The shot peening procedure enhances the mechanical characteristics with the transformation of compressive residual stresses which helps in the increment of operational lifespan of the product. The study comprehensively analyzed the effect of consecutive shot peening procedures up to four peening passes with the coverage increases 100% on each peening pass up to 400% on the laser powder bed fused austenitic stainless steel and compared with the as-built condition focusing on surface characteristics, mechanical characteristics, and corrosion potential. Surface damage of the peened samples was found very minimal with the absence of visible scan tracks and unmelted powder particles due to the controlled peening parameters. The inducement of compressive residual stresses (-625 MPa) was observed to be higher at the fourth consecutive peening passes without strain-induced martensite, with an increment of hardness proportion of 29.12% with a depth of 1 mm, and increment of corrosion resistance across each peening pass.

The utilization of laser shock peening (LSP) in laser powder bed fused (LPBF) stainless steel (SS) 316L components enhances the mechanical characteristics and operational lifespan of the product quality through a significant reduction of residual stress and a noticeable increase in roughness parameters. The key objective of the study is to analyze the influence of consecutive laser shock peening (LSP) without ablative coating and low pulse energy on the surface properties, residual stress distribution, and microhardness of samples produced by LPBF with SS316L material. The surface quality of the sample subjected to consecutive laser shock peening shows a slight deterioration in its condition. This can be attributed to the combined impact of ablative surface and surface damage resulting from the production of high-energy plasma. However, the implementation of successive LSP results in a distinctive enhancement of compressive residual stresses (CRS) that are evenly distributed throughout the central axis and sharp edges. In contrast, the as-built condition exhibits non-uniform stress magnitudes. CRS observed in each LSP iteration exhibits a notable increase, reaching a maximum magnitude of -389 MPa compared to the initial stress level of 165 MPa in the as-built sample. This enhancement can be attributed to the repetitive impact of shock waves on the surface, leading to the formation of plastic deformation. The refinement of surface grains and the presence of favorable residual stresses were proven by the utilization of x-ray diffraction (XRD) studies and the Cos alpha plot. The XRD investigation also indicated the absence of any newly formed phases or secondary phases. A significant enhancement in microhardness was observed, with an increase of 58.3% achieved after the third consecutive peening process. The successive LSP samples displayed a gradual improvement in electrochemical behavior. Though the amplitude parameters increased after LSP, the increase in wear rate was observed.

The current investigation involves the fabrication of fifteen samples of austenitic stainless steel 316 L (SS316L) utilizing laser powder bed fusion technology to evaluate the residual stresses through the impact of energy density, which was varied between 30 J/mm3 and 111 J/mm3 by varying process parameters, notably scanning speed and laser power. The energy density range suggested by existing literature has been found to have samples with significant mechanical properties, apart from its impact on residual stress, which can affect the service life of the product. The primary focus of this study is to identify the optimal window for achieving residual stress at various locations within the sample. The study discovered differences in residual stress development at all tested locations. When employing lower laser powers of 140 W and 160 W, residual stress formation remained consistent. Furthermore, when the laser power exceeds 140 W to 160 W, a substantial temperature gradient develops, leading to a considerable rise in tensile stress magnitude. The variation in energy density does not affect residual stress, while there is a variation in two process parameters, laser power and scanning speed, simultaneously. A laser power range of 140 W to 160 W, combined with scanning rates ranging from 500 mm/s to 1100 mm/s, results in a consistent range of minimal residual stress formation across multiple locations. The key outcomes of the study show the crucial role of laser power and scanning speed in residual stress development, which has implications for improving mechanical characteristics and product service life by generating minimal residual stresses.

Metal additive manufacturing (AM) is a revolutionary technological advancement that has made significant inroads in a wide range of sectors, including aerospace, defense, automotive, health care, and engineering applications. It offers unprecedented design freedom, reduced material waste, and enhanced performance, in addition to significant enhancements to fabrication processes. Microstructural defects and internal stresses formed during fabrication directly affect the fabricated product's surface integrity, quality, and service life. Identification, characterization, and prediction of these defects help significant and direct production of defect-free structures with high density. This article provides detailed insights concerning the common defects, mitigation techniques, and challenges reported in both powder bed fusion-based and wire arc AM methods. Defects such as porosity may develop due to the powder sphericity, roughness of the powder, preheating, process parameters, build environment, postprocessing techniques, and environmental factors. Therefore, a critical study of the techniques, alloys, process parameter optimization, and different postprocessing techniques to tone down the defects is made from their formations.

In this study, laser powder bed fused (LPBF) Inconel 718 alloy coupons are exposed to laser shock peening and shot peening to evaluate the post-treatment effect on mechanical performance. The coupons are analyzed under different conditions, such as As-built, heat-treated, shot-peened, and Laser shock peening (LSP) with overlapping percentages of 60, 70, and 80. The micrograph of the As-built IN718 sample surface shows the presence of unfused powder and tiny pores with precipitation, the laser-peened sample exhibits the refinement of the grains, while the shot-peened sample exhibits defect-free surface with waviness where the X-ray Diffraction (XRD) peaks ensure the quantitative agreement in each stage of the peening process. The microhardness was increased by 102.87% after LSP with 80% overlap, and by 71.96% after shot peening. The compressive residual stress was enhanced 2.39 times after shot peening and 1.78 times after LSP-80% when compared to the as-built coupon. This study has shown the elimination of the tensile residual stress, increment of microhardness, improvement of surface morphology in Laser powder bed fused material through LSP, and shot peening of IN718 alloy.