激光熔覆CoCrFeNiSix高熵合金涂层的组织及性能

目的 研究Si含量对CoCrFeNi高熵合金激光熔覆涂层的组织及性能的影响.方法 利用激光熔覆技术在45#钢基材上制备CoCrFeNiSix(x=0.0,0.5,1.0,1.5,2.0)高熵合金涂层,通过扫描电镜(SEM)、X射线衍射仪(XRD)、显微硬度计、摩擦磨损试样机,对单道和多道熔覆层的宏观形貌、微观组织、显微硬度及摩擦磨损性能进行观察和测试.结果 高熵合金涂层与基体形成良好的冶金结合,添加适量的Si可以提高熔覆层的表面成形性,随着Si的添加,合金的稀释率先增后减,且润湿角逐渐减小.涂层的微观组织随Si含量的升高由等轴晶变为树枝晶,后又变为等轴晶,晶粒结构尺寸减小,涂层致密度提高.涂层由fcc结构变为bcc结构.涂层的显微硬度随Si含量的增加而增加,在x=2.0时,硬度达到600HV0.5左右,约为基体3倍.磨损方式由粘着磨损变为磨粒磨损,当Si含量最高时,磨损量达到最少,摩擦因数也最低,约为0.49.结论 在CoCrFeNi基高熵合金中添加Si可以降低合金的熔点,提高润湿能力;Si还可以增加涂层的形核率,起到细化晶粒的作用;Si作为添加元素还提高了涂层硬度,改善了涂层的耐磨减摩作用.

Microstructure and Properties of Laser Cladding CoCrFeNiSix High-entropy Alloy Coating

The work aims to study the effect of Si content on the microstructure and properties of CoCrFeNi high-entropy alloy coating. Preparation of CoCrFeNiSix (x=0.0, 0.5, 1.0, 1.5, 2.0) high-entropy alloy coating on 45# steel substrate by laser cladding technology. The macro morphology, microstructure, microhardness and friction and wear properties of single and multi-layer cladding layer are observed by scanning electron microscopy (SEM), X-ray diffractometer (XRD), microhardness tester and friction wear tester. The research shows that high-entropy alloy coating forms a good metallurgical bond with the substrate, adding an appropriate amount of Si can improve the surface formability of the cladding layer. With the increase of Si content, the microstructure of the coating changes from equiaxed crystals to dendrites, and then to equiaxed crystals. Coating changes from fcc structure to bcc structure.The unit cell structure size decreases and the coating density increases. When x=2.0, the hardness reaches about 600HV0.5, which is about 3 times of the substrate. When the Si content is the highest, the wear amount is the smallest and the friction coefficient is also the lowest, which is about 0.49. Overall, adding Si to CoCrFeNi-based high-entropy alloy can lower the melting point of the alloy, improve the wetting ability, and improve the oxidation behavior of the coating. Si can also increase the nucleation rate of the coating and play a role in grain refinement. Si as an added element also increases the hardness of the coating and improves the wear resistance and friction reduction of the coating.