Oxidation characteristics of porous Ni-12 wt%Cr alloy at 1000 °C in air

Abstract

The oxidation kinetics of porous Ni-12 wt%Cr alloy with 23.7% porosity was investigated for 100 h at 1000 °C in air. The phases forming the oxide scale were determined by using X-ray diffractometry. The topography of the surface of the oxide scale and the microstructure of the cross-section of the oxide scale were investigated by utilizing optical and scanning electron microscopy and X-ray energy dispersive analysis. The oxidation rate was initially rapid and then it gradually decreased to lower values over a period of about 24 h until realizing the steady-state condition with linear rate constant of about 3.7 × 10−8 g/m2 sec. Double multilayered porous scale of NiO-Cr2O3 sublayers with internal precipitates of nickel spinel within the NiO layers was formed. The growth of the double multilayer scale was explained on the basis of inward migration of molecular oxygen. Keywords: High temperature oxidation, Ni-12 wt%Cr porous alloy, Linear kinetics, Double multilayered oxide scale, Inward molecular oxygen migration