Oxidation behavior of glass-based composite thermal barrier coating on K417G superalloy with a NiCoCrAlY bond coat at 1000 °C

A novel thermal barrier coating (TBC) of glass-based composite with inclusions of Nickel, Y-PSZ, and corundum particles was prepared by sintering on K417G superalloy with a NiCoCrAlY bond-coat (BC). Aiming at prohibiting the interfacial reactions between BC and the composite top-coat (TC), pre-oxidation process of BC was carried out to form a continuous α-Al2O3 scale. However, a very thin but continuous layer of gahnite formed at the α-Al2O3 scale/TC interface as a result of their interfacial reactions during oxidation. Thus, the original unstable α-Al2O3/TC interface was replaced by the inactive gahnite/TC interface. Because of the extra protection of the gahnite interlayer as well as the barrier effect of the TC on oxygen permeation, the α-Al2O3 scale thickened very slowly, which made the composite TBC exhibit better oxidation resistance than the NiCoCrAlY coating at 1000 °C.