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Sample records for b2 iron aluminides

  1. Thermal defects in B2 iron aluminide

    SciTech Connect

    Collins, G.S.; Peng, L.S.J.; Wei, M.

    1999-07-01

    Thermal defects in B2 FeAl samples with compositions between 49.5 and 54.7 at.% Fe were investigated using perturbed angular correlation of gamma rays (PAC). Vacancies on the Fe-sublattice were detected through quadrupole interactions induced at adjacent {sup 111}In/Cd probe atoms on the Al-sublattice. Five high-frequency quadrupole-interaction signals were detected (greater than 50 Mrad/s) that are attributed to complexes involving 1, 2, 3, 4 and (with less certainty) 5 Fe-vacancies in the first neighbor shells of the probes. These attribution are based on (1) a comparison between measured quadrupole interaction parameters and point-charge calculations of electric-field gradients for possible vacancy-probe complexes; and (2) numerical simulation of the evolution of site fractions of probes in the complexes at lower temperatures. Measurements were made at temperatures up to 950 C. Assuming that the equilibrium high-temperature is the triple defect (2 Fe-vacancies and one Fe-antisite atom), measurements over the range 600--900 C yield a formation enthalpy of 1.1(1) eV for the triple defect. Below about 600 C, Fe-vacancies are quenched-in with a fractional concentration of the order of 1 at.% close to stoichiometry. However, quenched-in vacancies continue to jump over short distances and trap next to the impurity probes atoms in day-long measurements down to 200 C. Simulations of site fractions below 700 C were used to determine binding enthalpies of vacancies with probe complexes. Binding enthalpies obtained for the first four vacancies were 0.23, 0.23, 0.15 and 0.18 eV. Simulations in the range 200--700 C suggest a negative value for the formation entropy. The negative value indicates either that triple defects stiffen the B2 lattice or that repulsive defect-defect interactions become important at the high defect concentrations in FeAl.

  2. Embrittlement of B2 iron aluminide by water vapor and by hydrogen

    NASA Astrophysics Data System (ADS)

    Kasul, D. B.; Heldt, L. A.

    1994-06-01

    The kinetics of embrittlement of a B2 iron aluminide in air were determined by measuring subcritical crack velocities under constant loading conditions and by measuring the strain rate dependence of the ductility. Correlative studies of embrittlement by internal hydrogen were carried out on cathodically charged samples, and the rates of ductility recovery were measured by baking the samples. The results of the hydrogen experiments are employed to consider whether subcritical cracking in air at the measured rates can be supported by hydrogen penetrating ahead of the advancing crack.

  3. Strength, thermal defects, and solid solution hardening in nickel-containing B2 iron aluminides

    SciTech Connect

    Schneibel, J.H.; Munroe, P.R.; Pike, L.M.

    1996-12-31

    Nickel-containing ternary iron aluminides with an aluminum concentration of 45 at.% were investigated with respect to room temperature strength, equilibrium vacancy concentration, and the kinetics of vacancy removal. As compared to binary iron aluminides with the same Al concentration, nickel additions reduce the thermal equilibrium vacancy concentration at 1,273 K, whereas they increase this concentration at 973 K. Furthermore, at low temperatures such as 673 K, nickel additions increase dramatically the time needed to reach vacancy equilibrium. During prolonged annealing at 673 K, the density of <001> dislocations in Fe-45Al-3Ni (at.%) increased by an order of magnitude. This suggests that dislocations act as sinks for vacancies. At the same time, the number density of small (20--50 nm) voids decreased, indicating that they were not stable in the absence of substantial vacancy supersaturations. The findings show also that the solid solution strengthening of iron aluminides due to Ni is much weaker than previously thought.

  4. Iron Aluminide Composites

    SciTech Connect

    Schneibel, J.H.

    1998-11-20

    Iron aluminides with the B2 structure are highly oxidation and corrosion resistant. They are thermodynamically compatible with a wide range of ceramics such as TiC, WC, TiB{sub 2}, and ZrB{sub 2}. In addition, liquid iron aluminides wet these ceramics very well. Therefore, FeAl/ceramic composites may be produced by techniques such as liquid phase sintering of powder mixtures, or pressureless melt infiltration of ceramic powders with liquid FeAl. These techniques, the resulting microstructure, and their advantages as well as limitations are described. Iron aluminide composites can be very strong. Room temperature flexure strengths as high as 1.8 GPa have been observed for FeAl/WC. Substantial gains in strength at elevated temperatures (1073 K) have also been demonstrated. Above 40 vol.% WC the room temperature flexure strength becomes flaw-limited. This is thought to be due to processing flaws and limited interfacial strength. The fracture toughness of FeAl/WC is unexpectedly high and follows a mile of mixtures. Interestingly, sufficiently thin (< 1 {micro}m) FeAl ligaments between adjacent WC particles fracture not by cleavage, but in a ductile manner. For these thin ligaments the dislocation pile-ups formed during deformation are not long enough to nucleate cleavage fracture, and their fracture mode is therefore ductile. For several reasons, this brittle-to-ductile size transition does not improve the fracture toughness of the composites significantly. However, since no cleavage cracks are nucleated in sufficiently thin FeAl ligaments, slow crack growth due to ambient water vapor does not occur. Therefore, as compared to monolithic iron aluminizes, environmental embrittlement is dramatically reduced in iron aluminide composites.

  5. On the crack growth resistance and strength of the B2 iron aluminides Fe-40Al, Fe-45Al, and Fe-10Ni-40Al (at. %)

    SciTech Connect

    Schneibel, J.H.; Maziasz, P.J.

    1994-09-01

    The crack growth resistance and yield strength of the B2 iron aluminides Fe-40Al, Fe-45Al, are Fe-10Ni-40Al (at. %) have been investigated at room temperature laboratory air. After fast cooling from 1273 K, Fe-45Al and Fe-10Ni-40Al are much stronger than Fe-40Al, and exhibit considerably lower crack growth resistance. The crack growth resistance decreases with decreasing crack propagation velocity. Low crack propagation velocities favor intergranular fracture, whereas high velocities can lead to significant contributions from transgranular fracture. Boron additions to Fe-40Al and Fe-10Ni-40Al improve the crack growth resistance, reduce its dependence on the crack propagation velocity, and cause the path to be predominantly transgranular. In a plot of fracture toughness versus yield strength, the properties of the iron aluminides are similar to those of typical aluminum alloys.

  6. The B2 aluminides as alternative materials

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.

    1984-01-01

    The potential of the B2 aluminides as structural material alternatives for the strategic element containing superalloys currently used in gas turbine engines is being explored with emphasis on the equiatomic Fe and Ni aluminides. Although Co is a strategic material, the equiatomic Co aluminide is also being studied to gain a more complete understanding of these fourth period intermetallics. Research focuses on initial processing techniques such as ingot melting, power metallurgy, and rapid solidification with and without additional thermomechanical processing; high temperature deformation - primarily compressive creep; compositional effects within the binary B2 aluminides; third-element alloying addition effects on high temperature strength and oxidation resistance, and near room temperature ductility as influenced by processing, alloying, and grain size. Various programs now underway are reviewed and some highlights of research results are presented.

  7. Development of iron aluminides

    SciTech Connect

    Viswanathan, S.; Sikka, V.K.; Andleigh, V.K.

    1995-06-01

    The primary reason for the poor room-temperature ductility of Fe{sub 3}Al-based alloys is generally accepted to be environmental embrittlement due to hydrogen produced by the reaction of aluminum with water vapor present in the test atmosphere. In the as-cast condition, another possible reason for the low room-temperature ductility is the large grain size (0.5 to 3 mm) of the cast material. While recent studies on iron aluminides in the wrought condition have led to higher room-temperature ductility and increased high-temperature strength, limited studies have been conducted on iron aluminides in the as-cast condition. The purpose of this study was to induce grain refinement of the as-cast alloy through alloying additions to the melt and study the effect on room-temperature ductility as measured by the strain corresponding to the maximum stress obtained in a three-point bend test. A base charge of Fe-28% Al-5% Cr alloy was used; as in previous studies this ternary alloy exhibited the highest tensile ductility of several alloys tested. Iron aluminide alloys are being considered for many structural uses, especially for applications where their excellent corrosion resistance is needed. Several alloy compositions developed at ORNL have been licensed to commercial vendors for development of scale-up procedures. With the licensees and other vendors, several applications for iron aluminides are being pursued.

  8. Weldability of iron aluminides

    SciTech Connect

    Zacharia, T.; David, S.A.

    1991-01-01

    Improvements in the ductility of iron aluminide alloys, achieved through control of composition and microstructure, has led to growing interest in using these materials for structural applications. weldability is a key issues in the utilization of these alloys for structural components. This paper describes the welding and welding behavior of an Fe{sub 3}Al alloy (FA-129) containing niobium and carbon. Weldability of this alloy has been found to be a strong function of composition, welding process and processing conditions. Crack free welds were made on both sheet and plate material using the electron beam (EB) welding process. Gas tungsten arc (GTA) welds, on the other hand, exhibited a tendency for delayed cold cracking. However, the study clearly demonstrated that successful welds can be made using matching filler metal and proper choice of processing conditions. 15 ref., 5 figs.

  9. Effect of grain size on the high temperature properties of B2 aluminides

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel

    1987-01-01

    Measurements of the slow plastic flow behavior of cobalt, iron and nickel B2 crystal structure aluminides were conducted on materials fabricated by metallurical techniques. Due to this processing, the aluminides invariably had small equiaxed grains, ranging in size from about 3 to 60 microns in diameter. Grain size was dependent on the extrusion temperature used for powder consolidation, and it proved to be remarkably stable at elevated temperatures. Mechanical properties of all three aluminides were determined via constant velocity compression testing in air between 1000 and 1400 K at strain rates ranging from approx. 10 to the minus 3 power to 10 to the minus 7 power s (-1).

  10. Development of nickel-iron aluminides

    SciTech Connect

    Liu, C.T.; Cathcart, J.V.; Goodwin, G.M.; Horton, J.A.; Lee, E.H.; Campbell, J.

    1987-09-01

    The objective of this program is to design and characterize new, improved high-temperature materials based on boron-doped Ni/sub 3/Al + Fe for structural use in advanced coal conversion systems. Chromium is a key alloying element that improves resistance to oxidation, corrosion, and environmental embrittlement in nickel-iron aluminides by promoting the rapid formation of protective oxide scales. Alloying with 3 to 7 at.% Cr dramatically reduces dynamic embrittlement in oxidizing environments at 400 to 800/sup 0/C. Chromium and iron additions increase the stability of the ordered body-centered cubic phase that is brittle at room temperature and weak at elevated temperatures. The formation of the B2 phase in the aluminides leads to lowering the tensile ductility at lower temperatures and the strength at higher temperatures. This study of alloying effects has led to the development of an aluminide with the composition: Ni-18.5 +- 0.5% Al-10.5 +- 0.5% Fe-7 +- 0.5% Cr-0.2% Zr-0.7% Mo-0.1% B( at.%). Corrosion studies have demonstrated that chromium additions of 7 at.% or greater were very effective in minimizing the sulfur attack on nickel-iron aluminides. Sulfidation protection can also be afforded by oxide films produced in air; however, the oxidation temperature should be 1000 to 1050/sup 0/C, and the alloys must contain 3 at.% or greater chromium. The nickel-iron aluminides developed were weldable using both the electron beam and gas tungsten arc processes. 19 refs., 24 figs., 9 tabs.

  11. Fracture of iron aluminide alloys

    SciTech Connect

    Alexander, D.J.; Sikka, V.K.

    1992-08-01

    Five heats of iron aluminide alloys have been prepared, and their impact fracture properties compared to FA-129 iron aluminide. The first was a simple ternary alloy of iron, aluminum, and chromium to match the FA-129 composition. The second was similar but with additions of zirconium and carbon. The third alloy had zirconium, carbon, niobium and molybdenum. Two heats were produced produced with reduced aluminum contents so that a disordered body-centered cubic structure would be present. The impact properties, microstructures, and fractography of these alloys were compared to FA-129. The ductile-to-brittle transition temperatures of all of the Fe{sub 3}Al alloys were similar, but the simple ternary alloy had a much higher upper-shelf energy. The reduced aluminum alloys had lower transition temperatures. The microstructures were, in general, coarse and anisotropic. The fracture processes were dominated by second-phase particles.

  12. Fracture of iron aluminide alloys

    SciTech Connect

    Alexander, D.J.; Sikka, V.K.

    1992-01-01

    Five heats of iron aluminide alloys have been prepared, and their impact fracture properties compared to FA-129 iron aluminide. The first was a simple ternary alloy of iron, aluminum, and chromium to match the FA-129 composition. The second was similar but with additions of zirconium and carbon. The third alloy had zirconium, carbon, niobium and molybdenum. Two heats were produced produced with reduced aluminum contents so that a disordered body-centered cubic structure would be present. The impact properties, microstructures, and fractography of these alloys were compared to FA-129. The ductile-to-brittle transition temperatures of all of the Fe{sub 3}Al alloys were similar, but the simple ternary alloy had a much higher upper-shelf energy. The reduced aluminum alloys had lower transition temperatures. The microstructures were, in general, coarse and anisotropic. The fracture processes were dominated by second-phase particles.

  13. Weldability and hot ductility of iron aluminides

    SciTech Connect

    Ash, D.I.; Edwards, G.R. . Center for Welding and Joining Research); David, S.A. )

    1991-05-01

    The weldability of iron aluminide alloys is discussed. Although readily welded with electron beam (EB) and gas-tungsten arc (GTA) techniques, iron aluminides are sometimes susceptible to cracking during cooling when welded with the GTA welding process. Taken into account are the effects of microstructural instability (grain growth), weld heat input (cooling rate) and environment on the hot ductility of an iron aluminide alloy designated FA-129. 64 refs., 59 figs., 3 tabs.

  14. Corrosion performance of iron aluminides

    SciTech Connect

    Natesan, K.

    1993-03-01

    Iron aluminides are being developed for use as structural materials and/or cladding alloys in fossil energy systems. Extensive development has been in progress on Fe[sub 3]Al-based alloys to improve the engineering ductility of these alloys. This paper describes results from the ongoing program to evaluate the corrosion performance of these alloys. The experimental program at Argonne National Laboratory involvesthermogravimetric analyses of alloys exposed to environments that simulate coal gasification and fluidized-bed combustion. Experiments were conducted at 650--1000[degrees]C in simulated oxygen/sulfur gas mixtures. In addition, oxidation/sulfidation behavior of several alumina-forming Fe-Al and Fe-Cr-Ni-Al alloys was determined for comparison with the corrosion rates obtained on iron aluminides. Other aspects of the program are corrosion evaluation of the aluminides in the presence of HC1-containing gases and in the presence of slag from a slogging gasifier. Results are used to establish threshold Al levels in the alloys for development of protective alumina scales. Thermal cycling tests are used to examine the spalling resistance of the scales.

  15. Corrosion performance of iron aluminides

    SciTech Connect

    Natesan, K.

    1993-03-01

    Iron aluminides are being developed for use as structural materials and/or cladding alloys in fossil energy systems. Extensive development has been in progress on Fe{sub 3}Al-based alloys to improve the engineering ductility of these alloys. This paper describes results from the ongoing program to evaluate the corrosion performance of these alloys. The experimental program at Argonne National Laboratory involvesthermogravimetric analyses of alloys exposed to environments that simulate coal gasification and fluidized-bed combustion. Experiments were conducted at 650--1000{degrees}C in simulated oxygen/sulfur gas mixtures. In addition, oxidation/sulfidation behavior of several alumina-forming Fe-Al and Fe-Cr-Ni-Al alloys was determined for comparison with the corrosion rates obtained on iron aluminides. Other aspects of the program are corrosion evaluation of the aluminides in the presence of HC1-containing gases and in the presence of slag from a slogging gasifier. Results are used to establish threshold Al levels in the alloys for development of protective alumina scales. Thermal cycling tests are used to examine the spalling resistance of the scales.

  16. Processing and applications of iron aluminides

    SciTech Connect

    Sikka, V.K.

    1994-09-01

    Iron aluminides are well known for their resistance to high- temperature sulfidizing and oxidizing environments. In order to take advantage of their excellent corrosion resistance, several methods for their processing have been identified. Issues with melting and processing are discussed detail. Effects of grain size and melting practice on low-temperature ductility are also presented. Many applications for iron aluminides are described.

  17. Corrosion resistance of iron aluminides

    SciTech Connect

    Natesan, K.

    1992-04-01

    Iron aluminides are being developed for use as structural materials and/or cladding alloys in fossil energy systems. Extensive development has been in progress on Fe{sub 3}Al-based alloys to improve their engineering ductility. This paper describes the corrosion performance of these alloys, determined at Argonne Naitonal Laboratory, in environments that simulate coal gasification and fluidized-bed combustion. Thermogravimetric analysis (TGA) was conducted at temperatures of 650--1000{degrees}C in air, 1 vol. % CO-CO{sub 2}, and H{sub 2}-H{sub 2}S environments at two sulfur activities. Upon completion of the kinetic runs, the morphology and structure of the scales formed on the alloy surface were evaluated by scanning electron microscopy and energy-dispersive X-ray analysis. Corrosion tests in simulated combustion environments were conducted at 900{degrees}C in the presence of reagent-grade CaSO{sub 4} and circulating-fluidized-bed deposits for 1000 and 3000 h. The test data on the aluminides from the TGA and combustion tests were compared with the corrosion performance of Type 310 stainless steel tested under similar conditions.

  18. Hot corrosion of the B2 nickel aluminides

    NASA Technical Reports Server (NTRS)

    Ellis, David L.

    1993-01-01

    The hot corrosion behavior of the B2 nickel aluminides was studied to determine the inherent hot corrosion resistance of the beta nickel aluminides and to develop a mechanism for the hot corrosion of the beta nickel aluminides. The effects of the prior processing of the material, small additions of zirconium, stoichiometry of the materials, and preoxidation of the samples were also examined. Additions of 2, 5, and 15 w/o chromium were used to determine the effect of chromium on the hot corrosion of the beta nickel aluminides and the minimum amount of chromium necessary for good hot corrosion resistance. The results indicate that the beta nickel aluminides have inferior inherent hot corrosion resistance despite their excellent oxidation resistance. Prior processing and zirconium additions had no discernible effect on the hot corrosion resistance of the alloys. Preoxidation extended the incubation period of the alloys only a few hours and was not considered to be an effective means of stopping hot corrosion. Stoichiometry was a major factor in determining the hot corrosion resistance of the alloys with the higher aluminum alloys having a definitely superior hot corrosion resistance. The addition of chromium to the alloys stopped the hot corrosion attack in the alloys tested. From a variety of experimental results, a complex hot corrosion mechanism was proposed. During the early stages of the hot corrosion of these alloys the corrosion is dominated by a local sulphidation/oxidation form of attack. During the intermediate stages of the hot corrosion, the aluminum depletion at the surface leads to a change in the oxidation mechanism from a protective external alumina layer to a mixed nickel-aluminum spinel and nickel oxide that can occur both externally and internally. The material undergoes extensive cracking during the later portions of the hot corrosion.

  19. Welding studies of nickel aluminide and nickel-iron aluminides

    SciTech Connect

    Santella, M.L.; David, S.A.; Horton, J.A.; White, C.L.; Liu, C.T.

    1985-08-01

    Because welding is often used during the fabrication of structural components, one of the key issues in the development of nickel aluminides and nickel-iron aluminides for engineering applications is their weldability. The goals of this study were to characterize weldment microstructures and to identify some of the factors controlling weldability of ductile Ni/sub 3/Al alloys. The alloys used in this initial study were Ni/sub 3/Al containing 500 wppm boron and Ni/sub 3/Al containing 10 at. % iron and either 500 wppm or 20 wppm boron. Full-penetration autogenous welds were made in sheet shock by the electron beam (EB) and gas tungsten arc (GTA) processes. The main process variables were travel speed and preheat. The as-welded coupons were examined visually and in detail by the usual optical and electron metallographic methods. Weldments of boron-doped Ni/sub 3/Al were composed of nearly 100% ordered ..gamma..' phase. Weldments of the nickel-iron aluminides were ..gamma..' + ..beta..' phase mixtures, with martensitic ..beta..' distributed interdendritically in the fusion zone and decorating grain boundaries in the heat-affected zone. All welds made in this particular boron-doped Ni/sub 3/Al alloy contained cracks. Weldability improved with the addition of iron, and defect-free welds were made in the nickel-iron aluminides by both EB and GTA welding. Nevertheless, the iron-containing alloys were susceptible to cracking, and their weldability was affected by boron concentration, welding speed, and (for GTA) gas shielding. Defect-free welds were found to have good tensile properties relative to those of the base metal. 34 refs., 17 figs., 2 tabs.

  20. Nickel aluminides and nickel-iron aluminides for use in oxidizing environments

    DOEpatents

    Liu, Chain T.

    1988-03-15

    Nickel aluminides and nickel-iron aluminides treated with hafnium or zirconium, boron and cerium to which have been added chromium to significantly improve high temperature ductility, creep resistance and oxidation properties in oxidizing environments.

  1. Ideal tensile strength of B2 transition-metal aluminides

    NASA Astrophysics Data System (ADS)

    Li, Tianshu; Morris, J. W., Jr.; Chrzan, D. C.

    2004-08-01

    The ideal tensile strengths of the B2 -type (CsCl) transition-metal aluminides FeAl , CoAl , and NiAl have been investigated using an ab initio electronic structure total energy method. The three materials exhibit dissimilar mechanical behaviors under the simulated ideal tensile tests along [001], [110], and [111] directions. FeAl is weakest in tension along [001] whereas CoAl and NiAl are strongest in the same direction. The weakness of FeAl along [001] direction is attributed to the instability introduced by the filling of antibonding d states.

  2. Iron Aluminide Hot Gas Filters

    SciTech Connect

    Hurley, J.; Brosious, S.; Johnson, M.

    1996-12-31

    Currently, high temperature filter systems are in the demonstration phase with the first commercial scale hot filter systems being installed on integrated gasification combined cycle (IGCC) and pressurized fluid bed combustion cycle (PBFC) systems (70 MW). They are dependent on the development of durable and economic high temperature filter systems. These filters are mostly ceramic tubes or candles. Ceramic filter durability has not been high. Failure is usually attributed to mechanical or thermal shock: they can also undergo significant changes due to service conditions. The overall objective of this project is to commercialize weldable, crack resistant filters which will provide several years service in advanced power processes. The specific objectives of this project are to develop corrosion resistant alloys and manufacturing processes to make Iron Aluminide filter media, and to use a ``short term`` exposure apparatus supported by other tests to identify the most promising candidate (alloy plus sintering cycle). The objectives of the next phases are to demonstrate long term corrosion stability for the best candidate followed by the production of fifty filters (optional).

  3. High-temperature corrosion of iron aluminides

    SciTech Connect

    Natesan, K.; Cho, W.D.

    1994-04-01

    Iron aluminides are being developed for use as structural materials and/or cladding alloys in fossil energy systems. Extensive development has been in progress on Fe{sub 3}Al-based alloys to improve their engineering ductility. This paper describes results from an ongoing program to evaluate the corrosion performance of these alloys. The experimental program at Argonne involves thermogravimetric analyses of alloys exposed to environments that simulate coal gasification and coal combustion. Corrosion experiments were conducted to determine the effect of gas flow rate and different levels of HCl at a gas temperature of 650 C on three heats of aluminide material, namely, FA 61, FA 129, and FAX. In addition, specimens of Type 316 stainless steel with an overlay alloying of iron aluminide were prepared by electrospark deposition and tested for their corrosion resistance. Detailed microstructural evaluations of tested specimens were performed. Results are used to assess the corrosion resistance of various iron aluminides for service in fossil energy systems that utilize coal as a feedstock.

  4. Hydrogen diffusivity in iron aluminides determined by subscale microhardness profiling

    SciTech Connect

    Banerjee, P.; Balasubramaniam, R.

    1998-10-05

    It has been well established that the poor ductility of iron aluminides at ambient temperatures is due to hydrogen embrittlement. Hydrogen is produced by the reaction of moisture with the iron aluminide and enters the lattice to cause embrittlement. Therefore, one of the important factors that needs to be understood is the diffusion of hydrogen in iron aluminides. There are relatively few studies that have determined the diffusivity of hydrogen in iron aluminides. The apparent hydrogen diffusion coefficient can be easily measured by the technique of subsurface microhardness profiling after cathodic hydrogen charging. This technique has been utilized to determine room temperature hydrogen diffusivity in Al-Li alloys and several austenitic stainless steels. A similar technique was also used to determine high temperature oxygen and nitrogen diffusivities in titanium aluminides. The aim of the present paper is to determine the diffusivity of hydrogen, in stoichiometric Fe{sub 3}Al and iron aluminides alloyed with Cr nd Ti, by this technique.

  5. Weld overlay cladding with iron aluminides

    SciTech Connect

    Goodwin, G.M.

    1995-08-01

    The hot and cold cracking tendencies of some early iron aluminide alloy compositions have limited their use in applications where good weldability is required. Using hot crack testing techniques invented at ORNL, and experimental determinations of preheat and postweld heat treatment needed to avoid cold cracking, we have developed iron aluminide filler metal compositions which can be successfully used to weld overlay clad various substrate materials, including 9Cr-1Mo steel, 2-1/4Cr-1Mo steel, and 300-series austenitic stainless steels. Dilution must be carefully controlled to avoid crack-sensitive deposit compositions. The technique used to produce the current filler metal compositions is aspiration-casting, i.e. drawing the liquid from the melt into glass rods. Future development efforts will involve fabrication of composite wires of similar compositions to permit mechanized gas tungsten arc (GTA) and/or gas metal arc (GMA) welding.

  6. Ordered iron aluminide alloys having an improved room-temperature ductility and method thereof

    DOEpatents

    Sikka, Vinod K.

    1992-01-01

    A process is disclosed for improving the room temperature ductility and strength of iron aluminide intermetallic alloys. The process involves thermomechanically working an iron aluminide alloy by means which produce an elongated grain structure. The worked alloy is then heated at a temperature in the range of about 650.degree. C. to about 800.degree. C. to produce a B2-type crystal structure. The alloy is rapidly cooled in a moisture free atmosphere to retain the B2-type crystal structure at room temperature, thus providing an alloy having improved room temperature ductility and strength.

  7. Fabrication and processing of iron aluminides

    SciTech Connect

    Sikka, V.K.; Viswanathan, S.

    1992-07-01

    The Fe{sub 3}Al-based alloys have been shown to exhibit room-temperature ductility values of 15 to 19% by the control of composition and thermomechanical processing steps. The scale-up of one of the compositions to 2270-kg (5000-lb) electroslag-remelted (ESR) round ingot and 3272-kg (7200-lb) vacuum-induction-melted (VIM) slab ingot is described. Microstructural and mechanical property data are presented on small pieces sectioned from these ingots. The effects of final rolling temperature and the final annealing treatment on room-temperature ductility were investigated for the ESR ingot. A study of iron-aluminide binary alloys revealed that the environmental effects on room-temperature ductility values were absent for {le}8.5 wt % Al. The increasing aluminum content and the development of ordered structure resulted in increased environmental effects. Applications and a brief description of their status are described. Based on the combined property and cost advantage, continued development of iron aluminide is recommended.

  8. Ductility enhancement of iron-aluminide alloys

    SciTech Connect

    Sikka, V.K. )

    1991-07-01

    Iron aluminides based on Fe{sub 3}Al are ordered intermetallic alloys that offer good oxidation resistance, excellent sulfidation resistance, and low material cost. These materials also conserve strategic elements such as chromium and have a lower density than stainless steels. However, limited ductility at ambient temperature and a sharp drop in strength above 600C have been major deterrents to their acceptance for structural applications. This paper presents results on iron aluminides with room-temperature elongations of 15 to 20%. Ductility values were improved by a combination of thermomechanical processing and heat-treatment control. This method of ductility improvement has been demonstrated for a range of compositions. The data presented in this paper suggest that the Fe{sub 3}Al-based compositions tested are sensitive to environmental effects. The environment of concern is moisture in air that reacts with aluminum to form hydrogen at the metal surface. The hydrogen produced is adsorbed and absorbed in the specimens during plastic strain and results in low room-temperature ductilities. Results showed that the use of highly elongated grains produced by warm working increases ductility. A special heat treatment produces an additional improvement in ductility.

  9. Fabrication and processing of iron aluminides

    SciTech Connect

    Sikka, V.K.; Viswanathan, S.

    1992-01-01

    The Fe{sub 3}Al-based alloys have been shown to exhibit room-temperature ductility values of 15 to 19% by the control of composition and thermomechanical processing steps. The scale-up of one of the compositions to 2270-kg (5000-lb) electroslag-remelted (ESR) round ingot and 3272-kg (7200-lb) vacuum-induction-melted (VIM) slab ingot is described. Microstructural and mechanical property data are presented on small pieces sectioned from these ingots. The effects of final rolling temperature and the final annealing treatment on room-temperature ductility were investigated for the ESR ingot. A study of iron-aluminide binary alloys revealed that the environmental effects on room-temperature ductility values were absent for {le}8.5 wt % Al. The increasing aluminum content and the development of ordered structure resulted in increased environmental effects. Applications and a brief description of their status are described. Based on the combined property and cost advantage, continued development of iron aluminide is recommended.

  10. Hydrogen cracking behavior in an iron aluminide alloy weldment

    SciTech Connect

    Fasching, A.A.; Edwards, G.R.; Ash, D.I.; David, S.A.

    1995-02-01

    Significant interest exists in developing polycrystalline, long-range ordered iron-aluminide alloys for high temperature applications because of their unique properties such as superior oxidation resistance. However, detrimental properties such as low room temperature ductility and poor weldability restrict the use of iron-aluminides in structural applications. This paper describes the results of hot dutility tests conducted on iron-aluminide alloy FA-129 to determine the effect of test temperature, grain size and atmosphere on the ductility. Also, a preliminary study was performed to determine the hydrogen cold cracking sensitivity of weldments produced in varying atmospheres of water vapor.

  11. Environmental effects on iron aluminide

    SciTech Connect

    DeVan, J.H.; Tortorelli, P.F.; Bennett, M.J.

