Research status and prospects of novel technology in underwater wet arc welding/laser cladding

Underwater wet welding (UWW) is more cost-effective and easier to perform compared to underwater dry and local dry welding, leading to its extensive use in offshore steel structure construction and maintenance. However, the water environment introduces challenges like rapid cooling, severe quenching, high hydrogen sensitivity, and alloy element loss. To address these, recent advancements have introduced various innovative techniques. This paper reviews the research status of novel techniques in UWW, and systematically classifies and summarizes the new processes based on their different mechanisms. It elaborates on the latest advancements and key mechanisms of underwater welding/cladding processes driven by auxiliary external energy fields and new techniques for protecting the molten pool zone in underwater wet welding/cladding. Study results demonstrate the influence mechanisms of underwater wet arc welding/laser cladding new techniques on enhancing the mechanical properties of welded joints and controlling diffusible hydrogen content. External energy fields improve weld morphology, microstructure, and mechanical properties by slowing the cooling rate of the weld metal, enhancing molten metal flow, and removing hydrogen from the molten pool. Protective materials in the preset protective layer reduce welding defects such as spatter, porosity, and discontinuities while improving mechanical properties by adjusting viscosity, increasing heat input, and reducing hydrogen content in the atmosphere. Additionally, this paper reviews the regulation mechanisms of underwater wet flux-cored arc welding (FCAW) techniques on welding process stability. External energy fields and protective materials modify the forces acting on droplets, reduce interference from the aqueous environment and arc bubbles, and facilitate droplet transfer into the molten pool. By comprehensively analyzing the processes and mechanisms of underwater wet welding/cladding new techniques, this paper proposes future development directions for underwater wet laser welding/cladding technology. It not only enriches the knowledge system of underwater welding/cladding processes but also provides guidance for the research and advancement of underwater wet welding/cladding techniques.