results have produced some general guidelines for the design of high-temperature bainitic steels. Examples illustrating the implementation of the results and the effectiveness of the design guidelines are provided. Largely based on the benefits shown by this work, a high-purity 3.5NiCrMoV steel, which is essentially free of Mn, Si, and impurities, has been developed and is already being used commercially.

  12. Adherent Al2O3 scales produced on undoped NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    1986-01-01

    Repeated oxidation and polishing of high purity Ni-15Cr-13Al has dramatically changed its cyclic oxidation behavior from nonadherent to adherent. No apparent change in scale phase, morphology or interface structure occurred during this transition, dismissing any mechanism based on pegging, vacancy sink, or growth stress. The principle change that did occur was a reduction in the sulfur content from 10 ppmw to 3 ppmw after 25 cycles at 1120 C. These observations are used to support the model of Al2O3 scale adherence put forth by Smeggil et al. which claims that Al2O3 scale spallation occurs due to sulfur segregation and bond deterioration at the oxide-metal interface.

  13. [Influence of SiO2 films on color reproduction of Ni-Cr alloy porcelain crowns].

    PubMed

    Wu, Dong; Feng, Yunzhi

    2011-08-01

    To study whether SiO2 films will influence the color of Ni-Cr metal ceramic restorations. For the film plating experimental group, Sol-gel method was employed to apply SiO2 films to the surface of the Ni-Cr copings, while no coating was applied for the non-film-plating control group. Veneering porcelains were then applied subsequently, and a total of 12 B2-colored maxillary incisor metal ceramic crowns were fabricated with 6 crowns in each group. A ShadeEye Ncc computer-aided colorimeter was employed to measure the shade of the samples, as well as 6 B2(Vitapan classical vita color tabs) shade standards. The color was expressed as C1E-1976-Lab coordinates. There was a statistically significant color difference between all metal ceramic crowns and the B2 shade standards (delta E>1.5). The L*, a*, b* values of all crowns were higher than those of the B2 shade standards, and the crowns were typically yellower or redder. While neither significant color difference nor difference in shade values was observed between the film plating experimental group and non-film-plating control group (delta E<1.5). SiO2 films applied to the Ni-Cr copings by means of Sol-gel technique do not impact the final color of the metal ceramic restorations.

  14. 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.

  15. Impact of Small Chemistry Variations in Plate and Weld Filler Metal on the Corrosion Performance of Ni-Cr-Mo Alloys

    SciTech Connect

    Fix, D V; Rebak, R B

    2006-02-05

    The ASTM standard B 575 provides the requirements for the chemical composition of Nickel-Chromium-Molybdenum (Ni-Cr-Mo) alloys such as Alloy 22 (N06022) and Alloy 686 (N06686). The compositions of each element are given in a range. For example, the content of Mo is specified from 12.5 to 14.5 weight percent for Alloy 22 and from 15.0 to 17.0 weight percent for Alloy 686. It was important to determine how the corrosion rate of welded plates of Alloy 22 using Alloy 686 weld filler metal would change if heats of these alloys were prepared using several variations in the composition of the elements even though still in the range specified in B 575. Seven heats of plate were welded with seven heats of wire. Immersion corrosion tests were conducted in a boiling solution of sulfuric acid plus ferric sulfate (ASTM G 28 A) using both as-welded (ASW) coupons and solution heat-treated (SHT) coupons. Results show that the corrosion rate was not affected by the chemistry of the materials in the range specified in the standard B 575.

  16. Effect of Small Variation in the Composition of Plates and Weld Filler Wires on the General Corrosion Rate of Ni-Cr-Mo Alloys

    SciTech Connect

    Fix, D V; Estill, J C; Rebak, R B

    2005-02-05

    The ASTM standard B 575 provides the requirements for the chemical composition of Nickel-Chromium-Molybdenum (Ni-Cr-Mo) alloys such as Alloy 22 (N06022) and Alloy 686 (N06686). The compositions of each element are given in a range. For example, the content of Mo is specified from 12.5 to 14.5 weight percent for Alloy 22 and from 15.0 to 17.0 weight percent for Alloy 686. It was important to determine how the corrosion rate of welded plates of Alloy 22 using Alloy 686 weld filler metal would change if heats of these alloys were prepared using several variations in the composition of the elements even though still in the range specified in B 575. All the material used in this report were especially prepared at Allegheny Ludlum Co. Seven heats of plate were welded with seven heats of wire. Immersion corrosion tests were conducted in a boiling solution of sulfuric acid plus ferric sulfate (ASTM G 28 A) using both as-welded (ASW) coupons and solution heat-treated (SHT) coupons. Results show that the corrosion rate was not affected by the chemistry of the materials within the range of the standards.

  17. 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.

  18. Relation of structure to mechanical properties of thin thoria dispersion strengthened nickel-chromium (TD-NiCr alloy sheet

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1975-01-01

    A study of the relation between structure and mechanical properties of thin TD-NiCr sheet indicated that the elevated temperature tensile, stress-rupture, and creep strength properties depend primarily on the grain aspect ratio and sheet thickness. In general, the strength properties increased with increasing grain aspect ratio and sheet thickness. Tensile testing revealed an absence of ductility at elevated temperatures. A threshold stress for creep appears to exist. Even small amounts of prior creep deformation at elevated temperatures can produce severe creep damage.

  19. Preparation of Functionally Graded Materials (FGMs) Using Coal Fly Ash and NiCr-Based Alloy Powder by Spark Plasma Sintering (SPS)

    SciTech Connect

    Kaneko, Gen-yo; Kitagawa, Hiroyuki; Hasezaki, Kazuhiro; Ito, Yuji; Kakuda, Hideaki

    2008-02-15

    Functionally Graded Materials (FGMs) were prepared by spark plasma sintering (SPS) using coal fly ash and NiCr alloy powder. The coal fly ash was produced by the Misumi Coal Thermal Power Station (Chugoku Electric Power Co., Inc.), with 80 wt% nickel and 20 wt% chromium (Fukuda Metal Foil and Powder Co., Ltd.) used as source materials. The sintering temperature in the graphite die was 1000 deg. C. X-ray diffraction patterns of the sintered coal fly ash materials indicated that mullite (3Al{sub 2}O{sub 3}{center_dot}2SiO{sub 2}) and silica (SiO{sub 2}) phases were predominant. Direct joining of coal fly ash and NiCr causes fracture at the interface. This is due to the mismatch in the thermal expansion coefficients (CTE). A crack in the FGM was observed between the two layers with a CTE difference of over 4.86x10{sup -6} K{sup -1}, while a crack in the FGM was difficult to detect when the CTE difference was less than 2.77x10{sup -6} K{sup -1}.

  20. Preparation of Functionally Graded Materials (FGMs) Using Coal Fly Ash and NiCr-Based Alloy Powder by Spark Plasma Sintering (SPS)

    NASA Astrophysics Data System (ADS)

    Kaneko, Gen-yo; Kitagawa, Hiroyuki; Hasezaki, Kazuhiro; Ito, Yuji; Kakuda, Hideaki

    2008-02-01

    Functionally Graded Materials (FGMs) were prepared by spark plasma sintering (SPS) using coal fly ash and NiCr alloy powder. The coal fly ash was produced by the Misumi Coal Thermal Power Station (Chugoku Electric Power Co., Inc.), with 80 wt% nickel and 20 wt% chromium (Fukuda Metal Foil & Powder Co., Ltd.) used as source materials. The sintering temperature in the graphite die was 1000 °C. X-ray diffraction patterns of the sintered coal fly ash materials indicated that mullite (3Al2O3ṡ2SiO2) and silica (SiO2) phases were predominant. Direct joining of coal fly ash and NiCr causes fracture at the interface. This is due to the mismatch in the thermal expansion coefficients (CTE). A crack in the FGM was observed between the two layers with a CTE difference of over 4.86×10-6 K-1, while a crack in the FGM was difficult to detect when the CTE difference was less than 2.77×10-6 K-1.

  1. Microstructure and wear behaviors of laser clad NiCr/Cr3C2-WS2 high temperature self-lubricating wear-resistant composite coating

    NASA Astrophysics Data System (ADS)

    Yang, Mao-Sheng; Liu, Xiu-Bo; Fan, Ji-Wei; He, Xiang-Ming; Shi, Shi-Hong; Fu, Ge-Yan; Wang, Ming-Di; Chen, Shu-Fa

    2012-02-01

    The high temperature self-lubricating wear-resistant NiCr/Cr3C2-30%WS2 coating and wear-resistant NiCr/Cr3C2 coating were fabricated on 0Cr18Ni9 austenitic stainless steel by laser cladding. Phase constitutions and microstructures were investigated, and the tribological properties were evaluated using a ball-on-disc wear tester under dry sliding condition at room-temperature (17 °C), 300 °C and 600 °C, respectively. Results indicated that the laser clad NiCr/Cr3C2 coating consisted of Cr7C3 primary phase and γ-(Fe,Ni)/Cr7C3 eutectic colony, while the coating added with WS2 was mainly composed of Cr7C3 and (Cr,W)C carbides, with the lubricating WS2 and CrS sulfides as the minor phases. The wear tests showed that the friction coefficients of two coatings both decrease with the increasing temperature, while the both wear rates increase. The friction coefficient of laser clad NiCr/Cr3C2-30%WS2 is lower than the coating without WS2 whatever at room-temperature, 300 °C, 600 °C, but its wear rate is only lower at 300 °C. It is considered that the laser clad NiCr/Cr3C2-30%WS2 composite coating has good combination of anti-wear and friction-reducing capabilities at room-temperature up to 300 °C.

  2. Brazing ZrO{sub 2} ceramic to Ti–6Al–4V alloy using NiCrSiB amorphous filler foil: Interfacial microstructure and joint properties

    SciTech Connect

    Cao, J.; Song, X.G.; Li, C.; Zhao, L.Y.; Feng, J.C.

    2013-07-15

    Reliable brazing of ZrO{sub 2} ceramic and Ti–6Al–4V alloy was achieved using NiCrSiB amorphous filler foil. The interfacial microstructure of ZrO{sub 2}/Ti–6Al–4V joints was characterized by scanning electron microscope, energy dispersive spectrometer and micro-focused X-ray diffractometer. The effects of brazing temperature on the interfacial microstructure and joining properties of brazed joints were investigated in detail. Active Ti of Ti–6Al–4V alloy dissolved into molten filler metal and reacted with ZrO{sub 2} ceramic to form a continuous TiO reaction layer, which played an important role in brazing. Various reaction phases including Ti{sub 2}Ni, Ti{sub 5}Si{sub 3} and β-Ti were formed in brazed joints. With an increasing of brazing temperature, the TiO layer thickened gradually while the Ti{sub 2}Ni amount reduced. Shear test indicated that brazed joints tend to fracture at the interface between ZrO{sub 2} ceramic and brazing seam or Ti{sub 2}Ni intermetallic layer. The maximum average shear strength reached 284.6 MPa when brazed at 1025 °C for 10 min. - Graphical Abstract: Interfacial microstructure of ZrO{sub 2}/TC4 joint brazed using NiCrSiB amorphous filler foil was: ZrO{sub 2}/TiO/Ti{sub 2}Ni + β-Ti + Ti{sub 5}Si{sub 3}/β-Ti/Widmanstätten structure/TC4. - Highlights: • Brazing of ZrO{sub 2} ceramic and Ti-6Al-4V alloy was achieved. • Interfacial microstructure was TiO/Ti{sub 2}Ni + β + Ti{sub 5}Si{sub 3}/β/Widmanstätten structure. • The formation of TiO produced the darkening effect of ZrO{sub 2} ceramic. • The highest joining strength of 284.6MPa was obtained.

  3. The bond strength of porcelain to Ni-Cr alloy--the influence of tin or chromium plating.

    PubMed

    Inoue, K; Murakami, T; Terada, Y

    1992-01-01

    Nickel-chromium alloys were plated with tin and chromium to evaluate the effect on porcelain shear bond strength. Six plating methods were used. Additionally, the microstructure of the bond between the plated alloy and porcelain were studied using SEM and EPMA. Tin plating increased the bond strength of porcelain to a nickel-chromium alloy while chromium plating did not.

  4. 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.

  5. High-Temperature Oxidation and Smelt Deposit Corrosion of Ni-Cr-Ti Arc-Sprayed Coatings

    NASA Astrophysics Data System (ADS)

    Matthews, S.; Schweizer, M.

    2013-08-01

    High Cr content Ni-Cr-Ti arc-sprayed coatings have been extensively applied to mitigate corrosion in black liquor recovery boilers in the pulp and paper industry. In a previous article, the effects of key spray parameters on the coating's microstructure and its composition were investigated. Three coating microstructures were selected from that previous study to produce a dense, oxidized coating (coating A), a porous, low oxide content coating (coating B), and an optimized coating (coating C) for corrosion testing. Isothermal oxidation trials were performed in air at 550 and 900 °C for 30 days. Additional trials were performed under industrial smelt deposits at 400 and 800 °C for 30 days. The effect of the variation in coating microstructure on the oxidation and smelt's corrosion response was investigated through the characterization of the surface corrosion products, and the internal coating microstructural developments with time at high temperature. The effect of long-term, high-temperature exposure on the interaction between the coating and substrate was characterized, and the mechanism of interdiffusion was discussed.

  6. Thermally activated low temperature creep and primary water stress corrosion cracking of NiCrFe alloys

    SciTech Connect

    Hall, M.M. Jr.

    1993-10-01

    A phenomenological SCC-CGR model is developed based on an apriori assumption that the SCC-CGR is controlled by low temperature creep (LTC). This mode of low temperature time dependent deformation occurs at stress levels above the athermal flow stress by a dislocation glide mechanism that is thermally activated and may be environmentally assisted. The SCC-CGR model equations developed contain thermal activation parameters descriptive of the dislocation creep mechanism. Thermal activation parameters are obtained by fitting the CGR model to SCC-CGR data obtained on Alloy 600 and Alloy X-750. These SCC-CGR activation parameters are compared to LTC activation parameters obtained from stress relaxation tests. When the high concentration of hydrogen at the tip of an SCC crack is considered, the SCC-CGR activation energies and rate sensitivities are shown to be quantitatively consistent with hydrogen reducing the activation energy and increasing the strain rate sensitivity in LTC stress relaxation tests. Stress dependence of SCC-CGR activation energy consistent with that found for the LTC activation energy. Comparisons between temperature dependence of the SCC-CGR stress sensitivity and LTC stress sensitivity provide a basis for speculation on effects of hydrogen and solute carbon on SCC crack growth rates.

  7. Residual stress and crack initiation in laser clad composite layer with Co-based alloy and WC + NiCr

    NASA Astrophysics Data System (ADS)

    Lee, Changmin; Park, Hyungkwon; Yoo, Jaehong; Lee, Changhee; Woo, WanChuck; Park, Sunhong

    2015-08-01

    Although laser cladding process has been widely used to improve the wear and corrosion resistance, there are unwanted cracking issues during and/or after laser cladding. This study investigates the tendency of Co-based WC + NiCr composite layers to cracking during the laser cladding process. Residual stress distributions of the specimen are measured using neutron diffraction and elucidate the correlation between the residual stress and the cracking in three types of cylindrical specimens; (i) no cladding substrate only, (ii) cladding with 100% stellite#6, and (iii) cladding with 55% stellite#6 and 45% technolase40s. The microstructure of the clad layer was composed of Co-based dendrite and brittle eutectic phases at the dendritic boundaries. And WC particles were distributed on the matrix forming intermediate composition region by partial melting of the surface of particles. The overlaid specimen exhibited tensile residual stress, which was accumulated through the beads due to contraction of the coating layer generated by rapid solidification, while the non-clad specimen showed compressive. Also, the specimen overlaid with 55 wt% stellite#6 and 45 wt% technolase40s showed a tensile stress higher than the specimen overlaid with 100% stellite#6 possibly, due to the difference between thermal expansion coefficients of the matrix and WC particles. Such tensile stresses can be potential driving force to provide an easy crack path ways for large brittle fractures combined with the crack initiation sites such as the fractured WC particles, pores and solidification cracks. WC particles directly caused clad cracks by particle fracture under the tensile stress. The pores and solidification cracks also affected as initiation sites and provided an easy crack path ways for large brittle fractures.

  8. Effect of retained austenite on high cycle fatigue behaviour of carburized 14NiCr11 steel

    NASA Astrophysics Data System (ADS)

    Jeddi, D.; Sidhom, H.; Lieurade, H.-P.

    2008-11-01

    Two vacuum carburizing treatments were applied to ductile steel 14NiCr11 to obtain equivalent hardened layers with retained austenite contents of 25% and 41%. The properties of the carburized surfaces were examined and characterized before fatigue tests and during cyclic loading. Transformation of retained austenite into martensite during loading, was evaluated by dispersive X-ray diffraction method. The effects of this transformation on the residual stresses have been measured by X ray diffraction in martensite and in retained austenite structures. It was shown that the cyclic retained austenite transformation caused a redistribution of the compressive residual stresses and an increased surface hardness that stabilized after a small number of cycles. The dependence of fatigue behaviour on surface properties was determined, and a relationship between the stabilized state and the fatigue limit is suggested. A phenomenological approach is proposed to correlate the influence of surface hardening and the stabilized residual stresses on fatigue limit of carburized specimens. The Crossland, Dang Van and Findley-Matake, multiaxial high cycle fatigue criteria were used in this approach and results have shown a good agreement with experimental data.

  9. Comparative characteristic and erosion behavior of NiCr coatings deposited by various high-velocity oxyfuel spray processes

    NASA Astrophysics Data System (ADS)

    Sidhu, Hazoor Singh; Sidhu, Buta Singh; Prakash, S.

    2006-12-01

    The purpose of this study is to analyze and compare the mechanical properties and microstructure details at the interface of high-velocity oxyfuel (HVOF)-sprayed NiCr-coated boiler tube steels, namely ASTM-SA-210 grade A1, ASTM-SA213-T-11, and ASTM-SA213-T-22. Coatings were developed by two different techniques, and in these techniques liquefied petroleum gas was used as the fuel gas. First, the coatings were characterized by metallographic, scanning electron microscopy/energy-dispersive x-ray analysis, x-ray diffraction, surface roughness, and microhardness, and then were subjected to erosion testing. An attempt has been made to describe the transformations taking place during thermal spraying. It is concluded that the HVOF wire spraying process offers a technically viable and cost-effective alternative to HVOF powder spraying process for applications in an energy generation power plant with a point view of life enhancement and to minimize the tube failures because it gives a coating having better resistance to erosion.

  10. High temperature wear performance of HVOF-sprayed Cr3C2-WC-NiCoCrMo and Cr3C2-NiCr hardmetal coatings

    NASA Astrophysics Data System (ADS)

    Zhou, Wuxi; Zhou, Kesong; Li, Yuxi; Deng, Chunming; Zeng, Keli

    2017-09-01

    A novel Cr3C2-WC-NiCoCrMo and commercial Cr3C2-NiCr thermal spray-grade powders with particle size of -45 + 15 μm were prepared by an agglomeration and sintering process. Cr3C2-WC-NiCoCrMo and Cr3C2-NiCr coatings were deposited by high velocity oxygen fuel (HVOF) spraying. The fundamental properties of both coatings were evaluated and friction wear test against Al2O3 counterbodies of both coatings at high temperatures (450 °C, 550 °C, 650 °C) were carried out ball-on-disk high temperature tribometer. All specimens were characterized by optical microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) and 3D non-contact surface mapping profiler. The results have shown that the Cr3C2-WC-NiCoCrMo coating exhibited lower porosity, higher micro-hardness compared to the Cr3C2-NiCr coating. The Cr3C2-WC-NiCoCrMo coating also exhibited better wear resistance and higher friction coefficient compared to the Cr3C2-NiCr coating when sliding against the Al2O3 counterpart. Wear rates of both coatings increased with raising temperature. Both coatings experienced abrasive wear; hard phase particles (WC and Cr3C2) with different sizes, distributed in the matrix phase, will effectively improve the resistance against wear at high temperatures.

  11. Ab initio investigation of the surface properties of austenitic Fe-Ni-Cr alloys in aqueous environments

    NASA Astrophysics Data System (ADS)

    Rák, Zs.; Brenner, D. W.

    2017-04-01

    The surface energetics of two austenitic stainless steel alloys (Type 304 and 316) and three Ni-based alloys (Alloy 600, 690, and 800) are investigated using theoretical methods within the density functional theory. The relative stability of the low index surfaces display the same trend for all alloys; the most closely packed orientation and the most stable is the (111), followed by the (100) and the (110) surfaces. Calculations on the (111) surfaces using various surface chemical and magnetic configurations reveal that Ni has the tendency to segregate toward the surface and Cr has the tendency to segregate toward the bulk. The magnetic frustration present on the (111) surfaces plays an important role in the observed segregation tendencies of Ni and Cr. The stability of the (111) surfaces in contact with aqueous solution are evaluated as a function of temperature, pH, and concentration of aqueous species. The results indicate that the surface stability of the alloys decrease with temperature and pH, and increase slightly with concentration. Under conditions characteristic to an operating pressurized water reactor, the Ni-based alloy series appears to be of better quality than the stainless steel series with respect to corrosion resistance and release of aqueous species when in contact with aqueous solutions.

  12. High-Temperature Exposure Studies of HVOF-Sprayed Cr3C2-25(NiCr)/(WC-Co) Coating

    NASA Astrophysics Data System (ADS)

    Singh, Harpreet; Kaur, Manpreet; Prakash, Satya

    2016-08-01

    In this research, development of Cr3C2-25(NiCr) + 25%(WC-Co) composite coating was done and investigated. Cr3C2-25(NiCr) + 25%(WC-Co) composite powder [designated as HP2 powder] was prepared by mechanical mixing of [75Cr3C2-25(NiCr)] and [88WC-12Co] powders in the ratio of 75:25 by weight. The blended powders were used as feedstock to deposit composite coating on ASTM SA213-T22 substrate using High Velocity Oxy-Fuel (HVOF) spray process. High-temperature oxidation/corrosion behavior of the bare and coated boiler steels was investigated at 700 °C for 50 cycles in air, as well as, in Na2SO4-82%Fe2(SO4)3 molten salt environment in the laboratory. Erosion-corrosion behavior was investigated in the actual boiler environment at 700 ± 10 °C under cyclic conditions for 1500 h. The weight-change technique was used to establish the kinetics of oxidation/corrosion/erosion-corrosion. X-ray diffraction, field emission-scanning electron microscopy/energy-dispersive spectroscopy (FE-SEM/EDS), and EDS elemental mapping techniques were used to analyze the exposed samples. The uncoated boiler steel suffered from a catastrophic degradation in the form of intense spalling of the scale in all the environments. The oxidation/corrosion/erosion-corrosion resistance of the HVOF-sprayed HP2 coating was found to be better in comparison with standalone Cr3C2-25(NiCr) coating. A simultaneous formation of protective phases might have contributed the best properties to the coating.

  13. 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.

  14. Predicting oxidation-limited lifetime of thin-walled components of NiCrW alloy 230

    SciTech Connect

    Duan, R.; Jalowicka, Aleksandra; Unocic, Kinga A.; Pint, Bruce A.; Huczkowski, P.; Chyrkin, Anton; Gruner, D.; Pillai, R.; Quadakkers, Willem Joseph

    2016-10-18

    Using alloy 230 as an example, a generalized oxidation lifetime model for chromia-forming Ni-base wrought alloys is proposed, which captures the most important damaging oxidation effects relevant for component design: wall thickness loss, scale spallation, and the occurrence of breakaway oxidation. For deriving input parameters and for verification of the model approach, alloy 230 specimens with different thicknesses were exposed for different times at temperatures in the range 950–1050 °C in static air. The studies focused on thin specimens (0.2–0.5 mm) to obtain data for critical subscale depletion processes resulting in breakaway oxidation within reasonably achievable test times up to 3000 h. The oxidation kinetics and oxidation-induced subscale microstructural changes were determined by combining gravimetric data with results from scanning electron microscopy with energy dispersive X-ray spectroscopy. The modeling of the scale spallation and re-formation was based on the NASA cyclic oxidation spallation program, while a new model was developed to describe accelerated oxidation occurring after longer exposure times in the thinnest specimens. The calculated oxidation data were combined with the reservoir model equation, by means of which the relation between the consumption and the remaining concentration of Cr in the alloy was established as a function of temperature and specimen thickness. Based on this approach, a generalized lifetime diagram is proposed, in which wall thickness loss is plotted as a function of time, initial specimen thickness, and temperature. As a result, the time to reach a critical Cr level at the scale/alloy interface of 10 wt% is also indicated in the diagrams.

  15. Predicting oxidation-limited lifetime of thin-walled components of NiCrW alloy 230

    DOE PAGES

    Duan, R.; Jalowicka, Aleksandra; Unocic, Kinga A.; ...

    2016-10-18

    Using alloy 230 as an example, a generalized oxidation lifetime model for chromia-forming Ni-base wrought alloys is proposed, which captures the most important damaging oxidation effects relevant for component design: wall thickness loss, scale spallation, and the occurrence of breakaway oxidation. For deriving input parameters and for verification of the model approach, alloy 230 specimens with different thicknesses were exposed for different times at temperatures in the range 950–1050 °C in static air. The studies focused on thin specimens (0.2–0.5 mm) to obtain data for critical subscale depletion processes resulting in breakaway oxidation within reasonably achievable test times up tomore » 3000 h. The oxidation kinetics and oxidation-induced subscale microstructural changes were determined by combining gravimetric data with results from scanning electron microscopy with energy dispersive X-ray spectroscopy. The modeling of the scale spallation and re-formation was based on the NASA cyclic oxidation spallation program, while a new model was developed to describe accelerated oxidation occurring after longer exposure times in the thinnest specimens. The calculated oxidation data were combined with the reservoir model equation, by means of which the relation between the consumption and the remaining concentration of Cr in the alloy was established as a function of temperature and specimen thickness. Based on this approach, a generalized lifetime diagram is proposed, in which wall thickness loss is plotted as a function of time, initial specimen thickness, and temperature. As a result, the time to reach a critical Cr level at the scale/alloy interface of 10 wt% is also indicated in the diagrams.« less

  16. Coupled Multi-Electrode Investigation of Crevice Corrosion of 316 Stainless Steel and NiCrMo Alloy 625

    SciTech Connect

    F. Bocher; F.J. Presuel-Moreno; J.R. Scully

    2006-06-08

    Crevice corrosion is currently mostly studied using either one of two techniques depending on the information desired. The first method involves two multicrevice formers or washers fastened on both sides of a sample plate. This technique provides exposure information regarding the severity of crevice corrosion (depth, position, frequency of attack) but delivers little or no electrochemical information. The second method involves the potentiodynamic or potentiostatic study of an uncreviced sample in a model crevice solution or under a crevice former in aggressive solution where crevice corrosion may initiate and propagate and global current is recorded. However, crevice corrosion initiation and propagation behavior is highly dependent on exact position in the crevice over time. The distance from the crevice mouth will affect the solution composition, the pH, the ohmic potential drop and the true potential in the crevice. Coupled multi-electrode arrays (MEA) were used to study crevice corrosion in order to take in account spatial and temporal evolution of electrochemistry simultaneously. Scaling laws were used to rescale the crevice geometry while keeping the corrosion electrochemical properties equivalent to that of a natural crevice at a smaller length scale. one of the advantages was to be able to use commercial alloys available as wires electrode and, in the case of MEA, to spread the crevice corrosion over many individual electrodes so each one of them will have a near homogeneous electrochemical behavior. The initial step was to obtain anodic polarization curves for the relevant material in acid chloride solution which simulated the crevice electrolyte. using the software Crevicer{trademark}, the potential distribution inside the crevice as a function of the distance from the crevice mouth was determined for various crevice gaps and applied potentials, assuming constant chemistry throughout the crevice. The crevice corrosion initiation location x{sub crit} is

  17. 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.

  18. 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.

  19. Characterization of the scale on oxidized Fe-Ni-Cr alloys using grazing emission x-ray fluorescence.

    SciTech Connect

    Koshelev, I.; Paulikas, A. P.; Beno, M.; Jennings, G.; Linton, J.; Uran, S.; Veal, B. W.; Materials Science Division

    2001-09-01

    Grazing emission X-ray fluorescence (GEXRF, or refracted X-ray fluorescence-RXF) has been used to characterize the oxide scale (predominately chromia) which formed on an alloy of 55Fe-25Cr-20Ni (wt%) after oxidation for 4 h at 750{sup o}C in O{sub 2}. Angle dependent X-ray emission spectra I({theta}) were acquired for three elements, Cr, Fe and Ni. The measured data were fit by adjusting scale parameters in the calculated spectra such that I({theta}) data were simultaneously fit for all three elements. It is shown that the calculated spectra are sensitive to scale thickness, to the Cr depletion zone that develops in the substrate at the scale-metal interface, and to the concentration of Fe and Ni atoms dissolved in the scale. The very demanding requirements imposed by simultaneously fitting all three measured I({theta}) curves provide a satisfactory determination of these scale parameters. The GEXRF measurements showed that the scale was about 0.5 {mu}m thick, with an underlying Cr depletion zone extending about 4 {mu}m (midpoint) into the substrate. The average Cr concentration in this depletion zone was reduced from the preoxidized value of 25 to 22.2 wt%. The scale contained about 2. 4 at% of Fe and less than 0.5 at% Ni. These measurements demonstrate that GEXRF can, in a single nondestructive measurement, provide key information needed to characterize a thermally grown chromia scale.

  20. The Phase Competition and Stability of High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Liu, W. H.; Wu, Y.; He, J. Y.; Zhang, Y.; Liu, C. T.; Lu, Z. P.

    2014-10-01

    Phase competition and stability of several typical high-entropy alloys (HEAs) were studied, and the effects of alloying additions and processing conditions on phase formation in these alloys were discussed. Alloying with chemically incompatible elements having a large difference in either the atomic size or enthalpy of mixing with constituting components in HEAs, e.g., Cu and Al in the FeCoNiCr alloy system, inevitably induced phase separation and stimulated formation of duplex solid-solution phases and even intermetallic compounds. The solid-solution phase in the as-cast FeCoNiCrMn HEA is extremely stable due to the good chemical compatibility among constituent components, but in the FeCoNiCrAl and (FeCoNiCrAl)99Si1 HEAs with the incompatible elements Al and Si, pretreatment and annealing processes could induce phase transitions and the formation of new phases, indicating that the as-cast solid-solution phases were destabilized by quenched-in chemical segregation, resulting from additions of the dissimilar elements.

  1. Electron microscopy characterization of Ni-Cr-B-Si-C laser deposited coatings.

    PubMed

    Hemmati, I; Rao, J C; Ocelík, V; De Hosson, J Th M

    2013-02-01

    During laser deposition of Ni-Cr-B-Si-C alloys with high amounts of Cr and B, various microstructures and phases can be generated from the same chemical composition that results in heterogeneous properties in the clad layer. In this study, the microstructure and phase constitution of a high-alloy Ni-Cr-B-Si-C coating deposited by laser cladding were analyzed by a combination of several microscopy characterization techniques including scanning electron microscopy in secondary and backscatter imaging modes, energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The combination of EDS and EBSD allowed unequivocal identification of micron-sized precipitates as polycrystalline orthorhombic CrB, single crystal tetragonal Cr5B3, and single crystal hexagonal Cr7C3. In addition, TEM characterization showed various equilibrium and metastable Ni-B, Ni-Si, and Ni-Si-B eutectic products in the alloy matrix. The findings of this study can be used to explain the phase formation reactions and to tune the microstructure of Ni-Cr-B-Si-C coatings to obtain the desired properties.

  2. 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

    2016-08-01

    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.

  3. Effect of different alloyed layers on the high temperature oxidation behavior of newly developed Ti 2AlNb-based alloys

    NASA Astrophysics Data System (ADS)

    Wu, Hongyan; Zhang, Pingze; Zhao, Haofeng; Wang, Ling; Xie, Aigen

    2011-01-01

    The application of titanium aluminide orthorhombic alloys (O-phase alloys) as potential materials in aircraft and jet engines was limited by their poor oxidation resistance at high temperature. The Ti 2AlNb-based alloys were chromised (Cr), chromium-tungstened (Cr-W) and nickel-chromised (Ni-Cr) by the double glow plasma surface alloying process to improve their high temperature oxidation resistance. The discontinuous oxidative behavior of Cr, Cr-W and Ni-Cr alloyed layers on Ti 2AlNb-based alloy at 1093 K was explored in this study. After exposing at 1093 K, the TiO 2 layer was formed on the bare alloy and accompanied by the occurrence of crack, which promoted oxidation rate. The oxidation behavior of Ti 2AlNb-based alloys was improved by surface alloying due to the formation of protective Al 2O 3 scale or continuous and dense NiCr 2O 4 film. The Ni-Cr alloyed layer presented the best high-temperature oxidation resistance among three alloyed layers.

  4. Characterization of the mechanical and physical properties of TD-NiCr (Ni-20Cr-2ThO2) alloy sheet

    NASA Technical Reports Server (NTRS)

    Fritz, L. J.; Koster, W. P.; Taylor, R. E.

    1973-01-01

    Sheets of TD-NiCr processed using techniques developed to produce uniform material were tested to supply mechanical and physical property data. Two heats each of 0.025 and 0.051 cm thick sheet were tested. Mechanical properties evaluated included tensile, modulus of elasticity, Poisson's Ratio, compression, creep-rupture, creep strength, bearing strength, shear strength, sharp notch and fatigue strength. Test temperatures covered the range from ambient to 1589K. Physical properties were also studied as a function of temperature. The physical properties measured were thermal conductivity, linear thermal expansion, specific heat, total hemispherical emittance, thermal diffusivity, and electrical conductivity.

  5. Creation of ternary Ni-Cr-W alloys with a sharp cube texture and a curie temperature below 77 K to produce epitaxial substrates for superconducting compositions

    NASA Astrophysics Data System (ADS)

    Rodionov, D. P.; Gervas'eva, I. V.; Khlebnikova, Yu. V.; Kazantsev, V. A.; Sazonova, V. A.

    2009-02-01

    The texture, structure, and magnetic and mechanical properties of thin tape substrates fabricated of nickel alloys with chromium and tungsten have been investigated. It has been shown that in Ni89.6Cr8.6W1.8 and Ni89.6Cr7.8W2.6 alloys a sharp cube texture can be formed, which is stable up to high annealing temperatures. In the Ni89.2Cr7.2W3.6 alloy, other orientations are present along with a cube component. The possibility of obtaining a sharp cube texture after primary recrystallization is connected with the quantitative relationship between the texture components in a cold-rolled tape, which is determined by the method of orientation-distribution functions. The alloys studied are paramagnetic at 77 K.

  6. 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.

  7. Copper modified austenitic stainless steel alloys with improved high temperature creep resistance

    DOEpatents

    Swindeman, R.W.; Maziasz, P.J.

    1987-04-28

    An improved austenitic stainless steel that incorporates copper into a base Fe-Ni-Cr alloy having minor alloying substituents of Mo, Mn, Si, T, Nb, V, C, N, P, B which exhibits significant improvement in high temperature creep resistance over previous steels. 3 figs.

  8. Measurement of the Nickel/Nickel Oxide Transition in Ni-Cr-Fe Alloys and Updated Data and Correlations to Quantify the Effect of Aqueous Hydrogen on Primary Water SCC

    SciTech Connect

    Steven A. Attanasio; David S. Morton

    2003-06-16

    Alloys 600 and X-750 have been shown to exhibit a maximum in primary water stress corrosion cracking (PWSCC) susceptibility, when testing is conducted over a range of aqueous hydrogen (H{sub 2}) levels. Contact electric resistance (CER) and corrosion coupon testing using nickel specimens has shown that the maximum in SCC susceptibility occurs in proximity to the nickel-nickel oxide (Ni/NiO) phase transition. The measured location of the Ni/NiO transition has been shown to vary with temperature, from 25 scc/kg H{sub 2} at 360 C to 4 scc/kg H{sub 2} at 288 C. New CER measurements show that the Ni/NiO transition is located at 2 scc/kg H{sub 2} at 260 C. An updated correlation of the phase transition is provided. The present work also reports CER testing conducted using an Alloy 600 specimen at 316 C. A large change in resistance occurred between 5 and 10 scc/kg H{sub 2}, similar to the results obtained at 316 C using a nickel specimen. This result adds confidence in applying the Ni/NiO transition measurements to Ni-Cr-Fe alloys. The understanding of the importance of the Ni/NiO transition to PWSCC has been used previously to quantify H{sub 2} effects on SCC growth rate (SCCGR). Specifically, the difference in the electrochemical potential (EcP) of the specimen or component from the Ni/NiO transition (i.e., EcP{sub Ni/NiO}-EcP) has been used as a correlating parameter. In the present work, these SCCGR-H{sub 2} correlations, which were based on SCCGR data obtained at relatively high test temperatures (338 and 360 C), are evaluated via SCCGR tests at a reduced temperature (316 C). The 316 C data are in good agreement with the predictions, implying that the SCCGR-H{sub 2} correlations extrapolate well to reduced temperatures. The SCCGR-H{sub 2} correlations have been revised to reflect the updated Ni/NiO phase transition correlation. New data are presented for EN82H weld metal (also known as Alloy 82) at 338 C. Similar to other nickel alloys, SCC of EN82H is a function of

  9. Preliminary Microstructural and Microscratch Results of Ni-Cr-Fe and Cr3C2-NiCr Coatings on Magnesium Substrate

    NASA Astrophysics Data System (ADS)

    Istrate, B.; Munteanu, C.; Lupescu, S.; Benchea, M.; Vizureanu, P.

    2017-06-01

    Thermal coatings have a large scale application in aerospace and automotive field, as barriers improving wear mechanical characteristics and corrosion resistance. In present research, there have been used two types of coatings, Ni-Cr-Fe, respectively Cr3C2-NiCr which were deposited on magnesium based alloys (pure magnesium and Mg-30Y master alloy). There have been investigated the microstructural aspects through scanning electronic microscopy and XRD analysis and also a series of mechanical characteristics through microscratch and indentation determinations. The results revealed the formation of some adherent layers resistant to the penetration of the metallic indenter, the coatings did not suffer major damages. Microstructural analysis highlighted the formation of Cr3C2, Cr7C3, Cr3Ni2, Cr7Ni3, FeNi3, Cr-Ni phases. Also, the apparent coefficient of friction for Ni-Cr-Fe coatings presents superior values than Cr3C2-NiCr coatings.

  10. The effect of post-treatment of a high-velocity oxy-fuel Ni-Cr-Mo-Si-B coating part 2: Erosion-corrosion behavior

    NASA Astrophysics Data System (ADS)

    Shrestha, S.; Hodgkiess, T.; Neville, A.

    2001-12-01

    In this paper, a study of the erosion-corrosion characteristics of a Ni-Cr-Mo-Si-B coating applied by the high-velocity oxy-fuel (HVOF) process on to an austenitic stainless steel (UNS S31603) substrate are reported. The coatings were studied in the as-sprayed condition, after vacuum sealing with polymer impregnation and after vacuum furnace fusion. The erosion-corrosion characteristics were assessed in an impinging liquid jet of 3.5% NaCl solution at 18 °C at a velocity of 17 m/s at normal incidence in two conditions: (1) free from added solids and (2) containing 800 ppm silica sand. The methodology employed electrochemical control and monitoring to facilitate the identification of the separate and interrelated erosion and corrosion contributions to the erosion-corrosion process. The rates of erosion-corrosion damage were drastically accelerated in the presence of the suspended solids. The application of cathodic protection significantly reduced the deterioration process. The study showed the effect of sealing with polymer impregnation did not significantly alter the erosion-corrosion behavior of the sprayed coating. However, there was a significant improvement in erosion-corrosion durability afforded by the postfusion process. The mechanisms by which the improved performance of vacuum-fused coatings is achieved are discussed.

  11. 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 SAP technique of dispersion strengthening (formation of an oxide dispersion by preoxidation of metal powders) was applied to atomized powder of the alloy Ni-17Cr-5Al-0.2 Y. SAP-NiCrAl was worked by extrusion and rod rolling at 1205 C and by swaging at 760 C. A variety of annealing treatments were applied after working to determine the recrystallization response. NiCrAlY, similarly prepared from atomized powder, but without a preoxidation treatment, was examined for comparison. The SAP-NiCrAl of this study 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 as has been reported for other oxide dispersion strengthened alloys. In contrast, unoxidized NiCrAlY exhibited only primary recrystallization.

  12. High Velocity Oxidation and Hot Corrosion Resistance of Some ODS Alloys

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    Several oxide dispersion strengthened (ODS) alloys were tested for cyclic, high velocity, oxidation, and hot corrosion resistance. These results were compared to the resistance of an advanced, NiCrAl coated superalloy. An ODS FeCrAl were identified as having sufficient oxidation and hot corrosion resistance to allow potential use in an aircraft gas turbine without coating.

  13. 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.

  14. Electroless deposition of NiCrB diffusion barrier layer film for ULSI-Cu metallization

    NASA Astrophysics Data System (ADS)

    Wang, Yuechun; Chen, Xiuhua; Ma, Wenhui; Shang, Yudong; Lei, Zhengtao; Xiang, Fuwei

    2017-02-01

    NiCrB films were deposited on Si substrates using electroless deposition as a diffusion barrier layer for Cu interconnections. Samples of the prepared NiCrB/SiO2/Si and NiCrB/Cu/NiCrB/SiO2/Si were annealed at temperatures ranging from 500 °C to 900 °C. The reaction mechanism of the electroless deposition of the NiCrB film, the failure temperature and the failure mechanism of the NiCrB diffusion barrier layer were investigated. The prepared samples were subjected to XRD, XPS, FPP and AFM to determine the phases, composition, sheet resistance and surface morphology of samples before and after annealing. The results of these analyses indicated that the failure temperature of the NiCrB barrier film was 900 °C and the failure mechanism led to crystallization and grain growth of the NiCrB barrier layer after high temperature annealing. It was found that this process caused Cu grains to reach Si substrate through the grain boundaries, and then the reaction between Cu and Si resulted in the formation of highly resistive Cu3Si.

  15. Effect of Anodic Polarization on Layer-Growth of Fe-Ni-Cr Anodes in Cryolite-Alumina Melts

    NASA Astrophysics Data System (ADS)

    Ndong, GermainKouma; Xue, Jilai; Feng, Luxing; Zhu, Jun

    High-temperature corrosion behaviors of Fe-Ni-Cr alloy as inert anodes for aluminum electrolysis have been studied. The effect of anodic overpotential on layer growth of anodic surface is specially considered. The corrosion layers on the anodes tested were analyzed using XRD and SEM-EDS to provide a fundamental understanding of the layers growth at metallic anode surface. The dissolution of the scale layers on the metal anode occurred with low overpotential, while AlxM3-xO4 spinel phase within the scale layers was found with an increased overpotential. A mixture of multiple MyO layers existed on the anode substrate. The results may be useful for understanding and controlling the corrosion behaviors of Fe-Ni-Cr anode for potential application in aluminum electrolysis.

  16. Effect of rare-earth element additions on microstructural properties and irradiation behavior of an Fe-Ni-Cr alloy from LMFBR and fusion reactor applications

    SciTech Connect

    Park, J.Y.

