Microstructural aspects of plain aluminide and Pt-aluminide coatings on Ti-base alloy IMI-834

One of the major limitations of the near-α titanium alloys such as IMI-834 and IMI-829 that is currently restricting their use at high temperatures is their poor oxidation resistance. Several protective coatings including diffusion aluminide coatings are currently being examined to enhance the oxidation performance of these alloys in the temperature range of 600-750 °C. In the present study, various microstructural aspects of plain aluminide and Pt-aluminide coatings on Ti-base alloy IMI-834 have been studied. Plain aluminide coating shows a single layer consisting of only Al3Ti phase in the as-aluminized state. Pt-aluminide coating consists of three layers, namely an outer platinum-rich layer, an intermediate Al3Ti layer, and the inner interdiffusion layer. The above structure of Pt-aluminide coating on IMI-834 alloy is very similar to that reported on Ni-base superalloys. It has further been found in the present study that the structure of Pt-aluminide coating depends on its Pt and Al contents. The nature of such dependence is similar to that reported for Pt-aluminide coatings on Ni-base superalloy substrates.