Abstract
The surface microstructure of air plasma spraying (APS) CoCrAlY coatings deposited on the Ni-based superalloy before and after high-current pulsed electron beam (HCPEB) irradiation was characterized by using scanning electron microscope (SEM) and transmission electron microscope (TEM). After HCPEB irradiation, the rough surface of APS-CoCrAlY was remelted and changed as ‘hill and valley’ aspect with a compact appearance. Besides, the thermally sprayed defects including rough surface, porosities, microcracks and etc were removed. In addition to the usual nano-grains, the HCPEB treatment has induced deformed structures containing Y-Al oxide particles within the remelted layer. Transient oxidation tests were carried out. As for the APS-CoCrAlY, a continuous thermally grown oxide (TGO) protective layer was not formed, and mixed oxides were instead formed on the surface due to its high roughness, the presence of structural defects and chemical heterogeneities. Comparatively, as for the HCPEB-CoCrAlY, a complete and dense α-Al2O3 layer was formed rapidly in the remelted surface due to the irradiated effects during the transient oxidation process, which guaranteed a protective effect on the bond coat for further oxidation behavior.
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