Influence of Re-Scan Strategy on Decreasing Pore Defects in Laser Powder Bed Fusion

Abstract

Laser powder bed fusion (LPBF) has attracted increasing attention owing to its advantages in fabricating complex-shaped structure in aerospace, medical, and automobile. However, pore defects in the built part may weaken its mechanical properties. Pore defects are typically classified into three types: lack of fusion (LOF), gas pores, and keyhole pores. In this study, we used in situ re-scan to decrease pore defects and then investigated the influence of re-scan strategy on decreasing pores. Two scan strategies were used in this study, including meander scanning strategy (M) and chessboard scanning strategy (C). The results have shown that M + M (the former for LPBF, the latter for re-scan) strategy mainly decreases gas pores and keyhole pores, whereas C + C re-scan strategy is good at eliminating LOF defects. More importantly, C + M re-scan strategy effectively decreases all the three types of pores. This study presents a distinct relationship between scanning strategy and pore defects, as well as an effective approach to decrease pore defects by laser re-scan with optimized scan strategy.

Keywords: Laser Powder Bed Fusion, Pore defect, scan strategy, laser re-scan, Relative density