    1983-01-01

    This study consists of a survey of the effect of yttrium, lanthanum, and cerium rare-earth additions on the microstructure and radiation swelling behavior of an Fe-25.6Ni-8.7Cr-3.3Ti-1.6Al alloy. The undoped alloy was investigated in the as-received, annealed, and arc-melted conditions, and twelve arc melted and rare-earth doped alloys were prepared (doping levels of 0.05, 0.1, 0.5, and 1.0 wt % for each of the three rare earths). The ion bombardments were carried out at 570 and 600C with 4 MeV Ni or Fe ions to nominal 100 dpa and to 100 and 550 appm He. Lattice parameter, hardness, swelling, and optical and transmission electron microscopy observations were conducted.

  17. Effect of rare-earth element additions on microstructural properties and irradiation behavior of an Fe-Ni-Cr alloy for LMFBR and fusion reactor applications

    SciTech Connect

    Park, J.Y.

    1983-09-01

    This study consists of a survey of the effect of yttrium, lanthanum, and cerium rare-earth additions on the microstructure and radiation swelling behavior of an Fe-25.6Ni-8.7Cr-3.3Ti-1.6Al alloy. The undoped alloy was investigated in the as-received, annealed, and arc-melted conditions, and twelve arc melted and rare-earth doped alloys were prepared (doping levels of 0.05, 0.1, 0.5, and 1.0 wt % for each of the three rare earths). The ion bombardments were carried out at 570 and 600/sup 0/C with 4 MeV Ni or Fe ions to nominal 100 dpa and to 100 and 550 appm He. Lattice parameter, hardness, swelling, and optical and transmission electron microscopy observations were conducted.

  18. Ordering Transformation and Age Hardening in a Ni-Cr-W Superalloy

    NASA Astrophysics Data System (ADS)

    Gao, Xiangyu; Hu, Rui; Li, Xiaolin; Luo, Gongliao; Li, Jinshan; Fu, Hengzhi

    2016-12-01

    The microstructural changes occurring in a Ni-Cr-W superalloy during prolonged exposure to proper temperature have been investigated using transmission electron microscopy. It is demonstrated that nanometer-sized C11b (Pt2Mo-type) and DO22 superlattices can precipitate in the Ni-Cr-W alloy by means of a simple aging treatment at temperatures varying in the range of 773 K to 973 K (500 °C to 700 °C). The mechanism of transformation to long-range order has been revealed to accord with continuous mode based on transmission electron microscopy results and variation trend in Vickers microhardness. No signs of overaging and coarsening of C11b and DO22 phases with further aging have been found, which indicates that both of them have a high-thermal stability. The orientation relationships and interfaces between C11b/DO22 precipitates and Ni-based matrix have been investigated by high-resolution transmission electron microscopy, and the results reveal that the interfaces between C11b/DO22 precipitates and surrounding matrix are coherent at the atomic scale. Because of the high-density nanometer-sized C11b/DO22 precipitates, the microhardness of the alloy is improved remarkably.

  19. The oxidation performance of modern high-temperature alloys

    NASA Astrophysics Data System (ADS)

    Deodeshmukh, V. P.; Srivastava, S. K.

    2009-07-01

    The high-temperature oxidation resistance of an alloy is a key design criterion for components in a variety of industrial applications, such as advanced gas turbines, industrial heating, automotive, waste incineration, power generation and energy conversion, chemical and petrochemical processing, and metals and minerals processing. The importance of correctly assessing the long-term oxidation behavior of high-temperature alloys is illustrated. As applications move to higher temperatures, new alloys are needed. In this paper, the oxidation performance of three newly developed alloys, an alumina-forming Ni-Fe-Cr-Al alloy, a γ'-strengthened Ni-Cr-Co-Mo-(Al+Ti) alloy, and a nitride-strengthened Co-Cr-Fe-Ni-(Ti+Nb) alloy is presented.

  20. 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.

  1. Single crystal plastic behavior of a single-phase, face-center-cubic-structured, equiatomic FeNiCrCo alloy

    DOE PAGES

    Wu, Zhenggang; Gao, Y. F.; Bei, Hongbin

    2015-07-25

    To understand the fundamental deformation mechanisms of compositionally complex alloys, single crystals of a multi-component equiatomic FeNiCoCr alloy with face-centered cubic (FCC) structure were grown for mechanical studies. Similarly to typical FCC pure metals, slip trace analyses indicate that dislocation slips take place on (1 1 1) planes along [11¯0] directions. The critical resolved shear stress (CRSS) obeys the Schmid law at both 77 and 293 K, and tension–compression asymmetry is not observed. Although this material slips in a normal FCC manner both at 293 and 77 K, compared to typical FCC metals the CRSS’s strong temperature dependence is abnormal.

  2. Development of dispersion strengthened nickel-chromium alloy (Ni-Cr-ThO2) sheet for space shuttle vehicles, part 2

    NASA Technical Reports Server (NTRS)

    Klingler, L. J.; Weinberger, W. R.; Bailey, P. G.; Baranow, S.

    1972-01-01

    Two dispersion strengthened nickel base alloy systems were developed for use at temperatures up to 1204 C(2200 F); TD nickel chromium (TDNiCr) and TD nickel chromium aluminum (TDNiCrA1). They are considered candidate materials for use on the thermal protection systems of the space shuttle and for long term use in aircraft gas turbine engine applications. Improved manufacturing processes were developed for the fabrication of TDNiCr sheet and foil to specifications. Sheet rolling process studies and extrusion studies were made on two aluminum containing alloys: Ni-16%Cr-3.5%A1-2%ThO2 and Ni-16%Cr-5.0%A12%ThO2. Over 1600 kg.(3500 lb.) of plate, sheet, foil, bar and extrusion products were supplied to NASA Centers for technology studies.

  3. Single crystal plastic behavior of a single-phase, face-center-cubic-structured, equiatomic FeNiCrCo alloy

    SciTech Connect

    Wu, Zhenggang; Gao, Y. F.; Bei, Hongbin

    2015-07-25

    To understand the fundamental deformation mechanisms of compositionally complex alloys, single crystals of a multi-component equiatomic FeNiCoCr alloy with face-centered cubic (FCC) structure were grown for mechanical studies. Similarly to typical FCC pure metals, slip trace analyses indicate that dislocation slips take place on (1 1 1) planes along [11¯0] directions. The critical resolved shear stress (CRSS) obeys the Schmid law at both 77 and 293 K, and tension–compression asymmetry is not observed. Although this material slips in a normal FCC manner both at 293 and 77 K, compared to typical FCC metals the CRSS’s strong temperature dependence is abnormal.

  4. Development of dispersion strengthened nickel-chromium alloy (Ni-Cr-Th-O2) sheet for space shuttle vehicles, part 1

    NASA Technical Reports Server (NTRS)

    Klingler, L. J.; Weinberger, W. R.; Bailey, P. G.; Baranow, S.

    1971-01-01

    A dispersion-strengthened alloy, TD nickel chromium (TDNiCr) is being developed for use on the thermal protection system of the space shuttle at temperatures up to 1204 C(2200 F). Manufacturing processes were developed for the fabrication of sheet and foil to specifications. The addition of aluminum to the basic TDNiCr composition provides outstanding oxidation resistance up to 1260 C(2300 F); aluminum levels of 2 to 4% are considered optimum for space shuttle application.

  5. Investigation of the oxidation behavior of dispersion stabilized alloys when exposed to a dynamic high temperature environment

    NASA Technical Reports Server (NTRS)

    Tenney, D. R.

    1974-01-01

    The oxidation behavior of TD-NiCr and TD-NiCrAlY alloys have been studied at 2000 and 2200 F in static and high speed flowing air environments. The TD-NiCrAlY alloys preoxidized to produce an Al2O3 scale on the surface showed good oxidation resistance in both types of environments. The TD-NiCr alloy which had a Cr2O3 oxide scale after preoxidation was found to oxidize more than an order of magnitude faster under the dynamic test conditions than at comparable static test conditions. Although Cr2O3 normally provides good oxidation protection, it was rapidly lost due to formation of volatile CrO3 when exposed to the high speed air stream. The preferred oxide arrangement for the dynamic test consisted of an external layer of NiO with a porous mushroom type morphology, an intermediate duplex layer of NiO and Cr2O3, and a continuous inner layer of Cr2O3 in contact with the alloy substrate. An oxidation model has been developed to explain the observed microstructure and overall oxidation behavior of all alloys.

  6. Selective oxidation of cube textured Ni and Ni-Cr substrate for the formation of cube textured NiO as a component buffer layer for REBa 2Cu 3O 7+ x (REBCO) coated conductors

    NASA Astrophysics Data System (ADS)

    Lockman, Z.; Goldacker, W.; Nast, R.; deBoer, B.; MacManus-Driscoll, J. L.

    2002-08-01

    Thermal oxidation of cube textured, pure Ni and Ni-Cr tapes was undertaken under different oxidation conditions to form cube textured NiO for the use as a first component of buffer layer for the coated conductor. Cube textured NiO was formed on pure Ni after oxidising for more than 130 min in O 2 at 1250 °C. The oxide thickness was >30 μm. Much shorter oxidation times (20-40 min, NiO thickness of ∼5 μm) and lower temperature (1050 °C) were required to form a similar texture on Ni-Cr foils. In addition, NiO formed on Ni-13%Cr was more highly textured than Ni-10%Cr. A Cr 2O 3 inner layer and NiO outer layer was formed on the Ni-Cr alloys.

  7. Influence of Laser Cladding Parameters on the Distribution of Elements in the Beads of Nickel-Based Ni-Cr-B-Si Alloy

    NASA Astrophysics Data System (ADS)

    Devoyno, O. G.; Drozdov, P. S.; Dovoretskiy, Y. B.; Kardapolova, M. A.; Lutsko, N. I.; Tamanis, E.

    2012-01-01

    The authors explore the beads obtained by laser cladding with nickel-based self-fluxing alloy (grain size 20-80 μm) at different laser beam travel rates against the sample and different cladding distances. They examined the iron, nickel, chrome and silicon content of the coating in dependence on the cladding rate and the microstructure in each zone of a bead. As a result, it was established that the beads after laser cladding have a similar structure morphology in all the examined zones, which confirms that there is intense mixing of the molten-metal pool. A distinct correlation has been found between the distribution of coating elements and the modes of laser cladding: the nickel, chrome, and silicon contents of the coating are decreasing while the iron content is increasing with increased cladding rate. The authors point out a strong effect of radiation shielding caused by the vapours generated during the process of melting the powder particles in the area exposed to laser radiation.

  8. Accurate classical short-range forces for the study of collision cascades in Fe-Ni-Cr

    NASA Astrophysics Data System (ADS)

    Béland, Laurent Karim; Tamm, Artur; Mu, Sai; Samolyuk, German D.; Osetsky, Yuri N.; Aabloo, Alvo; Klintenberg, Mattias; Caro, Alfredo; Stoller, Roger E.

    2017-10-01

    The predictive power of a classical molecular dynamics simulation is largely determined by the physical validity of its underlying empirical potential. In the case of high-energy collision cascades, it was recently shown that correctly modeling interactions at short distances is necessary to accurately predict primary damage production. An ab initio based framework is introduced for modifying an existing embedded-atom method FeNiCr potential to handle these short-range interactions. Density functional theory is used to calculate the energetics of two atoms approaching each other, embedded in the alloy, and to calculate the equation of state of the alloy as it is compressed. The pairwise terms and the embedding terms of the potential are modified in accordance with the ab initio results. Using this reparametrized potential, collision cascades are performed in Ni50Fe50, Ni80Cr20 and Ni33Fe33Cr33. The simulations reveal that alloying Ni and NiCr to Fe reduces primary damage production, in agreement with some previous calculations. Alloying Ni and NiFe to Cr does not reduce primary damage production, in contradiction with previous calculations.

  9. 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.

  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. High-resolution diffraction for residual stress determination in the NiCrMoV wheel of an axial compressor for a heavy-duty gas turbine

    NASA Astrophysics Data System (ADS)

    Rogante, M.; Török, G.; Ceschini, G. F.; Tognarelli, L.; Füzesy, I.; Rosta, L.

    2004-07-01

    The wheel of an axial compressor for a heavy-duty gas turbine has been investigated for residual stresses (RS) evaluation of the teeth-section where SANS measurements have previously been performed. Such a component can contain internal RS, either due to the manufacturing process, or to the operating cycles fatigue. The constitutive material is a NiCrMoV steel to ASTM A 471 (type 2) norms (equivalent to B50A420B10); this material is usually adopted in the manufacturing of forged components for gas turbines. Internal radial and hoop RS have been determined, whose values are under the limit of 200kPa. Hoop RS, in general, resulted in higher value than the radial ones. The present experiment represents a particularly important step in the RS determination for gas turbine components, since the measurements reveal that the fatigue of the wheel is also a lifetime limiting factor although, in the same technological field, the available data in the actual neutron techniques literature mainly concern turbine buckets.

  12. Adjustment of temperature coefficient of resistance in NiCr/CuNi(Mn)/NiCr films

    NASA Astrophysics Data System (ADS)

    Brückner, W.; Baunack, St.; Elefant, D.; Reiss, G.

    1996-06-01

    The thin-film system Ni0.37Cr0.63/Cu0.57Ni0.42Mn0.01/Ni0.37Cr0. 63 with a typical thickness of 1 μm is used for low-ohmic precision resistors. The necessary adjustment of the temperature coefficient of resistance (TCR) by annealing has been studied by investigating the irreversible changes of the resistance during various annealing steps of NiCr/CuNi(Mn)/NiCr multilayers in comparison with single layers of CuNi(Mn) and NiCr. Auger depth profiles showed that the interdiffusion of CuNi(Mn) and NiCr results in an impoverishment of Ni in CuNi(Mn), explaining the TCR shift by comparison with data of Cu1-xNix bulk material. The decrease of the resistivity and the reduction of the width of the copper-nickel conductive layer by formation of a Ni0.6Cr0.2Cu0.2 interdiffusion zone phase (in accordance with the Cu-Ni-Cr phase diagram) cause a significant curvature of the resistance-temperature curve. As main result, it is shown that the NiCr base and cover layers and their interdiffusion with CuNi(Mn) play the decisive role in adjusting the TCR. It was checked that oxidation and topography effects have no remarkable influences.

  13. Investigation of Ni-Cr-Si-Fe-B coatings produced by the electron beam cladding technique

    NASA Astrophysics Data System (ADS)

    Zimogliadova, T. A.; Drobyaz, E. A.; Golkovskii, M. G.; Bataev, V. A.; Durakov, V. G.; Cherkasova, N. Yu

    2016-11-01

    This paper presents the results of structural investigations and results of tribological and microhardness tests of the coating obtained by electron beam cladding of a Ni-Cr-Si-Fe-B self-fluxing alloy on low-carbon steel. After electron beam treatment high-quality dense layer with a thickness of 1.2-1.8 mm was obtained. The structure of the coating consisted of dendrite crystals based on y-Ni-solid solution and eutectic with complex composition. Microhardness of the coating achieves 370 HV. Wear-resistance of the coating obtained by electron-beam cladding technique was 1.6-fold higher than that of low-carbon carburized steel.

  14. 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.

  15. 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.

  16. 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.

  17. Feasibility study of tungsten as a diffusion barrier between nickel-chromium-aluminum and Gamma/Gamma prime - Delta eutectic alloys

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    Coating systems proposed for potential use on eutectic alloy components in high-temperature gas turbine engines were studied with emphasis on deterioration of such systems by diffusion. A 1-mil thick W sheet was placed between eutectic alloys and a NiCrAl layer. Layered test specimens were aged at 1100 C for as long as long as 500 hours. Without the W barrier, the delta phase of the eutectic deteriorated by diffusion of Nb into the NiCrAl. Insertion of the W barrier stopped the diffusion of Nb from delta. Chromium diffusion from the NiCrAl into the gamma/gamma prime phase of the eutectic was greatly reduced by the barrier. However, the barrier thickness decreased with time; and W diffused into both the NiCrAl and the eutectic. When the delta platelets were alined parallel to the NiCrAl layer, rather than perpendicular, diffusion into the eutectic was reduced.

  18. 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.

  19. Corrosion aspects of Ni-Cr-Fe based and Ni-Cu based steam generator tube materials

    NASA Astrophysics Data System (ADS)

    Dutta, R. S.

    2009-09-01

    This paper reviews corrosion related issues of Ni-Cr-Fe based (in a general sense) and Ni-Cu based steam generator tube materials for nuclear power plants those have been dealt with for last more than four decades along with some updated information on corrosion research. The materials include austenitic stainless steels (SSs), Alloy 600, Monel 400, Alloy 800 and Alloy 690. Compatibility related issues of these alloys are briefly discussed along with the alloy chemistry and microstructure. For austenitic SSs, stress corrosion cracking (SCC) behaviour in high temperature aqueous environments is discussed. For Alloy 600, intergranular cracking in high temperature water including hydrogen-induced intergranular cracking is highlighted along with the interactions of material in various environments. In case of Monel 400, intergranular corrosion and pitting corrosion at ambient temperature and SCC behaviour at elevated temperature are briefly described. For Alloy 800, the discussion covers SCC behaviour, surface characterization and microstructural aspects of pitting, whereas hydrogen-related issues are also highlighted for Alloy 690.

  20. Powder-Derived High-Conductivity Coatings for Copper Alloys

    NASA Technical Reports Server (NTRS)

    Thomas-Ogbuji, Linus U.

    2003-01-01

    Makers of high-thermal-flux engines prefer copper alloys as combustion chamber liners, owing to a need to maximize heat dissipation. Since engine environments are strongly oxidizing in nature and copper alloys generally have inadequate resistance to oxidation, the liners need coatings for thermal and environmental protection; however, coatings must be chosen with great care in order to avoid significant impairment of thermal conductivity. Powder-derived chromia- and alumina- forming alloys are being studied under NASA's programs for advanced reusable launch vehicles to succeed the space shuttle fleet. NiCrAlY and Cu-Cr compositions optimized for high thermal conductivity have been tested for static and cyclic oxidation, and for susceptibility to blanching - a mode of degradation arising from oxidation-reduction cycling. The results indicate that the decision to coat the liners or not, and which coating/composition to use, depends strongly on the specific oxidative degradation mode that prevails under service conditions.

  1. Phase relations in the Fe-Ni-Cr-S system and the sulfidation of an austenitic stainless steel

    NASA Technical Reports Server (NTRS)

    Jacob, K. T.; Rao, D. B.; Nelson, H. G.

    1977-01-01

    The stability fields of various sulfide phases that form on Fe-Cr, Fe-Ni, Ni-Cr and Fe-Cr-Ni alloys were developed as a function of temperature and the partial pressure of sulfur. The calculated stability fields in the ternary system were displayed on plots of log P sub S sub 2 versus the conjugate extensive variable which provides a better framework for following the sulfidation of Fe-Cr-Ni alloys at high temperatures. Experimental and estimated thermodynamic data were used in developing the sulfur potential diagrams. Current models and correlations were employed to estimate the unknown thermodynamic behavior of solid solutions of sulfides and to supplement the incomplete phase diagram data of geophysical literature. These constructed stability field diagrams were in excellent agreement with the sulfide phases and compositions determined during a sulfidation experiment.

  2. HVOF- and HVAF-Sprayed Cr3C2-NiCr Coatings Deposited from Feedstock Powders of Spherical Morphology: Microstructure Formation and High-Stress Abrasive Wear Resistance Up to 800 °C

    NASA Astrophysics Data System (ADS)

    Janka, L.; Norpoth, J.; Trache, R.; Thiele, S.; Berger, L.-M.

    2017-10-01

    Chromium carbide-based coatings are commonly applied to protect surfaces against wear at high temperatures. This work discusses the influence of feedstock powder and spray torch selection on the microstructure and high-stress abrasion resistance of thermally sprayed Cr3C2-NiCr coatings. Four commercial feedstock powders with spherical morphology and different microstructures were deposited by different high-velocity spray processes, namely third-generation gas- and liquid-fueled HVOF torches and by the latest generation HVAF torch. The microstructures of the coatings were studied in the as-sprayed state and after various heat treatments. The high-stress abrasion resistance of as-sprayed and heat-treated coatings was tested at room temperature and at 800 °C. The study reveals that the selection of the spray torch mainly affects the room temperature abrasion resistance of the as-sprayed coatings, which is due to differences in the embrittlement of the binder phase generated by carbide dissolution. At elevated temperatures, precipitation and growth of secondary carbides yields a fast equalization of the various coatings microstructures and wear properties.

  3. HVOF- and HVAF-Sprayed Cr3C2-NiCr Coatings Deposited from Feedstock Powders of Spherical Morphology: Microstructure Formation and High-Stress Abrasive Wear Resistance Up to 800 °C

    NASA Astrophysics Data System (ADS)

    Janka, L.; Norpoth, J.; Trache, R.; Thiele, S.; Berger, L.-M.

    2017-08-01

    Chromium carbide-based coatings are commonly applied to protect surfaces against wear at high temperatures. This work discusses the influence of feedstock powder and spray torch selection on the microstructure and high-stress abrasion resistance of thermally sprayed Cr3C2-NiCr coatings. Four commercial feedstock powders with spherical morphology and different microstructures were deposited by different high-velocity spray processes, namely third-generation gas- and liquid-fueled HVOF torches and by the latest generation HVAF torch. The microstructures of the coatings were studied in the as-sprayed state and after various heat treatments. The high-stress abrasion resistance of as-sprayed and heat-treated coatings was tested at room temperature and at 800 °C. The study reveals that the selection of the spray torch mainly affects the room temperature abrasion resistance of the as-sprayed coatings, which is due to differences in the embrittlement of the binder phase generated by carbide dissolution. At elevated temperatures, precipitation and growth of secondary carbides yields a fast equalization of the various coatings microstructures and wear properties.

  4. Interface Microstructure and Tribological Properties of Flame Spraying NiCr/La2O3 Coatings

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenyu; Liang, Bunv; Guo, Hongjian

    2014-12-01

    NiCr alloy coatings with 0.5, 1.0, 1.5 and 2.0 wt.% of La2O3 were deposited on 1045 carbon steel by a flame spraying and melting processing. Interface microstructure investigations of the coating/substrate systems were conducted by field emission gun scanning electron microscopy, with attached energy dispersive spectroscopy. The effect of La2O3 addition on the tribological properties of the coatings was investigated under dry sliding wear conditions. The result showed that the microstructure of the NiCr alloy coatings are refined with proper amounts of La2O3, and the microhardness and wear resistance of the coatings show best enhancement with 1.0% La2O3.

  5. Fabrication and Characterization of Ni-P-CoNiCrAlY Composite Coatings

    NASA Astrophysics Data System (ADS)

    Heydari, H.; Monirvaghefi, S. M.; Hadipour, Ali

    2017-03-01

    In this study, Ni-P-CoNiCrAlY composite coatings were deposited on 310 stainless steel. The surface morphology and cross-sectional observations were carried out using scanning electron microscopy and optical microscopy. The high-temperature corrosion of all coatings was evaluated by cyclic oxidation method. According to the results, the amounts of CoNiCrAlY particles co-deposited in all samples coated at pH = 4.7 were higher than that of those produced at pH = 6.7. Also, the surface roughness of all composite coatings coated at pH = 6.7 is lower than the coatings produced at pH = 4.7. The Ni-P-(3 g/l) CoNiCrAlY deposit produced at pH = 6.7 had the best corrosion resistance among other coatings.

  6. Fabrication and Characterization of Ni-P-CoNiCrAlY Composite Coatings

    NASA Astrophysics Data System (ADS)

    Heydari, H.; Monirvaghefi, S. M.; Hadipour, Ali

    2017-02-01

    In this study, Ni-P-CoNiCrAlY composite coatings were deposited on 310 stainless steel. The surface morphology and cross-sectional observations were carried out using scanning electron microscopy and optical microscopy. The high-temperature corrosion of all coatings was evaluated by cyclic oxidation method. According to the results, the amounts of CoNiCrAlY particles co-deposited in all samples coated at pH = 4.7 were higher than that of those produced at pH = 6.7. Also, the surface roughness of all composite coatings coated at pH = 6.7 is lower than the coatings produced at pH = 4.7. The Ni-P-(3 g/l) CoNiCrAlY deposit produced at pH = 6.7 had the best corrosion resistance among other coatings.

  7. Heredity of medium-range order structure from melts to the microstructure of Ni-Cr-W superalloy

    NASA Astrophysics Data System (ADS)

    Gao, Zhongtang; Hu, Rui; Wang, Jun; Li, Jinshan

    2015-07-01

    The structure factor S( Q), intensities and pair distribution function g( r) of liquid Ni-Cr-W superalloy at different temperatures have been measured by a high-temperature X-ray diffractometer. Coordination N min, correlation radius r c, the nearest atomic distance r 1, solidification microstructure and compression performance have been studied. The results show that a pre-peak exists on the structure factor curve at the liquidus temperature, and a fine structure of equiaxed, globular and non-dendritic primary grains can be achieved by casting the alloy at liquidus temperature. Liquid structure feature of Ni-Cr-W superalloy is found to depend on temperature. During the solidification, some structural information carried by the medium-range order (MRO) structure is inherited from the melt to the microstructure, which is beneficial for grain refinement. The maximum yield strength measured from typical microstructure of the equiaxed and non-dendritic grains at 1400 °C is 543 MPa. The results show that refinement and non-dendritic grain is beneficial to the improvement of the yield strength.

  8. Phase relations in the Nb-Ni-Cr system at 1,100 °C.

    PubMed

    Kodentsov, Alexander A; van Loo, Frans J J

    The isothermal cross section through the ternary phase diagram Nb-Ni-Cr at 1,100 °C was constructed by means of diffusion couples and equilibrated alloys. It was found that nearly 28 at.% of Cr can be dissolved in the μ phase (Nb7Ni6) at this temperature, and the solubility of chromium in NbNi3 is approximately 5 at.%. Under these circumstances the low-temperature (cubic) modification of the NbCr2 Laves phase can dissolve up to 6 at.% of nickel, but further increase of the Ni content (up to approximately 10 at.%) stabilizes the hexagonal (high-temperature) modification of the Laves phase. The presence of this pseudo-ternary compound which is in equilibrium with all binary intermetallics and body-centred cubic (BCC) Nb- and Cr-based solid solutions largely determines the topology of the isotherm at 1,100 °C. The formation of this phase was also observed in the reaction zone between Nb and Ni-Cr solid solution when chromium concentration exceeded 15 at.%.

  9. Hot corrosion of four superalloys - HA-188, S-57, IN-617, and TD-NiCrAl

    NASA Technical Reports Server (NTRS)

    Santoro, G. J.

    1979-01-01

    Cyclic oxidation and hot corrosion tests of two cobalt-base and two nickel-base alloys are reported. The alloys were exposed to maximum temperatures of 900 and 1000 C in a Mach 0.3 burner rig whose flame was doped with various concentrations of sea salt and sodium sulfate for hot corrosion tests. The test data were subjected to a regression analysis for the development of model equations relating corrosion to temperature and for the effects of salt concentration and composition on corrosion. The corrosion resistance varied with temperature, sea salt concentration, and salt composition, concluding that the S-57 cobalt-base alloy was the most hot corrosion-resistant alloy, and the TD-NiCrAl nickel-base alloy was the least resistant. However, under straight oxidation conditions, the TD-NiCrAl was most resistant, while S-57 was the least resistant alloy.

  10. High strength nickel-chromium-iron austenitic alloy

    DOEpatents

    Gibson, Robert C.; Korenko, Michael K.

    1980-01-01

    A solid solution strengthened Ni-Cr-Fe alloy capable of retaining its strength at high temperatures and consisting essentially of 42 to 48% nickel, 11 to 13% chromium, 2.6 to 3.4% niobium, 0.2 to 1.2% silicon, 0.5 to 1.5% vanadium, 2.6 to 3.4% molybdenum, 0.1 to 0.3% aluminum, 0.1 to 0.3% titanium, 0.02 to 0.05% carbon, 0.002 to 0.015% boron, up to 0.06 zirconium, and the balance iron. After solution annealing at 1038.degree. C. for one hour, the alloy, when heated to a temperature of 650.degree. C., has a 2% yield strength of 307 MPa, an ultimate tensile strength of 513 MPa and a rupture strength of as high as 400 MPa after 100 hours.

  11. The oxidation and corrosion of ODS alloys

    NASA Technical Reports Server (NTRS)

    Lowell, Carl E.; Barrett, Charles A.

    1990-01-01

    The oxidation and hot corrosion of high temperature oxide dispersion strengthened (ODS) alloys are reviewed. The environmental resistance of such alloys are classified by oxide growth rate, oxide volatility, oxide spalling, and hot corrosion limitations. Also discussed are environmentally resistant coatings for ODS materials. It is concluded that ODS NiCrAl and FeCrAl alloys are highly oxidation and corrosion resistant and can probably be used uncoated.

  12. Enhanced magnetodielectric response in Dy modified NiCr2O4

    NASA Astrophysics Data System (ADS)

    Mandal, P. R.; Singh, Ripandeep; Das, A.; Sarkar, Tarapada; Nath, T. K.

    2017-06-01

    The chemically synthesized high purity spinel NiCr2-xDyxO4 (x = 0, 0.1) samples have been characterized using magnetic and dielectric measurements in presence of high magnetic field. Crystal and magnetic structure of the samples have been determined by analyzing neutron diffraction data recorded between temperature of 6 K and 300 K. NiCr2O4 crystallizes in tetragonal phase with the space group of I41/amd whereas NiCr1.9Dy0.1O4 crystallizes in the mixed phase of cubic (space group of Fd 3 bar m) and tetragonal phases at room temperature. An additional phase of DyCrO3 with orthorhombic structure has been found in the Dy doped compound. The lattice parameter a increases and the c decreases in tetragonal structure with the substitution of Dy in Cr site. Both the samples show superlattice reflection peak indicating the presence of long range AFM ordering (transverse component) below 40 K. But the saturation magnetization slightly increases after Dy doping. An anomaly observed near Curie temperature in ε‧ (T) of NiCr2O4 and NiCr1.9Dy0.1O4 demonstrates the contribution of coupling between ferroelectricity and ferrimagnetism in the compounds. A linear correlation between the difference in dielectric constant and the field dependent squared magnetization for both the samples has been observed. The spin-spin interactions are most likely responsible for the observed magnetodielectric (MD) effect due to the magnetodielectric hysteresis in both parent and doped samples. Interestingly the MD% is found to increase with Dy doping.

  13. Factors Affecting the Hydrogen Embrittlement Resistance of Ni-Cr-Mn-Nb Welds

    SciTech Connect

    G.A. Young; C.K. Battige; N. Liwis; M.A. Penik; J. Kikel; A.J. Silvia; C.K. McDonald

    2001-03-18

    Nickel based alloys are often welded with argon/hydrogen shielding gas mixtures to minimize oxidation and improve weld quality. However, shielding gas mixtures with {ge} 1% hydrogen additions can result in hydrogen concentrations greater than 5 wt. ppm in the weld metal and reduce ductility via hydrogen embrittlement. For the conditions investigated, the degree of hydrogen embrittlement is highly variable between 5 and 14 wt. ppm. investigation of hydrogen embrittlement of EN82H GTAW welds via tensile testing, light microscopy, transmission electron microscopy, orientation imaging microscopy, and thermal desorption spectroscopy shows that this variability is due to the inhomogeneous microstructure of the welds, the presence of recrystallized grains, and complex residual plastic strains. Specifically, research indicates that high residual strains and hydrogen trapping lower the ductility of Ni-Cr-Mn-Nb weld metal when dissolved hydrogen concentrations are greater than 5 wt. ppm. The inhomogeneous microstructure contains columnar dendritic, cellular dendritic, and recrystallized grains. The decreased tensile ductility observed in embrittled samples is recovered by post weld heat treatments that decrease the bulk hydrogen concentration below 5 wt. ppm.

  14. High strength alloys

    DOEpatents

    Maziasz, Phillip James [Oak Ridge, TN; Shingledecker, John Paul [Knoxville, TN; Santella, Michael Leonard [Knoxville, TN; Schneibel, Joachim Hugo [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Vinegar, Harold J [Bellaire, TX; John, Randy Carl [Houston, TX; Kim, Dong Sub [Sugar Land, TX

    2010-08-31

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.

  15. High strength alloys

    DOEpatents

    Maziasz, Phillip James; Shingledecker, John Paul; Santella, Michael Leonard; Schneibel, Joachim Hugo; Sikka, Vinod Kumar; Vinegar, Harold J.; John, Randy Carl; Kim, Dong Sub

    2012-06-05

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tublar that is at least partially made from a material containing at least one of the metal alloys.

  16. Microstructure and Sliding Wear Performance of Cr7C3-(Ni,Cr)3(Al,Cr) Coating Deposited from Cr7C3 In Situ Formed Atomized Powder

    NASA Astrophysics Data System (ADS)

    Zhu, Hong-Bin; Shen, Jie; Gao, Feng; Yu, Yueguang; Li, Changhai

    2017-01-01

    This work is aimed at developing a new type of Cr7C3-(Ni,Cr)3(Al,Cr) coating for parts used in heavy-duty diesel engines. The feedstock, in which the stripe-shaped Cr7C3 was in situ formed, was firstly prepared by vacuum melting and gas atomization and then subjected by high-velocity oxy-fuel spraying to form the coatings. The carbon content, microstructure and phase constitution of the powders, as well as the sprayed coatings, were analyzed by chemical analysis, SEM and XRD. The hardness and sliding wear performance of the sprayed coatings were also tested and compared to a commercial Cr3C2-NiCr coating used on piston rings. The results showed that the content of carbon in feedstock was almost the same as designed, and that the volume content of in situ formed Cr7C3 was increased with carbon and chromium added. The major phases of the powders and sprayed coatings are Cr7C3 and Cr-alloyed Ni3Al. Only a small amount of carbon lost during the spraying process. As Cr7C3 content increased in the coatings, the microhardness at room temperature was firstly increased to about 1000Hv0.3. The microhardness of the coatings stayed almost constant, while the testing temperature was raised up to 700 °C for 0.5 h, which illustrates the potential application of the investigated coatings under high temperature conditions. The coatings containing 70 and 77 vol.% Cr7C3 showed the most promising wear resistance, lower friction coefficient and better tribological compatibility to gray cast iron counterpart than other tested Cr7C3-(Ni,Cr)3(Al,Cr) coatings and the reference Cr3C2-NiCr coating.

  17. Oxide Scale Adherence Mechanisms and the Effects of Yttrium, Oxide Particles and Externally Applied Loads on the Oxidation of NiCrAl and CoCrAl Alloys

    DTIC Science & Technology

    1975-06-01

    was performed at a constant strain rate of 0.042%/hr. The tensile testing was accomplished in a creep apparatus where 6-7% and 1- 2 % strains would... 2 . OXIDE SCALE ADHESION I 3. PROBLEMS TO BE STUDIED 2 I! EXPERIM-NTAL 4 I. MATERIALS 4 2 . ALLOY FABRICAllON AND CHiARACTIRIZATION 4 a. As-Cast Alloys...Stress I I e. Specimen (;eometrt’ and Preparation 12 f E-xamination of Oxidized Specimens 12 III RESULTS AND DISCUSSION 13 1. INTRODUCTION 13 2 . THE RATES

  18. The use of Ni-Cr-Si-Be filler metals for brazing of stainless steels

    NASA Astrophysics Data System (ADS)

    Ivannikov, A.; Fedotov, V.; Suchkov, A.; Penyaz, M.; Fedotov, I.; Tarasov, B.

    2016-04-01

    Nanocrystalline ribbon filler metal-alloys of system Ni-Cr-Si-Be are produced by the rapidly quenching of the melt method. By these filler metals carried out hight temperature vacuum brazing of austenitic steels (12Kh18N10T and Kh18N8G2) and austenitic-ferritic class EI-811 (12Kh21N5T). The basic laws of structure-phase state foundation of brazed joints are determined, features of the interaction of the molten filler metal to the brazed materials are identified, the optimal temperature and time parameters of the brazing process are determined.

  19. Microstructure and Thermal Oxidation of Cube Textured NiCrW Metallic Substrate for HTS Coated Conductors

    NASA Astrophysics Data System (ADS)

    Tuissi, A.; Villa, E.; Zamboni, M.

    The non-magnetic highly resistant to oxygenation Ni88Cr8W4 tape demonstrated to be a good metallic substrate for the production high Tc coated conductors. In this work rhe rolling assisted biaxially textured substrates (RABiTS) method has been used to promote a sharp (100)[001] texture on NiCrW metallic tape. The influence of the critical processing parameters on the cube texture development of the tape is investigated Moreover thermal oxidation of the textured NiCrW substrate has been performed at several conditions to study the oxide growth on the surface. Electron BackScatter Diffraction (EBSD) analysis was used for high resolution crystal orientation mapping of the surfaces. The microstructure of the substrates has also been investigated by X-ray and SEM. Differential thermal analysis (TG/DTA) was used to study the oxidation behavior of the NiCrW tapes.

  20. Weldability of High Alloys

    SciTech Connect

    Maroef, I

    2003-01-22

    The purpose of this study was to investigate the effect of silicon and iron on the weldability of HAYNES HR-160{reg_sign} alloy. HR-I60 alloy is a solid solution strengthened Ni-Co-Cr-Si alloy. The alloy is designed to resist corrosion in sulfidizing and other aggressive high temperature environments. Silicon is added ({approx}2.75%) to promote the formation of a protective oxide scale in environments with low oxygen activity. HR-160 alloy has found applications in waste incinerators, calciners, pulp and paper recovery boilers, coal gasification systems, and fluidized bed combustion systems. HR-160 alloy has been successfully used in a wide range of welded applications. However, the alloy can be susceptible to solidification cracking under conditions of severe restraint. A previous study by DuPont, et al. [1] showed that silicon promoted solidification cracking in the commercial alloy. In earlier work conducted at Haynes, and also from published work by DuPont et al., it was recognized that silicon segregates to the terminal liquid, creating low melting point liquid films on solidification grain boundaries. Solidification cracking has been encountered when using the alloy as a weld overlay on steel, and when joining HR-160 plate in a thickness greater than19 millimeters (0.75 inches) with matching filler metal. The effect of silicon on the weldability of HR-160 alloy has been well documented, but the effect of iron is not well understood. Prior experience at Haynes has indicated that iron may be detrimental to the solidification cracking resistance of the alloy. Iron does not segregate to the terminal solidification product in nickel-base alloys, as does silicon [2], but iron may have an indirect or interactive influence on weldability. A set of alloys covering a range of silicon and iron contents was prepared and characterized to better understand the welding metallurgy of HR-160 alloy.

  1. Influence of Al2O3 Particle Size on Microstructure, Mechanical Properties and Abrasive Wear Behavior of Flame-Sprayed and Remelted NiCrBSi Coatings

    NASA Astrophysics Data System (ADS)

    Habib, K. A.; Cano, D. L.; Caudet, C. T.; Damra, M. S.; Cervera, I.; Bellés, J.; Ortells, P.

    2017-04-01

    The influence of micrometric alumina (low surface area-to-volume ratio) and nanometric alumina (high surface area-to-volume ratio) on microstructure, hardness and abrasive wear of a NiCrBSi hardfacing alloy coating applied to an AISI 304 substrate using flame spraying (FS) combined with surface flame melting (SFM) is studied. Remelting after spraying improved the mechanical and tribological properties of the coatings. Microstructural characterization using XRD, SEM and EDS indicated that alumina additions produced similar phases (NiSi, Ni3B, CrC and Ni31Si12) regardless of the alumina size, but the phases differed in morphology, size distribution and relative proportions from one coating to another. The addition of 12 wt.% nanometric Al2O3 increased the phases concentration more than five- to sixfold and reduced the hard phases size about four-to threefold compared with NiCrBSi + 12 wt.% micrometric Al2O3. Nanoalumina led to reduced mass loss during abrasive wear compared to micrometric alumina and greater improvement in hardness.

  2. Influence of Al2O3 Particle Size on Microstructure, Mechanical Properties and Abrasive Wear Behavior of Flame-Sprayed and Remelted NiCrBSi Coatings

    NASA Astrophysics Data System (ADS)

    Habib, K. A.; Cano, D. L.; Caudet, C. T.; Damra, M. S.; Cervera, I.; Bellés, J.; Ortells, P.

    2017-03-01

    The influence of micrometric alumina (low surface area-to-volume ratio) and nanometric alumina (high surface area-to-volume ratio) on microstructure, hardness and abrasive wear of a NiCrBSi hardfacing alloy coating applied to an AISI 304 substrate using flame spraying (FS) combined with surface flame melting (SFM) is studied. Remelting after spraying improved the mechanical and tribological properties of the coatings. Microstructural characterization using XRD, SEM and EDS indicated that alumina additions produced similar phases (NiSi, Ni3B, CrC and Ni31Si12) regardless of the alumina size, but the phases differed in morphology, size distribution and relative proportions from one coating to another. The addition of 12 wt.% nanometric Al2O3 increased the phases concentration more than five- to sixfold and reduced the hard phases size about four-to threefold compared with NiCrBSi + 12 wt.% micrometric Al2O3. Nanoalumina led to reduced mass loss during abrasive wear compared to micrometric alumina and greater improvement in hardness.

  3. Metallographic etching and microstructure characterization of NiCrMoV rotor steels for nuclear power

    NASA Astrophysics Data System (ADS)

    Liu, Peng; Lu, Feng-gui; Liu, Xia; Gao, Yu-lai

    2013-12-01

    The grain size of prior austenite has a distinct influence on the microstructure and final mechanical properties of steels. Thus, it is significant to clearly reveal the grain boundaries and therefore to precisely characterize the grain size of prior austenite. For NiCrMoV rotor steels quenched and tempered at high temperature, it is really difficult to display the grain boundaries of prior austenite clearly, which limits a further study on the correlation between the properties and the corresponding microstructure. In this paper, an effective etchant was put forward and further optimized. Experimental results indicated that this agent was effective to show the details of grain boundaries, which help analyze fatigue crack details along the propagation path. The optimized corrosion agent is successful to observe the microstructure characteristics and expected to help analyze the effect of microstructure for a further study on the mechanical properties of NiCrMoV rotor steels used in the field of nuclear power.

  4. Long-Term Strength of a Composition of Complex Refractory Coating and Single-Crystal Rhenium-Alloyed Nickel Alloy after High-Temperature Holds

    NASA Astrophysics Data System (ADS)

    Kuznetsov, V. P.; Lesnikov, V. P.; Moroz, E. V.; Khadyev, M. S.; Konakova, I. P.

    2013-11-01

    The long-term strength of a system of single-crystal nickel alloy ZhS36-VI with Cr - Al gas circulation coating (GCC) + Ni - Cr - Al - Ta - Re - Yion-plasma coating (IPC) + Al - Ni - Cr - Yion-plasma coating (IPC) is analyzed under conditions close to the operating ones after a hold for 1 - 1000 h in a temperature range of 1050 - 1300°C.

  5. 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.

  6. Improved oxide spallation resistance of microcrystalline Ni-Cr-Al coatings

    SciTech Connect

    Liu, Z.; Gao, W.; Dahm, K.L.; Wang, F.

    1998-08-01

    Microcrystalline Ni-20Cr-3Al coatings were deposited on Ni-20Cr-3Al substrates by unbalanced magnetron-sputter deposition. The grain size of the coatings was varied by using different Ar pressures. Cyclic-oxidation testing was performed at 1100 C. It was found that (1) an external {alpha}-Al{sub 2}O{sub 3} scale formed on coating A (4.7 {micro}m thick, 50 nm grain size); (2) an external Cr{sub 2}O{sub 3} scale and internal Al{sub 2}O{sub 3} oxide formed on coating B (14 {micro}m thick, 500 nm grain size); and (3) an outer layer scale of Cr{sub 2}O{sub 3} + NiCr{sub 2}O{sub 4} and interior layer of Al{sub 2}O{sub 3} formed on the as-cast alloy. Extensive spallation of the Cr{sub 2}O{sub 3} + NiCr{sub 2}O{sub 4} scale took place on the as-cast alloy, but no obvious spallation occurred on the two coatings. Improvement of the spallation resistance of the scale is explained by effective diffusional creep of the coatings and the micropegging effect of the inward-grown oxides.

