ZrC增强激光熔覆CoCrNi合金熔覆层的组织及性能

本研究采用激光熔覆技术,在低碳钢表面制备了ZrC增强的CoCrNi合金涂层。研究了ZrC的不同分数(0, 1, 3, 5 wt.%)对CoCrNi基中熵合金涂层组织、硬度和耐磨性的影响。利用X射线衍射仪、扫描电镜和能谱仪分析了涂层的相组成及微观组织结构,并采用显微硬度和摩擦磨损试验对样品的硬度和耐磨性进行了测试。结果表明：熔覆层与基体形成了良好的冶金结合,没有出现明显的裂纹和及空洞等缺陷。不含ZrC的CoCrNi中熵合金涂层由单相FCC结构组成,随着涂层中ZrC的加入,涂层中的物相组成变为了FCC+ ZrC_0.7+Cr₂₃C₆+ZrO₂。涂层的晶粒得到了明显细化,实现了晶界强化、固溶强化和弥散强化(Orowan)的共同作用,形成的碳化物Cr₂₃C₆相与FCC固溶体结合形成共晶碳化物,起到了协同强化作用,有效地提高了涂层的硬度和耐磨性。然而ZrC中的Zr与空气中的杂质O结合生成的ZrO₂也对涂层的性能产生了不利影响,主要是因为ZrO₂的存在会导致涂层中颗粒分布不均匀加剧,弱化弥散强化的作用。所以当ZrC较少时,涂层的性能并未得到较好的提升,但是当涂层中ZrC含量增加到5wt.%时,涂层中析出了较多的强化相ZrC0.7能够有效的提高材料的性能,该涂层的最大硬度为651±15 HV_0.1,摩擦系数为0.161,相较于不含ZrC的涂层均有较大的提升。

Microstructure and Properties of ZrC Enhanced Laser Cladding CoCrNi Alloy Cladding Layer

ZrC strengthened CoCrNi-based laser cladded coatings with different content of ZrC were prepared on the surface of low carbon steel. The effects of ZrC addition on microstructure, hardness and wear resistance of CoCrni-based medium entropy alloy coating were investigated. The results show that there is a good metallurgical bond between the cladding layer and the matrix without obvious cracks and defects. The CoCrNi alloy coating without ZrC is composed of single-phase FCC structure. With the addition of ZrC in the coating, the coating phase compositions change to FCC+ ZrC0.7+Cr23C6+ZrO2 multiple phase structures. The grains of the coating were significantly refined, and the combination of grain boundary strengthening, solution strengthening and dispersion strengthening (Orowan) was realized, which effectively improved the hardness and wear resistance of the coating. However, ZrO2 produced by the combination of Zr in ZrC and O in the air also has an adverse effect on the performance of the coating, mainly because the presence of ZrO2 will cause the uneven distribution of particles in the coating and weaken the effect of dispersion strengthening. Therefore, when the content of ZrC is small, the performance of the coating is not improved. However, when ZrC content in the coating increases to 5wt.%, more ZrC0.7 phase is separated out from the coating, which can effectively improve the performance of the material. The hardness is 651±15 HV_0.1 and the friction coefficient is 0.161 which is much lower owing to the synergetic strengthening effect.