Using shot peening and burnishing to improve fatigue performance of additively manufactured 316L stainless steel

Abstract

Despite the growing demands for personalized items, the capacity of conventional production techniques is restricted to respond to such needs. Instead of conventional manufacturing processes, the intended structure can be directly constructed in a layer-by-layer manner, also known as additive manufacturing (AM). Among AM methods, selective laser melting (SLM) has gained a great deal of attention due to its low cost and availability. However, the poor surface quality in this method is still a problem as it may influence critical mechanical properties of the components like their fatigue life. Therefore, adequate postprocesses are required for additively manufactured metals. In the present study, shot peening (SP) and burnishing were applied as postprocesses to the 316 L stainless steel manufactured by SLM, and then, surface roughness, porosity, microhardness, and fatigue performance were experimentally investigated. Based on the results, the mean surface roughness (Ra) of the as-SLMed sample was 10.907 µm which decreased to 8.543 and 1.324 µm, after SP and the burnishing processes, respectively. Interestingly, the burnishing process was more effective in eliminating near-surface pores and improving microhardness of the samples compared to SP. In addition, the fatigue life of the as-SLMed sample (135,000 cycles) slightly improved after SP (353,000 cycles), while burnishing drastically enhanced the fatigue life of the samples (3,030,000 cycles).