Experimental Study of Residual Stresses in LPBF Using Different Island Scanning Strategies

Abstract

Residual stress remains a major limitation in laser powder bed fusion (LPBF), yet most prior work has focused on hatch patterns and rotation angles rather than the sequence in which individual islands or stripes are printed. This study addresses that gap by examining how four island-sequence strategies, two fixed sequences and two optimized sequences, influence residual stress in SS316L parts. Samples were fabricated using LPBF system, and top-surface stresses were measured at twelve locations using X-ray diffraction. While the top surface residual stress field contained both tensile and compressive stresses, the conventional successive and chessboard sequences exhibited higher local tensile extremes, consistent with localized heat accumulation and steep temperature gradient. In contrast, the optimized sequences distributed heat more evenly, reduced peak tensile stress, and produced smoother stress maps after baseplate removal. The results demonstrate that controlling the order of island activation is a powerful and underutilized method for mitigating residual stress, offering meaningful improvements.