Additive-manufactured equiaxed microstructural IN718 with high hardness and enhanced high temperature oxidation resistance

摘要

? 2022 Elsevier B.V.A unique Al-Si composite modified IN718 coating was obtained by plasma cladding. Its average hardness increased from 264.2HV0.2 to 625.3HV0.2 when compared to the original IN718, and its high temperature oxidation resistance was considerably enhanced. Separate addition of Al or Si cannot achieve the similar results. The microstructure of the coating changed from columnar to equiaxed after the composite addition of Al and Si, and the grain size was significantly refined. Through thermodynamic calculations, the oxidation mechanisms of coatings were investigated. The oxide layer of the IN718 coating is mainly composed of Cr2O3, while the Al-Si IN718 coating is mainly composed of Al2O3. The significant improvement in oxidation resistance was attributed to the lower diffusion rate of O in Al2O3 than in Cr2O3.