Effect of Co distribution on the oxidation behavior of aluminide coatings in Mo-rich Ni-based single-crystal superalloy

Three Co-modified coatings with different Co content distribution were prepared by electroless plating and vapor phase aluminizing (VPA) technique on Mo-rich Ni-based single-crystal superalloy. These coatings were subsequently subjected to prolonged static oxidation tests at 1000 °C for a duration of 500 h to reveal their oxidation behavior. The findings of this study indicated that the incorporation of Co within the coatings impeded the diffusion of Al and Mo within the infiltration layer and results in a slight decrease in the oxidation resistance of the coatings during the oxidation at 1000 °C. Additionally, Co accelerated the θ-to-α Al₂O₃ phase transformation at the initial oxidation stage. A comprehensive analysis was conducted to elucidate the oxidation kinetics and the underlying mechanisms associated with the diffusion behavior of the aluminide coatings in the presence of varying Co concentrations.