High-temperature oxidation of a nickel base superalloy at different oxygen partial pressures

Abstract

A series of oxidation tests were conducted for a nickel base superalloy, as these materials are used at high temperature in aggressive conditions, thus the influence of oxygen on their degradation mechanisms must be known. The material was treated for up to 150 h at 900 and 1000°C in a furnace able to control and maintain atmospheres with different partial oxygen pressures. The oxidation rate of the material was determined by gravimetric means. In all cases, the rate of oxidation followed parabolic regimes that depended on the value of oxygen partial pressure. The oxide scale formed was characterised by X-ray diffraction and scanning electron microscopy; these analyses revealed that the oxide scale consisted of an outer TiO2 layer and inner Cr2O3 layer under all experimental conditions. Cross-section analyses indicated the development of internal oxidation and the presence of gamma-prime free zones.