Laser shock peening for suppression of hydrogen embrittlement of Inconel 718

This study investigates the impact of hydrogen embrittlement on the microstructure and mechanical properties of as-received (AR) and laser shock peened (LSP) Inconel 718, a material commonly used in subsea oil and gas engineering due to its high strength and corrosion resistance. Hydrogen embrittlement was induced through electrochemical charging and evaluated using slow strain rate tensile testing (SSRT). The comparison between AR and LSP-treated samples shows that while LSP-treated samples maintain similar yield strength whether charged or uncharged (544.69 MPa uncharged to 557.72 MPa charged), they exhibit higher susceptibility to hydrogen embrittlement in terms of ductility, with strain to failure decreasing by about 11.9 % under hydrogen charging. In contrast, AR samples lose both yield strength and ductility when exposed to hydrogen, with yield strength dropping by about 9.2 %, and strain to failure decreasing by approximately 8.7 %. This retention of yield strength under hydrogen exposure in LSP-treated samples suggests that LSP treatment may be advantageous in applications where preserving yield strength is critical. Additionally, the LSP process induces a uniform increase in dislocation density, leading to extensive dislocation tangling with minimal macroscopic deformation. This dislocation structure not only limits long-range dislocation diffusion but also mitigates the Hydrogen-Enhanced Localized Plasticity (HELP) mechanism, further enhancing resistance to hydrogen embrittlement. Despite the potential for field failures due to hydrogen embrittlement, this study underscores the limited research on improving resistance in hydrogen-rich environments.