Two typical oxidation models on nickel-based superalloys under different initial surface roughness

Abstract

Two oxidation models were reported on DD6 and DZ125 superalloys with different initial surface roughness. The oxidation model I was characterized by one linear relationship in double-logarithmic mass-gain curves at high roughness of Ra 0.68 μm, but the model II had two linear stages at lower roughness. From oxide microstructure, only compact external Al2O3 layer developed in model I. A discrete inner Al2O3 and outer NiO/Cr2O3 layer were responsible for the mass-gain at the first stage of model II. The intermediate multiple layers mainly contributed to the second stage. The critical role of external Al2O3 layer on oxidation models and the formation mechanism of the layer under high surface roughness were discussed extensively.