  7. Alloy composition effects on oxidation products of VIA, B-1900, 713C, and 738X: A high temperature diffractometer study

    NASA Technical Reports Server (NTRS)

    Garlick, R. G.; Lowell, C.

    1973-01-01

    High temperature X-ray diffraction studies were performed to investigate isothermal and cyclic oxidation at 1000 and 1100 C of the nickel-base superalloys VIA, B-1900, 713C, and 738X. Oxidation was complex. The major oxides, Al2O3, Cr2O3, and the spinels, formed in amounts consistent with alloy chemistry. The alloys VIA and B-1900 (high Al, low Cr alloys) tended to form Al2O3 and NiAl2O4; 738X (high Cr, low Al) formed Cr2O3 and NiCr2O4. A NiTa2O6 type of oxide formed in amounts approximately proportional to the refractory metal content of the alloy. One of the effects of cycling was to increase the amount of spinels formed.

  8. Materials corrosion of high temperature alloys immersed in 600C binary nitrate salt.

    SciTech Connect

    Kruizenga, Alan Michael; Gill, David Dennis; LaFord, Marianne Elizabeth

    2013-03-01

    Thirteen high temperature alloys were immersion tested in a 60/40 binary nitrate salt. Samples were interval tested up to 3000 hours at 600ÀC with air as the ullage gas. Chemical analysis of the molten salt indicated lower nitrite concentrations present in the salt, as predicted by the equilibrium equation. Corrosion rates were generally low for all alloys. Corrosion products were identified using x-ray diffraction and electron microprobe analysis. Fe-Cr based alloys tended to form mixtures of sodium and iron oxides, while Fe-Ni/Cr alloys had similar corrosion products plus oxides of nickel and chromium. Nickel based alloys primarily formed NiO, with chromium oxides near the oxide/base alloy interface. In625 exhibited similar corrosion performance in relation to previous tests, lending confidence in comparisons between past and present experiments. HA230 exhibited internal oxidation that consisted of a nickel/chromium oxide. Alloys with significant aluminum alloying tended to exhibit superior performance, due formation of a thin alumina layer. Soluble corrosion products of chromium, molybdenum, and tungsten were also formed and are thought to be a significant factor in alloy performance.

  9. Kinetics and Microstructural Investigation of High-Temperature Oxidation of IN-738LC Super Alloy

    NASA Astrophysics Data System (ADS)

    Hamidi, S.; Rahimipour, M. R.; Eshraghi, M. J.; Hadavi, S. M. M.; Esfahani, H.

    2017-02-01

    The present study was carried out to investigate the kinetics and the surface chemistry of the oxide layers formed on the IN-738LC super alloy during high-temperature oxidation at 950 °C in air from 1 to 260 h. Oxidation kinetics were studied by mass gain measurement. The oxide layers were characterized by field emission scanning electron microscope, elemental distribution map, energy-dispersive spectroscopy as well as x-ray diffractometry (XRD). The oxidation kinetics followed the parabolic law. The XRD analysis revealed that the oxide scale contained mainly NiO, Ni (Cr, Al)2O4, Al2O3, TiO2 and Cr2O3. The oxide structure, from the top surface down to the substrate, was clarified by elemental map distribution studies as Ni-Ti oxides, Cr-Ti oxides, Cr2O3 oxide band, Ni-Co-Cr-W oxide and finally a blocky Al2O3 region. The oxidation scales were composed of three distinct layers of the outer and mid layers enriched by TiO2 and Cr2O3, NiCr2O4 oxide, respectively, and the innermost layer was composed of Al2O3 and matrix alloy. The depleted gamma prime layer was formed under the oxidation scales due to the impoverishment of Al and Ti which were induced by the formation of Al2O3 and TiO2.

  10. Kinetics and Microstructural Investigation of High-Temperature Oxidation of IN-738LC Super Alloy

    NASA Astrophysics Data System (ADS)

    Hamidi, S.; Rahimipour, M. R.; Eshraghi, M. J.; Hadavi, S. M. M.; Esfahani, H.

    2016-12-01

    The present study was carried out to investigate the kinetics and the surface chemistry of the oxide layers formed on the IN-738LC super alloy during high-temperature oxidation at 950 °C in air from 1 to 260 h. Oxidation kinetics were studied by mass gain measurement. The oxide layers were characterized by field emission scanning electron microscope, elemental distribution map, energy-dispersive spectroscopy as well as x-ray diffractometry (XRD). The oxidation kinetics followed the parabolic law. The XRD analysis revealed that the oxide scale contained mainly NiO, Ni (Cr, Al)2O4, Al2O3, TiO2 and Cr2O3. The oxide structure, from the top surface down to the substrate, was clarified by elemental map distribution studies as Ni-Ti oxides, Cr-Ti oxides, Cr2O3 oxide band, Ni-Co-Cr-W oxide and finally a blocky Al2O3 region. The oxidation scales were composed of three distinct layers of the outer and mid layers enriched by TiO2 and Cr2O3, NiCr2O4 oxide, respectively, and the innermost layer was composed of Al2O3 and matrix alloy. The depleted gamma prime layer was formed under the oxidation scales due to the impoverishment of Al and Ti which were induced by the formation of Al2O3 and TiO2.

  11. Composition dependence of ternary Pt-Ni-Cr catalyst activity for the methanol electro-oxidation reaction

    NASA Astrophysics Data System (ADS)

    Jeon, Min Ku; McGinn, Paul J.

    Various compositions of binary and ternary Pt-Ni-Cr alloys were investigated as catalysts for the methanol electro-oxidation reaction (MOR). Among the binary (Pt 28Ni 72/C and Pt 28Cr 72/C) and ternary Pt-Ni-Cr catalysts (Pt 28Ni 36Cr 36/C, Pt 22Ni 39Cr 39/C, Pt 33Ni 31Cr 36/C, and Pt 33Ni 36Cr 31/C) examined, the Pt 28Ni 36Cr 36/C composition exhibited the highest MOR mass activity (4.42 A g cat. -1) in the as-prepared version, which was higher than the 3.58 A g cat. -1 value of the PtRu/C catalyst after 60 min of chronoamperometry testing. The order of mass activity for the MOR was Pt 28Ni 36Cr 36/C > Pt 33Ni 36Cr 31/C > Pt 22Ni 39Cr 39/C > Pt 33Ni 31Cr 36/C > Pt 28Cr 72/C > Pt 28Ni 72/C, which was slightly changed to Pt 28Ni 36Cr 36/C > Pt 22Ni 39Cr 39/C > Pt 33Ni 36Cr 31/C > Pt 33Ni 31Cr 36/C > Pt 28Cr 72/C > Pt 28Ni 72/C after a conditioning process. The effect of anodic conditioning was also studied. A combination of X-ray diffraction, cyclic voltammetry, and chronoamperometry experiments revealed that the conditioning process caused dissolution and an oxidation state change of metallic Ni and Cr 2O 3 in the binary catalysts. The higher MOR mass activities of the ternary catalysts compared to the binary ones is attributed to co-alloying of Ni and Cr, leading to exposure of more Pt on the catalyst surface without reducing specific activities of the catalysts. The results of this study also correlate well with a prior ranking of catalytic activity of the same compositions in the form of thin film catalysts that we processed and evaluated by a high-throughput combinatorial approach [J.S. Cooper, M.K. Jeon, P.J. McGinn, Electrochem. Commun. 10 (2008) 1545-1547].

  12. Mechanical Properties and Thermal Shock Resistance of HVOF Sprayed NiCrAlY Coatings Without and With Nano Ceria

    NASA Astrophysics Data System (ADS)

    Sun, Xiaoguang; Chen, Shufen; Wang, You; Pan, Zhaoyi; Wang, Liang

    2012-09-01

    NiCrAlY coatings without and with 0.2 wt.% nano ceria were prepared by high velocity oxygen fuel spraying. The microstructure, mechanical properties, and thermal shock resistance of as-sprayed coatings were investigated. The results showed that in the as-sprayed coatings, the number of un-melted particles was reduced drastically, the microstructure was refined and compact due to the refinement of sprayable powders. Both the hardness and adhesive strength of the NiCrAlY increased due to the refinement of microstructure and the decrease of the defects, such as pores and oxides, after adding nano ceria. The thermal cycle life of NiCrAlY coatings was improved by 15% after adding 0.2 wt.% nano ceria, which is attributed to the low content of spinel NiCr2O4 and high content of Cr2O3 in the thermal cycling, the refined and compact microstructure, and increased interfacial boundary.

  13. 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.

  14. 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.

  15. High-Temperature Oxidation Behavior of Al-Co-Cr-Ni-(Fe or Si) Multicomponent High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Butler, T. M.; Alfano, J. P.; Martens, R. L.; Weaver, M. L.

    2015-01-01

    High-entropy alloys (HEAs) are a class of alloys that are being considered for a number of applications. In the present study, the microstructures and 1050°C oxidation behaviors of two HEAs, Al10Cr22.5Co22.5Ni22.5Fe22.5 (at.%) and Al20Cr25Co25Ni25Si5 have been investigated along with Al15Cr10Co35Ni35Si5, which is a high-temperature shape-memory alloy. Oxide formation occurred via selective oxidation in a manner that was consistent with the oxide formation model devised by Giggins and Pettit for model Ni-Cr-Al alloys. The lower Al content alloy formed an external Cr2O3 scale and an internal subscale consisting of Al2O3 and AlN precipitates. The higher Al content alloys exhibited smaller mass gains and formed external Al2O3 scales without any internal oxidation of the alloys.

  16. 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.

  17. In situ Raman spectroscopic analysis of surface oxide films on Ni-base alloy/low alloy steel dissimilar metal weld interfaces in high-temperature water

    NASA Astrophysics Data System (ADS)

    Kim, Jongjin; Choi, Kyung Joon; Bahn, Chi Bum; Kim, Ji Hyun

    2014-06-01

    In situ Raman spectroscopy has been applied to analyze the surface oxide films formed on dissimilar metal weld (DMW) interfaces of nickel-base alloy/low alloy steel under hydrogenated high-temperature water condition. For the analysis of the oxide films under high temperature/pressure aqueous conditions, an in situ Raman spectroscopy system was developed by constructing a hydrothermal cell where the entire optics including the excitation laser and the Raman light collection system were located at the nearest position to the specimen by means of immersion optics. In situ Raman spectra of the DMW interfaces were collected in hydrogenated water condition at different temperatures up to 300 °C. The measured in situ Raman spectra showed peaks of Cr2O3, NiCr2O4 and Fe3O4 at the DMW interface. It is considered that differences in the oxide chemistry originated from the chemical element distribution inside of the DMW interface region.

  18. 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.

  19. Effects of chemical composition on the corrosion of dental alloys.

    PubMed

    Galo, Rodrigo; Ribeiro, Ricardo Faria; Rodrigues, Renata Cristina Silveira; Rocha, Luís Augusto; de Mattos, Maria da Glória Chiarello

    2012-01-01

    The aim of this study was to determine the effect of the oral environment on the corrosion of dental alloys with different compositions, using electrochemical methods. The corrosion rates were obtained from the current-potential curves and electrochemical impedance spectroscopy (EIS). The effect of artificial saliva on the corrosion of dental alloys was dependent on alloy composition. Dissolution of the ions occurred in all tested dental alloys and the results were strongly dependent on the general alloy composition. Regarding the alloys containing nickel, the Ni-Cr and Ni-Cr-Ti alloys released 0.62 mg/L of Ni on average, while the Co-Cr dental alloy released ions between 0.01 and 0.03 mg/L of Co and Cr, respectively.The open-circuit potential stabilized at a higher level with lower deviation (standard deviation: Ni-Cr-6Ti = 32 mV/SCE and Co-Cr = 54 mV/SCE). The potenciodynamic curves of the dental alloys showed that the Ni-based dental alloy with >70 wt% of Ni had a similar curve and the Co-Cr dental alloy showed a low current density and hence a high resistance to corrosion compared with the Ni-based dental alloys. Some changes in microstructure were observed and this fact influenced the corrosion behavior for the alloys. The lower corrosion resistance also led to greater release of nickel ions to the medium. The quantity of Co ions released from the Co-Cr-Mo alloy was relatively small in the solutions. In addition, the quantity of Cr ions released into the artificial saliva from the Co-Cr alloy was lower than Cr release from the Ni-based dental alloys.

  20. Influence of Ni-Cr substitution on the magnetic and electric properties of magnesium ferrite nanomaterials

    SciTech Connect

    Iqbal, Muhammad Javed; Ahmad, Zahoor; Meydan, Turgut; Nlebedim, Ikenna Cajetan

    2012-02-15

    Graphical abstract: Variation of saturation magnetization (M{sub S}) and magnetocrystalline anisotropy coefficient (K{sub 1}) with Ni-Cr content for Mg{sub 1-x}Ni{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4} (x = 0.0-0.5). Highlights: Black-Right-Pointing-Pointer Mg{sub 1-x}Ni{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4} are synthesized by novel PEG assisted microemulsion method. Black-Right-Pointing-Pointer High field regime of M-H loops are modeled using Law of Approach to saturation. Black-Right-Pointing-Pointer A considerable increase in the value of M{sub S} from 148 kA/m to 206 kA/m is achieved Black-Right-Pointing-Pointer {rho}{sup RT} enhanced to the order of 10{sup 9} {Omega}cm at potential operational range around 300 K. -- Abstract: The effect of variation of composition on the structural, morphological, magnetic and electric properties of Mg{sub 1-x}Ni{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4} (x = 0.0-0.5) nanocrystallites is presented. The samples were prepared by novel polyethylene glycol (PEG) assisted microemulsion method with average crystallite size of 15-47 nm. The microstructure, chemical, and phase analyses of the samples were studied by the scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray fluorescence (ED-XRF), and X-ray diffraction (XRD). Compositional variation greatly affected the magnetic and structural properties. The high-field regimes of the magnetic loops are modelled using the Law of Approach (LOA) to saturation in order to extract information about their anisotropy and the saturation magnetization. Thermal demagnetization measurements are carried out using VSM and significant enhancement of the Curie temperature from 681 K to 832 K has been achieved by substitution of different contents of Ni-Cr. The dc-electrical resistivity ({rho}{sup RT}) at potential operational range around 300 K is increased from 7.5 Multiplication-Sign 10{sup 8} to 4.85 Multiplication-Sign 10{sup 9} {Omega}cm with the increase in Ni-Cr contents

  1. Distribution of Cd, Ni, Cr and Pb in sewage sludge amended soils

    NASA Astrophysics Data System (ADS)

    Sanfeliu, Teófilo

    2010-05-01

    , organic matter and clay content, is essential. The sewage sludge incorporation has modified the soil composition, leading to the increment of heavy metals. The heavy metals in this set of sewage sludge amended soils were mostly and variously associated with residual, reducible and carbonate forms depending on the nature and properties of the soils. Mainly, Ni, Cr and Pb are associated with residual phase. However, Cd is mainly associated with carbonate forms. Use of X-rays diffraction to observe possible associations of heavy metals with soil constituents proved to be unsuccessful due to a combination of the highly dispersed distribution of the heavy metals in the soil matrix.

  2. 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.

  3. Synthesis of High-Temperature Self-lubricating Wear Resistant Composite Coating on Ti6Al4V Alloy by Laser Deposition

    NASA Astrophysics Data System (ADS)

    Luo, Jian; Liu, Xiu-Bo; Xiang, Zhan-Feng; Shi, Shi-Hong; Chen, Yao; Shi, Gao-Lian; Wu, Shao-Hua; Wu, Yu-Nan

    2015-05-01

    Laser deposition was adopted to prepare novel Ni-based solid solution (γ-NiCrAlTi)/ TiC/α-Ti/CaF2 high-temperature self-lubricating wear resistant composite coating on Ti6Al4V alloy. Microstructure, micro-hardness, wear behavior, and counter-body effect of the coating were investigated systematically. It can be seen that the coating mainly consists of γ-NiCrAlTi, TiC, α-Ti, and small fine CaF2 particles. Average micro-hardness of the coating is 1023 HV0.3, which is about three-factor higher than that of Ti6Al4V substrate (380 HV0.3). The friction coefficient and wear rate of the coating decrease at all test temperatures to different extents with respect to the substrate. The improvement in wear resistance is believed to be the combined effects of the γ-NiCrAlTi solid solution, the dominating anti-wear capabilities of the reinforced TiC carbides, and the self-lubricating property of CaF2.

  4. Surface oxidation of cube-textured Ni-Cr for the formation of a NiO buffer layer for superconducting coated conductors

    NASA Astrophysics Data System (ADS)

    Lockman, Z.; Qi, X.; Berenov, A.; Goldacker, W.; Nast, R.; deBoer, B.; Holzapfel, B.; MacManus-Driscoll, J. L.

    2002-12-01

    The surface oxidation epitaxy behaviour of the rolling assisted biaxially textured substrates of cube-textured Ni-10%Cr and Ni-13%Cr foils were investigated, in air, at 1050 °C. For both alloys, the optimum out-of-plane texture of cube oriented NiO was obtained for the shortest oxidation times, t, of a few minutes, although a strong texture still remained for longer times. For t<40 min, the NiO layer showed both 0° and 45° in-plane orientations with respect to the underlying Ni-Cr, whereas for t⩾40 min, a single, 45° in-plane orientation was observed. The surface roughness of the NiO layer was the lowest after ∼10-40 min oxidation. For oxidation times longer than 40 min, the macroscopic NiO roughness (mm 2 scale) increased dramatically due to a festooning effect. A fully connected Cr 2O 3 layer formed at the interface between the Ni and NiO for even the shortest oxidation times (few minutes). The Cr 2O 3 layer acted as a diffusion barrier to Ni, and limited the thickness of the surface NiO to a few microns, almost independent of oxidation time. The surface NiO layer showed better adherence to the Ni-10%Cr than to the Ni-13%Cr. For superconducting coated conductor applications, the optimum NiO buffer layer is formed on Ni-10%Cr foil after oxidation at 1050 °C for ∼40 min. The important columnar surface layer is ∼ 7 μm thick, is highly textured with an r.m.s. surface roughness of ∼200 nm on a mm 2 scale, and ∼100 nm on the scale of the grain size. The layer shows good adherence to the underlying Cr 2O 3/Ni-Cr.

  5. Hot hardness of nickel-rich nickel-chromium-aluminum alloys

    NASA Technical Reports Server (NTRS)

    Levine, S. R.

    1976-01-01

    Rockwell A hardness of cast nickel-chromium-aluminum (NiCrAl) alloys was examined from ambient to 1150 K and compared to cast NiAl and IN-100. Alloy constitution was either gamma, gamma prime + gamma or gamma + beta + alpha + gamma prime. Below 1000 K beta containing NiCrAl alloys have hardnesses comparable to IN-100; above 1000 K they soften faster than IN-100. At 1150 K the hardness of beta-containing NiCrAl alloys decreases with increasing beta-content. The beta-containing NiCrAl alloys were harder than beta-NiAl. The ultimate tensile strengths of the NiCrAl alloys were estimated. The effects of NiCrAl coatings on strength and fatigue life of cooled turbine components were deduced.

  6. Effects of high temperature treatment on microstructure and mechanical properties of laser-clad NiCrBSi/WC coatings on titanium alloy substrate

    SciTech Connect

    Li, Guang Jie; Li, Jun Luo, Xing

    2014-12-15

    Laser-clad composite coatings on the Ti6Al4V substrate were heat-treated at 700, 800, and 900 °C for 1 h. The effects of post-heat treatment on the microstructure, microhardness, and fracture toughness of the coatings were investigated by scanning electron microscopy, X-ray diffractometry, energy dispersive spectroscopy, and optical microscopy. The wear resistance of the coatings was evaluated under dry reciprocating sliding friction at room temperature. The coatings mainly comprised some coarse gray blocky (W,Ti)C particles accompanied by the fine white WC particles, a large number of black TiC cellular/dendrites, and the matrix composed of NiTi and Ni{sub 3}Ti; some unknown rich Ni- and Ti-rich particles with sizes ranging from 10 nm to 50 nm were precipitated and uniformly distributed in the Ni{sub 3}Ti phase to form a thin granular layer after heat treatment at 700 °C. The granular layer spread from the edge toward the center of the Ni{sub 3}Ti phase with increasing temperature. A large number of fine equiaxed Cr{sub 23}C{sub 6} particles with 0.2–0.5 μm sizes were observed around the edges of the NiTi supersaturated solid solution when the temperature was further increased to 900 °C. The microhardness and fracture toughness of the coatings were improved with increased temperature due to the dispersion-strengthening effect of the precipitates. Dominant wear mechanisms for all the coatings included abrasive and delamination wear. The post-heat treatment not only reduced wear volume and friction coefficient, but also decreased cracking susceptibility during sliding friction. Comparatively speaking, the heat-treated coating at 900 °C presented the most excellent wear resistance. - Highlights: • TiC + WC reinforced intermetallic compound matrix composite coatings were produced. • The formation mechanism of the reinforcements was analyzed. • Two precipitates were generated at elevated temperature. • Cracking susceptibility and microhardness of the coatings were improved. • Post-heat treatment enhances wear resistance of the coatings.

  7. 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.

  8. The effect of alloy composition on the localized corrosion behavior of nickel-chromium-molybdenum alloys

    NASA Astrophysics Data System (ADS)

    Wong, Fariaty

    Ni-Cr-Mo alloys are one of the most versatile Ni-based alloys because they resist corrosion in a variety of environments. This versatility is due to the combination of Cr and Mo additions to the alloy. These alloying elements complement each other in producing a highly corrosion resistant alloy. The concentration of the elements in the alloy establishes the corrosion behavior of these alloys. In this study, Ni-Cr-Mo alloys with varying composition were studied using electrochemical methods. The dependency of pitting corrosion on the alloy chemistry was captured in empirical models that roughly rank the pitting susceptibility of the Ni-Cr-Mo alloys studied. The same type of model was also constructed for capturing the effect of alloy composition on the repassivation potential. It was found that these models were specific in terms of alloying element effects on the type of environments exposed to the alloys particularly, pH and temperature. The addition of chromium was shown to contribute to the higher pitting potential on the Ni-Cr-Mo alloys in neural chloride environment while molybdenum was dominant in acidified chloride solutions. In regards to the repassivation potential, both chromium and molybdenum affect the repassivation potential more or less evenly in neutral pH solutions. Under low pH high temperature conditions, molybdenum content has a greater effect on the repassivation potential value than chromium. Stabilization of localized corrosion is increasingly difficult as alloying element content increases. However, metastable pitting occurs in most alloys and the metastable pitting behavior of several Ni-Cr-Mo alloys was studied through potentiostatic analysis. Higher chromium and molybdenum contents decreased the metastable pitting incidence; although, the effect of Mo content was observed to be more dominant. Molybdenum additions were found to suppress the growth of the metastable pits. The growth rate of the fastest growing pits was also reduced by

  9. Atomic displacement in the CrMnFeCoNi high-entropy alloy - A scaling factor to predict solid solution strengthening

    NASA Astrophysics Data System (ADS)

    Okamoto, Norihiko L.; Yuge, Koretaka; Tanaka, Katsushi; Inui, Haruyuki; George, Easo P.

    2016-12-01

    Although metals strengthened by alloying have been used for millennia, models to quantify solid solution strengthening (SSS) were first proposed scarcely seventy years ago. Early models could predict the strengths of only simple alloys such as dilute binaries and not those of compositionally complex alloys because of the difficulty of calculating dislocation-solute interaction energies. Recently, models and theories of SSS have been proposed to tackle complex high-entropy alloys (HEAs). Here we show that the strength at 0 K of a prototypical HEA, CrMnFeCoNi, can be scaled and predicted using the root-mean-square atomic displacement, which can be deduced from X-ray diffraction and first-principles calculations as the isotropic atomic displacement parameter, that is, the average displacements of the constituent atoms from regular lattice positions. We show that our approach can be applied successfully to rationalize SSS in FeCoNi, MnFeCoNi, MnCoNi, MnFeNi, CrCoNi, CrFeCoNi, and CrMnCoNi, which are all medium-entropy subsets of the CrMnFeCoNi HEA.

  10. 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.

  11. Multicomponent interdiffusion in austenitic nickel-, iron-nickel-base alloys and L1(2)-nickel-aluminum intermetallic for high-temperature applications

    NASA Astrophysics Data System (ADS)

    Garimella, Narayana

    Interdiffusion in multicomponent-multiphase alloys is commonly encountered in many materials systems. The developments of multicomponent-multiphase alloys require control of microstructure through appropriate heat treatment, involving solid-state transformations, precipitation processes, and surface modification, where the interdiffusion processes play a major role. In addition, interdiffusion processes often control degradation and failure of these materials systems. Enhanced performance and reliable durability always requires a detailed understanding of interdiffusion. In this study, ternary and quaternary interdiffusion in Ni-Cr-X (X = Al, Si, Ge, Pd) at 900°C and 700°C, Fe-Ni-Cr-X (X = Si, Ge) at 900°C, and Ni3Al alloyed with Ir, Ta and Re at 1200°C were examined using solid-to-solid diffusion couples. Interdiffusion fluxes of individual components were calculated directly from experimental concentration profiles determined by electron probe microanalysis. Moments of interdiffusion fluxes were examined to calculate main and cross interdiffusion coefficients averaged over selected composition ranges from single diffusion couple experiments. Consistency in the magnitude and sign of ternary and quaternary interdiffusion coefficient were verified with interdiffusion coefficients determined by Boltzmann-Matano analysis that requires multiple diffusion couples with intersecting compositions. Effects of alloying additions, Al, Si, Ge and Pd, on the interdiffusion in Ni-Cr-X and Fe-Ni-Cr-X alloys were examined with respect to Cr2O 3-forming ability at high temperature. Effects of Ir, Ta and Re additions on interdiffusion in Ni3Al were examined with respect to phase stability and site-preference. In addition, a numerically refined approach to determine average ternary interdiffusion coefficients were developed. Concentrations and moments of interdiffusion fluxes are employed to generate multiple combinations of multicomponent interdiffusion coefficient as a function

  12. New generation super alloy candidates for medical applications: corrosion behavior, cation release and biological evaluation.

    PubMed

    Reclaru, L; Ziegenhagen, R; Unger, R E; Eschler, P Y; Constantin, F

    2014-12-01

    Three super alloy candidates (X1 CrNiMoMnW 24-22-6-3-2 N, NiCr21 MoNbFe 8-3-5 AlTi, CoNiCr 35-20 Mo 10 BTi) for a prolonged contact with skin are evaluated in comparison with two reference austenitic stainless steels 316L and 904L. Several electrochemical parameters were measured and determined (E(oc), E(corr), i(corr), b(a), b(c), E(b), R(p), E(crev) and coulometric analysis) in order to compare the corrosion behavior. The cation release evaluation and in vitro biological characterization also were performed. In terms of corrosion, the results reveal that the 904L steels presented the best behavior followed by the super austenitic steel X1 CrNiMoMnW 24-22-6-3-2 N. For the other two super alloys (NiCr and CoNiCr types alloys) tested in different conditions (annealed, work hardened and work hardened+age hardened) it was found that their behavior to corrosion was weak and close to the other reference stainless steel, 316L. Regarding the extraction a mixture of cations in relatively high concentrations was noted and therefore a cocktail effect was not excluded. The results obtained in the biological assays WST-1 and TNF-alpha were in correlation with the corrosion and extraction evaluation.

  13. Microstructural Characteristics and Oxidation Behavior of Low-Pressure Cold-Sprayed CoNiCrAlY Coatings

    NASA Astrophysics Data System (ADS)

    Zhang, Lin-wei; Lu, Lei; Wang, Lu; Ning, Xian-jin; Wang, Quan-sheng; Wang, Ri-xin

    2017-09-01

    CoNiCrAlY coatings were deposited by low-pressure cold spraying and subsequently heat-treated at 1050 °C for 4 h in a vacuum environment. The microstructural characteristics and oxidation behavior of CoNiCrAlY coatings were investigated. The as-sprayed coating exhibited low porosity and oxygen content. The high plastic deformation of the sprayed particles led to significant refinement of γ-matrix and dissolution of β-(Ni,Co)Al phase in the as-sprayed coating. After heat treatment, the single phase (γ) in the as-sprayed coating was converted into a γ/β microstructure, and a continuous single α-Al2O3 scale was formed on the coating surface. Vacuum heat treatment can postpone the formation of spinel oxides within 100 h. After being oxidized at 1050 °C for 400 h, the heat-treated coating exhibited better oxidation resistance than the as-sprayed coating. The reduced growth rate of the oxide scale and the suppression of the formation of spinel oxides can be attributed to the vacuum heat treatment, as well as the intrinsic microstructure of the cold-sprayed coating. Finally, the effects of the microstructural changes induced during the cold spraying process on the growth of the thermally grown oxide and the oxidation mechanisms of the CoNiCrAlY coatings were discussed.

  14. Microstructural Characteristics and Oxidation Behavior of Low-Pressure Cold-Sprayed CoNiCrAlY Coatings

    NASA Astrophysics Data System (ADS)

    Zhang, Lin-wei; Lu, Lei; Wang, Lu; Ning, Xian-jin; Wang, Quan-sheng; Wang, Ri-xin

    2017-10-01

    CoNiCrAlY coatings were deposited by low-pressure cold spraying and subsequently heat-treated at 1050 °C for 4 h in a vacuum environment. The microstructural characteristics and oxidation behavior of CoNiCrAlY coatings were investigated. The as-sprayed coating exhibited low porosity and oxygen content. The high plastic deformation of the sprayed particles led to significant refinement of γ-matrix and dissolution of β-(Ni,Co)Al phase in the as-sprayed coating. After heat treatment, the single phase (γ) in the as-sprayed coating was converted into a γ/β microstructure, and a continuous single α-Al2O3 scale was formed on the coating surface. Vacuum heat treatment can postpone the formation of spinel oxides within 100 h. After being oxidized at 1050 °C for 400 h, the heat-treated coating exhibited better oxidation resistance than the as-sprayed coating. The reduced growth rate of the oxide scale and the suppression of the formation of spinel oxides can be attributed to the vacuum heat treatment, as well as the intrinsic microstructure of the cold-sprayed coating. Finally, the effects of the microstructural changes induced during the cold spraying process on the growth of the thermally grown oxide and the oxidation mechanisms of the CoNiCrAlY coatings were discussed.

  15. Developments of the Physical and Electrical Properties of NiCr and NiCrSi Single-Layer and Bi-Layer Nano-Scale Thin-Film Resistors

    PubMed Central

    Cheng, Huan-Yi; Chen, Ying-Chung; Li, Chi-Lun; Li, Pei-Jou; Houng, Mau-Phon; Yang, Cheng-Fu

    2016-01-01

    In this study, commercial-grade NiCr (80 wt % Ni, 20 wt % Cr) and NiCrSi (55 wt % Ni, 40 wt % Cr, 5 wt % Si) were used as targets and the sputtering method was used to deposit NiCr and NiCrSi thin films on Al2O3 and Si substrates at room temperature under different deposition time. X-ray diffraction patterns showed that the NiCr and NiCrSi thin films were amorphous phase, and the field-effect scanning electronic microscope observations showed that only nano-crystalline grains were revealed on the surfaces of the NiCr and NiCrSi thin films. The log (resistivity) values of the NiCr and NiCrSi thin-film resistors decreased approximately linearly as their thicknesses increased. We found that the value of temperature coefficient of resistance (TCR value) of the NiCr thin-film resistors was positive and that of the NiCrSi thin-film resistors was negative. To investigate these thin-film resistors with a low TCR value, we designed a novel bi-layer structure to fabricate the thin-film resistors via two different stacking methods. The bi-layer structures were created by depositing NiCr for 10 min as the upper (or lower) layer and depositing NiCrSi for 10, 30, or 60 min as the lower (or upper) layer. We aim to show that the stacking method had no apparent effect on the resistivity of the NiCr-NiCrSi bi-layer thin-film resistors but had large effect on the TCR value. PMID:28344296

  16. Developments of the Physical and Electrical Properties of NiCr and NiCrSi Single-Layer and Bi-Layer Nano-Scale Thin-Film Resistors.

    PubMed

    Cheng, Huan-Yi; Chen, Ying-Chung; Li, Chi-Lun; Li, Pei-Jou; Houng, Mau-Phon; Yang, Cheng-Fu

    2016-02-25

    In this study, commercial-grade NiCr (80 wt % Ni, 20 wt % Cr) and NiCrSi (55 wt % Ni, 40 wt % Cr, 5 wt % Si) were used as targets and the sputtering method was used to deposit NiCr and NiCrSi thin films on Al₂O₃ and Si substrates at room temperature under different deposition time. X-ray diffraction patterns showed that the NiCr and NiCrSi thin films were amorphous phase, and the field-effect scanning electronic microscope observations showed that only nano-crystalline grains were revealed on the surfaces of the NiCr and NiCrSi thin films. The log (resistivity) values of the NiCr and NiCrSi thin-film resistors decreased approximately linearly as their thicknesses increased. We found that the value of temperature coefficient of resistance (TCR value) of the NiCr thin-film resistors was positive and that of the NiCrSi thin-film resistors was negative. To investigate these thin-film resistors with a low TCR value, we designed a novel bi-layer structure to fabricate the thin-film resistors via two different stacking methods. The bi-layer structures were created by depositing NiCr for 10 min as the upper (or lower) layer and depositing NiCrSi for 10, 30, or 60 min as the lower (or upper) layer. We aim to show that the stacking method had no apparent effect on the resistivity of the NiCr-NiCrSi bi-layer thin-film resistors but had large effect on the TCR value.

  17. Cube-textured nickel and Ni alloy substrates for YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Nast, R.; Obst, B.; Goldacker, W.

    2002-08-01

    This paper deals with the texturing of nickel and NiCr, NiW and NiCrW alloys. Concurrently with measurements of the primary recrystallization kinetics, the recrystallization texture of these materials was investigated in dependence on the annealing temperature and time. An increase of the recrystallization temperature or time sharpens the texture due to grain growth, limited however by the occurrence of secondary recrystallization when a sample specific temperature is exceeded. The most favorable recrystallization temperature was found to correlate with the recrystallization kinetics, varying with the sample composition. The reduced stacking fault energy (SFE) in binary Ni alloys in comparison with pure Ni favors the formation of recrystallization twins {1 2 2}<2 1 2> . The effect of a ternary alloy on the SFE is not easy to predict. So we tried to find, experimentally, a ternary alloy with medium to high SFE to produce the cube texture.

  18. Emittance of TD-NiCr after simulated reentry

    NASA Technical Reports Server (NTRS)

    Clark, R. K.; Dicus, D. L.; Lisagor, W. B.

    1978-01-01

    The effects of simulated reentry heating on the emittance of TD-NiCr were investigated. Groups of specimens with three different preconditioning treatments were exposed to 6, 24, and 30 half-hour simulated reentry exposure cycles in a supersonic arc tunnel at each of three conditions intended to produce surface temperatures of 1255, 1365, and 1475 K. Emittance was determined at 1300 K on specimens which were preconditioned only and specimens after completion of reentry simulation exposure. Oxide morphology and chemistry were studied by scanning electron microscopy and X-ray diffraction analysis. A consistent relationship was established between oxide morphology and total normal emittance. Specimens with coarser textured oxides tended to have lower emittances than specimens with finer textured oxides.

  19. High performance alloy electroforming

    NASA Technical Reports Server (NTRS)

    Malone, G. A.; Winkelman, D. M.

    1989-01-01

    Electroformed copper and nickel are used in structural applications for advanced propellant combustion chambers. An improved process has been developed by Bell Aerospace Textron, Inc. wherein electroformed nickel-manganese alloy has demonstrated superior mechanical and thermal stability when compared to previously reported deposits from known nickel plating processes. Solution chemistry and parametric operating procedures are now established and material property data is established for deposition of thick, large complex shapes such as the Space Shuttle Main Engine. The critical operating variables are those governing the ratio of codeposited nickel and manganese. The deposition uniformity which in turn affects the manganese concentration distribution is affected by solution resistance and geometric effects as well as solution agitation. The manganese concentration in the deposit must be between 2000 and 3000 ppm for optimum physical properties to be realized. The study also includes data regarding deposition procedures for achieving excellent bond strength at an interface with copper, nickel-manganese or INCONEL 718. Applications for this electroformed material include fabrication of complex or re-entry shapes which would be difficult or impossible to form from high strength alloys such as INCONEL 718.

  20. Lightweight High-Temperature Thermal Insulation

    NASA Technical Reports Server (NTRS)

    Wagner, W. R.; Fasheh, J. I.

    1985-01-01

    Fine Ni/Cr fibers sintered into corrosion-resistant, fireproof batt. Possible applications include stoves, furnaces, safes, fire clothing, draperies in public buildings, wall firebreaks, airplane walls, and jetengine components. New insulation takes advantage of some of same properties of nickel/chromium alloy useful in heating elements in toasters, namely, corrosion and oxidation resistance even at high temperatures.

  1. Improvement of Ni-Cr-Mo coating performance by laser cladding combined re-melting

    NASA Astrophysics Data System (ADS)

    Wang, Qin-Ying; Bai, Shu-Lin; Zhang, Yang-Fei; Liu, Zong-De

    2014-07-01

    Although being an efficient technique to produce metallic alloy coating, laser cladding may leave original unmelted particles in the coating. Further treatment is thus necessary to improve the coating quality, and laser re-melting therefore becomes a potential method. In this study, Ni-Cr-Mo alloy coatings were prepared on Q235 steel substrate by laser cladding (coating N1) and then re-melted by laser (coating N2) with the same technic parameters. The initial defect evolution and its effect on hardness and corrosion resistance of coatings were studied. The results show that there are fewer and smaller defects in coating N2 than in coating N1, which is ascribbed to the disappearance and partial melting of Cr/Cr2O3 particles. The nearly unchanged hardness of coatings N1 and N2 is justified by both Vickers tests and nanoindentation combined theoretical calculation. Coating N2 with higher positive corrosion potential and lower corrosion current density exhibits better corrosion resistance than coating N1. Above results prove that laser re-melting can refine the microstructure and improve corrosion resistance of coatings to some degree.

  2. Shear Bond Strength of a Resin Cement to Different Alloys Subjected to Various Surface Treatments

    PubMed Central

    Tabari, Kasra; Jaberi Ansari, Zahra; Torabzadeh, Hassan; Kharrazi fard, Mohammad Javad

    2016-01-01

    Objectives: Micromechanical retention of resin cements to alloys is an important factor affecting the longevity of metal base restorations. This study aimed to compare the bond strength and etching pattern of a newly introduced experimental etchant gel namely Nano Met Etch with those of conventional surface treatment techniques for nickel-chrome (Ni-Cr) and high noble alloys. Materials and Methods: A total of 120 discs (8×10×15 mm) were cast with Ni-Cr (n=20), high noble BegoStar (n=50) and gold coin alloys (n=50). Their Surfaces were ground with abrasive papers. Ni-Cr specimens received sandblasting and etching. High noble alloy specimens (BegoStar and gold coin) received sandblasting, sandblasting-alloy primer, etching, etch-alloy primer and alloy primer alone. Cylindrical specimens of Panavia were bonded to surfaces using Tygon tubes. Specimens were subjected to micro-shear bond strength testing after storing at 37°C for 24 hours. Results: In gold coin group, the highest bond strength was achieved after sandblasting (25.82±1.37MPa, P<0.001) and etching+alloy primer (26.60 ± 5.47 MPa, P<0.01). The lowest bond strength belonged to sandblasting+alloy primer (17.79±2.96MPa, P<0.01). In BegoStar group, the highest bond strength was obtained in the sandblasted group (38.40±3.29MPa, P<0.001) while the lowest bond strength was detected in the sandblast+ alloy primer group (15.38±2.92MPa, P<0.001). For the Ni-Cr alloy, bond strength in the etched group (20.79±2.01MPa) was higher than that in the sandblasted group (18.25±1.82MPa) (P<0.01). Conclusions: For the Ni-Cr alloy, etching was more efficient than sandblasting but for the high noble alloys, higher Au content increased the efficacy of etching. PMID:27536326

  3. High strength ferritic alloy

    DOEpatents

    Hagel, William C.; Smidt, Frederick A.; Korenko, Michael K.

    1977-01-01

    A high-strength ferritic alloy useful for fast reactor duct and cladding applications where an iron base contains from about 9% to about 13% by weight chromium, from about 4% to about 8% by weight molybdenum, from about 0.2% to about 0.8% by weight niobium, from about 0.1% to about 0.3% by weight vanadium, from about 0.2% to about 0.8% by weight silicon, from about 0.2% to about 0.8% by weight manganese, a maximum of about 0.05% by weight nitrogen, a maximum of about 0.02% by weight sulfur, a maximum of about 0.02% by weight phosphorous, and from about 0.04% to about 0.12% by weight carbon.

  4. Hot Corrosion Studies of Detonation-Gun-Sprayed NiCrAlY + 0.4 wt.% CeO2 Coated Superalloys in Molten Salt Environment

    NASA Astrophysics Data System (ADS)

    Kamal, Subhash; Jayaganthan, R.; Prakash, Satya

    2011-08-01

    Rare earth oxide (CeO2) has been incorporated in NiCrAlY alloy and hot corrosion resistance of detonation-gun-sprayed NiCrAlY + 0.4 wt.% CeO2 coatings on superalloys, namely, superni 75, superni 718, and superfer 800H in molten 40% Na2SO4-60% V2O5 salt environment were investigated at 900 °C for 100 cycles. The coatings exhibited characteristic splat globular dendritic structure with diameter similar to the original powder particles. The weight change technique was used to establish corrosion kinetics. X-ray diffraction (XRD), field emission scanning electron microscopy/energy-dispersive analysis (FE-SEM/EDAX), and x-ray mapping techniques were used to analyze the corrosion products. Coated superfer 800H alloy showed the highest corrosion resistance among the examined superalloys. CeO2 was found to be distributed in the coating along the splat boundaries, whereas Al streaks distributed non-uniformly. The main phases observed for the coated superalloys are oxides of Ni, Cr, Al, and spinels, which are suggested to be responsible for developing corrosion resistance.

  5. Effect of Oxyacetylene Flame Remelting on Wear Behaviour of Supersonic Air-Plasma Sprayed NiCrBSi/h-BN Composite Coatings

    NASA Astrophysics Data System (ADS)

    Zhang, N. N.; Lin, D. Y.; He, B.; Zhang, G. W.; Zhang, Y.; Li, D. Y.

