激光重熔实现水下局部干法激光熔覆双相不锈钢耐磨性能提升

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

摘要:

水下局部干法激光熔覆（ULDLC）是核电站设备原位修复的关键技术。本研究提出采用水下激光重熔技术进一步提升ULDLC制备的双相不锈钢（DSS）涂层的耐磨性能。研究了激光重熔热输入对ULDLC-DSS涂层微观组织及耐磨性能的影响规律。结果表明：DSS涂层初始组织包含魏氏体奥氏体（WA）、晶内奥氏体（IGA）、晶界奥氏体、二次奥氏体（γ₂）及铁素体。随重熔热输入增加，IGA与WA的含量逐渐降低，WA完全消失，铁素体含量显著增加，γ₂相完全溶解，铁素体形貌由片状转变为等轴晶。在最优工艺参数（激光功率3 kW、光斑直径6 mm、扫描速度10 mm/s）下，重熔区显微硬度提升至318.7 HV，增幅达25.7 HV，摩擦系数降低32%，磨损量减少55%。熔覆金属耐磨性能的提升得益于激光重熔导致表面氧化层形成和铁素体晶粒细化的协同作用。

Abstract:

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 Widmanst?tten 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.