A comparative study of cyclic oxidized Ir aluminide and aluminized nickel base single crystal superalloy

A comparative study on microstructure, composition variation and phase distribution in an Ir-aluminide and an aluminized Ni-base single crystal superalloy, TMS-75 subjected to cyclic oxidation test at 1373 K is reported. The weight change as a function of number of oxidation cycles has demonstrated an improved oxidation resistance for iridium aluminide. While aluminized TMS-75 has an enrichment of aluminium to approximately 50 at.%, an addition of iridium increases the average aluminium concentration of the surface to approximately 70 at.% in the as aluminized condition. Unlike the aluminized TMS-75, the cyclic oxidized Ir aluminide reveals a precipitate free surface layer, followed by a significantly reduced precipitation of γ′-Ni3Al and TCP phases in the diffusion zone.