Communication Dans Un Congrès Année : 2026

Leading role of the subsurface microstructure over the surface topography on the fatigue strength of stress-relieved L-PBF 316L parts

Résumé

The Laser Powder Bed Fusion (L-PBF) process allows to manufacture parts with both a complex geometry and a high mechanical performance. The as-built and net-shape L-PBF parts - i.e. without any heat nor surface treatment, have tensile residual stresses, sub-surfaces pores, a rough surface and a contour-core microstructure that lead to a low fatigue strength. Residual stresses can be relieved with a heat-treatment to enhance the fatigue properties, but the best performance is obtained after machining and polishing. The differences between the polished and the heat-treated net-shape conditions lie in the sub-surface microstructure, the surface topography, and the population of sub-surface pores. This study aims to quantify the impact of each of these sub-surface parameters on the fatigue behaviour. To do so, the sub-surface microstructure of the net-shape condition is characterized. Then, uni-axial fatigue tests are carried out on stress-relieved specimens with the following surface conditions: net-shape, partially polished, and machined and polished. For defects smaller than 200 μm, the sub-surface microstructure is the most influential parameter on the fatigue strength. The grain size under the surface is considered in the Kitagawa-Takahashi diagram relatively to the killer defect size and allows to align all the batches.

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Dates et versions

cea-05580221 , version 1 (03-04-2026)

Identifiants

  • HAL Id : cea-05580221 , version 1

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Marion Auffray, Linamaria Gallegos Mayorga, Franck Morel, Etienne Pessard, Thierry Baffie. Leading role of the subsurface microstructure over the surface topography on the fatigue strength of stress-relieved L-PBF 316L parts. Metal AMS 2026, 3rd edition International Conference Metal Additive Manufacturing, Mar 2026, Senlis, France. ⟨cea-05580221⟩

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