One of the biggest limitations of parts made by Selective Laser Melting (SLM) are the high tensile residual stresses (TRS) that accumulate in the near surface region during production. They are known to have a detrimental effect on the fatigue life and can even cause SLM process failure. Although a heat treatment can be applied for only a partial stress relieving after the part is made, it cannot introduce beneficial compressive residual stresses (CRS). The 3D Laser Shock Peening (3D LSP) process is a novel approach patented by the Laboratory of Thermomechanical Metallurgy at EPFL, which combines Laser Shock Peening (LSP) during the building phase of the Selective Laser Melting process. This gives an ability to tailor the residual stresses during the SLM process itself. Throughout the 3D LSP process, after a certain number of layers are made by SLM the LSP process is applied and this sequence is repeated until the completion of the part. The beneficial effect of the 3D LSP process on the hardness, residual stresses and the fatigue life of parts has been investigated. Different 3D LSP parameters were used, varying laser energy, shot overlap, laser spot size and the number of SLM layers between two subsequent LSP treatments. A clear and significant increase in the volume and depth of CRS was observed, with the expected increase of fatigue life. This increase was observed for all different 3D LSP process parameters compared to the SLM as – built and LSP states.
- Understand the basics of the 3D Laser Shock Peening.
- Evaluate the benefits of the 3D Laser Shock Peening process and the potential to apply it for their specific use-cases.