Improving the surface quality and mechanical properties by shot-peening of 17-4 stainless steel fabricated by additive manufacturing

Abstract

Direct metal laser sintering (DMLS), a type of additive manufacturing (AM) process, is currently used for the direct fabrication of powder-based functional metallic objects. The main concern in industrial application of DMLS is the range of materials that can be processed while ensuring that the resulting surface roughness and mechanical properties are equivalent to or better than those of wrought materials. This paper presents an attempt at inducing grain refinements through a shot-peening (SP) process creating severe plastic deformation at the outer surface layers to improve the physical and mechanical properties of 17-4 stainless steel components produced by DMLS. The as-built sample exhibited high content of retained austenite and the SP treatment induces a martensitic phase transformation; the micro-strain and compressive residual stresses were significantly increased upon SP. Compared to an as-built sample, a shot-peened sample exhibited a refined surface microstructure and more favorable roughness, hardness, compressive yield strength, and wear resistance, because of the obtained very fine microstructure. We believe that with the use of SP technology presented in this study, the use of AM materials for a wide range of potential applications should significantly increase for improving their performance. This can highlight the efficiency and applicability of the SP treatment to practical cases.