Influence of Water Vapour on a Nickel-Based Alloy Oxidation

Abstract

Water vapour has little effect on the oxidation rate and scale composition of a nickel-based SY 625 alloy oxidized between 900 and 1100°C. At 900 and 1000°C, the outer scale is composed of Cr2O3 and a continuous NbNi4 - Ni3Mo subscale is found at the oxide/alloy interface. At 1100°C the scale is composed of an outer chromia scale and an internal CrNbO4 subscale. The oxide scale morphology differs between dry and wet conditions. Under dry conditions the oxide scale appears to be compact and chromia pegs are observed at the internal interface. Under wet conditions, porosities are observed inside the scale. At 1100°C some scale spallation is observed under dry and wet conditions.