    1994-09-01

    Air oxidation tests of iron-aluminum alloys containing 16 and 28 at. % Al, were conducted at 1300C to determine the effect of alloy composition and section thickness on time to breakdown of oxidation resistance. Oxidation rates of 16% Al were significantly higher than for 28% Al (Fe{sub 3}Al). The times over which the oxide scales remained protective correlated with extent of aluminum depletion of the alloy matrix and were therefore a direct function of the initial aluminum content of the alloy, the section thickness, and oxidation rate. The oxidation rate of the Fe{sub 3}Al alloys was significantly reduced by addition of 0.1% Zr, which improved the adherence of the scale during thermal cycling to room temperature. However, the oxidation rates of the Fe{sub 3}Al alloys were higher at 1300C than those reported for oxide-dispersion-strengthened (ODS) Fe-18%Cr-10%Al alloys containing Y{sub 2}O{sub 3}. Times to the onset of breakaway oxidation were similar for zirconium-containing Fe{sub 3}Al and the ODS alloys, the lower oxidation rate of the latter offsetting the higher initial aluminum of the former. Studies of the effects of chlorine (HCl) on the oxidation/sulfidation resistance of Fe{sub 3}Al- based alloys were conducted using test facilities at the National Physical Laboratory (NPL) in the United Kingdom. Alloys were exposed to a test gas composed of CO{sub 2}, H{sub 2}, H{sub 2}O, and H{sub 2}S Plus 1000--5000 ppm HCl at 450 and 550C for 1000 h. Weight gains were relatively low and were generally less than companion specimens of Fe-Cr-Al alloys.

  12. Precipitation-strengthening effects in iron-aluminides

    SciTech Connect

    Maziasz, P.J.; McKamey, C.G.; Goodwin, G.M.

    1995-05-01

    The purpose of this work is to produce precipitation to improve both high-temperature strength and room-temperature ductibility in FeAl-type(B2 phase) iron-aluminides. Previous work has focused on primarily wrought products, but stable precipitates can also refine the grain size and affect the properties of as-cast and/or welded material as well. New work began in FY 1994 on the properties of these weldable, strong FeAl alloys in the as-cast condition. Because the end product of this project is components for industry testing, simpler and better (cheaper, near-net-shape) processing methods must be developed for industrial applications of FeAl alloys.

  13. Preliminary investigation of inertia friction welding B2 aluminides

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Moore, Thomas J.; Kuruzar, Daniel L.

    1987-01-01

    An attempt is made to achieve inertia friction-welding in FeAl and NiAl samples, taking into account their intermetallics' compositions, extrusion parameters, and microstructural data. The energy required for the weld is stored in a rotating flywheel mass attached to one of the two pieces to be joined; when enough energy is introduced, the flywheel is disconnected and an axial load is applied which forces the spinning piece against the stationary one, converting the energy into heat by means of friction. Due to the inherent brittleness of the aluminides, a step-load program was used in which an initial, low-pressure heat buildup increased the work pieces' ductility.

  14. Preparation and fabrication of iron aluminides

    SciTech Connect

    Sikka, V.K.; Baldwin, R.H.; Blakely, K.S.; Hatfield, E.C.; Howell, C.R.; McKamey, C.G.

    1991-01-01

    The Fe{sub 3}AL-based iron aluminides are under development at Oak Ridge National Laboratory (ORNL) for a range of fossil energy applications. The room-temperature ductility, which was the major drawback for their use, has been increased from 8% to a more usable range of 15 to 20%. The commercial application of these alloys requires information regarding their melting and fabrication. This paper presents the recent data regarding alloy compositions, melting and fabrication, and properties. The Fe{sup 3}AL alloy (FA-129) was vacuum-induction melted in a MgO crucible, with a slight pickup of magnesium. This magnesium pickup was not detrimental to the processing of the ingot. The magnesium content has been subsequently reduced by either vacuum-arc remelting or electroslag remelting. The ingots were hot worked without any problems at ORNL, Special Metals Corporation (New Hartford, New York), and Precision Rolled Products (Reno, Nevada). Tensile and creep properties of the ingots in this study were similar to those observed in previous heats. 10 refs., 6 figs., 1 tab.

  15. Iron aluminides and nickel aluminides as materials for chemical air separation

    DOEpatents

    Kang, D.

    1991-01-29

    The present invention is directed to a chemical air separation process using a molten salt solution of alkali metal nitrate and nitrite wherein the materials of construction of the containment for the process are chosen from intermetallic alloys of nickel and/or iron aluminide wherein the aluminum content is 28 atomic percent or greater to impart enhanced corrosion resistance.

  16. Iron aluminides and nickel aluminides as materials for chemical air separation

    DOEpatents

    Kang, Doohee

    1991-01-01

    The present invention is directed to a chemical air separation process using a molten salt solution of alkali metal nitrate and nitrite wherein the materials of construction of the containment for the process are chosen from intermetallic alloys of nickel and/or iron aluminide wherein the aluminum content is 28 atomic percent or greater to impart enhanced corrosion resistance.

  17. Tensile fracture of iron-iron aluminide foil composites

    SciTech Connect

    Rawers, J.C. . Albany Research Center)

    1994-03-15

    Because intermetallics have limited ductility, it is not possible to form composite structures that require extensive plastic deformation during processing. However, the formation of metal-intermetallic composites by Self-propagating, High-temperature, Synthesis, (SHS) reactions has the advantage that materials may be preformed into the desired final shape prior to forming the intermetallic phase. Recently, the SHS process has been used to form metal-intermetallic composites in one step processing. Metal-metal aluminide composites were formed by sandwiching Al sheets between Fe, Ni, or Ti sheets. Then, by heating the layered composition, an SHS reaction occurred at the metal-aluminum interface. The resulting exothermic reaction melts the aluminum which then reacts with the surface of the other metal producing a liquid intermetallic phase. When the metal-intermetallic system cools the resulting structure is a tightly bonded layered composite. The fracture characteristics of any material and especially of composites are important to know before applications can be found for the material. The initiation and propagation of cracks in one of the composite phases, and the propagation of cracks through the interface and through the second phase controls the eventual failure of a material. In this study, iron-iron aluminide composites formed by SHS reactions were evaluated for tensile properties and failure characteristics.

  18. Commercialization of nickel and iron aluminides

    SciTech Connect

    Sikka, V.K.

    1996-12-31

    Metallurgists are taught that intermetallics are brittle phases and should be avoided in alloys of commercial interest. This education is so deeply rooted that irrespective of significant advances made in ductilization of aluminides,the road to their acceptance commercialization is extremely difficult. This paper identifies the requirements for commercialization of any new alloys and reports the activities carried out to commercialize Ni and Fe aluminides. The paper also identifies areas which meet the current commercialization requirements and areas needing additional effort.

  19. Effects of titanium and zirconium on iron aluminide weldments

    SciTech Connect

    Burt, R.P.; Edwards, G.R.; David, S.A.

    1996-08-01

    Iron aluminides form a coarse fusion zone microstructure when gas-tungsten arc welded. This microstructure is susceptible to hydrogen cracking when water vapor is present in the welding environment. Because fusion zone microstructural refinement can reduce the hydrogen cracking susceptibility, titanium was used to inoculate the weld pool in iron aluminide alloy FA-129. Although the fusion zone microstructure was significantly refined by this method, the fracture stress was found to decrease with titanium additions. This decrease is attributed to an increase in inclusions at the grain boundaries.

  20. Weld overlay cladding with iron aluminides

    SciTech Connect

    Goodwin, G.M.

    1996-11-01

    The hot and cold cracking tendencies of some early iron aluminide alloy compositions limited their use to applications where good weldability was not required. Considerable progress has been made toward improving this situation. Using hot crack testing techniques developed at ORNL and a systematic study of alloy compositional effects, we have established a range of compositions within which hot cracking resistance is very good, essentially equivalent to stainless steel. Cold cracking, however, remains an issue, and extensive efforts are continuing to optimize composition and welding parameters, especially preheat and postweld heat treatment, to minimize its occurrence. In terms of filler metal and process development, we have progressed from sheared strip through aspiration cast rod and shielded metal arc electrodes to the point where we can now produce composite wire with a steel sheath and aluminum core in coil form, which permits the use of both the gas tungsten arc and gas metal arc processes. This is a significant advancement in that the gas metal arc process lends itself well to automated welding, and is the process of choice for commercial weld overlay applications. Using the newly developed filler metals, we have prepared clad specimens for testing in a variety of environments both in-house and outside ORNL, including laboratory and commercial organizations. As a means of assessing the field performance of this new type of material, we have modified several non-pressure boundary boiler components, including fuel nozzles and port shrouds, by introducing areas of weld overlay in strategic locations, and have placed these components in service in operating boilers for a side-by-side comparison with conventional corrosion-resistant materials.

  1. Damping and modulus measurements in B2 transition metal aluminides

    NASA Technical Reports Server (NTRS)

    Harmouche, M. R.; Wolfenden, A.

    1985-01-01

    The polycrystalline intermetallic alloys FeAl (50.9 to 58.2 percent Fe), NiAl (49.2 to 55.9 percent Ni) and CoAl (48.5 to 52.3 percent Co) have the B2 structure and are of interest for high temperature applications. The PUCOT (piezoelectric ultrasonic composite oscillator technique) has been used to measure mechanical damping or internal friction and Young's modulus has been used as a function of temperature and composition for these materials. The modulus data for six CoAl alloys at temperatures up to 1300 K are presented. Examples are given of the strain amplitude dependence of internal friction for four CoAl alloys. The curves showed the break away phenomenon and are interpreted in terms of a theory dealing with the pinning of dislocation lines and their eventual break away at large strain amplitudes. The dislocation density was calculated to be about 10 to the 8th per sq m. For all the compositions (X1) of CoAl studied, a single equation could be fitted to the data.

  2. Solute hardening and softening effects in B2 nickel aluminides

    SciTech Connect

    Pike, L.M.; Liu, C.T.; Anderson, I.M.; Chang, Y.A.

    1998-11-01

    The effect of substitutional solute additions including Fe, Mn, and Pd on the hardness of B2-ordered NiAl alloys was investigated. The solid solution hardening behavior of intermetallics is more complex than that of typical metallic solid solutions because of complications arising from the site preference of the solute as well as the effects of the solute on the concentrations of other point defects, e.g., vacancies and anti-site defects. For this reason, care was taken to experimentally establish solute site preferences and point defect concentrations in the NiAl alloys before analyzing the hardness data. By taking these factors into account it was possible to rationalize the observed unusual hardening effects. Three distinct categories of solid solution hardening behavior were encountered. The first was hardening by the solute addition itself. This was observed in the case of Pd additions to Al-poor NiAl. However, when fe or Mn is added to Al-poor NiAl a second category is observed; these elements are seen to soften the material. The third category of behavior is observed when Fe is added to NiAl with a constant Al concentration of 50 at. %. In this case it is vacancies, rather than solute atoms, which harden the material.

  3. Effects of titanium and zirconium on iron aluminide weldments

    SciTech Connect

    Mulac, B.L.; Edwards, G.R.; Burt, R.P.; David, S.A.

    1997-12-01

    When gas-tungsten arc welded, iron aluminides form a coarse fusion zone microstructure which is susceptible to hydrogen embrittlement. Titanium inoculation effectively refined the fusion zone microstructure in iron aluminide weldments, but the inoculated weldments had a reduced fracture strength despite the presence of a finer microstructure. The weldments fractured by transgranular cleavage which nucleated at cracked second phase particles. With titanium inoculation, second phase particles in the fusion zone changed shape and also became more concentrated at the grain boundaries, which increased the particle spacing in the fusion zone. The observed decrease in fracture strength with titanium inoculation was attributed to increased spacing of second phase particles in the fusion zone. Current research has focused on the weldability of zirconium- and carbon-alloyed iron aluminides. Preliminary work performed at Oak Ridge National Laboratory has shown that zirconium and carbon additions affect the weldability of the alloy as well as the mechanical properties and fracture behavior of the weldments. A sigmajig hot cracking test apparatus has been constructed and tested at Colorado School of Mines. Preliminary characterization of hot cracking of three zirconium- and carbon-alloyed iron aluminides, each containing a different total concentration of zirconium at a constant zirconium/carbon ratio of ten, is in progress. Future testing will include low zirconium alloys at zirconium/carbon ratios of five and one, as well as high zirconium alloys (1.5 to 2.0 atomic percent) at zirconium/carbon ratios of ten to forty.

  4. Iron aluminides and the inventor of the year

    SciTech Connect

    Krause, C.

    1990-01-01

    ORNL is working on iron aluminide alloys, which are of interest to the fossil fuel industry because they are highly resistant to the corrosion induced by the sulfur-bearing gaseous effluents of coal combustion and conversion. Chromium added to the alloy increases the ductility.

  5. High-temperature fabricable nickel-iron aluminides

    DOEpatents

    Liu, Chain T.

    1988-02-02

    Nickel-iron aluminides are described that are based on Ni.sub.3 Al, and have significant iron content, to which additions of hafnium, boron, carbon and cerium are made resulting in Ni.sub.3 Al base alloys that can be fabricated at higher temperatures than similar alloys previously developed. Further addition of molybdenum improves oxidation and cracking resistance. These alloys possess the advantages of ductility, hot fabricability, strength, and oxidation resistance.

  6. Primary fabrication processes for nickel and iron aluminides

    SciTech Connect

    Weir, J.R. Jr.; Sikka, V.K.

    1991-01-01

    Alloys based on the intermetallic compounds Ni{sub 3}Al and Fe{sub 3}Al have been developed. Intermetallic compounds are characteristically brittle at room temperature, and some are also brittle at elevated temperatures. Nickel-aluminide alloys have been made ductile by alloying with a small amount of boron (200 ppm by weight) and adjusting the aluminum content to 24 at. % or less. Iron-aluminide alloys are ductile when chromium is added (>wt 2%) and the aluminum is adjusted to 28 at %. These alloys begin ordering upon solidification; therefore, a greater shrinkage must be accommodated during casting. The hot-working temperature window'' for the nickel-aluminide alloy is very narrow; however, the alloy can be cold-worked large amounts. Iron-aluminide alloys have a very broad hot-working temperature range but have limited ductility (<20%) at room temperature. The strength and oxidation resistance of these alloys are such that many potential applications exist. Commercialization is in progress. 15 refs., 14 figs., 2 tabs.

  7. Development of nickel and iron aluminides and their applications

    SciTech Connect

    Sikka, V.K.

    1991-01-01

    Alloys based on the intermetallic compounds Ni{sub 3}Al and Fe{sub 3}Al have been developed. Intermetallic compounds are characteristically brittle at room temperature, and some are also brittle at elevated temperatures. Nickel-aluminide alloys have been made ductile by alloying with a small amount of boron (200 ppM by weight) and adjusting the aluminum content to 24 at. % or less. Iron-aluminide alloys are ductile when chromium is added (>wt. 2%) and the aluminum is adjusted to 28 at. %. These alloys begin ordering upon solidification; therefore, a greater shrinkage must be accommodated during casting. The hot-working temperature window'' for the nickel-aluminide alloy is very narrow; however, the alloy can be cold-worked large amounts. Iron-aluminide alloys have a very broad hot-working temperature range but have limited ductility (<20%) at room temperature. The strength and oxidation resistance of these alloys are such that many potential applications exist. Commercialization is in progress. 15 refs., 14 figs.

  8. Microstructural effects on the oxidation of iron aluminide

    NASA Astrophysics Data System (ADS)

    Hale, Peter M.

    This work addresses the impact of processing and microstructure on the oxide chemistry and short-term isothermal oxidation rate, over the first 24h of oxidation, for the B2 iron aluminide, Fe-40Al. Research interests in iron-aluminum alloys, used for high temperature structural applications, are primarily concerned with the improvement of high temperature oxidation performance and mechanical properties. The oxidation performance of alloys with aluminum contents below 20at% is dependent upon processing and microstructure. Before this work, it was not established if there was any impact of material processing and microstructure on the oxidation performance of the high aluminum content Fe-40Al alloy. This study utilized eight industrial processes to produce six different material conditions. Among the characteristics of the microstructures produced were grain sizes from 2 to ≥500mum, oxygen contents from 0--2.6at%, and powder particle surface area-to-volume ratios from 0--0.6 m2/cm3. For the six materials tested, short-term (24h) isothermal oxidation rates were determined at 700, 750, and 800°C. The resultant rates were then used to determine the relationship between the oxidation rate constant and temperature. The chemistry, physical characteristics, and structure of the oxides formed were then characterized. It was concluded that microstructure has a limited impact on oxidation properties: no practical impact was observed on oxidation rate; an initial transient oxide layer formed independent of microstrucure; microstructure can be used to control the formation of oxide-metal interfacial voids, formed during the oxidation process; and oxide inclusion "pegs" serve to improve oxide adhesion. Additionally it was observed that contamination from hot pressing contributed to the formation of oxide nodules during oxidation. Overall the isothermal oxidation properties during the first 24h of exposure proved to be robust over many combinations of microstructures.

  9. Iron aluminide alloy container for solid oxide fuel cells

    DOEpatents

    Judkins, Roddie Reagan; Singh, Prabhakar; Sikka, Vinod Kumar

    2000-01-01

    A container for fuel cells is made from an iron aluminide alloy. The container alloy preferably includes from about 13 to about 22 weight percent Al, from about 2 to about 8 weight percent Cr, from about 0.1 to about 4 weight percent M selected from Zr and Hf, from about 0.005 to about 0.5 weight percent B or from about 0.001 to about 1 weight percent C, and the balance Fe and incidental impurities. The iron aluminide container alloy is extremely resistant to corrosion and metal loss when exposed to dual reducing and oxidizing atmospheres at elevated temperatures. The alloy is particularly useful for containment vessels for solid oxide fuel cells, as a replacement for stainless steel alloys which are currently used.

  10. Liquid-phase sintering of iron aluminide-bonded ceramics

    SciTech Connect

    Schneibel, J.H.; Carmichael, C.A.

    1995-12-31

    Iron aluminide intermetallics exhibit excellent oxidation and sulfidation resistance and are therefore considered as the matrix in metal matrix composites, or the binder in hard metals or cermets. In this paper the authors discuss the processing and properties of liquid-phase sintered iron aluminide-bonded ceramics. It is found that ceramics such as TiB{sub 2}, ZrB{sub 2}, TiC, and WC may all be liquid phase-sintered. nearly complete densification is achieved for ceramic volume fractions ranging up to 60%. Depending on the composition, room temperature three point-bend strengths and fracture toughnesses reaching 1,500 MPa and 30 MPa m{sup 1/2}, respectively, have been found. Since the processing was carried out in a very simple manner, optimized processing is likely to result in further improvements.

  11. Iron aluminide alloy coatings and joints, and methods of forming

    DOEpatents

    Wright, Richard N.; Wright, Julie K.; Moore, Glenn A.

    1994-01-01

    A method of joining two bodies together, at least one of the bodies being predominantly composed of metal, the two bodies each having a respective joint surface for joining with the joint surface of the other body, the two bodies having a respective melting point, includes the following steps: a) providing aluminum metal and iron metal on at least one of the joint surfaces of the two bodies; b) after providing the aluminum metal and iron metal on the one joint surface, positioning the joint surfaces of the two bodies in juxtaposition against one another with the aluminum and iron positioned therebetween; c) heating the aluminum and iron on the juxtaposed bodies to a temperature from greater than or equal to 600.degree. C. to less than the melting point of the lower melting point body; d) applying pressure on the juxtaposed surfaces; and e) maintaining the pressure and the temperature for a time period effective to form the aluminum and iron into an iron aluminide alloy joint which bonds the juxtaposed surfaces and correspondingly the two bodies together. The method can also effectively be used to coat a body with an iron aluminide coating.

  12. Iron aluminide alloy coatings and joints, and methods of forming

    DOEpatents

    Wright, R.N.; Wright, J.K.; Moore, G.A.

    1994-09-27

    Disclosed is a method of joining two bodies together, at least one of the bodies being predominantly composed of metal, the two bodies each having a respective joint surface for joining with the joint surface of the other body, the two bodies having a respective melting point, includes the following steps: (a) providing aluminum metal and iron metal on at least one of the joint surfaces of the two bodies; (b) after providing the aluminum metal and iron metal on the one joint surface, positioning the joint surfaces of the two bodies in juxtaposition against one another with the aluminum and iron positioned therebetween; (c) heating the aluminum and iron on the juxtaposed bodies to a temperature from greater than or equal to 600 C to less than the melting point of the lower melting point body; (d) applying pressure on the juxtaposed surfaces; and (e) maintaining the pressure and the temperature for a time period effective to form the aluminum and iron into an iron aluminide alloy joint which bonds the juxtaposed surfaces and correspondingly the two bodies together. The method can also effectively be used to coat a body with an iron aluminide coating.

  13. Identification of thermodynamically stable ceramic reinforcement materials for iron aluminide matrices

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1990-01-01

    Aluminide-base intermetallic matrix composites are currently being considered as potential high-temperature materials. One of the key factors in the selection of a reinforcement material is its chemical stability in the matrix. In this study, chemical interactions between iron aluminides and several potential reinforcement materials, which include carbides, oxides, borides, and nitrides, are analyzed from thermodynamic considerations. Several chemically compatible reinforcement materials are identified for the iron aluminides with Al concentrations ranging from 40 to 50 at. pct.

  14. Oxide Dispersion Strengthened Iron Aluminide by CVD Coated Powders

    SciTech Connect

    Asit Biswas Andrew J. Sherman

    2006-09-25

    This I &I Category2 program developed chemical vapor deposition (CVD) of iron, aluminum and aluminum oxide coated iron powders and the availability of high temperature oxidation, corrosion and erosion resistant coating for future power generation equipment and can be used for retrofitting existing fossil-fired power plant equipment. This coating will provide enhanced life and performance of Coal-Fired Boilers components such as fire side corrosion on the outer diameter (OD) of the water wall and superheater tubing as well as on the inner diameter (ID) and OD of larger diameter headers. The program also developed a manufacturing route for readily available thermal spray powders for iron aluminide coating and fabrication of net shape component by powder metallurgy route using this CVD coated powders. This coating can also be applid on jet engine compressor blade and housing, industrial heat treating furnace fixtures, magnetic electronic parts, heating element, piping and tubing for fossil energy application and automotive application, chemical processing equipment , heat exchanger, and structural member of aircraft. The program also resulted in developing a new fabrication route of thermal spray coating and oxide dispersion strengthened (ODS) iron aluminide composites enabling more precise control over material microstructures.

  15. Mechanisms of defect complex formation and environmental-assisted fracture behavior of iron aluminides

    SciTech Connect

    Cooper, B.R.; Muratov, L.S.; Kang, B.S.J.; Li, K.Z.

    1997-12-01

    Iron aluminide has excellent corrosion resistance in high-temperature oxidizing-sulfidizing environments; however, there are problems at room and medium temperature with hydrogen embrittlement as related to exposure to moisture. In this research, a coordinated computational modeling/experimental study of mechanisms related to environmental-assisted fracture behavior of selected iron aluminides is being undertaken. The modeling and the experimental work will connect at the level of coordinated understanding of the mechanisms for hydrogen penetration and for loss of strength and susceptibility to fracture. The focus of the modeling component at this point is on the challenging question of accurately predicting the iron vacancy formation energy in Fe{sub 3}A{ell} and the subsequent tendency, if present, for vacancy clustering. The authors have successfully performed, on an ab initio basis, the first calculation of the vacancy formation energy in Fe{sub 3}A{ell}. These calculations include lattice relaxation effects which are quite large. This has significant implications for vacancy clustering effects with consequences to be explored for hydrogen diffusion. The experimental work at this stage has focused on the relationship of the choice and concentration of additives to the improvement of resistance to hydrogen embrittlement and hence to the fracture behavior. For this reason, comparative crack growth tests of FA-186, FA-187, and FA-189 iron aluminides (all with basic composition of Fe-28A{ell}-5Cr, at % with micro-alloying additives of Zr, C or B) under, air, oxygen, or water environment have been performed. These tests showed that the alloys are susceptible to room temperature hydrogen embrittlement in both B2 and DO{sub 3} conditions. Test results indicated that FA-187, and FA-189 are intrinsically more brittle than FA-186.

  16. Iron aluminide alloys with improved properties for high temperature applications

    DOEpatents

    McKamey, C.G.; Liu, C.T.

    1990-10-09

    An improved iron aluminide alloy of the DO[sub 3] type is described that has increased room temperature ductility and improved high elevated temperature strength. The alloy system further is resistant to corrosive attack in the environments of advanced energy conversion systems such as those using fossil fuels. The resultant alloy is relatively inexpensive as contrasted to nickel based and high nickel steels currently utilized for structural components. The alloy system consists essentially of 26--30 at. % aluminum, 0.5--10 at. % chromium, 0.02--0.3 at. % boron plus carbon, up to 2 at. % molybdenum, up to 1 at. % niobium, up to 0.5 at. % zirconium, up to 0.1 at. % yttrium, up to 0.5 at. % vanadium and the balance iron. 3 figs.

  17. Iron aluminide alloys with improved properties for high temperature applications

    DOEpatents

    McKamey, Claudette G.; Liu, Chain T.

    1990-01-01

    An improved iron aluminide alloy of the DO.sub.3 type that has increased room temperature ductility and improved high elevated temperature strength. The alloy system further is resistant to corrosive attack in the environments of advanced energy corrosion systems such as those using fossil fuels. The resultant alloy is relatively inexpensive as contrasted to nickel based and high nickel steels currently utilized for structural components. The alloy system consists essentially of 26-30 at. % aluminum, 0.5-10 at. % chromium, 0.02-0.3 at. % boron plus carbon, up to 2 at. % molybdenum, up to 1 at. % niobium, up to 0.5 at. % zirconium, up to 0.1 at. % yttrium, up to 0.5 at. % vanadium and the balance iron.

  18. Investigation of Iron Aluminide Weld Overlays

    SciTech Connect

    Banovic, S.W.; DuPont, J.B.; Levin, B.F.; Marder, A.R.

    1999-08-02

    Conventional fossil fired boilers have been retrofitted with low NO(sub)x burners in order for the power plants to comply with new clean air regulations. Due to the operating characteristics of these burners, boiler tube sulfidation corrosion typically has been enhanced resulting in premature tube failure. To protect the existing panels from accelerated attack, weld overlay coatings are typically being applied. By depositing an alloy that offers better corrosion resistance than the underlying tube material, the wastage rates can be reduced. While Ni-based and stainless steel compositions are presently providing protection, they are expensive and susceptible to failure via corrosion-fatigue due to microsegregation upon solidification. Another material system presently under consideration for use as a coating in the oxidation/sulfidation environments is iron-aluminum. These alloys are relatively inexpensive, exhibit little microsegregation, and show excellent corrosion resistance. However, their use is limited due to weldability issues and their lack of corrosion characterization in simulated low NO(sub)x gas compositions. Therefore a program was initiated in 1996 to evaluate the use of iron-aluminum weld overlay coatings for erosion/corrosion protection of boiler tubes in fossil fired boilers with low NO(sub)x burners. Investigated properties included weldability, corrosion behavior, erosion resistance, and erosion-corrosion performance.

  19. Al2O3 Scale Development on Iron Aluminides

    SciTech Connect

    Zhang, Xiao-Feng; Thaidigsmann, Katja; Ager, Joel; Hou, Peggy Y.

    2005-11-10

    The structure and phase of the Al{sub 2}O{sub 3} scale that forms on an Fe{sub 3}Al-based alloy (Fe-28Al-5Cr) (at %) was investigated by transmission electron microscopy (TEM) and photoluminescence spectroscopy (PL). Oxidation was performed at 900 C and 1000 C for up to 190 min. TEM revealed that single-layer scales were formed after short oxidation times. Electron diffraction was used to show that the scales are composed of nanoscale crystallites of the {theta}, {gamma}, and {alpha} phases of alumina. Band-like structure was observed extending along three 120{sup o}-separated directions within the surface plane. Textured {theta} and {gamma} grains were the main components of the bands, while mixed {alpha} and transient phases were found between the bands. Extended oxidation produced a double-layered scale structure, with a continuous {alpha} layer at the scale/alloy interface, and a {gamma}/{theta} layer at the gas surface. The mechanism for the formation of Al{sub 2}O{sub 3} scales on iron aluminide alloys is discussed and compared to that for nickel aluminide alloys.

  20. Ordered iron aluminide alloys having an improved room-temperature ductility and method thereof

    SciTech Connect

    Sikka, V.K.

    1992-01-28

    This patent describes a method for improving the room temperature ductility and high temperature strength of iron aluminide intermetallic alloys. It comprises: thermomechanically working of the alloys ; heating the alloys; and rapidly cooling the alloys.

  1. Hot extrusion of B2 iron aluminide powders

    NASA Technical Reports Server (NTRS)

    Strothers, S.; Vedula, K.

    1987-01-01

    The objective of the study was to investigate the effect of powder and processing variables on the microstructure and resultant tensile properties of an extruded FeAlZrB alloy. For a given powder particle size, increasing the extrusion temperature from 1250 to 1450 K is found to increase the grain size and produce a more uniform microstructure. At high extrusion temperatures, where grain boundary mobility is high, powder size is not critical in determining the grain size. The addition of Y2O3 dispersion (1 vol pct) by mechanical alloying makes it possible to obtain very fine-grained materials at low and high extrusion temperatures.

  2. Development of Improved Iron-Aluminide Filter Tubes and Elements

    SciTech Connect

    Judkins, R.R.; Sutton, T.G.; Miller, C.J.; Tortorelli, P.F.

    2008-01-14

    The purpose of this Cooperative Research and Development Agreement (CRADA) was to explore and develop advanced manufacturing techniques to fabricate sintered iron-aluminide intermetallic porous bodies used for gas filtration so as to reduce production costs while maintaining or improving performance in advanced coal gasification and combustion systems. The use of a power turbine fired with coal-derived synthesis gas requires some form of gas cleaning in order to protect turbine and downstream components from degradation by erosion, corrosion, and/or deposition. Hot-gas filtration is one form of cleaning that offers the ability to remove particles from the gases produced by gasification processes without having to substantially cool and, possibly, reheat them before their introduction into the turbine. This technology depends critically on materials durability and reliability, which have been the subject of study for a number of years.

