Research On The Temperature Field And The Heat Transfer Of Tiny Molten Pool During Selective Laser Melting Of Inconel 718

As an important technology in addictive manufacturing, Selective Laser Melting(SLM) has a broad application prospects in the future. As for Inconel 718 alloy, due to its good overall performance, the components made of Inconel 718 by SLM have been widely used in aerospace and defense. Since the temperature gradient of the Selective Laser Melting directly affects the size and stability of the molten pool, and the size and stability of the molten pool will determine the surface integrity, microstructure and mechanical properties of the components to a great extent, the study of temperature field and resulting molten pool behavior of the SLM process is necessary.This study establishes a full-parametric finite element model aimed for simulate the temperature field during selective laser melting of Inconel 718 alloy with the combination of ANSYS restart analysis technique and loop statement, considering the difference between the material properties of Inconel 718 alloy in solid condition and in powder condition, and then carries out SLM experiments to verify the heat source of the finite element model and verify the size of the molten pool. The simulation results are in good agreement with the experimental results.The results of finite element analysis show that, during selective laser melting of Inconel 718 alloy, the processed area will transfer heat to the unprocessed area, which will preheat the unprocessed area. This preheating plays an important role in the whole process. During the process of a single layer of powder, generally, with the laser scanning on different paths one by one, the overall maximum temperatures increases due to this preheating effect. While at the corner of the adjacent two paths, because of the large hatch spacing, there is no obvious preheating at the beginning point of the new path, therefore the temperature declines.The analysis of the molten pool shows that, the preheating effect that provided by processed area to unprocessed area makes the size of the molten pool increase gradually during processing a single layer of powder. In the same path, due to the relationship between the heat effect of preheating of the last path, the movement of the laser beam and the heat dissipation of the rear-end of the molten pool changes constantly, the length of the molten pool increases at first, then decreases, and finally tends to stable; and the width of the molten pool’s rear-end is greater than the width of the molten pool’s front-end at first, then it goes opposite.The temperature and the temperature gradient rise sharply in the area where the laser beam just goes through. The temperature of the molten pool’s center can reach to the order of magnitudes of 107(℃/m). Different process parameters such as hatch spacing, scan speed and laser’s power have obvious influence on the maximum temperature and temperature gradient of the molten pool and the depth and width of the molten pool.