Investigation on in-situ laser cladding coating of the 304 stainless steel in water environment

•Underwater laser cladding coating of the 304 stainless steel was prepared in water environment in situ.•The high-density aerosol particles decreased the laser power density and reduced the stability of cladding process.•The water interaction on coating formation, grain, microstructure and corrosion performance was investigated.•The grain size decreased overall and the number of equiaxed grain dropped compared with in-air coating.•The increasing ferrite content caused the corrosion resistance of underwater coating reduced.