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

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.