Investigation of breakaway oxidation kinetics of nickel-base single crystal superalloys: Modeling and experiments

Varied oxidation behaviors at 1100 degrees C were investigated in six nickel-base single crystal superalloys. Thereinto, breakaway oxidation shows a feature of continuously increased oxidation rate, contrary to the typical parabolic theory. Predicated on parabolic oxide-layer growth and a constant spalling area fraction, we proposed a kinetics model to simulate the iterative scale growth and spallation process on the surface of superalloys. Our findings revealed that the breakaway oxidation behavior corresponds to accelerated weight-gain rate and is mechanistically attributed to continuous spallation of oxide layers. Based on our and previous research, a typical isothermal oxidation process can be defined as four stages: initial linear stage, parabolic stage, accelerated oxidation stage and dynamic-balance stage.