Laser shock peening as a post-processing technique for Inconel 718 components manufactured by laser powder bed fusion

Additive manufacturing (AM) has shown advantages to fabricate complex components in an efficient way. However, it has some limitations related to imperfections on the as-built parts that may limit its mechanical behavior and performance. The aim of this paper is to investigate the effect of laser shock peening (LSP) as a post-processing technique of components produced by AM. Porosity, microstructure, residual stresses, and fatigue life of Inconel 718 samples manufactured by laser powder bed fusion (LPBF) and then treated by LSP have been evaluated. For the laser shock peening (LSP) treatment, a Nd:YAG pulsed laser operating at 10 Hz with 1064 nm of wavelength was used; pulse density was 2500 pulses/cm2. The LSP setup was the waterjet arrangement without protective coating. Residual stress distribution as a function of depth was determined by the hole-drilling method. Fatigue specimens were LSP treated on both sides and then cyclic loading was applied with R = 0.1. Residual stress profiles of as-built specimens showed tensile residual stresses while specimens with LSP exhibited compressive residual stresses. Fatigue life in specimens with stress relief heat treatment plus LSP showed an increase of 18-22% with respect to that of as-built specimens. Porosity levels were lower than 1% in the tested specimens, while surface microhardness increased due to LSP. It is shown that LSP is a viable alternative to improve the performance of IN718 components processed with AM.