Microstructure and performance properties of 1200 °C-servicing gradiently aluminized NiCrAlYSi coating for single-crystal nickel-based superalloy

Enhancing service temperature of commercial MCrAlY series coatings to above 1100 °C becomes a new challenge. The aluminization seems be a possible solution. In this work, different Al contents aluminized NiCrAlYSi coatings were prepared. The microstructure, elemental distribution and cyclic oxidation performance of aluminized NiCrAlYSi coating with different Al contents have been investigated, using a substrate of Mo-rich single-crystal nickel-based superalloy. The Al content dependence of coating-air oxidation resistance and coating-substrate diffusion behavior is obtained at 1200 °C. These results demonstrate that this gradient aluminization is a cost-effective way to resolve service temperature enhancement. This also establishes a trade-off that adding Al content increases formation of dense Al₂O₃ scales with the sacrifice of surface smoothness.