Iron Aluminide Powder Research Articles

Дослідження механічних властивостей і зносостійкості плазмових покриттів на основі інтерметаліду Fe-Al

Studies of the mechanical characteristics and abrasive resistance of FeAl-based plasma sprayed coatings are presented. Coatings were obtained by plasma spraying method using iron aluminide powders of Fe3Al, Fe-AlMg and Fe-TiAl systems. The powders were prepared by mechanochemical synthesis. The mechanical characteristics (hardness and elastic modulus) of the coatings were determined by microindentation method. It has been found that the hardness of the coatings is in the range of 2.9…5.4 GPa, the elastic modulus is in the range of 80…100 GPa. It is shown that the gas-abrasive resistance of all tested coatings at room temperature exceeds the wear resistance of St3 steel 1.4…4.3 times; when dry abrasive/rubber wheel testing the resistance of the coatings exceeds the resistance of St3 2.1…3.8 times. The resistance of Fe3Al, Fe-AlMg and Fe-TiAl coatings is higher 2.2…3.1 times than resistance of St3 steel under conditions of gas-abrasive wear at a temperature of 550 °C; the resistance of Fe3Al and Fe-TiAl coatings under the same conditions exceeds the resistance of heat-resistant steels 1.2…1.5 times. In all cases Fe3Al coating has the highest wear resistance because of low porosity and low content of brittle phases in the coating. An assessment of the relationship between the mechanical properties of coatings and wear resistance showed that the wear resistance of coatings increases with an increasing of their elastic modulus. Based on the results of studies the possibility of using FeAl-based coatings for the protection and hardening of parts and constructions operating under conditions of abrasive wear at temperatures range from 20 to 550 °C is shown.

Comparison of microstructure and adhesion strength of plasma, flame and high velocity oxy-fuel sprayed coatings from an iron aluminide powder

In this study an iron aluminide powder with the feedstock powder composition of Fe-28Al-5Cr and a particle size of 45μm to 75μm was thermally sprayed onto AlSi10Mg and AlSi12CuNiMg substrates by flame spray (FS), atmospheric plasma spray (APS) and high velocity oxy-fuel spray (HVOF) processes. The combination of the utilized materials is due to lightweight design and is, therefore, different from most of the previous studies, which dealt with the application of iron aluminide coatings onto steels. Coatings were analyzed in terms of microstructural investigations using SEM coupled with EDX measurements in the as sprayed condition and after a heat treatment of 100h at 500°C in argon atmosphere. Phase analysis was performed by XRD measurements in the as sprayed and heat treated condition. The FS and APS coatings contained different amounts of a bcc solid solution α(Fe, Al, Cr), FeO, Fe3O4, FeAl2O4 and γ-Al2O3. It was found that the FeO rearranged to bcc Fe and Fe3O4 during this heat treatment. The HVOF coating retained 90% of feedstock powder material and a low fraction of oxide and Al-depleted phases. The microhardness was determined to be 277HV0.4 (FS), 394HV0.4 (APS) and 479HV0.4 (HVOF) which was associated to the different constituting phases. Adhesion strength was measured using the tensile adhesion test (TAT) and the achieved adhesion was 13.8MPa (APS), 30.3MPa (FS) and exceeded 58MPa (HVOF).

Evaluation of Iron Aluminide-Fly Ash Nanocomposite Prepared by Attritor Milling and Equal Channel Angular Extrusion Consolidation

An experimental investigation was conducted to evaluate the crystallite size and microhardness of mixtures iron aluminide (Fe 3 Al) powder and Class C fly ash in different volume percentages, subjected to attritor milling and consolidation using Equal Channel Angular Extrusion (ECAE) process. Design if experiments was employed to select the lowest size of fly ash to be mixed with pre-milled iron aluminide powder. The results indicate that crystallite sizes n the low nano-range are obtained in all iron aluminide-fly ash compacts, qualifying the compact as a nanocomposite. The microhardness of the nanocomposite is lower than that of the nano-iron aluminide indicating the possibility of porosity being developed in fly ash during processing.

Structural evolution of Fe–50 at.% Al powders during mechanical alloying and subsequent annealing processes

Iron aluminides, despite having desirable properties like excellent corrosion resistance, present low room-temperature ductility and low strength at high temperatures. Mechanical alloying as a capable process to synthesize nanocrystalline materials is under consideration to modify these drawbacks. In this study, the microstructure of iron aluminide powders synthesized by mechanical alloying and subsequent annealing was investigated. Elemental Fe and Al powders with the same atomic percent were milled in a planetary ball mill for 15 min to 100 h. The powder milled for 80 h was annealed at temperatures of 300, 500 and 700 °C for 1 h. The alloyed powders were disordered Fe(Al) solid solutions which were transformed to FeAl intermetallic after annealing. The effect of the milling time and annealing treatment on structural parameters, such as crystallite size, lattice parameter and lattice strain was evaluated by X-ray diffraction. Typically, these values were 15 nm, 2.92 Å and 3.1% for the disordered Fe(Al) solid solution milled for 80 h and were 38.5 nm, 2.896 Å and 1.2% for the FeAl intermetallic annealed at 700 °C, respectively.

