Nanomechanical Characterization of Laser Peened Additively Manufactured Inconel 718 Superalloy

Abstract

Laser peening (LP) is a post‐processing method used to optimize the service lives of critical components for various applications by increasing the material's resistance to surface‐related failures, such as fatigue, corrosion‐fatigue, wear, and stress corrosion cracking. Herein, the effects of LP on the nanomechanical properties of additively manufactured Inconel 718 are reported. Additively manufactured cubic specimens peened without a protective overlay are evaluated under vigorous microscopy and nanomechanical studies. Depth sensing through hardness and modulus mapping is conducted to evaluate the plastic deformation and hardness enhancement introduced by the process. X‐ray diffraction is used to measure the residual stresses to correlate hardness and residual stresses. The results show that three layers of LP induces significant compressive residual stresses in the surface and subsurface (up to the depth of ≈2 mm) of the material and a moderate increase in hardness (≈20–30%) with high thermal stability of compressive stresses (retaining 60% of initial stress) after even 50 h of annealing at 593 °C. Slight changes in the elastic modulus are recorded in LP specimens.