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 CoCrAlYTaCSiAl2O3 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 CoCrAlYTaCSiAl2O3 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 CoCrAlYTaCSiAl2O3 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.