High-temperature performance of Pt-modified Ni-20Co-28Cr-10Al-0.5Y coating: Formation mechanism of Pt-rich overlayer and its effect on thermally grown oxide failure

A Pt-modified NiCoCrAlY coating was prepared on N5 via arc ion plating (AIP), Pt-electroplating, and subsequent vacuum annealing treatments. To perform a comparison between the properties of the modified and normal NiCoCrAlY coatings, the isothermal oxidation performances of the Pt-free and Pt-modified NiCoCrAlY coatings were evaluated at 1100 °C in static air. The results indicate that the Pt-rich overlayer on the Pt-modified NiCoCrAlY coatings exhibited superior oxidation resistance, and the adherent, thinner scale of α-Al2O3 inhibited the formation of detrimental (Ni, Co)(Cr, Al)2O4 spinel oxide. Furthermore, the addition of Pt effectively delayed the Al2O3 oxide phase transformation from θ to α in the early stage and markedly decreased the level of residual stress. The mechanism of forming the Pt-rich overlayer and its effect on thermally grown oxide (TGO) failure during high-temperature oxidation are discussed in detail, and the effect of Pt on improving the TGO growth, stress evolution, and spallation resistance are highlighted. •Pt-rich overlayer serves as Al-pumper, which inhibiting the formation of (Ni,Co)(Cr,Al)2O4 spinel.•The Pt-rich overlayer consisted of NiAl and Ni3Al without any PtAl2 phase were clearly characterized by TEM.•Pt delays θ-to-α Al2O3 transformation in initial oxidation stage.•Lesser growth stress and better adhesion of TGO are achieved on Pt-modified NiCoCrAlY coating.