  3. Solidification behavior of FA-129 iron-aluminide alloy

    SciTech Connect

    Viswanathan, S.; Maziasz, P.J.; Sikka, V.K.

    1992-07-01

    Samples of FA-129 iron-aluminide alloy have been processed by various casting processes, including vacuum arc-melting followed by chill casting into water-cooled copper molds, air melting followed by casting into graphite molds, and electroslag melting and casting into large ingots. The resulting microstructures obtained in these processes are examined and compared. Selected samples are homogenized at various temperatures and times. Optical and transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) are used to identify the morphology, constituents, and compositions of various phases. Interrupted solidification experiments are used to study the evolution of cast structure. Some observations are made on the effect of dissolved hydrogen in the melt on as-cast soundness.

  4. Solidification behavior of FA-129 iron-aluminide alloy

    SciTech Connect

    Viswanathan, S.; Maziasz, P.J.; Sikka, V.K.

    1992-01-01

    Samples of FA-129 iron-aluminide alloy have been processed by various casting processes, including vacuum arc-melting followed by chill casting into water-cooled copper molds, air melting followed by casting into graphite molds, and electroslag melting and casting into large ingots. The resulting microstructures obtained in these processes are examined and compared. Selected samples are homogenized at various temperatures and times. Optical and transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) are used to identify the morphology, constituents, and compositions of various phases. Interrupted solidification experiments are used to study the evolution of cast structure. Some observations are made on the effect of dissolved hydrogen in the melt on as-cast soundness.

  5. Joining silicon nitride to FA-129 iron aluminide

    NASA Astrophysics Data System (ADS)

    Brochu, Mathieu

    Joints between dissimilar materials are characterized particularly by compositional gradients and microstructural changes, which yield large variations in chemical, physical and mechanical properties across the joint. The joining of dissimilar materials is therefore more complex than the joining of similar materials. In this project, the joining procedure, from the interaction between the different components in a joint to the determination of the mechanical properties was applied to the Si3N4/FA-129 system. This iron aluminide intermetallic alloy (FA-129), was developed by Oak Ridge National Laboratories (ORNL) to have high temperature properties with good room temperature ductility. This intermetallic is replacing high strength ferritic stainless steel (SS) in moderate strength applications due to cost and property reasons. Joints between SS and Si3N4 are already used industrially and this project was to evaluate the potential to replace these Si3N 4/SS joints by those of Si3N4/FA-129. Broadly stated, the results obtained during this project are as follows: (I) The E2 energy for Si3N4 ceramic was calculated to be 3.01 keV. (II) The wetting of iron aluminide alloy by copper has been achieved and the spreading and reaction kinetics are influenced by the presence of Cr as alloying element. (III) The penetration and decohesion of the FA-129 microstructure is significantly reduced by the utilization of a Cu alloy containing a high titanium concentration. (IV) An active brazing alloy containing a high active element content can be fabricated by an electroless deposition technique. (V) The melting behavior of the powder was characterized and complete melting occurs in a multi-step process at different temperatures, which are a function of the heating rate. (VI) The strength of joint produced by brazing Si3N4 to itself using the composite powder reached 400 MPa. (VII) Direct brazing of Si 3N4 to FA-129 was shown to be unsuccessful and therefore a soft Cu interlayer was

  6. Characterization of iron aluminides formed in situ in an aluminium matrix composite

    SciTech Connect

    Olszowka-Myalska, Anita . E-mail: anita.olszowka-myalska@polsl.pl; Szala, Janusz . E-mail: janusz.szala@polsl.pl; Cwajna, Jan . E-mail: jan.cwajna@polsl.pl

    2006-06-15

    The application of quantitative metallography to the description of in situ formation of reinforcement in composites is presented. The dispersion of iron aluminides, formed from iron powder in an aluminium matrix during hot pressing in vacuum, was analyzed on images from a scanning electron microscope. It was found that the dispersion of a new phase formed at a temperature of 630 deg. C depended on the initial composition mixture of metal powders and time of pressing. Iron aluminides were formed by two mechanisms: by a regular diffusional growth and by self-propagating high-temperature synthesis (SHS). In the case of the formation of particles by the SHS mechanism, two types of very fine iron aluminides were noticed. They differed in size and shape.

  7. The effects of zirconium and carbon on the hot cracking resistance of iron aluminides. Topical report

    SciTech Connect

    Mulac, B.L.; Edwards, G.R.; David, S.A.

    1998-02-01

    Iron aluminides have been of interest for about 60 years because of their good high temperature strengths (below 600{degrees}C) and excellent oxidation and sulfidation resistance, as well as their relatively low cost and conservation of strategic elements. These advantageous properties have driven the development of iron aluminides as potential structural materials. However, the industrial application of iron aluminides has been inhibited because of a sharp reduction in strength at temperatures higher than 600{degrees}C and low ductility at ambient temperatures due to hydrogen embrittlement. Oak Ridge National Laboratory has shown in recent years that room temperature properties of alloys containing 28% Al (all compositions are in atomic percent unless otherwise noted) can be improved through thermomechanical processing and alloying. Iron aluminides must have good weldability if they are to be used as structural materials. A coarse fusion zone microstructure is formed when iron aluminides are welded, increasing their susceptibility to cold cracking in water vapor. A recent study at Colorado School of Mines has shown that refining the fusion zone microstructure by weld pool oscillation effectively reduces cold cracking. Weld pool inoculation has been shown to refine fusion zone microstructures, but coarse carbide distribution caused this approach to reducing cold cracking to be ineffective.

  8. Evaluation of the fabricability of advanced iron aluminide-clad austenitic stainless steel tubing

    SciTech Connect

    Mohn, W.R.; Topolski, M.J.

    1993-07-01

    Researchers at Babcock & Wilcox Alliance Research Center have investigated methods to produce bimetallic tubing consisting of iron aluminide-clad austenitic stainless steel for practical use in fossil fueled energy equipment. In the course of this work, the compatibility of iron aluminide with four candidate austenitic stainless steel substrates was first evaluated using diffusion couples. Based on these results, a combination of iron aluminide and 304 stainless steel was selected for further development. Two composite billets of this combination were then prepared and extruded in separate trails at 2200F and 2000F. Both extrusions yielded 2-inch OD clad tubes, each approximately 18 feet long. Results of the evaluation show that the tube extruded at 2000F had a sound, integrally bonded clad layer throughout its entire length. However, the tube extruded at 2200F exhibited regions of disbonding between the clad layer and the substrate. In supplement to this work, an assessment of the technical and economic merits of iron aluminide-clad austenitic stainless steel components in power generation systems was conducted by B&W Fossil Power Division. Future activities should include an investigation of lower extrusion processing temperatures to optimize the fabrication of high quality iron-aluminide clad tubing.

  9. Corrosion performance of iron aluminides in single- and multioxidant environments.

    SciTech Connect

    Natesan, K.

    1998-06-22

    Iron aluminide intermetallics are being developed for use as structural materials and/or as cladding for conventional engineering alloys. In addition to their strength advantages, these materials exhibit excellent resistance to corrosion in single- and multioxidant environments at elevated temperatures through the formation of slow-growing, adherent alumina scales. Even though these intermetallics develop protective oxide scales in single-oxidant environments, the simultaneous presence of several reactants in the environment (typical of practical systems) can lead to development of oxide scales that are nonprotective and that undergo breakaway corrosion, or to nonoxide scales that are detrimental to the performance of the underlying alloy. This paper describes the corrosion performance of Fe-Al intermetallics in environments that contain sulfur, carbon, chlorine, and oxygen and that are typical of fossil energy systems. Emphasis is on mechanisms of scale development and breakdown, performance envelopes for long-term usage of these materials, and approaches to modifying the surfaces of engineering alloys by cladding or coating them with intermetallics to improve their corrosion resistance.

  10. Corrosion performance of iron aluminides in fossil energy environments

    SciTech Connect

    Natesan, K.

    1997-12-01

    Corrosion of metallic structural materials in complex gas environments of coal gasification and combustion is a potential problem. The corrosion process is dictated by concentrations of two key constituents: sulfur as H{sub 2}S or SO{sub 2} and chlorine as HCl. This paper presents a comprehensive review of the current status of the corrosion performance of alumina scales that are thermally grown on Fe-base alloys, including iron aluminides, in multicomponent gas environments of typical coal-conversion systems. Mechanisms of scale development/breakdown, performance envelopes for long-term usage of these materials, approaches to modifying the surfaces of engineering alloys by cladding or coating them with intermetallics, and in-service experience with these materials are emphasized. The results are compared with the performance of chromia-forming alloys in similar environments. The paper also discusses the available information on corrosion performance of alloys whose surfaces were enriched with Al by the electrospark deposition process or by weld overlay techniques.

  11. Influence of compositional modifications on the corrosion of iron aluminides of molten nitrate salts

    SciTech Connect

    Tortorelli, P.F.; Bishop, P.S.

    1991-01-01

    The corrosion of iron-aluminum alloys by molten nitrate salt as a function of aluminum, chromium, and other minor elements has been studied as part of an alloy design effort aimed at the development of a strong, ductile, corrosion-resistant FeAl type of aluminide. Short- term weight change data were used to examine the compositional dependence of the corrosion processes that occurred upon exposure of iron aluminides to highly oxidizing nitrate salts of 650{degrees}C. Corrosion resistance was found to increase with increasing aluminum concentrations of the alloy up to approximately 30 at. % Al. Chromium additions to the aluminide were not detrimental and may have improved the corrosion behavior for certain aluminum concentrations. No effects of minor alloying additions (C, B, Ti, and Zr) could be determined. The best overall corrosion resistance as measured by weight change results were obtained for an Fe-35.8 at. % Al aluminide containing some chromium. Based on linear weight loss kinetics, the weight change measurements for the most resistant compositions predict corrosion rates of 300 {mu}m/year or less at 650{degrees}C. These rates are substantially better than typical nickel-based alloys and stainless steels. From a consideration of the weight changes; the microstructural, thermodynamic, and X-ray diffraction data; and the salt analyses, corrosion of iron aluminides by the molten nitrate salt appears to be controlled by oxidation of base metal components and a slow release of material from an aluminum-rich product layer into the salt. The rate of release was substantially lower than that previously found for iron and iron-based alloys. This would imply that corrosion of iron aluminides could be minimized by maximizing the surface coverage of this aluminum-rich layer either by alloying or by an appropriate preoxidation treatment.

  12. Nickel aluminides and nickel-iron aluminides for use in oxidizing environments

    SciTech Connect

    Liu, C.T.

    1988-03-15

    A nickel aluminide is described consisting essentially of: a Ni/sub 3/Al base; a sufficient concentration of a Group IVB element or mixtures thereof to increase high temperature strength; a sufficient concentration of boron to increase ductility; and a sufficient concentration of chromium to increase ductility at elevated temperatures in oxidizing environments.

  13. Nickel aluminides and nickel-iron aluminides for use in oxidizing environments

    SciTech Connect

    Lui, C.T.

    1988-03-15

    This patent describes a nickel aluminide consisting essentially of: a Ni{sub 3}Al base; a sufficient concentration of a Group IVB element or mixtures thereof to increase high temperature strength; a sufficient concentration of boron to increase ductility; and a sufficient concentration of chromium to increase ductility at elevated temperatures in oxidizing environments.

  14. Metal matrix composite of an iron aluminide and ceramic particles and method thereof

    DOEpatents

    Schneibel, J.H.

    1997-06-10

    A metal matrix composite comprising an iron aluminide binder phase and a ceramic particulate phase such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide is made by heating a mixture of iron aluminide powder and particulates of one of the ceramics such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide in a alumina crucible at about 1,450 C for about 15 minutes in an evacuated furnace and cooling the mixture to room temperature. The ceramic particulates comprise greater than 40 volume percent to about 99 volume percent of the metal matrix composite.

  15. Metal matrix composite of an iron aluminide and ceramic particles and method thereof

    DOEpatents

    Schneibel, Joachim H.

    1997-01-01

    A metal matrix composite comprising an iron aluminide binder phase and a ceramic particulate phase such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide is made by heating a mixture of iron aluminide powder and particulates of one of the ceramics such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide in a alumina crucible at about 1450.degree. C. for about 15 minutes in an evacuated furnace and cooling the mixture to room temperature. The ceramic particulates comprise greater than 40 volume percent to about 99 volume percent of the metal matrix composite.

  16. Development of filler metals for welding of iron aluminide alloys. Final report

    SciTech Connect

    Goodwin, G.M.; Scott, J.L.

    1995-06-29

    Attempts were made to develop a coating formulation for shielded metal arc (SMA) welding electrodes for iron aluminide alloys. Core wires of various compositions were produced by aspiration casting at ORNL and coating formulation development was conducted by Devasco, Inc. It was found that, except for weld deposit compositions containing less than 10 weight % aluminum, all weld deposits exhibited extensive cold cracking and/or porosity. It was concluded that current coating formulation technology limits successful iron aluminide deposits to less than 10 weight % aluminum.

  17. Reaction synthesis and processing of nickel and iron aluminides

    SciTech Connect

    Deevi, S.C.; Sikka, V.K.

    1996-12-31

    Composites of Ni and Fe aluminides were obtained by hot pressing and hot extrusion of a blended mixture of Ni and Al or Fe and Al with ceramic phases such as TiC, ZrO{sub 2}, and Al{sub 2}O{sub 3}. Aluminides were analyzed by XRD to determine the phase structures, and optical and scanning electron microscopies were used to determine the grain sizes of the aluminides and dispersion of ceramics. Tensile properties (0.2% YS, UTS, total elong., RIA) were measured on buttonhead and sheet specimens of Ni and Fe aluminides and their composites at room and high temperatures in air at a strain rate of 1. 2x10{sup -3}/s. Tensile properties of Fe-8 wt% Al from partial mechanical alloying and then combustion synthesis compare very well with oxide-dispersed alloys of Fe. Fe aluminides of FeAl and their composites, based on Fe-24 wt% Al from hot pressing of Fe and Al powders with or without ceramic phases, exhibited full densities and uniform grain sizes. Tensile properties of FeAl and composites (hot pressing of elemental powders) were excellent compared to those of FeAl alloys from hot extrusion of water-atomized powders. Fe aluminides were also obtained by hot extrusion of Fe and Al powders at 950, 1000, and 1100 C.

  18. The thermographic nondestructive evaluation of iron aluminide green sheet

    NASA Astrophysics Data System (ADS)

    Watkins, Michael Lee

    The recent development of manufacturing techniques for the fabrication of thin iron aluminide sheet requires advanced quantitative methods for on-line inspection. An understanding of the mechanisms responsible for flaws and the development of appropriate flaw detection methods are key elements in an effective quality management system. The first step in the fabrication of thin FeAl alloy sheet is the formation of a green sheet by cold rolling FeAl powder mixed with organic binding agents. The green sheet composite has a bulk density, which is typically less than about 3.6 g/cc. The finished sheet, with a density of about 6.1 g/cc, is obtained using a series of process steps involving binder elimination, densification, sintering, and annealing. Non-uniformities within the green sheet are the major contributor to material failure in subsequent sheet processing and the production of non-conforming finished sheet. The production environment and physical characteristics of the composite provide for unique challenges in developing a rapid nondestructive inspection capability. The method must be non-contact due to the fragile nature of the composite. Limited access to the material also demands a one-sided inspection technique. An active thermographic method providing for 100% on-line inspection within an industrial, process has been developed. This approach is cost competitive with alternative technologies, such as x-ray imaging systems, and provides the required sensitivity to the variations in material composition. The mechanism of flaw formation and the transformation of green sheet flaws into defects that appear in intermediate and finished sheet products are described. A mathematical model which describes the green sheet heat transfer propagation, in the context of the inspection technique and the compact heterogeneity, is also presented. The potential for feedback within the production process is also discussed.

  19. Shape memory properties of an iron modified nickel aluminide alloy

    SciTech Connect

    Horton, J.A.; Liu, C.T.; George, E.P.

    1994-12-31

    The ordered intermetallic NiAl with aluminum levels near 36% undergoes a B2 to martensite transformation. Shape memory alloys based on NiAl + Fe have the potential for transition temperatures of greater than 150 C. While binary alloys appear inherently brittle, alloying with iron and boron results in two phase alloys with L1{sub 2} and B2 phases and with about 7% room temperature tensile ductility. These alloys show a two-way shape memory effect over a range of transition temperatures with austenite peak temperature, Ap, between 100 to 200 C based on composition. Unfortunately, the B2 phase and its low temperature body centered tetragonal martensitic form are not stable and both can transform to Ni{sub 5}Al{sub 3} with a loss in ductility. These alloys with a constant tensile load show a two way shape recovery of up to 0.6% during temperature cycling between 100 and 200 C. A thorough survey of the shape memory properties of one such alloy with a composition of Ni-25.5 Al-16 Fe-0.12 B (at.%) as a function of prior cold work, tensile loading and other training steps is presented. Nanoindentation was used to independently measure the mechanical properties of the two phases.

  20. Current status of research and development on nickel and iron aluminides

    SciTech Connect

    Liu, C.T.; George, E.P.; McKamey, C.G.

    1993-12-01

    This paper provides a comprehensive review of current status of research and development on nickel and iron aluminides based on Ni{sub 3}Al, NiAl, Fe{sub 3}Al and FeAl. These aluminides possess attractive properties for elevated-temperature structural use; however, brittle fracture and poor fracture resistance have limited their use as engineering materials in many cases. in recent years, considerable effort has been devoted to the study of the brittle fracture behavior of these aluminides; as a result, both intrinsic and extrinsic factors governing brittle fracture have been identified. Surprisingly, moisture-induced hydrogen embrittlement has been recognized as one of the major causes of low ductility and brittle fracture in Ni{sub 3}Al, Fe{sub 3}Al and FeAl at ambient temperatures. These efforts have led to the development of ductile and strong aluminide alloys for structural applications. Industrial interest in these aluminide alloys is high, and several examples of industrial involvement are mentioned.

  1. Method of manufacturing iron aluminide by thermomechanical processing of elemental powders

    SciTech Connect

    Deevi, S.C.; Lilly, A.C. Jr.; Sikka, V.K.; Hajaligol, M.R.

    2000-03-07

    A powder metallurgical process is dislosed for preparing iron aluminide useful as electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 20 to 32% Al, and optional additions such as {<=}1% Cr, {>=}05% Zr or ZrO{sub 2} stringers extending perpendicular to an exposed surface of the heating element, {<=}2% Ti, {<=}2% Mo, {<=}1% Zr, {<=}1% C, {<=}0.1% B, {<=}30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, {<=}1 % rare earth metal, {<=}1% oxygen, and/or {<=}3% Cu. The process includes forming a mixture of aluminum powder and iron powder, shaping the mixture into an article such as by cold rolling the mixture into a sheet, and sintering the article at a temperature sufficient to react the iron and aluminum powders and form iron aluminide. The sintering can be followed by hot or cold rolling to reduce porosity created during the sintering step and optional annealing steps in a vacuum or inert atmosphere.

  2. Method of manufacturing iron aluminide by thermomechanical processing of elemental powders

    DOEpatents

    Deevi, Seetharama C.; Lilly, Jr., A. Clifton; Sikka, Vinod K.; Hajaligol, Mohammed R.

    2000-01-01

    A powder metallurgical process of preparing iron aluminide useful as electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 20 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1 % rare earth metal, .ltoreq.1% oxygen, and/or .ltoreq.3% Cu. The process includes forming a mixture of aluminum powder and iron powder, shaping the mixture into an article such as by cold rolling the mixture into a sheet, and sintering the article at a temperature sufficient to react the iron and aluminum powders and form iron aluminide. The sintering can be followed by hot or cold rolling to reduce porosity created during the sintering step and optional annealing steps in a vacuum or inert atmosphere.

  3. Microstructural and mechanical property characterization of ingot metallurgy ODS iron aluminide

    SciTech Connect

    Sikka, V.K.; Howell, C.R.; Hall, F.; Valykeo, J.

    1997-12-01

    This paper deals with a novel, lower cost method of producing a oxide dispersion strengthened (ODS) iron-aluminide alloy. A large 250-kg batch of ODS iron-aluminide alloy designated as FAS was produced by Hoskins Manufacturing Company (Hoskins) [Hamburg, Michigan] using the new process. Plate and bar stock of the ODS alloy were the two major products received. Each of the products was characterized for its microstructure, including grain size and uniformity of oxide dispersion. Tensile tests were completed from room temperature to 1100 C. Only 100-h creep tests were completed at 800 and 1000 C. The results of these tests are compared with the commercial ODS alloy designated as MA-956. An assessment of these data is used to develop future plans for additional work and identifying applications.

  4. Corrosion resistant iron aluminides exhibiting improved mechanical properties and corrosion resistance

    DOEpatents

    Liu, Chain T.; McKamey, Claudette G.; Tortorelli, Peter F.; David, Stan A.

    1994-01-01

    The specification discloses a corrosion-resistant intermetallic alloy comprising, in atomic percent, an FeAl iron aluminide containing from about 30 to about 40% aluminum alloyed with from about 0.01 to 0.4% zirconium and from 0.01 to about 0.8% boron. The alloy exhibits considerably improved room temperature ductility for enhanced usefulness in structural applications. The high temperature strength and fabricability is improved by alloying with molybdenum, carbon, chromium and vanadium.

  5. Corrosion resistant iron aluminides exhibiting improved mechanical properties and corrosion resistance

    DOEpatents

    Liu, C.T.; McKamey, C.G.; Tortorelli, P.F.; David, S.A.

    1994-06-14

    The specification discloses a corrosion-resistant intermetallic alloy comprising, in atomic percent, an FeAl iron aluminide containing from about 30 to about 40% aluminum alloyed with from about 0.01 to 0.4% zirconium and from 0.01 to about 0.8% boron. The alloy exhibits considerably improved room temperature ductility for enhanced usefulness in structural applications. The high temperature strength and fabricability is improved by alloying with molybdenum, carbon, chromium and vanadium. 9 figs.

  6. Erosion studies on a Fe sub 3 Al-based iron aluminide and 1100 Al

    SciTech Connect

    Rao, M.; Keiser, J.

    1991-01-01

    Samples of a Fe{sub 3}Al-based iron aluminide alloy were eroded using nominally spherical steel shot. Two distinct erosion mechanisms were observed: (1) extrusion of platelets resulting from spherical particle impacts and (2) cutting of the target by angular particles either present in the initial erodent or formed on impact by fracture of the shot. The overall erosion resistance of the alloy was judged to be relatively good and may be improved by increasing the alloy's ductility. Measurements using a mechanical properties microprobe (MPM) showed that significant work hardening occurred due to erosion, but the hardness dropped off near the surface, apparently due to thermal effects. In contrast no sub-surface softening was observed in samples of 1100 Al which were also eroded by steel shot. In order to model the impact process, single 343 {mu}m WC spheres were shot at the two alloys at velocities between 20 m/s and 900 m/s. Compared to the iron aluminide, the craters on 1100 Al show better developed lips and features indicative of sustained plastic deformation. Both alloys showed thermally induced subsurface softening at high velocities. At lower velocities, only the iron aluminide showed clear thermal effects. Results of the single particle and multiple particle impact tests are reconciled in terms of deformation behavior and thermal effects. 22 refs., 7 figs.

  7. Fabrication and mechanical properties of Fe sub 3 Al-based iron aluminides

    SciTech Connect

    Sikka, V.K.; McKamey, C.G.; Howell, C.R.; Baldwin, R.H.

    1990-03-01

    Iron aluminides based on Fe{sub 3}Al are ordered intermetallic alloys that offer good oxidation resistance, excellent sulfidation resistance, and lower material cost than many stainless steels. These materials also conserve strategic elements such as chromium and have a lower density than stainless steels. However, limited ductility at ambient temperature and a sharp drop in strength have been major deterrents to their acceptance for structural applications. This report presents results on iron aluminides with room-temperature elongations of 15 to 20%. Ductility values were improved by a combination of thermomechanical processing and heat-treatment control. This method of ductility improvement has been demonstrated for a range of compositions. Melting, casting, and processing of 7-kg (15-lb) heats produced at the Oak Ridge National Laboratory (ORNL) and 70-kg (150-lb) commercial heats are described. Vacuum melting and other refining processes such as electroslag remelting are recommended for commercial heats. The Fe{sub 3}Al-based iron aluminides are hot workable by forging or extruding at temperatures in the range of 850 to 1100{degree}C. rolling at 800{degree}C is recommended with a final 50% reduction at 650{degree}C. Tensile and creep properties of 7- and 70-kg (15- and 150-lb) heats are presented. The presence of impurities such as manganese an silicon played an important role in reducing the ductility of commercially melted heats. 7 refs., 60 figs., 12 tabs.

  8. Evaluation of the intrinsic and extrinsic fracture behavior of iron aluminides

    SciTech Connect

    Kang, B.S.; Yao, Qizhou; Cooper, B.R.

    1996-08-01

    Comparative creep crack growth tests of FA-186 and FA-187 iron aluminides under either dry oxygen or air environment showed that both alloys are susceptible to room temperature hydrogen embrittlement. Test results also revealed that FA-187 is intrinsically a more brittle material than FA-186. Atomistic computational modeling is being undertaken to find the preferred geometries, structures and formation energies of iron vacancies and vacancy pairs (Fe-Fe) in FeAl and Fe{sub 3}Al. An indication of vacancy clustering in Fe{sub 3}Al, with consequences for dislocation behavior, may be important for understanding the role of dislocation assisted diffusion in the hydrogen embrittlement mechanism.

  9. Evaluation of the intrinsic and extrinsic fracture behavior of iron aluminides

    SciTech Connect

    Cooper, B.R.; Kang, B.S.

    1998-07-27

    Iron aluminides have excellent corrosion resistance in high-temperature oxidizing-sulfidizing environments; however, there are problems at room and medium temperatures with hydrogen embrittlement as related to exposure to moisture. In this research, a coordinated computational modeling/experimental study of mechanisms related to environmental-assisted fracture behavior of selected iron aluminides has been undertaken. The modeling and the experimental work connect at the level of coordinated understanding of the mechanisms for hydrogen penetration and for loss of strength and susceptibility to fracture. The focus of the modeling component has been on the challenging question of accurately predicting the iron vacancy formation energy in Fe{sub 3}Al and the subsequent tendency, if present, for vacancy clustering. The authors have successfully performed, on an ab initio basis, the first calculation of the vacancy formation energy in Fe{sub 3}Al. These calculations include lattice relaxation effects which are quite large for one of the two types of iron sites. This has significant implications for vacancy clustering effects with consequences for hydrogen diffusion. Indeed, the ab-initio-based estimate of the divacancy binding energy indicates a likely tendency toward such clustering for iron vacancies on the sites with large lattice relaxation. The experimental work has focused on the relationship of the choice and concentration of additives to the improvement of resistance to hydrogen embrittlement and hence to the fracture behavior.

  10. Iron aluminide-titanium carbide composites: Microstructure and mechanical properties

    SciTech Connect

    Subramanian, R.; Schneibel, J.H.; Alexander, K.B.

    1996-09-01

    Composites of intermetallics and carbides (with binder contents less that 50 vol.%) are considered as potential candidates for applications requiring high wear resistance in corrosive environments. Intermetallics, especially aluminides, provide the corrosion resistance, and the high hardness of the carbide phase contributes to increased wear resistance of the composites. In this study, cost effective and simple processing techniques to obtain FeAl-TiC composites, over a wide range of binder volume fractions, are demonstrated. Binder volume fractions range from 0.15 to 0.7 (18 to 75 wt. % binder). Two techniques - liquid phase sintering of mixed powders and pressureless melt infiltration of TiC preforms was found to be very successful for obtaining fully dense composites with binder volume fractions from 0.15 to 0.3 (18 to 34 wt. %), whereas for higher binder contents liquid phase sintering of mixed powders was the best approach. Mechanical properties of these composites including the 3-point bend strength, fracture toughness and hardness are presented.

  11. Influence of strain rate and temperature on the mechanical behavior of iron aluminide-based alloys

    SciTech Connect

    Gray, G.T.

    1995-04-01

    Iron aluminides are receiving increasing attention as potential high temperature structural materials due to their excellent oxidation and sulfidation resistance. Although the influence of strain rate on the microstructure/property relationships of pure iron and a variety of iron alloys and steels has been extensively studied, the effect of strain rate on the stress-strain and deformation response of iron aluminides remains poorly understood. In this paper the influence of strain rate, varied between 0.001 and 10{sup 4} s{sup {minus}1}, and temperature, between 77 & 1073{degree}K, on the mechanical behavior of Fe-40Al-0.1B and Fe-16.12Al-5.44Cr-0.11Zr-0.13C-1.07Mo-006Y, called FAP-Y, (both in at.%) is presented. The rate sensitivity and work hardening of Fe-40Al and the disordered alloy based on Fe-16% Al are discussed as a function of strain rate and temperature.

  12. Environmental embrittlement of iron aluminides under cyclic loading conditions

    SciTech Connect

    Castagna, A.; Alven, D.A.; Stoloff, N.S.

    1995-08-01

    The tensile and fatigue crack growth behavior in air in hydrogen and in oxygen of an Fe-Al-Cr-Zr alloy is described. The results are compared to data for FA-129. A detailed analysis of frequency effects on fatigue crack growth rates of FA-129, tested in the B2 condition, shows that dislocation transport of hydrogen from the surface is the rate limiting step in fatigue crack growth.

  13. Oxidation, carburization and/or sulfidation resistant iron aluminide alloy

    DOEpatents

    Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

    2003-08-19

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or Zro.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B. .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

  14. Iron aluminide useful as electrical resistance heating elements

    SciTech Connect

    Sikka, V.K.; Deevi, S.C.; Fleischhauer, G.S.; Hajaligol, M.R.; Lilly, A.C. Jr.

    1999-11-02

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, {le}1% Cr and either {ge}0.05% Zr or ZrO{sub 2} stringers extending perpendicular to an exposed surface of the heating element or {ge}0.1% oxide dispersoid particles. The alloy can contain 14--32% Al, {le}2% Ti, {le}2% Mo, {le}1% Zr, {le}1% C, {le}0.1% B, {le}30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, {le}1% rare earth metal, {le}1% oxygen, {le}3% Cu, balance Fe.