    NiCrBSi alloy coatings are widely used in wear and corrosion protection at higher temperature. As a primary hard phase forming element, B element can effectively improve the coating hardness. In this study, the low coefficient of friction of BN with three ratios (10%, 20%, and 30%) was added in order to reduce the wear rate and provide additional B element. The NiCrBSi/h-BN composite coatings were successfully prepared on a cast-iron substrate using supersonic air-plasma spray technology. The phase constitution, microstructure characterization, and microhardness of the coatings before and after oxyacetylene flame remelting were investigated by means of scanning electron microscope (SEM), X-ray diffraction, and energy dispersive analysis of X-ray techniques, respectively. The wear resistance of composite coatings was also tested in this paper. It was found that the microstructure was well refined by remelting treatment and this was beneficial for the adherence between the coating and the substrate, which was nearly 33MPa. The wear resistance of the NiCrBSi alloy coating was also improved with the increasing component of h-BN in remelted samples. When the h-BN content reached 30%, the friction coefficient decreased to 0.38 for the remelted coating. The effect of the remelting process on the anti-abrasive property and extension of the material’s wear life was quite important.

  6. Nickel-based Gadolinium Alloy for Neutron Adsorption Application in Ram Packages

    SciTech Connect

    Gregg Wachs; James Sterbentz; William Hurt; P. E. McConnell; C. V. Robino; F. Tovesson; T. S. Hill

    2007-10-01

    Neutron transmission experiments were performed on samples of an advanced nickel-chromium-molybdenum-gadolinium (Ni-Cr-Mo-Gd) neutron absorber alloy and chromium-nickel (Cr-Ni) stainless steel, modified by the addition of boron. The primary purpose of the experiments was to demonstrate the thermal neutron absorbing capability of the materials at specific gadolinium and boron dopant levels. The Ni-Cr-Mo-Gd alloy is envisioned to be deployed for criticality control of highly enriched U.S. Department of Energy (DOE)-owned spent nuclear fuel (SNF). For these transmission experiments, test samples were fabricated with 0.0, 1.58 and 2.1 wt% natural gadolinium dispersed in a Ni-Cr-Mo base alloy and 1.16 wt% boron in stainless steel. The transmission experiments were successfully carried out at the Los Alamos Neutron Science Center (LANSCE). Measured data from the neutron transmission experiments were compared to calculated results derived from a simple exponential transmission formula using total neutron cross sections. Excellent agreement between the measured and calculated results demonstrated the expected strong thermal absorption capability of the gadolinium and boron elements and in addition, verified the measured elemental composition of the Ni-Cr-Mo-Gd alloy and borated stainless steel test samples. The good agreement also indirectly confirmed that the size and distribution of the gadolinium in both the hot-top (as-cast) and Ni-Cr-Mo-Gd converted to plate was not a discriminator related to neutron absorption. Moreover, the Evaluated Nuclear Data File (ENDF VII) total neutron cross section data were accurate.

  7. State-of-technology for joining TD-NiCr sheet

    NASA Technical Reports Server (NTRS)

    Holko, K. H.; Moore, T. J.; Gyorgak, C. A.

    1972-01-01

    At the current state-of-technology there are many joining processes that can be used to make sound welds in TD-NiCr sheet. Some of these that are described in this report are electron beam welding, gas-tungsten arc welding, diffusion welding, resistance spot welding, resistance seam welding, and brazing. The strengths of the welds made by the various processes show considerable variation, especially at elevated temperatures. Most of the fusion welding processes tend to give weak welds at elevated temperatures (with the exception of fusion-type resistance spotwelds). However, solid-state welds have been made with parent metal properties. The process used for a specific application will be dictated by the specific joint requirements. In highly stressed joints at elevated temperatures, one of the solid-state processes, such as DFW, RSW (solid-state or fusion), and RSEW, offer the most promise.

  8. Auger electron spectroscopy study of interdiffusion, oxidation and segregation during thermal treatment of NiCr/CuNi(Mn)/NiCr thin films

    NASA Astrophysics Data System (ADS)

    Baunack, S.; Brückner, W.; Pitschke, W.; Thomas, J.

    1999-04-01

    The effect of annealing on sputter deposited thin-films NiCr/CuNi(Mn)/NiCr is studied by Auger electron depth profiling. The samples were annealed to maximum temperatures of 300°C to 550°C and investigated at ambient temperature. Auger transitions of Cu and Ni are separated by target factor analysis, principal component analysis and linear least squares fit to standard spectra. For the CuNi(Mn) layer in the as-received state AES results shows a Cu depletion caused by bombardment induced segregation. After annealing the measured Cu concentration has increased due to Ni diffusion to the interfaces. The NiCr layer is degraded with increasing annealing temperature due to formation of a chromium oxide and diffusion of Ni from the CuNi(Mn) layer. A sequence with nominal compositions near Cr 2Ni, CrNi and CrNi 2 is found. At the NiCr/CuNi(Mn) interface an interdiffusion zone phase Ni 0.6Cr 0.2Cu 0.2 is formed.

  9. Passive Corrosion Behavior of Alloy 22

    SciTech Connect

    Rebak, R B; Payer, J H

    2006-01-10

    Alloy 22 (N06022) was designed to stand the most aggressive industrial applications, including both reducing and oxidizing acids. Even in the most aggressive environments, if the temperature is lower than 150 F (66 C) Alloy 22 would remain in the passive state having particularly low corrosion rates. In multi-ionic solutions that may simulate the behavior of concentrated ground water, even at near boiling temperatures, the corrosion rate of Alloy 22 is only a few nanometers per year because the alloy is in the complete passive state. The corrosion rate of passive Alloy 22 decreases as the time increases. Immersion corrosion testing also show that the newer generation of Ni-Cr-Mo alloys may offer a better corrosion resistance than Alloy 22 only in some highly aggressive conditions such as in hot acids.

  10. Passive Corrosion Behavior of Alloy 22

    SciTech Connect

    R.B. Rebak; J.H. Payer

    2006-01-20

    Alloy 22 (NO6022) was designed to stand the most aggressive industrial applications, including both reducing and oxidizing acids. Even in the most aggressive environments, if the temperature is lower than 150 F (66 C) Alloy 22 would remain in the passive state having particularly low corrosion rates. In multi-ionic solutions that may simulate the behavior of concentrated ground water, even at near boiling temperatures, the corrosion rate of Alloy 22 is only a few nano-meters per year because the alloy is in the complete passive state. The corrosion rate of passive Alloy 22 decreases as the time increases. Immersion corrosion testing also show that the newer generation of Ni-Cr-Mo alloys may offer a better corrosion resistance than Alloy 22 only in some highly aggressive conditions such as in hot acids.

  11. Mechanically Alloyed High Entropy Composite

    NASA Astrophysics Data System (ADS)

    Popescu, G.; Adrian, M. M.; Csaki, I.; Popescu, C. A.; Mitrică, D.; Vasile, S.; Carcea, I.

    2016-08-01

    In the last years high entropy alloys have been investigated due to their high hardness, high temperature stability and unusual properties that make these alloys to have significant interest. In comparison with traditional alloys that are based on two or three major elements, this new generation alloys consists at least of 5 principal elements, with the concentration between 5 and 35 at.%. The present paper reports synthesis of high entropy alloys (HEA) and high entropy composites (HEC) synthesized by mechanical alloying (MA). The equiatomic AlCrFeNiMn matrix was used for creating the HEA matrix, starting from elemental powders and as reinforcing material for composites was used pure graphite. The mechanical alloying process was carried out at different duration, in a high energy planetary ball mill, under argon atmosphere. The elemental powders alloying began after '5 hours of milling and was complete after 40 hours. The mechanical alloyed matrix and composite was pressed and heat treated under argon protection. The elemental powers were investigated for physical - technological properties, and by X-ray diffraction and scanning electron microscopy. Phase pressing operation was realized with a hydraulic press and the applied pressure was progressive. The sintering process was carried out at 850°C for 2 h. The X-ray diffraction revealed that the MA process resulted in solid solutions formation and also revealed body- centred cubic (BCC) and face-centred cubic (FCC) structures with average grain size around 40 nm. In addition, nanoscale particles were highlighted by scanning electron microscopy, as well as the homogeneity of the chemical composition of the matrix and composite that was confirmed by EDX microanalysis. It was noted that HEA matrix and HEA composites were processed with a high degree of compaction and with a quite large capacity of mixed powder densification (around 70%).

  12. Structures and Properties of C-Doped NiCr Thin Film Deposited by Closed-Field Unbalanced Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Lai, Lifei; Wang, Jinxia; Wang, Hongtao; Bao, Mingdong

    2017-01-01

    The structures and properties of C-doped NiCr thin film as embedded thin film resistor (ETFR) materials were studied by closed-field, unbalanced magnetron sputtering method. The C-doped NiCr (NiCrC1) thin film had more stable electrical performance, better corrosion resistance, and higher hardness than NiCr thin film. The temperature coefficient of resistance (TCR) of NiCrC1 thin film deposited at room temperature (from 19.73 ppm/K to 173.7 ppm/K) was lower than that of NiCr thin film (from 157.8 ppm/K to 378.9 ppm/K), and the sheet resistor (154.25 Ω/Sq) was higher than that of NiCr thin film (62.84 Ω/Sq). The preferred orientations of C-doped NiCr thin film was Ni (111), while that of NiCr thin film was Ni (011). The carbon-doped NiCr thin film can reduce the defects and stress and change the preferred orientations. The dominant carbon in C-doped NiCr thin film had a graphite-like structure.

  13. Manufacture and engine test of advanced oxide dispersion strengthened alloy turbine vanes. [for space shuttle thermal protection

    NASA Technical Reports Server (NTRS)

    Bailey, P. G.

    1977-01-01

    Oxide-Dispersion-strengthened (ODS) Ni-Cr-Al alloy systems were exploited for turbine engine vanes which would be used for the space shuttle thermal protection system. Available commercial and developmental advanced ODS alloys were evaluated, and three were selected based on established vane property goals and manufacturing criteria. The selected alloys were evaluated in an engine test. Candidate alloys were screened by strength, thermal fatigue resistance, oxidation and sulfidation resistance. The Ni-16Cr (3 to 5)Al-ThO2 system was identified as having attractive high temperature oxidation resistance. Subsequent work also indicated exceptional sulfidation resistance for these alloys.

  14. Microstructure of Au-ion irradiated 316L and FeNiCr austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Jublot-Leclerc, S.; Li, X.; Legras, L.; Lescoat, M.-L.; Fortuna, F.; Gentils, A.

    2016-11-01

    Thin foils of 316L were irradiated in situ in a Transmission Electron Microscope with 4 MeV Au ions at 450 °C and 550 °C. Similar irradiations were performed at 450 °C in FeNiCr. The void and dislocation microstructure of 316L is found to depend strongly on temperature. At 450 °C, a dense network of dislocation lines is observed in situ to grow from black dot defects by absorption of other black dots and interstitial clusters whilst no Frank loops are detected. At 550 °C, no such network is observed but large Frank loops and perfect loops whose sudden appearance is concomitant with a strong increase in void density as a result of a strong coupling between voids and dislocations. Moreover, differences in both alloys microstructure show the major role played by the minor constituents of 316L, increasing the stacking fault formation energy, and possibly leading to significant differences in swelling behaviour.

  15. Stress, resistance, and phase transitions in NiCr(60 wt %) thin films

    NASA Astrophysics Data System (ADS)

    Brückner, W.; Pitschke, W.; Thomas, J.; Leitner, G.

    2000-03-01

    The evolution in both stress and resistance has been investigated on sputtered NiCr(60 wt %) resistive films during annealing (temperature cycles to maximum 700 °C). Aiming at the correlation of stress, resistance, and microstructure, samples from measurements to various maximum temperatures were analyzed by x-ray diffraction and transmission electron microscopy including microanalysis. A series of metastable phases was found with increasing temperature: the as-deposited amorphous phase a, the supersaturated body-centered-cubic (bcc) solid solution αss(Cr) (400 °C), and the tetragonal σ phase (500 °C). This was followed by the equilibrium two-phase alloy bcc α(Cr) plus face-centered-cubic γ(Ni) (600 °C). The phase transitions, characterized by differential scanning calorimetry, were found to be exothermic. The transition a→αss(Cr) results in a distinct tensile-stress component due to material densification. The resistivity is sharply decreasing and the temperature coefficient of resistance is changing from negative to positive values during the a→αss(Cr) transition.

  16. Oxidation behaviors of porous Haynes 214 alloy at high temperatures

    SciTech Connect

    Wang, Yan; Liu, Yong; Tang, Huiping; Li, Weijie

    2015-09-15

    The oxidation behaviors of porous Haynes 214 alloy at temperatures from 850 to 1000 °C were investigated. The porous alloys before and after the oxidation were examined by optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) analyses, and X-ray photoelectron spectroscopy (XPS). The oxidation kinetics of the porous alloy approximately follows a parabolic rate law and exhibits two stages controlled by different oxidation courses. Complex oxide scales composed of Cr{sub 2}O{sub 3}, NiCr{sub 2}O{sub 4} and Al{sub 2}O{sub 3} are formed on the oxidized porous alloys, and the formation of Cr{sub 2}O{sub 3} on its outer layer is promoted with the oxidation proceeding. The rough surface as well as the micropores in the microstructures of the porous alloy caused by the manufacturing process provides fast diffusion paths for oxygen so as to affect the formation of the oxide layers. Both the maximum pore size and the permeability of the porous alloys decrease with the increase of oxidation temperature and exposure time, which may limit its applications. - Highlights: • Two-stage oxidation kinetics controlled by different oxidation courses is showed. • Oxide scale mainly consists of Cr{sub 2}O{sub 3}, NiCr{sub 2}O{sub 4} and Al{sub 2}O{sub 3}. • Rough surface and micropores lead to the formation of uneven oxide structure. • Content of Cr{sub 2}O{sub 3} in the outer layer of the scale increases with time at 1000 °C. • Maximum pore size and permeability decrease with increasing temperature and time.

  17. The effect of mucine, IgA, urea, and lysozyme on the corrosion behavior of various non-precious dental alloys and pure titanium in artificial saliva.

    PubMed

    Bilhan, H; Bilgin, T; Cakir, A F; Yuksel, B; Von Fraunhofer, J A

    2007-11-01

    The corrosion of dental alloys has biological, functional, and aesthetic consequences. Various studies have shown that protein solutions can inhibit the corrosion of alloys. This study is planned to determine the relationship of organic constituents of saliva and the corrosion of dental alloys. The organic constituents are IgA, mucine, urea, and lysozyme which are encountered in the highest amounts in saliva and the dental materials are titanium (Ti), Co-Cr-Mo and Ni-Cr-Mo alloys, and dental amalgam, the most often used metallic components in dentistry. In particular, the interactions between the commonest salivary proteins, IgA, mucine, urea and lysozyme, and Ti, Co-Cr-Mo, Ni-Cr-Mo and dental amalgam were investigated. Each alloy was evaluated by cyclic polarization in each medium. The general anodic and cathodic behavior during forward and reverse cycles, the corrosion and passivation current densities (muA/cm2 ), and the corrosion and the pitting potentials (mV) were determined. The results have shown that Ni-Cr-Mo and dental amalgam alloys are highly susceptible to corrosion in all the investigated media. The Co-Cr-Mo alloy has shown high passive current densities in the solution of mucine and lysozyme in artificial saliva. Titanium instead, has shown a high resistance to corrosion and a stable passive behavior in all media, especially in a solution of mucine and IgA in synthetic saliva. Mucine and IgA, as well as urea and lysozyme, appeared to enhance the formation of a passive film layer on the Ti metal surface, thus inhibiting the corrosion. Based on the study findings, and especially considering the problem of nickel allergy and toxicity of mercury released from dental amalgam, the use of Co-Cr-Mo alloys and Ti to Ni-Cr-Mo alloys is recommended and alternatives to dental amalgam should be sought for patients with impaired salivary flow.

  18. Manufacturing of High Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Jablonski, Paul D.; Licavoli, Joseph J.; Gao, Michael C.; Hawk, Jeffrey A.

    2015-07-01

    High entropy alloys (HEAs) have generated interest in recent years due to their unique positioning within the alloy world. By incorporating a number of elements in high proportion they have high configurational entropy, and thus they hold the promise of interesting and useful properties such as enhanced strength and phase stability. The present study investigates the microstructure of two single-phase face-centered cubic (FCC) HEAs, CoCrFeNi and CoCrFeNiMn, with special attention given to melting, homogenization and thermo-mechanical processing. Large-scale ingots were made by vacuum induction melting to avoid the extrinsic factors inherent in small-scale laboratory button samples. A computationally based homogenization heat treatment was applied to both alloys in order to eliminate segregation due to normal ingot solidification. The alloys fabricated well, with typical thermo-mechanical processing parameters being employed.

  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. Fracture resistances of zirconia, cast Ni-Cr, and fiber-glass composite posts under all-ceramic crowns in endodontically treated premolars.

    PubMed

    Habibzadeh, Sareh; Rajati, Hamid Reza; Hajmiragha, Habib; Esmailzadeh, Shima; Kharazifard, Mohamadjavad

    2017-06-01

    The aim of the present study was to evaluate the fracture resistances of zirconia, cast nickel-chromium alloy (Ni-Cr), and fiber-composite post systems under all-ceramic crowns in endodontically treated mandibular first premolars. A total of 36 extracted human mandibular premolars were selected, subjected to standard endodontic treatment, and divided into three groups (n=12) as follows: cast Ni-Cr post-and-core, one-piece custom-milled zirconia post-and-core, and prefabricated fiber-glass post with composite resin core. Each specimen had an all-ceramic crown with zirconia coping and was then loaded to failure using a universal testing machine at a cross-head speed of 0.5 mm/min, at an angle of 45 degrees to the long axis of the roots. Fracture resistance and modes of failure were analyzed. The significance of the results was assessed using analysis of variance (ANOVA) and Tukey honest significance difference (HSD) tests (α=.05). Fiber-glass posts with composite cores showed the highest fracture resistance values (915.70±323 N), and the zirconia post system showed the lowest resistance (435.34±220 N). The corresponding mean value for the Ni-Cr casting post and cores was reported as 780.59±270 N. The differences among the groups were statistically significant (P<.05) for the zirconia group, as tested by ANOVA and Tukey HSD tests. The fracture resistance of zirconia post-and-core systems was found to be significantly lower than those of fiberglass and cast Ni-Cr post systems. Moreover, catastrophic and non-restorable fractures were more prevalent in teeth restored by zirconia posts.

  1. Fracture resistances of zirconia, cast Ni-Cr, and fiber-glass composite posts under all-ceramic crowns in endodontically treated premolars

    PubMed Central

    Rajati, Hamid Reza; Hajmiragha, Habib; Esmailzadeh, Shima; Kharazifard, Mohamadjavad

    2017-01-01

    PURPOSE The aim of the present study was to evaluate the fracture resistances of zirconia, cast nickel-chromium alloy (Ni-Cr), and fiber-composite post systems under all-ceramic crowns in endodontically treated mandibular first premolars. MATERIALS AND METHODS A total of 36 extracted human mandibular premolars were selected, subjected to standard endodontic treatment, and divided into three groups (n=12) as follows: cast Ni-Cr post-and-core, one-piece custom-milled zirconia post-and-core, and prefabricated fiber-glass post with composite resin core. Each specimen had an all-ceramic crown with zirconia coping and was then loaded to failure using a universal testing machine at a cross-head speed of 0.5 mm/min, at an angle of 45 degrees to the long axis of the roots. Fracture resistance and modes of failure were analyzed. The significance of the results was assessed using analysis of variance (ANOVA) and Tukey honest significance difference (HSD) tests (α=.05). RESULTS Fiber-glass posts with composite cores showed the highest fracture resistance values (915.70±323 N), and the zirconia post system showed the lowest resistance (435.34±220 N). The corresponding mean value for the Ni-Cr casting post and cores was reported as 780.59±270 N. The differences among the groups were statistically significant (P<.05) for the zirconia group, as tested by ANOVA and Tukey HSD tests. CONCLUSION The fracture resistance of zirconia post-and-core systems was found to be significantly lower than those of fiberglass and cast Ni-Cr post systems. Moreover, catastrophic and non-restorable fractures were more prevalent in teeth restored by zirconia posts. PMID:28680547

  2. Laser cladding for high-temperature self-lubricating wear-resistant composite coatings on γ-TiAl intermetallic alloy Ti-48Al-2Cr-2Nb

    NASA Astrophysics Data System (ADS)

    Liu, X. B.; Wang, C. M.; Yu, L. G.; Wang, Hua Ming

    2000-02-01

    High-temperature self-lubricating wear-resistant metal matrix composite coatings are fabricated on substrate of a (gamma) - TiAl intermetallic alloy Ti-48Al-2Cr-2Nb by laser cladding. The hybrid (gamma) -NiCr metal matrix composite coating is mainly reinforced by rapidly solidified wear-resistant phase of hyper-eutectic M7C3 and self-lubricating particles of Ag and CaF2 or CaAgF4. Microstructure and hardness within the whole laser clad composite coating is homogeneous and the bonding to the substrate is purely metallurgical. Both hardness and dry sliding wear resistance of the (gamma) -TiAl intermetallic alloy are significantly enhanced after laser cladding treatment.

  3. Effect of recrystallization annealing on the formation of a perfect cube texture in FCC nickel alloys

    NASA Astrophysics Data System (ADS)

    Rodionov, D. P.; Gervas'eva, I. V.; Khlebnikova, Yu. V.; Kazantsev, V. A.; Vinogradova, N. I.; Sazonova, V. A.

    2011-06-01

    Based on the data of X-ray diffraction, dilatometry, transmission electron microscopy, and electron backscatter diffraction, the optimum regimes of heat treatment of cold-rolled (to 98.5-99%) tapes made of binary Ni-W, Ni-Cr, Ni-Fe and ternary tungsten-containing Ni-Pd-W and Ni-Cr-W alloys that are widely utilized in the world practice for the fabrication of high-temperature superconducting cables of the second generation, which make it possible to obtain a perfect cube texture. In all five alloys, the spreed of the texture upon slow heating and two-step annealing decreases by 0.2°-1.5° around the RD and by 0.1°-0.6° around the RD in comparison with the single-stage high-temperature annealing.

  4. Effect of ion plating TiN on the oxidation of sputtered NiCrAlY-coated Ti{sub 3}Al-Nb in air at 850-950 C

    SciTech Connect

    Rizzo, F.C.; Zeng, C. |; Wu, W.

    1998-08-01

    A single sputtered NiCrAlY coating and a complex coating of inner ion-plated TiN and outer sputtered NiCrAlY were prepared on the intermetallic compound Ti{sub 3}Al-Nb. Their oxidation behavior was examined at 850, 900, and 950 C in air by thermal gravimetry combined with XRD, SEM, and EDAX. The results showed that Ti{sub 3}Al-Nb followed approximately parabolic oxidation, forming an outer thin Al{sub 2}O{sub 3}-rich scale and an inner TiO{sub 2}-rich layer doped with Nb at the three temperatures. The TiO{sub 2}-rich layer doped with Nb dominated the oxidation reaction. The single NiCrAlY coating did not follow parabolic oxidation exactly at 850 and 950 C, but oxidized approximately in a parabolic manner, because the instantaneous parabolic constants changed slightly with time. Besides the Al{sub 2}O{sub 3} scale, TiO{sub 2} formed from the coating surface at the coating-substrate interface. The deterioration of the coating accelerated with increasing temperature. The NiCrAlY-TiN coating showed two-stage parabolic oxidation at 850 and 900 C, and an approximate parabolic oxidation at 950 C. The TiN layer was effective as a barrier to inhibit coating-alloy interdiffusion.

  5. [Effect of laser irradiation power on the mechanical properties of Co-Cr and Ni-Cr laser-welded joints.].

    PubMed

    Zhang, Jian-zhong; Huang, Qing-feng; Jiang, Wei-dong; Li, Quan; Yu, Jin-xing

    2004-10-01

    To investigate the effect of different irradiation power on the mechanical properties of laser-welded joints. The standard tensile test and three-point bending test rods made from Co-Cr and Ni-Cr alloy were laser-welded with different irradiation powers. Then the tensile rods were tested for the ultimate tensile strength (UTS), and the bending rods for the ultimate bending strength (UBS). The tensile fracture surface was examined by scanning electron microscopy (SEM). Metallurgical analysis and microhardness test were also performed on polished longitudinal sectioned samples. For Co-Cr alloy, greater irradiation power resulted in greater UTS, minor UBS. For Ni-Cr alloy, there was no significant difference of UTS and UBS between the four groups. SEM and metallurgical examination showed that the welded zone exhibited more gas pores and cracks as the irradiation power increased. Microhardness test showed that hardness increased toward the center of the welded zone and as the irradiation power increased, the range of hardness increased was expanded. The optimal laser irradiation power was the key to achieved superior mechanical properties joints.

  6. Analysis of solidification microstructures in Fe-Ni-Cr single-crystal welds

    NASA Astrophysics Data System (ADS)

    Rappaz, M.; David, S. A.; Vitek, J. M.; Boatner, L. A.

    1990-06-01

    A geometric analysis technique for the evaluation of the microstructures in autogenous single-crystal electron beam welds has been previously developed. In the present work, these analytical methods are further extended, and a general procedure for predicting the solidification microstructure of single-crystal welds with any arbitrary orientation is established. Examples of this general analysis are given for several welding orientations. It is shown that a nonsymmetric cell structure is expected in transverse micrographs for most welding geometries. The development of steady-state conditions in the weld pool is also examined in terms of the weld pool size, its shape (as revealed by the dendritic growth pattern), and the size of the dendritic cells. It is found that steady state is established within a few millimeters of the beginning of the weld. Furthermore, steady state is achieved faster in welds made at higher welding speeds. A general analysis of the three-dimensional (3-D) weld pool shape based on the dendritic structure as revealed in the two-dimensional (2-D) transverse micrographs is also developed. It is shown that in combination with information on the preferred growth direction as a function of the solidification front orientation, the entire dendritic growth pattern in single-crystal welds can be predicted. A comparison with the actual weld micrographs shows a reasonable agreement between the theory and experiment. Finally, the theoretical analysis of the dendrite tip radius is extended from binary systems to include the case of ternary systems. The theoretical dendrite trunk spacing in a ternary Fe-Ni-Cr alloy is calculated from the dendrite tip radius and is compared with the experimental values for several weld conditions. Good agreement between experiment and theory is found.

  7. High strength, tough alloy steel

    DOEpatents

    Thomas, Gareth; Rao, Bangaru V. N.

    1979-01-01

    A high strength, tough alloy steel is formed by heating the steel to a temperature in the austenite range (1000.degree.-1100.degree. C.) to form a homogeneous austenite phase and then cooling the steel to form a microstructure of uniformly dispersed dislocated martensite separated by continuous thin boundary films of stabilized retained austenite. The steel includes 0.2-0.35 weight % carbon, at least 1% and preferably 3-4.5% chromium, and at least one other substitutional alloying element, preferably manganese or nickel. The austenite film is stable to subsequent heat treatment as by tempering (below 300.degree. C.) and reforms to a stable film after austenite grain refinement.

  8. Microstructures and superplastic behavior of eutectic Fe-C and Ni-Cr white cast irons produced by rapid solidification

    NASA Astrophysics Data System (ADS)

    Kum, D. W.; Frommeyer, G.; Grant, N. J.; Sherby, O. D.

    1987-10-01

    Superplastic behavior of two commercial grade white cast irons, eutectic Fe-C and Ni-Cr white cast irons, was investigated at intermediate temperatures (650 to 750 °C). For this purpose, rapidly solidified powders of the cast irons were fully consolidated by compaction and rolling at about 650 °C. The volume fractions of cementite in the eutectic cast iron and in the Ni-Cr cast iron were 64 pct and 51 pct, respectively, and both cast irons consisted of fine equiaxed grains of cementite (1 to 2 μm) and ferrite (0.5 to 2 μm). The cast iron compacts exhibited high strain-rate sensitivity (strain-rate-sensitivity exponent of 0.35 to 0.46) and high tensile ductility (total elongation of 150 pct to 210 pct) at strain rates of 10-4 to 10-3 s-1 and at 650 °C to 750 °C. Microstructure evaluations were made by TEM, SEM, and optical microscopy methods. The equiaxed grains in the as-compacted samples remained unchanged even after large tensile deformation. It is concluded that grain boundary sliding ( e.g., along cementite grain boundaries in the case of the eutectic cast iron) is the principal mode of plastic deformation in both cast irons during superplastic testing conditions.

  9. Picosecond laser patterning of NiCr thin film strain gages

    NASA Astrophysics Data System (ADS)

    Suttmann, Oliver; Gosselin, Michael; Klug, Ulrich; Kling, Rainer

    2010-02-01

    This paper presents results of ablation experiments of NiCr layers with thicknesses ranging from 23nm to 246nm on Al2O3 substrates. Investigated parameters are fluence, number of pulses, film thickness and substrate roughness. The influence of the parameters on the removal threshold is analyzed in order to identify stable processing parameters. Patterned NiCr thin films as an essential component for the measurement of mechanical stress are required for the development of sputtered thin film strain gages. With this new approach strain sensors will be resistant against creeping or swelling through changing ambient conditions unlike conventional strain gages.

  10. Alloys developed for high temperature applications

    NASA Astrophysics Data System (ADS)

    Basuki, Eddy Agus; Prajitno, Djoko Hadi; Muhammad, Fadhli

    2017-01-01

    Alloys used for high temperatures applications require combinations of mechanical strength, microstructural stability and corrosion/oxidation resistance. Nickel base superalloys have been traditionally the prime materials utilized for hot section components of aircraft turbine engines. Nevertheless, due to their limited melting temperatures, alloys based on intermetallic compounds, such as TiAl base alloys, have emerged as high temperature materials and intensively developed with the main aim to replace nickel based superalloys. For applications in steam power plants operated at lower temperatures, ferritic high temperature alloys still attract high attention, and therefore, development of these alloys is in progress. This paper highlights the important metallurgical parameters of high temperature alloys and describes few efforts in the development of Fe-Ni-Al based alloys containing B2-(Fe,Ni)Al precipitates, oxide dispersion strengthening (ODS) ferritic steels and titanium aluminide based alloys include important protection system of aluminide coatings.

  11. Tribological Characterization of Plasma-Sprayed CoNiCrAlY-BN Abradable Coatings

    NASA Astrophysics Data System (ADS)

    Irissou, E.; Dadouche, A.; Lima, R. S.

    2014-01-01

    The processing conditions, microstructural and tribological characterizations of plasma-sprayed CoNiCrAlY-BN high temperature abradable coatings are reported in this manuscript. Plasma spray torch parameters were varied to produce a set of abradable coatings exhibiting a broad range of porosity levels (34-62%) and superficial Rockwell hardness values (0-78 HR15Y). Abradability tests have been performed using an abradable-seal test rig, capable of simulating operational wear at different rotor speeds and seal incursion rates (SIRs). These tests allowed determining the rubbing forces and quantifying the blade and seal wear characteristics for slow and fast SIRs. Erosion wear performance and ASTM C633 coating adhesion strength test results are also reported. For optimal abradability performance, it is shown that coating hardness needs to be lower than 70 and 50 HR15Y for slow and fast blade incursion rate conditions, respectively. It is shown that the erosion wear performance, as well as, the coating cohesive strength is a function of the coating hardness. The current results allow defining the coating specifications in terms of hardness and porosity for targeted applications.

  12. Residual Stresses in a NiCrY-Coated Powder Metallurgy Disk Superalloy

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Rogers, Richard B.; Nesbitt, James A.; Puleo, Bernadette J.; Miller, Robert A.; Telesman, Ignacy; Draper, Susan L.; Locci, Ivan E.

    2017-01-01

    Protective ductile coatings will be necessary to mitigate oxidation and corrosion attack on superalloy disks exposed to increasing operating temperatures in some turbine engine environments. However, such coatings must be resistant to harmful surface cracking during service. The objective of this study was to investigate how residual stresses evolve in such coatings. Cylindrical gage fatigue specimens of powder metallurgy-processed disk superalloy LSHR were coated with a NiCrY coating, shot peened, and then subjected to fatigue in air at room and high temperatures. The effects of shot peening and fatigue cycling on average residual stresses and other aspects of the coating were assessed. Shot peening did induce beneficial compressive residual stresses in the coating and substrate. However, these stresses became more tensile in the coating with subsequent heating and contributed to cracking of the coating in long intervals of cycling at 760 C. Substantial compressive residual stresses remained in the substrate adjacent to the coating, sufficient to suppress fatigue cracking. The coating continued to protect the substrate from hot corrosion pitting, even after fatigue cracks initiated in the coating.

  13. High strength forgeable tantalum base alloy

    NASA Technical Reports Server (NTRS)

    Buckman, R. W., Jr.

    1975-01-01

    Increasing tungsten content of tantalum base alloy to 12-15% level will improve high temperature creep properties of existing tantalum base alloys while retaining their excellent fabrication and welding characteristics.

  14. High Temperature Corrosion studies on Pulsed Current Gas Tungsten Arc Welded Alloy C-276 in Molten Salt Environment

    NASA Astrophysics Data System (ADS)

    Manikandan, M.; Arivarasu, M.; Arivazhagan, N.; Puneeth, T.; Sivakumar, N.; Murugan, B. Arul; Sathishkumar, M.; Sivalingam, S.

    2016-09-01

    Alloy C-276 is widely used in the power plant environment due to high strength and corrosion in highly aggressive environment. The investigation on high- temperature corrosion resistance of the alloy C-276 PCGTA weldment is necessary for prolonged service lifetime of the components used in corrosive environments. Investigation has been carried out on Pulsed Current Gas Tungsten Arc Welding by autogenous and different filler wires (ERNiCrMo-3 and ERNiCrMo-4) under molten state of K2SO4-60% NaCl environment at 675oC under cyclic condition. Thermogravimetric technique was used to establish the kinetics of corrosion. Weight gained in the molten salt reveals a steady-state parabolic rate law while the kinetics with salt deposits displays multi-stage growth rates. PCGTA ERNiCrMo-3 shows the higher parabolic constant compared to others. The scale formed on the weldment samples upon hot corrosion was characterized by using X-ray diffraction, SEM and EDAX analysis to understand the degradation mechanisms. From the results of the experiment the major phases are identified as Cr2O3, Fe2O3, and NiCr2O4. The result showed that weld fabricated by ERNiCrMo-3 found to be more prone to degradation than base metal and ERNiCrMo-4 filler wire due to higher segregation of alloying element of Mo and W in the weldment

  15. 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.

  16. State-of-technology for joining TD-NiCr sheet.

    NASA Technical Reports Server (NTRS)

    Holko, K. H.; Moore, T. J.; Gyorgak, C. A.

    1972-01-01

    At the current state-of-technology there are many joining processes that can be used to make sound welds in TD-NiCr sheet. Some of these that are described in this report are electron beam welding (EBW), gas-tungsten arc welding (GTAW), diffusion welding (DFW), resistance spot welding (RSW), resistance seam welding (RSEW), and brazing. Roll welding (RW) and explosion welding (EXW) have not been developed to the point where they can be used to make sound welds in TD-NiCr. Joining work that has previously been done on TD-NiCr by various organizations, both privately supported and under Air Force and NASA contracts, is described in this summary. Current work is also described that is being done at General Dynamics/Convair (under NASA contract) and at NASA/Lewis to develop and evaluate DFW, RSW, RSEW, and brazing. Preliminary comparisons of joining processes are made for typical applications. A brief description of the manufacture of TD-NiCr sheet by a recently standardized process (under NASA contract) also is given.

  17. State-of-technology for joining TD-NiCr sheet.

    NASA Technical Reports Server (NTRS)

    Holko, K. H.; Moore, T. J.; Gyorgak, C. A.

    1972-01-01

    At the current state-of-technology there are many joining processes that can be used to make sound welds in TD-NiCr sheet. Some of these that are described in this report are electron beam welding (EBW), gas-tungsten arc welding (GTAW), diffusion welding (DFW), resistance spot welding (RSW), resistance seam welding (RSEW), and brazing. Roll welding (RW) and explosion welding (EXW) have not been developed to the point where they can be used to make sound welds in TD-NiCr. Joining work that has previously been done on TD-NiCr by various organizations, both privately supported and under Air Force and NASA contracts, is described in this summary. Current work is also described that is being done at General Dynamics/Convair (under NASA contract) and at NASA/Lewis to develop and evaluate DFW, RSW, RSEW, and brazing. Preliminary comparisons of joining processes are made for typical applications. A brief description of the manufacture of TD-NiCr sheet by a recently standardized process (under NASA contract) also is given.

  18. Welding high-strength aluminum alloys

    NASA Technical Reports Server (NTRS)

    Parks, P. G.; Hoppes, R. V.; Hasemeyer, E. A.; Masubuchi, K.

    1974-01-01

    Handbook has been published which integrates results of 19 research programs involving welding of high-strength aluminum alloys. Book introduces metallurgy and properties of aluminum alloys by discussing commercial alloys and heat treatments. Several current welding processes are reviewed such as gas tungsten-arc welding and gas metal-arc welding.

  19. Surface Modification of Oilfield Alloys by Ultrasonic Impact Peening: UNS N07718, N07716, G41400, and S17400

    NASA Astrophysics Data System (ADS)

    Singh, Virendra; Marya, Manuel

    2016-01-01

    Ultrasonic impact peening (UIP) is a severe plastic deformation process to induce localized surface hardening combined with compressive residual stresses which therefore extends the useful life of mechanical parts. In this investigation, UIP has been applied to four widespread alloys in use in the oilfields. These include two premium NiCrMo alloys, UNS N07718 (718) and UNS N07716 (625 Plus®), both characterized by satisfactory oilfield performance but lacking hardness and abrasive wear resistance, and two relatively low-cost alloys, UNS G41400 (4140) and UNS S17400 (17-4PH), both limited by their corrosion fatigue. To promote comparisons and determine important alloy parameters for successful UIP, all four alloys were carefully selected so that their respective yield strengths were within relative proximity (~780 to ~910 MPa), and then ultrasonically impact peened under identical conditions. Among major findings from microstructural examinations, micro-hardness indentations, and residual stress measurements, surface topological changes (roughness), alloy microstructural evolution (depth and extent of strain hardening, including mechanical twinning in the NiCrMo alloys), and compressive residual stresses were found to be well correlated. Among all four alloys, the NiCrMo alloys, in particular UNS N07716 was found to be best suited for UIP. This is explained by its FCC austenitic microstructure, relatively low stacking-fault energy (prone to mechanical twinning), and in practical terms high yield strength and high tensile-to-yield strength ratio, both related to its excellent plastic flow behavior under ultrasonic rates of plastic deformation.

  20. A precipitation-hardened high-entropy alloy with outstanding tensile properties

    DOE PAGES

    He, J. Y.; Wang, H.; Huang, H. L.; ...

    2015-09-29

    Recent studies indicated that high-entropy alloys (HEAs) possess unusual structural and thermal features, which could greatly affect dislocation motion and contribute to the mechanical performance, however, a HEA matrix alone is insufficiently strong for engineering applications and other strengthening mechanisms are urgently needed to be incorporated. In this work, we demonstrate the possibility to precipitate nanosized coherent reinforcing phase, i.e., L12-Ni3(Ti,Al), in a fcc-FeCoNiCr HEA matrix using minor additions of Ti and Al. Through thermomechanical processing and microstructure controlling, extraordinary balanced tensile properties at room temperature were achieved, which is due to a well combination of various hardening mechanisms, particularlymore » precipitation hardening. The applicability and validity of the conventional strengthening theories are also discussed. In conclusion, the current work is a successful demonstration of using integrated strengthening approaches to manipulate the properties of fcc-HEA systems, and the resulting findings are important not only for understanding the strengthening mechanisms of metallic materials in general, but also for the future development of high-performance HEAs for industrial applications.« less

  1. A precipitation-hardened high-entropy alloy with outstanding tensile properties

    SciTech Connect

    He, J. Y.; Wang, H.; Huang, H. L.; Xu, X. D.; Chen, M. W.; Wu, Y.; Liu, X. J.; Nieh, T. G.; An, K.; Lu, Z. P.

    2015-09-29

    Recent studies indicated that high-entropy alloys (HEAs) possess unusual structural and thermal features, which could greatly affect dislocation motion and contribute to the mechanical performance, however, a HEA matrix alone is insufficiently strong for engineering applications and other strengthening mechanisms are urgently needed to be incorporated. In this work, we demonstrate the possibility to precipitate nanosized coherent reinforcing phase, i.e., L12-Ni3(Ti,Al), in a fcc-FeCoNiCr HEA matrix using minor additions of Ti and Al. Through thermomechanical processing and microstructure controlling, extraordinary balanced tensile properties at room temperature were achieved, which is due to a well combination of various hardening mechanisms, particularly precipitation hardening. The applicability and validity of the conventional strengthening theories are also discussed. In conclusion, the current work is a successful demonstration of using integrated strengthening approaches to manipulate the properties of fcc-HEA systems, and the resulting findings are important not only for understanding the strengthening mechanisms of metallic materials in general, but also for the future development of high-performance HEAs for industrial applications.

  2. Development of Ion-Plasma Coatings for Protecting Intermetallic Refractory Alloys VKNA-1V and VKNA-25 in the Temperature Range of 1200 - 1250°C

    NASA Astrophysics Data System (ADS)

    Budinovskii, S. A.; Matveev, P. V.; Smirnov, A. A.

    2017-05-01

    Multilayer heat-resistant ion-plasma coatings for protecting the parts of the hot duct of gas-turbine engines produced from refractory nickel alloys based on VKNA intermetallics from high-temperature oxidation are considered. Coatings of the Ni - Cr - Al (Ta, Re, Hf, Y) + Al - Ni - Y systems are tested for high-temperature strength at 1200 and 1250°C. Metallographic and microscopic x-ray spectrum analyses of the structure and composition of the coatings in the initial condition and after the testing are performed. The effect of protective coatings of the Ni - Cr - Al - Hf + Al - Ni - Y systems on the long-term strength of alloys VKNA-1V and VKNA-25 at 1200°C is studied.

  3. Protective claddings for high strength chromium alloys

    NASA Technical Reports Server (NTRS)

    Collins, J. F.

    1971-01-01

    The application of a Cr-Y-Hf-Th alloy as a protective cladding for a high strength chromium alloy was investigated for its effectiveness in inhibiting nitrogen embrittlement of a core alloy. Cladding was accomplished by a combination of hot gas pressure bonding and roll cladding techniques. Based on bend DBTT, the cladding alloy was effective in inhibiting nitrogen embrittlement of the chromium core alloy for up to 720 ks (200hours) in air at 1422 K (2100 F). A significant increase in the bend DBTT occurred with longer time exposures at 1422 K or short time exposures at 1589 K (2400 F).

  4. Structural features of Ni-Cr-Si-B materials obtained by different technologies

    NASA Astrophysics Data System (ADS)

    Kornienko, E. E.; Nikulina, A. A.; Belousova, N. S.; Lazurenko, D. V.; Ivashutenko, A. S.; Kuz'min, V. I.

    2016-11-01

    This study considers the structural features of Ni-Cr-Si-B (Ni - base; 15.1 % Cr; 2 % Si; 2 % B; 0.4 % C) materials obtained by different methods. The self-fluxing coatings were deposited by plasma spraying on the tubes from low carbon steel. Bulk cylinder specimens of 20 mm diameter and 15 mm height were obtained by spark plasma sintering (SPS). The structure and phase composition of these materials were investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The major phases of coatings and sintered materials are γ-Ni, Ni3B, CrB and Cr7C3. We demonstrate that the particle unmelted in the process of plasma spraying or SPS consist of γ-Ni-NEB eutectic and also CrB and Cr7C3 inclusions. The prolonged exposure of powder to high temperatures as well as slow cooling rates by SPS provide for the growth of the structural components as compared to those of plasma coatings materials. High cooling rates at the plasma spraying by melted particles contribute to the formation of supersaturated solid solution of Cr, Si and Fe in γ-Ni. The structure of the melted particles in sintering material has gradient composition: the core constituted of Ni grains of 10 μm with γ-Ni-Ni3B eutectic on the edges. The results of the experiment demonstrate that the sintering material has a smaller microhardness in comparison with plasma coatings (650 and 850 MPa, respectively), but at the same time the material has higher density (porosity less than 1 %) than plasma coatings (porosity about 2.. .3 %).

