Effect of cracking in diffusion aluminide coatings on their cyclic oxidation performance on Ti-based IMI-834 alloy

Diffusion aluminide coatings improve the high temperature oxidation resistance of Ti-alloys. This study evaluates the oxidation resistance of a Al₃Ti type aluminide coating and a Pt-aluminide coating on Ti-alloy IMI-834, at 650, 750 and 850 °C under cyclic oxidation conditions in air. Both coatings provide good oxidation resistance, however, the extent of through-thickness cracking in coating and localized oxidation degradation of substrate increases with thermal cycling. At high temperature of 850 °C, TiO₂ outgrowths emanate from these cracks, resulting in a prominent mud-crack pattern on the surface. The possible effect of such cracking on long-term oxidation properties of coatings has been discussed.