Enhancing Fatigue Life of Metal Parts Produced by High Speed Laser Powder Bed Fusion Through In‐Situ Surface Quality Improvement

The poor surface quality of metal parts produced by laser powder bed fusion (LPBF) limits their application in load-bearing components, as it promotes crack initiation under cyclic loadings. Consequently, the part quality relies on time-consuming surface finishing. This work explores a dual laser PBF strategy to simultaneously improve productivity, surface quality, and fatigue life of parts with inclined up-facing surfaces made from a novel tool steel. This is achieved by combining building using a high LT of 120 μm with in-situ quality enhancement through powder removal and laser remelting. A bending fatigue campaign was conducted to assess the performance of such treated samples produced with different LT’s (60 μm, hull-bulk 60/120 μm, 120 μm) compared to as-built and machined reference samples. Remelting consistently enhanced the fatigue life compared to the as-built reference samples by up to a factor of 36. The improvement was attributed to a reduced surface roughness and critical stress concentration factors, and gradually changing surface features with increased lateral dimension. This leads to a beneficial load distribution and fewer potential crack initiation points. Finally, remelting samples produced with a LT=120 μm achieved a fatigue life enhanced by a factor of 4 and reduced the production time by 30%, compared to the standard approach using LT=60 μm.