Microstructure and Properties of CoCrAlYTa-10%Al2O3 Coating Prepared by HVOF Thermal Spraying

CoCrAlYTa-10%Al2O3 coating was deposited on Q235 steel substrate by high velocity oxygen fuel (HVOF) thermal spraying method. Microstructure, phase compositions and micro-hardness of the coating were analyzed by using optical microscope (OM), scanning electron microscope (SEM) equipped with energy dispersive spectroscope (EDS), X-ray diffractometer (XRD) and micro-hardness tester. The results show that the coating had dense and uniform microstructure with the porosity of 0.44%, and it was composed of light gray Co-based solid solution, dark gray Cr-based solid solution, white ball Ta-rich solid solution and black Al2O3 phase. The formation of Al2O3 phase was attributed to the original composition of the feedstock powders and the oxidation of element aluminum in CoCrAlYTa alloy. The micro-hardness of the coating was 580~630 HV0.3, about 3 times of that of Q235 steel substrate (200 HV0.3), indicating that the coating had good mechanical properties.