Microstructure and Mechanical Properties of Nickel-Based Coatings Prepared by Laser Additive Manufacturing on Water-Cooled Substrate

Abstract

In this study, the effects of water-cooled substrate on the microstructure and mechanical properties of laser additive manufactured nickel-based coatings were investigated by experimental and numerical simulations. The results showed that the water-cooled substrate decreased the size of columnar crystals and increased the number as well as the length of secondary dendrite crystals at the bottom of the nickel-based coatings. There was also a noticeable increase in the size of equiaxed grains and the quantity of the solid solution in the middle of the coatings. The hardness value of the coating increased at the water flow rate of 4.76 m/s and 5.95 m/s and and finally decreased at and 6.25 m/s. A finite element model was established by ABAQUS software to numerically simulate the temperature field of the laser-cladded nickel-based coating with the water-cooled substrate. The results revealed significant differences in the temperature distribution of the coatings with different velocities. As the water velocity increased, the peak temperature at the center of the coating's molten pool gradually decreased. In addition, the cooling rate of the specimens increased with the application of the water cooling, leading to a more concentrated temperature distribution near the laser heat source.

Keywords: Laser additive manufacturing, Ni45 alloy powder, water-cooled substrate, Temperature field