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激光功率对激光熔覆Stellite 6合金微观组织及磨损性能的影响

Effect of laser power on microstructure and wear properties of laser cladding Stellite 6 alloy coating

  • 摘要: 采用激光熔覆技术在0Cr17Ni4Cu4Nb不锈钢表面制备Stellite 6合金涂层,利用光学显微镜(OM)、扫描电子显微镜(SEM)、能谱仪(EDS)、电子背散射衍射分析(EBSD)、激光共聚焦显微镜(CLSM)等表征涂层的微观组织,并测试了试样的硬度和耐磨性能。不同激光功率参数制备的涂层均无明显气孔、裂纹等缺陷,且涂层与基体均有良好的冶金结合。涂层的组织主要由底部的柱状晶,中部的树枝晶以及顶部的等轴枝晶组成。涂层的硬度(420~510 HV)显著高于基体(206 HV),硬度沿涂层顶部到基体逐渐降低。激光功率为1400 W的样品组织最细小均匀,同时枝晶间的硬质相(碳化物)较多,表现出最高的硬度。经过磨损实验测试,所有样品表面均出现沿滑动方向平行的犁沟,无明显磨屑堆积的情况,属于磨粒磨损机制。激光功率为1400 W的样品,摩擦系数最小,同时磨痕宽度(928.463 μm)最窄,磨痕深度(45.087 μm)最小,表现出最好的耐磨性能。

     

    Abstract: Stellite 6 alloy coating was prepared on 0Cr17Ni4Cu4Nb stainless steel by laser cladding technology. The microstructure of the coating was characterized by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and confocal laser scanning microscopy (CLSM). The hardness and wear resistance of the sample were tested. The coatings prepared with different laser power parameters had no obvious defects such as pores and cracks. The coating of all samples had good metallurgical bonding with the substrate. Therefore, all 5 laser powers were reasonable process parameters. The microstructure of the coatings mainly consisted of coarse columnar dendrite at the bottom, coarse dendritic crystals at the middle, and fine equiaxed dendrite at the top. The hardness of the coating (420~510 HV) was significantly higher than that of the substrate (206 HV), and the hardness gradually decreased from the top of the coating to the substrate. The sample with a laser power of 1400 W exhibited the smallest and most uniform microstructure, while there were more hard phases (carbides) between dendrites. Therefore, the 1400 W sample exhibited the highest hardness. After wear experiment testing, all sample surfaces showed parallel furrows along the sliding direction, without obvious accumulation of debris, which belongs to the abrasive wear mechanism. The sample with a laser power of 1400 W had the lowest friction coefficient (0.353) and wear rate (0.954 m3sN-1), while the 1400 W sample had the narrowest wear scar width (928.463 μm) and the minimum depth of wear marks (45.087 μm), exhibiting the best wear resistance.

     

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