In-process mitigation of residual stress in laser powder bed fusion: Effect of scanning strategies

Residual stress is a critical challenge in laser powder bed fusion (L-PBF) that can compromise the mechanical performance and dimensional accuracy of printed parts. This study investigated the role of scanning strategy on residual stress mitigation and temperature distribution in Ti-6Al-4V components fabricated by L-PBF. Six scanning strategies, comprising three continuous and three discontinuous patterns with rotation angles of 45° and 67° and unidirectional paths, were evaluated using a combined experimental–numerical approach. Experimental analyses included computed tomography (CT), surface roughness and hardness tests, and X-ray diffraction (XRD) residual stress measurement, while thermal and static finite element simulations were conducted to capture temperature evolution and stress distribution.

The results revealed that discontinuous strategies generally outperformed continuous ones in mitigating defects and residual stress. In particular, the discontinuous 67° rotation strategy exhibited the most favorable performance, achieving a high relative density of 99%, reduced peak temperatures, the lowest residual stress of 220 MPa, and a uniform stress field. CT analysis confirmed that continuous 45° rotation yielded the lowest density (97%) due to poor overlap and possible keyhole porosity, whereas discontinuous patterns reduced porosity and improved surface finish. Thermal simulations indicated that continuous strategies generated smoother but more heat-accumulated fields, leading to higher stresses, while discontinuous approaches facilitated thermal relaxation and stress homogenization.

This study demonstrated the importance of choosing scanning strategies for residual stress mitigation in L-PBF. The insights gained provide valuable guidance for improving the structural integrity and reliability of additively manufactured components.