Research on process optimization and microstructure of CrCoNi medium-entropy alloy formed by laser metal deposition

Laser metal deposition (LMD) has shown its unique advantages in surface strengthening coatings and parts repair, and has brought revolutionary changes to manufacturing industry. However, unexpected shaping and internal defects can occur when an inappropriate combination of process parameters are used in the LMD process. These problems need to be solved to ensure satisfactory printed parts when using LMD. This study uses response surface methodology and multi-objective gray wolf optimization algorithm to obtain the process parameters of a single track with excellent forming quality. The results show that the process parameters have an important impact on the forming quality, and a single track with a good shape and microstructure are formed when the obtained optimal process parameters be used. In addition, the effects of laser energy densities on the microstructure and microhardness of printed parts were also studied by contrast experiments. The results indicate that the microstructure of the printed parts changes and the sub-grain size decreases with the decrease of the laser energy density, which ultimately leads to an increase in its microhardness. This work provides guidance for the selection of process parameters for surface enhancement coatings and parts repair by the LMD process.