Abstract
With the ongoing expansion of marine resource development into deep-sea regions, underwater welding integrity plays a crucial role in various critical marine and nuclear infrastructure projects. Underwater laser welding has become an indispensable technique for marine engineering systems. However, deep-sea laser welding faces some major challenges, including the laser energy attenuation by seawater, the unstable molten pool solidification during rapid cooling, and poor joint corrosion resistance. High-entropy alloys (HEAs), as an emerging type of multi-principal-element metallic materials, address the core scientific problems arising from deep-sea laser welding through intrinsic material effects. Their high configurational entropy suppresses the precipitation of brittle intermetallic compounds during rapid solidification, which protects against the grain coarsening and element segregation caused in welds by underwater rapid cooling. Severe lattice distortion, induced by atomic size differences, scatters phonons to reduce thermal conductivity (30–50% lower than traditional ER308), thus minimizing laser energy attenuation and stabilizing molten pool behavior. The sluggish diffusion effect hinders the penetration of corrosive Cl− and harmful H+, while the “cocktail effect” of Cr, Ni, and Mn elements promotes the formation of a dense passive film. Collectively, this results in the improved corrosion and hydrogen embrittlement resistance of welds. These mechanisms enable HEAs to perform better in mechanical strength, corrosion resistance, and cold crack resistance. Compared with arc welding, which is prone to energy inefficiency and grain coarsening underwater, HEA-assisted laser welding exhibits superior process stability and joint reliability. This study provides a material-process integrated solution for high-performance deep-sea laser welding.
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