  5. 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.

  6. Structural and compositional characterization of RF sputter-deposited Ni-Cr + Cr2O3 films

    NASA Technical Reports Server (NTRS)

    Bhushan, B.

    1980-01-01

    An RF-sputtered chrome oxide coating with metallic binders was developed. The chrome oxide coating has high-temperature capabilities and is wear resistant, and has some self-lubricating properties. A nichrome metallic binder was added in the coating to improve its ductility without significant loss in the hardness. The sputtering parameters were optimized to obtain a smooth coating with the maximum adherence. The coatings were applied using bias-sputter and sputter-deposit modes on the heat treated and annealed foil substrates. The coating applied on annealed foils using the sputter-deposit mode was smooth and had the best adherence. Metallurgical examinations showed that the coating was Ni-Cr + Cr2O3. The coating as applied was amorphous and it crystallized during substrate heat treatment.

  7. Fabrication and efficiency evaluation of a hybrid NiCrAl pressure cell up to 4 GPa

    SciTech Connect

    Fujiwara, Naoki; Matsumoto, Takehiko; Koyama-Nakazawa, Kazuko; Hisada, Akihiko; Uwatoko, Yoshiya

    2007-07-15

    A hybrid NiCrAl pressure cell was fabricated to measure magnetic quantities under high pressure above 3 GPa. A pressure of 4.0 GPa was achieved and the pressure cell was found to be reusable even after a pressurizing trial up to 4.0 GPa. Pressure was monitored using {sup 63}Cu nuclear quadrupole resonance of Cu{sub 2}O and ruby fluorescence. The pressure efficiency of a fresh cell was maintained at 96%, and no appreciable deformation was observed at pressures below 3 GPa; on the other hand, the efficiency after pressurizing trials decreased gradually and reached 75% at 4 GPa accompanied by a maximum expansion inside the cylinder of 2%.

  8. Alloy design for intrinsically ductile refractory high-entropy alloys

    NASA Astrophysics Data System (ADS)

    Sheikh, Saad; Shafeie, Samrand; Hu, Qiang; Ahlström, Johan; Persson, Christer; Veselý, Jaroslav; Zýka, Jiří; Klement, Uta; Guo, Sheng

    2016-10-01

    Refractory high-entropy alloys (RHEAs), comprising group IV (Ti, Zr, Hf), V (V, Nb, Ta), and VI (Cr, Mo, W) refractory elements, can be potentially new generation high-temperature materials. However, most existing RHEAs lack room-temperature ductility, similar to conventional refractory metals and alloys. Here, we propose an alloy design strategy to intrinsically ductilize RHEAs based on the electron theory and more specifically to decrease the number of valence electrons through controlled alloying. A new ductile RHEA, Hf0.5Nb0.5Ta0.5Ti1.5Zr, was developed as a proof of concept, with a fracture stress of close to 1 GPa and an elongation of near 20%. The findings here will shed light on the development of ductile RHEAs for ultrahigh-temperature applications in aerospace and power-generation industries.

  9. Concentrations of heavy metals (Mn, Co, Ni, Cr, Ag, Pb) in coffee.

    PubMed

    Nędzarek, Arkadiusz; Tórz, Agnieszka; Karakiewicz, Beata; Clark, Jeremy Simon; Laszczyńska, Maria; Kaleta, Agnieszka; Adler, Grażyna

    2013-01-01

    Technologies involved in roasting coffee beans, as well as the methods used to prepare infusions, vary according to culture, and contribute to differences in the concentration of elements in the drink. Concentrations of six elements: manganese (Mn), cobalt (Co), nickel (Ni), chrome (Cr), silver (Ag) and lead (Pb) were investigated in coffee infusions from eleven samples of coffee, roasted and purchased in four countries: Bosnia and Herzegovina, Brazil, Lebanon and Poland. Metal concentrations were determined using an induction coupled plasma technique in combination with mass spectrometry (ICP-MS, Perkin Elmer) which measures total metal (ionic and non-ionic) content. Metal intake estimated for individual countries (in the respective order; mean consumption per person per year) was as follows: Mn: 26.8-33.1, 28.3-29.5, 29.7, 12.6-18.9 mg; Co: 0.33-0.48, 0.42-0.35, 0.32, 0.12-0.17 mg; Ni: 3.83-5.68, 4.85-5.51, 4.04, 2.06-2.24 mg; Cr: 0.17-0.41, 0.21-0.47, 0.17, 0.09-0.28 mg; Ag: 0.16-1.13, 0.26-0.70, 0.61, 0.33-1.54 mg, Pb: 4.76-7.56, 3.59-5.13, 3.33, 1.48-2.43 mg. This finding gives new data for Mn, Co, Ni, Cr, and Ag intake from coffee , and suggests that the amounts are negligible. However, the data for Pb consumption in heavy drinkers, for example in Bosnia and Herzegovina, indicate that Pb intake from coffee may contribute to the disease burden. The high lead level in some coffees suggests the need for a more precise control of coffee contamination.

  10. 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

  11. CHARACTERIZATION OF AN ADVANCED GADOLINIUM NEUTRON ABSORBER ALLOY BY MEANS OF NEUTRON TRANSMISSION

    SciTech Connect

    Gregg W. Wachs

    2007-09-01

    Neutron transmission experiments were performed on samples of an advanced nickel-chromium-molybdenum-gadolinium (Ni-Cr-Mo-Gd) neutron absorber alloy. The primary purpose of the experiments was to demonstrate the thermal neutron absorbing capability of the alloy at specific gadolinium dopant levels. The new alloy is to be deployed for criticality control of highly enriched DOE SNF. For the transmission experiments, alloy test samples were fabricated with 0.0, 1.58 and 2.1 wt% natural gadolinium dispersed in a Ni-Cr-Mo base alloy. The transmission experiments were successfully carried out at the Los Alamos Neutron Science Center (LANSCE). Measured data from the neutron transmission experiments were compared to calculated results derived from a simple exponential transmission formula using only radiative capture cross sections. Excellent agreement between the measured and calculated results demonstrated the expected strong thermal absorption capability of the gadolinium poison and in addition, verified the measured elemental composition of the alloy test samples. The good agreement also indirectly confirmed that the gadolinium was dispersed fairly uniformly in the alloy and the ENDF VII radiative capture cross section data were accurate.

  12. Thermal Shock Behavior of Air Plasma Sprayed CoNiCrAlY/YSZ Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Liu, Zi Wei; Wu, Wei; Hua, Jia Jie; Lin, Chu Cheng; Zheng, Xue Bin; Zeng, Yi

    2014-07-01

    The structural changes and failure mechanism of thermal barrier coatings (TBCs) during thermal shock cycling were investigated. TBCs consisting of CoNiCrAlY bond coat and partially yttria-stabilized zirconia (YSZ) top coat were deposited by atmospheric plasma spraying (APS) on a nickel-based alloy substrate and its thermal shock resistance performance was evaluated. TBCs were heated at 1100°C for 15 min followed by cold water quenching to ambient temperature. Microstructural evaluation and elemental analysis of TBCs were performed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), respectively. The crack features of YSZ coatings in TBCs during thermal shock cycling, including those of horizontal (parallel to the substrate) and vertical cracks (perpendicular to the substrate), were particularly investigated by means of SEM and image analysis. Results show that horizontal and vertical cracks have different influences on the thermal shock resistance of the coatings. Horizontal cracks that occur at the interface of YSZ and thermally growth oxidation (TGO) cause partial or large-area spalling of coatings. When vertical and horizontal cracks encounter, network segments are formed which lead to partial spalling of the coatings.

  13. Formation and diffusion behavior of intermixed and segregated amorphous layers in sputtered NiCr films on Si

    NASA Astrophysics Data System (ADS)

    Lee, Ju-Hyeon; Rozgonyi, G. A.; Patnaik, B. K.; Knoesen, D.; Adams, D.; Balducci, P.; Salih, A. S. M.

    1993-04-01

    Sputter-deposited Ni80Cr20 films on sputter-cleaned Si substrates contain an amorphous layer at the substrate/film interface whose composition is a mixture of all the elements present at the interface. Subsequent thermal processing at 300 °C for 30 min produces a new segregated Cr-rich amorphous layer as Ni atoms preferentially diffuse through and react with the initial amorphous layer and the silicon substrate. Further annealing results in the growth of uniform nanoscale NiSi layers, as long as the segregated a layer is sustained. The amorphous layers eventually crystallize at ˜500 °C and Kirkendall voids are observed at 550 °C. Whereas the formation of intermixed amorphous layers from metal-metal or metal-silicon systems has been reported by several authors, the segregated amorphous layer arising out of the interdiffusion and reaction between a metal alloy and Si is of both fundamental and technological interest due to its thermal stability and ability to control the silicide growth. In this work, we describe the evolution of both kinds of amorphous layers, i.e., intermixed and segregated, so as to elucidate their origins. The evolution of the two a layers is also observed when monolayers of Pt are introduced prior to NiCr deposition. In this case, the growth of the segregated amorphous layer is retarded and it dissolves earlier during thermal annealing.

  14. Orientational high-entropy alloys

    NASA Astrophysics Data System (ADS)

    Kumar, Nitesh; Subramaniam, Anandh

    2014-12-01

    In high-entropy alloys (HEA), the configurational entropy arising from the presence of multiple elements, stabilizes a disordered solid solution in preference to the possible formation of compounds. In the current work, we identify cluster compounds (of the type AM4X8) as orientational analogues of HEA (as a first report on orientational high-entropy systems). In cluster compounds, orientational disorder increases the entropy and plays a role analogous to positional disorder in HEA. In the GaMo4S8 compound, at temperatures greater than 50 K, the entropic benefit more than makes up for the strain energy cost and stabilizes the disordered phase in preference to an orientationally ordered compound.

  15. Influence of recasting different types of dental alloys on gingival fibroblast cytotoxicity.

    PubMed

    Imirzalioglu, Pervin; Alaaddinoglu, Emine; Yilmaz, Zerrin; Oduncuoglu, Bahar; Yilmaz, Burak; Rosenstiel, Stephen

    2012-01-01

    Surplus alloy from the initial casting is commonly reused with the addition of new alloy. This recasting procedure could affect the cytotoxicity of dental alloys. The purpose of this in vitro study was to evaluate the effect of repeated casting of high-noble and base metal alloys on gingival fibroblast cytotoxicity. Disk-shaped specimens (5 × 2 mm, n=60) of a high-noble (Au-Pt) and 2 base metal (Ni-Cr and Cr-Co, n=20) alloys were prepared with 100% new alloy and 50%, 65%, and 100% once recast alloy. The elemental composition of specimens was analyzed with X-ray energy-dispersive spectroscopy. Five specimens from each group were conditioned in saline with 3% fetal bovine serum albumin. The conditioning media were analyzed for elemental release with atomic absorption spectroscopy. Cytotoxic effects were assessed on human gingival fibroblast with a 3-(4.5-dimethylthiazol-2-yl)-2.5-diphenyl tetrazolium bromide (MTT) colorimetric assay. The data were analyzed with 1-way and 2-way ANOVA and Tukey's HSD multiple comparison test (α-=.05). Elemental compositions of Co-Cr and Au-Pt alloys were significantly different among casting protocols. Elemental release of Co-Cr and Ni-Cr alloys was significantly different between new and recast specimens (P<.001). Nickel release increased with recast alloy addition. The 2-way ANOVA showed a significant effect of the casting procedure (P<.001) alloy group (P<.001) and their interaction for cytotoxicity (P<.001). The Ni-Cr alloy groups with 65% and 100% recast alloy had lower cellular activity than all other specimens (P<.001). The results of this study indicated that alloys containing nickel have increased cytotoxic effects and that composition of the alloys affected the cytotoxicity. Furthermore, recasting nickel-containing alloys with 65% surplus metal addition significantly increased the cytotoxic activity. Copyright © 2012 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  16. High-temperature property data: Ferrous alloys

    SciTech Connect

    Rothman, M.F.

    1987-01-01

    In this book over 250 alloys are organized by AISI number into 10 major sections: Irons, Carbon Steels, Alloy Steels, Low Alloy Constructional Steels, Ultra High Strength Steels, Tool Steels, Maraging Steels, Wrought Stainless Steels, Heat Resistnat Casting Alloys, and Iron Based Rought Superalloys. Each alloy record lists the designation, specifications, UNS number, composition, product forms and a comment on the high-temperature properties and applications. Referenced data is then given for physical properties such as density, specific heat, thermal conductivity, thermal expansion, electrical conductivity, Poisson's ratio, moduli of elasticity and rigidity, etc. Mechanical properties follow, and include tensile properties, shearing and bearing properties, impact properties, creep, stress rupture and stress relaxation and fatigue properties. The last part of the alloy record gives other effects of temperature, such as hot hardness, corrosion, and growth.

  17. 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.

  18. Progress in High-Entropy Alloys

    SciTech Connect

    Gao, Michael C

    2013-12-01

    Strictly speaking, high-entropy alloys (HEAs) refer to single-phase, solid-solution alloys with multiprincipal elements in an equal or a near-equal molar ratio whose configurational entropy is tremendously high. This special topic was organized to reflect the focus and diversity of HEA research topics in the community.

  19. Survey of degradation modes of four nickel-chromium-molybdenum alloys

    SciTech Connect

    Gdowski, G.E.

    1991-03-01

    This report examines the degradation modes of four Ni-Cr-Mo alloys under conditions relevant to the Yucca Mountain Site Characterization Project (YMP). The materials considered are Alloys C-276, C-4, C-22, and 625 because they have desirable characteristics for the conceptual design (CD) of the high-level radioactive-waste containers presented in the YMP Site Characterization Plan (SCP). The types of degradation covered in this report are general corrosion; localized corrosion, including pitting and crevice corrosion; stress corrosion cracking in chloride environments; hydrogen embrittlement (HE); and undesirable phase transformations due to a lack of phase stability. Topics not specifically addressed are welding concerns and microbiological corrosion. The four Ni-Cr-Mo alloys have excellent corrosion resistance in chloride environments such as seawater as well as in more aggressive environments. They have significantly better corrosion resistance than the six materials considered for the CD waste container in the YMP SCP. (Those six materials are Types 304L and 3161L stainless steels, Alloy 825, unalloyed copper, Cu(70)-Ni(30), and 7% aluminum bronze.) In seawater, the Ni-Cr-Mo alloys have negligible general corrosion rates and show little evidence of localized corrosion. The four base materials of these alloys are expected to have nearly indistinguishable corrosion resistance in the YMP environments. The strength requirements of the SCP-CD waste container are met by these materials in the annealed condition; in this condition, they are highly resistant to HE. Historically, HE has been noted when these materials have been strengthened (cold-worked) and used in sour gas (H{sub 2}S and CO{sub 2}) well service -- conditions that are not expected for the YMP. Metallurgical phase stability may be a concern under conditions favoring (1) the formation of intermetallics and carbides, and (2) microstructural ordering.

  20. Annealing effect on the electrical properties and composition of a NiCrAl thin film resistor

    NASA Astrophysics Data System (ADS)

    Chuang, Nai-Chuan; Lin, Jyi-Tsong; Chen, Huey-Ru

    2015-12-01

    The composition of NiCrAl thin film resistors, under different annealing conditions in a N2 atmosphere, was investigated. The Auger electron spectrum (AES) has been used in studying the composition of NiCrAl thin films. The concentration ratio of Cr to Ni decreases when the annealing temperature increases. The electrical properties of a NiCrAl thin film resistor are affected by the concentrations of Cr and Ni, which lead to a higher temperature coefficient of resistance (TCR) and a lower sheet resistivity. The TCR of a NiCrAl thin film resistor is -5 ppm/°C at a 250 °C annealing temperature.

  1. Annealing behavior of high permeability amorphous alloys

    SciTech Connect

    Rabenberg, L.

    1980-06-01

    Effects of low temperature annealing on the magnetic properties of the amorphous alloy Co/sub 71/ /sub 4/Fe/sub 4/ /sub 6/Si/sub 9/ /sub 6/B/sub 14/ /sub 4/ were investigated. Annealing this alloy below 400/sup 0/C results in magnetic hardening; annealing above 400/sup 0/C but below the crystallization temperature results in magnetic softening. Above the crystallization temperature the alloy hardens drastically and irreversibly. Conventional and high resolution transmission electron microscopy were used to show that the magnetic property changes at low temperatures occur while the alloy is truly amorphous. By imaging the magnetic microstructures, Lorentz electron microscopy has been able to detect the presence of microscopic inhomogeneities in this alloy. The low temperature annealing behavior of this alloy has been explained in terms of atomic pair ordering in the presence of the internal molecular field. Lorentz electron microscopy has been used to confirm this explanation.

  2. Braze alloys for high temperature service

    NASA Technical Reports Server (NTRS)

    Lindberg, R. A.; Mckisson, R. L.; Erwin, G., Jr.

    1973-01-01

    Two groups of refractory metal compositions have been developed that are very useful as high temperature brazing alloys for sealing between ceramic and metal parts. Each group consists of various compositions of three selected refractory metals which, when combined, have characteristics required of good braze alloys.

  3. Superior hydrogen storage in high entropy alloys

    NASA Astrophysics Data System (ADS)

    Sahlberg, Martin; Karlsson, Dennis; Zlotea, Claudia; Jansson, Ulf

    2016-11-01

    Metal hydrides (MHx) provide a promising solution for the requirement to store large amounts of hydrogen in a future hydrogen-based energy system. This requires the design of alloys which allow for a very high H/M ratio. Transition metal hydrides typically have a maximum H/M ratio of 2 and higher ratios can only be obtained in alloys based on rare-earth elements. In this study we demonstrate, for the first time to the best of our knowledge, that a high entropy alloy of TiVZrNbHf can absorb much higher amounts of hydrogen than its constituents and reach an H/M ratio of 2.5. We propose that the large hydrogen-storage capacity is due to the lattice strain in the alloy that makes it favourable to absorb hydrogen in both tetrahedral and octahedral interstitial sites. This observation suggests that high entropy alloys have future potential for use as hydrogen storage materials.

  4. Superior hydrogen storage in high entropy alloys.

    PubMed

    Sahlberg, Martin; Karlsson, Dennis; Zlotea, Claudia; Jansson, Ulf

    2016-11-10

    Metal hydrides (MHx) provide a promising solution for the requirement to store large amounts of hydrogen in a future hydrogen-based energy system. This requires the design of alloys which allow for a very high H/M ratio. Transition metal hydrides typically have a maximum H/M ratio of 2 and higher ratios can only be obtained in alloys based on rare-earth elements. In this study we demonstrate, for the first time to the best of our knowledge, that a high entropy alloy of TiVZrNbHf can absorb much higher amounts of hydrogen than its constituents and reach an H/M ratio of 2.5. We propose that the large hydrogen-storage capacity is due to the lattice strain in the alloy that makes it favourable to absorb hydrogen in both tetrahedral and octahedral interstitial sites. This observation suggests that high entropy alloys have future potential for use as hydrogen storage materials.

  5. Copper Alloy For High-Temperature Uses

    NASA Technical Reports Server (NTRS)

    Dreshfield, Robert L.; Ellis, David L.; Michal, Gary

    1994-01-01

    Alloy of Cu/8Cr/4Nb (numbers indicate parts by atom percent) improved over older high-temperature copper-based alloys in that it offers enhanced high temperature strength, resistance to creep, and ductility while retaining most of thermal conductivity of pure copper; in addition, alloy does not become embrittled upon exposure to hydrogen at temperatures as high as 705 degrees C. Designed for use in presence of high heat fluxes and active cooling; for example, in heat exchangers in advanced aircraft and spacecraft engines, and other high-temperature applications in which there is need for such material. High conductivity and hardness of alloy exploited in welding electrodes and in high-voltage and high-current switches and other applications in which wear poses design problem.

  6. The behavior of ZrO2/20%Y2O3 and Al2O3 coatings deposited on aluminum alloys at high temperature regime

    NASA Astrophysics Data System (ADS)

    Pintilei, G. L.; Crismaru, V. I.; Abrudeanu, M.; Munteanu, C.; Baciu, E. R.; Istrate, B.; Basescu, N.

    2015-10-01

    Aluminum alloy present numerous advantages like lightness, high specific strength and diversity which recommend them to a high number of applications from different fields. In extreme environments the protection of aluminum alloys is difficult and requires a high number of requirements like high temperature resistance, thermal fatigue resistance, corrosion fatigue resistance and galvanic corrosion resistance. To obtain these characteristics coatings can be applied to the surfaces so they can enhance the mechanical and chemical properties of the parts. In this paper two coatings were considered for deposition on an AA2024 aluminum alloy, ZrO2/20%Y2O3 and Al2O3. To obtain a better adherence of the coating to the base material an additional bond layer of NiCr is used. Both the coatings and bond layer were deposited by atmospheric plasma spraying on the samples. The samples were subjected to a temperature of 500 °C and after that slowly cooled to room temperature. The samples were analyzed by electron microscopy and X-ray diffraction to determine the morphological and phase changes that occurred during the temperature exposure. To determine the stress level in the parts due to thermal expansion a finite element analysis was performed in the same conditions as the tests.

  7. Structural alloys for high field superconducting magnets

    SciTech Connect

    Morris, J.W. Jr.

    1985-08-01

    Research toward structural alloys for use in high field superconducting magnets is international in scope, and has three principal objectives: the selection or development of suitable structural alloys for the magnet support structure, the identification of mechanical phenomena and failure modes that may influence service behavior, and the design of suitable testing procedures to provide engineering design data. This paper reviews recent progress toward the first two of these objectives. The structural alloy needs depend on the magnet design and superconductor type and differ between magnets that use monolithic and those that employ force-cooled or ICCS conductors. In the former case the central requirement is for high strength, high toughness, weldable alloys that are used in thick sections for the magnet case. In the latter case the need is for high strength, high toughness alloys that are used in thin welded sections for the conductor conduit. There is productive current research on both alloy types. The service behavior of these alloys is influenced by mechanical phenomena that are peculiar to the magnet environment, including cryogenic fatigue, magnetic effects, and cryogenic creep. The design of appropriate mechanical tests is complicated by the need for testing at 4/sup 0/K and by rate effects associated with adiabatic heating during the tests. 46 refs.

  8. Effects of compound carboxylate-urea system on nano Ni-Cr/SiC composite coatings from trivalent chromium baths.

    PubMed

    He, Xinkuai; Hou, Bailong; Cai, Youxing; Wu, Luye

    2013-03-01

    The effects of compound carboxylate-urea system on the nano Ni-Cr/SiC composite coatings from trivalent chromium baths have been investigated in ultrasonic field. These results indicated that the SiC and Cr contents and the thickness of the Ni-Cr/SiC composite coatings could be obviously improved by the compound carboxylate-urea system. The steady-state polarization curves showed that the hydrogen evolution reaction (HER) could be significantly inhibited by the compound carboxylate-urea system, which was benefit to increase the SiC and Cr contents and the thickness of the composite coatings. The cyclic voltammetry (CV) curves showed that both of the Cr(III) and Ni(II) cathodic polarization could be increased in the bath containing the compound carboxylate-urea system. Thus, a compact Ni-Cr/SiC composite coating could be obtained using this technique. The surface morphology of the Ni-Cr/SiC composite coatings checked with the scanning electron micrographs (SEM) showed that the surface smoothness could be also improved and the microcracks and pinholes could be decreased due to the presence of the compound carboxylate-urea system. The phase composition of the as-posited coating was measured by the X-ray diffraction. XRD data showed that the as-posited coating was Ni-Cr/SiC composite coating. The chemical composition of the coating was investigated by energy dispersive spectrum (EDS) analysis. The result showed the Ni-Cr/SiC composite coatings with 3.8 wt.% SiC and 24.68 wt.% Cr were obtained in this study, which had best corrosion resistance according to the results of the typical potentiodynamic polarization curves of the Ni-Cr/SiC composite coatings.

  9. Alloyed coatings for dispersion strengthened alloys

    NASA Technical Reports Server (NTRS)

    Wermuth, F. R.; Stetson, A. R.

    1971-01-01

    Processing techniques were developed for applying several diffusion barriers to TD-Ni and TD-NiCr. Barrier coated specimens of both substrates were clad with Ni-Cr-Al and Fe-Cr-Al alloys and diffusion annealed in argon. Measurement of the aluminum distribution after annealing showed that, of the readily applicable diffusion barriers, a slurry applied tungsten barrier most effectively inhibited the diffusion of aluminum from the Ni-Cr-Al clad into the TD-alloy substrates. No barrier effectively limited interdiffusion of the Fe-Cr-Al clad with the substrates. A duplex process was then developed for applying Ni-Cr-Al coating compositions to the tungsten barrier coated substrates. A Ni-(16 to 32)Cr-3Si modifier was applied by slurry spraying and firing in vacuum, and was then aluminized by a fusion slurry process. Cyclic oxidation tests at 2300 F resulted in early coating failure due to inadequate edge coverage and areas of coating porosity. EMP analysis showed that oxidation had consumed 70 to 80 percent of the aluminum in the coating in less than 50 hours.

  10. Adhesive/cohesive strength of a ZrO2.1-2 w/o Y2O3/NiCrAIY thermal barrier coating

    NASA Technical Reports Server (NTRS)

    Levine, S. R.

    1978-01-01

    The room temperature adhesive/cohesive strength of a 0.05 cm thick ZrO2.12w/oY2O3/0.013 cm thick NiCrAlY thermal barrier coating system (TBC) was investigated. The weakest link was the oxide/NiCrAlY interface region with a strength of 6.2 MN/sq m. The fracture was about half cohesive oxide failure, half oxide/NiCrAlY adhesive failure and 1 percent cohesive NiCrAlY failure. The TBC failed in a similar manner in 950 C tensile and compression tests. The oxide stripped from the TBC had a cohesive strength of 24.6 MN/sq m. The NiCrAlY had a cohesive strength of 25.1 MN/sq m. The NiCrAlY and oxide failed primarily at interparticle boundaries.

  11. High toughness-high strength iron alloy

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R. (Inventor)

    1980-01-01

    An iron alloy is provided which exhibits strength and toughness characteristics at cryogenic temperatures. The alloy consists essentially of about 10 to 16 percent by weight nickel, about 0.1 to 1.0 percent by weight aluminum, and 0 to about 3 percent by weight copper, with the balance being essentially iron. The iron alloy is produced by a process which includes cold rolling at room temperature and subsequent heat treatment.

  12. Corrosion and degradation of a polyurethane/Co-Ni-Cr-Mo pacemaker lead

    SciTech Connect

    Sung, P.; Fraker, A.C.

    1987-12-01

    An investigation to study changes in the metal surfaces and the polyurethane insulation of heart pacemaker leads under controlled in vitro conditions was conducted. A polyurethane (Pellethane 2363-80A)/Co-Ni-Cr-Mo (MP35N) wire lead was exposed in Hanks' physiological saline solution for 14 months and then analyzed using scanning electron microscopy, x-ray energy dispersive analysis, and small angle x-ray scattering. Results showed that some leakage of solution into the lead had occurred and changes were present on both the metal and the polyurethane surfaces.

  13. Thermal Spray Coatings for High-Temperature Corrosion Protection in Biomass Co-Fired Boilers

    NASA Astrophysics Data System (ADS)

    Oksa, M.; Metsäjoki, J.; Kärki, J.

    2015-01-01

    There are over 1000 biomass boilers and about 500 plants using waste as fuel in Europe, and the numbers are increasing. Many of them encounter serious problems with high-temperature corrosion due to detrimental elements such as chlorides, alkali metals, and heavy metals. By HVOF spraying, it is possible to produce very dense and well-adhered coatings, which can be applied for corrosion protection of heat exchanger surfaces in biomass and waste-to-energy power plant boilers. Four HVOF coatings and one arc sprayed coating were exposed to actual biomass co-fired boiler conditions in superheater area with a probe measurement installation for 5900 h at 550 and 750 °C. The coating materials were Ni-Cr, IN625, Fe-Cr-W-Nb-Mo, and Ni-Cr-Ti. CJS and DJ Hybrid spray guns were used for HVOF spraying to compare the corrosion resistance of Ni-Cr coating structures. Reference materials were ferritic steel T92 and nickel super alloy A263. The circulating fluidized bed boiler burnt a mixture of wood, peat and coal. The coatings showed excellent corrosion resistance at 550 °C compared to the ferritic steel. At higher temperature, NiCr sprayed with CJS had the best corrosion resistance. IN625 was consumed almost completely during the exposure at 750 °C.

  14. Thermal Spray Coatings for High-Temperature Corrosion Protection in Biomass Co-Fired Boilers

    NASA Astrophysics Data System (ADS)

    Oksa, M.; Metsäjoki, J.; Kärki, J.

    2014-09-01

    There are over 1000 biomass boilers and about 500 plants using waste as fuel in Europe, and the numbers are increasing. Many of them encounter serious problems with high-temperature corrosion due to detrimental elements such as chlorides, alkali metals, and heavy metals. By HVOF spraying, it is possible to produce very dense and well-adhered coatings, which can be applied for corrosion protection of heat exchanger surfaces in biomass and waste-to-energy power plant boilers. Four HVOF coatings and one arc sprayed coating were exposed to actual biomass co-fired boiler conditions in superheater area with a probe measurement installation for 5900 h at 550 and 750 °C. The coating materials were Ni-Cr, IN625, Fe-Cr-W-Nb-Mo, and Ni-Cr-Ti. CJS and DJ Hybrid spray guns were used for HVOF spraying to compare the corrosion resistance of Ni-Cr coating structures. Reference materials were ferritic steel T92 and nickel super alloy A263. The circulating fluidized bed boiler burnt a mixture of wood, peat and coal. The coatings showed excellent corrosion resistance at 550 °C compared to the ferritic steel. At higher temperature, NiCr sprayed with CJS had the best corrosion resistance. IN625 was consumed almost completely during the exposure at 750 °C.

  15. Phonon broadening in high entropy alloys

    NASA Astrophysics Data System (ADS)

    Körmann, Fritz; Ikeda, Yuji; Grabowski, Blazej; Sluiter, Marcel H. F.

    2017-09-01

    Refractory high entropy alloys feature outstanding properties making them a promising materials class for next-generation high-temperature applications. At high temperatures, materials properties are strongly affected by lattice vibrations (phonons). Phonons critically influence thermal stability, thermodynamic and elastic properties, as well as thermal conductivity. In contrast to perfect crystals and ordered alloys, the inherently present mass and force constant fluctuations in multi-component random alloys (high entropy alloys) can induce significant phonon scattering and broadening. Despite their importance, phonon scattering and broadening have so far only scarcely been investigated for high entropy alloys. We tackle this challenge from a theoretical perspective and employ ab initio calculations to systematically study the impact of force constant and mass fluctuations on the phonon spectral functions of 12 body-centered cubic random alloys, from binaries up to 5-component high entropy alloys, addressing the key question of how chemical complexity impacts phonons. We find that it is crucial to include both mass and force constant fluctuations. If one or the other is neglected, qualitatively wrong results can be obtained such as artificial phonon band gaps. We analyze how the results obtained for the phonons translate into thermodynamically integrated quantities, specifically the vibrational entropy. Changes in the vibrational entropy with increasing the number of elements can be as large as changes in the configurational entropy and are thus important for phase stability considerations. The set of studied alloys includes MoTa, MoTaNb, MoTaNbW, MoTaNbWV, VW, VWNb, VWTa, VWNbTa, VTaNbTi, VWNbTaTi, HfZrNb, HfMoTaTiZr.

  16. Grain boundary diffusion of {sup 181}W in Fe-Cr ferritic alloys

    SciTech Connect

    Cermak, J.; Ruzickova, J.; Pokorna, A.

    1995-07-15

    The grain boundary diffusivity s{delta}D{sub b} of {sup 181}W in binary Fe-Cr alloys with 8--12 wt.% Cr, in a ternary alloy Fe-8Cr-0.17C and in two commercial modifications of 8% Cr ferritic steels were measured by the serial sectioning method in the temperature range 773--1,123 K. A variation of the Cr concentration in the range 8--12 wt.% does not influence s{delta}D{sub b}. The addition of carbon and, probably also phosphorus, decreases s{delta}D{sub b} similarly as it was observed in a previous study on iron diffusion in austenitic alloys Fe-Ni-Cr-C and Fe-Ni-Cr-P. The binary alloys could be considered pure, i.e. free of carbon, above 883 K, whereas at lower temperatures, probably due to residual carbon segregation to grain boundaries, a considerable decrease in s{delta}D{sub b} was observed compared with the extrapolated values from the high temperature region. The tungsten grain boundary diffusivity was found to be insensitive to small changes in the concentration of other alloying or impurity elements.

  17. Multiscale Modeling of Grain Boundary Segregation and Embrittlement in Tungsten for Mechanistic Design of Alloys for Coal Fired Plants

    SciTech Connect

    Luo, Jian; Tomar, Vikas; Zhou, Naixie; Lee, Hongsuk

    2013-06-30

    Based on a recent discovery of premelting-like grain boundary segregation in refractory metals occurring at high temperatures and/or high alloying levels, this project investigated grain boundary segregation and embrittlement in tungsten (W) based alloys. Specifically, new interfacial thermodynamic models have been developed and quantified to predict high-temperature grain boundary segregation in the W-Ni binary alloy and W-Ni-Fe, W-Ni-Ti, W-Ni-Co, W-Ni-Cr, W-Ni-Zr and W-Ni-Nb ternary alloys. The thermodynamic modeling results have been experimentally validated for selected systems. Furthermore, multiscale modeling has been conducted at continuum, atomistic and quantum-mechanical levels to link grain boundary segregation with embrittlement. In summary, this 3-year project has successfully developed a theoretical framework in combination with a multiscale modeling strategy for predicting grain boundary segregation and embrittlement in W based alloys.

  18. High-temperature alloys for high-power thermionic systems

    SciTech Connect

    Shin, Kwang S.; Jacobson, D.L.; D'cruz, L.; Luo, Anhua; Chen, Bor-Ling.

    1990-08-01

    The need for structural materials with useful strength above 1600 k has stimulated interest in refractory-metal alloys. Tungsten possesses an extreme high modulus of elasticity as well as the highest melting temperature among metals, and hence is being considered as one of the most promising candidate materials for high temperature structural applications such as space nuclear power systems. This report is divided into three chapters covering the following: (1) the processing of tungsten base alloys; (2) the tensile properties of tungsten base alloys; and (3) creep behavior of tungsten base alloys. Separate abstracts were prepared for each chapter. (SC)

  19. Short Communication on "Self-welding susceptibility of NiCr-B hardfaced coating with and without NiCr-B coating on 316LN stainless steel in flowing sodium at elevated temperature"

    NASA Astrophysics Data System (ADS)

    Kumar, Hemant; Ramakrishnan, V.; Albert, S. K.; Bhaduri, A. K.; Ray, K. K.

    2017-02-01

    The self-welding susceptibility between NiCr-B coated 316LN stainless steel and the base metal, and that between NiCr-B hardfaced coatings has been evaluated in flowing sodium at 823 K for 90 and 135 days under contact stress of 8.0 and 11.0 MPa using a fabricated set-up. Neither any self-welding could be observed nor could any damage be detected on the specimen surfaces of the selected materials under the imposed experimental conditions, which indicate their satisfactory potential for applications in Fast Breeder Reactors.

  20. Microstructure of Vacuum-Brazed Joints of Super-Ni/NiCr Laminated Composite Using Nickel-Based Amorphous Filler Metal

    NASA Astrophysics Data System (ADS)

    Ma, Qunshuang; Li, Yajiang; Wu, Na; Wang, Juan

    2013-06-01

    Vacuum brazing of super-Ni/NiCr laminated composite and Cr18-Ni8 stainless steel was carried out using Ni-Cr-Si-B amorphous filler metal at 1060, 1080, and 1100 °C, respectively. Microstructure and phase constitution were investigated by means of optical and scanning electron microscopy, energy-dispersive spectroscopy, x-ray diffraction, and micro-hardness tester. When brazed at 1060-1080 °C, the brazed region can be divided into two distinct zones: isothermally solidified zone (ISZ) consisting of γ-Ni solid solution and athermally solidified zone (ASZ) consisting of Cr-rich borides. Micro-hardness of the Cr-rich borides formed in the ASZ was as high as 809 HV50 g. ASZ decreased with increase of the brazing temperature. Isothermal solidification occurred sufficiently at 1100 °C and an excellent joint composed of γ-Ni solid solution formed. The segregation of boron from ISZ to residual liquid phase is the reason of Cr-rich borides formed in ASZ. The formation of secondary precipitates in diffusion-affected zone is mainly controlled by diffusion of B.

  1. Modified Sol-Gel Processing of NiCr2O4 Nanoparticles; Structural Analysis and Optical Band Gap

    NASA Astrophysics Data System (ADS)

    Enhessari, Morteza; Salehabadi, Ali; Khanahmadzadeh, Salah; Arkat, Kamal; Nouri, Jalal

    2017-02-01

    Nickel Chromite nanoparticles were successfully synthesized via a modified sol-gel method using nickel acetate and ammonium dichromate in melted stearic acid as a complexing agent. The diffractograms of the nanoparticles confirmed a pure formation of NiCr2O4 spinel without any minor phase. The coordination structure of as prepared nanoparticles shows a series of absorption bands below 1,000 cm-1 were evidenced the M-O (Cr-O, Ni-O) bond in the sample. Optical band gap, magnetic properties and color parameters (L*.a*.b*) indicates that the final nanoparticles are optically and magnetically active. The particle size of NiCr2O4 was calculated using Scherrer equation at about 24 nm. Optical band gap obtained at 1.7 eV indicating that NiCr2O4 nanoparticles are semiconductor material and can be used in electrical devices.

  2. Stability Improvement of Tactile Sensor of Normal and Shear Stresses Using Ni-Cr Thin Film Gauge

    NASA Astrophysics Data System (ADS)

    Onishi, Hiroyuki; Sohgawa, Masayuki; Tachibana, Hiroto; Huang, Yu Ming; Kanashima, Takeshi; Okuyama, Masanori; Yamashita, Kaoru; Noda, Minoru; Noma, Haruo

    Tactile sensor consisted of micro-cantilevers has been developed to detect both normal and shear stresses, and have human-friendly surface. NiCr thin film is used as strain gauge having low resistance drift, although Si piezo-resistance gauge shows the large resistance drift induced by large temperature coefficient of resistance (TCR) and its output is unstable. TCRs of NiCr films prepared by vacuum evaporation and sputtering (at RT and 600°C) are 0.054%, 0.082%, and 0.0065%, respectively, and are much lower than that of Si, 0.25%. As a result, reduction of resistance drift and stabilization of the sensor have been obtained by using NiCr thin gauge.

  3. Simulation and Modeling in High Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Toda-Caraballo, I.; Wróbel, J. S.; Nguyen-Manh, D.; Pérez, P.; Rivera-Díaz-del-Castillo, P. E. J.

    2017-08-01

    High entropy alloys (HEAs) is a fascinating field of research, with an increasing number of new alloys discovered. This would hardly be conceivable without the aid of materials modeling and computational alloy design to investigate the immense compositional space. The simplicity of the microstructure achieved contrasts with the enormous complexity of its composition, which, in turn, increases the variety of property behavior observed. Simulation and modeling techniques are of paramount importance in the understanding of such material performance. There are numerous examples of how different models have explained the observed experimental results; yet, there are theories and approaches developed for conventional alloys, where the presence of one element is predominant, that need to be adapted or re-developed. In this paper, we review of the current state of the art of the modeling techniques applied to explain HEAs properties, identifying the potential new areas of research to improve the predictability of these techniques.

  4. HIGH-TEMPERATURE OXIDATION PROTECTIVE COATINGS FOR VANADIUM-BASE ALLOYS

    DTIC Science & Technology

    SILICIDES , SILICON COATINGS , THIN FILM STORAGE DEVICES, TITANIUM ALLOYS, VAPOR PLATING, YTTRIUM COMPOUNDS, ZINC ALLOYS, ZINC COATINGS ....ANTIOXIDANTS, *METAL COATINGS , *REFRACTORY COATINGS , *VANADIUM ALLOYS, ALUMINUM ALLOYS, CERAMIC COATINGS , CHROMIUM ALLOYS, CLADDING, FLAME SPRAYING...HIGH TEMPERATURE, INTERMETALLIC COMPOUNDS, IODINE COMPOUNDS, IRON ALLOYS, MAGNESIUM ALLOYS, NICKEL ALLOYS, NICKEL COMPOUNDS, NIOBIUM ALLOYS, OXIDES

  5. Formation of nanostructures in Ni-22Cr-11Fe-1X (X = Y2O3, TiO2) alloys by high-energy ball-milling.

    PubMed

    Park, Jiwhan; Jang, Jinsung; Kim, Tae Kyu; Kim, Sung-Jin; Ahn, Jung-Ho

    2011-07-01

    Powder mixtures of Ni, Cr, Fe and Y2O3 were high-energy ball-milled and subsequently sintered to fabricate Ni-based oxide-dispersion strengthened (ODS) alloys. Nano-sized Y2O3 and/or TiO2 seem to be dissolved in the Ni matrix forming a metastable solid solution during high-energy ball-milling or mechanical alloying (MA) process. The finely grained MA powders with high dislocation density facilitated the decomposition of oxides. The MA powders were consolidated to near-full density by spark plasma sintering at 1100 degrees C for 5 minutes in an Ar atmosphere. The Cr oxides as well as decomposed Y- and Ti-oxides thermally precipitated as oxide particles of several tens nanometers at this temperature, although sintering was carried out during a short time. The SPSed specimen showed a near full densification with almost pore-free microstructures. Examination of fractured surface showed a typical dimple rupture with fine and homogeneous distribution of dispersoids, indicating non-negligible room temperature ductility combined with high mechanical strength.

  6. Thermogravimetric study of reduction of oxides present in oxidized nickel-base alloy powders

    NASA Technical Reports Server (NTRS)

    Herbell, T. P.

    1976-01-01

    Carbon, hydrogen, and hydrogen plus carbon reduction of three oxidized nickel-base alloy powders (a solid solution strengthened alloy both with and without the gamma prime formers aluminum and titanium and the solid solution strengthened alloy NiCrAlY) were evaluated by thermogravimetry. Hydrogen and hydrogen plus carbon were completely effective in reducing an alloy containing chromium, columbium, tantalum, molybdenum, and tungsten. However, with aluminum and titanium present the reduction was limited to a weight loss of about 81 percent. Carbon alone was not effective in reducing any of the alloys, and none of the reducing conditions were effective for use with NiCrAlY.

  7. High Temperature Ordered Intermetallic Alloys

    DTIC Science & Technology

    1991-01-02

    AD-A232 769______ REPORT DOCUMENTATION PAGE OM NA 0704,u =otmferiwe. .. tio24.nqol .S 20~32 ton t o t i t re I$ out". *avunt ~~~ aeon "**Ou& M ft...Khowash, West Virginia University, Department of Physics, Morgantown, WV: D.L. Price, Memphis 2.30 P M . 02.3 State University, Department of Physics...DISLOCATION CORE STRUCTURES AND MECHANICAL BEHAVIOR MAGNETIC Fe-V SUBSTITUTIONAL ALLOYS SUBSTITUTIONAL OF LI. AND DO. TYPE AjITi, M . Khantha, V. Vitek and

  8. The metallurgy of high temperature alloys

    NASA Technical Reports Server (NTRS)

    Tien, J. K.; Purushothaman, S.

