Microstructural characteristics of plasma-sprayed MCrAlY/Al2O3-13 wt.%TiO2 coating prepared by induction heating-assisted laser remelting

Abstract

Abstract The plasma-sprayed MCrAlY/Al2O3-13 wt.%TiO2 double-layer coating was treated using conventional laser remelting and induction heating-assisted laser remelting technologies to investigate the influence of laser remelting on the coating’s microstructure. The microstructural and interface characteristics of the different coatings were analyzed via scanning electron microscopy, energy dispersive spectroscopy, and x-ray diffractometry. Results showed that the Al2O3-13 wt.%TiO2 ceramic coating and MCrAlY bond coating of plasma-sprayed samples are typical lamellar structures with high porosity and that the nanostructural ceramic coating consists of fully melting and partially melting zones. A fine equiaxed grain remelting region is formed at the surface of the conventional laser-remelted ceramic coating. However, residual plasma-sprayed state is formed at the bottom of the ceramic coating. The microstructures at the bottom of the ceramic and bond coating are similar to the as-sprayed coating, but the compactness is somehow elevated. After induction heating-assisted laser remelting, the whole ceramic coating and bond coating are remelted, and compact structures are formed. Mechanical bonding occurs at the ceramic coating/bond coating interface and bond coating/substrate interface in the original as-sprayed coating. Through conventional laser remelting, mechanical bonding is the main bonding form on the specimen interface. Meanwhile, a certain degree of metallurgical bonding also exists. After induction heating-assisted laser remelting, the interface is completely transformed into metallurgical bonding. The conventional laser remelting can only strengthen the surface ceramic coating, but induction heating-assisted laser remelting can strengthen the surface ceramic layer and metal bond coating.