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.

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This study investigated the stress relaxation and fatigue life and strength of laser peened single crystal nickel superalloy specimens compared to un-peened and shot peened specimens following hot corrosion exposure and then fatigue testing. The specimens were treated by conventional laser peening and a new cyclic laser peening plus thermal microstructure engineering process. The latter treatment supports the benefit of a unique process involving application of layers of laser peening using high energy with large footprint spots combined with interspersed cyclic annealing. Stress measurements by slitting showed the plastic penetration depth of laser peening exceeded shot peening by a factor of 24. Un-peened and peened specimens were exposed to sulphate corrosives at 700°C for 300 hours and then fatigue tested. Tests of five non-laser peened specimens all failed in low cycle fatigue regime whereas three identically tested laser peened specimens all achieved multi-million-cycle runout without failure, indicating fully consistent large benefit for life by laser peening. Additional tests also showed fatigue strength improvement of 2:1 by laser peening. Residual stress measurements post hot-corrosion exposure and fatigue testing showed notable 5 mm depth retention of residual eigenstress in a laser peened specimen.

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