Effect of Pre-Oxidation on High-Temperature Oxidation Behavior of Al-Si Coating on Nickel-Based Superalloy.

ABSTRACT

Under the condition of long-time high-temperature oxidation, oxidation in Al-Si coating will lead to degradation of the coating. To solve this problem, the Al-Si coating was treated before the oxidation experiment at different pre-oxidation temperatures and times. The structure, morphology and element distribution of the oxide film were characterized by XRD, SEM and EPMA, and the oxidation kinetics curves were drawn. The results show that the oxidation resistance of the pre-oxidized samples is improved in the process of constant temperature oxidation at 1000 °C. When the pre-oxidation temperature is set at 950 °C, the mass gain of the samples is the lowest, and the accelerated decomposition of Cr2O3 caused by high pre-oxidation temperature is avoided. After oxidation for 300 h, the oxide film on the surface is still continuous and dense without peeling. The samples pre-oxidized at 950 °C for 7 h show the best oxidation resistance in a 1000 °C constant temperature oxidation process, more α-Al2O3 oxides are generated on the coating surface and the element diffusion between the matrix and the coating caused by overly long oxidation time is avoided.