Effect of Surface Morphology of MCrAlY Bond Coats on the Isothermal Oxidation Behavior

Abstract

Abstract Surface morphology of MCrAlY bond coats is one of the factors that affect the oxidation behavior and the thermal stability of thermal barrier coatings. In the present study, the isothermal oxidation behavior of cold sprayed MCrAlY bond coat was investigated at three surface conditions: as-sprayed, polished and shot-peened conditions. The MCrAlY bond coat with sputters adhered weakly on the surface prepared by low-pressure plasma spraying was also employed. The above four types of surface conditions were employed to investigate the effect of the surface morphologies of MCrAlY (M=NiCo, Ni) bond coats on their oxidation behavior. MCrAlYs with the compositions of Ni20Cr10AlY and Ni23Co20Cr8.5Al5.0Ta0.6Y were employed for bond coat deposition. Cold-sprayed Ni20Cr10AlY exhibited a higher oxidation rate than that of the cold-sprayed Ni23Co20Cr8.5Al5.0Ta0.6Y bond coats. After 10 hrs oxidation, the TGO on the as-cold-sprayed bond coat surface was merely constituted by Al2O3, while the TGO on the bond coat surface attached with sputters was composed of Al2O3 and spinel. After 500 hrs oxidation, Cr2O3 and porous spinel appeared in the TGO on the two surfaces of as-cold-sprayed bond coat. The growth of Ni/Cr-oxides was attributed to the Al depletion. The content of spinel on cold-sprayed NiCrAlY decreased after shot-peening.