Surface microstructure and high temperature oxidation resistance of thermal sprayed CoCrAlY coating irradiated by high current pulsed electron beam

摘要

A thermal sprayed CoCrAlY coating prepared by high-current pulsed electron beam (HCPEB) was investigated. Oxidation test of the coated specimenswas conducted at 1050 °C in air for 100 hrs. Themicrostructure evolution and surface morphology of the coatings were analyzed by means of X-ray diffraction (XRD), scanning electron microscope (SEM), and 3D laser scanning microscope, respectively. XRD result shows that Al_2O_3 and YAlO_3 phases were recorded in the irradiated coatings, but the Co-based oxides originally which existed in the initial samples disappeared. Microstructure observations reveal that the original coarse surface of the air plasma sprayed (APS) CoCrAlY coating was significantly changed after HCPEB irradiation, with a compact appearance of interconnected bulged nodules. Moreover, the grains on the irradiated coating were very fine and homogeneously dispersed on the surface. After high temperature oxidation test, a uniform and dense α-Al_2O_3 layer on "discontinuously" modified surface was obtained, and a quite negligible amount of Co and Cr was inflicted away fromthe layer. For theHCPEB irradiation of 30 pulses, the high temperature oxidation resistance of CoCrAlY coating was improved most dramatically.