Investigation of the Microstructure and Microhardness of Inconel 792 Superalloy After Laser Shock Peening

Document Type : Article

Authors

1 Faculty of Mechanical Engineering, University of Birjand, Birjand, Iran.

2 Faculty of Materials Engineering of Birjand University of Technology, Birjand, Iran.

3 Faculty of Physics of Vali-e-Asr University of Rafsanjan, Rafsanjan, Iran.

Abstract

The use of laser shock peening (LSP) as a novel surface treatment generates controlled compressive residual stresses in materials, thereby enhancing their service life, particularly in stress‑sensitive environments. In the present study, the effect of varying the laser beam diameter on the microstructure and microhardness of cast Inconel 792 superalloy subjected to LSP was investigated. X‑ray diffraction (XRD) analysis was employed to identify the phases and quantify the surface residual stresses, while optical microscopy was used to examine the microstructure and the phases formed after chemical etching. The results confirmed the presence of residual stresses within the dendritic microstructure of the γ and γ′ phases. LSP produced significant grain refinement near the surface, leading to a reduction in grain area by approximately 62 %. Meanwhile, the microhardness of the treated region increased by 30 % up to a depth of 2 mm, and the residual stress was transformed from tensile to compressive, reaching about 290 MPa. These findings demonstrate that laser shock peening can effectively induce high compressive residual stress and promote surface grain refinement in Inconel 792, resulting in improved mechanical properties and enhanced durability under demanding service conditions.

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