Effect of alumina dispersion on oxidation behavior as well as friction and wear behavior of HVOF-sprayed CoCrAlYTaCSi coating at elevated temperature up to 1000 °C

CoCrAlYTaCSi alloy coating and CoCrAlYTaCSi−Al₂O₃ composite coating were prepared on Inconel 718 alloy substrate by high velocity oxy-fuel (HVOF) spraying in order to avoid the failure of the hot parts made of the Ni-based alloy induced by oxidation and wear damage at elevated temperature of up to 1000 °C, with which the agglomerated powder of CoCrAlYTaCSi and Al₂O₃ was sintered to afford the to-be-sprayed CoCrAlYTaCSi−Al₂O₃ powder. The microstructure and phase composition of the as-sprayed coatings were analyzed by scanning electron microscopy, transmission electron microscopy and X-ray diffraction, and their mechanical properties were determined with a Vicker's hardness tester and a nano-indentation tester. Furthermore, the oxidation behavior of the coatings was evaluated by thermogravimetry and oxidation test in muffle furnace, and their friction and wear behavior under dry sliding against Si₃N₄ ball from room temperature to 1000 °C was evaluated with a high temperature tribometer. Results show that Ta, C and Si elements mainly exist in the forms of TaC and SiC nano-particles in as-sprayed coatings. The incorporation of Al₂O₃ dispersion results in a significant increase in the hardness, modulus, contact stiffness and wear resistance, but metallic Co and Cr slightly reduce the oxidation resistance of CoCrAlYTaCSi coating. Particularly, as-fabricated CoCrAlYTaCSi−Al₂O₃ coating exhibits much better wear resistance than CoCrAlYTaCSi coating and other MCrAlY/oxide metal-matrix coatings prepared by HVOF or other technologies, showing promising potential as a protective coating of Ni-alloy based hot parts