基于高速激光熔覆技术的Ni-Co合金涂层组织性能及耐磨性研究

Study on the Structure,Properties,and Wear Resistance of Ni-Co Alloy Coating Based on High-Speed Laser Cladding Technology

利用高速激光熔覆技术,在C422钢表面制备Ni-Co基合金强化涂层,以提高其耐磨性和抗拉毛能力,从而延长蒸汽轮机阀杆的服役寿命。通过调整激光功率、扫描速度、搭接率和送粉速度等工艺参数,在C422钢材表面制备了不同组织的Ni-Co基合金强化涂层。采用金相观察、XRD检测、显微硬度测试和摩擦磨损试验等方法,对涂层的微观组织、物相组成、硬度和耐磨性进行了表征,以解明蒸汽轮机零部件表面磨损和失效的一般规律。结果表明,Ni-Co基高速激光熔覆层的物相成分主要为γ-Co固溶体、(Cr-Fe)7C3硬质碳化物及Ni4W金属间化合物等。熔覆层微观组织为网状超细共晶组织,晶粒细小且排列紧密。涂层显微硬度较基体有明显增高;涂层耐磨性较基体有较大提升。进一步研究表明,在合适的功率等其他条件下Ni-Co基合金高速激光熔覆层能够提高基体表面的硬度以及耐磨损性能;扫描速度对于涂层组织性能的影响较大,扫描速度提升时组织发生固溶强化、细晶强化和硬质化合物产生的弥散硬化共同作用导致了耐磨性提高,为机械零件磨损失效的问题提供解决方法和理论依据。

This paper aims to utilize high-speed laser cladding technology to prepare a Ni-Co based alloy reinforced coating on the surface of C422 steel,in order to improve its wear resistance and anti-pulling ability,thereby extending the service life of steam turbine valve rods.By adjusting process parameters such as laser power,scanning speed,overlap rate,and powder feeding speed,Ni-Co based alloy reinforced coatings with different structures were prepared on the surface of C422 steel material.Methods such as metallographic observation,XRD detection,microhardness testing,and friction and wear tests were used to characterize the microstructure,phase composition,hardness,and wear resistance of the coating,in order to understand the general laws of surface wear and failure of steam turbine components.The results show that the phase components of the Ni-Co based high-speed laser cladding layer mainly include γ-Co solid solution,(Cr-Fe)7C3 hard carbide,and Ni4W intermetallic compounds.The microstructure of the cladding layer is a network-like ultra-fine eutectic structure,with fine and closely arranged grains.The microhardness of the coating is significantly higher than that of the substrate;the wear resistance of the coating has been greatly improved compared to the substrate.Further research indicates that under appropriate power and other conditions,the Ni-Co based alloy high-speed laser cladding layer can improve the hardness and wear resistance of the substrate surface;the scanning speed has a significant impact on the performance of the coating structure.When the scanning speed increases,the combined effects of solid solution strengthening,fine grain strengthening,and the dispersion hardening caused by the production of hard compounds lead to improved wear resistance,providing solutions and theoretical basis for addressing the issue of mechanical part wear and failure.