Abstract In this research, the effect of Ultrasonic Nanocrystal Surface Modification (UNSM) on residual stress an‎d crystallographic texture in Inconel 625 alloy produced by selec‎tive Laser Melting (SLM) was investigated. For this purpose, cubic samples of the alloy were first fabricated using the SLM 3D printing process. The as-built samples were then examined for their microstructure an‎d hardness. The UNSM treatment was carried out at three different power levels: 100, 170, an‎d 420 W. Subsequently, the modified samples were examined microstructurally in cross-section using optical microscopy an‎d SEM, an‎d the hardness gradient was eva‎luated. Residual stress was determined by measuring lattice strain using the X-ray diffraction (XRD) method. Furthermore, the crystallographic texture of the as-built an‎d UNSM-treated samples was analyzed using an XRD device equipped with a texture measurement attachment, an‎d the inverse pole figures (IPFs), pole figures (PFs), an‎d orientation distribution functions (ODFs) were plotted. The results showed that in a thin surface layer of the samples, the melt pools present in the SLM alloy microstructure were completely flattened, an‎d the fine grains observed in the as-built sample became further refined after UNSM. The surface hardness of the alloy increased from approximately 400 HV in the as-built condition to about 670 HV after UNSM at 420 W. Moreover, a hardness gradient from the surface to the depth was observed in the UNSM-treated samples, with hardened depths of approximately 200, 260, an‎d 320 μm for the samples treated at 100, 170, an‎d 420 W, respectively. The residual compressive stress increased from 78 MPa in the as-built sample to 109, 353, an‎d 549 MPa for the UNSM-treated samples at 100, 170, an‎d 420 W, respectively.Texture analysis revealed that the as-built sample exhibited a cubic texture along with a weak Goss component. After UNSM treatment at 100 an‎d 170 W, the cubic texture was intensified, while at 420 W, both the cubic an‎d Goss textures appeared again but with reduced intensity.

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