    1976-01-01

    Nickel-base, cobalt-base, and high nickel and chromium iron-base alloys are dissected, and their microstructural and chemical components are assessed with respect to the various functions expected of high temperature structural materials. These functions include the maintenance of mechanical integrity over the strain-rate spectrum from creep resistance through fatigue crack growth resistance, and such alloy stability expectations as microstructural coarsening resistance, phase instability resistance and oxidation and corrosion resistance. Special attention will be given to the perennial conflict and trade-off between strength, ductility and corrosion and oxidation resistance. The newest developments in the constitution of high temperature alloys will also be discussed, including aspects relating to materials conservation.

  9. ACCELERATED TESTING OF NEUTRON-ABSORBING ALLOYS FOR NUCLEAR CRITICALITY CONTROL

    SciTech Connect

    Ronald E. Mizia

    2011-10-01

    The US Department of Energy requires nuclear criticality control materials be used for storage of highly enriched spent nuclear fuel used in government programs and the storage of commercial spent nuclear fuel at the proposed High-Level Nuclear Waste Geological Repository located at Yucca Mountain, Nevada. Two different metallic alloys (Ni-Cr-Mo-Gd and borated stainless steel) have been chosen for this service. An accelerated corrosion test program to validate these materials for this application is described and a performance comparison is made.

  10. Superior hydrogen storage in high entropy alloys

    PubMed Central

    Sahlberg, Martin; Karlsson, Dennis; Zlotea, Claudia; Jansson, Ulf

    2016-01-01

    Metal hydrides (MHx) provide a promising solution for the requirement to store large amounts of hydrogen in a future hydrogen-based energy system. This requires the design of alloys which allow for a very high H/M ratio. Transition metal hydrides typically have a maximum H/M ratio of 2 and higher ratios can only be obtained in alloys based on rare-earth elements. In this study we demonstrate, for the first time to the best of our knowledge, that a high entropy alloy of TiVZrNbHf can absorb much higher amounts of hydrogen than its constituents and reach an H/M ratio of 2.5. We propose that the large hydrogen-storage capacity is due to the lattice strain in the alloy that makes it favourable to absorb hydrogen in both tetrahedral and octahedral interstitial sites. This observation suggests that high entropy alloys have future potential for use as hydrogen storage materials. PMID:27829659

  11. Study of high performance alloy electroforming

    NASA Technical Reports Server (NTRS)

    Malone, G. A.

    1984-01-01

    Nickel-manganese electroformed specimens and nickel-cobalt-manganese samples were heat treated at 343 C (650 F) for comparison of room temperature ductility with that observed for alloys heat treated at 315.6C (600 F). All heat treatments were for 24 hours. This heat treatment temperature increase generally did not result in significant improvements in ductility. However, increases in yield strength - with slight decreases in tensile strengths - were noted for the nickel-manganese and nickel-cobalt-manganese alloys. For the case of employing fairly high manganese contents in the electrolyte and countering ensuing high tensile stress in the alloy by saccharin additions to the bath, it was noted that nickel-manganese alloys with over 0.4% by weight manganese retained high ultimate and yield strengths after the 343 C (650 F) heat treatment for 24 hours. Elongations were still lower than desired. For alloys with less than 0.4% by weight manganese this heat treatment provided excellent ductility, but very significant reductions in ultimate and yield strengths were noted.

  12. Precipitation Hardenable High Temperature Shape Memory Alloy

    NASA Technical Reports Server (NTRS)

    Noebe, Ronald Dean (Inventor); Draper, Susan L. (Inventor); Nathal, Michael V. (Inventor); Crombie, Edwin A. (Inventor)

    2010-01-01

    A composition of the invention is a high temperature shape memory alloy having high work output, and is made from (Ni+Pt+Y),Ti(100-x) wherein x is present in a total amount of 49-55 atomic % Pt is present in a total amount of 10-30 atomic %, Y is one or more of Au, Pd. and Cu and is present in a total amount of 0 to 10 atomic %. The alloy has a matrix phase wherein the total concentration of Ni, Pt, and the one or more of Pd. Au, and Cu is greater than 50 atomic %.

  13. Refractory High-Entropy Alloys (Postprint)

    DTIC Science & Technology

    2010-06-23

    AFRL-RX-WP-JA-2015-0119 REFRACTORY HIGH-ENTROPY ALLOYS (POSTPRINT) D.B. Miracle AFRL/RXCM O.N. Senkov UES, Inc. G.B. Wilks...AUTHOR(S) D.B. Miracle - AFRL/RXCM O.N. Senkov - UES, Inc. G.B. Wilks - General Dynamics, Corp. C.P. Chuang and P.K. Liaw - The University...intermetRefractory high-entropy alloys O.N. Senkov a,b,*, G.B. Wilks a,c, D.B. Miracle a, C.P. Chuang d, P.K. Liawd aAir Force Research Laboratory

  14. Influence of cryomilling on the microstructural features in HVOF-sprayed NiCrAlY bond coats for thermal barrier coatings: Creation of a homogeneous distribution of nanoscale dispersoids

    NASA Astrophysics Data System (ADS)

    Ma, Kaka; Schoenung, Julie M.

    2010-10-01

    Previous research has revealed that thermal barrier coatings with cryomilled bond coats exhibit improved thermal cycling lifetime by growing a continuous and uniform oxide layer at a slower rate; yet the mechanism controlling the ultimate failure remains unclear. In an effort to provide a foundation for understanding the improved behavior, the influence of cryomilling on the microstructure of the NiCrAlY bond coat material is investigated in this article. Rather than focusing on the alumina scale formation, the microstructural features and their evolution within the high-velocity oxy-fuel (HVOF)-sprayed NiCrAlY bond coats themselves, prepared from conventional powder and cryomilled powder, were carefully compared through extensive scanning electron microscope/energy-dispersive X-ray spectroscopy characterization. In addition, the as-cryomilled NiCrAlY powder is characterized to provide evidence of the direct influence of cryomilling and to exclude the impact from the HVOF spraying. It is found that the essential change in microstructural features resulting from the cryomilling is the creation of a homogeneous distribution of ultrafine (nanoscale) Al-rich oxide/nitride dispersoids, which remain thermally stable even after exposure at 1100°C for 100 h. The TEM study on the as-cryomilled powder, prior to the HVOF spraying, indicates that some Al and Y-rich oxides are already present within the material as a direct result of the cryomilling process.

  15. High strength cast aluminum alloy development

    NASA Astrophysics Data System (ADS)

    Druschitz, Edward A.

    The goal of this research was to understand how chemistry and processing affect the resulting microstructure and mechanical properties of high strength cast aluminum alloys. Two alloy systems were investigated including the Al-Cu-Ag and the Al-Zn-Mg-Cu systems. Processing variables included solidification under pressure (SUP) and heat treatment. This research determined the range in properties that can be achieved in BAC 100(TM) (Al-Cu micro-alloyed with Ag, Mn, Zr, and V) and generated sufficient property data for design purposes. Tensile, stress corrosion cracking, and fatigue testing were performed. CuAl2 and Al-Cu-Fe-Mn intermetallics were identified as the ductility limiting flaws. A solution treatment of 75 hours or longer was needed to dissolve most of the intermetallic CuAl 2. The Al-Cu-Fe-Mn intermetallic was unaffected by heat treatment. These results indicate that faster cooling rates, a reduction in copper concentration and a reduction in iron concentration might increase the ductility of the alloy by decreasing the size and amount of the intermetallics that form during solidification. Six experimental Al-Zn-Mg-Cu series alloys were produced. Zinc concentrations of 8 and 12wt% and Zn/Mg ratios of 1.5 to 5.5 were tested. Copper was held constant at 0.9%. Heat treating of the alloys was optimized for maximum hardness. Al-Zn-Mg-Cu samples were solution treated at 441°C (826°F) for 4 hours before ramping to 460°C (860°F) for 75 hours and then aged at 120°C (248°F) for 75 hours. X-ray diffraction showed that the age hardening precipitates in most of these alloys was the T phase (Mg32Zn 31.9Al17.1). Tensile testing of the alloys showed that the best mechanical properties were obtained in the lowest alloy condition. Chilled Al-8.2Zn-1.4Mg-0.9Cu solidified under pressure resulted in an alloy with a yield strength of 468MPa (68ksi), tensile strength of 525MPa (76ksi) and an elongation of 9%.

  16. Cast Aluminum Alloy for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2003-01-01

    Originally developed by NASA as high performance piston alloys to meet U.S. automotive legislation requiring low exhaust emission, the novel NASA alloys now offer dramatic increase in tensile strength for many other applications at elevated temperatures from 450 F (232 C) to about 750 F (400 C). It is an ideal low cost material for cast automotive components such as pistons, cylinder heads, cylinder liners, connecting rods, turbo chargers, impellers, actuators, brake calipers and rotors. It can be very economically produced from conventional permanent mold, sand casting or investment casting, with silicon content ranging from 6% to 18%. At high silicon levels, the alloy exhibits excellent dimensional stability, surface hardness and wear resistant properties.

  17. Valence band anticrossing in highly mismatched alloys

    NASA Astrophysics Data System (ADS)

    Alberi, Kirstin Mclean

    Semiconductor alloys offer the ability to tune certain material parameters such as the band gap or carrier effective mass through precise control of the alloy composition, allowing them to be optimized for specific device requirements. While many alloys demonstrate near linear composition dependencies in these properties, those containing isoelectronic anion species that are significantly mismatched in electronegativity or ionization energy, known as highly mismatched alloys (HMA), exhibit substantial deviation from this trend. Here, the optical and electrical properties of HMAs containing dilute concentrations of large metallic anions are investigated in the context of a valence band anticrossing (VBAC) theory. Minority species with low ionization energies often introduce localized p-states near the valence band edge of the host semiconductor. Hybridization of these localized states with the extended p-states of the host may be described by a 12 x 12 Hamiltonian and produces a splitting of the alloy valence band into E+ and E - states. Photomodulated reflectance studies coupled with the VBAC theory confirm that the band gap bowing observed in GaSbxAs1-x and GaBixAs1-x is caused by an upward movement of the valence band edge as a result of the anticrossing interaction between the E+ and E- states. The valence band restructuring also adversely affects hole transport in these alloys through an increase in the heavy hole effective mass and the addition of an alloy disorder scattering mechanism. Finally, the VBAC theory has been extended to group IV HMAs as well as to the dilute magnetic semiconductor Ga1-x MnxAs, both of which exhibit strong hole localization at the minority species sites.

  18. Solid-state and fusion resistance spot welding of TD-NiCr sheet

    NASA Technical Reports Server (NTRS)

    Moore, T. J.

    1973-01-01

    By using specially processed TD-NiCr sheet in both 0.4-mm (0.015-in.) and 1.6-mm (0.062-in.) thicknesses and carefully selected welding procedures, solid state resistance spot welds were produced which, after postheating at 1200 C, were indistinguishable from the parent material. Stress-rupture shear tests of single-spot lap joints in 0.4-mm (0.015-in.) thick sheet showed that these welds were as strong as the parent material. Similar results were obtained in tensile-shear tests at room temperature and 1100 C and in fatigue tests. Conventional fusion spot welds in commercial sheet were unsatisfactory because of poor stress-rupture shear properties resulting from metallurgical damage to the parent material.

  19. Characteristics of Ni-Cr-Fe laser clad layers on EA4T steel

    NASA Astrophysics Data System (ADS)

    Chen, Wenjing; Chen, Hui; Wang, Yongjing; Li, Congchen; Wang, Xiaoli

    2017-07-01

    The Ni-Cr-Fe metal powder was deposited on EA4T steel by laser cladding technology. The microstructure and chemical composition of the cladding layer were analyzed by optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The bonding ability between the cladding layer and the matrix was measured. The results showed that the bonding between the cladding layer and the EA4T steel was metallurgical bonding. The microstructure of cladding layer was composed of planar crystals, columnar crystals and dendrite, which consisted of Cr2Ni3, γ phase, M23C6 and Ni3B phases. When the powder feeding speed reached 4 g/min, the upper bainite occurred in the heat affected zone (HAZ). Moreover, the tensile strength of the joint increased, while the yield strength and the ductility decreased.

  20. Study of exchange bias in NiCr2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Singh, H.; Chakraborty, T.; Srikanth, K.; Chandra, R.; Mitra, C.; Kumar, U.

    2014-09-01

    We investigated exchange bias as a function of temperature in nanoparticles of ferrimagnetic normal spinel NiCr2O4. The studied bulk compound exhibits ferrimagnetic and canted antiferromagnetic ordering at 68 K and 30 K respectively. Sample characterization was carried out using X-Ray, Field Emission Scanning Electron Microscope (FE-SEM) and Transmission Electron Microscope (TEM) measurements. Magnetization measurements as a function of temperature has revealed interesting features. Magnetic isotherms of bulk and nanoparticle sample were also investigated at different temperatures. It was found that in nanoparticles, with decrease in temperature, exchange bias first increases, attains maximum value and then subsequently decreases. We argue that in nanoparticles, the higher exchange bias at 68 K is because of coexistence of ferrimagnetic and surface spin effect. However, the presence of glassy spin state may be the reason for decreasing exchange bias effect below Tc down to 5 K.

  1. Study of exchange bias and training effect in NiCr2O4

    NASA Astrophysics Data System (ADS)

    Barman, Junmoni; Bora, Tribedi; Ravi, S.

    2015-07-01

    Single phase sample of NiCr2O4 crystallized in a tetragonal structure of I41/amd space group was prepared. Ferrimagnetic transition at TC=73 K along with a large irreversibility has been observed from the magnetization measurement. The sample exhibits exchange bias phenomenon and it is explained by considering the anisotropic exchange interaction between the ferrimagnetic and the antiferromagnetic components of magnetic moment. Presence of training effect is also observed. The exchange bias field (HEB) is found to decay exponentially with increase in temperature and however, the coercive field (HCeff) follows the empirical relation HCeff = HCeff [ 1 - T/TC']2 . The maximum experimental values of HEB and HCeff are found to be 313 Oe and 4839 Oe respectively.

  2. Tribological and Oxidative Behavior of Thermally Sprayed NiCrBSi Coatings

    NASA Astrophysics Data System (ADS)

    Garrido, M. A.; Rico, A.; Gómez, M. T.; Cadenas, M.; Fernández-Rico, J. E.; Rodríguez, J.

    2017-01-01

    The behavior of NiCrBSi coatings deposited by three different spraying techniques was studied: flame spray with a subsequent flame treatment (FS + Flame), flame spray with post-laser treatment (FS + Laser) and laser cladding (LC). The coating responses under wear and oxidation conditions were analyzed. Although the microstructure of the coatings deposited by the three different techniques showed similar phases and precipitates, some changes in the size and distribution of these constituents were observed. The pin on disk configuration was used to determine the friction coefficients and wear rates. LC coatings showed the highest wear resistance, with plastic deformation being the main wear mechanism identified for all of the coatings analyzed. Tests under aggressive environments were also performed to determine the oxidation kinetics.

  3. Tribological and Oxidative Behavior of Thermally Sprayed NiCrBSi Coatings

    NASA Astrophysics Data System (ADS)

    Garrido, M. A.; Rico, A.; Gómez, M. T.; Cadenas, M.; Fernández-Rico, J. E.; Rodríguez, J.

    2017-02-01

    The behavior of NiCrBSi coatings deposited by three different spraying techniques was studied: flame spray with a subsequent flame treatment (FS + Flame), flame spray with post-laser treatment (FS + Laser) and laser cladding (LC). The coating responses under wear and oxidation conditions were analyzed. Although the microstructure of the coatings deposited by the three different techniques showed similar phases and precipitates, some changes in the size and distribution of these constituents were observed. The pin on disk configuration was used to determine the friction coefficients and wear rates. LC coatings showed the highest wear resistance, with plastic deformation being the main wear mechanism identified for all of the coatings analyzed. Tests under aggressive environments were also performed to determine the oxidation kinetics.

  4. Reaction diffusion in the NiCrAl and CoCrAl systems

    NASA Technical Reports Server (NTRS)

    Levine, S. R.

    1978-01-01

    The paper assesses the effect of overlay coating and substrate composition on the kinetics of coating depletion by interdiffusion. This is accomplished by examining the constitution, kinetics and activation energies for a series of diffusion couples primarily of the NiCrAl/Ni-10Cr or CoCrAl/Ni-10Cr type annealed at temperatures in the range 1000-1205 C for times up to 500 hr. A general procedure is developed for analyzing diffusion in multicomponent multiphase systems. It is shown that by introducing the concept of beta-source strength, which can be determined from appropriate phase diagrams, the Wagner solution for consumption of a second phase in a semiinfinite couple is successfully applied to the analysis of MCrAl couples. Thus, correlation of beta-recession rate constants with couple composition, total and diffusional activation energies, and interdiffusion coefficients are determined.

  5. Effects of phosphorus and molybdenum on the caustic stress corrosion cracking of NiCrMoV steels

    SciTech Connect

    Bandyopadhyay, N.; Briant, C.L.

    1984-01-01

    This paper presents a study of the effects of phosphorus and molybdenum on caustic stress corrosion cracking of 3.5NiCrMoV rotor steels. The results show that phosphorus segregation to the grain boundaries substantially lowers the resistance of the steel to caustic cracking. Removal of molybdenum provides some improvement in the resistance to caustic cracking.

  6. High-strength iron aluminide alloys

    SciTech Connect

    McKamey, C.G.; Maziasz, P.J.

    1996-06-01

    Past studies have shown that binary Fe{sub 3}Al possesses low creep-rupture strength compared to many other alloys, with creep-rupture lives of less than 5 h being reported for tests conducted at 593{degrees}C and 207 MPa. The combination of poor creep resistance and low room-temperature tensile ductility due to a susceptibility to environmentally-induced dynamic hydrogen embrittlement has limited use of these alloys for structural applications despite their excellent corrosion properties. With regard to the ductility problem, alloy development efforts have produced significant improvements, with ductilities of 10-20% and tensile yield strengths as high as 500 MPa being reported. Likewise, initial improvements in creep resistance have been realized through small additions of Mo, Nb, and Zr.

  7. Technical note - Plasma-sprayed ceramic thermal barrier coatings for smooth intermetallic alloys

    NASA Technical Reports Server (NTRS)

    Miller, R. A.; Doychak, J.

    1992-01-01

    A new approach for plasma spray deposition of ceramic thermal barrier coatings directly to smooth substrates is described. Ceramic thermal barrier coatings were directly applied to substrates that had been coated with low-pressure plasma sprayed NiCrAlY bond coats and then centerless ground to simulate a smooth oxidation-resistant substrate. As the high-temperature oxidation behavior of NiAl+Zr is superior to that of MCrALY alloy, the bond coat is not required for oxidation resistance.

  8. Technical note - Plasma-sprayed ceramic thermal barrier coatings for smooth intermetallic alloys

    NASA Astrophysics Data System (ADS)

    Miller, R. A.; Doychak, J.

    1992-09-01

    A new approach for plasma spray deposition of ceramic thermal barrier coatings directly to smooth substrates is described. Ceramic thermal barrier coatings were directly applied to substrates that had been coated with low-pressure plasma sprayed NiCrAlY bond coats and then centerless ground to simulate a smooth oxidation-resistant substrate. As the high-temperature oxidation behavior of NiAl+Zr is superior to that of MCrALY alloy, the bond coat is not required for oxidation resistance.

  9. Technical note - Plasma-sprayed ceramic thermal barrier coatings for smooth intermetallic alloys

    NASA Technical Reports Server (NTRS)

    Miller, R. A.; Doychak, J.

    1992-01-01

    A new approach for plasma spray deposition of ceramic thermal barrier coatings directly to smooth substrates is described. Ceramic thermal barrier coatings were directly applied to substrates that had been coated with low-pressure plasma sprayed NiCrAlY bond coats and then centerless ground to simulate a smooth oxidation-resistant substrate. As the high-temperature oxidation behavior of NiAl+Zr is superior to that of MCrALY alloy, the bond coat is not required for oxidation resistance.

  10. Two feasible approaches to enhance the wear behaviors of NiCrBSi coating in atmosphere and aqueous environments

    NASA Astrophysics Data System (ADS)

    Ye, Yuwei; Wang, Chunting; Zheng, Wenru; Xiong, Wei; Wang, Yongxin; Li, Xiaogang

    2017-09-01

    NiCrBSi coating was deposited successfully on the surface of 316 stainless steel substrate by means of plasma spraying. The microstructures and mechanical property were analyzed by scanning electron microscopy, x-ray diffraction, and a Vickers hardness tester. The wear performances of the coatings sliding against the GCr15 ball under ambient air and water conditions were investigated, and two feasible approaches (tungsten carbide (WC)-doping and heat treatment) were used to improve the tribological performance. Results showed that the hardness of the NiCrBSi coating increased by 12.5% and 28.5% and the porosity decreased by 26.1% and 47.8%, respectively, after WC-doping and heat treatment. During dry friction, the friction coefficient and wear rate of the NiCrBSi coating were about 0.47 and 1.4  ×  10‑5 mm3 N‑1 m‑1, respectively. These values were higher than those obtained on other coatings. In water conditions, all coatings showed a lower friction and wear rate than that in ambient air, which was as a result of the lubrication effect of water. Significantly, with WC-doping and heat treatment, the friction coefficients of both coatings were about 18.5% and 36.7%, respectively, lower than that of the NiCrBSi coating. Furthermore, the wear rates of both coatings were about 20% and 70%, respectively, lower than that of the NiCrBSi coating.

  11. Surface modification of high temperature iron alloys

    DOEpatents

    Park, Jong-Hee

    1995-01-01

    A method and article of manufacture of a coated iron based alloy. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700.degree. C.-1200.degree. C. to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy.

  12. Surface modification of high temperature iron alloys

    DOEpatents

    Park, J.H.

    1995-06-06

    A method and article of manufacture of a coated iron based alloy are disclosed. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700--1200 C to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy. 13 figs.

  13. Effect of the scanning speed on microstructural evolution and wear behaviors of laser cladding NiCrBSi composite coatings

    NASA Astrophysics Data System (ADS)

    Chen, J. L.; Li, J.; Song, R.; Bai, L. L.; Shao, J. Z.; Qu, C. C.

    2015-09-01

    Laser cladding composite coatings were fabricated on the surface of the Ti6Al4V substrate by fiber laser cladding the NiCrBSi alloy powder. The influences of scanning speed on the dilution rate and microstructure of the coatings were investigated in detail by X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). Combined with the analyses of microhardness and fracture toughness, the wear behaviors of the coatings obtained at different scanning speeds were revealed. Results indicated that the dilution rates of the coatings were similar (about 64.23%) with variations in scanning speed ranging from 5 mm/s to 15 mm/s. An abrupt decrease in dilution rate (37.06%) was observed at the scanning speed of 20 mm/s. Microstructural observation showed that the blocky TiB2 and the cellular dendrite TiC particles were uniformly dispersed in the TiNi-Ti2Ni dual-phase intermetallic compound matrix at scanning speeds of 5-15 mm/s. When the scanning speed was further increased to 20 mm/s, the stripe-shaped CrB, gray irregular-shaped Cr3C2 and black blocky TiC particles uniformly dispersed in the γ(Ni) matrix were synthesized in situ. The particles became finer with the increase in scanning speed. The average microhardness of the coating (1026.5 HV0.2) at the scanning speed of 20 mm/s was enhanced significantly compared with that of the other three coatings (about 886.4 HV0.2). The lowest average friction coefficient (about 0.371) was obtained at the scanning speed of 20 mm/s and was relatively stable with the change in sliding time. The lowest wear loss of the coating was also obtained at the scanning speed of 20 mm/s. Analyses of the worn surfaces showed that the coating prepared at the scanning speed of 20 mm/s was in good condition because of its excellent combination of resistance to micro-cutting and brittle debonding. Comparatively speaking, the coating produced at the scanning speed of 20 mm

  14. Polymorphism in a high-entropy alloy

    DOE PAGES

    Zhang, Fei; Wu, Yuan; Lou, Hongbo; ...

    2017-06-01

    Polymorphism, which describes the occurrence of different lattice structures in a crystalline material, is a critical phenomenon in materials science and condensed matter physics. Recently, configuration disorder was compositionally engineered into single lattices, leading to the discovery of high-entropy alloys and high-entropy oxides. For these novel entropy-stabilized forms of crystalline matter with extremely high structural stability, is polymorphism still possible? Here by employing in situ high-pressure synchrotron radiation X-ray diffraction, we reveal a polymorphic transition from face-centred-cubic (fcc) structure to hexagonal-close-packing (hcp) structure in the prototype CoCrFeMnNi high-entropy alloy. The transition is irreversible, and our in situ high-temperature synchrotron radiationmore » X-ray diffraction experiments at different pressures of the retained hcp high-entropy alloy reveal that the fcc phase is a stable polymorph at high temperatures, while the hcp structure is more thermodynamically favourable at lower temperatures. Lastly, as pressure is increased, the critical temperature for the hcp-to-fcc transformation also rises.« less

  15. Polymorphism in a high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Fei; Wu, Yuan; Lou, Hongbo; Zeng, Zhidan; Prakapenka, Vitali B.; Greenberg, Eran; Ren, Yang; Yan, Jinyuan; Okasinski, John S.; Liu, Xiongjun; Liu, Yong; Zeng, Qiaoshi; Lu, Zhaoping

    2017-06-01

    Polymorphism, which describes the occurrence of different lattice structures in a crystalline material, is a critical phenomenon in materials science and condensed matter physics. Recently, configuration disorder was compositionally engineered into single lattices, leading to the discovery of high-entropy alloys and high-entropy oxides. For these novel entropy-stabilized forms of crystalline matter with extremely high structural stability, is polymorphism still possible? Here by employing in situ high-pressure synchrotron radiation X-ray diffraction, we reveal a polymorphic transition from face-centred-cubic (fcc) structure to hexagonal-close-packing (hcp) structure in the prototype CoCrFeMnNi high-entropy alloy. The transition is irreversible, and our in situ high-temperature synchrotron radiation X-ray diffraction experiments at different pressures of the retained hcp high-entropy alloy reveal that the fcc phase is a stable polymorph at high temperatures, while the hcp structure is more thermodynamically favourable at lower temperatures. As pressure is increased, the critical temperature for the hcp-to-fcc transformation also rises.

  16. INCOLOY alloy 803, a cost effective alloy for high temperature service

    SciTech Connect

    Ganesan, P.; Plyburn, J.A.; Tassen, C.S.

    1995-12-31

    INCOLOY alloy 800 was the first of the 800 series of alloys invented by Inco Alloys International in the 1940`s. Because of its excellent oxidation and carburization resistance as well as high temperature creep strength, alloy 800 found uses for many applications such as heat treating hardware, petrochemical processing, home appliances, food processing, industrial heating, super-heater and re-heater tubing and soon became the workhorse material for the chemical processing industries. Alloy 803 has superior resistance to oxidation and carburization without sacrificing mechanical properties. In this paper the history of alloy 800 with introductions of alloys 800H and 800HT and the differences in properties and chemical compositions among them will be described. The development of alloy 803 for petrochemical applications is also covered. The performance of alloy 803 in cyclic oxidation, carburization and sulfidation tests will be presented and compared with several alloys including alloy HPM. The mechanical properties of alloy 803 including room temperature and high temperature tensile data and stress rupture and creep strengths up to 1,093 C (2,000 F) will be presented. The choice of available filler metals and welding electrodes to join alloy 803, using gas metal arc welding and shielded metal arc welding processes, will also be presented.

  17. XPS and electrochemical impedance spectroscopy studies on effects of the porcelain firing process on surface and corrosion properties of two nickel-chromium dental alloys.

    PubMed

    Qiu, Jing; Tang, Chun-bo; Zhu, Zhi-jun; Zhou, Guo-xing; Wang, Jie; Yang, Yi; Wang, Guo-ping

    2013-11-01

    The aim of this study was to evaluate the effects of a simulated porcelain firing process on the surface, corrosion behavior and cell culture response of two nickel-chromium (Ni-Cr) dental alloys. A Be-free alloy and a Be-containing alloy were tested. Before porcelain firing, as-cast specimens were examined for surface composition using X-ray photoelectron spectroscopy and metallurgical phases using X-ray diffraction. Corrosion behaviors were evaluated using electrochemical impedance spectroscopy. 3T3 fibroblasts were cultured and exposed indirectly to specimens. MTT assays were counted after 3 and 6 days. The cell culture mediums exposed to specimens were analyzed for metal ion release. After porcelain firing, similar specimens were examined for the same properties. In both as-cast and fired conditions, the Be-free Ni-Cr alloy showed significantly more resistance to corrosion than the Be-containing Ni-Cr alloy, which exhibited BeNi phase. After porcelain firing, the corrosion resistance of the Be-free Ni-Cr alloy decreased statistically, corresponding with evident decreases of Cr and Ni oxides on the alloy surface. Also, the alloy's MTT assay decreased significantly corresponding with an obvious increase of Ni-ion release after the firing. For the Be-containing Ni-Cr alloy, the firing process led to increases of surface oxides and metallic Be, while its corrosion resistance and cell culture response were not significantly changed after porcelain firing. The results suggested that the corrosion resistance and biocompatibility of the Be-free Ni-Cr alloy decreased after porcelain firing, whereas the firing process had little effect on the same properties of the Be-containing Ni-Cr alloy.

  18. The effect of plating on magnetron sputtering: Residual stress and scratch behavior of Au/NiCr/Ta multi-layers

    NASA Astrophysics Data System (ADS)

    Tang, Wu; Weng, Xiaolong; Deng, Longjiang; Xu, Kewei

    2006-12-01

    Au/NiCr/Ta multi-layers were deposited on Al2O3 substrate by magnetron sputtering and plating. The effect of plating technique on magnetron sputtering film in residual stress, crystal orientation and scratch resistance behavior was investigated. The all magnetron sputtering and plating films were highly textured with dominant Au-(1 1 1) orientation or a mixture of Au-(1 1 1) and Au-(2 0 0) orientation and the (1 1 1)/(2 0 0) intensity ratio were increased after plating. The residual stress in magnetron sputtering films at different substrate temperature was tensile stress with 155-400 MPa and it decreased approximately to 50 MPa after plating. The scratch resistance could be affected by the film thickness, and it increased approximately linearly with the increase of the thickness of metallic films after plating.

  19. Peel strength of sputtered FCCL(Flexible Copper Clad Laminate) using Ar:O2 mixed gas preprocessing and a Ni-Cr seed layer

    NASA Astrophysics Data System (ADS)

    Ahn, Woo-Young; Jang, Joong Soon

    2014-07-01

    The PI surface was modified with ion beams in a vacuum chamber to increase the surface area. A two-way Design of Experiments ("DOE") was performed by varying the DC power and changing the proportion of O2 gas with respect to the Ar reactive gas and measuring the peel strength between the PI layer and the plated Cu layer. The results showed that increasing the voltage level and applying mixed Ar-O2 gas makes the PI surface substantially rough, which increases the Van der Waals force as well as the chemical bonding strength. Using the oxygen gas makes the amorphous structure in the Cu layer sputtered. However, Cu plating with a high electrical current may remedy this, resulting in a good crystalline direction. It was also found that reducing the proportion of Cr in the Ni-Cr seed layer incurs a great decrease in the peel strength after the reflow process, although it requires just one etching.

  20. Study of the influence of morphology and strength of interphase boundaries on the integral mechanical properties of NiCr-TiC composite

    NASA Astrophysics Data System (ADS)

    Eremina, Galina M.; Smolin, Alexey Yu.; Shilko, Evgeny V.; Psakhie, Sergey G.

    2016-11-01

    Sintered metal-ceramic materials are characterized by high mechanical and tribological properties. A key element of the internal structure of the metal-ceramic composites which have an important, and in many cases, a decisive influence on the integral mechanical properties of these materials is the interphase boundary. In this paper, based on numerical simulation we show the influence of morphology and strength properties of interfaces for integral mechanical properties of the dispersion-reinforced composite NiCr-TiC (50 : 50). Computer simulation results indicate that the phase boundary significantly contributes to the integral mechanical characteristics of a composite material and to the nature of the initiation and development of cracks.

  1. Design of refractory high-entropy alloys

    DOE PAGES

    Gao, M. C.; Carney, C. S.; Dogan, O. N.; ...

    2015-09-15

    Here, this report presents a design methodology for refractory high-entropy alloys with a body-centered cubic (bcc) structure using select empirical parameters (i.e., enthalpy of mixing, atomic size difference, Ω-parameter, and electronegativity difference) and CALPHAD approach. Sixteen alloys in equimolar compositions ranging from quinary to ennead systems were designed with experimental verification studies performed on two alloys using x-ray diffraction, energy-dispersive spectroscopy, and scanning electron microscopy. Two bcc phases were identified in the as-cast HfMoNbTaTiVZr, whereas multiple phases formed in the as-cast HfMoNbTaTiVWZr. Observed elemental segregation in the alloys qualitatively agrees with CALPHAD prediction. Comparisons of the thermodynamic mixing properties formore » liquid and bcc phases using the Miedema model and CALPHAD are presented. This study demonstrates that CALPHAD is more effective in predicting HEA formation than empirical parameters, and new single bcc HEAs are suggested: HfMoNbTiZr, HfMoTaTiZr, NbTaTiVZr, HfMoNbTaTiZr, HfMoTaTiVZr, and MoNbTaTiVZr.« less

  2. Design of Refractory High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Gao, M. C.; Carney, C. S.; Doğan, Ö. N.; Jablonksi, P. D.; Hawk, J. A.; Alman, D. E.

    2015-11-01

    This report presents a design methodology for refractory high-entropy alloys with a body-centered cubic (bcc) structure using select empirical parameters (i.e., enthalpy of mixing, atomic size difference, Ω-parameter, and electronegativity difference) and CALPHAD approach. Sixteen alloys in equimolar compositions ranging from quinary to ennead systems were designed with experimental verification studies performed on two alloys using x-ray diffraction, energy-dispersive spectroscopy, and scanning electron microscopy. Two bcc phases were identified in the as-cast HfMoNbTaTiVZr, whereas multiple phases formed in the as-cast HfMoNbTaTiVWZr. Observed elemental segregation in the alloys qualitatively agrees with CALPHAD prediction. Comparisons of the thermodynamic mixing properties for liquid and bcc phases using the Miedema model and CALPHAD are presented. This study demonstrates that CALPHAD is more effective in predicting HEA formation than empirical parameters, and new single bcc HEAs are suggested: HfMoNbTiZr, HfMoTaTiZr, NbTaTiVZr, HfMoNbTaTiZr, HfMoTaTiVZr, and MoNbTaTiVZr.

  3. Design of refractory high-entropy alloys

    SciTech Connect

    Gao, M. C.; Carney, C. S.; Dogan, O. N.; Jablonksi, P. D.; Hawk, J. A.; Alman, D. E.

    2015-09-15

    Here, this report presents a design methodology for refractory high-entropy alloys with a body-centered cubic (bcc) structure using select empirical parameters (i.e., enthalpy of mixing, atomic size difference, Ω-parameter, and electronegativity difference) and CALPHAD approach. Sixteen alloys in equimolar compositions ranging from quinary to ennead systems were designed with experimental verification studies performed on two alloys using x-ray diffraction, energy-dispersive spectroscopy, and scanning electron microscopy. Two bcc phases were identified in the as-cast HfMoNbTaTiVZr, whereas multiple phases formed in the as-cast HfMoNbTaTiVWZr. Observed elemental segregation in the alloys qualitatively agrees with CALPHAD prediction. Comparisons of the thermodynamic mixing properties for liquid and bcc phases using the Miedema model and CALPHAD are presented. This study demonstrates that CALPHAD is more effective in predicting HEA formation than empirical parameters, and new single bcc HEAs are suggested: HfMoNbTiZr, HfMoTaTiZr, NbTaTiVZr, HfMoNbTaTiZr, HfMoTaTiVZr, and MoNbTaTiVZr.

  4. High-strength iron aluminide alloys

    SciTech Connect

    McKamey, C.G.; Marrero-Santos, Y.; Maziasz, P.J.

    1995-06-01

    Past studies have shown that binary Fe{sub 3}Al possesses low creep-rupture strength compared to many other alloys, with creep-rupture lives of less than 5 h being reported for tests conducted at 593{degrees}C and 207 MPa. The combination of poor creep resistance and low room-temperature tensile density due to a susceptibility to environmentally-induced dynamic hydrogen embrittlement has limited use of these alloys for structural applications, despite their excellent corrosion properties. Improvements in room temperature tensile ductility have been realized mainly through alloying effects, changes in thermomechanical processing to control microstructure, and by control of the specimen`s surface condition. Ductilities of 10-20% and tensile yield strengths as high as 500 MPa have been reported. In terms of creep-rupture strength, small additions of Mo, Nb, and Zr have produced significant improvements, but at the expense of weldability and room-temperature tensile ductility. Recently an alloy containing these additions, designated FA-180, was shown to exhibit a creep-rupture life of over 2000 h after a heat treatment of 1 h at 1150{degrees}C. This study presents the results of creep-rupture tests at various test temperatures and stresses and discusses the results as part of our effort to understand the strengthening mechanisms involved with heat treatment at 1150{degrees}C.

  5. Microstructure and properties of laser-borided Inconel 600-alloy

    NASA Astrophysics Data System (ADS)

    Kulka, M.; Dziarski, P.; Makuch, N.; Piasecki, A.; Miklaszewski, A.

    2013-11-01

    Nickel-based superalloys are used extensively for a variety of industrial applications involving high temperatures and aggressive environments. However, under conditions of appreciable mechanical wear (adhesive or abrasive), these materials have to be distinguished by suitable wear protection. The diffusion boronizing is the thermo-chemical treatment, which improves the tribological properties of nickel and its alloys. Nevertheless, the long duration of this process is necessary in order to obtain the layers of the thickness up to about 100 μm. Instead of the diffusion process, in this study the laser boriding is used for producing boride layer on Inconel 600-alloy. During the laser alloying, the external cylindrical surface of base material is coated by paste, including amorphous boron. Then the surface is re-melted by a laser beam. The high overlapping of multiple laser tracks (86%) causes the formation of uniform laser-alloyed layer in respect of the thickness. Laser re-melted zone, heat-affected zone and the substrate characterize the microstructure. In the re-melted zone, the three areas are observed: compact borides zone consisting of nickel, chromium and iron borides (close to the surface), zone of increased percentage of Ni-Cr-Fe-matrix (appearing in the greater distance from the surface) and zone of dominant Ni-Cr-Fe-matrix percentage (at the end of the layer). The hardness obtained is comparable to that-obtained in case of diffusion boriding. Simultaneously, the laser-borided layers are significantly thicker (about 346 or 467 μm depending on the laser power used). The significant increase in their abrasive wear resistance is observed. The wear intensity factors, as well as the relative mass loss of the laser-borided samples, are ten times smaller in comparison with untreated Inconel 600-alloy.

  6. Development of a Brazing Alloy for the Mechanically Alloyed High Temperature Sheet Material INCOLOY Alloy MA 956.

    DTIC Science & Technology

    1981-09-01

    well established that joining these alloys by conventional fusion welding techniques has presented problems, especially in achieving good quality high...temperature joint properties, mainly because of agglomeration of the dispersoid in the weld bead. Brazing, diffusion bonding and transient liquid...produced mechanically alloyed iron based sheet material, INQ)LOY alloy MA956, has excellent high temperature strength and corrosion resistance and has

  7. Hydrogen dominant metallic alloys: high temperature superconductors?

    PubMed

    Ashcroft, N W

    2004-05-07

    The arguments suggesting that metallic hydrogen, either as a monatomic or paired metal, should be a candidate for high temperature superconductivity are shown to apply with comparable weight to alloys of metallic hydrogen where hydrogen is a dominant constituent, for example, in the dense group IVa hydrides. The attainment of metallic states should be well within current capabilities of diamond anvil cells, but at pressures considerably lower than may be necessary for hydrogen.

  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. Laser Brazing of High Temperature Braze Alloy

    NASA Technical Reports Server (NTRS)

    Gao, Y. P.; Seaman, R. F.; McQuillan, T. J.; Martiens, R. F.

    2000-01-01

    The Space Shuttle Main Engine (SSME) consists of 1080 conical tubes, which are furnace brazed themselves, manifolds, and surrounding structural jacket making almost four miles of braze joints. Subsequent furnace braze cycles are performed due to localized braze voids between the coolant tubes. SSME nozzle experiences extremely high heat flux (180 mW/sq m) during hot fire. Braze voids between coolant tubes may result in hot combustion gas escape causing jacket bulges. The nozzle can be disqualified for flight or result in mission failure if the braze voids exceed the limits. Localized braze processes were considered to eliminate braze voids, however, damage to the parent materials often prohibited use of such process. Being the only manned flight reusable rocket engine, it has stringent requirement on the braze process. Poor braze quality or damage to the parent materials limits the nozzle service life. The objective of this study was to develop a laser brazing process to provide quality, localized braze joints without adverse affect on the parent materials. Gold (Au-Cu-Ni-Pd-Mn) based high temperature braze alloys were used in both powder and wire form. Thin section iron base superalloy A286 tube was used as substrate materials. Different Laser Systems including CO2 (10.6 micrometers, 1kW), ND:YAG (1.06 micrometers, 4kW). and direct diode laser (808nm. 150W) were investigated for brazing process. The laser process variables including wavelength. laser power, travel speed and angle of inclination were optimized according to bead geometry and braze alloy wetting at minimum heat input level, The properties of laser brazing were compared to that of furnace brazing. Microhardness profiles were used for braze joint property comparison between laser and furnace brazing. The cooling rate of laser brazing was compared to furnace brazing based on secondary dendritic arm spacing, Both optical and Scanning Electron Microscope (SEM) were used to evaluate the microstructures of

  10. Laser Brazing of High Temperature Braze Alloy

    NASA Technical Reports Server (NTRS)

    Gao, Y. P.; Seaman, R. F.; McQuillan, T. J.; Martiens, R. F.

