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激光功率对激光熔覆Stellite 6合金涂层微观组织及耐磨性能的影响

Effect of laser power on microstructure and wear resistance of laser cladding Stellite 6 alloy coatings

  • 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、扫描电子显微镜、能谱仪、电子背散射衍射分析仪、激光共聚焦显微镜等表征涂层的微观组织,并测试了试样的硬度和耐磨性能。结果表明,不同激光功率制备的涂层均无明显气孔、裂纹等缺陷,且与基体有良好的冶金结合。涂层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。涂层硬度(HV 420~510)显著高于基体(HV 206),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 coatings were prepared on 0Cr17Ni4Cu4Nb stainless steels by laser cladding technology. The microstructure of the coatings 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 samples were tested. In the results, all the coatings prepared with different laser powers have no obvious defects, such as pores and cracks, and show the good metallurgical bonding with the substrate. The microstructure of the coatings is mainly consisted of the coarse columnar dendrite at the bottom, the coarse dendritic crystals in the middle, and the fine equiaxed dendrite on the top. The hardness of the coatings (HV 420~510) is significantly higher than that of the substrate (HV 206), and the hardness gradually decreases from the top of coating to the substrate. The samples with the laser power of 1400 W exhibit the smallest and most uniform microstructure, while there are more hard phases (carbides) between dendrites. Therefore, the 1400 W samples exhibit the highest hardness. After the wear experiment testing, all the sample surfaces show the parallel furrows along the sliding direction without the obvious accumulation of debris, which belongs to the abrasive wear mechanism. The samples with the laser power of 1400 W have the lowest friction coefficient, while show 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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