Underwater wet laser cladding on 316L stainless steel: A protective material assisted method

In this paper, a new underwater processing technology was proposed, called underwater wet laser cladding (UWLC). Protective material assisted UWLC was provided to increase the processed water depth of UWLC and promote the quality of UWLC coatings without changing the laser power. For comparison, the direct UWLC and protective material assisted UWLC were performed under various water depths with uniform experimental parameters. The UWLC processes under water depth of 15 mm were studied in detail. The blue-purple plasma appears during the direct UWLC processes leading to the failure of UWLC. The mental plume appears during the protective material assisted UWLC processes. In addition, the protective material assisted UWLC is more likely to succeed by increasing the content of protective material. The 316L stainless steel coatings were successfully prepared by protective material assisted UWLC. The microstructure of the 316L coatings by protective material assisted UWLC is well in agreement with 316L coatings prepared by laser cladding in air, while the 316L coating by direct UWLC is mainly composed of columnar dendrites. Moreover, the corrosion resistance of 316L coating by direct UWLC in 3.5 wt.% NaCl solutions is improved markedly by applying protective material. The energy loss in the process of underwater wet laser processing is significantly reduced through the protective material assisted method, which provides meaningful theoretical support for underwater wet laser repair.