  15. Iron aluminide useful as electrical resistance heating elements

    DOEpatents

    Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

    2001-01-01

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

  16. Iron aluminide useful as electrical resistance heating elements

    DOEpatents

    Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

    1997-01-01

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

  17. Iron aluminide useful as electrical resistance heating elements

    DOEpatents

    Sikka, V.K.; Deevi, S.C.; Fleischhauer, G.S.; Hajaligol, M.R.; Lilly, A.C. Jr.

    1997-04-15

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, {<=}1% Cr and either {>=}0.05% Zr or ZrO{sub 2} stringers extending perpendicular to an exposed surface of the heating element or {>=}0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, {<=}2% Ti, {<=}2% Mo, {<=}1% Zr, {<=}1% C, {<=}0.1% B, {<=}30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, {<=}1% rare earth metal, {<=}1% oxygen, {<=}3% Cu, balance Fe. 64 figs.

  18. Iron aluminide useful as electrical resistance heating elements

    DOEpatents

    Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

    1999-01-01

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

  19. Single-step gas phase synthesis of stable iron aluminide nanoparticles with soft magnetic properties

    SciTech Connect

    Vernieres, Jerome Benelmekki, Maria; Kim, Jeong-Hwan; Grammatikopoulos, Panagiotis; Diaz, Rosa E.; Bobo, Jean-François; Sowwan, Mukhles

    2014-11-01

    Soft magnetic alloys at the nanoscale level have long generated a vivid interest as candidate materials for technological and biomedical purposes. Consequently, controlling the structure of bimetallic nanoparticles in order to optimize their magnetic properties, such as high magnetization and low coercivity, can significantly boost their potential for related applications. However, traditional synthesis methods stumble upon the long standing challenge of developing true nanoalloys with effective control over morphology and stability against oxidation. Herein, we report on a single-step approach to the gas phase synthesis of soft magnetic bimetallic iron aluminide nanoparticles, using a versatile co-sputter inert gas condensation technique. This method allowed for precise morphological control of the particles; they consisted of an alloy iron aluminide crystalline core (DO{sub 3} phase) and an alumina shell, which reduced inter-particle interactions and also prevented further oxidation and segregation of the bimetallic core. Remarkably, the as-deposited alloy nanoparticles show interesting soft magnetic properties, in that they combine a high saturation magnetization (170 emu/g) and low coercivity (less than 20 Oe) at room temperature. Additional functionality is tenable by modifying the surface of the particles with a polymer, to ensure their good colloidal dispersion in aqueous environments.

  20. High-temperature oxidation/sulfidation resistance of iron-aluminide coatings

    SciTech Connect

    Tortorelli, P.F.; Wright, I.G.; Goodwin, G.M.; Howell, M.

    1996-04-01

    Iron aluminides containing > 20-25 at. % Al have oxidation and sulfidation resistance at temperatures well above those at which these alloys have adequate mechanical strength. Accordingly, these alloys may find application as coatings or claddings on more conventional higher-strength materials which are generally less corrosion-resistant at high temperatures. To this end, iron-aluminide coatings were prepared by gas tungsten arc and gas metal arc weld-overlay techniques. Specimens were cut from weld deposits and exposed to a highly aggressive oxidizing-sulfidizing (H2S-H2-H2O-Ar) environment at 800 C. All the weld overlayers showed good corrosion behavior under isothermal conditions, including a gas metal arc-produced deposit with only 21 at. % Al. Rapid degradation in corrosion resistance was observed under thermal cycling conditions when the initally grown scales spalled and the rate of reaction was then not controlled by formation of slowly growing Al oxide. Higher starting Al concentrations (> {approximately} 25 at. %) are needed to assure overall oxidation-sulfidation resistance of the weld overlays, but hydrogen cracking susceptibility must be minimized in order to physically separate the corrosive species from the reactive substrate material.

  1. Evaluation of Iron Aluminide Weld Overlays for Erosion-Corrosion Resistant Boiler Tube Coatings in Low NOx Boilers

    SciTech Connect

    Regina, J.R.; Lim, M.; Barbosa, N., DuPont, J.N.; Marder, A.R.

    2000-04-28

    Iron aluminide weld overlays containing ternary additions and thermal spray coatings are being investigated for corrosion protection of boiler tubes in Low NO{sub x} burners. The primary objective of the research is to identify overlay and thermal spray compositions that provide corrosion protection of waterwall boiler tubes.

  2. High-temperature corrosion-resistant iron-aluminide (FeAl) alloys exhibiting improved weldability

    DOEpatents

    Maziasz, P.J.; Goodwin, G.M.; Liu, C.T.

    1996-08-13

    This invention relates to improved corrosion-resistant iron-aluminide intermetallic alloys. The alloys of this invention comprise, in atomic percent, from about 30% to about 40% aluminum alloyed with from about 0.1% to about 0.5% carbon, no more than about 0.04% boron such that the atomic weight ratio of boron to carbon in the alloy is in the range of from about 0.01:1 to about 0.08:1, from about 0.01 to about 3.5% of one or more transition metals selected from Group IVB, VB, and VIB elements and the balance iron wherein the alloy exhibits improved resistance to hot cracking during welding. 13 figs.

  3. High-temperature corrosion-resistant iron-aluminide (FeAl) alloys exhibiting improved weldability

    DOEpatents

    Maziasz, Philip J.; Goodwin, Gene M.; Liu, Chain T.

    1996-01-01

    This invention relates to improved corrosion-resistant iron-aluminide intermetallic alloys. The alloys of this invention comprise, in atomic percent, from about 30% to about 40% aluminum alloyed with from about 0.1% to about 0.5% carbon, no more than about 0.04% boron such that the atomic weight ratio of boron to carbon in the alloy is in the range of from about 0.01:1 to about 0.08:1, from about 0.01 to about 3.5% of one or more transition metals selected from Group IVB, VB, and VIB elements and the balance iron wherein the alloy exhibits improved resistance to hot cracking during welding.

  4. Preferred orientations in extruded nickel and iron aluminides

    NASA Astrophysics Data System (ADS)

    Khadkikar, P. S.; Michal, G. M.; Vedula, K.

    1990-01-01

    Preferred orientations in both powder-extruded and cast and extruded binary NiAl (≃45 at. pet Al), FeAl (≃40 at. pet Al), and Ni3Al (≃24 at. pet Al) have been characterized by plotting inverse pole figures. The preferred orientation, [111], was observed along the extrusion direction in both powder-extruded and cast and extruded NiAl. Powder-extruded FeAl also exhibited [111] as the preferred orientation in the as-extruded condition. However, [110] was observed to be the preferred orientation in the cast and extruded FeAl and was replaced by a [211] orientation preference upon annealing. Annealing did not change the preferred orientations in NiAl or in powder-extruded FeAl. In contrast to the B2 NiAl and FeAl alloys, the Ll2 Ni3Al alloy exhibited nearly random orientations with only a minor preference for a [111] orientation in the as-extruded condition.

  5. Synthesis of iron aluminide-Al{sub 2}O{sub 3} composites by in-situ displacement reactions

    SciTech Connect

    Subramanian, R.; McKamey, C.G.; Buck, L.R.; Schneibel, J.H.

    1997-09-01

    Composites consisting of an iron aluminide matrix with ceramic particle reinforcements, such as alumina, could improve the high temperature strength without compromising the oxidation resistance. In this paper, the feasibility of processing Fe-Al alloy/Al{sub 2}O{sub 3} composites by an in-situ displacement reaction between Fe-40 at.% Al and iron oxide, Fe{sub 2}O{sub 3}, is investigated. Simple powder metallurgical processing was performed without resorting to an externally applied pressures or deformations during the high temperature processing step. The microstructural features of the composites are rationalized based on results from diffusion couples. Preliminary mechanical properties such as fracture toughness, yield strength and hardness are determined and compared with the values obtained for monolithic iron aluminide - Fe-28 at.% Al. Results suggest that a significant improvement in the properties is needed and further avenues for modifications, such as changes in the interface strength and externally applied forces during processing, are suggested.

  6. Surface Gasification Materials Program: Semiannual progress report for the period ending September 30, 1986. [Iron aluminide

    SciTech Connect

    Not Available

    1987-01-01

    The objective of the Surface Gasification Materials Program is to conduct research and development on materials for application to the specific needs of coal gasification systems. One of the goals of the program is to evaluate innovative fabrication methods which have the potential to lower costs and improve reliability and safety for gasifier vessels and components. Another goal is to conduct engineering-scale development and application of materials for coal gasification systems to ensure that the materials of construction for pilot plants and future large-scale plants can be properly selected and specified. This semiannual progress report covers: (1) protective coatings and claddings - application/evaluation; (2) electroslag component casting; (3) materials development for solid oxide oxygen production unit; and (4) development of iron aluminides.

  7. Effects of surface condition on aqueous corrosion and environmental embrittlement of iron aluminides

    SciTech Connect

    Perrin, R.L.; Buchanan, R.A.

    1996-08-01

    Effects of retained high-temperature surface oxides, produced during thermomechanical processing and/or heat treatment, on the aqueous-corrosion and environmental-embrittlement characteristics of Fe{sub 3}Al-based iron aluminides (FA-84, FA-129 and FAL-Mo), a FeAl-based iron aluminide (FA-385), and a disordered low-aluminum Fe-Al alloy (FAPY) were evaluated. All tests were conducted at room temperature in a mild acid-chloride solution. In cyclic-anodic-polarization testing for aqueous-corrosion behavior, the surface conditions examined were: as-received (i.e., with the retained high-temperature oxides), mechanically cleaned and chemically cleaned. For all materials, the polarization tests showed the critical pitting potentials to be significantly lower in the as-received condition than in the mechanically-cleaned and chemically-cleaned conditions. These results indicate detrimental effects of the retained high-temperature oxides in terms of increased susceptibilities to localized corrosion. In 200-hour U-bend stress-corrosion-cracking tests for environmental-embrittlement behavior, conducted at open-circuit corrosion potentials and at a hydrogen-charging potential of {minus}1500 mV (SHE), the above materials (except FA-385) were examined with retained oxides and with mechanically cleaned surfaces. At the open-circuit corrosion potentials, none of the materials in either surface condition underwent cracking. At the hydrogen-charging potential, none of the materials with retained oxides underwent cracking, but FA-84, FA-129 and FAL-Mo in the mechanically cleaned condition did undergo cracking. These results suggest beneficial effects of the retained high-temperature oxides in terms of increased resistance to environmental hydrogen embrittlement.

  8. Evaluation of the Intrinsic and Extrinsic Fracture Behavior of Iron Aluminides

    SciTech Connect

    Cooper, B.R.

    2001-01-11

    In this paper, we first present the status of our computational modeling study of the thermal expansion coefficient of Fe/Al over a wide range of temperature and evaluate its dependence on selected additives. This will be accomplished by applying an isobaric Monte Carlo technique. The required total energy of the sample will be computed by using a tight-binding (TB) method that allows us to significantly increase the size of the computational data base without reducing the accuracy of the calculations. The parameters of the TB Hamiltonian are fitted to reproduce the band structure obtained by our quantum mechanical full-potential LMTO calculations. The combination of the three methods mentioned above creates an effective approach to the computation of the physical properties of the transition-metal aluminides and it can be extended to alloys with more than two components. At present, we are using a simplified approach for a first-round of results; and as a test of the simplified approach, have obtained excellent agreement with experiment for aluminum. Our previous experimental results showed that, because of their smaller grain size, FA-187 and FA-189 are extrinsically more susceptible to environmental embrittlement than FA-186 under low strain loading condition. To further investigate the grain boundary size effect as related to the susceptibility of hydrogen embrittlement, we conducted comparative finite element modeling simulations of initial intergranular fracture of two iron aluminides (FA186 and FA189) due to hydrogen embrittlement. Sequentially coupled stress and mass diffusion analyses are carried out to determine crack-tip stress state and the extent of hydrogen diffusion at the crack tip region, and a proper failure criteria is then adopted to simulate the intergranular fracture. Good qualitative agreement between the modeling predictions and experimental results is observed.

  9. Effects of high temperature surface oxides on room temperature aqueous corrosion and environmental embrittlement of iron aluminides

    SciTech Connect

    Buchanan, R.A.; Perrin, R.L.

    1996-09-01

    Studies were conducted to determine the effects of high-temperature surface oxides, produced during thermomechanical processing, heat treatment (750 {degrees}C in air, one hour) or simulated in-service-type oxidation (1000{degrees}C in air, 24 hours) on the room-temperature aqueous-corrosion and environmental-embrittlement characteristics of iron aluminides. Materials evaluated included the Fe{sub 3}Al-based iron aluminides, FA-84, FA-129, FAL and FAL-Mo, a FeAl-based iron aluminide, FA-385, and a disordered low-aluminum Fe-Al alloy, FAPY. Tests were performed in a mild acid-chloride solution to simulate aggressive atmospheric corrosion. Cyclic-anodic-polarization tests were employed to evaluate resistances to localized aqueous corrosion. The high-temperature oxide surfaces consistently produced detrimental results relative to mechanically or chemically cleaned surfaces. Specifically, the pitting corrosion resistances were much lower for the as-processed and 750{degrees} C surfaces, relative to the cleaned surfaces, for FA-84, FA-129, FAL-Mo, FA-385 and FAPY. Furthermore, the pitting corrosion resistances were much lower for the 1000{degrees}C surfaces, relative to cleaned surfaces, for FA-129, FAL and FAL-Mo.

  10. Aqueous corrosion characteristics and corrosion-related cracking susceptibilities of Fe sub 3 Al-type iron aluminides

    SciTech Connect

    Buchanan, R.A.; Kim, J.G. . Dept. of Materials Science and Engineering)

    1991-04-01

    In certain fossil-energy applications, iron aluminides may be subjected to ambient-temperature aqueous corrosion conditions. In the present project, the aqueous corrosion characteristics and the cracking tendencies under aqueous-corrosion conditions were studied. In these studies, electrochemical, immersion and electrochemical-mechanical evaluation techniques were employed. For a range of iron-aluminide compositions, cyclic anodic polarization tests were conducted in a number of electrolytes to provide information on anodic dissolution characteristics including tendencies for either active uniform corrosion, localized corrosion, or passivation. Average corrosion penetration rates were determined by application of Tafel methods or the polarization-resistance method in combination with Faraday's law. Immersion test methods were employed to verify corrosion behavior as determined by electrochemical methods and to evaluate localized-corrosion initiation times. U-bend corrosion tests were conducted at open-circuit corrosion potentials and at potentiostatically-controlled anodic and cathodic potentials to investigate the cracking tendencies of selected iron aluminides and to provide information on the cracking mechanism. And finally, slow-strain-rate corrosion tests were conducted at open-circuit and potentiostatically-controlled cathodic potentials to study the ductility response as related to cracking tendencies and the mechanism responsible. 32 refs., 19 figs., 11 tabs.

  11. The influence of processing on microstructure and properties of iron aluminides

    SciTech Connect

    Wright, R.N.; Wright, J.K.; Anderson, M.T.

    1997-12-01

    Oxide dispersion strengthened (ODS) iron aluminide alloys based on Fe3Al have been formed by reaction synthesis from elemental powders followed by hot extrusion. The resulting alloys have approximately 2.5% by volume Al{sub 2}O{sub 3} particles dispersed throughout the material. A proper combination of extrusion temperature, extrusion ratio, and post-consolidation heat treatment results in a secondary recrystallized microstructure with grain sizes greater than 25mm. ODS material with 5% Cr addition exhibits approximately an order of magnitude increase in time to failure at 650 C compared to a similar alloy without the oxide dispersion. Addition of Nb and Mo along with Cr results in decreased minimum creep rates, however, the time to rupture is greatly reduced due to fracture at low strains initiated at large Nb particles that were not put into solution. The activation energy for creep in the 5% Cr ODS material is on the order of 210 kJ/mole and the power law creep exponent is 9--9.5. Transmission electron microscopy examination of the substructure of deformed samples indicates some formation of low angle dislocation boundaries, however, most of the dislocations are pinned at particles. The TEM observations and the value of the creep exponent are indicative of dislocation breakaway from particles as the rate controlling deformation mechanism. The TEM results indicate that particles smaller than about 100nm and larger than about 500 nm do not contribute significantly to dislocation pinning.

  12. Production of iron aluminides by strip casting followed by cold rolling at room temperature

    SciTech Connect

    Blackford, J.R.; Buckley, R.A.; Jones, H.; Sellars, C.M.

    1996-05-15

    The high resistance of iron aluminides to sulfidizing and oxidizing environments at high temperatures offers potential for structural application as lower cost alternatives to 300 and 400 series stainless steels and some nickel-base alloys. They are, however, subject to ductility limitations at room temperature which compel careful processing in order to achieve optimum properties in the final product. The standard melt-processing route of casting to ingot followed by hot and warm working to bar, plate or sheet is critically dependent on, for example, control of grain size in the initial cast structure, and the low ductility of the ingot structure at room temperature rules out cold working as a possibility at that stage. The purpose of this contribution is to report results of initial trials involving strip casting from the melt followed directly by cold-rolling and heat treatment. A previous communication reported results of an alternative novel route, that of co-rolling of elemental foils followed by heat treatment.

  13. Environment-assisted cracking of iron aluminide in 3.5% NaCl solution

    SciTech Connect

    Chiu, H.; Qiao, L.; Mao, X.

    1996-03-15

    In 3.5% NaCl solution, the environment-assisted cracking behavior of an iron aluminide alloy was studied. Slow strain rate tests were done at different electrochemical potentials. A 55% loss in ductility was found when tested at anodic potentials, which suggests a material degradation by the aqueous environment. Results of the experiments that were carried out using pre-immersed specimens and notched tensile specimens confirmed this material degradation to be stress corrosion cracking (SCC). To identify the mechanism, an electrochemical permeation technique was employed. By measuring the diffusible hydrogen concentration, sensitivity to hydrogen embrittlement has been assessed at different potentials. Fracture surfaces were examined under the scanning electron microscope (SEM). Fracture mode was found to be mainly transgranular quasi-cleavage, except the ones tested at anodic potentials (that are 0 mV and {minus}100 mV vs SCE) on which intergranular SCC was found near the edge. It is believed that these cracks were initiated from the pits. These results indicate that the environment-assisted cracking is an intergranular SCC, controlled by anodic dissolution mechanism.

  14. Interdiffusion behaviors of iron aluminide coatings on China low activation martensitic steel

    NASA Astrophysics Data System (ADS)

    Zhu, X. X.; Yang, H. G.; Yuan, X. M.; Zhao, W. W.; Zhan, Q.

    2014-12-01

    The iron aluminide coating on China Low Activation Martensitic (CLAM) steel was prepared by pack cementation and subsequent heat treatment. A surface Fe2Al5 layer was formed on CLAM substrate by pack cementation process with Fe2Al5 donor powder and NH4Cl activator. Diffusion heat treatment was performed in order to allow the phase transformation from Fe2Al5 to a phase with lower aluminum content. Morphology and composition of the coatings were characterized by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), glow discharge optical emission spectroscopy (GDOES) and X-ray diffraction (XRD). There is a need to study the interdiffusion behaviors in these Al containing systems, as a basis for controlling the formation and subsequent degradation of the coating. In this paper, a predictive model was developed to describe the phase transformation of Fe2Al5 as a function of processing parameters. The Wagner's equation was used to calculate the interdiffusion coefficients based on the analysis of the Al concentration profiles. The results showed that the interdiffusion coefficients in the FeAl and α-Fe(Al) phase strongly depends on Al content and showed a maximum at about 28 at.% Al.

  15. Iron aluminide weld overlay coatings for boiler tube protection in coal-fired low NOx boilers

    SciTech Connect

    Banovic, S.W.; DuPont, J.N.; Marder, A.R.

    1997-12-01

    Iron aluminide weld overlay coatings are currently being considered for enhanced sulfidation resistance in coal-fired low NO{sub x} boilers. The use of these materials is currently limited due to hydrogen cracking susceptibility, which generally increases with an increase in aluminum concentration of the deposit. The overall objective of this program is to attain an optimum aluminum content with good weldability and improved sulfidation resistance with respect to conventional materials presently in use. Research has been initiated using Gas Tungsten Arc Welding (GTAW) in order to achieve this end. Under different sets of GTAW parameters (wire feed speed, current), both single and multiple pass overlays were produced. Characterization of all weldments was conducted using light optical microscopy, scanning electron microscopy, and electron probe microanalysis. Resultant deposits exhibited a wide range of aluminum contents (5--43 wt%). It was found that the GTAW overlays with aluminum contents above {approximately}10 wt% resulted in cracked coatings. Preliminary corrosion experiments of 5 to 10 wt% Al cast alloys in relatively simple H{sub 2}/H{sub 2}S gas mixtures exhibited corrosion rates lower than 304 stainless steel.

  16. Investigation of moisture-induced embrittlement of iron aluminides. Final report

    SciTech Connect

    Alven, D.A.; Stoloff, N.S.

    1997-06-05

    Iron-aluminum alloys with 28 at.% Al and 5 at.% Cr were shown to be susceptible to hydrogen embrittlement by exposure to both gaseous hydrogen and water vapor. This study examined the effect of the addition of zirconium and carbon on the moisture-induced hydrogen embrittlement of an Fe{sub 3}Al,Cr alloy through the evaluation of tensile properties and fatigue crack growth resistance in hydrogen gas and moisture-bearing air. Susceptibility to embrittlement was found to vary with the zirconium content while the carbon addition was found to only affect the fracture toughness. Inherent fatigue crack growth resistance and fracture toughness, as measured in an inert environment, was found to increase with the addition of 0.5 at.% Zr. The combined addition of 0.5 at.% Zr and carbon only increased the fracture toughness. The addition of 1 at.% Zr and carbon was found to have no effect on the crack growth rate when compared to the base alloy. Susceptibility to embrittlement in moisture-bearing environments was found to decrease with the addition of 0.5 at.% Zr. In gaseous hydrogen, the threshold value of the Zr-containing alloys was found to increase above that found in the inert environment while the crack growth resistance was much lower. By varying the frequency of fatigue loading, it was shown that the corrosion fatigue component of the fatigue crack growth rate in an embrittling environment displays a frequency dependence. Hydrogen transport in iron aluminides was shown to occur primarily by a dislocation-assisted transport mechanism. This mechanism, in conjunction with fractography, indicates that the zirconium-containing precipitates act as traps for the hydrogen that is carried along by the dislocations through the lattice.

  17. The effect of solidification rate on the formability of nickel aluminide containing iron and boron

    NASA Technical Reports Server (NTRS)

    Carro, G.; Flanagan, W. F.

    1987-01-01

    Following reports that rapid solidification improves the ductility of some nickel aluminides, an investigation has been conducted of the possibility of additional improvement in a nickel aluminide containing both Fe and B. Free fall-solidified and free fall/splat-quenched samples similar to those producible under microgravity conditions in space were prepared, and their microstructure was characterized. Attention is given to the preliminary results of tests quantitatively measuring mechanical properties.

  18. Evaluation of iron aluminide weld overlays for erosion - corrosion resistant boiler tube coatings in low NO{sub x} boilers

    SciTech Connect

    DuPont, J.N.; Banovic, S.W.; Marder, A.R.

    1996-08-01

    Low NOx burners are being installed in many fossil fired power plants in order to comply with new Clean Air Regulations. Due to the operating characteristics of these burners, boiler tube sulfidation corrosion is often enhanced and premature tube failures can occur. Failures due to oxidation and solid particle erosion are also a concern. A program was initiated in early 1996 to evaluate the use of iron aluminide weld overlays for erosion/corrosion protection of boiler tubes in Low NOx boilers. Composite iron/aluminum wires will be used with the Gas Metal Arc Welding (GMAW) process to prepare overlays on boiler tubes steels with aluminum contents from 8 to 16wt%. The weldability of the composite wires will be evaluated as a function of chemical composition and welding parameters. The effect of overlay composition on corrosion (oxidation and sulfidation) and solid particle erosion will also be evaluated. The laboratory studies will be complemented by field exposures of both iron aluminide weld overlays and co-extruded tubing under actual boiler conditions.

  19. The quantitative inspection of iron aluminide green sheet using transient thermography

    NASA Astrophysics Data System (ADS)

    Watkins, Michael L.; Hinders, Mark K.; Scorey, Clive; Winfree, William

    1999-12-01

    The recent development of manufacturing techniques for the fabrication of thin iron aluminide, FeAl, sheet requires advanced quantitative methods for on-line inspection. An understanding of the mechanisms responsible for flaws and the development of appropriate flaw detection methods are key elements in an effective quality management system. The first step in the fabrication of thin FeAl alloy sheet is the formation of a green sheet, either by cold rolling or tape casting FeAl powder mixed with organic binding agents. The finished sheet is obtained using a series of process steps involving binder elimination, densification, sintering, and annealing. Non-uniformities within the green sheet are the major contributor to material failure in subsequent sheet processing and the production of non-conforming finished sheet. Previous work has demonstrated the advantages of using active thermography to detect the flaws and heterogeneity within green powder composites (1)(2)(3). The production environment and physical characteristics of these composites provide for unique challenges in developing a rapid nondestructive inspection capability. Thermography is non-contact and minimizes the potential damage to the fragile green sheet. Limited access to the material also demands a one-sided inspection technique. In this paper, we will describe the application of thermography for 100% on-line inspection within an industrial process. This approach is cost competitive with alternative technologies, such as x-ray imaging systems, and provides the required sensitivity to the variations in material composition. The formation of green sheet flaws and their transformation into defects within intermediate and finished sheet products will be described. A green sheet conformance criterion will be presented which would significantly reduce the probability of processing poor quality green sheet which contributes to higher waste and inferior bulk alloy sheet.

  20. Fe sub 3 Al-type iron aluminides: Aqueous corrosion properties in a range of electrolytes and slow-strain-rate ductilities during aqueous corrosion

    SciTech Connect

    Buchanan, R.A.; Kim, J.G. . Dept. of Materials Science and Engineering)

    1992-08-01

    The Fe{sub 3}Al-type iron aluminides have undergone continued development at the Oak Ridge National Laboratory for enhancement of mechanical and corrosion properties. Improved alloys and thermomechanical processing methods have evolved. The overall purpose of the project herein described was to evaluate the aqueous corrosion properties of the most recent alloy compositions in a wide range of possibly-aggressive solutions and under several different types of corrosion-test conditions. The work supplements previous aqueous-corrosion studies on iron aluminides by the present authors. Four stages of this one-year aqueous-corrosion investigation are described. First the corrosion properties of selected iron aluminides were evaluated by means of electrochemical tests and longer-time immersion tests in a range of acidic, basic and chloride solutions. Theses tests were performed under non-crevice conditions, i.e. the specimens were not designed to contain crevice geometries. Second, the iron-aluminide alloy that proved most resistance to chloride-induced localized corrosion under non-crevice conditions was further evaluated under more-severe crevice conditions by electrochemical and immersion testing. Third, in order to study the relative roles of Fe, Al, Cr and Mo in the formation of passive films, the chemical compositions of passive films were determined by X-ray photoelectron spectroscopy (XPS). And fourth, in order to study aqueous-corrosion effects on the ductilities of iron aluminides as related to hydrogen embrittlement and/or stress-corrosion cracking, slow-strain-rate corrosion (SSRC) tests were conducted over a range of electrochemical potentials.

  1. Fe{sub 3}Al-type iron aluminides: Aqueous corrosion properties in a range of electrolytes and slow-strain-rate ductilities during aqueous corrosion

    SciTech Connect

    Buchanan, R.A.; Kim, J.G.

    1992-08-01

    The Fe{sub 3}Al-type iron aluminides have undergone continued development at the Oak Ridge National Laboratory for enhancement of mechanical and corrosion properties. Improved alloys and thermomechanical processing methods have evolved. The overall purpose of the project herein described was to evaluate the aqueous corrosion properties of the most recent alloy compositions in a wide range of possibly-aggressive solutions and under several different types of corrosion-test conditions. The work supplements previous aqueous-corrosion studies on iron aluminides by the present authors. Four stages of this one-year aqueous-corrosion investigation are described. First the corrosion properties of selected iron aluminides were evaluated by means of electrochemical tests and longer-time immersion tests in a range of acidic, basic and chloride solutions. Theses tests were performed under non-crevice conditions, i.e. the specimens were not designed to contain crevice geometries. Second, the iron-aluminide alloy that proved most resistance to chloride-induced localized corrosion under non-crevice conditions was further evaluated under more-severe crevice conditions by electrochemical and immersion testing. Third, in order to study the relative roles of Fe, Al, Cr and Mo in the formation of passive films, the chemical compositions of passive films were determined by X-ray photoelectron spectroscopy (XPS). And fourth, in order to study aqueous-corrosion effects on the ductilities of iron aluminides as related to hydrogen embrittlement and/or stress-corrosion cracking, slow-strain-rate corrosion (SSRC) tests were conducted over a range of electrochemical potentials.

  2. EVALUATION OF THE INTRINSIC AND EXTRINSIC FRACTURE BEHAVIOR OF IRON ALUMINIDES

    SciTech Connect

    Cooper, BR

    2001-10-15

    Comparative finite element modeling simulations of initial intergranular fracture of two iron aluminides (FA186 and FA189) were carried out to study the intrinsic and extrinsic fracture behavior of the alloys as related to hydrogen embrittlement. The computational simulations involved sequentially-coupled stress and mass-diffusion analyses to determine the stress/strain distribution and the extent of hydrogen concentration at the crack tip region. Simulations of initial intergranular fracture of the two alloys under either air or vacuum conditions were conducted. With judicious selection of grain boundary failure strains for each alloy and assumed material degradation at hydrogen diffusion zone, the numerical results agree well with previous experimental test results. We have considered the various methods by which the thermal expansion of Fe{sub 3}Al can be modeled. As a matter of practicality, we have started with a conceptually simple continuum medium modeling, which we have used in initial calculations reported here, despite its limitations in neglecting the effects of optical phonons. This makes the results increasingly suspect for temperatures above the Debye temperature. However, the results we obtain are surprisingly good considering this important limitation. Nevertheless, we regard these results as being suspect. Therefore, in addition, we discuss a wholly new ab-initio-based method which is both more accurate (preserves the ab-initio-generated information) and computationally more efficient. This method can directly transform the all-electron ab initio electronic structure results of the full-potential LMTO electronic structure behavior, computationally provided in reciprocal space, to the real space representation needed for the thermal expansion modeling. An increase of computational speed, use of larger supercells, and more efficient calculations, can all be achieved by using real space (tight-binding (TB)) calculations. The TB parameters are obtained

  3. Evaluation of the Intrinsic and Extrinsic Fracture Behavior of Iron Aluminides

    SciTech Connect

    Cooper, B.R.

