Oxidation behavior of Pt-Ir modified aluminized coatings on Ni-base single crystal superalloy TMS-82+

The oxidation resistance of Pt-Ir modified aluminized coatings, prepared by magnetron sputtering, was investigated. Cyclic oxidation tests revealed that Pt-30 at%Ir and Pt-50 at%Ir modified aluminide coatings demonstrated a smaller mass change compared with Pt, Pt-80 at%Ir and Ir modified aluminide coatings. Cross-sectional analyses following cyclic oxidation tests showed that the TGO layer formed on the Pt modified aluminide coating surface is almost twice as thick as those on the Pt-30 at%Ir and Pt-50 at%Ir coatings. In addition, the Pt-30 at%Ir and Pt-50 at%Ir samples had a much smoother surface than the Pt modified coatings after cyclic oxidation, and the latter suffered from severe surface rumpling. However, when the Ir content exceeded 80 at% in Pt-Ir modified coatings, internal voids formed during cyclic oxidation. These results show that the addition of 30-50 at%Ir to Pt-modified aluminized coatings is most effective in enhancing oxidation resistance.