    2000-01-01

    The Space Shuttle Main Engine (SSME) consists of 1080 conical tubes, which are furnace brazed themselves, manifolds, and surrounding structural jacket making almost four miles of braze joints. Subsequent furnace braze cycles are performed due to localized braze voids between the coolant tubes. SSME nozzle experiences extremely high heat flux (180 mW/sq m) during hot fire. Braze voids between coolant tubes may result in hot combustion gas escape causing jacket bulges. The nozzle can be disqualified for flight or result in mission failure if the braze voids exceed the limits. Localized braze processes were considered to eliminate braze voids, however, damage to the parent materials often prohibited use of such process. Being the only manned flight reusable rocket engine, it has stringent requirement on the braze process. Poor braze quality or damage to the parent materials limits the nozzle service life. The objective of this study was to develop a laser brazing process to provide quality, localized braze joints without adverse affect on the parent materials. Gold (Au-Cu-Ni-Pd-Mn) based high temperature braze alloys were used in both powder and wire form. Thin section iron base superalloy A286 tube was used as substrate materials. Different Laser Systems including CO2 (10.6 micrometers, 1kW), ND:YAG (1.06 micrometers, 4kW). and direct diode laser (808nm. 150W) were investigated for brazing process. The laser process variables including wavelength. laser power, travel speed and angle of inclination were optimized according to bead geometry and braze alloy wetting at minimum heat input level, The properties of laser brazing were compared to that of furnace brazing. Microhardness profiles were used for braze joint property comparison between laser and furnace brazing. The cooling rate of laser brazing was compared to furnace brazing based on secondary dendritic arm spacing, Both optical and Scanning Electron Microscope (SEM) were used to evaluate the microstructures of

  11. A Study of Pack Aluminizing Process for NiCrAlY Coatings Using Response Surface Methodology

    NASA Astrophysics Data System (ADS)

    Gao, Feng; Huang, Xiao; Liu, Rong; Yang, Qi

    2014-01-01

    Aluminizing process is widely used to provide additional Al deposition onto superalloy surface for enhanced oxidation and corrosion resistance. In this research, an aluminizing process—pack cementation process, is used to deposit Al onto the surface of NiCrAlY coatings for increasing environmental protection. The experiment is designed using Box-Behnken approach, in which three parameters, the Al content, Ni content of the pack powder, and the temperature of the process, are selected as factors; and the thickness and Al/Ni ratio of the coatings are selected as responses. The effects of the factors on the responses are analyzed and modeled empirically. It is found that these empirical models correlate well with the results from additional sets of experiment. These models can be used to produce aluminized NiCrAlY coatings with specific thicknesses and Al/Ni ratios.

  12. 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.

  13. 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

  14. 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.

  15. 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

    2016-01-11

    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.

  16. 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.

  17. Advanced alloy design technique: High temperature cobalt base superalloy

    NASA Technical Reports Server (NTRS)

    Dreshfield, R. L.; Freche, J. C.; Sandrock, G. D.

    1972-01-01

    Advanced alloy design technique was developed for treating alloys that will have extended life in service at high temperature and intermediate temperatures. Process stabilizes microstructure of the alloy by designing it so that compound identified with embrittlement is eliminated or minimized. Design process is being used to develop both nickel and cobalt-base superalloys.

  18. Effect of Metal Primers on Bond Strength of a Composite Resin to Nickel-Chrome Metal Alloy.

    PubMed

    Nima, Gabriel; Ferreira, Paulo Vitor Campos; Paula, Andreia Bolzan de; Consani, Simonides; Giannini, Marcelo

    2017-01-01

    This study evaluated the effects of three metal primers and one multi-mode adhesive system on the shear bond strength (SBS) of a flowable composite resin to nickel-chrome metal alloy (Ni-Cr). Ninety plates were cast from Ni-Cr and divided in nine groups (n=10). The surfaces were sandblasted with Al2O3 and primed with three adhesive primers: Alloy Primer (AP), Universal Primer (TP) and RelyX Ceramic Primer (CP), and a multi-mode adhesive (Scotchbond Universal, SU). The Adper Single Bond Plus (SB) and SU adhesives were also combined with adhesive primers. Control group did not have any surface treatment. The groups were: AP, AP+SB, AP+SU, TP+SB, TP+SU, CP+SB, CP+SU and SU. Composite cylinders were built on alloy surface. After 24 h, half the specimens were subjected to SBS and the other half to thermal cycling before testing. Data were analyzed by two-way ANOVA and Tukey's test (a=0.05). Failure modes were assessed by SEM observation. Higher SBS were obtained with AP and TP combined with adhesives at 24 h and the lowest one for control group. Thermocycling reduced SBS for AP, CP+SU and SU. Combination between TP and SU resulted in the highest SBS after the thermocycling. TP groups showed all types of failures and high incidence of mixed failures. The use of AP and UP metal primers before application of SU and SB adhesive systems increased the SBS of composite to Ni-Cr. These combinations between metal primers and adhesives had the highest SBS after thermocycling.

  19. 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.

  20. Ordering Transformations in High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Singh, Prashant; Johnson, Duane D.

    The high-temperature disordered phase of multi-component alloys, including high-entropy alloys (HEA), generally must experience segregation or else passes through partially-ordered phases to reach the low-temperature, fully-ordered phase. Our first-principles KKR-CPA-based atomic short-range ordering (SRO) calculations (analyzed as concentration-waves) reveal the competing partially and fully ordered phases in HEA, and these phases can be then directly assessed from KKR-CPA results in larger unit cells [Phys. Rev. B 91, 224204 (2015)]. For AlxCrFeNiTi0.25, Liu et al. [J Alloys Compd 619, 610 (2015)] experimentally find FCC+BCC coexistence that changes to BCC with increasing Al (x from 0-to-1), which then exhibits a partially-ordered B2 at low temperatures. CALPHAD (Calculation of Phase Diagrams) predicts a region with L21+B2 coexistence. From KKR-CPA calculations, we find crossover versus Al from FCC+BCC coexistence to BCC, as observed, and regions for partially-order B2+L21 coexistence, as suggest by CALPHAD. Our combined first-principles KKR-CPA method provides a powerful approach in predicting SRO and completing long-range order in HEA and other complex alloys. Supported by the U.S. DOE, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division. Work was performed at Ames Laboratory, which is operated by Iowa State University for the U.S. DOE under Contract #DE-AC02-07CH11358.

  1. The Effect of Hydrogen Annealing on the Impurity Content of Alumina-Forming Alloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    2000-01-01

    Previously, the effect of hydrogen annealing on increasing the adhesion of Al2O3 scales had been related to the effective desulfurization that occurred during this process. The simultaneous reduction of other impurities has now been re-examined for up to 20 impurity elements in the case of five different alloys (NiCrAl, FeCrAl, PWA 1480, Rene'142, and Rene'N5). Hydrogen annealing produced measurable reductions in elemental concentration for B, C, Na, Mg, P, K, Sr, or Sn in varying degrees for at least one and up to three of these alloys. No single element was reduced by hydrogen annealing for all the alloys except sulfur. In many cases spalling occurred at low levels of these other impurities, while in other cases the scales were adherent at high levels of the impurities. No impurity besides sulfur was strongly correlated with adhesion.

  2. Improved high pressure turbine shroud

    NASA Technical Reports Server (NTRS)

    Bessen, I. I.; Rigney, D. V.; Schwab, R. C.

    1977-01-01

    A new high pressure turbine shroud material has been developed from the consolidation of prealloyed powders of Ni, Cr, Al and Y. The new material, a filler for cast turbine shroud body segments, is called Genaseal. The development followed the identification of oxidation resistance as the primary cause of prior shroud deterioration, since conversion to oxides reduces erosion resistance and increases spalling under thermal cycled engine conditions. The NICrAlY composition was selected in preference to NIAL and FeCRALY alloys, and was formulated to a prescribed density range that offers suitable erosion resistance, thermal conductivity and elastic modulus for improved behavior as a shroud.

  3. A Promising New Class of High-Temperature Alloys: Eutectic High-Entropy Alloys

    PubMed Central

    Lu, Yiping; Dong, Yong; Guo, Sheng; Jiang, Li; Kang, Huijun; Wang, Tongmin; Wen, Bin; Wang, Zhijun; Jie, Jinchuan; Cao, Zhiqiang; Ruan, Haihui; Li, Tingju

    2014-01-01

    High-entropy alloys (HEAs) can have either high strength or high ductility, and a simultaneous achievement of both still constitutes a tough challenge. The inferior castability and compositional segregation of HEAs are also obstacles for their technological applications. To tackle these problems, here we proposed a novel strategy to design HEAs using the eutectic alloy concept, i.e. to achieve a microstructure composed of alternating soft fcc and hard bcc phases. As a manifestation of this concept, an AlCoCrFeNi2.1 (atomic portion) eutectic high-entropy alloy (EHEA) was designed. The as-cast EHEA possessed a fine lamellar fcc/B2 microstructure, and showed an unprecedented combination of high tensile ductility and high fracture strength at room temperature. The excellent mechanical properties could be kept up to 700°C. This new alloy design strategy can be readily adapted to large-scale industrial production of HEAs with simultaneous high fracture strength and high ductility. PMID:25160691

  4. A promising new class of high-temperature alloys: eutectic high-entropy alloys.

    PubMed

    Lu, Yiping; Dong, Yong; Guo, Sheng; Jiang, Li; Kang, Huijun; Wang, Tongmin; Wen, Bin; Wang, Zhijun; Jie, Jinchuan; Cao, Zhiqiang; Ruan, Haihui; Li, Tingju

    2014-08-27

    High-entropy alloys (HEAs) can have either high strength or high ductility, and a simultaneous achievement of both still constitutes a tough challenge. The inferior castability and compositional segregation of HEAs are also obstacles for their technological applications. To tackle these problems, here we proposed a novel strategy to design HEAs using the eutectic alloy concept, i.e. to achieve a microstructure composed of alternating soft fcc and hard bcc phases. As a manifestation of this concept, an AlCoCrFeNi2.1 (atomic portion) eutectic high-entropy alloy (EHEA) was designed. The as-cast EHEA possessed a fine lamellar fcc/B2 microstructure, and showed an unprecedented combination of high tensile ductility and high fracture strength at room temperature. The excellent mechanical properties could be kept up to 700°C. This new alloy design strategy can be readily adapted to large-scale industrial production of HEAs with simultaneous high fracture strength and high ductility.

  5. Study of high performance alloy electroforming

    NASA Technical Reports Server (NTRS)

    Malone, G. A.

    1985-01-01

    The nickel-manganese experimental electrolyte was hydrogen peroxide treated and carbon purified for removal of residual sodium saccharin and related organic decomposition products from the plating of previous test panels. The saccharin additive was used to reduce stress where high concentrations of manganese and high pulse peak current densities were used. A large quantity of nickel-manganese alloy plates containing 0.35 to 0.40 percent by weight manganese was electroformed for testing to supply data for a mechanical property data table. The aluminum billet required for the machining of the subscale SSME main combustion chamber was acquired.

  6. Solid state welding processes for an oxide dispersion strengthened nickel-chromium-aluminum alloy

    NASA Technical Reports Server (NTRS)

    Moore, T. J.

    1975-01-01

    Solid-state welding processes were evaluated for joining TD-NiCrAl (Ni-16Cr-4Al-2ThO2) alloy sheet. Both hot-press and resistance spot welding techniques were successfully applied in terms of achieving grain growth across the bond line. Less success was achieved with a resistance seam welding process. In stress-rupture shear and tensile shear tests of lap joints at 1100 C, most failures occurred in the parent material, which indicates that the weld quality was good and that the welds were not a plane of weakness. The overall weld quality was not as good as previously attained with TD-NiCr, probably because the presence of alumina at the faying surfaces and the developmental TD-NiCrAl sheet, which was not of the quality of the TD-NiCr sheet in terms of surface flatness and dimensional control.

  7. Several braze filler metals for joining an oxide-dispersion-strengthened nickel-chromium-aluminum alloy

    NASA Technical Reports Server (NTRS)

    Gyorgak, C. A.

    1975-01-01

    An evaluation was made of five braze filler metals for joining an aluminum-containing oxide dispersion-strengthened (ODS) alloy, TD-NiCrAl. All five braze filler metals evaluated are considered suitable for joining TD-NiCrAl in terms of wettability and flow. Also, the braze alloys appear to be tolerant of slight variations in brazing procedures since joints prepared by three sources using three of the braze filler metals exhibited similar brazing characteristics and essentially equivalent 1100 C stress-rupture properties in a brazed butt-joint configuration. Recommendations are provided for brazing the aluminum-containing ODS alloys.

  8. Microstructure and wear behavior of γ/Al 4C 3/TiC/CaF 2 composite coating on γ-TiAl intermetallic alloy prepared by Nd:YAG laser cladding

    NASA Astrophysics Data System (ADS)

    Liu, Xiu-Bo; Shi, Shi-Hong; Guo, Jian; Fu, Ge-Yan; Wang, Ming-Di

    2009-03-01

    As a further step in obtaining high performance elevated temperature self-lubrication anti-wear composite coatings on TiAl alloy, a novel Ni-P electroless plating method was adopted to encapsulate the as-received CaF 2 in the preparation of precursor NiCr-Cr 3C 2-CaF 2 mixed powders with an aim to decrease its mass loss and increase its compatibility with the metal matrix during a Nd:YAG laser cladding. The microstructure of the coating was examined using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) and the friction and wear behavior of the composite coatings sliding against the hardened 0.45% C steel ring was evaluated using a block-on-ring wear tester at room temperature. It was found that the coating had a unique microstructure consisting of primary dendrites TiC and block Al 4C 3 carbides reinforcement as well as fine isolated spherical CaF 2 solid lubrication particles uniformly dispersed in the NiCrAlTi ( γ) matrix. The good friction-reducing and anti-wear abilities of the laser clad composite coating was suggested to the Ni-P electroless plating and the attendant reduction of mass loss of CaF 2 and the increasing of it's wettability with the NiCrAlTi ( γ) matrix during the laser cladding process.

  9. Hydrogen embrittlement of ultra-pure alloys of the inconel 600 type: Influence of the additions of elements (C, P, Sn, Sb)

    NASA Astrophysics Data System (ADS)

    Cornet, M.; Bertrand, C.; Belo, M. Da Cunha

    1982-01-01

    The mechanical behavior of very high purity nickel base alloys of the Inconel 600 type that were simultaneously charged with hydrogen and deformed in tension was investigated. Experimental results show that this procedure decreases markedly the fracture strain of the pure 76 pct Ni-16 pct Cr-8 pct Fe alloy; cracks are observed after two to four pct elongation, and the fracture is completely intercrystalline. Hydrogen embrittlement appears as an intrinsic property of the Ni-Cr-Fe system in the sense that the grain boundary cohesion decreases when the purity of the alloy increases. The presence of carbon or phosphorus in the alloys increases grain boundary cohesion. The addition of metallic elements such as antimony or tin has relatively little effect on intergranular embrittlement.

  10. Mechanical Properties of High Strength Al-Mg Alloy Sheet

    NASA Astrophysics Data System (ADS)

    Choi, Bong-Jae; Hong, Kyung-Eui; Kim, Young-Jig

    The aim of this research is to develop the high strength Al alloy sheet for the automotive body. For the fabrication Al-Mg alloy sheet, the composition of alloying elements was designed by the properties database and CALPHAD (Calculation Phase Diagram) approach which can predict the phases during solidification using thermodynamic database. Al-Mg alloys were designed using CALPHAD approach according to the high content of Mg with minor alloying elements. After phase predictions by CALPHAD, designed Al-Mg alloys were manufactured. Addition of Mg in Al melts were protected by dry air/Sulphur hexafluoride (SF6) mixture gas which can control the severe Mg ignition and oxidation. After rolling procedure of manufactured Al-Mg alloys, mechanical properties were examined with the variation of the heat treatment conditions.

  11. Unusual Thermal Stability of High-Entropy Alloy Amorphous Structure

    DTIC Science & Technology

    2012-06-20

    1    REPORT Unusual Thermal Stability of High - Entropy Alloy Amorphous Structure Basic research for AOARD 114009 Award No. FA2386-11-1...stability of high - entropy alloy amorphous structure 5a. CONTRACT NUMBER FA23861114009 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Jien-Wei...at least 3 h. If substrate effect could be eliminated, the crystallization temperature would be higher. 15. SUBJECT TERMS high entropy alloys 16

  12. The Effect of Alloy Additions on Superplasticity in Thermomechanically Processed High Magnesium Aluminum-Magnesium Alloys.

    DTIC Science & Technology

    1984-12-01

    AD-Ri55 142 THE EFFECT OF ALLOY ADDITIONS ON SUPERPLASTICITY IN I/2 THERMOMECHANICALLY PR-.(U) NAVAL POSTGRADUATE SCHOOL UNCLSSIIED MONTEREY CA R J...Ln Monterey, California DTr J U N 1985 * THESIS THE EFFECT OF ALLOY ADDITIONS ON SUPERPLASTICITY IN THERMOMECHANICALLY PROCESSED HIGH MAGNESIUM *0...ALUMINUM-MAGNESIUM ALLOYS >by 0 (Richard J. Self December 1984 C-31 Thesis Advisor: Terry McNelley Approved for public release; distribution is unlimited

  13. The effect of hydrogen on the fracture toughness of alloy X-750 at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Symons, Douglas M.

    Ni-Cr-Fe alloys are widely used in pressurized water nuclear reactors (PWR). These alloys are susceptible to stress corrosion cracking (SCC) in PWR environments. There have been numerous mechanisms of crack advance proposed to describe the SCC of the nickel-base alloys in a PWR environment including slip/film rupture/oxidation and hydrogen embrittlement. It has also been suggested that there is not sufficient evidence to implicate hydrogen in the PWR SCC of nickel-base alloys. This program evaluated the effect of hydrogen on the embrittlement of a nickel-base alloy, alloy X-750, at elevated temperatures with a hydrogen concentration typical of what may be developed from the corrosion reaction. Fracture toughness values and the tearing resistance of alloy X-750 were evaluated in hydrogen gas and in air 260°C and 338°C. It was shown that at 260°C and 338°C alloy X-750 was severely embrittled in high pressure hydrogen gas. Further, the fracture morphology changed from predominantly transgranular ductile dimple fracture in air to predominantly intergranular fracture in hydrogen. The fracture morphology in hydrogen was similar to that found for PWR SCC of this material. This work supports a hydrogen-enhanced fracture mechanism contributing to the SCC of nickel-base alloys at elevated temperatures.

  14. High strength uranium-tungsten alloy process

    DOEpatents

    Dunn, Paul S.; Sheinberg, Haskell; Hogan, Billy M.; Lewis, Homer D.; Dickinson, James M.

    1990-01-01

    Alloys of uranium and tungsten and a method for making the alloys. The amount of tungsten present in the alloys is from about 4 wt % to about 35 wt %. Tungsten particles are dispersed throughout the uranium and a small amount of tungsten is dissolved in the uranium.

  15. High strength uranium-tungsten alloys

    DOEpatents

    Dunn, Paul S.; Sheinberg, Haskell; Hogan, Billy M.; Lewis, Homer D.; Dickinson, James M.

    1991-01-01

    Alloys of uranium and tungsten and a method for making the alloys. The amount of tungsten present in the alloys is from about 4 wt % to about 35 wt %. Tungsten particles are dispersed throughout the uranium and a small amount of tungsten is dissolved in the uranium.

  16. High-temperature nickel-brazing alloy

    NASA Technical Reports Server (NTRS)

    Powell, A. H.; Thompson, S. R.

    1970-01-01

    Gold-nickel brazing alloy, with 5 percent indium added to depress the melting point, is used for brazing of nickel-clad silver electrical conductors which operate at temperatures to 1200 deg F. Alloy has low resistivity, requires no flux, and is less corrosive than other gold-nickel, gold-copper alloys.

  17. High-niobium titanium aluminide alloys

    SciTech Connect

    Huang, S.C.

    1992-02-18

    This patent describes an aged niobium modified titanium aluminum alloy, the alloy consisting essentially of titanium, aluminum, and niobium in the following atomic ratio: Ti{sub 48-37}Al{sub 46-49}Nb{sub 6-14}, the alloy having been prepared by ingot metallurgy.

  18. Colorimetric analysis of opaque porcelain fired to different base metal alloys used in metal ceramic restorations.

    PubMed

    Ozcelik, Tuncer Burak; Yilmaz, Burak; Ozcan, Isil; Kircelli, Cem

    2008-03-01

    The popularity of base metal alloys has considerably increased in recent years because of their superior mechanical properties as well as the high cost of noble alloys. However, there is disagreement about their effect on the opaque porcelain color and the color differences among base metal alloys. The purpose of this in vitro study was to determine and compare the influence of various commercially available base metal alloys (excluding titanium-based systems) on the resulting color of opaque porcelain with the use of a colorimetric device. Fourteen different types of Ni-Cr and 3 different types of Co-Cr porcelain bonding alloys were selected with a Au-Pd alloy (V-Delta SF) as the control group for colorimetric measurements and determination of color shift after opaque application. Shade B1 of an opaque porcelain (IPS d.SIGN Opaquer) was applied (0.1 mm) to all specimens (16 mm x 1 mm). The color coordinates of each specimen were measured with a chromameter. The data were displayed in L*, a*, and b* values according to the CIELAB system, and the color differences (DeltaE) between base metal alloys and the control group were calculated. Data were statistically analyzed with 1-way ANOVA (alpha=.05). The ANOVA was followed by Dunnett's multiple comparison test for comparisons with the control group to determine specifically which groups were significantly different from the control group. The L* value of only 1 base metal alloy was significantly different from the control group (P<.001). All base metal alloy groups except 3 had a* values which were significantly different from the control group a* value (P=.001 for Rexillium III, P=.008 for Heracles N, and P<.001 for the remaining 12 alloys), whereas only 3 base metal alloys were not statistically significantly different from the control group in the means of b* values (P<.001). All base metal alloys to which opaque porcelain was applied had significantly different DeltaE values in comparison with the control group (P

  19. Titanium Alloys and Processing for High Speed Aircraft

    NASA Technical Reports Server (NTRS)

    Brewer, William D.; Bird, R. Keith; Wallace, Terryl A.

    1996-01-01

    Commercially available titanium alloys as well as emerging titanium alloys with limited or no production experience are being considered for a variety of applications to high speed commercial aircraft structures. A number of government and industry programs are underway to improve the performance of promising alloys by chemistry and/or processing modifications and to identify appropriate alloys and processes for specific aircraft structural applications. This paper discusses some of the results on the effects of heat treatment, service temperatures from - 54 C to +177 C, and selected processing on the mechanical properties of several candidate beta and alpha-beta titanium alloys. Included are beta alloys Timetal 21S, LCB, Beta C, Beta CEZ, and Ti-10-2-3 and alpha-beta alloys Ti-62222, Ti-6242S, Timetal 550, Ti-62S, SP-700, and Corona-X. The emphasis is on properties of rolled sheet product form and on the superplastic properties and processing of the materials.

  20. Microstructure and magnetic properties of mechanically alloyed FeSiBAlNi (Nb) high entropy alloys

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Zheng, Zhou; Xu, Jing; Wang, Yan

    2014-04-01

    In this paper, the effects of milling duration and composition on the microstructure and magnetic properties of equi-atomic FeSiBAlNi and FeSiBAlNiNb high entropy alloys during mechanical alloying have been investigated using X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, transmission electron microscopy and alternating gradient magnetometry. The amorphous high entropy alloys have been successfully fabricated using the mechanical alloying method. The results show that the Nb addition prolongs the milling time for the formation of the fully FeSiBAlNi amorphous phase and decreases the glass forming ability. However, FeSiBAlNiNb amorphous high entropy alloy has the higher thermal stability and heat resisting properties. Moreover, the as-milled FeSiBAlNi(Nb) powders are soft-magnetic materials indicated by their low coercivity. The saturation magnetization of the as-milled FeSiBAlNi(Nb) powders decreases with prolonging of the milling time and shows the lowest value when the amorphous high entropy alloys are formed. It suggests that the as-milled products with solid solution phases show the better soft-magnetic properties than those with fully amorphous phases. The Nb addition does not improve the soft-magnetic properties of the FeSiBAlNi high entropy alloys. Rather, both amorphous high entropy alloys have similar soft-magnetic properties after a long milling time.

  1. High-entropy alloys as high-temperature thermoelectric materials

    SciTech Connect

    Shafeie, Samrand; Guo, Sheng; Hu, Qiang; Fahlquist, Henrik; Erhart, Paul; Palmqvist, Anders

    2015-11-14

    Thermoelectric (TE) generators that efficiently recycle a large portion of waste heat will be an important complementary energy technology in the future. While many efficient TE materials exist in the lower temperature region, few are efficient at high temperatures. Here, we present the high temperature properties of high-entropy alloys (HEAs), as a potential new class of high temperature TE materials. We show that their TE properties can be controlled significantly by changing the valence electron concentration (VEC) of the system with appropriate substitutional elements. Both the electrical and thermal transport properties in this system were found to decrease with a lower VEC number. Overall, the large microstructural complexity and lower average VEC in these types of alloys can potentially be used to lower both the total and the lattice thermal conductivity. These findings highlight the possibility to exploit HEAs as a new class of future high temperature TE materials.

  2. High Strength, Nano-Structured Mg-Al-Zn Alloy

    DTIC Science & Technology

    2011-01-01

    REPORT High strength, nano-structured Mg– Al – Zn alloy 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: The mechanical behavior and microstructure of...Prescribed by ANSI Std. Z39.18 - High strength, nano-structured Mg– Al – Zn alloy Report Title ABSTRACT The mechanical behavior and microstructure of...strength, nano-structured Mg– Al – Zn alloy Block 13: Supplementary Note © 2011 . Published in Materials Science and Engineering, Vol. 528, (54), Ed. 0 (2011

  3. Superplasticity in Thermomechanically Processed High Magnesium Aluminum-Magnesium Alloys.

    DTIC Science & Technology

    1984-03-01

    California DTIC EECTE JL I 1984 THESIS SUPERPLASTICITY IN THERMOMECHANICALLY PROCESSED HIGH MAGNESIUM ALUMINUM-MAGNESIUM ALLOYS C:L by CD) John J. Becker...High Magnesium Aluminum- March 1984 Magnesium Alloys S. PERFORMING ORG. REPORT NUMBER 7. AUTHOR(@) S. CONTRACT OR GRANT NUMBER(&) John J. Becker 9...magnesium, aluminum-magnesium alloys were investigated. The thermomechanical processing itself included warm rolling at 300°C to 94% reduction

  4. Phase separation in NiCrN coatings induced by N2 addition in the gas phase: A way to generate magnetic thin films by reactive sputtering of a non-magnetic NiCr target

    NASA Astrophysics Data System (ADS)

    Luciu, I.; Duday, D.; Choquet, P.; Perigo, E. A.; Michels, A.; Wirtz, T.

    2016-12-01

    Magnetic coatings are used for a lot of applications from data storage in hard discs, spintronics and sensors. Meanwhile, magnetron sputtering is a process largely used in industry for the deposition of thin films. Unfortunately, deposition of magnetic coatings by magnetron sputtering is a difficult task due to the screening effect of the magnetic target lowering the magnetic field strength of the magnet positioned below the target, which is used to generate and trap ions in the vicinity of the target surface to be sputtered. In this work we present an efficient method to obtain soft magnetic thin films by reactive sputtering of a non-magnetic target. The aim is to recover the magnetic properties of Ni after dealloying of Ni and Cr due to the selective reactivity of Cr with the reactive nitrogen species generated during the deposition process. The effects of nitrogen content on the dealloying and DC magnetron sputtering (DCMS) deposition processes are studied here. The different chemical compositions, microstructures and magnetic properties of DCMS thin films obtained by sputtering in reactive gas mixtures with different ratios of Ar/N2 from a non-magnetic Ni-20Cr target have been determined. XPS data indicate that the increase of nitrogen content in the films has a strong influence on the NiCr phase decomposition into Ni and CrN, leading to ferromagnetic coatings due to the Ni phase. XRD results show that the obtained Ni-CrN films consist of a metallic fcc cubic Ni phase mixed with fcc cubic CrN. The lattice parameter decreases with the N2 content and reaches the theoretical value of the pure fcc-Ni, when Cr is mostly removed from the Ni-Cr phase. Dealloying of Cr from a Ni80-Cr20 solid solution is achieved in our experimental conditions and the deposition of Ni ferromagnetic coatings embedding CrN from a non-magnetic target is possible with reactive DC magnetron sputtering.

  5. High-temperature cyclic oxidation data. Part 2: Turbine alloys

    NASA Technical Reports Server (NTRS)

    Barrett, Charles A.; Garlick, Ralph G.

    1989-01-01

    Specific-weight-change-versus-time data and x ray diffraction results are presented derived from high temperature cyclic tests on high temperature, high strength nickel-base gamma/gamma prime and cobalt-base turbine alloys. Each page of data summarizes a complete test on a given alloy sample.

  6. High temperature cyclic oxidation data. Part 1: Turbine alloys

    NASA Technical Reports Server (NTRS)

    Barrett, Charles A.; Garlick, Ralph G.; Lowell, Carl E.

    1989-01-01

    Specific-weight-change-versus-time data and x ray diffraction results are presented derived from high temperature cyclic tests on high temperature, high strength nickel-base gamma/gamma prime and cobalt-base turbine alloys. Each page of data summarizes a complete test on a given alloy sample.

  7. Investigation of austenitic alloys for advanced heat recovery and hot gas cleanup systems

    SciTech Connect

    Swindeman, R.W.; Ren, W.

    1996-06-01

    The objective of the research is to provide databases and design criteria to assist in the selection of optimum alloys for construction of components needed to contain process streams in advanced heat recovery and hot-gas cleanup systems. Typical components include: steam line piping and superheater tubing for low emission boilers (600 to 700{degrees}C), heat exchanger tubing for advanced steam cycles and topping cycle systems (650 to 800{degrees}C), foil materials for recuperators, on advanced turbine systems (700 to 750{degrees}C), and tubesheets for barrier filters, liners for piping, cyclones, and blowback system tubing for hot-gas cleanup systems (850 to 1000{degrees}C). The materials being examined fall into several classes, depending on which of the advanced heat recovery concepts is of concern. These classes include martensitic steels for service to 650{degrees}C, lean stainless steels and modified 25Cr-30Ni steels for service to 700{degrees}C, modified 25Cr-20Ni steels for service to 900{degrees}C, and high Ni-Cr-Fe or Ni-Cr-Co-Fe alloys for service to 1000{degrees}C.

  8. 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.

  9. 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.

  10. Alloy development for irradiation performance. Quarterly progress report for period ending December 31, 1979

    SciTech Connect

    Ashdown, B.G.

    1980-04-01

    Progress is reported concerning preparation of a materials handbook for fusion, creep-fatigue of first-wall structural materials, test results on miniature compact tension fracture toughness specimens, austenitic stainless steels, Fe-Ni-Cr alloys, iron-base alloys with long-range crystal structure, ferritic steels, irradiation experiments, corrosion testing, and hydrogen permeation studies. (FS)

  11. Atomic-scale properties of Ni-based FCC ternary, and quaternary alloys

    DOE PAGES

    Tamm, Artur; Aabloo, Alvo; Klintenberg, Mattias; ...

    2015-08-26

    The aim of our study is to characterize some atomic-scale properties of Ni-based FCC multicomponent alloys. For this purpose, we use Monte Carlo method combined with density functional theory calculations to study short-range order (SRO), atomic displacements, electronic density of states, and magnetic moments in equimolar ternary NiCrCo, and quaternary NiCrCoFe alloys. The salient features for the ternary alloy are a negative SRO parameter between Ni Cr and a positive between Cr Cr pairs as well as a weakly magnetic state. For the quaternary alloy we predict negative SRO parameter for Ni Cr and Ni Fe pairs and positive formore » Cr Cr and Fe Fe pairs. Atomic displacements for both ternary and quaternary alloys are negligible. In contrast to the ternary, the quaternary alloy shows a complex magnetic structure. The electronic structure of the ternary and quaternary alloys shows differences near the Fermi energy between a random solid solution and the predicted structure with SRO. Despite that, the calculated EXAFS spectra does not show enough contrast to discriminate between random and ordered structures. Finally, the predicted SRO has an impact on point-defect energetics, electron phonon coupling and thermodynamic functions and thus, SRO should not be neglected when studying properties of these two alloys.« less

  12. Atomic-scale properties of Ni-based FCC ternary, and quaternary alloys

    SciTech Connect

    Tamm, Artur; Aabloo, Alvo; Klintenberg, Mattias; Stocks, Malcolm; Caro, Alfredo

    2015-08-26

    The aim of our study is to characterize some atomic-scale properties of Ni-based FCC multicomponent alloys. For this purpose, we use Monte Carlo method combined with density functional theory calculations to study short-range order (SRO), atomic displacements, electronic density of states, and magnetic moments in equimolar ternary NiCrCo, and quaternary NiCrCoFe alloys. The salient features for the ternary alloy are a negative SRO parameter between Ni Cr and a positive between Cr Cr pairs as well as a weakly magnetic state. For the quaternary alloy we predict negative SRO parameter for Ni Cr and Ni Fe pairs and positive for Cr Cr and Fe Fe pairs. Atomic displacements for both ternary and quaternary alloys are negligible. In contrast to the ternary, the quaternary alloy shows a complex magnetic structure. The electronic structure of the ternary and quaternary alloys shows differences near the Fermi energy between a random solid solution and the predicted structure with SRO. Despite that, the calculated EXAFS spectra does not show enough contrast to discriminate between random and ordered structures. Finally, the predicted SRO has an impact on point-defect energetics, electron phonon coupling and thermodynamic functions and thus, SRO should not be neglected when studying properties of these two alloys.

  13. Protective nitride formation on stainless steel alloys for proton exchange membrane fuel cell bipolar plates

    SciTech Connect

    Yang, Bing; Brady, Michael P; Wang, Heli; Turner, John; More, Karren Leslie; Young, David J; Tortorelli, Peter F; Payzant, E Andrew; Walker, Larry R

    2007-01-01

    Gas nitridation has shown excellent promise to form dense, electrically conductive and corrosion-resistant Cr-nitride surface layers on Ni-Cr base alloys for use as proton exchange membrane fuel cell (PEMFC) bipolar plates. Due to the high cost of nickel, Fe-base bipolar plate alloys are needed to meet the cost targets for many PEMFC applications. Unfortunately, nitridation of Fe-base stainless steel alloys typically leads to internal Cr-nitride precipitation rather than the desired protective surface nitride layer formation, due to the high permeability of nitrogen in these alloys. This paper reports the finding that it is possible to form a continuous, protective Cr-nitride (CrN and Cr{sub 2}N) surface layer through nitridation of Fe-base stainless steel alloys. The key to form a protective Cr-nitride surface layer was found to be the initial formation of oxide during nitridation, which prevented the internal nitridation typically observed for these alloys, and resulted in external Cr-nitride layer formation. The addition of V to the alloy, which resulted in the initial formation of V{sub 2}O{sub 3}-Cr{sub 2}O{sub 3}, was found to enhance this effect, by making the initially formed oxide more amenable to subsequent nitridation. The Cr-nitride surface layer formed on model V-modified Fe-27Cr alloys exhibited excellent corrosion resistance and low interfacial contact resistance under simulated PEMFC bipolar plate conditions.

  14. CORROSION OF HIGH-TEMPERATURE ALLOYS

    SciTech Connect

    John P. Hurley; John P. Kay

    1999-10-01

    Five alloys were tested in the presence of water vapor and water vapor with HCl for 1000 hours using simulated combustion gas. Samples were removed at intervals during each test and measured for determination of corrosion rates. One sample of each alloy was examined with a SEM after the completion of each test. Cumulative corrosion depths were similar for the superstainless alloys. Corrosion for Alloy TP310 roughly doubled. Corrosion for the enhanced stainless alloys changed dramatically with the addition of chlorine. Corrosion for Alloy RA85H increased threefold, whereas Alloy TP347HFG showed an eightfold increase. SEM examination of the alloys revealed that water vapor alone allowed the formation of chromium oxide protective layers on the superstainless alloys. The enhanced stainless alloys underwent more corrosion due to greater attack of sulfur. Iron-rich oxide layers were more likely to form, which do not provide protection from further corrosion. The addition of chlorine further increased the corrosion because of its ability to diffuse through the oxide layers and react with iron. This resulted in a broken, discontinuous, and loose oxide layer that offered less protection. Niobium, although added to aid in creep strength, was found to be detrimental to corrosion resistance. The niobium tended to be concentrated in nodules and was easily attacked through sulfidation, providing conduits for further corrosion deep into the alloy. The alloys that displayed the best corrosion resistance were those which could produce chromium oxide protective layers. The predicted microstructure of all alloys except Alloy HR3C is the same and provided no further information relating to corrosion resistance. No correlation can be found relating corrosion resistance to the quantity of minor austenite-or ferrite-stabilizing elements. Also, there does not appear to be a correlation between corrosion resistance and the Cr:Ni ratio of the alloy. These alloys were tested for their

  15. Mixing and non-stoichiometry in Fe-Ni-Cr-Zn-O spinel compounds: density functional theory calculations.

    PubMed

    Andersson, David A; Stanek, Christopher R

    2013-10-07

    Density functional theory (DFT) calculations have been performed on A(2+)B2(3+)O4(2-) (where A(2+) = Fe, Ni or Zn, and B(3+) = Fe or Cr) spinel oxides in order to determine some of their thermodynamic properties. Mixing energies were calculated for Fe3O4-NiFe2O4, Fe3O4-ZnFe2O4, Fe3O4-FeCr2O4, NiFe2O4-ZnFe2O4, NiFe2O4-NiCr2O4, FeCr2O4-NiCr2O4, FeCr2O4-ZnCr2O4 and ZnCr2O4-ZnFe2O4 pseudo-binaries based on special quasi random (SQS) structures to account for cationic disorder. The results generally agree with available experimental data and the rule that two normal or two inverse spinel compounds easily form solid solutions, while inverse-normal spinel mixtures exhibit positive deviation from solid solution behavior (i.e. immiscibility). Even though the NiFe2O4-NiCr2O4 and Fe3O4-FeCr2O4 systems obey this rule, they exhibit additional features with implications for the corresponding phase diagrams. In addition to mixing enthalpies, non-stoichiometry was also considered by calculating the energies of the relevant defect reactions resulting in A, B and O excess (or deficiency). The DFT calculations predict close to zero or slightly exothermic reactions for both A and B excess in a number of spinel compounds.

  16. High-Strength Low-Alloy (HSLA) Mg-Zn-Ca Alloys with Excellent Biodegradation Performance

    NASA Astrophysics Data System (ADS)

    Hofstetter, J.; Becker, M.; Martinelli, E.; Weinberg, A. M.; Mingler, B.; Kilian, H.; Pogatscher, S.; Uggowitzer, P. J.; Löffler, J. F.

    2014-04-01

    This article deals with the development of fine-grained high-strength low-alloy (HSLA) magnesium alloys intended for use as biodegradable implant material. The alloys contain solely low amounts of Zn and Ca as alloying elements. We illustrate the development path starting from the high-Zn-containing ZX50 (MgZn5Ca0.25) alloy with conventional purity, to an ultrahigh-purity ZX50 modification, and further to the ultrahigh-purity Zn-lean alloy ZX10 (MgZn1Ca0.3). It is shown that alloys with high Zn-content are prone to biocorrosion in various environments, most probably because of the presence of the intermetallic phase Mg6Zn3Ca2. A reduction of the Zn content results in (Mg,Zn)2Ca phase formation. This phase is less noble than the Mg-matrix and therefore, in contrast to Mg6Zn3Ca2, does not act as cathodic site. A fine-grained microstructure is achieved by the controlled formation of fine and homogeneously distributed (Mg,Zn)2Ca precipitates, which influence dynamic recrystallization and grain growth during hot forming. Such design scheme is comparable to that of HSLA steels, where low amounts of alloying elements are intended to produce a very fine dispersion of particles to increase the material's strength by refining the grain size. Consequently our new, ultrapure ZX10 alloy exhibits high strength (yield strength R p = 240 MPa, ultimate tensile strength R m = 255 MPa) and simultaneously high ductility (elongation to fracture A = 27%), as well as low mechanical anisotropy. Because of the anodic nature of the (Mg,Zn)2Ca particles used in the HSLA concept, the in vivo degradation in a rat femur implantation study is very slow and homogeneous without clinically observable hydrogen evolution, making the ZX10 alloy a promising material for biodegradable implants.

  17. 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.

  18. Synthesis Processing of High-Lithium Al-Li Alloys

    DTIC Science & Technology

    1988-06-27

    Li-base alloys suitable for structural applications, with densities 15 to 20 percent lower than 7075 Al. The alloy compositions being investigated...States and Europe. Alloys that offer a 7 to 9 percent decrease in density compared to 7075 Al, with service properties similar to conventional high...large particles substantially influence the deformation behavior due to their non-shearable nature and are therefore desirable for the improvement of

  19. Influence of the casting processing route on the corrosion behavior of dental alloys.

    PubMed

    Galo, Rodrigo; Rocha, Luis Augusto; Faria, Adriana Claudia; Silveira, Renata Rodrigues; Ribeiro, Ricardo Faria; de Mattos, Maria da Gloria Chiarello

    2014-12-01

    Casting in the presence of oxygen may result in an improvement of the corrosion performance of most alloys. However, the effect of corrosion on the casting without oxygen for dental materials remains unknown. The aim of this study was to investigate the influence of the casting technique and atmosphere (argon or oxygen) on the corrosion behavior response of six different dental casting alloys. The corrosion behavior was evaluated by electrochemical measurements performed in artificial saliva for the different alloys cast in two different conditions: arc melting in argon and oxygen-gas flame centrifugal casting. A slight decrease in open-circuit potential for most alloys was observed during immersion, meaning that the corrosion tendency of the materials increases due to the contact with the solution. Exceptions were the Co-based alloys prepared by plasma, and the Co-Cr-Mo and Ni-Cr-4Ti alloys processed by oxidized flame, in which an increase in potential was observed. The amount of metallic ions released into the artificial saliva solution during immersion was similar for all specimens. Considering the pitting potential, a parameter of high importance when considering the fluctuating conditions of the oral environment, Co-based alloys show the best performance in comparison with the Ni-based alloys, independent of the processing route.

  20. High strength ferritic alloy-D53

    DOEpatents

    Hagel, William C.; Smidt, Frederick A.; Korenko, Michael K.

    1977-01-01

    A high strength ferritic alloy is described having from about 0.2% to about 0.8% by weight nickel, from about 2.5% to about 3.6% by weight chromium, from about 2.5% to about 3.5% by weight molybdenum, from about 0.1% to about 0.5% by weight vanadium, from about 0.1% to about 0.5% by weight silicon, from about 0.1% to about 0.6% by weight manganese, from about 0.12% to about 0.20% by weight carbon, from about 0.02% to about 0.1% by weight boron, a maximum of about 0.05% by weight nitrogen, a maximum of about 0.02% by weight phosphorous, a maximum of about 0.02% by weight sulfur, and the balance iron.

  1. Recent Progress in High Entropy Alloy Research

    NASA Astrophysics Data System (ADS)

    MacDonald, B. E.; Fu, Z.; Zheng, B.; Chen, W.; Lin, Y.; Chen, F.; Zhang, L.; Ivanisenko, J.; Zhou, Y.; Hahn, H.; Lavernia, E. J.

    2017-07-01

    Since their discovery in 2004, high-entropy alloys (HEAs) have generated significant interest from the scientific community. Based on a multi-principal element design approach, HEAs are engineered to possess a unique random solid solution (RSS) crystalline structure, in which each of the constituent elements has an equal probability of occupying a given lattice site. Published literature reports that certain HEAs exhibit exceptional chemical, physical, mechanical and functional properties that are attributed to the presence of a RSS phase. Not surprisingly, research on HEAs has begun to expand at an accelerated rate. The scientific and engineering topics being studied include: experimentally measuring various properties in HEA systems, understanding the effect of the RSS on these properties, and developing methods for predicting the formation of RSS phases. Accordingly, the goal of this brief review is to introduce the field of HEAs, discuss their core concepts, highlight exceptional properties, and discuss current design aspects.

  2. Recent Progress in High Entropy Alloy Research

    NASA Astrophysics Data System (ADS)

    MacDonald, B. E.; Fu, Z.; Zheng, B.; Chen, W.; Lin, Y.; Chen, F.; Zhang, L.; Ivanisenko, J.; Zhou, Y.; Hahn, H.; Lavernia, E. J.

