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Previous work conducted by Mintek (Couperthwaite et al., 2013(Couperthwaite et al., , 2015 investigated the effect of precious metal additions on the structure, oxidation and corrosion properties of an Fe-40 at.% Al (FeAl) alloy. Initial work determined that additions of more than 0.5 at.% precious metal did not improve the oxidation and corrosion properties of the materials and in some cases even decreased the resistance to corrosion. Further work identified Pt and Ru as beneficial additions to the FeAl alloy. Four alloys were then produced by mechanical alloying and sintering (FeAl-0.2 at.% Pd, FeAl-0.2 at.% Ru, FeAl-0.5 at.% Ag, FeAl-0.5 at.% Pt). These alloys were all successfully produced by melting and casting and mechanical alloying sintering and it was found that the nonequilibrium processing greatly decreased the grain size of the materials compared to the ascast materials. It was found that the additions of Ru and Pt were still the most beneficial to the oxidation and corrosion properties, with Ru being considered the most beneficial.This report details the results from the initial spray testing work done with the FeAl-0.2 at.% Ru alloy powder produced by mechanical alloying. There are several options for powder coating onto substrates; thermalspray techniques, which include high-velocity oxy-fuel (HVOF) coating and plasma coating, or cold-spray (also known as supersonicspray) techniques. Cold-spray techniques have attracted a lot of interest lately and as a system is available at University of the Witwatersrand, it was decided to use cold spraying in the current work. This work was done to determine the effectiveness of cold-spray coating of these mechanically alloyed powders.The iron-aluminium system has attracted a large amount of research due to the fact that Fe-Al intermetallic compounds possess good mechanical properties, along with low density and low cost, as well as easy access to the raw materials (Ji et al., 2006;Montealegre et al., 2000). Arzhnikov et al. (2008) found that the Fe-Al alloys are promising, due to their good refractoriness, oxidation and corrosion resistance and good ductility at room temperature. In comparison to conventional alloys, Fe-Al alloys perform much better at higher temperatures, due to the stability of the Cold-spray coating of an Fe-40 at.% Al alloy with additions of ruthenium by R.A. Couperthwaite*, L.A. Cornish † ‡ and I.A. Mwamba* In previous work by the authors, it was established that additions of 0.2 at.% Ru to an Fe-40 at.% Al alloy improved the corrosion and oxidation resistance of the alloy. The alloy was produced by mechanical alloying and spark plasma sintering and the work showed that nonequilibrium processing was able to significantly refine the grain size of the material. The sintered material had a higher hardness than the as-cast material and the change in grain size did not significantly affect the oxidation and corrosion. In the present research, the mechanically alloyed powder was coated onto a mild steel substrate using cold-spray coating at ...

Platinum-based alloys are being developed with microstructures similar to nickel-based superalloys for potential high-temperature applications in aggressive environments. Since the chemistries of nickel and platinum are similar, Pt-based alloys can be made with gamma prime ~Pt 3 Al precipitates in a gamma (Pt) matrix. Currently, the Pt-Al-Cr-Ru system is one of the bases for developing Pt-based alloys, where Al allows the formation of the Pt 3 Al precipitate and also gives protection from the alumina scale formed, Cr provides oxidation resistance and stabilization for the L1 2 ~Pt 3 Al phase, and Ru provides solid solution strengthening in the (Pt) matrix.Four Pt-Al-Cr-Ru-V and two Pt-Al-Cr-Ru-V-Nb alloys were made, with compositions based on a quaternary alloy, ~Pt 82 :Al 12 :Cr 4 :Ru 2 , which had previously been identified as having optimum properties. Four of the ascast alloys had the targeted two-phase structure of ~Pt 3 Al and (Pt), and two were single-phase ~Pt 3 Al. Vanadium partitioned more to (Pt) than to ~Pt 3 Al. There was an improvement in hardness compared to the quaternary alloys. The best addition of V was ~15 at.%; higher additions resulted in brittle intermetallic phases of the Pt-V system. The effect of Nb could not be ascertained because of its high losses.