Influence of convection heat transfer coefficient on the predicted macroscopic temperature field in direct laser deposition of large-scale parts

In this work the influence of the heat transfer coefficient on the accuracy of the numerical prediction of the macroscopic temperature field in direct laser deposition of large-scale thin-walled structures is investigated in detail. It is shown that a temperature-independent constant heat transfer coefficient results in a considerable discrepancy in the prediction of the interpass temperature and the temperature distribution in the whole buildup. The numerical simulation revealed that the macroscopic temperature field in the buildup exhibits a pronounced sensitivity to the temperature dependence of the heat transfer coefficient. The film coefficient of the bottom surface of the substrate, which contacts the massive turntable of the direct laser deposition machine, has a negligible effect on the interpass temperature and mainly influences the temperature distribution near the substrate.