High-temperature oxidation behaviour of CoCrNi medium-entropy alloy

The high-temperature oxidation behaviour of CoCrNi was investigated over different exposure times (6, 12, 24, and 48 h) at 900–1100 °C. The initial phase identification indicated that the tendency of oxide formation at 1100 °C was different after each exposure time. Microstructure observation demonstrated that Cr2O3 was mainly present at the interface of the oxide layer/base alloy, whereas CoCr2O4 and NiCr2O4 were identified near the outer oxide layer. The oxidation mechanism and the corresponding activation energy of CoCrNi were explained based on the slow diffusion of the Co, Cr, and Ni elements and the vacancy accumulation near the surface.