Effects of laser processing parameters on thermal behavior and melting/solidification mechanism during selective laser melting of TiC/Inconel 718 composites

Abstract

A three-dimensional finite element model is proposed to study the effects of laser power and scan speed on the thermal behavior and melting/solidification mechanism during selective laser melting (SLM) of TiC/Inconel 718 powder system. The cooling time during powder delivery is taken into account to simulate the actual production process well. It shows obviously the existence of heat accumulation effect in SLM process and, the tailored set of cooling time of 10ms during powder delivery alleviates that effectively. The maximum temperature gradient in the molten pool slightly increases from 1.30×104°C/mm to 2.60×104°C/mm as the laser power is increased from 75W to 150W. However, it is negligibly sensitive to the variation of scan speed. There is a positive corresponding relationship between the maximum rate of temperature change and processing parameters. A low laser power (75W) or a high scan speed (300mm/s) is more energy efficient in Z-direction of the molten pool, giving rise to a deep-narrow cross section of the pool. Whereas, a high laser power (150W) or a low scan speed (50mm/s) causes a shallow-wide cross section of the molten pool, meaning it is more energy efficient in the Y-direction of the melt. The combination of a laser power of 125W and a scan speed of 100mm/s contributes to achieve a sound metallurgical bonding between the neighbor layers and tracks, due to the proper molten pool size (width: 109.3µm; length: 120.7µm; depth: 67.8µm). The SLM experiments on TiC/Inconel 718 powder system are performed to verify the reliability and accuracy of the physical model and, simulation results are proved to be correct.