Ordering and disordering processes in MA and MM intermetallic iron aluminide powders

The formation of the FeAl intermetallic compound has been investigated by annealing a mechanically milled powder and a mechanically cryoalloyed powder. First, the morphological transformations that result from both milling processes were analysed, giving special emphasis to the cryoalloyed powder; the evolution of continuous cold welding and fracturing during milling was assessed by means of scanning electron microscopy (SEM). The lattice parameter changes of both powders were then evaluated as a function of milling time using profile fitting and Rietveld analysis of the XRD data. The powder thermal stability was also examined by differential scanning calorimetry (DSC) and the detected transformations were discussed according to the structural changes observed in X-ray temperature-dependent measurements. Furthermore, Mossbauer data has been used to compare the different atom rearrangements, from that of an ideal B2 structure and a typical bcc-Fe type to a disordered A2-solid solution and their temperature-induced ordering processes.

Sintering Behavior of Iron Aluminide Powders

Sintering Behavior of Iron Aluminide Powders

Production of iron aluminide powder by self propagating high temperature synthesis : T.L. Talako et al. (Powder Metallurgy Research Inst., Minsk, Belarus)

Production of iron aluminide powder by self propagating high temperature synthesis : T.L. Talako et al. (Powder Metallurgy Research Inst., Minsk, Belarus)

Tape casting of iron aluminide powders

Tape casting of iron aluminide powders

Microstructure and Oxidation Behavior of Low Pressure Plasma Sprayed Iron Aluminides.

Microstructure and oxidation behavior of plasma sprayed iron aluminide have been investigated focusing on the spraying conditions of atmosphere and pressure. Iron aluminide powder for spraying was prepared by ball milling of turnings fabricated from an Fe-40at%Al ingot. Microstructure of laminated layers including cavities was observed in all samples and particles with a size of about 100 μm were observed only in the sample sprayed in 50 Torr Ar atmosphere. Chemical analysis revealed an amount of aluminium loss and oxygen pick-up in samples sprayed in air, while X-ray diffraction analysis exhibited only the iron aluminide spectra without the second phase. The intensity of superlattice spectra of aluminide was strong in the samples sprayed in Ar compared with in air. Change of mass gain in oxidation testing was small in the sample sprayed in 50 Torr Ar, which is equivalent to as-cast bulk sample, while large in other samples. SEM observation revealed the evolution of iron oxides in the samples sprayed in air, which was not observed in the sample sprayed in Ar. The mechanism for superior resistance to oxidation in the sample sprayed in 50 Torr Ar is attributed to infusible particles deposition, which inherited the intrinsic oxidation resistant property of iron aluminides.

Micro-mechanical testing of injection moulded iron aluminide powder compacts: J.C.Foley et al. (Ames Laboratory, USA.)

Micro-mechanical testing of injection moulded iron aluminide powder compacts: J.C.Foley et al. (Ames Laboratory, USA.)

Titanium aluminide composites from combustion reaction processing: H.Mabuchi et al. (Osaka Prefecture University, Sakai, Japan.) J. Jpn Soc. Powder Powder Metall., vol 44, no 6, 1997, 535–541 (In English.)

Composites of an intermetallic alloy matrix (such as iron aluminide) and ceramic particle reinforcement (such as alumina) have potential for high-temperature structural applications requiring excellent oxidation resistance. In contrast to conventional processing methods (e.g. mechanical alloying), in situ processing techniques can be inexpensive and can also lead to unique microstructures, such as very fine dispersions of the reinforcements or interconnecting phases. The feasibility of processing Fe–Al alloy/Al2O3 composites by an in situ displacement reaction between Fe–40at.%Al and the iron oxide Fe2O3 was investigated and the results are presented in this paper. Specimens were prepared by hot pressing of the powder mixtures at 1300°C. The final volume fractions of Al2O3 were determined by the initial ratio of Fe–40%Al to Fe2O3 and composites with 7 and 20 vol.% Al2O3 were investigated in this study. Compression creep tests performed at 700°C showed that composites with 7 and 20 vol.% Al2O3 had higher compressive strengths than monolithic iron aluminide (Fe–28at.%Al). In particular, the compressive strength of the composite with 20 vol.% Al2O3 was three times that of the monolithic iron aluminide. Further increases in compressive strength, as well as significant improvements in bend and fracture strength, were obtained when the particle size of the starting Fe–40%Al powders was less than 10 μm. Improved fracture toughness with the smaller Fe–40%Al powders could be attributed to the ductile failure of fine iron aluminide ligaments. The effect of Cr and Ti additions of up to 8 at.% on the strength of the interface between the iron aluminide and alumina phases was also investigated. The compressive strength of a composite processed with <10-μm diameter iron aluminide powders and 8 at.% Cr was the highest of all the specimens. However, within the range of compositions studied in this investigation, only slight improvements in the mechanical properties could be obtained with these alloying additions.

