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激光选区熔化成形CoCrMo合金的组织各向异性及摩擦磨损性

Microstructure anisotropy and wear performance of CoCrMo alloys melted by selective laser melting

  • 摘要: 采用激光选区熔化成功制备了CoCrMo合金,利用光学显微镜、扫描电子显微镜和电子背散射衍射对横向和纵向两个平面CoCrMo合金显微结构进行了表征。结果表明,CoCrMo合金纵向平面呈现典型的鱼鳞形貌,晶粒平均直径为44.2 μm,表现出较弱的<100>与<111>织构;横向平面主要由细小的六边形胞状结构组成,晶粒取向优先沿<110>方向生长,晶粒平均直径为29.5 μm,相比纵向平面低了33.26%。横向平面成形试样的小角度晶界占比(体积分数)、硬度和摩擦系数分别为39.6%、HV 435和0.5958;纵向平面上的小角度晶界占比(体积分数)、硬度和摩擦系数分别为28.6%、HV 416和0.7605。激光选区熔化成形CoCrMo合金在微观结构与力学性能上均存在明显的各向异性,横向平面成形试样硬度高归因于细晶强化和较高的初始位错密度,优异的磨损性能归因于胞状微观结构,容易粘着磨损轨道,提高耐磨性。

     

    Abstract: The CoCrMo alloys were successfully prepared by selective laser melting (SLM), the microstructures of the CoCrMo alloys in transverse and longitudinal planes were characterized by optical microscope (OM), scanning electron microscope (SEM), and electron backscattering diffraction (EBSD). The results show that the CoCrMo alloys in longitudinal plane show the typical fish scale morphology, the average diameter of the grains is 44.2 μm, showing a weak <100> and <111> weave; the CoCrMo alloys in transverse plane mainly consist of the fine hexagonal cellular structure, the grain orientation preferentially grows along the <110> direction, and the average diameter of the grains is 29.5 μm, which is 33.26% lower compared with that of the longitudinal plane. The proportion of small angle grain boundaries (volume fraction), hardness, and friction coefficient of the specimens in transverse plane are 39.6%, HV 435, and 0.5958, while those of the longitudinal plane are 28.6%, HV 416, and 0.7605, respectively. The SLM-formed CoCrMo alloys have the obvious anisotropy both in microstructure and mechanical properties. The higher hardness of the transverse plane-formed specimens is attributed to the fine-grained reinforcement and higher initial dislocation density, and the excellent wear property is mainly attributed to the cytosolic microstructure, which are easy to adhere to the wear track and improve the wear resistance.

     

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