    2002-02-08

    Comparative finite element modeling simulations of initial intergranular fracture of two iron aluminides (FA186 and FA189) were carried out to study the intrinsic and extrinsic fracture behavior of the alloys as related to hydrogen embrittlement. The computational simulations involved sequentially-coupled stress and mass-diffusion analyses to determine the stress/strain distribution and the extent of hydrogen concentration at the crack tip region. Simulations of initial intergranular fracture of the two alloys under either air or vacuum conditions were conducted. With judicious selection of grain boundary failure strains for each alloy and assumed material degradation at hydrogen diffusion zone, the numerical results agree well with previous experimental test results. We have considered the various methods by which the thermal expansion of Fe{sub 3}Al can be modeled. As a matter of practicality, we have started with a conceptually simple continuum medium modeling, which we have used in initial calculations reported here, despite its limitations in neglecting the effects of optical phonons. This makes the results increasingly suspect for temperatures above the Debye temperature. However, the results we obtain are surprisingly good considering this important limitation. Nevertheless, we regard these results as being suspect. Therefore, in addition, we discuss a wholly new ab-initio-based method which is both more accurate (preserves the ab-initio-generated information) and computationally more efficient, This method can directly transform the all-electron ab initio electronic structure results of the full-potential LMTO electronic structure behavior, computationally provided in reciprocal space, to the real space representation needed for the thermal expansion modeling. An increase of computational speed, use of larger supercells, and more efficient calculations, can all be achieved by using real space (tight-binding (TB)) calculations. The TB parameters are obtained

  4. Taylor simulation and experimental investigation of rolling textures of polycrystalline iron aluminides with special regard to slip on {l_brace}112{r_brace} planes

    SciTech Connect

    Raabe, D.

    1996-03-01

    The evolution of the crystallographic rolling textures of B2- and DO{sub 3}-ordered polycrystalline iron aluminides is described in terms of taylor-type simulations. The contribution of crystallographic slip on the various types of glide systems, particularly the influence of {l_brace}112{r_brace}<111> slip is examined. The evolution of the aspect ratio of the grains during rolling is considered by gradually relaxing the externally imposed strain constraints with increasing deformation. For simulating low reductions, full constraints Taylor-type conditions are assumed. For describing intermediate reductions the lath model and for large reductions the pancake model is employed. The ratio of the critical resolved shear stress of the {l_brace}110{r_brace}<111> and {l_brace}112{r_brace}<111> slip systems is varied. The predictions yielded by impeding {l_brace}110{r_brace}<111> systems and promoting {l_brace}112{r_brace}<111> systems ({tau}{sub {l_brace}110{r_brace}<111>} = 10 {times} {tau}{sub {l_brace}112{r_brace}<111>}) are in good accord with experiment. The results are discussed in terms of the energy of the antiphase boundaries and of dislocation core effects.

  5. Effects of plasma parameters and collection region on synthesis of iron and nickel aluminide composite particles during thermal plasma processing

    NASA Astrophysics Data System (ADS)

    Suresh, K.; Selvarajan, V.

    2010-02-01

    Iron and Nickel aluminide composite particles were synthesized by non-transferred DC plasma spray torch at atmospheric pressure. Irregular shaped ball milled, micron sized powders were fed in to the plasma flame using argon as carrier gas. The particles got molten and vaporized. The vapour condensed on the walls of the reaction chamber and nanoparticles were formed. The molten particles got spheroidized due to surface tension forces. Powders as formed were collected in the plasma reactor at three different sections (Section A, B and C). These powder particles were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The particle size and morphology of the composite particles strongly varied depending on the processing parameters and collection region. The results were discussed.

  6. Environment-induced embrittlement: Stress corrosion cracking and metal-induced embrittlement; Environmental embrittlement of iron aluminide alloys

    SciTech Connect

    Heldt, L.A.; Milligan, W.W.; White, C.L.

    1991-01-01

    This research program has included two thrusts. The first addressed environment-induced embrittlement in a parallel study of stress corrosion cracking and metal-induced embrittlement. This work has examined (1) mechanical properties as influenced by embrittling environments, (2) fractography and crystallography or transgranular cracking, (3) the mechanics of cracking, (4) the extent and role of local plastic flow, and (5) local chemistry within stress corrosion and metal-induced cracks. The embrittlement of iron aluminide alloys by air was addressed by determining the effect of water and hydrogen upon the mechanical properties. Slow strain rate testing in aqueous environments was carried out at controlled anodic and cathodic potentials. The effect of cathodically charged hydrogen and the effect of subsequent baking were measured. Environmental susceptibility was measured as affected by alloy composition, microstructure and degree of ordering.

  7. Evaluation of Iron Aluminide Weld Overlays for Erosion-Corrosion Resistant Boiler Tube Coatings in Low NOx Boilers

    SciTech Connect

    Regina, J.R.

    2000-05-16

    Iron aluminide weld overlays containing ternary additions and thermal spray coatings are being investigated for corrosion protection of boiler tubes in Low NOx burners. The primary objective of the research is to identify overlay and thermal spray compositions that provide corrosion protection of waterwall boiler tubes. In the current phase of work, preliminary corrosion tests were conducted on a binary Fe-Al alloy in multiple complex gases to determine which gases will be used for testing of the ternary alloys. Preliminary solid-state corrosion tests were also conducted to simulate slag-metal interactions seen in Low NOx furnaces. Two powder compositions were chosen for testing of the ternary alloys. A matrix of alloys to be tested in both gaseous and solid-state corrosion experiments was produced based on corrosion literature.

  8. The ductile-brittle size transition of iron aluminide ligaments in an FeAl/TiC composite

    SciTech Connect

    Subramanian, R.; Schneibel, J.H.

    1998-08-10

    The fracture surfaces of FeAl/TiC composites containing 70 vol% TiC were investigated. Since thin iron aluminide ligaments in the composites fractured in a ductile manner, whereas thicker ones fractured by cleavage, a systematic correlation of the fracture mode to the ligament thickness was performed. The results clearly show that FeAl ligaments thicker than about 1--2 {micro}m fracture by cleavage and those smaller in size fracture predominantly in a ductile manner. The ductile failure mode is attributed to the limited dislocation pile-up distance available for very thin ligaments, which prevents high stresses from building up and eliminates cleavage fracture. It is also shown that the ductile-brittle transition size is controlled by alloying and/or heat treatment. No significant dependence of the fracture toughness on the fracture mode would be found.

  9. High-temperature corrosion and applications of nickel and iron aluminides in coal-conversion power systems

    SciTech Connect

    Natesan, K.; Tortorelli, P.F.

    1996-10-01

    Nickel and iron aluminide intermetallics are being developed for use as structural materials and/or as cladding for conventional engineering alloys. In addition to strength advantages, these materials exhibit excellent resistance to corrosion in single- and multioxidant environments at elevated temperatures by the formation of slow-growing, adherent alumina scales. Corrosion resistance in a given environment is strongly dependent on the composition of the alloy and on the nature of the corrosive species prevalent in the service environment. This paper presents a comprehensive review of the current status of the corrosion performance of these intermetallics in oxidizing, sulfidizing, and multicomponent gas environments of typical coal-conversion systems. Mechanisms of scale development/breakdown, performance envelopes for long-term usage of these materials, approaches to modifying the surfaces of engineering alloys by cladding or coating them with intermetallics, and in-service experience with these materials are emphasized.

  10. Effects of 1000 C oxide surfaces on room temperature aqueous corrosion and environmental embrittlement of iron aluminides

    SciTech Connect

    Buchanan, R.A.; Perrin, R.L.

    1997-12-01

    Results of electrochemical aqueous-corrosion studies at room temperature indicate that retained in-service-type high-temperature surface oxides (1000 C in air for 24 hours) on FA-129, FAL and FAL-Mo iron aluminides cause major reductions in pitting corrosion resistance in a mild acid-chloride solution designed to simulate aggressive atmospheric corrosion. Removal of the oxides by mechanical grinding restores the corrosion resistance. In a more aggressive sodium tetrathionate solution, designed to simulate an aqueous environment contaminated by sulfur-bearing combustion products, only active corrosion occurs for both the 1000 C oxide and mechanically cleaned surfaces at FAL. Results of slow-strain-rate stress-corrosion-cracking tests on FA-129, FAL and FAL-Mo at free-corrosion and hydrogen-charging potentials in the mild acid chloride solution indicate somewhat higher ductilities (on the order of 50%) for the 1000 C oxides retard the penetration of hydrogen into the metal substrates and, consequently, are beneficial in terms of improving resistance to environmental embrittlement. In the aggressive sodium tetrathionate solution, no differences are observed in the ductilities produced by the 1000 C oxide and mechanically cleaned surfaces for FAL.

  11. Effect of thermomechanical treatments on the room-temperature mechanical behavior of iron aluminide Fe{sub 3}Al

    SciTech Connect

    Agarwal, A.; Balasubramaniam, R.; Bhargava, S.

    1996-10-01

    The room-temperature hydrogen embrittlement (HE) problem in iron aluminides has restricted their use as high-temperature structural materials. The role of thermomechanical treatments (TMT), i.e., rolling at 500 C, 800 C, and 1,000 C, and post-TMT heat treatments, i.e., recrystallization at 750 C and ordering at 500 C, in affecting the room-temperature mechanical properties of Fe-25Al intermetallic alloy has been studied from a processing-structure-properties correlation viewpoint. It was found that when this alloy is rolled at higher temperature, it exhibits a higher fracture strength. This has been attributed to find subgrain size (28 {micro}) due to dynamic recrystallization occurring at the higher rolling temperature of 1,000 C. However, when this alloy is rolled at 1,000 C and then recrystallized, it shows the highest ductility but poor fracture strength. This behavior has been ascribed to the partially recrystallized microstructure, which prevents hydrogen ingress through grain boundaries and minimizes hydrogen embrittlement. When the alloy is rolled at 1,000 C and then ordered at 500 C for 100 hours, it shows the highest fracture strength, due to its finer grain size. The alloy rolled at 500 C and then ordered undergoes grain growth. Hence, it exhibits a lower fracture strength of 360 MPa. Fracture morphologies of the alloy were found to be typical of brittle fracture, i.e., cleavage-type fracture in all the cases.

  12. Microstructure control in iron aluminides by phase decomposition or by mechanical alloying for improved strength and ductility

    SciTech Connect

    Morris, D.G.; Gunther, S.

    1997-12-31

    The iron aluminides based on Fe{sub 3}Al or FeAl being developed for intermediate temperature applications suffer from mediocre room temperature strength and ductility and poor high temperature tensile and creep strength. Attempts to overcome these problems have been restricted by the limited possibilities of structure modification by, for example, precipitation of stable strengthening particles. The present study examines two approached to obtaining two-phase mixtures for improved strength and ductility: by adjusting chemical compositions such that two-phase order-disorder ({alpha}-{alpha}{double_prime}) mixtures are obtained, and by mechanical alloying. Two-phase {alpha}-{alpha}{double_prime} mixtures are obtained by heat treatment of Fe-Al alloys with Al content near 20--24% and in ternary Fe-Al-Si alloys with suitably adjusted Al and Si contents. Microstructures of such alloys can be modified during heat treatments by ordering, precipitation or decomposition, and two-phase mixtures similar to those in the {gamma}-{gamma}{prime} superalloys obtained. Such two-phase alloys show good high temperature tensile and creep strength with some indication of reasonable ductility and reduced environmental sensitivity. Mechanical alloying can easily produce Fe-Al alloys of fine grain size reinforced with stable oxide particles. These structures lead to high room temperature strength with some ductility; controlled recrystallization can significantly modify both strength and ductility.

  13. Effect of thermomechanical treatments on the room-temperature mechanical behavior of iron aluminide Fe3AI

    NASA Astrophysics Data System (ADS)

    Agarwal, Arvind; Balasubramaniam, R.; Bhargava, S.

    1996-10-01

    The room-temperature hydrogen embrittlement (HE) problem in iron aluminides has restricted their use as high-temperature structural materials. The role of thermomechanical treatments (TMT), i.e., rolling at 500 °C, 800 °C, and 1000 °C, and post-TMT heat treatments, i.e., recrystallization at 750 °C and ordering at 500 °C, in affecting the room-temperature mechanical properties of Fe-25A1 intermetallic alloy has been studied from a processing-structure-properties correlation viewpoint. It was found that when this alloy is rolled at higher temperature, it exhibits a higher fracture strength. This has been attributed to fine subgrain size (28 /μ) due to dynamic recrystallization occurring at the higher rolling temperature of 1000 °C. However, when this alloy is rolled at 1000 °C and then recrystallized, it shows the highest ductility but poor fracture strength. This behavior has been ascribed to the partially recrystallized microstructure, which prevents hydrogen ingress through grain boundaries and minimizes hydrogen embrittlement. When the alloy is rolled at 1000 °C and then ordered at 500 °C for 100 hours, it shows the highest fracture strength, due to its finer grain size. The alloy rolled at 500 °C and then ordered undergoes grain growth. Hence, it exhibits a lower fracture strength of 360 MPa. Fracture morphologies of the alloy were found to be typical of brittle fracture, i.e., cleavage-type fracture in all the cases.

  14. Cast B2-phase iron-aluminum alloys with improved fluidity

    DOEpatents

    Maziasz, Philip J.; Paris, Alan M.; Vought, Joseph D.

    2002-01-01

    Systems and methods are described for iron aluminum alloys. A composition includes iron, aluminum and manganese. A method includes providing an alloy including iron, aluminum and manganese; and processing the alloy. The systems and methods provide advantages because additions of manganese to iron aluminum alloys dramatically increase the fluidity of the alloys prior to solidification during casting.

  15. Aluminide coatings

    DOEpatents

    Henager, Jr; Charles, H [Kennewick, WA; Shin, Yongsoon [Richland, WA; Samuels, William D [Richland, WA

    2009-08-18

    Disclosed herein are aluminide coatings. In one embodiment coatings are used as a barrier coating to protect a metal substrate, such as a steel or a superalloy, from various chemical environments, including oxidizing, reducing and/or sulfidizing conditions. In addition, the disclosed coatings can be used, for example, to prevent the substantial diffusion of various elements, such as chromium, at elevated service temperatures. Related methods for preparing protective coatings on metal substrates are also described.

  16. Environment-induced embrittlement: Stress corrosion cracking and metal-induced embrittlement; Environmental embrittlement of iron aluminide alloys. Final report, September 1, 1986--August 31, 1991

    SciTech Connect

    Heldt, L.A.; Milligan, W.W.; White, C.L.

    1991-12-31

    This research program has included two thrusts. The first addressed environment-induced embrittlement in a parallel study of stress corrosion cracking and metal-induced embrittlement. This work has examined (1) mechanical properties as influenced by embrittling environments, (2) fractography and crystallography or transgranular cracking, (3) the mechanics of cracking, (4) the extent and role of local plastic flow, and (5) local chemistry within stress corrosion and metal-induced cracks. The embrittlement of iron aluminide alloys by air was addressed by determining the effect of water and hydrogen upon the mechanical properties. Slow strain rate testing in aqueous environments was carried out at controlled anodic and cathodic potentials. The effect of cathodically charged hydrogen and the effect of subsequent baking were measured. Environmental susceptibility was measured as affected by alloy composition, microstructure and degree of ordering.

  17. Surface Gasification Materials Program semiannual progress report for the period ending March 31, 1986. [Fe/sub 3/Al (iron aluminides)

    SciTech Connect

    Not Available

    1986-06-01

    The objective of the Surface Gasification Materials Program is to conduct research and development on materials for application to the specific needs of coal gasification systems. One of the goals of the program is to evaluate innovative fabrication methods which have the potential to lower costs and improve reliability and safety for gasifier vessels and components. Another goal is to conduct engineering-scale development and application of materials for coal gasification systems to ensure that the materials of construction for pilot plants and future large-scale plants can be properly selected and specified. Contents of this semiannual progress report include: (1) protective coatings and claddings - application/evaluation; (2) corrosion of structural ceramics in coal gasification environments; (3) electroslag component casting; and (4) development of iron aluminides. 8 figs., 14 tabs.

  18. ODS iron aluminides

    SciTech Connect

    Wright, I.G.; Pint, B.A.; Tortorelli, P.F.; Ohriner, E.K.

    1996-06-01

    Interest in advanced cycles that involve indirectly-fired gas turbines, in which coal- or gas-fired high-temperature heat exchangers are used to heat a working fluid in a closed system, has led to investigation of materials for heat exchangers capable of operation at temperatures of the order of 1200 to 1300{degrees}C. The candidate materials are ceramics and, possibly, oxide dispersion-strengthened (ODS) alloys. An ODS FeCrAl alloy was found to meet the strength requirements for such an application, in which the working fluid at 0.9 MPa was to be heated from 800 to 1100{degrees}C over a tube length of 4 m. The oxidation life of ODS FeCrAl alloys is determined by their ability to form or reform a protective alumina scale, and can be related to the time for the aluminum content of the alloy to be depleted to some minimum level. As a result, the service life is a function of the available aluminum content of the alloys and the minimum aluminum level at which breakaway oxidation occurs, hence there is a limit on the minimum cross section which can be safely employed at temperatures above 1200{degrees}C. Because of their significantly higher aluminum content ({ge}28 atom %/{ge}16 wt. percent compared to {approx}9 atom %15 wt. percent), alloys based on Fe{sub 3}Al afford a potentially larger reservoir of aluminum to sustain oxidation resistance at higher temperatures and, therefore, offer a possible improvement over the currently-available ODS FeCrAl alloys, providing they can be strengthened in a similar manner.

  19. Development of iron aluminides

    SciTech Connect

    Goodwin, G.M.

    1996-06-01

    Alloys based on the intermetallic compound Fe{sub 3}Al exhibit many attractive properties, particularly excellent resistance to high temperature oxidation. Their use in commercial applications has been limited, however, by the limited workability of wrought material and the susceptibility of weldments to both hot and cold cracking. Prior efforts have systematically evaluated the effect of alloy composition on hot cracking. By the use of the Sigmajig test, we have found that hot cracking can essentially be eliminated by the addition of carbon and the control of maximum levels of niobium, zirconium, and other alloying elements. Cold cracking, however, remains an issue, and recent efforts have been aimed at minimizing its occurrence, concurrent with development of welding filler metals, processes, and procedures aimed at commercial applications.

  20. ODS iron aluminides

    SciTech Connect

    Wright, I.G.; Pint, B.A.; Ohriner, E.K.; Tortorelli, P.F.

    1996-08-01

    The overall goal of this program is to develop an oxide dispersion-strengthened (ODS) version of Fe{sub 3}Al that has sufficient creep strength and resistance to oxidation at temperatures in the range 1000 to 1200{degrees}C to be suitable for application as heat exchanger tubing in advanced power generation cycles. The program has two main thrusts: (a) alloy processing, which involves mechanical alloying and thermomechanical processing to achieve the desired size and distribution of the oxide dispersoid, and (b) optimization of the oxidation behavior to provide increased service life compared to ODS-FeCrAl alloys intended for the same applications. Control of the grain size and shape in the final alloy is very dependent on the homogeneity of the alloy powder, in terms of the size and distribution of the dispersed oxide particles, and on the level of strain and temperature applied in the recrystallization step. Studies of the effects of these variables are being made using mechanically-alloyed powder from two sources: a commercial powder metallurgy alloy vendor and an in-house, controlled environment high-energy mill. The effects of milling parameters on the microstructure and composition of the powder and consolidated alloy are described. Comparison of the oxidation kinetics of ODS-Fe{sub 3}Al alloys with commercial ODS-FeCrAl alloys in air at 1000-1300{degrees}C indicated that the best Fe{sub 3}Al-based alloys oxidized isothermally at the same rate as the ODS-FeCrAl alloys but, under thermal cycling conditions, the oxidation rate of ODS-Fe{sub 3}Al was faster. The main difference was that the ODS-Fe{sub 3}Al experienced significantly more scale spallation above 1000{degrees}C. The differences in oxidation behavior were translated into expected lifetimes which indicated that, for an alloy section thickness of 2.5 mm, the scale spallation of ODS-Fe{sub 3}Al leads to an expected service lifetime similar to that for the INCO alloy MA956 at 1100 to 1300{degrees}C.

  1. ODS iron aluminides

    SciTech Connect

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

    1995-07-01

    Since oxide dispersion-strengthened (ODS) FeCrAl-based alloys have sufficient creep strength and good oxidation resistance at the very high temperatures of interest for the primary heat exchanger in advanced, closed-cycle gas turbine systems, they constitute viable alternative candidates to ceramics. A major life-limiting factor of these alloys is the ability to continue to form a protective scale of aluminum oxide, a factor proportional to the total amount of aluminum contained in the alloy. Fe{sub 3}Al has oxidation resistance comparable to that of the FeCrAl-based alloys, and significantly superior sulfidation resistance. Also, because of its larger reservoir of aluminum, Fe{sub 3}Al would be expected to exhibit longer lifetimes at the temperatures of interest. Since the strengthening effects of ODS processing are expected to confer similar high-temperature creep properties to those found for the FeCrAl-based alloys, ODS-Fe{sub 3}Al is considered to have excellent potential for the very high-temperature heat exchanger application. The program effort on ODS Fe{sub 3}Al includes examination of the properties of available ODS-FeCrAl alloys; development of mechanical alloying parameters for ODS-Fe{sub 3}Al; determination of the effects of a dispersion of reactive element oxides on the high-temperature oxidation behavior of Fe{sub 3}Al; and evaluation of methods for joining them.

  2. ODS iron aluminides

    SciTech Connect

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

    1995-06-01

    There has been a recent increase of interest in advanced cycles that involve indirectly-fired gas turbines, in which coal- or gas-fired high-temperature heat exchangers are used to heat a working fluid in a closed system. In a program conducted as part of the European COST-501 Concerted Action Project, available alloys based on FeCrAl-Y{sub 2}O{sub 3} were evaluated for use in the main heat exchanger in a similar closed-cycle gas turbine application. One of the currently available ODS FeCrAl alloys was found to meet the strength requirements for this application, in which the working fluid at 0.9 MPa (131 psi) flowing at 5,889 kg/hr (12,955 lb/hr) was to be heated from 800 to 1100{degrees}C (1472 to 2012{degrees}F) over a tube length of 4 m (13 ft).

  3. Weldability of polycrystalline aluminides

    SciTech Connect

    Fasching, A.A.; Edwards, G.R.; David, S.A.

    1993-07-01

    Iron aluminide alloy FA-129 is susceptible to cold cracking during gas-tungsten arc (GTA) welding. Cracking occurs by brittle fracture in the fusion zone, which has been attributed to excessive grain growth during solidification, in concert with environmental embrittlement. Previous work has shown that iron aluminide can be susceptible to environmental embrittlement when tested in the presence of water vapor. The suggested mechanism is similar to that observed in aluminum alloys: the reaction of water molecules with freshly exposed aluminum atoms at the crack tip results in the formation of high activity atomic hydrogen, which diffuses into the metal and causes embrittlement. This phenomenon occurs only when the metal is stressed, and therefore, is a dynamic embrittlement phenomenon. The same effect was not seen in experiments conducted in the presence of hydrogen gas. To further investigate this embrittlement problem and its effect on welding, GTA welds were conducted in atmospheres of varying amounts of water vapor on base material of varying grain sizes. The varying base material grain sizes were chosen because fusion zone grain size depends, to an extent, on the grain size of the base material. For example, a fine-grained base material should produce a finer grained fusion zone that a coarse-grained base material would. The results of the investigation are presented within this paper.

  4. Corrosion of aluminides by molten nitrate salt

    SciTech Connect

    Tortorelli, P.F.; Bishop, P.S.

    1990-01-01

    The corrosion of titanium-, iron-, and nickel-based aluminides by a highly aggressive, oxidizing NaNO{sub 3}(-KNO{sub 3})-Na{sub 2}O{sub 2} has been studied at 650{degree}C. It was shown that weight changes could be used to effectively evaluate corrosion behavior in the subject nitrate salt environments provided these data were combined with salt analyses and microstructural examinations. The studies indicated that the corrosion of relatively resistant aluminides by these nitrate salts proceeded by oxidation and a slow release from an aluminum-rich product layer into the salt at rates lower than that associated with many other types of metallic materials. The overall corrosion process and resulting rate depended on the particular aluminide being exposed. In order to minimize corrosion of nickel or iron aluminides, it was necessary to have aluminum concentrations in excess of 30 at. %. However, even at a concentration of 50 at. % Al, the corrosion resistance of TiAl was inferior to that of Ni{sub 3}Al and Fe{sub 3}Al. At higher aluminum concentrations, iron, nickel, and iron-nickel aluminides exhibited quite similar weight changes, indicative of the principal role of aluminum in controlling the corrosion process in NaNO{sub 3}(-KNO{sub 3})-Na{sub 2}O{sub 2} salts. 20 refs., 5 figs., 3 tabs.

  5. Method of manufacturing aluminide sheet by thermomechanical processing of aluminide powders

    DOEpatents

    Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleishhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

    2003-12-09

    A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

  6. Method of manufacturing aluminide sheet by thermomechanical processing of aluminide powders

    DOEpatents

    Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

    2000-01-01

    A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr.ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

  7. Method of manufacturing aluminide sheet by thermomechanical processing of aluminide powders

    SciTech Connect

    Hajaligol, M.R.; Scorey, C.; Sikka, V.K.; Deevi, S.C.; Fleischhauer, G.; Lilly, A.C. Jr.; German, R.M.

    2000-02-29

    A powder metallurgical process is disclosed of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as {<=}1% Cr, {>=}0.05% Zr{<=}2% Ti, {<=}2% Mo, {<=}1% Ni, {<=}0.75% C, {<=}0.1% B, {<=}1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, {<=}1% rare earth metal, and/or {<=}3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 {mu}m. Final stress relief annealing can be carried out in the B2 phase temperature range.

  8. Iron abundance in the hot DA white dwarfs Feige 24 and G191 B2B

    NASA Technical Reports Server (NTRS)

    Vennes, Stephane; Chayer, Pierre; Thorstensen, John R.; Bowyer, Stuart; Shipman, Harry L.

    1992-01-01

    Attention is given to model calculations of the far- and extreme-UV line spectra of highly ionized Fe species (Fe IV, Fe V, and Fe VI) for hot high-gravity H-rich stars. A spectral analysis of 31 hr of exposure of the DA white dwarf Feige 24 with IUE in the echelle mode reveals the presence of Fe with an abundance relative to H by number of (5-10) x 10 exp -6 with an uncertainty dominated by the determination of stellar parameters. An analysis of IUE data from the white dwarf G191 B2B results in a similar Fe abundance if this star shares similar atmospheric parameters (Teff, g) with Feige 24. Fe is thus the second most abundant photospheric element in hot DA white dwarfs.

  9. Engineering processing and properties of nickel aluminides

    SciTech Connect

    Sikka, V.K.

    1988-01-01

    Ordered intermetallic compounds of iron, nickel, and titanium are materials recently under development for structural applications. Among these, Ni/sub 3/Al has been made reasonably ductile by the addition of small amounts of boron. Further additions of zirconium and chromium have been utilized for enhancement of high temperature strength and intermediate temperature ductility. Nickel aluminide alloys based on Ni/sub 3/Al are near commercialization. This paper describes the melting, processing, mechanical properties, physical properties, corrosion, and weldability of these alloys. Applications for nickel aluminides have been identified. Potential suppliers who have recently licensed the nickel aluminide technology from Oak Ridge National Laboratory (ORNL) are also listed. 16 refs., 7 figs., 7 tabs.

  10. Compositional effects on processing and properties of nickel aluminides

    SciTech Connect

    Sikka, V.K.

    1988-01-01

    Compositional effects on hot and cold workability of ductile-ordered nickel aluminides are described. Compositional affects studied variation of chromium, aluminium, iron, and zirconium. The hot and cold workability of various nickel-aluminide alloys was ranked with respect to workability of stainless steel. The nickel-aluminide alloy containing chromium and low zirconium (IC-218LZr) had the best combination of hot and cold workability. This alloy also offered a good combination of strength and ductility values over a range of test temperatures. 3 refs., 8 figs., 1 tab.

  11. Diffusion bonding of iron aluminide Fe{sub 72}Al{sub 28} using a copper interlayer

    SciTech Connect

    Torun, O.; Celikyuerek, I.; Guerler, R.

    2008-07-15

    An Fe{sub 72}Al{sub 28} alloy was diffusion-bonded using a copper interlayer under vacuum at 1075 deg. C for 1 h, 2 h, 4 h and 6 h durations at 3.2 MPa applied pressure. The bond microstructure was found to be composed of the copper rich interlayer, copper rich precipitates and the base metal. SEM-EDS studies indicated major diffusion of aluminium and iron atoms from Fe{sub 72}Al{sub 28} into the copper interlayer and copper atoms from the copper interlayer into the Fe{sub 72}Al{sub 28} matrix. SEM observations of fractured surfaces of the diffusion-bonded samples showed some plastic deformation and signs of good bonding. Cu{sub 3}Al and B{sub 2}-FeAl-based phases were identified by SEM-EDS and X-ray diffraction studies at the bond and on the fracture surfaces of all samples investigated. Good bonding was achieved with a maximum shear strength of 298 MPa which is 65% of the parent material shear strength for a sample diffusion-bonded for 6 h.

  12. Weldability of polycrystalline aluminides. Final report

    SciTech Connect

    Fasching, A.A.; Burt, R.P.; Edwards, G.R.; David, S.A.

