Tailoring residual stress profile of Selective Laser Melted parts byLaser Shock Peening

The paper describes a new approach in controlling and tailoring residual stress profile of parts made bySelective Laser Melting (SLM). SLM parts are well known for the high tensile stresses in the as – built statein the surface or subsurface region. These stresses have a detrimental effect on the mechanical propertiesand especially on the fatigue life. Laser Shock Peening (LSP) as a surface treatment method was appliedon SLM parts and residual stress measurements with the hole – drilling method were performed. Twodifferent grades of stainless steel were used: a martensitic 15-5 precipitation hardenable PH1 and anaustenitic 316L. Different LSP parameters were used, varying laser energy, shot overlap, laser spot sizeand treatments with and without an ablative medium. For both materials the as-built (AB) residual stressstate was changed to a more beneficial compressive state. The value and the depth of the compressivestress was analyzed and showed a clear dependence on the LSP processing parameters. Application of LSPon SLM parts showed promising results, and a novel method that would combine these two processes isproposed. The use of LSP during the building phase of SLM as a “3D LSP” method would possibly give theadvantage of further increasing the depth and volume of compressive residual stresses, and selectivelytreating key areas of the part, thereby further increasing fatigue life.