Feasibility Study of a Novel Post-Processing Method Based on Microscale Laser Shock Peening Without Coating for Selective Laser Melting-Fabricated Components

Selective Laser Melting (SLM) has been widely employed for fabricating lightweight and integrated components for aircraft and aero-engine applications. However, SLM-fabricated components, especially those containing locally complex surface regions, often suffer from burrs, balling, microcracks, and tensile residual stress (TRS). These issues are difficult to eliminate by conventional machining or heat treatment (HT) alone. Consequently, such defects degrade fatigue performance and restrict the practical engineering application of SLM-fabricated components. This study proposed a novel direct surface post-processing method utilizing microscale laser shock peening without coating (μLSPwC) for locally complex surface regions of SLM-fabricated components. The process was designed to combine laser-induced local micro-melting for surface defect mitigation with shock-induced plastic deformation for near-surface strengthening. SLM-fabricated 17-4PH (AISI 630, UNS S17400) stainless steel, TC4 (Ti-6Al-4V) titanium alloy, and GH4169 (Inconel 718, UNS N07718) nickel-based superalloy were treated to assess the impact of μLSPwC on surface morphology, roughness, residual stress, microhardness, and rotating bending fatigue life. The surface roughness of all three materials dropped more than 20% after treatment. Furthermore, μLSPwC introduced compressive residual stress (CRS) layers and hardened layers exceeding 300 μm. The rotating bending fatigue life was improved by more than 20 times, and in some cases by over two orders of magnitude, at the selected stress levels. Therefore, μLSPwC is a promising post-processing technique for locally complex surface regions on SLM-fabricated components, particularly in situations where hot isostatic pressing, HT, or conventional surface machining is impractical or ineffective.