    1996-07-01

    When gas-tungsten arc welded, iron aluminides form a coarse fusion zone microstructure which is susceptible to hydrogen cracking. Magnetic arc oscillation and weld pool inoculation were implemented to refine the fusion zone microstructure in iron aluminide alloy FA-129 weldments. Magnetic arc oscillation effectively refined the fusion zone microstructure, and slow strain rate tensile tests showed fine-grained microstructures to be less susceptible to hydrogen cracking. However, magnetic arc oscillation was found to be suitable only for well-controlled fabrication environments. Weld pool inoculation offers a potentially more robust refinement method. Titanium inoculation was also shown to effectively refined the fusion zone microstructure, but weldment properties were not improved using this refinement method. The effect of titanium on the size, shape and distribution of the second phase particles in the fusion zone appears to be the cause of the observed decrease in weldment properties.

  13. Proposal of new structure of MgB 2 wires with low AC loss for stator windings of fully superconducting motors located in iron core slots

    NASA Astrophysics Data System (ADS)

    Kajikawa, K.; Osaka, R.; Kuga, H.; Nakamura, T.; Wakuda, T.

    2011-11-01

    The new structure of MgB 2 monofilamentary wires for stator windings of fully superconducting motors is proposed to reduce their AC losses in iron core slots for the application of an alternating transport current. In order to validate the proposed structure of wire for loss reduction, numerical calculations are carried out by means of a finite element method using edge elements formulated with a self-field due to currents induced in an analysis region. It is assumed that the voltage-current characteristics of the MgB 2 superconductor are given by Bean’s critical state model, in which the critical current density is independent of the local magnetic field. The influences of wire structures on the AC losses are discussed quantitatively toward the optimum design of stator windings in fully superconducting motors with the MgB 2 wires.

  14. Prospects for three-electron donor boronyl (BO) ligands and dioxodiborene (B2O2) ligands as bridging groups in binuclear iron carbonyl derivatives.

    PubMed

    Chang, Yu; Li, Qian-Shu; Xie, Yaoming; King, R Bruce

    2012-08-20

    Recent experimental work (2010) on (Cy(3)P)(2)Pt(BO)Br indicates that the oxygen atom of the boronyl (BO) ligand is more basic than that in the ubiquitous CO ligand. This suggests that bridging BO ligands in unsaturated binuclear metal carbonyl derivatives should readily function as three-electron donor bridging ligands involving both the oxygen and the boron atoms. In this connection, density functional theory shows that three of the four lowest energy singlet Fe(2)(BO)(2)(CO)(7) structures have such a bridging η(2)-μ-BO group as well as a formal Fe-Fe single bond. In addition, all four of the lowest energy singlet Fe(2)(BO)(2)(CO)(6) structures have two bridging η(2)-μ-BO groups and formal Fe-Fe single bonds. Other Fe(2)(BO)(2)(CO)(n) (n = 7, 6) structures are found in which the two BO groups have coupled to form a bridging dioxodiborene (B(2)O(2)) ligand with B-B bonding distances of ~1.84 Å. All of these Fe(2)(μ-B(2)O(2))(CO)(n) structures have long Fe···Fe distances indicating a lack of direct iron-iron bonding. One of the singlet Fe(2)(BO)(2)(CO)(7) structures has such a bridging dioxodiborene ligand with cis stereochemistry functioning as a six-electron donor to the pair of iron atoms. In addition, the lowest energy triplet structures for both Fe(2)(BO)(2)(CO)(7) and Fe(2)(BO)(2)(CO)(6) have bridging dioxodiborene ligands with trans stereochemistry functioning as a four-electron donor to the pair of iron atoms. PMID:22862812

  15. Thermal strains in titanium aluminide and nickel aluminide composites

    SciTech Connect

    Saigal, A.; Kupperman, D.S.

    1992-07-01

    Neutron diffraction was used to measure residual thermal strains developed during postfabrication cooling in titanium aluminide and nickel aluminide intermetallic matrix composites. Silicon carbide /Ti 14Al-21Nb, tungsten and sapphire/NiAl, and sapphire and SiC-coated sapphire/NiAl{sub 25}Fe{sub 10} composites were investigated. The thermal expansion coefficient of the matrix is usually greater than that of the fibers. As such, during cooldown, compressive residual strains are generated in the fibers and tensile residual strains are generated in the matrix, parallel to the fibers. Liquid-nitrogen dipping and thermal cycling tend to reduce the fabrication-induced residual strains in silicon carbide-fiber-reinforced titanium aluminide matrix composites. However, matrix cracking can occur as a result of these processes. The axial residual strains in the matrix were lower in the nickel aluminide matrix than in the titanium aluminide matrix. As the matrix undergoes plastic deformation, residual thermal strains are related to the yield stress of the matrix.

  16. Aluminide Coatings for Power-Generation Applications

    SciTech Connect

    Zhang, Y

    2003-11-17

    Aluminide coatings are of interest for many high temperature applications because of the possibility of improving the oxidation of structural alloys by forming a protective external alumina scale. In order to develop a comprehensive lifetime evaluation approach for aluminide coatings used in fossil energy systems, some of the important issues have been addressed in this report for aluminide coatings on Fe-based alloys (Task I) and on Ni-based alloys (Task II). In Task I, the oxidation behavior of iron aluminide coatings synthesized by chemical vapor deposition (CVD) was studied in air + 10vol.% H{sub 2}O in the temperature range of 700-800 C and the interdiffusion behavior between the coating and substrate was investigated in air at 500-800 C. Commercial ferritic (Fe-9Cr-1Mo) and type 304L (Fe-18Cr-9Ni, nominally) austenitic stainless steels were used as the substrates. For the oxidation study, the as-deposited coating consisted of a thin (<5 {micro}m), Al-rich outer layer above a thicker (30-50 {micro}m), lower Al inner layer. The specimens were cycled to 1000 1-h cycles at 700 C and 500 1-h cycles at 800 C, respectively. The CVD coating specimens showed excellent performance in the water vapor environment at both temperatures, while the uncoated alloys were severely attacked. These results suggest that an aluminide coating can substantially improve resistance to water vapor attack under these conditions. For the interdiffusion study, the ferritic and austenitic steels were coated with relatively thicker aluminide coatings consisting of a 20-25 {micro}m outer layer and a 150-250 {micro}m inner layer. The composition profiles before and after interdiffusion testing (up to 5,000h) were measured by electron probe microanalysis (EPMA). The decrease of the Al content at the coating surface was not significant after extended diffusion times ({le} 5,000h) at temperatures {le} 700 C. More interdiffusion occurred at 800 C in coatings on both Fe- 9Cr-1Mo and 304L alloys; a

  17. Trapped field of 1.1 T without flux jumps in an MgB2 bulk during pulsed field magnetization using a split coil with a soft iron yoke

    NASA Astrophysics Data System (ADS)

    Fujishiro, H.; Mochizuki, H.; Ainslie, M. D.; Naito, T.

    2016-08-01

    MgB2 superconducting bulks have promising potential as trapped field magnets. We have achieved a trapped field of B z = 1.1 T on a high-J c MgB2 bulk at 13 K without flux jumps by pulsed field magnetization (PFM) using a split-type coil with a soft iron yoke, which is a record-high trapped field by PFM for bulk MgB2 to date. The flux jumps, which frequently took place using a solenoid-type coil during PFM, were avoided by using the split-type coil, and the B z value was enhanced by the insertion of soft iron yoke. The flux dynamics and heat generation/propagation were analyzed during PFM using a numerical simulation, in which the magnetic flux intruded and attenuated slowly in the bulk and tended to align along the axial direction due to the presence of soft iron yoke. The advantages of the split-type coil and the simultaneous use of a soft iron yoke are discussed.

  18. Nickel aluminide alloys with improved weldability

    DOEpatents

    Santella, M.L.; Goodwin, G.M.

    1995-05-09

    Weldable nickel aluminide alloys which are essentially free, if not entirely free, of weld hot cracking are provided by employing zirconium concentrations in these alloys of greater than 2.6 wt. % or sufficient to provide a substantial presence of Ni--Zr eutectic phase in the weld so as to prevent weld hot cracking. Weld filler metals formed from these so modified nickel aluminide alloys provide for crack-free welds in previously known nickel aluminide alloys. 5 figs.

  19. Nickel aluminide alloys with improved weldability

    DOEpatents

    Santella, Michael L.; Goodwin, Gene M.

    1995-05-09

    Weldable nickel aluminide alloys which are essentially free, if not entirely free, of weld hot cracking are provided by employing zirconium concentrations in these alloys of greater than 2.6 wt. % or sufficient to provide a substantial presence of Ni--Zr eutectic phase in the weld so as to prevent weld hot cracking. Weld filler metals formed from these so modified nickel aluminide alloys provide for crack-free welds in previously known nickel aluminide alloys.

  20. Weld overlay cladding with iron aluminides

    SciTech Connect

    Goodwin, G.M.

    1997-12-01

    The author has established a range of compositions for these alloys within which hot cracking resistance is very good, and within which cold cracking can be avoided in many instances by careful control of welding conditions, particularly preheat and postweld heat treatment. For example, crack-free butt welds have been produced for the first time in 12-mm thick wrought Fe{sub 3}Al plate. Cold cracking, however, still remains an issue in many cases. The author has developed a commercial source for composite weld filler metals spanning a wide range of achievable aluminum levels, and are pursuing the application of these filler metals in a variety of industrial environments. Welding techniques have been developed for both the gas tungsten arc and gas metal arc processes, and preliminary work has been done to utilize the wire arc process for coating of boiler tubes. Clad specimens have been prepared for environmental testing in-house, and a number of components have been modified and placed in service in operating kraft recovery boilers. In collaboration with a commercial producer of spiral weld overlay tubing, the author is attempting to utilize the new filler metals for this novel application.

  1. 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.

  2. Melting of iron-aluminide alloys

    SciTech Connect

    Sikka, V.K.

    1990-01-01

    The melting of Fe{sub 3}Al-based alloys at the Oak Ridge National Laboratory (ORNL) and commercial vendors is described. The melting processes evaluated includes are melting, air-induction melting (AIM), vacuum-induction melting (VIM), and electroslag remelting (ESR). The quality of the ingots studied are base on internal soundness and the surface finish obtained. The ingots were analyzed for recovery of various elements during melting. The impurity levels observed in the alloys by various melting processes were compared. Recommendations are made for viable processes for commercial melting of these alloys. 1 ref., 5 figs., 3 tabs.

  3. Iron aluminide knife and method thereof

    DOEpatents

    Sikka, V.K.

    1997-08-05

    Fabricating an article of manufacture having a Fe{sub 3}Al-based alloy cutting edge is discussed. The fabrication comprises the steps of casting an Fe{sub 3}Al-based alloy, extruding into rectangular cross section, rolling into a sheet at 800 C for a period of time followed by rolling at 650 C, cutting the rolled sheet into an article having an edge, and grinding the edge of the article to form a cutting edge. 1 fig.

  4. Iron aluminide knife and method thereof

    DOEpatents

    Sikka, Vinod K.

    1997-01-01

    Fabricating an article of manufacture having a Fe.sub.3 Al-based alloy cutting edge. The fabrication comprises the steps of casting an Fe.sub.3 Al-based alloy, extruding into rectangular cross section, rolling into a sheet at 800.degree. C. for a period of time followed by rolling at 650.degree. C., cutting the rolled sheet into an article having an edge, and grinding the edge of the article to form a cutting edge.

  5. 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.

  6. Weldability of polycrystalline aluminides. Topical report

    SciTech Connect

    Fasching, A.A.; Edwards, G.R.; David, S.A.

    1995-07-01

    To investigate hydrogen cold cracking in iron aluminides and, specifically, to study the effect of fusion zone grain size on cracking susceptibility, welds were produced using magnetic arc oscillation to refine the fusion zone grain structures. Conventional welding produced extremely coarse columnar fusion zone grains (an average linear dimension of 530 micrometers) while welds produced with a magnetically oscillated arc contained equiaxed fusion zone grains averaging 115 micrometers in diameter. Slow strain rate tensile tests were conducted in varying water vapor atmospheres, on weldments with average fusion zone grain sizes ranging between 115 and 530 micrometers. Fracture strength and percent strain to fracture were measured for each fusion zone microstructure. The fracture strength increased in proportion to the inverse square root of the mean grain diameter, and decreased with increasing water vapor concentration. The results of the tensile tests showed that finer, equiaxed fusion zones were less susceptible to hydrogen cracking and more tolerant of high hydrogen concentrations than coarse fusion zone grain structures. Microstructural refinement via arc oscillation was also found to be suitable only for well-controlled fabrication environments.

  7. Electronic Structure of the Ferryl Intermediate in the α-Ketoglutarate Dependent Non-Heme Iron Halogenase SyrB2: Contributions to H Atom Abstraction Reactivity.

    PubMed

    Srnec, Martin; Wong, Shaun D; Matthews, Megan L; Krebs, Carsten; Bollinger, J Martin; Solomon, Edward I

    2016-04-20

    Low temperature magnetic circular dichroism (LT MCD) spectroscopy in combination with quantum-chemical calculations are used to define the electronic structure associated with the geometric structure of the Fe(IV)═O intermediate in SyrB2 that was previously determined by nuclear resonance vibrational spectroscopy. These studies elucidate key frontier molecular orbitals (FMOs) and their contribution to H atom abstraction reactivity. The VT MCD spectra of the enzymatic S = 2 Fe(IV)═O intermediate with Br(-) ligation contain information-rich features that largely parallel the corresponding spectra of the S = 2 model complex (TMG3tren)Fe(IV)═O (Srnec, M.; Wong, S. D.; England, J; Que, L; Solomon, E. I. Proc. Natl. Acad. Sci. USA 2012, 109, 14326-14331). However, quantitative differences are observed that correlate with π-anisotropy and oxo donor strength that perturb FMOs and affect reactivity. Due to π-anisotropy, the Fe(IV)═O active site exhibits enhanced reactivity in the direction of the substrate cavity that proceeds through a π-channel that is controlled by perpendicular orientation of the substrate C-H bond relative to the halide-Fe(IV)═O plane. Also, the increased intrinsic reactivity of the SyrB2 intermediate relative to the ferryl model complex is correlated to a higher oxyl character of the Fe(IV)═O at the transition states resulting from the weaker ligand field of the halogenase. PMID:27021969

  8. Interdiffusion Behavior in Aluminide Coatings for Power Generation Applications

    SciTech Connect

    Zhang, Y.; Pint, B.A.; Haynes, J.A.; Cooley, K.M.; Wright, I.G.

    2003-04-22

    One of the critical issues for the application of iron aluminide coatings is the loss of Al from the coating into the Fe-base substrate alloys which do not contain aluminum. The interdiffusion behavior between chemical vapor deposited (CVD) aluminide coatings and ferritic and austenitic substrates is being studied for times up to 10,000h in the temperature range of 500-800 C. Coatings were synthesized using a laboratory-scale CVD reactor on representative commercial ferritic (Fe-9Cr-1Mo) and austenitic (type 304L stainless steel) alloys. The aluminide coatings on both alloys typically consisted of a relatively thin (20-25 {micro}m) Al-rich outer layer and a thicker (150- 250 {micro}m) inner layer with less Al. The composition profiles before and after interdiffusion testing were measured by electron probe microanalysis (EPMA). The decrease of the Al content at the coating surface was not significant after extended diffusion times ({le} 5000h) at temperatures {le} 700 C. More interdiffusion occurred at 800 C in coatings on both Fe-9Cr-1Mo and 304L alloys. Particularly, a two-phase microstructure was formed in the outer coating layer on 304L after interdiffusion of 2000h at 800 C. The interdiffusion behavior also was simulated using a computer model COSIM (Coating Oxidation and Substrate Interdiffusion Model), which was originally developed for MCrAlY overlay coatings by NASA. Reasonable agreement was observed between the simulated and experimental composition profiles although more work is needed to confirm assumptions made in the model.

  9. Iron

    MedlinePlus

    Iron is a mineral that our bodies need for many functions. For example, iron is part of hemoglobin, a protein which carries ... It helps our muscles store and use oxygen. Iron is also part of many other proteins and ...

  10. Weldability of Fe[sub 3]Al-type Aluminide

    SciTech Connect

    David, S.A.; Zacharia, T. )

    1993-05-01

    An investigation was carried out to determine the weldability of a series of Fe[sub 3]Al-type alloys. Autogenous welds were made on thin sheets of iron aluminide alloys using gas tungsten arc (GTA) and electron beam (EB) welding processes at different travel speeds and power levels. The results indicate that although these alloys can be successfully welded using the EB welding process, some compositions may hot crack during GTA welding. Boron and zirconium additions have been found to promote hot cracking in these alloys. Among the alloys investigated, Fe[sub 3]Al modified with chromium, niobium and carbon (FA-129) showed the most promise for good weldability. Hot-cracking severity of this alloy was further investigated using the Sigmajig test. The minimum threshold stress of 25 ksi measured is within the material range of other aluminides and some commercial stainless steels. Also, some of these alloys exhibited a tendency for cold cracking. This is related to severe hydrogen embrittlement associated with this class of alloys.

  11. Two phase titanium aluminide alloy

    DOEpatents

    Deevi, Seetharama C.; Liu, C. T.

    2001-01-01

    A two-phase titanic aluminide alloy having a lamellar microstructure with little intercolony structures. The alloy can include fine particles such as boride particles at colony boundaries and/or grain boundary equiaxed structures. The alloy can include alloying additions such as .ltoreq.10 at % W, Nb and/or Mo. The alloy can be free of Cr, V, Mn, Cu and/or Ni and can include, in atomic %, 45 to 55% Ti, 40 to 50% Al, 1 to 5% Nb, 0.3 to 2% W, up to 1% Mo and 0.1 to 0.3% B. In weight %, the alloy can include 57 to 60% Ti, 30 to 32% Al, 4 to 9% Nb, up to 2% Mo, 2 to 8% W and 0.02 to 0.08% B.

  12. Electroslag component casting. [Nickel aluminide

    SciTech Connect

    Sikka, V.K.

    1986-01-01

    This project is directed toward the development of electroslag-casting (ESC) technology for use in coal conversion components such as valve bodies, pump housings, and pipe fittings. The aim is also to develop a sufficient data base to permit electroslag casting to become an ASME Code-accepted process. It is also intended to transfer the ESC process technology to private industry. A total of 32 electroslag castings of 2.25Cr-1Mo, 9Cr-1Mo, type 316, and nickel aluminide were procured from four facilities for evaluation (Table 1). The most complex castings procured during this program were the valve bodies shown in Figure 2. The castings were subjected to various heat treatments (Table 2), checked for chemical composition uniformity from top to bottom, and subjected to macrostructural evaluation and mechanical properties testing. Results are discussed. 10 refs., 7 figs., 3 tabs.

  13. Nickel aluminides: Breaking into the marketplace

    SciTech Connect

    Krause, C.

    1995-12-31

    Nurtured by ORNL researchers for almost 15 years, nickel aluminides may have found their niche. ORNL`s modified nickel aluminides are receiving considerable attention by the heat-treating industry in the United States and may have arrived just in the nick of time to make some companies more competitive. Nickel aluminides are intermetallic materials that have long been considered potentially useful because, thanks to their ordered crystal structure, they are very strong and hard and melt only at very high temperatures. But they had a serious weakness: they were too brittle to be shaped into reliable components. Then, in 1982, ORNL researchers led by Chain T. Liu in the Metals and Ceramics Division found the secret recipe for producing a ductile nickel aluminide alloy: add trace amounts of a few alloying elements in the right proportion. It was like turning peanut brittle into taffy. Their most important discovery was that the addition of a small amount of boron (200 parts per million) to a nickel aluminide alloy (Ni{sub 3}Al) makes the alloy highly ductile at room temperature. To address the safety concerns of the alloy preparation industry, Vinod Sikka and Joseph Vought developed a new process in collaboration with Seetharama Deevi, who was on a 1-year sabbatical at ORNL from the Research Center at Philip Morris in Richmond, Virginia. The development is called the Exo-Melt process.

  14. Strength and toughness of composite materials based on nickel aluminide matrices

    NASA Technical Reports Server (NTRS)

    Rigney, J. D.; Khadkikar, P. S.; Lewandowski, J. J.; Vedula, K.

    1989-01-01

    Several nickel aluminide matrix composites were prepared using vacuum hot pressing techniques. The matrix compositions, based on Ni3Al, Ni3Al+B, and NiAl, were reinforced with 10 vol pct TiB2 particles. Both smooth- and notched-bend tests were conducted at room temperature on the monolithic as well as the reinforced materials in order to determine the effects of TiB2 reinforcement on both the smooth-bend and notched-bend properties. TiB2 additions were shown to improve the smooth-bend strengths regardless of the matrix composition, while notched-bend tests, conducted to provide estimates of fracture toughness, revealed somewhat lower values for the composites in comparison to the monolithic materials. Fractographic analyses and in situ fracture observations of the composites revealed that preferential fracture in regions of clustered TiB2 particles may significantly affect the measured toughnesses.

  15. Microstructures in rapidly solidified niobium aluminides

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G.; Locci, Ivan E.

    1988-01-01

    The microstructures of niobium aluminides produced by chill block melt spinning were compared to those of niobium aluminides produced by conventional casting. The rapidly solidified alloys were rapidly solidified by melt spinning in an argon atmosphere, and the melt-spun ribbons were examined by optical, X-ray, and TEM techniques. Microstructures were found to range from single-phase for Nb-75 at. pct Al (NbAl3) to two phase for Nb-46 at. pct Al (NbAl3 + Nb2Al). It was found that the melt spinning of Nb-aluminides produced finer grained microstructures than those produced in induction-melted ingots or in powders produced by the rotating electrode process. Ternary additions such as Cr, Ti, and Si tended to form intermetallic phases along the grain boundaries.

  16. Method for producing titanium aluminide weld rod

    DOEpatents

    Hansen, Jeffrey S.; Turner, Paul C.; Argetsinger, Edward R.

    1995-01-01

    A process for producing titanium aluminide weld rod comprising: attaching one end of a metal tube to a vacuum line; placing a means between said vacuum line and a junction of the metal tube to prevent powder from entering the vacuum line; inducing a vacuum within the tube; placing a mixture of titanium and aluminum powder in the tube and employing means to impact the powder in the tube to a filled tube; heating the tube in the vacuum at a temperature sufficient to initiate a high-temperature synthesis (SHS) reaction between the titanium and aluminum; and lowering the temperature to ambient temperature to obtain a intermetallic titanium aluminide alloy weld rod.

  17. IRON

    EPA Science Inventory

    The document surveys the effects of organic and inorganic iron that are relevant to humans and their environment. The biology and chemistry of iron are complex and only partially understood. Iron participates in oxidation reduction processes that not only affect its geochemical m...

  18. Production of reactive sintered nickel aluminide

    SciTech Connect

    1995-10-01

    This is the final report pertaining to the development of aluminides by reactive synthesis. Included in this report is an overview of results during the scope of this effort, details on specific task accomplishments, and a summary of customer evaluations. Opportunities for future work are also included at the end of this report.

  19. Castable nickel aluminide alloys for structural applications

    DOEpatents

    Liu, Chain T.

    1992-01-01

    The specification discloses nickel aluminide alloys which include as a component from about 0.5 to about 4 at. % of one or more of the elements selected from the group consisting of molybdenum or niobium to substantially improve the mechanical properties of the alloys in the cast condition.

  20. Large Scale Evaluation fo Nickel Aluminide Rolls

    SciTech Connect

    2005-09-01

    This completed project was a joint effort between Oak Ridge National Laboratory and Bethlehem Steel (now Mittal Steel) to demonstrate the effectiveness of using nickel aluminide intermetallic alloy rolls as part of an updated, energy-efficient, commercial annealing furnace system.

  1. Castable nickel aluminide alloys for structural applications

    DOEpatents

    Liu, C.T.

    1992-04-28

    The specification discloses nickel aluminide alloys which include as a component from about 0.5 to about 4 at. % of one or more of the elements selected from the group consisting of molybdenum or niobium to substantially improve the mechanical properties of the alloys in the cast condition. 4 figs.

  2. Metallography of gamma titanium aluminides

    SciTech Connect

    Baeslack, W.A. III . Dept. of Welding Engineering); McQuay, P.A.; Lee, D.S. ); Fletcher, E.D. )

    1993-12-01

    The microstructures of forged and heat treated Ti-48A1-2Nb-2Mn (at.%) and Ti-48A1-2Nb-2Cr (at.%) gamma titanium aluminides have been revealed by the application of selected metallographic preparation techniques and characterized using light microscopy. Examination of the as-polished specimen surface under polarized light was highly effective in revealing the equiaxed gamma grain structure and twins within the gamma grains, but it did not delineate alpha-two phase present at gamma grain boundaries or within a lamellar gamma/alpha-two constituent. Bright-field and differential-interference contrast light microscopy analyses of specimens chemically etched with Kroll's reagent (100mL H[sub 2]O + 4mL HNO[sub 3] + 2mL HF) were marginally effective in characterizing the equiaxed gamma grain structure and likewise did not reveal the alpha-two phase. Furthermore, the application of Kroll's reagent resulted in localized dissolution in the form of fine grooves or microcracks oriented in preferred directions within the equiaxed gamma grains. Under light microscopy, gamma grains that experienced this attack resembled the lamellar gamma/alpha-two constituent. The alpha-two phase was most clearly revealed using an etching solution comprised of 30mL lactic acid + 30mL HNO[sub 3] + 3mL HF, while the gamma grain and twin boundaries were most effectively revealed using an etching solution comprised of 30mL HCL + 10mL HNO[sub 3] + 5mL H[sub 2]O[sub 2] + 3mL HF. An etching solution of 25 mL H[sub 2]O + 50mL glycerol + 25mL HNO[sub 3] + 2mL HF was very effective in simultaneously revealing both the gamma and alpha-two phase morphologies.

  3. Determination of site-occupancies in aluminide intermetallics by ALCHEMI

    SciTech Connect

    Anderson, I.M.; Bentley, J.; Duncan, A.J.

    1995-04-01

    The site-distributions of Fe in four B2-ordered NiAl-based alloys with Fe concentrations of 10%, 2%, and 0.5% have been determined by ALCHEMI (atom-location by channeling-enhanced microanalysis). Site-distributions have been extracted with standard errors between {approximately} 1.5% (10% Fe concentration) and {approximately} 6% (0.5% Fe concentration). The results show that Fe has no strong site-preference in NiAl and tends to reside on the site of the stoichiometrically deficient host element. An improved ALCHEMI analysis procedure is outlined. The analysis explicitly addresses the phenomenon of ionization delocalization, which previously complicated the determination of site-distributions in aluminide intermetallics, leading to inaccurate and oftentimes nonphysical results. The improved ALCHEMI analysis also addresses the presence of anti-site defects. The data acquisition conditions have been optimized to minimize the sources of statistical and systematic error. This optimized procedure should be suitable for all analyses of B2-ordered alloys. Several analyses at different channeling orientations show that the extracted site-occupancies are robust as long as the data are acquired at orientations that are remote from any major pole of the crystal.

  4. Advances in gamma titanium aluminides and their manufacturing techniques

    NASA Astrophysics Data System (ADS)

    Kothari, Kunal; Radhakrishnan, Ramachandran; Wereley, Norman M.

    2012-11-01

    Gamma titanium aluminides display attractive properties for high temperature applications. For over a decade in the 1990s, the attractive properties of titanium aluminides were outweighed by difficulties encountered in processing and machining at room temperature. But advances in manufacturing technologies, deeper understanding of titanium aluminides microstructure, deformation mechanisms, and advances in micro-alloying, has led to the production of gamma titanium aluminide sheets. An in-depth review of key advances in gamma titanium aluminides is presented, including microstructure, deformation mechanisms, and alloy development. Traditional manufacturing techniques such as ingot metallurgy and investment casting are reviewed and advances via powder metallurgy based manufacturing techniques are discussed. Finally, manufacturing challenges facing gamma titanium aluminides, as well as avenues to overcome them, are discussed.

  5. Influence of high-strain rate and temperature on the mechanical behavior of Nl-, Fe-, and Ti- based aluminides

    SciTech Connect

    Gray, G.T. III

    1996-09-01

    The majority of the strength characterization studies on ordered intermetallics have concentrated on the assessment of strength and work-hardening at conventional strain rates. Although the influence of strain rate on the structure/property relationships of pure nickel, iron, and titanium and a variety of their alloys have been extensively studied, the effect of strain rate on the stress-strain response of Ni-, Fe-, and Ti-based aluminides remains poorly understood. Dynamic constitutive behavior is however relevant to high speed impact performance of these materials such as during foreign object damage in aerospace applications, high-rate forging, and localized deformation behavior during machining. The influence of strain rate, varied between 0.001 and 10{sup 4} s{sup -1}, and temperatures, between 77 & 800K, on the compressive mechanical behavior of Ni{sub 3}A1, NiAl, Fe{sub 3}Al, Fe-40Al-0.1B, Ti-24Al-11Nb, and Ti-48Al-2Cr-2Nb will be presented. In this paper the influence of strain rate on the anomalous temperature dependency of the flow stresses in these aluminides will be reviewed and compared between aluminides. The rate sensitivity and work hardening of each aluminide will be discussed as a function of strain rate and temperature and contrasted to each other and to the values typical for their respective disordered base metals. 66 refs., 16 figs., 2 tabs.

  6. Iron

    MedlinePlus

    ... organ failure, coma, convulsions, and death. Child-proof packaging and warning labels on iron supplements have greatly ... levodopa that the body absorbs, making it less effective. Levodopa, found in Sinemet® and Stalevo®, is used ...

  7. Welding of gamma titanium aluminide alloys

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

    An article made of a gamma titanium aluminide alloy is welded, as for example in the weld repair of surface cracks, by removing foreign matter from the area to be welded, first stress relieving the article, cooling the entire article to a welding temperature of from about 1000.degree. F. to about 1400.degree. F., welding a preselected region in an inert atmosphere at the welding temperature, and second stress relieving the article. Welding is preferably accomplished by striking an arc in the preselected region so as to locally melt the alloy in the preselected region, providing a filler metal having the same composition as the gamma titanium aluminide alloy of the article, and feeding the filler metal into the arc so that the filler metal is melted and fused with the article to form a weldment upon solidification.

