Surface strengthening and wear resistance enhancement of electron beam powder bed fusion fabricated Ni-based superalloys via laser shock peening

Abstract

Electron beam powder bed fusion (EBPBF) enables the direct fabrication of non-weldable superalloy components; however, surface strengthening remains essential to enhance wear performance. This study investigates the effect of laser shock peening (LSP) on the 600 °C dry sliding wear performance of EBPBF-fabricated IN738 superalloys. LSP introduces a millimeter-scale work-hardened layer through the formation of high-density dislocation structures, including dislocation pairs, stacking faults, and Lomer-Cottrell (L-C) locks, without causing grain refinement or texture changes. Notably, the LSP-treated sample using laser energy of 5 J showcases the most pronounced hardening effect and demonstrates the greatest improvements in wear resistance, with an average coefficient of friction (COF) and wear rate reduced by 23.6 % and 73.6 %, respectively, compared to the as-received sample. This improvement is primarily attributed to the synergistic effects of the work-hardened layer and compressive residual stress (CRS). Additionally, LSP-induced dislocation structures provide a fast pathway for inward oxygen diffusion, facilitating the formation of a uniform oxide layer that protects the surface from wear mass loss and lowers the COF through self-lubricating. As a consequence, LSP treatment shifts the wear mechanism from adhesive wear in the untreated samples to a combination of abrasive and oxidative wear in LSP-treated samples. This study provides valuable insights into the role of the LSP-induced surface-strengthening effect in enhancing wear resistance and highlights the potential of combining surface-strengthening technologies with additive manufacturing for the production of high-performance aerospace components.