    2017-10-01

    Since their discovery in 2004, high-entropy alloys (HEAs) have generated significant interest from the scientific community. Based on a multi-principal element design approach, HEAs are engineered to possess a unique random solid solution (RSS) crystalline structure, in which each of the constituent elements has an equal probability of occupying a given lattice site. Published literature reports that certain HEAs exhibit exceptional chemical, physical, mechanical and functional properties that are attributed to the presence of a RSS phase. Not surprisingly, research on HEAs has begun to expand at an accelerated rate. The scientific and engineering topics being studied include: experimentally measuring various properties in HEA systems, understanding the effect of the RSS on these properties, and developing methods for predicting the formation of RSS phases. Accordingly, the goal of this brief review is to introduce the field of HEAs, discuss their core concepts, highlight exceptional properties, and discuss current design aspects.

  3. High conductivity Be-Cu alloys for fusion reactors

    SciTech Connect

    Lilley, E.A.; Adachi, Takao; Ishibashi, Yoshiki

    1995-09-01

    The optimum material has not yet been identified. This will result in heat from plasma to the first wall and divertor. That is, because of cracks and melting by thermal power and shock. Today, it is considered to be some kinds of copper, alloys, however, for using, it must have high conductivity. And it is also needed another property, for example, high strength and so on. We have developed some new beryllium copper alloys with high conductivity, high strength, and high endurance. Therefore, we are introducing these new alloys as suitable materials for the heat sink in fusion reactors.

  4. High-Throughput Screening Across Quaternary Alloy Composition Space: Oxidation of (AlxFeyNi1-x-y)∼0.8Cr∼0.2.

    PubMed

    Payne, Matthew A; Miller, James B; Gellman, Andrew J

    2016-09-12

    Composition spread alloy films (CSAFs) are commonly used as libraries for high-throughput screening of composition-property relationships in multicomponent materials science. Because lateral gradients afford two degrees of freedom, an n-component CSAF can, in principle, contain any composition range falling on a continuous two-dimensional surface through an (n - 1)-dimensional composition space. However, depending on the complexity of the CSAF gradients, characterizing and graphically representing this composition range may not be straightforward when n ≥ 4. The standard approach for combinatorial studies performed using quaternary or higher-order CSAFs has been to use fixed stoichiometric ratios of one or more components to force the composition range to fall on some well-defined plane in the composition space. In this work, we explore the synthesis of quaternary Al-Fe-Ni-Cr CSAFs with a rotatable shadow mask CSAF deposition tool, in which none of the component ratios are fixed. On the basis of the unique gradient geometry produced by the tool, we show that the continuous quaternary composition range of the CSAF can be rigorously represented using a set of two-dimensional "pseudoternary" composition diagrams. We then perform a case study of (AlxFeyNi1-x-y)∼0.8Cr∼0.2 oxidation in dry air at 427 °C to demonstrate how such CSAFs can be used to screen an alloy property across a continuous two-dimensional subspace of a quaternary composition space. We identify a continuous boundary through the (AlxFeyNi1-x-y)∼0.8Cr∼0.2 subspace at which the oxygen uptake into the CSAF between 1 and 16 h oxidation time increases abruptly with decreasing Al content. The results are compared to a previous study of the oxidation of AlxFeyNi1-x-y CSAFs in dry air at 427 °C.

  5. Magnetocaloric Properties of Fe-Ni-Cr Nanoparticles for Active Cooling

    NASA Astrophysics Data System (ADS)

    Chaudhary, V.; Ramanujan, R. V.

    2016-10-01

    Low cost, earth abundant, rare earth free magnetocaloric nanoparticles have attracted an enormous amount of attention for green, energy efficient, active near room temperature thermal management. Hence, we investigated the magnetocaloric properties of transition metal based (Fe70Ni30)100‑xCrx (x = 1, 3, 5, 6 and 7) nanoparticles. The influence of Cr additions on the Curie temperature (TC) was studied. Only 5% of Cr can reduce the TC from ~438 K to 258 K. These alloys exhibit broad entropy v/s temperature curves, which is useful to enhance relative cooling power (RCP). For a field change of 5 T, the RCP for (Fe70Ni30)99Cr1 nanoparticles was found to be 548 J-kg‑1. Tunable TCin broad range, good RCP, low cost, high corrosion resistance and earth abundance make these nanoparticles suitable for low-grade waste heat recovery as well as near room temperature active cooling applications.

  6. Magnetocaloric Properties of Fe-Ni-Cr Nanoparticles for Active Cooling

    PubMed Central

    Chaudhary, V.; Ramanujan, R.V.

    2016-01-01

    Low cost, earth abundant, rare earth free magnetocaloric nanoparticles have attracted an enormous amount of attention for green, energy efficient, active near room temperature thermal management. Hence, we investigated the magnetocaloric properties of transition metal based (Fe70Ni30)100−xCrx (x = 1, 3, 5, 6 and 7) nanoparticles. The influence of Cr additions on the Curie temperature (TC) was studied. Only 5% of Cr can reduce the TC from ~438 K to 258 K. These alloys exhibit broad entropy v/s temperature curves, which is useful to enhance relative cooling power (RCP). For a field change of 5 T, the RCP for (Fe70Ni30)99Cr1 nanoparticles was found to be 548 J-kg−1. Tunable TCin broad range, good RCP, low cost, high corrosion resistance and earth abundance make these nanoparticles suitable for low-grade waste heat recovery as well as near room temperature active cooling applications. PMID:27725754

  7. Magnetocaloric Properties of Fe-Ni-Cr Nanoparticles for Active Cooling.

    PubMed

    Chaudhary, V; Ramanujan, R V

    2016-10-11

    Low cost, earth abundant, rare earth free magnetocaloric nanoparticles have attracted an enormous amount of attention for green, energy efficient, active near room temperature thermal management. Hence, we investigated the magnetocaloric properties of transition metal based (Fe70Ni30)100-xCrx (x = 1, 3, 5, 6 and 7) nanoparticles. The influence of Cr additions on the Curie temperature (TC) was studied. Only 5% of Cr can reduce the TC from ~438 K to 258 K. These alloys exhibit broad entropy v/s temperature curves, which is useful to enhance relative cooling power (RCP). For a field change of 5 T, the RCP for (Fe70Ni30)99Cr1 nanoparticles was found to be 548 J-kg(-1). Tunable TCin broad range, good RCP, low cost, high corrosion resistance and earth abundance make these nanoparticles suitable for low-grade waste heat recovery as well as near room temperature active cooling applications.

  8. Phase transformation and tribological properties of Ag-MoO3 contained NiCrAlY based composite coatings fabricated by laser cladding

    NASA Astrophysics Data System (ADS)

    Wang, Lingqian; Zhou, Jiansong; Xin, Benbin; Yu, Youjun; Ren, Shufang; Li, Zhen

    2017-08-01

    Ag-MoO3 contained NiCrAlY based composite coating was successfully prepared on GH4169 stainless steel substrate by high energy ball milling and laser cladding. The microstructure and phase transformation were investigated by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction spectrum (XRD). The tribological behavior and mechanism from room temperature to 800 °C were investigated. Results showed that MoO3 in the composite powders transformed to Mo2C reinforcement under the high energy density of laser, and a series of opposite transformation occurred during friction process. The coating showed the lowest friction coefficient and low wear rate at 600 °C and 800 °C due to the generation of Ag2MoO4 during tribo-chemical reactions and the formation of lubrication glaze on the worn surface. Ag made effective lubrication when the temperature rose up to 200 °C. The coating displayed a relatively high friction coefficient (about 0.51) at 400 °C, because though MoO3 (oxidation products of Mo2C) and Ag2MoO4 were detected on the worn surface, they could not realize effective lubrication at this temperature. Abrasive wear, adhesive wear and plastic deformation contributed to the increased friction and wear.

  9. Comparative study on tribological mechanisms of polyimide composites when sliding against medium carbon steel and NiCrBSi.

    PubMed

    Qi, Huimin; Li, Guitao; Liu, Gen; Zhang, Chao; Zhang, Ga; Wang, Tingmei; Wang, Qihua

    2017-11-15

    Tribological behaviors of various polyimide (PI) composites when rubbing with medium carbon steel (MCS35) and NiCrBSi, were comprehensively investigated. When the conventional PI composite filled with carbon fibers and graphite was concerned, the carbon-based tribofilm formed on NiCrBSi surface resulted in obvious friction- and wear-reduction. However, no lubricating tribofilm was formed on MCS35 surface. Chelation of polymeric molecular radicals with the metallic counterparts was identified on the worn surfaces. Theoretical calculations corroborated that the Ni-based metal-organic compound showed a higher stability than the Fe-based one. With respect to the sliding of the hybrid nanocomposites containing silica or h-BN nanoparticles, the nanoparticles released onto the interface significantly mitigated tribo-oxidation of metallic counterparts, and were finally tribo-sintered into a compact layer after being mixed with remnant polymer and tribo-oxidation products. The effect of counterpart material was less pronounced for the tribological mechanisms of the nanocomposites than for the conventional composite. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Thermal Failure of Nanostructured Thermal Barrier Coatings with Cold-Sprayed Nanostructured NiCrAlY Bond Coat

    NASA Astrophysics Data System (ADS)

    Zhang, Qiang; Li, Chang-Jiu; Li, Yong; Zhang, Shao-Ling; Wang, Xiu-Ru; Yang, Guan-Jun; Li, Cheng-Xin

    2008-12-01

    Nanostructured thermal barrier coatings (TBCs) were deposited by plasma spraying using agglomerated nanostructured YSZ powder on Inconel 738 substrate with cold-sprayed nanostructured NiCrAlY powder as bond coat. The isothermal oxidation and thermal cycling tests were applied to examine failure modes of plasma-sprayed nanostructured TBCs. For comparison, the TBC consisting of conventional microstructure YSZ and conventional NiCrAlY bond coat was also deposited and subjected to the thermal shock test. The results showed that nanostructured YSZ coating contained two kinds of microstructures; nanosized zirconia particles embedded in the matrix and microcolumnar grain structures of zirconia similar to those of conventional YSZ. Although, after thermal cyclic test, a continuous, uniform thermally grown oxide (TGO) was formed, cracks were observed at the interface between TGO/BC or TGO/YSZ after thermal cyclic test. However, the failure of nanostructured and conventional TBCs mainly occurred through spalling of YSZ. Compared with conventional TBCs, nanostructured TBCs exhibited better thermal shock resistance.

  11. Fatigue in a heat treatable high silicon containing aluminium alloy

    NASA Astrophysics Data System (ADS)

    González, J. A.; Talamantes-Silva, J.; Valtierra, S.; Colás, Rafael

    2017-05-01

    The use of cast aluminium alloys in automobiles contributes to reductions in weight and fuel consumption without impairing the safety for the occupants or the performance of the car. Most of the alloys used are heat treatable hypoeutectic Al-Si alloys, which have the drawback of exhibiting low wear resistance. So industry relies in wear resistant alloys, such as grey iron, for the liners of the combustion chambers in engine blocks, which increase the weight of the engine. Therefore, it is of interest to cast high silicon containing alloys into engine components that are able to resist wear while maintaining the mechanical properties required by the components. This work presents the result of the work carried out in a high silicon containing heat treatable aluminium alloy as it is subjected to high cycle fatigue. The alloy was prepared and cast in ingots designed to promote one dimensional solidification gradient to obtain samples to study the high cycle fatigue. The material was machined into hour-glass specimens that were tested at room temperature in a servohydraulic machine under load control following the stair case method. The results show that the resistance to fatigue depends on the microstructure of the sample, as the fatigue cracks originate in pores close to the surface of the sample and propagate through the eutectic aggregate. The results from this work are compared with those from previously obtained with hypoeutectic alloys.

  12. Terahertz Absorption Characteristics of NiCr Film and Enhanced Absorption by Reactive Ion Etching in a Microbolometer Focal Plane Array

    NASA Astrophysics Data System (ADS)

    Gou, Jun; Wang, Jun; Li, Weizhi; Tai, Huiling; Gu, Deen; Jiang, Yadong

    2013-08-01

    Nano - scale metallic films have been proven to be an effective terahertz (THz) absorption layer in uncooled infrared (IR) microbolometers operated in THz spectral range. Optimized absorption can be achieved by adjusting the thickness of metallic film. Nickel - chromium (NiCr) thin films are deposited on the diaphragms of 320 × 240 VOx - based infrared focal plane arrays (IRFPA). Absorption measurements of the diaphragms with different thicknesses of NiCr (5 to 40 nm) agree reasonably well with the predicted absorption. To improve THz absorption further, a reactive ion etching (RIE) process applied to the dielectric support layer is first suggested, which generates nano - scale surface structures and increases the effective surface area of NiCr absorption film. This provides an effective way which is easy to accomplish and compatible with the manufacturing process of microbolometer IRFPAs to improve THz absorption and detection sensitivity.

  13. Effect of non-ionizing radio frequency signals of magnetic resonance imaging on physical properties of dental alloys and metal-ceramic adhesion.

    PubMed

    El-Bediwi, Abu Bakr; El-Fallal, Abeer; Saker, Samah; Ozcan, Mutlu

    2014-10-01

    To assess the influence of non-ionizing radio frequency signals of magnetic resonance imaging (MRI) on physical properties of dental alloys and metal-ceramic adhesion. A total of 120 disk-shaped wax patterns (10 mm x 10 mm x 1 mm) were cast in a base metal alloy (Ni-Cr alloy) and commercially pure titanium (Ti) following the manufacturing recommendation. After casting, air abrasion and ultrasonic cleaning, feldspathic ceramic was applied and fired according to manufacturer's instructions using a standard mold. The specimens were subjected to 3000 thermocycles in distilled water between 5°C and 55°C, then veneered alloy specimens were randomly assigned to three groups according to MRI exposure time: a) 15 min of MRI exposure, b) 30 min of MRI exposure and c) no MRI exposure (control group). The specimens were subjected to shear loading until failure. A separate set of Ni-Cr and Ti specimens were prepared, and after exposure to MRI for 15 and 30 min, x-ray diffraction (XRD) analysis, surface roughness, and Vicker's hardness were measured. Both the alloy type (p < 0.005) and exposure duration (p < 0.005) had a significant effect on the bond results. While the control group presented the highest bond strength for Ni-Cr and Ti (36.9 ± 1.4 and 21.5 ± 1.6 MPa, respectively), 30 min MRI exposure significantly decreased the bond strength for both alloys (29.4 ± 1.5 and 12.8 ± 1.5 MPa, respectively) (p < 0.05). XRD analysis indicated formation of the crystalline phase as well as change in crystal size and position for Ni-Cr and Ti after MRI. Compared to the control group where alloys were not exposed to MRI (Ni-Cr: 0.40 μm; Ti: 0.17 μm), surface roughness increased (Ni-Cr: 0.54 μm; Ti: 1.1 μm). Vicker's hardness of both alloys decreased after 30 min MRI (Ni-Cr: 329.5; Ti: 216.1) compared to the control group c (Ni-Cr: 356.1; Ti: 662.1), being more significant for Ti (p < 0.005). Ni-Cr alloy is recommended over Ti for the fabrication of metal-ceramic restorations

  14. APFIM characterization of 15Kh2MFA Cr-Mo-V and 15Kh2NMFA Ni-Cr-Mo-V type steels

    NASA Astrophysics Data System (ADS)

    Miller, M. K.; Jayaram, R.; Othen, P. J.; Brauer, G.

    1994-03-01

    A microstructural characterization of 15Kh2MFA Cr-Mo-V and 15Kh2NMFA Ni-Cr-Mo-V type steels that are used in the pressure vessels of Russian VVER 440 and VVER 1000 nuclear reactors, respectively, has been performed with the use of the techniques of atom-probe field-ion microscopy (APFIM) and transmission electron microscopy. The microstructure of these materials was found to be tempered martensite and bainite. A high number density of coarse (≈ 50 to ≈ 500 nm) blocky M 7C 3 carbides and some inclusions were observed. In addition to these coarse carbides, some finer (≈ 10 nm diameter) approximately spherical MC carbides were also observed in the VVER 440 steel. Field-ion microscopy has revealed that the lath boundaries in both unirradiated VVER 440 and VVER 1000 reactor steels are decorated with an ultrathin semicontinuous film of molybdenum-carbonitride precipitates. Atom-probe analysis has revealed a high enrichment of phosphorus at the lath boundaries.

  15. [The effect of solid phase transformation on the metal-ceramic compatibility of Co-Cr alloy].

    PubMed

    Wu, Zhikai; Xu, Sheng; Li, Ning

    2011-12-01

    To study the effect of solid phase transformation on the metal-ceramic compatibility of Co-Cr alloy during firing programs. 9 foils of Co-Cr and Ni-Cr alloy with the dimension of 25 mmx3 mmx0.5 mm were casted using lost wax technology respectively. Among them, 6 specimens were subjected to metal-ceramic bonding strength test (three point bending method), the ceramic layer of 3 specimens were removed for X-ray diffraction (XRD) analysis. One cylindrical specimen of each alloy was casted for the test of coefficient of thermal expansion, cooling curves were recorded. The metal-ceramic bonding strength of Ni-Cr, Co-Cr alloy was (49.1 +/- 3.40), (40.9 +/- 2.02) MPa respectively. There was significant difference between the two groups' bonding strength (P = 0.00). The coefficient of thermal expansion in the 20-500 degrees C interval of Ni-Cr and Co-Cr alloy was 13.9 x 10(-6), 13.8 x 10(-6) x K(-1) respectively. XRD analysis indicated that the microstructure of Ni-Cr alloy was austenite. While Co-Cr alloy was constituted by fcc phase, hcp phase and sigma phase. During the cooling procedure, the transformation of fcc phase to hcp phase and segregation of needle-like sigma phase intensify the linear contraction speed of Co-Cr alloy, which decreases the metal-ceramic adaptability.

  16. Irradiation damage in multicomponent equimolar alloys and high entropy alloys (HEAs).

    PubMed

    Nagase, Takeshi; Rack, Philip D; Egami, Takeshi

    2014-11-01

    To maintain sustainable energy supply and improve the safety and efficiency of nuclear reactors, development of new and advanced nuclear materials with superior resistance to irradiation damage is necessary. Recently, a new generation of structural materials, termed as multicomponent equimolar alloys and/or high entropy alloys (HEAs), are being developed. These alloys consist of multicomponent elements for maximizing the compositional entropy, which stabilizes the solid solution phase. In this paper, preliminary studies on the irradiation damage in equimolar alloys and HEAs by High Voltage Electron Microscopy (HVEM) are reported [1-4]. (1) ZrHfNb equimolar alloys [1, 2]A multicomponent ZrHfNb alloy was prepared by a co-sputtering process using elemental Zr, Hf, and Nb targets using an AJA International ATC 2000-V system. A single-phase bcc solid solution was obtained in the ZrHfNb alloy with an approximately equiatomic ratio of its constituent elements. The irradiation-induced structural change in the ZrHfNb equimolar alloys with the bcc solid solution structure was investigated by HVEM using the Hitachi H-3000 installed at Osaka University. The polycrystalline bcc phase shows high phase stability against irradiation damage at 298 K; the bcc solid solution phase, whose grain size was about 20 nm, remained as a main constituent phase even after the severe irradiation damage that reached 10 dpa. (2) CoCrCuFeNi HEAs [3]A single-phase fcc solid solution was obtained in a CoCrCuFeNi alloy. The microstructure of the alloy depended on the preparation technique: a nanocrystalline CoCrCuFeNi alloy with an approximately equiatomic ratio of its constituent elements was obtained by a co-sputtering process with multi-targets, while polycrystalline structures were formed when the arc-melting method was used. Both nanocrystalline and polycrystalline structures showed high phase stability against fast electron irradiation at temperatures ranging from 298 K to 973 K; a fcc

  17. High bandgap III-V alloys for high efficiency optoelectronics

    DOEpatents

    Alberi, Kirstin; Mascarenhas, Angelo; Wanlass, Mark

    2017-01-10

    High bandgap alloys for high efficiency optoelectronics are disclosed. An exemplary optoelectronic device may include a substrate, at least one Al.sub.1-xIn.sub.xP layer, and a step-grade buffer between the substrate and at least one Al.sub.1-xIn.sub.xP layer. The buffer may begin with a layer that is substantially lattice matched to GaAs, and may then incrementally increase the lattice constant in each sequential layer until a predetermined lattice constant of Al.sub.1-xIn.sub.xP is reached.

  18. Electrodepositing behaviors and properties of nano Fe-Ni-Cr/SiC composite coatings from trivalent chromium baths containing compound carboxylate-urea system.

    PubMed

    He, Xinkuai; Hou, Bailong; Cai, Youxing; Li, Chen; Jiang, Yumei; Wu, Luye

    2013-06-01

    The nano Fe-Ni-Cr/SiC composite coatings were prepared using pulse electrodeposition method from trivalent chromium baths containing compound carboxylate-urea system and nano SiC in ultrasonic field. The effects of the carboxylate-urea system on the nano Fe-Ni-Cr/SiC composite coatings have been investigated. These results indicated that the SiC and Cr contents and the thickness of the Fe-Ni-Cr/SiC composite coatings could be obviously improved by the compound carboxylate-urea system. The steady-state polarization curves showed that the hydrogen evolution reaction (HER) could be significantly inhibited by the compound carboxylate-urea system, which was benefit to increase the SiC and Cr contents and the thickness of the composite coatings. The cyclic voltammetry (CV) curves showed that the cathodic polarization of the matrix metal ions could be increased in the bath containing the compound carboxylate-urea system. Thus, a compact Fe-Ni-Cr/SiC composite coating could be obtained using this technique. The surface morphology of the Fe-Ni-Cr/SiC composite coatings checked with the scanning electron micrographs (SEM) showed that the surface smoothness could be also improved and the microcracks and pinholes could be decreased due to the presence of the compound carboxylate-urea system. The phase composition of the as-posited coating was measured by the X-ray diffraction (XRD). XRD data showed that the as-posited coating was Fe-Ni-Cr/SiC composite coating. The chemical composition of the coating was investigated by energy dispersive spectrum (EDS) analysis. The result showed the functional Fe-Ni-Cr/SiC composite coatings with 4.1 wt.% SiC and 25.1 wt.% Cr, and 23.9 microm thickness were obtained in this study, which had best corrosion resistance according to the results of the typical potentiodynamic polarization curves of the Fe-Ni-Cr/SiC composite coatings.

  19. 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.

  20. Effect of temperature variation on the cytotoxicity of cast dental alloys and commercially pure titanium.

    PubMed

    Faria, Adriana Cláudia Lapria; Rodrigues, Renata Cristina Silveira; Antunes, Rossana Pereira de Almeida; de Mattos, Maria da Gloria Chiarello; Rosa, Adalberto Luiz; Ribeiro, Ricardo Faria

    2009-01-01

    Cell culture system has been used to evaluate alloy cytotoxicity under different environments, testing the extracts, but the effect of temperature variation on the cytotoxicity of dental alloys has not been analyzed. The aim of the present study was to investigate if temperature variation could affect dental alloy cytotoxicity, testing alloy extracts in an epithelial cell culture system. Discs of Ni-Cr, Co-Cr-Mo, Ni-Cr-Ti, Ti-6Al-4V and commercially pure titanium (cp Ti) were cast by arc melting, under argon atmosphere, injected by vacuum-pressure. Discs were immersed in artificial saliva and subjected to different temperatures: 37 degrees C and thermocycling (37 degrees C/5 degrees C/37 degrees C/55 degrees C/37 degrees C). After thermocycling, extracts were put in a subconfluent culture during 6 h, and the number of cells and their viability were used to evaluate cytotoxicity in these temperatures. For each alloy, data from temperature conditions were compared by Student's t-test (alpha=0.05). The cytotoxicity tests with alloy/metal extracts showed that Ni-Cr, Co-Cr-Mo, Ti-6Al-4V and cp Ti extracts (p>0.05) did not affect cell number or cell viability, while Ni-Cr-Ti (p<0.05) extract decreased cell number and viability when the alloy was subjected to thermocycling. Within the limitations of the present study, the Ni-Cr-Ti alloy had cell number and viability decreased when subjected to temperature variation, while the other alloys/metal extracts did not show these results.

  1. EFFECT OF TEMPERATURE VARIATION ON THE CYTOTOXICITY OF CAST DENTAL ALLOYS AND COMMERCIALLY PURE TITANIUM

    PubMed Central

    Faria, Adriana Cláudia Lapria; Rodrigues, Renata Cristina Silveira; Antunes, Rossana Pereira de Almeida; de Mattos, Maria da Gloria Chiarello; Rosa, Adalberto Luiz; Ribeiro, Ricardo Faria

    2009-01-01

    Cell culture system has been used to evaluate alloy cytotoxicity under different environments, testing the extracts, but the effect of temperature variation on the cytotoxicity of dental alloys has not been analyzed. Objective: The aim of the present study was to investigate if temperature variation could affect dental alloy cytotoxicity, testing alloy extracts in an epithelial cell culture system. Material and methods: Discs of Ni-Cr, Co-Cr-Mo, Ni-Cr-Ti, Ti-6Al-4V and commercially pure titanium (cp Ti) were cast by arc melting, under argon atmosphere, injected by vacuum-pressure. Discs were immersed in artificial saliva and subjected to different temperatures: 37°C and thermocycling (37°C/5°C/37°C/55°C/37°C). After thermocycling, extracts were put in a subconfluent culture during 6 h, and the number of cells and their viability were used to evaluate cytotoxicity in these temperatures. For each alloy, data from temperature conditions were compared by Student's t-test (α=0.05). Results: The cytotoxicity tests with alloy/metal extracts showed that Ni-Cr, Co-Cr-Mo, Ti-6Al-4V and cp Ti extracts (p>0.05) did not affect cell number or cell viability, while Ni-Cr-Ti (p<0.05) extract decreased cell number and viability when the alloy was subjected to thermocycling. Conclusion: Within the limitations of the present study, the Ni-Cr-Ti alloy had cell number and viability decreased when subjected to temperature variation, while the other alloys/metal extracts did not show these results. PMID:19936519

  2. Swelling of Uranium Alloys at High Exposures

    SciTech Connect

    McDonell, W.R.

    2001-03-26

    This reports summarizes the results of postirradiation examinations of a series of unrestrained dilute uranium alloy specimens irradiated to exposures up to 13,000 MWD/T in NaK-containing stainless steel capsules.

  3. Study of high performance alloy electroforming

    NASA Technical Reports Server (NTRS)

    Malone, G. A.

    1984-01-01

    The first series of heat treated nickel manganese alloys are tested for mechanical properties at temperatures of 148.9 C (300 F) and 260 C (500 F). All material receives the same heat treatment in order to provide a common basis for comparison of results. Mechanical property performance improves with increasing manganese content in the alloy. Although all manganese bearing alloy is significantly superior to conventional electroformed nickel, samples containing over 3000 ppm manganese display outstanding ultimate and yield strengths while maintaining reasonably satisfactory ductility. Alloy containing over 6000 ppm of manganese is very competitive to Inconel 718 (mill annealed and age hardened) at all temperatures of interest, although ductility is not as great in the electrodeposited counterpart.

  4. Creep and intergranular cracking of Ni-Cr-Fe-C in 360[degree]C argon

    SciTech Connect

    Angeliu, T.M. ); Was, G.S. )

    1994-06-01

    The influence of carbon and chromium on the creep and intergranular (IG) cracking behavior of controlled-purity Ni-xCr-9Fe-yC alloys in 360 C argon was investigated using constant extension rate tension (CERT) and constant load tension (CLT) testing. The CERT test results at 360 C show that the degree of IG cracking increases with decreasing bulk chromium or carbon content. The CLT test results at 360 C and 430 C reveal that, as the amounts of chromium and carbon in solution decrease, the steady-state creep rate increases. The occurrence of severe IG cracking correlates with a high steady-state creep rate, suggesting that creep plays a role in the IG cracking behavior in argon at 360 C. The failure mode of IG cracking and the deformation mode of creep are coupled through the formation of grain boundary voids that interlink to form grain boundary cavities, resulting in eventual failure by IG cavitation and ductile overload of the remaining ligaments. Grain boundary sliding may be enhancing grain boundary cavitation by redistributing the stress from inclined to more perpendicular boundaries and concentrating stress at discontinuities for the boundaries oriented 45 deg with respect to the tensile axis. Additions of carbon or chromium, which reduce the creep rate over all stress levels, also reduce the amount of IG fracture in CERT experiments. A damage accumulation model was formulated and applied to CERT tests to determine whether creep damage during a CERT test controls failure. Results show that, while creep plays a significant role in CERT experiments, failure is likely controlled by ductile overload caused by reduction in area resulting from grain boundary void formation and interlinkage.

  5. Effect of boron on intergranular hot cracking in Ni-Cr-Fe superalloys containing niobium

    NASA Technical Reports Server (NTRS)

    Thompson, R. G.

    1990-01-01

    Solidification mechanisms had a dominant influence on microfissuring behavior of the test group. Carbon modified the Laves formation significantly and showed that one approach to alloy design would be balancing carbide formers against Laves formers. Boron's strong effect on microfissuring can be traced to its potency as a Laves former. Boron's segregation to grain boundaries plays at best a secondary role in microfissuring.

  6. Phase relations of iron alloys at high pressure (Invited)

    NASA Astrophysics Data System (ADS)

    Kuwayama, Y.; Hirose, K.; Sata, N.; Ohishi, Y.

    2009-12-01

    The Earth's core is believed to be composed of iron-nickel alloy with a small amount of one or more light elements (such as H, C, O, Si and S). Phase relations and crystal structures of iron alloys at high pressures are essential for understanding the seismic observations and the nature of the solid inner core. For recent years, we have developed experimental techniques of the high P-T generation using a laser-heated diamond-anvil cell (LH-DAC) and studied the phase relations of various iron alloys at high pressure and high temperature. For example, phase relations of iron and iron-nickel alloys were investigated up to 300 GPa and 2000 K (Kuwayama et al. EPSL, 2008). Iron-silicon alloys and iron-sulfur alloys were also studied up to more than 200 GPa, based on in-situ x-ray diffraction measurements along with chemical analysis of the quenched samples using a field-emission electron microprobe (FE-EPMA)(Kuwayama et al. PCM, 2009). In this talk, I will present recent experimental results on iron alloys and discuss the structure and composition of the Earth's inner core.

  7. Fully alloyed metal nanorods with highly tunable properties.

    PubMed

    Albrecht, Wiebke; van der Hoeven, Jessi E S; Deng, Tian-Song; de Jongh, Petra E; van Blaaderen, Alfons

    2017-02-23

    Alloyed metal nanorods offer a unique combination of enhanced plasmonic and photothermal properties with a wide variety in optical and catalytic properties as a function of the alloy composition. Here, we show that fully alloyed anisotropic nanoparticles can be obtained with complete retention of the particle shape via thermal treatment at surprisingly low temperatures. By coating Au-Ag, Au-Pd and Au-Pt core-shell nanorods with a protective mesoporous silica shell the transformation of the rods to a more stable spherical shape was successfully prevented during alloying. For the Au-Ag core-shell NRs the chemical stability was drastically increased after alloying, and from Mie-Gans and finite-difference time-domain (FDTD) calculations it followed that alloyed AuAg rods also exhibit much better plasmonic properties than their spherical counterparts. Finally, the generality of our method is demonstrated by alloying Au-Pd and Au-Pt core-shell NRs, whereby the AuPd and AuPt alloyed NRs showed a surprisingly high increase in thermal stability of several hundred degrees compared with monometallic silica coated Au NRs.

  8. Initial development of high-temperature titanium silicide alloys

    SciTech Connect

    Liu, C.T.; Lee, E.H.; Henson, T.J.

    1988-01-01

    Mechanical and metallurgical properties of Ti/sub 5/Si/sub 3/ and its alloys were studied for the purpose of developing high-temperature silicides for structural use. Titanium silicides are extremely hard and brittle. Microcracks that formed transgranularly were observed in the silicide and its alloys, indicating a poor cleavage strength for Ti/sub 5/Si/sub 3/. Microalloying with boron and carbon gave no apparent beneficial effect. The tendency for cracking can be reduced by lowering the silicon content or by alloying with 2 to 4% Cr and 4% Zr. In particular, almost no cracks were observed in the alloy Ti-33Si-4Zr-4Cr (at. %). Titanium silicide has a hardness of 980 dph. The hardness shows a slight increase with zirconium additions and a decrease with chromium additions. Tensile tests indicate that the silicide and its alloys are brittle even at 1000/degree/C. All alloys fractured with a strength less than 100 MPa. Among the silicides tested, the alloys containing 4 to 8% Cr have better fracture strength. The fracture mode of the silicide alloys is mainly transgranular with a cleavage appearance. The silicides showed basically a parabolic oxidation rate at 800/degree/C, with an oxidation rate higher by an order of magnitude than that of nickel aluminides. 10 figs., 5 tabs.

  9. HIGH-TEMPERATURE OXIDATION PROTECTIVE COATINGS FOR VANADIUM-BASE ALLOYS

    DTIC Science & Technology

    SILICIDES , SILICON COATINGS , TENSILE PROPERTIES, TITANIUM ALLOYS, YTTRIUM COMPOUNDS....CERAMIC COATINGS , *METAL COATINGS , *VANADIUM ALLOYS, ALLOYS, ANTIOXIDANTS, BORON COMPOUNDS, COATINGS , DEFORMATION, ELECTRODEPOSITION, FLAME SPRAYING...HEAT RESISTANT ALLOYS, HIGH TEMPERATURE, INTERMETALLIC COMPOUNDS, MECHANICAL PROPERTIES, NICKEL, NICKEL COMPOUNDS, NIOBIUM ALLOYS, OXIDES, PLATING

  10. Laser assisted high entropy alloy coating on aluminum: Microstructural evolution

    SciTech Connect

    Katakam, Shravana; Joshi, Sameehan S.; Mridha, Sanghita; Mukherjee, Sundeep; Dahotre, Narendra B.

    2014-09-14

    High entropy alloy (Al-Fe-Co-Cr-Ni) coatings were synthesized using laser surface engineering on aluminum substrate. Electron diffraction analysis confirmed the formation of solid solution of body centered cubic high entropy alloy phase along with phases with long range periodic structures within the coating. Evolution of such type of microstructure was a result of kinetics associated with laser process, which generates higher temperatures and rapid cooling resulting in retention of high entropy alloy phase followed by reheating and/or annealing in subsequent passes of the laser track giving rise to partial decomposition. The partial decomposition resulted in formation of precipitates having layered morphology with a mixture of high entropy alloy rich phases, compounds, and long range ordered phases.

  11. Interfacial Reactions of High-Bi Alloys on Various Substrates

    NASA Astrophysics Data System (ADS)

    Wang, Jin-Yi; Chen, Chih-Ming; Yen, Yee-Wen

    2014-01-01

    Bi-Sn alloys with high Bi concentration are potential candidates to replace high-Pb alloys as high-temperature Pb-free solders. Interfacial reactions between high-Bi alloys (Sn concentration 2 wt.%, 5 wt.%, and 10 wt.%) and various substrates have been investigated to understand the intermetallic compound formation and interfacial morphological evolution at the joint interface. The substrates investigated include Ni, Au/Ni, Cu, and Ag/Cu layers deposited on Si chips. The interfacial reactions were carried out at 300°C and 120°C to simulate the liquid/solid and solid/solid reactions, respectively, at such solder joints. Experimental results reveal that the intermetallic compound formation and interfacial morphological evolution vary with the substrate and the Sn concentration of the Bi-Sn alloy.

  12. High-temperature alloys: Single-crystal performance boost

    NASA Astrophysics Data System (ADS)

    Schütze, Michael

    2016-08-01

    Titanium aluminide alloys are lightweight and have attractive properties for high-temperature applications. A new growth method that enables single-crystal production now boosts their mechanical performance.

  13. Microstructure and Mechanical Behavior of High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Licavoli, Joseph J.; Gao, Michael C.; Sears, John S.; Jablonski, Paul D.; Hawk, Jeffrey A.

    2015-10-01

    High-entropy alloys (HEAs) have generated interest in recent years due to their unique positioning within the alloy world. By incorporating a number of elements in high proportion, usually of equal atomic percent, they have high configurational entropy, and thus, they hold the promise of interesting and useful properties such as enhanced strength and alloy stability. The present study investigates the mechanical behavior, fracture characteristics, and microstructure of two single-phase FCC HEAs CoCrFeNi and CoCrFeNiMn with some detailed attention given to melting, homogenization, and thermo-mechanical processing. Ingots approaching 8 kg in mass were made by vacuum induction melting to avoid the extrinsic factors inherent to small-scale laboratory button samples. A computationally based homogenization heat treatment was given to both alloys in order to eliminate any solidification segregation. The alloys were then fabricated in the usual way (forging, followed by hot rolling) with typical thermo-mechanical processing parameters employed. Transmission electron microscopy was subsequently used to assess the single-phase nature of the alloys prior to mechanical testing. Tensile specimens (ASTM E8) were prepared with tensile mechanical properties obtained from room temperature through 800 °C. Material from the gage section of selected tensile specimens was extracted to document room and elevated temperature deformation within the HEAs. Fracture surfaces were also examined to note fracture failure modes. The tensile behavior and selected tensile properties were compared with results in the literature for similar alloys.

  14. Nonequilibrium Phase Chemistry in High Temperature Structure Alloys

    NASA Technical Reports Server (NTRS)

    Wang, R.

    1991-01-01

    Titanium and nickel aluminides of nonequilibrium microstructures and in thin gauge thickness were identified, characterized and produced for potential high temperature applications. A high rate sputter deposition technique for rapid surveillance of the microstructures and nonequilibrium phase is demonstrated. Alloys with specific compositions were synthesized with extended solid solutions, stable dispersoids, and specific phase boundaries associated with different heat treatments. Phase stability and mechanical behavior of these nonequilibrium alloys were investigated and compared.

  15. Processability and High Temperature Behavior of Emerging Aerospace Alloys

    DTIC Science & Technology

    1988-08-01

    I F opy IOSR-Th. 8-O0 970 - SC5459.AR - c Copy No. 4 0i Q PROCESSABILITY AND HIGH TEMPERATURE BEHAVIOR OF EMERGING AEROSPACE ALLOYS ANNUAL REPORT NO...NO. NO. ACCESSION NO. b0’ 2306 A\\ 11. TITLE finclude Security Classficationi PROCESSABILITY AND HIGH TEMPERATURE BEHAVIOR OF EMERGING AEROSPACE ALLOYS...conducted. Progress of microstruc - turel refinement and changes in misorientation between subgrains are determined to delineate the path for optimum

  16. Materials Design for Joinable, High Performance Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Glamm, Ryan James

    An aluminum alloy compatible with friction stir welding is designed for automotive and aerospace structural applications. Current weldable automotive aluminum alloys do not possess the necessary strength to meet safety standards and therefore are not able to replace steel in the automotive body. Significant weight savings could be achieved if steel components are replaced with aluminum. Current aerospace alloys are not weldable, requiring machining of large pieces that are then riveted together. If an aerospace alloy could be friction stir welded, smaller pieces could be welded, reducing material waste. Using a systems approach for materials design, property goals are set from performance objectives. From previous research and computational predictions, a structure is designed for a prototype alloy containing dynamic precipitates to readily dissolve and re-precipitate and high stability precipitates to resist dissolution and coarsening in the weld region. It is found that a Ag modified Al-3.9Mg-0.04Cu (at. %) alloy enhanced the rate and magnitude of hardening during ageing, both beneficial effects for dynamic precipitation. In the same alloy, ageing at 350°C results in hardening from Al 3(Sc,Zr) precipitates. Efforts to effectively precipitate both populations simultaneously are unsuccessful. The Al3(Sc,Zr) precipitation hardened prototype is friction stir processed and no weak zones are found in the weld hardness profile. An aerospace alloy design is proposed, utilizing the dual precipitate structure shown in the prototype. The automotive alloy is designed using a basic strength model with parameters determined from the initial prototype alloy analysis. After ageing to different conditions, the alloy is put through a simulated heat affected zone thermal cycle with a computer controlled induction heater. The aged samples lose hardness from the weld cycle but recover hardness from a post weld heat treatment. Atom probe tomography and transmission electron

  17. Sputter-ion plating of coatings for protection of gas-turbine blades against high-temperature oxidation and corrosion

    NASA Technical Reports Server (NTRS)

    Coad, J. P.; Restall, J. E.

    1982-01-01

    Considerable effort is being devoted to the development of overlay coatings for protecting critical components such as turbine blades against high-temperature oxidation, corrosion, and erosion damage in service. The most commercially advanced methods for depositing coatings are electron-beam evaporation and plasma spraying. Sputter-ion plating (SIP) offers a potentially cheaper and simpler alternative method for depositing overlays. Experimental work on SIP of Co-Cr-Al-Y and Ni-Cr-Al-Ti alloy coatings is described. Results are presented of metallographic assessment of these coatings, and of the results obtained from high-velocity testing using a gas-turbine simulator rig.

  18. An empirical-statistical model for coaxial laser cladding of NiCrAlY powder on Inconel 738 superalloy

    NASA Astrophysics Data System (ADS)

    Ansari, M.; Shoja Razavi, R.; Barekat, M.

    2016-12-01

    In this study, coaxial laser cladding of NiCrAlY powder on a nickel-based superalloy is investigated from an experimental point of view so as to propose an empirical-statistical model for the process. The correlations between main processing parameters (i.e. scanning speed, powder feeding rate, and laser power) and geometrical characteristics (i.e. width, height, penetration depth, dilution and wetting angle) of single clad tracks have been predicted and are discussed using regression analysis (RA). The validity of the predictions is confirmed by providing correlation coefficient and analysis of the residuals. The correlations are established as a combined parameter (PαVβFγ) for each studied characteristic of single clad tracks. These correlations finally lead to the design of a processing map that can be practically used to select proper processing parameters for laser cladding of the particular material.

  19. Acoustic Emission Investigation of Rolling/Sliding Contact Fatigue Failure of NiCr-Cr3C2 Coating

    NASA Astrophysics Data System (ADS)

    Guolu, Li; Zhonglin, Xu; Tianshun, Dong; Haidou, Wang; Jinhai, Liu; Jiajie, Kang

    2016-10-01

    NiCr-Cr3C2 coating was fabricated using supersonic plasma spraying technology. Subsequently, rolling/sliding contact fatigue (R/SCF) testing was carried out, using acoustic emission (AE) technology to monitor the failure process. The results showed that R/SCF consists of three failure modes, namely abrasion, spalling, and delamination. Abrasion is the main failure mode, but delamination is the most severe. The AE monitoring results indicated that the R/SCF failure process is composed of normal contact, crack initiation, crack propagation, and material removal stages. The frequency of each stage was analyzed by fast Fourier transform, revealing a peak frequency for each stage mainly distributed from 200 to 250 kHz.

  20. Observations on the relationship of structure to the mechanical properties of thin TD-NiCr sheet

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1976-01-01

    A study of the relationship between structure and mechanical properties of thin TD-NiCr sheet indicated that the elevated temperature tensile, stress-rupture, and creep strength properties are dependent on grain aspect ratio and sheet thickness. In general, the strength properties increase with increasing grain aspect ratio and sheet thickness. Tensile testing revealed an absence of ductility at elevated temperatures (not less than 1144 K). Significant creep damage as determined by subsequent tensile testing at room temperature occurs after very small amounts (less than 0.1%) of prior creep deformation over the temperature range 1144-1477 K. A threshold stress for creep appears to exist. Creep exposure below the threshold stress at T not less than 1366 K results in almost full retention of room temperature tensile properties.