Addition of vanadium to silicide master alloys for plasma-deposited coatings
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An investigation was carried out into the effect of vanadium on the structure and phase composition of some alloys of the Si-Ti-Cr system. The microstructure of resultant alloys is the same as that of similar vanadium-free materials. Vanadium is concentrated in the refractory phase, entering into the composition of a complex (Cr, Ti, V)Si2 disilicide. The remaining structural components are, as in the vanadium-free ternary alloys, free silicon and a eutectic. A study was made also of the effect of vanadium on the oxidation kinetics of alloys of the Si-Ti-Cr system exposed for 100 h to air at 1300‡C. Alloying with vanadium substantially slows down the rate of oxidation of these alloys and changes the law of oxidation from parabolic, characterizing the ternary alloys, to logarithmic for the vanadium-containing alloys. The 100-h rate of oxidation of an alloy of optimum composition at 1300‡C is 0.04 mg/cm2 · h. The optimum particle size of Si-Ti-Cr-V alloy powders intended for the application of coatings by gasothermic spray-deposition has been established.
KeywordsOxidation Particle Size Silicon Microstructure Vanadium
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