Effect of Si and Cr content on the high temperature oxidation resistance of aluminide coatings on Ti obtained by microwave assisted SHS of metallic powders mixture

High temperature oxidation protection of alpha-titanium alloys is a fundamental aspect to be improved when applying such materials in demanding environments like in the case of high-performance exhaust systems. Protective Ni-Aluminide coatings produced by microwave assisted self-propagating high-temperature synthesis (SHS) of Ni and Al powder mixtures on Ti substrates are a promising route towards the improvement of hightemperature wear and oxidation resistance. As a matter of fact, the newly formed Ti-Ni-Al ternary compound at the Ti- interface (15 wt% of Al), results protective like pure NiAl, but only up to 750 °C. At 900 °C the lack of protective enough oxides does not hinder the growth of non-protective TiO2. In this study, the improvement of the 900°C oxidation resistance of the Ti-Ni-Al layer by powder metallurgy route is investigated, adding Si or Cr to the protective intermetallic coating and using microwave assisted SHS to minimize the extension of heat affected zones generated in the substrate when applying the coating.