macro-scale thermal modeling for optimization of preheating strategies during laser powder bed fusion of inconel 738 parts

During additive manufacturing by laser powder bed fusion (L-PBF), a part undergoes rapid thermal cycling with significant heating and cooling rates. This thermal history leads to the initiation of microcracks that degrade the material properties. To mitigate this issue, various studies have explored the effect of preheating strategies. For instance, mesoscale models (molten pool scale) have predicted a reduction in cracking risk when the substrate (i.e. the most recently solidified layer) temperature is increased from 200 °C to 600 °C, with experimental data supporting these predictions. The aim of this study is to optimize the preheating strategy in L-PBF and thereby minimize the risk of hot cracking in Inconel 738 parts. To this end, a macroscale finite-element heat-flow model has been developed to simulate the part-scale temperature evolution during the preheating phase. Several parameters, such as the laser power, the thickness of the deposited powder layers, and the laser scanning time, can be tailored to faithfully replicate experimental conditions reported in the literature. The work of M. ASSAINTE et al. (this conference) was selected for model calibration. M. ASSAINTE et al. employed mobile thermocouples to measure temperature within the part during both fabrication and preheating stages. In the simulation, virtual mobile sensors are placed along the same trajectory as the experimental thermocouples, enabling point-by-point temperature comparison and optimal model calibration. Ultimately, a correlation between the build-front temperature and the microcrack density is established, enabling optimization of the preheating strategy during L-PBF fabrication.