Evaluating Wagner Oxidation Criteria for Protective Al2O3 Scale Formation in Ni-Based Superalloys
J. W. X. Wo, Mark Hardy, H.J. Stone
Abstract
Abstract An assessment is made of the Wagner transition criteria for predicting the formation of a continuous Al 2 O 3 scale in Ni-based superalloys. Predictions are compared with data from an experimental Ni-based superalloy as well as commercial superalloys for which published data are available. The methodology was generally successful in predicting the transition temperature of the commercial superalloys but underpredicted the transition temperature of the experimental superalloy by approximately 50–100 °C. The difference in the transition temperature of the experimental superalloy to form a continuous Al 2 O 3 scale is primarily attributed to a complex oxide subscale that increased the internal volume fraction of oxide and led to reduced oxygen ingress. The sensitivity and limitations of the methodology are discussed, and recommendations are made to refine the methodology to facilitate the interpretation of oxidation behaviour in polycrystalline Ni-based superalloys.