Enhanced Wear Resistance of ULDLC Duplex Stainless Steel Coating via Laser Remelting

Underwater local dry laser cladding (ULDLC) is a key technique for in-situ repair of nuclear power equipment. In this study, an underwater laser remelting technique was proposed to further enhance the wear resistance of duplex stainless steel (DSS) coatings prepared by ULDLC. The effects of laser remelting heat input on the microstructure and wear resistance of DSS coating prepared by ULDLC were investigated. Results indicate that the microstructure of DSS coatings consists of Widmanstätten austenite (WA), intergranular austenite (IGA), grain boundary austenite, secondary austenite (γ₂), and ferrite. With the increase in laser remelting heat input, the content of IGA and WA gradually decreases, while the ferrite content increases. After laser remelting, γ₂ is eliminated and the grain morphology of ferrite is transformed from flaky to equiaxed. Under optimal laser remelting parameters (a laser power of 3 kW, a laser spot diameter of 6 mm, and a laser scanning speed of 10 mm/s), the microhardness of remelted zone is 318.7 HV, which is increased by 25.7 HV, the friction coefficient decreases by 32%, and the wear volume is reduced by 55%. The significantly improved wear resistance is attributed to the synergistic effects of surface oxide-layer formation and ferrite grain refinement.