Effects of shot peening and laser peening on the microstructural, mechanical, and tribological properties of Inconel 625 superalloy

Abstract This study evaluates the impact of laser peening and shot peening on the mechanical, microstructural, and tribological properties of Inconel 625. Indentation and dry sliding tests were employed to investigate local mechanical properties and tribological enhancements resulting from the surface engineering techniques. Advanced electron microscopy techniques were utilized to study the surface morphology, chemical composition, and microstructure of specimens before and after the surface treatments and following tribological tests. The results demonstrate significant enhancements in near-surface microhardness following laser peening and shot peening treatments. The highest microhardness was observed in the shot peened specimen, while the highest macrohardness was observed in the laser peened specimen, highlighting deeper effects of the laser peening process. Electron microscopy analyses revealed notable lattice distortion and strain, elevated dislocation densities, and the formation of planar slip bands following shot peening and laser peening, with the deepest microstructural modifications and subsequent enhancements in mechanical properties observed in the laser peened specimen. Wear track images confirm abrasion and adhesion to be the dominant wear mechanisms for all specimens. While no noticeable change in the coefficient of friction was observed for all specimens, notable decreases in the wear rate were observed following laser peening and shot peening, with the laser peened specimen exhibiting the best resistance to wear. These findings provide useful quantitative and qualitative comparative insights into the outcomes of employing laser peening and shot peening to treat Inconel 625 and contribute to the understanding of the underlying mechanisms responsible for the observed microstructural and mechanical improvements.