Effect of Variable Specific Energy Laser Remelting on the Morphology, Microstructure, and Mechanical Properties of Ta/Ni-Based Composite Coatings

In this study, laser remelting was used to prepare Ta/Ni-based composite coatings using a combination of Ta-doping in a Ni-based powder. The effects of laser remelting specific energy and Ta-doping content on the surface morphology, phase composition, microstructure, bonding interface, microhardness, and wear resistance of the cladding layers were investigated. The unmelted powder particles on the coating surface disappeared after laser remelting. Laser remelting significantly decreased the grain size of the Ta/Ni-based composite coating, and the bright white microstructure of the doped Ta hindered crystal growth. With increase in the specific energy of the remelts, the internal porosity of the coating significantly decreased, overall grain size of the upper part of the composite coating gradually increased, central columnar crystal content gradually increased, overall crystal size of the lower part first decreased and then increased, and Ta and Ni diffused more fully at the bonding interface between the matrix and the coating, which decreased the difference in the chemical composition of the two sides of the bonding interface. The Ta/Ni-based composite remelted layers had significantly improved microhardness and wear resistance compared to before remelting, and both these parameters tended to increase and then decrease with increasing remelting specific energy.