Contribution of Si to the precipitation of '-phase in high Al content IN718 coatings and the phase transformation of -Al₂O₃ during high temperature oxidation

The Al-Si composite-modified IN718 alloy has not been studied in depth thus far. In this paper, an Al-Si composite-modified IN718 coating was successfully fabricated by plasma cladding, and it was found that Al-Si increases the composition supercooling of the alloy melt, increases the proportion of equiaxed crystals in the coating, and greatly enhances the hardness of the coating through the precipitation of a large area of the gamma'-phase. The changes in the properties of the gamma and gamma'-phases before and after Si doping were clarified by firstprinciples studies. High-temperature experiments show that the Al-Si IN718 coating has excellent resistance to high-temperature oxidation and that the addition of Si promotes the phase transformation of alpha-Al2O3 in the early stages of oxidation.