Effect of residual stress on the spallation of the thermally-grown oxide formed on NiCoCrAlY coating

Abstract

In this study, the effect of residual stress in the NiCoCrAlY coating on the oxidation and spallation behavior of the thermally grown oxide (TGO) has been investigated. The surfaces of the NiCoCrAlY coatings were polished to a 0.1 μm finish before oxidation. The oxidation performed at 1150 °C shows that coating with compressive stress induced by grit blasting exhibits a higher oxidation rate, higher surface roughness and lower spallation resistance compared with coating with tensile stress. This is attributed to the significant interfacial rumpling induced by the relaxation of the compressive stress in the coating at the initial oxidation stage. The interfacial rumpling leads to the formation of the fast-growing spinel oxides and interfacial cracks, which are detrimental to the interfacial adherence.