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选区激光熔化成形CoCrMo合金的组织各向异性及摩擦磨损性

Anisotropy in Microstructure and Wear Performance of CoCrMo Alloy Melted by Laser Selective Melting

  • 摘要: 本研究采用激光选区熔化成功制备了CoCrMo合金,分别对横向和纵向两个平面的CoCrMo合金试样进行试验。利用光学显微镜(OM)、扫描电子显微镜(SEM)和电子背散射衍射(EBSD对其显微结构进行了表征。结果表明,纵向平面上呈现典型的鱼鳞形貌,晶粒平均直径为44.2μm,表现出较弱的<100> 与<111>织构;而横向平面上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29.5μm,相比纵向平面低了33.26%;横向平面成形试样的小角度晶界、硬度和摩擦系数分别为39.6%、435HV和0.5958;而纵向平面上的小角度晶界、硬度和摩擦系数分别为28.6%、416HV和0.7529。SLM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;而优异的磨损性能主要归因于其具有胞状微观结构,容易粘着磨损轨道,提高耐磨性。本研究揭示了激光选区熔化CoCrMo合金的微观组织和力学性能各向异性机理,为CoCrMo合金在生产应用提供理论基础。

     

    Abstract: In this study, CoCrMo alloys were successfully prepared by laser selective melting, and the CoCrMo alloy specimens were tested in two planes, transverse and longitudinal, respectively. The microstructures were characterized using optical microscopy (OM), scanning electron microscopy (SEM) and electron backscattering diffraction (EBSD).The results show that the longitudinal plane shows typical fish scale morphology, the average diameter of the grains is 44.2 μm, showing a weak <100> and <111> weave; while the transverse plane mainly consists of fine hexagonal cellular structure, grain orientation preferentially grows along the <110> direction, the average diameter of the grains is 29.5μm, which is 33.26% lower compared with that of the longitudinal plane; the small angle grain boundaries, hardness and friction coefficient of the transverse plane molding samples The small-angle grain boundaries, hardness and friction coefficient of the transverse plane molding specimens were 39.6%, 435 HV and 0.5958, respectively, while those of the longitudinal plane were 28.6%, 416 HV and 0.7529, respectively.SLM-formed CoCrMo alloys have obvious anisotropy in both microstructure and mechanical properties. The high hardness of transverse plane-formed specimens is attributed to the fine-grained reinforcement and higher initial dislocation density; and the excellent wear properties are mainly attributed to their cytosolic microstructures, which are easy to adhere to the wear tracks and improve the wear resistance. This study reveals the mechanism of anisotropy of microstructure and mechanical properties of CoCrMo alloy melted by laser selective melting, which provides a theoretical basis for the application of CoCrMo alloy in production.

     

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