等温淬火处理对感应重熔镍基合金涂层摩擦学性能的影响

目的改善镍基合金涂层的摩擦学性能。方法分别采用感应重熔工艺及感应重熔-等温淬火一体化工艺,在GCr15钢基体表面制备了两种镍基合金涂层,并通过销盘摩擦磨损试验、扫描电子显微镜、X射线衍射仪、显微硬度测试对其摩擦磨损性能、微观组织、表面硬度进行了对比研究,探讨了等温淬火处理对感应重熔镍基合金涂层摩擦学性能、微观组织、表面硬度的影响,揭示了其增强机理。结果经等温淬火后的重熔涂层比感应重熔涂层具有更低的摩擦系数和磨损失重,摩擦稳定阶段的摩擦系数为0.301,比后者低23.8%,相对耐磨性是后者的1.71倍。感应重熔涂层同时存在着磨粒磨损和粘着磨损两种机制,而经等温淬火后的重熔涂层以磨粒磨损为主,比前者具有更优异的抵抗磨粒磨损和粘着磨损的能力。感应重熔涂层及经等温淬火处理后的重熔涂层平均显微硬度分别为818.0、873.6HV(0.5),硬度极差分别为170.9、132.6HV(0.5),形状参数分别为18.5057、22.6189,后者比前者具有更高的平均硬度值、更小的硬度极差以及更加稳定的涂层性能。经过微观组织分析发现,重熔涂层在经等温淬火处理后,其晶粒的细化、硬质相的相对均质弥散性、共晶相的减少、丰富的耐磨陶瓷相和快速凝固的定向晶粒结构的协同作用,是其具有优异的显微硬度Weibull分布特性,以及耐磨性得到进一步提高的根本原因。结论合适的等温淬火热处理工艺能够改善感应重熔镍基合金涂层的微观组织,从而有效减小其摩擦系数,并提高其耐磨性。

Effect of Isothermal Quenching on Tribological Properties of Induction Remelting Nickel-based Alloy Coatings

The work aims to improve the tribological properties of nickel-based alloy coatings. Two kinds of nickel-based alloy coatings were prepared on the surface of GCr15 steel by induction remelting and its isothermal quenching respectively. The friction and wear properties, microstructures and surface hardness of the two kinds of nickel-based alloy coatings were investigated comparatively by pin-disc friction and wear tests, scanning electron microscopy, X-ray diffractometer and microhardness tests. The effects of isothermal quenching treatment on the tribological properties, microstructure and surface hardness of nickel-based alloy coatings prepared by induction remelting were investigated, and the strengthening mechanism was revealed. The friction coefficient and wear loss of the remelting coatings after isothermal quenching were lower than that of the induction remelting coatings. The friction coefficient during the friction stabilization stage of the remelting coatings after isothermal quenching was 0.301, 23.8% lower than that of the latter, and the relative wear resistance was 1.71 times as much as that of the latter. There were two mechanisms of abrasive wear and adhesive wear in induction remelting coatings, while the remelting coatings after isothermal quenching were dominated by abrasive wear and had better resistance to abrasive wear and adhesive wear than the former. The average microhardness of the induction remelting coating and the coating after isothermal quenching was 818.0HV0.5 and 873.6HV0.5 respectively, the extreme hardness difference was 170.9HV0.5 and 132.6HV0.5 respectively, and the shape parameters were 18.5057 and 22.6189 respectively, thus the latter had higher average hardness, smaller extreme hardness difference and more stable coating properties than the former. Microstructure analysis showed that the synergistic effect of grain refinement, relative homogeneity and dispersion of hard phase, reduction of eutectic phase, abundant wear-resistant ceramic phase and directional grain structure of rapid solidification was the root cause of the excellent Weibull distribution of microhardness and the further improvement of the wear resistance. Therefore, the appropriate isothermal quenching heat treatment process can improve the microstructure of nickel-based alloy coating, thus effectively reducing the friction coefficient of the coating and improving its wear resistance.