  8. Environmental Studies on Titanium Aluminide Alloys

    NASA Technical Reports Server (NTRS)

    Brindley, William J.; Bartolotta, Paul A.; Smialek, James L.; Brady, Michael P.

    2005-01-01

    Titanium aluminides are attractive alternatives to superalloys in moderate temperature applications (600 to 850 C) by virtue of their high strength-to-density ratio (high specific strength). These alloys are also more ductile than competing intermetallic systems. However, most Ti-based alloys tend to degrade through interstitial embrittlement and rapid oxidation during exposure to elevated temperatures. Therefore, their environmental behavior must be thoroughly investigated before they can be developed further. The goals of titanium aluminide environmental studies at the NASA Lewis Research Center are twofold: characterize the degradation mechanisms for advanced structural alloys and determine what means are available to minimize degradation. The studies to date have covered the alpha 2 (Ti3Al), orthorhombic (Ti2AlNb), and gamma (TiAl) classes of alloys.

  9. Reactive spraying of nickel-aluminide coatings

    NASA Astrophysics Data System (ADS)

    Deevi, S. C.; Sikka, V. K.; Swindeman, C. J.; Seals, R. D.

    1997-09-01

    Reactive spraying of nickel aluminides was accomplished via reaction synthesis techniques in which nickel and aluminum powders were fed through a direct- current plasma torch onto carbon steel substrates. The as- sprayed coatings obtained by reactive spraying were characterized by x- ray diffraction and microscopic techniques. Reactive spraying of nickel and aluminum resulted in coatings consisting of Ni, Al, Ni 3Al, NiAl3, Ni5Al3, NiAl, and Al2O3, depending on the experimental conditions. Nickel aluminide phases observed in plasma spray depositions were compared with the phases obtained by combustion synthesis techniques, and the formation of phases in reactive spraying was attributed to the exothermic reaction between splats of aluminum and nickel. Primary and secondary reactions leading to the formation of nickel aluminides were also examined. The splat thickness and the reaction layer suppressed the formation of desired equilibrium phases such as Ni3Al and NiAl. As- sprayed coatings were annealed to enhance the diffusional reactions between the product phases and aluminum and nickel. Coatings obtained by reactive spraying of elemental powders were compared with as- sprayed and annealed coatings obtained with a bond coat material in which nickel was deposited onto aluminum particles.

  10. Shock-induced reaction synthesis (SRS) of nickel aluminides

    SciTech Connect

    Thadhani, N.N.; Work, S. , New Mexico Tech, Socorro, New Mexico 87801 ); Graham, R.A.; Hammetter, W.F. )

    1992-05-01

    Shock-induced chemical reactions between nickel and aluminum powders (mixed in Ni{sub 3}Al stoichiometry) are used for the synthesis of nickel aluminides. It is shown that the extent of shock-induced chemical reactions and the nature of the shock-synthesized products are influenced by the morphology of the starting powders. Irregular (flaky type) and fine morphologies of the powders undergo complete reactions in contrast to partial reactions occurring in coarse and uniform morphology powders under identical shock loading conditions. Furthermore, irregular morphology powders result in the formation of the equiatomic (B2 phase) NiAl compound while the Ni{sub 3}Al (L1{sub 2} phase) compound is the reaction product with coarse and regular morphology powders. Shock-induced reaction synthesis can be characterized as a bulk reaction process involving an intense mechanochemical'' mechanism. It is a process in which shock compression induces fluid-like plastic flow and mixing, and enhances the reactivity due to the introduction of defects and cleansing of particle surfaces, which strongly influence the synthesis process.

  11. Two-phase nickel aluminides

    NASA Technical Reports Server (NTRS)

    Khadkikar, P. S.; Vedula, K.; Shabel, B. S.

    1987-01-01

    The as-extruded microstructures of two alloys in the two phase field consisting of Ni3Al and NiAl in the Ni-Al phase diagram exhibit fibrous morphology and consist of Ll(2) Ni3Al and B2 NiAl. These as-extruded microstructures can be modified dramatically by suitable heat treatments. Martensite plus NiAl or martensite plus Ni3Al microstructures are obtained upon quenching from 1523 K. Aging of martensite at 873 K results in the recently identified phase Ni5Al, whereas aging at 1123 K reverts the microstructures to Ni3Al plus NiAl. The microstructures with predominantly martensite of Ni5Al3 phases are brittle in tension at room temperature. The latter microstructure does not deform plastically even in compression at room temperature. However, some promise of room temperature tensile ductility is indicated by the Ni3Al plus NiAl phase mixtures.

  12. High Temperature Oxidation Performance of Aluminide Coatings

    SciTech Connect

    Pint, Bruce A; Zhang, Ying; Haynes, James A; Wright, Ian G

    2004-01-01

    Aluminide coatings are of interest for many high temperature applications because of the possibility of improving the oxidation resistance of structural alloys by forming a protective external alumina scale. Steam and exhaust gas environments are of particular interest because alumina is less susceptible to the accelerated attack due to hydroxide formation observed for chromia- and silica-forming alloys and ceramics. For water vapor testing, one ferritic (Fe-9Cr-1Mo) and one austenitic alloy (304L) have been selected as substrate materials and CVD coatings have been used in order to have a well-controlled, high purity coating. It is anticipated that similar aluminide coatings could be made by a higher-volume, commercial process such as pack cementation. Previous work on this program has examined as-deposited coatings made by high and low Al activity CVD processes and the short-term performance of these coatings. The current work is focusing on the long term behavior in both diffusion tests16 and oxidation tests of the thicker, high Al activity coatings. For long-term coating durability, one area of concern has been the coefficient of thermal expansion (CTE) mismatch between coating and substrate. This difference could cause cracking or deformation that could reduce coating life. Corrosion testing using thermal cycling is of particular interest because of this potential problem and results are presented where a short exposure cycle (1h) severely degraded aluminide coatings on both types of substrates. To further study the potential role of aluminide coatings in fossil energy applications, several high creep strength Ni-base alloys were coated by CVD for testing in a high pressure (20atm) steam-CO{sub 2} environment for the ZEST (zero-emission steam turbine) program. Such alloys would be needed as structural and turbine materials in this concept. For Ni-base alloys, CVD produces a {approx}50{mu}m {beta}-NiAl outer layer with an underlying interdiffusion zone

  13. Hydrogen partitioning and transport in titanium aluminides

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.; Lee, Weon S.

    1993-01-01

    This report gives the final summary of the research work perfomed from March 1, 1990 to August 28, 1993. Brief descriptions of the research findings are given on the surface variation of Ti-14Al-21Nb as a function of temperature under ultrahigh vacuum conditions; titanium aluminides: surface composition effects as a function of temperature; Auger electron intensity variation in oxygen-charged silver; and segregation of sulfur on a titanium surface studied by Auger electron spectroscopy. Each description details one or more of the attached corresponding figures. Published journal documents are provided as appendices to give further detail.

  14. Titanium aluminide intermetallic alloys with improved wear resistance

    DOEpatents

    Qu, Jun; Lin, Hua-Tay; Blau, Peter J.; Sikka, Vinod K.

    2014-07-08

    The invention is directed to a method for producing a titanium aluminide intermetallic alloy composition having an improved wear resistance, the method comprising heating a titanium aluminide intermetallic alloy material in an oxygen-containing environment at a temperature and for a time sufficient to produce a top oxide layer and underlying oxygen-diffused layer, followed by removal of the top oxide layer such that the oxygen-diffused layer is exposed. The invention is also directed to the resulting oxygen-diffused titanium aluminide intermetallic alloy, as well as mechanical components or devices containing the improved alloy composition.

  15. CVD aluminiding process for producing a modified platinum aluminide bond coat for improved high temperature performance

    NASA Technical Reports Server (NTRS)

    Nagaraj, Bangalore A. (Inventor); Williams, Jeffrey L. (Inventor)

    2003-01-01

    A method of depositing by chemical vapor deposition a modified platinum aluminide diffusion coating onto a superalloy substrate comprising the steps of applying a layer of a platinum group metal to the superalloy substrate; passing an externally generated aluminum halide gas through an internal gas generator which is integral with a retort, the internal gas generator generating a modified halide gas; and co-depositing aluminum and modifier onto the superalloy substrate. In one form, the modified halide gas is hafnium chloride and the modifier is hafnium with the modified platinum aluminum bond coat comprising a single phase additive layer of platinum aluminide with at least about 0.5 percent hafnium by weight percent and about 1 to about 15 weight percent of hafnium in the boundary between a diffusion layer and the additive layer. The bond coat produced by this method is also claimed.

  16. An Oxidation-Resistant Coating Alloy for Gamma Titanium Aluminides

    NASA Technical Reports Server (NTRS)

    Brady, Michael P.; Smialek, James L.; Brindley, William J.

    1997-01-01

    Titanium aluminides based on the g-phase (TiAl) offer the potential for component weight savings of up to 50 percent over conventional superalloys in 600 to 850 C aerospace applications. Extensive development efforts over the past 10 years have led to the identification of "engineering" gamma-alloys, which offer a balance of room-temperature mechanical properties and high-temperature strength retention. The gamma class of titanium aluminides also offers oxidation and interstitial (oxygen and nitrogen) embrittlement resistance superior to that of the alpha(sub 2) (Ti3Al) and orthorhombic (Ti2AlNb) classes of titanium aluminides. However, environmental durability is still a concern, especially at temperatures above 750 to 800 C. Recent work at the NASA Lewis Research Center led to the development of an oxidation-resistant coating alloy that shows great promise for the protection of gamma titanium aluminides.

  17. Fundamental study about CO2 laser welding of titanium aluminide intermetallic compound

    NASA Astrophysics Data System (ADS)

    Kuwahara, Gaku; Yamaguchi, Shigeru; Nanri, Kenzo; Ootani, Masanori; Tetsuka, Masato; Seto, Sachio; Arai, Mikiya; Fujioka, Tomoo

    2000-11-01

    Titanium aluminide intermetallic compound is attracting attentions as heat-resistant and high-specific strength material in the next generation, especially, it is promising material in the field of aerospace components. Conventional machining process including welding, however, can be hardly applied due to its very low ductility. The objective of this study, as a first stage, is to find out paying attention to crack and hardness the fundamental good conditions of the bead-on-plate welding of TiAl intermetallic compound using CO2 laser irradiation. In the experiment, we used the casting gamma titanium aluminide contained iron, vanadium and boron with a thickness of 2mm. We carried out bead-on-plate laser welding in the titanium aluminide material in inert gas environment filled with argon. We measured fused depth, Vickers hardness, transverse crack numbers and so on as major parameters of welding speed from 1000 to 4600 mm/min and initial temperature of specimen from R.T. to 873 K with a beam spot size of 0.5 mm and an output power of 1.5 kW. In addition, the specimens were analyzed by Electron Probe X-ray Micro Analyzer, Energy Dispersive X-ray Spectroscopy and X-ray Diffractometry. As a result of experiments, transverse crack-free welding was achieved, when initial temperature was at 873 K. In every condition, the value of Vickers hardness of fused zone increased compared with base. We think the reason of it is an increase of (alpha) 2(Ti3Al) phase, which is caused by rapid cooling, taking in Oxygen, fine structure and so on.

  18. Spark plasma sintering of titanium aluminide intermetallics and its composites

    NASA Astrophysics Data System (ADS)

    Aldoshan, Abdelhakim Ahmed

    Titanium aluminide intermetallics are a distinct class of engineering materials having unique properties over conventional titanium alloys. gamma-TiAl compound possesses competitive physical and mechanical properties at elevated temperature applications compared to Ni-based superalloys. gamma-TiAl composite materials exhibit high melting point, low density, high strength and excellent corrosion resistance. Spark plasma sintering (SPS) is one of the powder metallurgy techniques where powder mixture undergoes simultaneous application of uniaxial pressure and pulsed direct current. Unlike other sintering techniques such as hot iso-static pressing and hot pressing, SPS compacts the materials in shorter time (< 10 min) with a lower temperature and leads to highly dense products. Reactive synthesis of titanium aluminide intermetallics is carried out using SPS. Reactive sintering takes place between liquid aluminum and solid titanium. In this work, reactive sintering through SPS was used to fabricate fully densified gamma-TiAl and titanium aluminide composites starting from elemental powders at different sintering temperatures. It was observed that sintering temperature played significant role in the densification of titanium aluminide composites. gamma-TiAl was the predominate phase at different temperatures. The effect of increasing sintering temperature on microhardness, microstructure, yield strength and wear behavior of titanium aluminide was studied. Addition of graphene nanoplatelets to titanium aluminide matrix resulted in change in microhardness. In Ti-Al-graphene composites, a noticeable decrease in coefficient of friction was observed due to the influence of self-lubrication caused by graphene.

  19. Development of weldable, corrosion-resistant iron-aluminide alloys

    SciTech Connect

    Maziasz, P.J.; Goodwin, G.M.; Wang, X.L.

    1995-05-01

    Corrosion-resistant, weldable FeAl alloys have been developed with improved high-temperature strength industrial applications. Previous processing difficulties with these alloys led to their evaluation as weld-overlay claddings on conventional structural steels to take advantage of their good properties now. Simplified and better processing methods for monolithic FeAl components are also currently being developed so that components for industrial testing can be made. Other avenues for producing FeAl coatings are currently being explored. Neutron scattering experiments residual stress distributions in the FeAl weld-overlay cladding began in FY 1993 and continued this year.

  20. Moisture-induced embrittlement of iron aluminides. Final report

    SciTech Connect

    Castagna, A.; Stoloff, N.S.

    1995-04-01

    FeAl alloys {ge}24 at. %Al are H embrittled by both H2 gas and water vapor. This examines effect of H embrittlement by H2 gas and moisture-bearing air on tensile properties and fatigue crack growth resistance of two ordered FeAl intermetallic alloys (28, 36 at. % Al) and one disordered Fe-Al alloy (16 at. % Al). Susceptibility to embrittlement varies with both Al content and ordered state. Tensile ductility of disordered low Al alloy is not affected by moisture-bearing air, and fatigue crack growth resistance is affected only slightly by moisture. However, the higher Al alloys are severely embrittled by moisture-bearing air. Oxidation of Al with concurrent release of H2 is responsible for embrittlement of Fe3Al alloys. It is likely that the smaller amount of Al available for the oxidation reaction in the 16at. % alloy precludes such embrittling reactions. In contrast, H2 is found to be embrittling to all alloys in both cyclic and monotonic tests. Fractography shows that H2 preferentially attacks cleavage planes in these alloys. Inherent fatigue crack growth resistance in an inert environment of the low Al disordered alloy is found to be much lower than that for the high Al alloys. Fatigue crack growth rate in an embrittling environment can be expressed as superposed mechanical fatigue and corrosion-fatigue components. Fatigue crack growth tests in inert and embrittling environments are used to isolate corrosion fatigue of the crack growth rate in Fe-28at. %Al. The corrosion-fatigue component displays a frequency dependence: At lower frequencies, more time is available for penetration of H ahead of the crack tip. H transport in the Fe-Al alloys occurs primarily by dislocation-assisted transport, which allows for penetration depths of 10-100x the distance that can be achieved by bulk diffusion. An equation is developed for the corrosion-fatigue component of crack growth rate which includes stress intensity range and frequency dependence.

  1. Development of iron-aluminide hot-gas filters

    SciTech Connect

    Tortorelli, P.F.; Wright, I.G.; Judkins, R.R.

    1996-06-01

    Removal of particles from hot synthesis gas produced by coal gasification is vital to the success of these systems. In Integrated [Coal] Gasification Combined Cycle systems, the synthesis gas is the fuel for gas turbines. To avoid damage to turbine components, it is necessary that particles be removed from the fuel gas prior to combustion and introduction into the turbine. Reliability and durability of the hot-gas filtering devices used to remove the particles is, of course, of special importance. Hot-gas filter materials include both ceramics and metals. Numerous considerations must be made in selecting materials for these filters. Constituents in the hot gases may potentially degrade the properties and performance of the filters to the point that they are ineffective in removing the particles. Very significant efforts have been made by DOE and others to develop effective hot-particle filters and, although improvements have been made, alternative materials and structures are still needed.

  2. The influence of composition on environmental embrittlement of iron aluminides

    SciTech Connect

    Alven, D.A.; Stoloff, N.S.

    1996-07-01

    The effects of water vapor in air and hydrogen gas on the tensile and fatigue crack growth behavior of Fe{sub 3}Al alloys have been studied at room temperature. Fe-28a% Al-5a% Cr alloys to which either Zr alone or Zr and C have been added and tested in controlled humidity air environments as well as in 1.3 atm hydrogen or oxygen gas and in vacuum. As with other Fe{sub 3}Al alloys, oxygen produces the lowest crack growth rates as well as the highest critical stress intensities and tensile ductility in each of the alloys tested. However, while Zr lowers crack growth rates in the Paris regime, there is no apparent beneficial effect on crack growth thresholds. Hydrogen gas also produces unusual results. While crack growth rates are very high in hydrogen in the Paris regime for all alloys, hydrogen only lowers the crack growth threshold relative to air in ternary Fe-28Al-5Cr; it does not lower the threshold in the Zr-containing alloys. It was found that decreased test frequency leads to increased crack growth rates in a Zr-containing alloy which points to a moisture-induced embrittlement mechanism responsible for the higher crack growth rates in air. Fracture path tends to be insensitive to environment for each alloy.

  3. Characterization of Field-Exposed Iron Aluminide Hot Gas Filters

    SciTech Connect

    McKamey, C.G.; McCleary, D.; Tortorelli, P.F.; Sawyer, J.; Lara-Curzio, E.; Judkins, R.R.

    2002-09-19

    The use of a power turbine fired with coal-derived synthesis gas will require some form of gas cleaning in order to protect turbine and downstream components from degradation by erosion, corrosion, or deposition. Hot-gas filtration is one form of cleaning that offers the ability to remove particles from the gases produced by gasification processes without having to substantially cool and, possibly, reheat them before their introduction into the turbine. This technology depends critically on materials durability and reliability, which have been the subject of study for a number of years (see, for example, Alvin 1997, Nieminen et al. 1996, Oakey et al. 1997, Quick and Weber 1995, Tortorelli, et al. 1999).

  4. Tensile properties of as-cast iron-aluminide alloys

    SciTech Connect

    Viswanathan, S.; McKamey, C.G.; Maziasz, P.J.; Sikka, V.K.

    1993-07-01

    Room-temperature tensile properties of as-cast Fe{sub 3}Al, Fe{sub 3}Al with chromium, and Fe{sub 3}Al-based FA-129 alloy are investigated. Tensile properties were obtained in the as-cast condition and after homogenization at 700, 900, and 1,200{degrees}C. Transmission electron microscopy (TEM) was used to characterize ordered phases, and optical metallography and scanning electron microscopy (SEM) were used to characterize the microstructure and fracture morphology. The results indicate that the low ductility of as-cast Fe{sub 3}Al-based alloys may be related to the relatively large grain size in the cast condition, the low dislocation density in as-cast samples, and the presence of the DO{sub 3} ordered phase. Homogenized samples of FA-129 alloy exhibited almost twice the ductility of the as-cast the as-cast and homogenized microstructures may provide a clue to the poor ductility in the as-cast state.

  5. Microstructure and Stresses in HVOF-Sprayed Iron Aluminide Coatings

    SciTech Connect

    Totemeier, Terry Craig; Wright, Richard Neil; Swank, William David

    2002-09-01

    The microstructure and state of stress present in Fe3Al coatings produced by high velocity oxygen fuel (HVOF) thermal spraying in air at varying particle velocities were characterized using metallography, curvature measurements, x-ray analysis, and microhardness measurements. Sound coatings were produced for all conditions. The microstructures of coatings prepared at higher velocities showed fewer unmelted particles and a greater extent of deformation. Residual stresses in the coatings were compressive and varied from nearly zero at the lowest velocity to approximately -450 MPa at the highest velocity. X-ray line broadening analyses revealed a corresponding increase in the extent of cold work present in the coating, which was also reflected in increased microhardness. Values of mean coefficient of thermal expansion obtained for as-sprayed coatings using x-ray analysis were significantly lower than those for powder and bulk alloy.

  6. The influence of composition on environmental embrittlement of iron aluminides

    SciTech Connect

    Alven, D.A.; Stoloff, N.S.

    1996-08-01

    The effects of water vapor in air and hydrogen gas on the tensile and fatigue crack growth behavior of Fe{sub 3}Al alloys has been studied at room temperature. Fe-28a%Al-5a%Cr alloys to which either Zr alone or Zr and C have been added have been tested in controlled humidity air environments as well as in 1.3 atm hydrogen or oxygen gas and in vacuum. As with other Fe{sub 3}Al alloys, oxygen produces the lowest crack growth rates as well as the highest critical stress intensities and tensile ductility in each of the alloys tested. However, while Zr lowers crack growth rates in the Paris regime, there is no apparent beneficial effect on crack growth thresholds. Hydrogen gas also produces unusual results. While crack growth rates are very high in hydrogen in the Paris regime for all alloys, hydrogen only lowers the crack growth threshold relative to air in ternary Fe-28Al-5Cr; it does not lower the threshold in the Zr-containing alloys. Fracture path tends to be transgranular in all alloys and environments. The results will be discussed in the light of possible effects of Zr on oxide formation.

  7. As-cast microstructure investigation of two iron aluminides

    NASA Astrophysics Data System (ADS)

    Geraldo Schön, Cláudio; Geoffroy Scuracchio, Bruno

    2006-08-01

    The as-cast microstructure of Fe-30Al-6Cr and Fe-30Al-10Ti high purity alloys was investigated using Electron Backscatter Diffraction. The first alloy is characterized by a highly textured columnar grain microstructure with large grains, while the second is characterized by an equiaxed grain microstructure with small grains and a random texture. These differences are discussed with regard to the higher reactivity of Ti compared with Cr, leading to nanometric nitride or oxide, which may act as sites for heterogeneous nucleation, and the ordered state of the BCC phase in equilibrium with the liquid during solidification and its effect upon dendrite growth kinetics.

  8. Investigation of moisture-induced embrittlement of iron aluminides

    SciTech Connect

    Castagna, A.; Stoloff, N.S.

    1993-04-15

    The effect in ambient air the tensile and fatigue behavior of an Fe{sub 3}Al, Cr type intermetallic alloy is examined as a function of test temperature. Hydrogen due to moisture in the air is found to be a major cause of embrittlement. Rates and mechanisms of observed embrittlement appear to be temperature dependent. In addition, the alloy was found to have no notch sensitivity.

  9. Tensile properties of as-cast iron-aluminide alloys

    SciTech Connect

    Viswanathan, S.; McKamey, C.G.; Maziasz, P.J.

    1995-01-01

    Room-temperature tensile properties of as-cast Fe{sub 3}Al-based FA-129 alloy were investigated. Tensile properties were obtained in the as-cast condition in air, oxygen, and water-vapor environments, and after homogenization at 700, 900, and 1200{degrees}C. Transmission electron microscopy (MM) was used to characterize ordered phases and dislocation structure, and optical metallography and scanning electron microscopy (SEM) were used to characterize the grain microstructure and fracture morphology. Tensile properties in the as-cast condition exhibited an environmental effect; tensile ductilities in oxygen atmosphere were greater than those obtained in laboratory air. Homogenized samples of FA-129 alloy exhibited almost twice the ductility found in the as-cast condition. Microstructural characterization of the homogenized samples and comparison of the as-cast and homogenized microstructures provided clues that helped to explain the poor ductility in the as-cast state.

  10. Tensile properties of as-cast iron-aluminide alloys

    SciTech Connect

    Viswanathan, S.: McKamey, C.G.; Maziasz, P.J.; Sikka, V.K.

    1993-07-01

    Room-temperature tensile properties of as-cast Fe{sub 3}Al, Fe{sub 3}Al with chromium, and Fe{sub 3}Al-based FA-129 alloy are investigated. Tensile properties were obtained in the as-cast condition and after homogenization at 700, 900, and 1200{degrees}C. Transmission electron microscopy (TEM) was used to characterize ordered phases, and optical metallography and scanning electron microscopy (SEM) were used to characterize the microstructure and fracture morphology. The results indicate that the low ductility of as-cast Fe{sub 3}Al-based alloys may be related to the relatively large grain size in the cast condition, the low dislocation density in as-cast samples, and the presence of the D0{sub 3} ordered phase. Homogenized samples of FA-129 alloy exhibited almost twice the ductility of the as-cast condition. Microstructural characterization of the homogenized samples and comparison of the as-cast and homogenized microstructures may provide a clue to the poor ductility in the as-cast state.

  11. Physical properties of intermetallic iron(2) vanadium aluminide

    NASA Astrophysics Data System (ADS)

    Feng, Ye

    2001-11-01

    Fe2VAl has recently been discovered to have a negative temperature coefficient of resistivity, moderately enhanced specific heat coefficient, and a large DOS at the Fermi level by photoemission. This triggered a round of heated research to understand the ground state of this material, both theoretically and experimentally. Here we report a comprehensive characterization of Fe2VAl. X-ray diffraction exhibited appreciable antisite disorder in all of our samples. FTIR spectroscopy measurements showed that the carrier density and scattering time had little sample-to-sample variation or temperature dependence for near-stoichiometric samples. FTIR and DC resistivity suggest that the transport properties of Fe2VAl are influenced by both localized and delocalized carriers, with the former primarily responsible for the negative temperature coefficient of resistivity. Magnetization measurements reveal that near-stoichiometric samples have superparamagnetic clusters with at least two sizes of moments. X-ray photoemission from Fe core level shows localized magnetic moments on site-exchanged Fe. We conclude that in Fe 2VAl, antisite disorder causes significant modification to the semi-metallic band structure proposed by LDA calculations. With antisite disorder considered, we are now able to explain most of the physical properties of Fe2VAl.

  12. Plasma electrolytic oxidation of Titanium Aluminides

    NASA Astrophysics Data System (ADS)

    Morgenstern, R.; Sieber, M.; Grund, T.; Lampke, T.; Wielage, B.

    2016-03-01

    Due to their outstanding specific mechanical and high-temperature properties, titanium aluminides exhibit a high potential for lightweight components exposed to high temperatures. However, their application is limited through their low wear resistance and the increasing high-temperature oxidation starting from about 750 °C. By the use of oxide ceramic coatings, these constraints can be set aside and the possible applications of titanium aluminides can be extended. The plasma electrolytic oxidation (PEO) represents a process for the generation of oxide ceramic conversion coatings with high thickness. The current work aims at the clarification of different electrolyte components’ influences on the oxide layer evolution on alloy TNM-B1 (Ti43.5Al4Nb1Mo0.1B) and the creation of compact and wear resistant coatings. Model experiments were applied using a ramp-wise increase of the anodic potential in order to show the influence of electrolyte components on the discharge initiation and the early stage of the oxide layer growth. The production of PEO layers with technically relevant thicknesses close to 100 μm was conducted in alkaline electrolytes with varying amounts of Na2SiO3·5H2O and K4P2O7 under symmetrically pulsed current conditions. Coating properties were evaluated with regard to morphology, chemical composition, hardness and wear resistance. The addition of phosphates and silicates leads to an increasing substrate passivation and the growth of compact oxide layers with higher thicknesses. Optimal electrolyte compositions for maximum coating hardness and thickness were identified by statistical analysis. Under these conditions, a homogeneous inner layer with low porosity can be achieved. The frictional wear behavior of the compact coating layer is superior to a hard anodized layer on aluminum.

  13. Characterization of segregation in nickel and titanium aluminides

    SciTech Connect

    Miller, M.K.; Larson, D.J.; Russell, K.F.

    1997-03-01

    Atom probe field ion microscopy has been used to characterize the distributions of microalloying additions in the microstructure of a variety of nickel and titanium aluminides. In Ni{sub 3}Al, boron additions were found to segregate to dislocations, low angle boundaries, stacking faults, antiphase boundaries, and grain boundaries. The boron and aluminum levels at grain boundaries were found to vary both from boundary to boundary and also along an individual boundary segment. In some cases, a boron-enriched film up to {approximately}3 nm thick was observed. In aluminum-enriched Ni{sub 3}Al, ultrafine clusters containing up to approximately 10 boron atoms were detected in the matrix. In contrast, the majority of the boron additions in NiAl was determined to be in the form of ultrafine MB{sub 2}-type precipitates. These precipitates offset the benefits of the boron segregation to the high angle grain boundaries. In molybdenum-doped NiAl, atom probe analyses indicated extremely low solubilities of the molybdenum and other trace impurities in the matrix and significant enrichments of molybdenum, nitrogen and silicon, boron, and iron at the grain boundaries. In boron-doped two phase {alpha}{sub 2} + {gamma} TiAl containing chromium, niobium, and tungsten, the boron level was found to be significantly depleted from the bulk level in both the {alpha}{sub 2} and {gamma} phases and a variety of coarse borides including TiB, TiB{sub 2} and a finer chromium-enriched (Ti, Cr){sub 2}B precipitate was observed. The tungsten and chromium were determined to partition preferentially to the {alpha}{sub 2} phase and also to segregated to the {alpha}{sub 2}-{gamma} and {gamma}-{gamma} interfaces. These results indicate that a significant proportion of the microalloying elements are consumed by the boride precipitates.

  14. Oxidation Resistant Ti-Al-Fe Diffusion Barrier for FeCrAlY Coatings on Titanium Aluminides

    NASA Technical Reports Server (NTRS)

    Brady, Michael P. (Inventor); Smialke, James L. (Inventor); Brindley, William J. (Inventor)

    1996-01-01

    A diffusion barrier to help protect titanium aluminide alloys, including the coated alloys of the TiAl gamma + Ti3Al (alpha2) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C is disclosed. The coating may comprise FeCrAlX alloys. The diffusion barrier comprises titanium, aluminum, and iron in the following approximate atomic percent: Ti-(50-55)Al-(9-20)Fe. This alloy is also suitable as an oxidative or structural coating for such substrates.

