Microstructure and element distribution characteristics of Y2O3 modulated WC reinforced coating on Invar alloys by laser cladding

As an essential material of aviation composite forming mold, Invar alloys will produce defects such as wear and crack during long-term service. In this paper, the rare earth oxide Y2O3 was added into the WC reinforced composite coating to improve the surface properties of Invar alloy. The microstructural evolution, element distribution and microhardness of composite coating were investigated by optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and Vickers hardness tests. The mean area and proportion of regular cellular crystals were quantitatively measured. The effect of Y2O3 on the distribution of the W element in the coating is revealed. Results indicate that the addition of Y2O3 significantly increases the thickness of the coating and improves the melting efficiency. Furthermore, cellular dendritic crystals tend to transform into regular cellular crystals with higher Y2O3 amounts. The proportion of regular cellular crystals reaches up to 30.0% when the mass fraction of Y2O3 is 5%. The W and Y elements tend to converge at crystals boundaries. Meanwhile, the microhardness gradient of the cladding layer (CL) decreases with Y2O3.