Tape casting as a fabrication process for iron aluminide (FeAl) thin sheets

The conversion of iron aluminide powder into a slurry followed by tape casting into a green sheet was investigated. Casting parameters affecting green sheet properties were studied. Application of thermo-mechanical processing including sintering, cold rolling, annealing and heat treating resulted in sheets with a fine-grain structure at essentially 100% of theoretical density. The various microstructures developed throughout the process are described, along with tensile property measurements on the fully dense product. Differences in property with sheets made by other processes are explained, and it is demonstrated that tape casting is a viable method of making thin gauge sheets of iron aluminide with a wide range of compositions.

Iron aluminide–Al 2O 3 composites by in situ displacement reactions: processing and mechanical properties

Composites of an intermetallic alloy matrix (such as iron aluminide) and ceramic particle reinforcement (such as alumina) have potential for high-temperature structural applications requiring excellent oxidation resistance. In contrast to conventional processing methods (e.g. mechanical alloying), in situ processing techniques can be inexpensive and can also lead to unique microstructures, such as very fine dispersions of the reinforcements or interconnecting phases. The feasibility of processing Fe–Al alloy/Al 2O 3 composites by an in situ displacement reaction between Fe–40at.%Al and the iron oxide Fe 2O 3 was investigated and the results are presented in this paper. Specimens were prepared by hot pressing of the powder mixtures at 1300°C. The final volume fractions of Al 2O 3 were determined by the initial ratio of Fe–40%Al to Fe 2O 3 and composites with 7 and 20 vol.% Al 2O 3 were investigated in this study. Compression creep tests performed at 700°C showed that composites with 7 and 20 vol.% Al 2O 3 had higher compressive strengths than monolithic iron aluminide (Fe–28at.%Al). In particular, the compressive strength of the composite with 20 vol.% Al 2O 3 was three times that of the monolithic iron aluminide. Further increases in compressive strength, as well as significant improvements in bend and fracture strength, were obtained when the particle size of the starting Fe–40%Al powders was less than 10 μm. Improved fracture toughness with the smaller Fe–40%Al powders could be attributed to the ductile failure of fine iron aluminide ligaments. The effect of Cr and Ti additions of up to 8 at.% on the strength of the interface between the iron aluminide and alumina phases was also investigated. The compressive strength of a composite processed with <10-μm diameter iron aluminide powders and 8 at.% Cr was the highest of all the specimens. However, within the range of compositions studied in this investigation, only slight improvements in the mechanical properties could be obtained with these alloying additions.

Spray deposition of an iron aluminide

High velocity oxyfuel (HVOF) spray forming of an iron aluminide [Fe–12.5 Al–2.93 Ni–0.02 B (wt%), containing 300 p.p.m. oxygen], followed by heat treatment for 24 h at 500°C, 18 h at 600°C and 20 min at 800°C, and multipass hot rolling at 800°C has been studied. Three different thicknesses (0.43, 0.93 and 1.33 mm) of sprayed deposit were produced by spraying for different times (approximately 10, 20 and 30 min). The spray-deposited layers exhibited some oxide and some porosity. This porosity was reduced by heat treatment. The as deposited layer had a high degree of B2 order, and a B2 antiphase domain size of 4.5 nm. On hot rolling this material to a reduction of 38%, it was found to be more susceptible to edge cracking than similar material processed by an ingot–extrusion–hot rolling route. In heat treatment, the aluminide-sprayed layer formed a non-protective Fe2O3 oxide, rather than the usual Al2O3 that forms on the binary alloy. This is attributable to the Ni content of the iron aluminide powder employed. © 1998 Kluwer Academic Publishers

Compaction and sintering of iron aluminide powders : L.Co, R.M.German. (Pennsylvania State University, USA.)

Compaction and sintering of iron aluminide powders : L.Co, R.M.German. (Pennsylvania State University, USA.)

Powder Processing of Fe3Al-Based Iron-Aluminide Alloys

ABSTRACTThe production, characterization, and consolidation of Fe3Al-based iron-aluminide powders are described. The consolidated powders were fabricated into sheet. The sheet was tensile tested from room temperature to 800°C and creep tested in the temperature range of 450 to 704°C. Mechanical properties were compared for nitrogen and argon atomized powders. Mechanical properties were also compared for argon atomized powders of Fe3Al alloys containing 2 and 5% Cr.