  15. Creep induced substructures in titanium aluminide

    NASA Astrophysics Data System (ADS)

    Cerreta, Ellen Kathleen

    Many investigations have examined the creep properties of titanium aluminides. Attempts to classify observed behaviors with existing models for high temperature deformation have been met with limited success. Several researchers have shown that an understanding of substructural evolution in the early stages of the creep curve may offer insight into the mechanisms, which control the rate of deformation. Creep deformation has been shown to include twinning, recrystallization, grain boundary sliding, ordinary and super dislocation activity, and faulting depending on the microstructure of the alloy and testing conditions. However, the environments that these alloys are likely to be exposed to are not similar to the test conditions in the literature. Furthermore the emphasis of much of the research into this group of alloys has been on the effects of microstructure particularly, the volume fraction of lamellar phase and ternary elemental additions. With all of these studies little information is available on the deformation behavior of the gamma phase. The alloys in these studies are mostly composed of the gamma phase and yet its creep behavior is not well understood. For this reason single phase binary gamma titanium aluminides were investigated in this study. To understand the effects of aluminum, interstitial oxygen content, and stress on creep, five alloys of varying Al concentrations and interstitial oxygen contents were deformed at temperatures ranging from 700--800°C and at stresses of 150, 200, and 250MPa. Full creep curves were developed under these conditions and phenomenological parameters for creep were calculated from these data. Additional tests were interrupted during primary and secondary creep at 760°C. Specimens from the interrupted tests as well as from the as-processed materials were examined optically and by TEM. Creep data and the microscopy were analyzed in concert to determine rate-controlling mechanisms for creep. Evolution of the substructure

  16. Human laminin B2 chain

    SciTech Connect

    Pikkarainen, T.; Kallunki, T.; Tryggvason, K.

    1988-05-15

    The complete amino acid sequence of the human laminin B2 chains has been determined by sequencing of cDNA clones. The six overlapping clones studied cover approximately 7.5 kilobases of which 5312 nucleotides were sequenced from the 5' end. The open reading frame codes for a 33-residue signal peptide and a 1576-residue B2 chain proper, which is 189 residues less than in the highly homologous B1 chain. Computer analysis revealed that the B2 chain consists of distinct domains that contain helical structures, cysteine-rich repeats, and globular regions, as does the B1 chain. However, domain ..cap alpha.. and domain ..beta.. of the B1 chain have no counterpart in B2, and the number of cysteine-rich repeats is 12, or 1 less than in the B1 chain. The degree of homology between the two chains is highest in the cysteine repeat-containing domains III and V where 40% of the residues match. However, in helical domains I/II only 16% of residues match. The results demonstrate that the B1 and B2 chains of laminin are highly homologous proteins that are probably the products of related genes.

  17. Diffusion coefficient of hydrogen in a cast gamma titanium aluminide

    SciTech Connect

    Sundaram, P.A.; Wessel, E.; Ennis, P.J.; Quadakkers, W.J.; Singheiser, L.

    1999-06-04

    Gamma titanium aluminides have the potential for high temperature applications because of their high specific strength and specific modulus. Their oxidation resistance is good, especially at intermediate temperatures and with suitable alloying additions, good oxidation resistance can be obtained up to 800 C. One critical area of application is in combustion engines in aero-space vehicles such as hypersonic airplanes and high speed civil transport airplanes. This entails the use of hydrogen as a fuel component and hence the effect of hydrogen on the mechanical properties of gamma titanium aluminides is of significant scientific and technological utility. The purpose of this short investigation is to use an electrochemical method under galvanostatic conditions to determine the diffusion coefficient of hydrogen in a cast gamma titanium aluminide, a typical technical alloy with potential application in gas turbines under creep conditions. This result will be then compared with that obtained by microhardness profiling of electrolytically hydrogen precharged material.

  18. Evaluation of a Gamma Titanium Aluminide for Hypersonic Structural Applications

    NASA Technical Reports Server (NTRS)

    Johnson, W. Steven; Weeks, Carrell E.

    2005-01-01

    Titanium matrix composites (TMCs) have been extensively evaluated for their potential to replace conventional superalloys in high temperature structural applications, with significant weight-savings while maintaining comparable mechanical properties. New gamma titanium aluminide alloys and an appropriate fiber could offer an improved TMC for use in intermediate temperature applications (400-800 C). The purpose of this investigation is the evaluation of a gamma titanium aluminide alloy with nominal composition Ti-46.5Al-4(Cr,Nb,Ta,B)at.% as a structural material in future aerospace transportation systems, where very light-weight structures are necessary to meet the goals of advanced aerospace programs.

  19. HIGH TEMPERATURE OXIDATION PERFORMANCE OF ALUMINIDE COATINGS

    SciTech Connect

    Pint, B.A.; Zhang, Y.; Haynes, J.A.; Wright, I.G.

    2003-04-22

    In order to determine the potential benefits and limitations of aluminide coatings, coatings made by chemical vapor deposition (CVD) on Fe- and Ni-base alloy substrates are being evaluated in various high-temperature environments. Testing of coatings on representative ferritic (Fe-9Cr-1Mo) and austenitic (type 304L stainless steel) alloys has found that high frequency thermal cycling (1h cycle time) can significantly degrade the coating. Based on comparison with similar specimens with no thermal cycling or a longer cycle time (100h), this degradation was not due to Al loss from the coating but most likely because of the thermal expansion mismatch between the coating and the substrate. Several coated Ni-base alloys were tested in a high pressure (20atm) steam-CO2 environment for the ZEST (zero-emission steam turbine) program. Coated specimens showed less mass loss than the uncoated specimens after 1000h at 900 C and preliminary characterization examined the post-test coating structure and extent of attack.

  20. Extended life aluminide fuel. Final report

    SciTech Connect

    Miller, L.G.; Beeston, J.M.

    1986-06-01

    As the price of fuel fabrication, shipment of both new and spent fuel, and fuel reprocessing continue to rise at a rapid rate, researchers look for alternate methods to keep reactor fuel costs within their limited funding. Extended fuel element lifetimes, without jeopardizing reactor safety, can reduce fuel costs by up to a factor of two. The Extended Life Aluminide (ELAF) program was started at the Idaho National Engineering Laboratory (INEL) as a joint project of the United States Department of Energy (DOE), the University of Missouri, and the Massachusetts Institute of Technology research reactors. Fuel plates of Advanced Test Reactor (ATR) type construction were fabricated at Atomics International and irradiated in the ATR at the INEL. Four fuel matrix compositions were tested (i.e., 50 vol% UAl/sub x/ cores for reference, and 40, 45 and 50 vol% UAl/sub 2/ cores). The 50 vol% UAl/sub 2/ cores contained up to 3 grams U-235 per cm/sup 3/ of core. Three plates of each composition were irradiated to peak burnup levels of 3 x 10/sup 21/ fission/cm/sup 3/ of core. The only observed damage was due to external corrosion at similar rates experienced by UAl/sub x/ fuel elements in test reactors.

  1. Iridium Aluminide Coats For Protection Against Ox idation

    NASA Technical Reports Server (NTRS)

    Kaplan, Richard B.; Tuffias, Robert H.; La Ferla, Raffaele; Jang, Qin

    1996-01-01

    Iridium aluminide coats investigated for use in protecting some metallic substrates against oxidation at high temperatures. Investigation prompted by need for cost-effective anti-oxidation coats for walls of combustion chambers in rocket engines. Also useful in special terrestrial applications like laboratory combustion chambers and some chemical-processing chambers.

  2. A study of the structure and properties of certain aluminides

    NASA Technical Reports Server (NTRS)

    Drits, M. Y.; Kadaner, E. S.; Vashchenko, A. A.

    1982-01-01

    Experimental data are presented on the structure and heat resistance of the aluminides ZrAl3, Fe2Al5 and Co2Al9, considering sp. wt., type of combination, and resistance to oxidation at high temperatures. Co2Al9 possesses a relatively high heat of formation, attributed to its high heat resistance characteristics.

  3. New phase formation in titanium aluminide during chemical etching

    SciTech Connect

    Takasaki, Akito; Ojima, Kozo; Taneda, Youji . Dept. of Mathematics and Physics)

    1994-05-01

    A chemical etching technique is widely used for metallographic observation. Because this technique is based on a local corrosion phenomenon on a sample, the etching mechanism, particularly for two-phase alloys, can be understood by electrochemical consideration. This paper describes formation of a new phase in a Ti-45Al (at.%) titanium aluminide during chemical etching, and the experimental results are discussed electrochemically.

  4. Alloy development of FeAl aluminide alloys for structural use in corrosive environments

    SciTech Connect

    Liu, C.T.; Sikka, V.K.; McKamey, C.G.

    1993-02-01

    Objectives include adequate ductilities ([ge]10%) at ambient temperature, high-temperature strength better than stainless steels (types 304 and 316), and fabricability and weldability by conventional techniques (gas tungsten arc). The alloys should be capable of being corrosion resistant in molten nitrate salts with rates lower than other iron-base structural alloys and coating materials (such as Fe-Cr-Al alloys). Such corrosion rates should be less than 0.3 mm per year. The FeAl aluminide containing 35.8 at. % Al was selected as base composition. Preliminary studies indicate that additions of B and Zr, increase the room-temperature ductility of FeAl. Further alloying with 0.2% Mo, and/or 5% Cr, improves the creep. Our preliminary alloying effort has led to identification of the following aluminide composition with promising properties: Fe - (35 [plus minus] 2)Al - (0.3 [plus minus] 0.2)Mo - (0.2 [plus minus] 0.15)Zr - (0.3 [plus minus] 0.2)B- up to 5Cr, at. %. However, this composition is likely to be modified in future work to improve the weldability of the alloy. The FeAl alloy FA-362 (Fe-35.8% Al-0.2% Mo-0.05% Zr-0.24% B) produced by hot extrusion at 900C showed a tensile ductility of more than 10% at room temperature and a creep rupture life longer than unalloyed FeAl by more than an order of magnitude at 593C at 138 MPa. Melting and processing of scaled-up heats of selected FeAl alloys are described. Forging, extruding, and hot-rolling processes for the scale-up heats are also described.

  5. Alloy development of FeAl aluminide alloys for structural use in corrosive environments

    SciTech Connect

    Liu, C.T.; Sikka, V.K.; McKamey, C.G.

    1993-02-01

    Objectives include adequate ductilities ({ge}10%) at ambient temperature, high-temperature strength better than stainless steels (types 304 and 316), and fabricability and weldability by conventional techniques (gas tungsten arc). The alloys should be capable of being corrosion resistant in molten nitrate salts with rates lower than other iron-base structural alloys and coating materials (such as Fe-Cr-Al alloys). Such corrosion rates should be less than 0.3 mm per year. The FeAl aluminide containing 35.8 at. % Al was selected as base composition. Preliminary studies indicate that additions of B and Zr, increase the room-temperature ductility of FeAl. Further alloying with 0.2% Mo, and/or 5% Cr, improves the creep. Our preliminary alloying effort has led to identification of the following aluminide composition with promising properties: Fe - (35 {plus_minus} 2)Al - (0.3 {plus_minus} 0.2)Mo - (0.2 {plus_minus} 0.15)Zr - (0.3 {plus_minus} 0.2)B- up to 5Cr, at. %. However, this composition is likely to be modified in future work to improve the weldability of the alloy. The FeAl alloy FA-362 (Fe-35.8% Al-0.2% Mo-0.05% Zr-0.24% B) produced by hot extrusion at 900C showed a tensile ductility of more than 10% at room temperature and a creep rupture life longer than unalloyed FeAl by more than an order of magnitude at 593C at 138 MPa. Melting and processing of scaled-up heats of selected FeAl alloys are described. Forging, extruding, and hot-rolling processes for the scale-up heats are also described.

  6. Superplasticity in near-gamma titanium aluminide

    NASA Astrophysics Data System (ADS)

    Lombard, Carl Michael

    The superplastic behavior of a near-gamma titanium aluminide (Ti-45.5Al-2Cr-2Nb) was determined under uniaxial tension in the as-rolled and two rolled-and-heat treated conditions (1177°C/4 hours or 1238°C/2 hours). Flow behavior, failure mode, microstructural evolution, cavitation rates, and the effects of these on superplastic behavior were the primary interests of this research. These relations were established via isothermal, constant strain rate tests conducted at 10-4--10-2 s -1 and temperatures between 900°C and 1200°C. The primary mechanism for hot deformation at 900--1000°C was identified as power law creep (n approximately 3) accompanied by dynamic recrystallization, as indicated by the activation energy values of approximately 300 kJ/mol. The process at 1100--1200°C was grain boundary sliding ( n approximately 2) accommodated by dynamic recrystallization. Significant microstructural changes were found. At 900°C and 1000°C, a small percentage of gamma and alpha2 grains of 3--5 mum diameter statically recrystallized during the test hold period. This was followed by dynamic recrystallization to a finer grain size of both the statically recrystallized grains and the unrecrystallized as-rolled material during tensile deformation. At 1100°C and 1200°C, the microstructural evolution process starting from the as-rolled condition was similar except that during testing there was (1) dynamic grain growth and/or dynamic recrystallization of statically recrystallized grains and (2) dynamic recrystallization of the unrecrystallized as-rolled material. Failure modes were established as predominantly cavitation/fracture controlled rather than localized thinning. Cavity growth was found to be largely plasticity controlled. Experimentally derived cavity growth rates were compared with various equations that predict cavity growth rates as a function of strain rate sensitivity. For all three initial microstructures, the optimum sheet forming temperature in the

  7. The Vaporization of B2O3(l) to B2O3(g) and B2O2(g)

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Myers, Dwight L.

    2011-01-01

    The vaporization of B2O3 in a reducing environment leads to formation of both B2O3(g) and B2O2(g). While formation of B2O3(g) is well understood, many questions about the formation of B2O2(g) remain. Previous studies using B(s) + B2O3(l) have led to inconsistent thermodynamic data. In this study, it was found that after heating, B(s) and B2O3(l) appear to separate and variations in contact area likely led to the inconsistent vapor pressures of B2O2(g). To circumvent this problem, an activity of boron is fixed with a two-phase mixture of FeB and Fe2B. Both second and third law enthalpies of formation were measured for B2O2(g) and B2O3(g). From these the enthalpies of formation at 298.15 K are calculated to be -479.9 +/- 41.5 kJ/mol for B2O2(g) and -833.4 +/- 13.1 kJ/mol for B2O3(g). Ab initio calculations to determine the enthalpies of formation of B2O2(g) and B2O3(g) were conducted using the W1BD composite method and show good agreement with the experimental values.

  8. Theoretical studies of aluminum and aluminide alloys using CALPHAD and first-principles approach

    NASA Astrophysics Data System (ADS)

    Jiang, Chao

    -temperature structural materials for aerospace applications due to their high melting temperature and good oxidation resistance. Many important properties of B2 aluminides are governed by the existences of point defects. In the present study, Special Quasirandom Structures (SQS's) are developed to model non-stoichiometric B2 compounds containing large concentrations of constitutional point defects. The SQS's are then applied to study B2 NiAl. The first-principles SQS results provide formation enthalpies, equilibrium lattice parameters and elastic constants of B2 NiAl which agree satisfactorily with the existing experimental data in the literature. It is unambiguously shown that, at T = 0K and zero pressure, Ni vacancies and antisite Ni atoms are the energetically favorable point defects in Al-rich and Ni-rich B2 NiAl, respectively. Remarkably, it is predicted that high defect concentrations can lead to structural instability of B2 NiAl, which explains well the martensitic transformation observed in this compound at high Ni concentrations.

  9. Ductility enhancement in NiAl (B2)-base alloys by microstructural control

    NASA Astrophysics Data System (ADS)

    Ishida, K.; Kainuma, R.; Ueno, N.; Nishizawa, T.

    1991-02-01

    An attempt to improve ductility of NiAl (B2)-base alloys has been made by the addition of alloying elements and the control of microstructure. It has been found that a small amount of fcc γ phase formed by the addition of Fe, Co, and Cr has a drastic effect not only on the hot workability but also on the tensile ductility at room temperature. The enhancement in ductility is mainly due to the modification of Β-phase grains by the coexistence of γ phase. The effect of alloying elements on the hot forming ability is strongly related to the phase equilibria and partition behavior among γ, γ' (L12 structure), and Β phases in the Ni-Al-X alloy systems. The ductility-enhancement method shows promise for expanding the practical application of nickel aluminide.

  10. Ductile aluminide alloys for high temperature applications

    SciTech Connect

    Liu, C.T.; Stiegler, J.O.

    1986-09-16

    An alloy is described consisting essentially of sufficient nickel and aluminum to form Ni/sub 3/A1, an amount of boron sufficient to promote ductility in the alloy and 0.3 to 1.5 atomic percent of an element selected from the group consisting of hafnium and zirconium. The alloy further including 6 to 12 atomic percent iron.

  11. Observations on the brittle to ductile transition temperatures of B2 nickel aluminides with and without zirconium

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Noebe, R. D.; Bowman, R.

    1989-01-01

    The effect of a zirconium addition (0.05 at. pct) to a stoichiometric NiAl alloy on the brittle-to-ductile transition temperature (BDTT) of this alloy was investigated. Constant velocity tensile tests were conducted to fracture between 300 and 1100 K under initial strain rate 0.00014/sec, and the true stress and true strain values were determined from plots of load vs time after subtracting the elastic strain. The inelastic strain was measured under a traveling microscope. Microstructural characterization of as-extruded and fractured specimens was carried out by SEM and TEM. It was found that, while the addition of 0.05 at. pct Zr strengthened the NiAl alloy, it increased its BDTT; this shift in the BDTT could not be attributed either to variations in grain size or to impurity contents. Little or no room-temperature ductility was observed for either alloy.

  12. Mechanisms of elevated-temperature deformation in the B2 aluminides NiAl and CoAl

    NASA Technical Reports Server (NTRS)

    Yaney, D. L.; Nix, W. D.

    1988-01-01

    A strain rate change technique, developed previously for distinguishing between pure-metal and alloy-type creep behavior, was used to study the elevated-temperature deformation behavior of the intermetallic compounds NiAl and CoAl. Tests on NiAl were conducted at temperatures between 1100 and 1300 K while tests on CoAl were performed at temperatures ranging from 1200 to 1400 K. NiAl exhibits pure-metal type behavior over the entire temperature range studied. CoAl, however, undergoes a transition from pure-metal to alloy-type deformation behavior as the temperature is decreased from 1400 to 1200 K. Slip appears to be inherently more difficult in CoAl than in NiAl, with lattice friction effects limiting the mobility of dislocations at a much higher tmeperature in CoAl than in NiAl. The superior strength of CoAl at elevated temperatures may, therefore, be related to a greater lattice friction strengthening effect in CoAl than in NiAl.

  13. Titanium Aluminide Applications in the High Speed Civil Transport

    NASA Technical Reports Server (NTRS)

    Bartolotta, Paul A.; Krause, David L.

    1999-01-01

    It is projected that within the next two decades, overseas air travel will increase to over 600,000 passengers per day. The High Speed Civil Transport (HSCT) is a second-generation supersonic commercial aircraft proposed to meet this demand. The expected fleet of 500 to 1500 aircraft is required to meet EPA environmental goals; the HSCT propulsion system requires advanced technologies to reduce exhaust and noise pollution. A part of the resultant strategy for noise attenuation is the use of an extremely large exhaust nozzle. In the nozzle, several critical components are fabricated from titanium aluminide: the divergent nap uses wrought gamma; the nozzle sidewall is a hybrid fabrication of both wrought gamma face sheet and cast gamma substructure. This paper describes the HSCT program and the use of titanium aluminide for its components.

  14. The Oxidation and Protection of Gamma Titanium Aluminides

    NASA Technical Reports Server (NTRS)

    Brady, Michael P.; Brindley, William J.; Smialek, James L.; Locci, Ivan E.

    1996-01-01

    The excellent density-specific properties of the gamma class of titanium aluminides make them attractive for intermediate-temperature (600-850 C) aerospace applications. The oxidation and embrittlement resistance of these alloys is superior to that of the alpha(sub 2) and orthorhombic classes of titanium aluminides. However, since gamma alloys form an intermixed Al2O3/TiO2 scale in air rather than the desired continuous Al2O3 scale, oxidation resistance is inadequate at the high end of this temperature range (i.e., greater than 750-800 C). For applications at such temperatures, an oxidation-resistant coating will be needed; however, a major drawback of the oxidation-resistant coatings currently available is severe degradation in fatigue life by the coating. A new class of oxidation-resistant coatings based in the Ti-Al-Cr system offers the potential for improved fatigue life.

  15. Electron Beam Welding to Join Gamma Titanium Aluminide Articles

    NASA Technical Reports Server (NTRS)

    Kelly, Thomas Joseph (Inventor)

    2008-01-01

    A method is provided for welding two gamma titanium aluminide articles together. The method includes preheating the two articles to a welding temperature of from about 1700 F to about 2100 F, thereafter electron beam welding the two articles together at the welding temperature and in a welding vacuum to form a welded structure, and thereafter annealing the welded structure at an annealing temperature of from about 1800 F to about 2200 F, to form a joined structure.

  16. Manufacturing techniques for titanium aluminide based alloys and metal matrix composites

    NASA Astrophysics Data System (ADS)

    Kothari, Kunal B.

    Dual phase titanium aluminides composed vastly of gamma phase (TiAl) with moderate amount of alpha2 phase (Ti3Al) have been considered for several high temperature aerospace and automobile applications. High specific strength coupled with good high temperature performance in the areas of creep and oxidation resistance makes titanium aluminides "materials of choice" for next generation propulsion systems. Titanium alumnides are primarily being considered as potential replacements for Ni-based superalloys in gas turbine engine components with aim of developing more efficient and leaner engines exhibiting high thrust-to-weight ratio. Thermo-mechanical treatments have shown to enhance the mechanical performance of titanium aluminides. Additionally, small additions of interstitial elements have shown further and significant improvement in the mechanical performance of titanium alumnide alloys. However, titanium aluminides lack considerably in room temperature ductility and as a result manufacturing processes of these aluminides have greatly suffered. Traditional ingot metallurgy and investment casting based methods to produce titanium aluminide parts in addition to being expensive, have also been unsuccessful in producing titanium aluminides with the desired mechanical properties. Hence, the manufacturing costs associated with these methods have completely outweighed the benefits offered by titanium aluminides. Over the last two decades, several powder metallurgy based manufacturing techniques have been studied to produce titanium aluminide parts. These techniques have been successful in producing titanium aluminide parts with a homogeneous and refined microstructure. These powder metallurgy techniques also hold the potential of significant cost reduction depending on the wide market acceptance of titanium aluminides. In the present study, a powder metallurgy based rapid consolidation technique has been used to produce near-net shape parts of titanium aluminides. Micron

  17. High temperature stability of aluminide-coated Inconel 617

    NASA Astrophysics Data System (ADS)

    Cho, Hyun; Lee, Byeong Woo

    2015-03-01

    Aluminum diffusion coatings were applied to the Inconel 617 by a pack cementation. The effect of coatings on the thermal stability and wear resistance of the Inconel alloy after heat-treatment under an air and a helium atmosphere at 1000°C, 48 h has been studied. The aluminide-coated Inconel specimens are prepared at 850°C and 1000°C for 1 h. An aluminiding layer indexed as AlxNi1-x (x = 0.4-0.6) was formed near the surface region and it played a role as a barrier layer against the surface diffusion of Cr. The thin Cr2O3 film formed in situ on the alloy surface is protective inhibiting further oxidation at moderate temperatures. As the temperature increases further, the thermal stability of the Inconel alloy is limited by the instability of the Cr2O3 scale. The aluminide-coated Inconel 617 samples showed the better performances, the enhanced thermal stability and improved wear resistance, most likely due to the barrier layer formation with the reduced amount of Cr2O3 scale formation.

  18. Deposition of aluminide and silicide based protective coatings on niobium

    NASA Astrophysics Data System (ADS)

    Majumdar, S.; Arya, A.; Sharma, I. G.; Suri, A. K.; Banerjee, S.

    2010-11-01

    We compare aluminide and alumino-silicide composite coatings on niobium using halide activated pack cementation (HAPC) technique for improving its oxidation resistance. The coated samples are characterized by SEM, EDS, EPMA and hardness measurements. We observe formation of NbAl3 in aluminide coating of Nb, though the alumino-silicide coating leads to formation primarily of NbSi2 in the inner layer and a ternary compound of Nb-Si-Al in the outer layer, as reported earlier (Majumdar et al. [11]). Formation of niobium silicide is preferred over niobium aluminide during alumino-silicide coating experiments, indicating Si is more strongly bonded to Nb than Al, although equivalent quantities of aluminium and silicon powders were used in the pack chemistry. We also employ first-principles density functional pseudopotential-based calculations to calculate the relative stability of these intermediate phases and the adhesion strength of the Al/Nb and Si/Nb interfaces. NbSi2 exhibits much stronger covalent character as compared to NbAl3. The ideal work of adhesion for the relaxed Al/Nb and Si/Nb interfaces are calculated to be 3226 mJ/m2 and 3545 mJ/m2, respectively, indicating stronger Nb-Si bonding across the interface.

  19. The effect of cobalt content in U-700 type alloys on degradation of aluminide coatings

    NASA Technical Reports Server (NTRS)

    Zaplatynsky, I.

    1985-01-01

    The influence of cobalt content in U-700 type alloys on the behavior of aluminide coatings is studied in burner rig cyclic oxidation tests at 1100C. It is determined that aluminide coatings on alloys with higher cobalt offer better oxidation protection than the same coatings on alloys containing less cobalt.

  20. Equilibrium defects and concentrations in nickel aluminide

    SciTech Connect

    Bai, B.; Collins, G.S.

    1999-07-01

    Perturbed angular correlation of gamma rays was applied to determine properties of equilibrium defects in B2 NiAl near the stoichiometric composition. Point defects were detected through quadrupole interactions they induce at In probe atoms on the Al sublattice. Well-resolved signals were observed for probe atoms having zero, one or two Ni-vacancies (V{sub Ni}) in the first neighbor shell. The fractions of probes in different sites are analyzed using a thermodynamic model to determine defect properties as follows. The equilibrium high-temperature defect is determined to be the triple defect combination (two V{sub Ni} and one Ni-antisite atom) through the variation of the vacancy concentration with composition and not, for example, the Schottky vacancy pair. The binding enthalpy of V{sub Ni} with a probe atom was determined to be in the range 0.18--0.24 eV. Site fractions were measured for three samples having 50.03, 50.14 and 50.91 at.% Ni at temperatures up to 1300 C. Vacancy concentrations were deduced from the site fractions and binding enthalpy. The equilibrium constant for formation of the triple defect was determined as a function of temperature from the vacancy concentrations and sample compositions. The formation enthalpy was found to be in the range 1.65--1.83 eV, depending on the binding enthalpy. The formation entropy was found to be {minus}3.2(4)k{sub B}. The large, negative value of the formation entropy probably cannot be explained in terms of a binding entropy, and the authors speculate that triple defects harden the B2 lattice, perhaps by disrupting the well-known 1/3 {l{underscore}angle}111{r{underscore}angle} soft mode lattice instability in B2 and bcc materials.

  1. Ruthenium Aluminides: Deformation Mechanisms and Substructure Development

    SciTech Connect

    Tresa M. Pollock

    2005-05-11

    Structural and functional materials that can operate in severe, high temperature environments are key to the operation of a wide range of energy generation systems. Because continued improvements in the energy efficiency of these systems is critical, the need for new materials with higher temperature capabilities is inevitable. Intermetallic compounds, with strong bonding and generally high melting points offer this possibility for a broad array of components such as coatings, electrode materials, actuators and/or structural elements. RuAl is a very unusual intermetallic compound among the large number of B2compounds that have been identified and investigated to date. This material has a very high melting temperature of 2050?C, low thermal expansion, high thermal conductivity and good corrosion resistance. Unlike most other high temperature B2 intermetallics, RuAl possesses good intrinsic deformability at low temperatures. In this program fundamental aspects of low and high temperature mechanical properties and deformation mechanisms in binary and higher order RuAl-based systems have been investigated. Alloying additions of interest included platinum, boron and niobium. Additionally, preliminary studies on high temperature oxidation behavior of these materials have been conducted.

  2. 32 CFR 806b.2 - Basic guidelines.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

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  3. 32 CFR 806b.2 - Basic guidelines.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 32 National Defense 6 2012-07-01 2012-07-01 false Basic guidelines. 806b.2 Section 806b.2 National Defense Department of Defense (Continued) DEPARTMENT OF THE AIR FORCE ADMINISTRATION PRIVACY ACT PROGRAM Overview of the Privacy Act Program § 806b.2 Basic guidelines. This part implements the Privacy Act of...

  4. 42 CFR 52b.2 - Definitions.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 1 2012-10-01 2012-10-01 false Definitions. 52b.2 Section 52b.2 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS NATIONAL INSTITUTES OF HEALTH CONSTRUCTION GRANTS § 52b.2 Definitions. As used in this part: Act means the Public Health Service Act,...

  5. 42 CFR 52b.2 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 1 2011-10-01 2011-10-01 false Definitions. 52b.2 Section 52b.2 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS NATIONAL INSTITUTES OF HEALTH CONSTRUCTION GRANTS § 52b.2 Definitions. As used in this part: Act means the Public Health Service Act,...

  6. 42 CFR 52b.2 - Definitions.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Definitions. 52b.2 Section 52b.2 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS NATIONAL INSTITUTES OF HEALTH CONSTRUCTION GRANTS § 52b.2 Definitions. As used in this part: Act means the Public Health Service Act,...

  7. 42 CFR 52b.2 - Definitions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 1 2013-10-01 2013-10-01 false Definitions. 52b.2 Section 52b.2 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS NATIONAL INSTITUTES OF HEALTH CONSTRUCTION GRANTS § 52b.2 Definitions. As used in this part: Act means the Public Health Service Act,...

  8. 42 CFR 52b.2 - Definitions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 1 2014-10-01 2014-10-01 false Definitions. 52b.2 Section 52b.2 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS NATIONAL INSTITUTES OF HEALTH CONSTRUCTION GRANTS § 52b.2 Definitions. As used in this part: Act means the Public Health Service Act,...

  9. 12 CFR 708b.2 - Definitions.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

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  10. 18 CFR 1b.2 - Scope.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

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