Cyclic oxidation behavior of an EB-PVD CoCrAlY coating influenced by substrate/coating interdiffusion

To reveal the influence of substrate/coating interdiffusion on the cyclic oxidation property of a metallic coating, cyclic oxidation behavior of an EB-PVD CoCrAlY coating on directionally solidified Ni-based superalloy DZ125 at 1 050 °C is investigated. The 40 μm thick CoCrAlY coating has a cyclic oxidation life of around 160 h, and the oxidation constant is 1.915×10 ^-7mg ⁴·cm ^-8·s ^-1. However, severe spallation of the oxides containing Co, Cr, Ni, Ta and Ti occurs with longer cyclic oxidation. The degradation in oxidation resistance for the coating is related to the depletion of Al due to the oxide spallation and interdiffusion. Severe interdiffusion between the coating and underlying substrate occurs at 1 050 °C. The composition of the substrate has an important effect on the thermal cycling lifetime of the coating. The influencing mechanism is discussed.