Exploring laser-induced protection material assisted elevating the forming quality of multi-pass ER2209 coating via underwater wet laser cladding

Underwater wet laser cladding (UWLC) technology has considerable application potential for in situ repair of offshore engineering equipment. Moreover, multipass UWLC has notable practical application value and can ensure the efficiency of underwater repair processing. A multipass laser cladding layer with high forming quality that is formed in a complex underwater environment has notable application value. Herein, new results regarding the preparation of in situ multipass UWLC duplex stainless steel (DSS) coatings are reported. Multipass ER2209 UWLC coatings are successfully prepared in a completely wet environment. Laser-induced self-protection materials are used to counter and eliminate the effects of the water environment on the forming quality of the UWLC coatings. The results show that the numerous porosity defects on the cladding layer surface are attributed to effects such as laser-induced cavitation and water ionization. Effective use of laser-induced protective materials mitigates the detrimental effects of water intrusion. The rapid cooling effect of the underwater environment is counteracted by the heat input form the underwater multipass laser and the exothermic action of the protective material. Compared with ER2209 air laser cladding (ALC) coatings, the accumulation of dislocations at grain boundary slightly decreases the corrosion resistance of the ER2209 UWLC coatings. Multipass underwater cladding formation assisted by laser-induced protection materials offers valuable theoretical insights for in situ repair of underwater equipment.