Finite element modeling of heat transfer in single and multilayered deposits of Ni-WC produced by the laser-based powder deposition process

Abstract

The localized high-energy input and high-cooling rate inherent in the laser-based powder deposition (LBPD) process yield deposits with superior mechanical and metallurgical properties. However, these characteristics induce thermal stresses within the deposited material that subsequently lead to cracks. This tendency is predominant in the LBPD of metal–ceramic composite materials such as nickel (Ni) and tungsten carbide (WC). In this study, the thermal behavior of single and multilayered compositionally graded Ni-WC composite material during LBPD is studied using an experimentally verified three-dimensional finite element model. The model incorporates both directional- and temperature-dependent material properties. The effect of the mass fraction of the reinforcement, laser power, scanning speed, powder flow rate, and preheating temperature on temperature, temperature gradient, cooling rate, and molten pool evolution are investigated. The distribution and dissolution of WC in Ni-WC deposits are analyzed in the light of the scanning electron microscope, energy-dispersive spectroscopy, and microhardness distribution. The dissolution of WC in the molten Ni varies based on the mass fractions of the Ni and WC and the prevailing thermal conditions such as molten pool temperature and cooling rate. Experimental and numerical results confirm that the desired composition gradient can be achieved in a multilayered Ni-WC composite material deposit by adjusting the laser power. The developed heat transfer analysis may be used to select the suitable process variables needed to achieve the desired properties in the LBPD of single and multilayered Ni-WC composite material.