Coupled effects of powder characteristics and layer thickness on L-PBF process windows

Laser powder bed fusion (L-PBF) is still constrained in industrial applications by its relatively low manufacturing efficiency. Increasing the layer thickness is a direct approach to improving productivity; however, it often deteriorates forming quality and narrows the process window. However, under variable layer thickness conditions, how powder characteristics affect forming quality, process-window evolution, and optimized energy input is still not fully understood. Therefore, Ti-6Al-4V powders with different particle size distributions (PSD) and sphericities were used in this study to examine their coupled effects with layer thickness. A support vector machine (SVM) model was developed to optimize the process parameters. The results showed that the SVM model could accurately predict high-quality process windows, with a prediction accuracy of 95%. After optimization, the relative density approached or exceeded 99%, and the Ra was reduced by 17.9%–49.1% compared with that under the default parameters. Powders with finer particle size and higher sphericity exhibited a wider process window and better forming quality. Furthermore, under small and large layer thickness conditions, lower sphericity and finer particle size, respectively, corresponded to lower optimal energy density demand. With increasing layer thickness, the dominant laser–powder interaction shifted from particle-surface optical effects to volume absorption within the powder bed. These findings clarify the coupled effects of powder characteristics and layer thickness on forming quality and process window in L-PBF, and guide powder selection and parameter optimization for high-efficiency L-PBF forming.