Process parameter optimization and EBSD analysis of Ni60A-25% WC laser cladding

In this research work, the parameters of the preset powder feeding laser cladding process of Ni60A-25% tungsten carbide (WC) powder were optimized by using the response surface methodology of the central composite design. The dilution rate η and unit effective area ϕ of the laser cladding layer were considered as the response. Based on the factors and levels in the design matrix, the Ni60A-25% WC powder was fused on the 42CrMo alloy structural steel substrate with the laser cladding process to form a high-microhardness cladding layer. In this work, the microstructural characterization and crystal orientation analysis of the laser cladding layer obtained from the optimal process parameters were performed by using a Field Emission Scanning Electron Microscope (FE-SEM) and the Electron Backscatter Diffraction (EBSD) technique. The microhardness of the specimen processed with the optimal process parameters was evaluated using a Vickers microhardness tester. The results show the order of influence of four laser cladding process parameters on the dilution rate η and unit effective area ϕ. The developed mathematical models for the dilution and the unit effective area were validated. The errors between the experimentally obtained dilution rate η and unit effective area ϕ and predicted values were within acceptable limits. The EBSD analysis revealed that there was no meritocratic orientation of the substrate, while the laser cladding layer showed a pronounced meritocratic orientation. A large amount of martensite was produced within the coating after the laser cladding, resulting in a significant increase in the microhardness compared with the substrate. The microhardness test results were consistent with the microstructure morphology.