Oxide pegs improved α-Al₂O₃ scale adhesion on aluminide coatings

This study aimed to improve the adhesion of α-Al₂O₃ scale on aluminide coatings. Precipitation heat treatment at 1100°C in an inert atmosphere led to the formation of HfO₂ pegs on the coating surface. These pegs penetrated deep into the coating, mechanically anchoring the α-Al₂O₃ scale and significantly improving its adhesion. The heat-treated coating exhibited reduced scale spallation and enhanced oxidation resistance. The formation of HfO₂ pegs was attributed to the surface oxidation of Hf segregated from the superalloy substrate to the coating surface. The surface segregation of Hf also contributed to a reduction in the growth rate of α-Al₂O₃ scale, thereby helping to prevent scale spallation.