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CN  62-1095/O4

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王世伟, 周晖, 徐莺歌, 张凯锋, 冯凯. CoCrFeNiWx高熵合金在室温及900℃下的摩擦磨损性能[J]. 摩擦学学报, 2024, 44(3): 1−11. doi: 10.16078/j.tribology.2023005
引用本文: 王世伟, 周晖, 徐莺歌, 张凯锋, 冯凯. CoCrFeNiWx高熵合金在室温及900℃下的摩擦磨损性能[J]. 摩擦学学报, 2024, 44(3): 1−11. doi: 10.16078/j.tribology.2023005
WANG Shiwei, ZHOU Hui, XU Yingge, ZHANG Kaifeng, FENG Kai. Tribological Properties of CoCrFeNiWx High-Entropy Alloys at Room Temperature and 900 ℃[J]. Tribology, 2024, 44 (3): 1−11. doi: 10.16078/j.tribology.2023005
Citation: WANG Shiwei, ZHOU Hui, XU Yingge, ZHANG Kaifeng, FENG Kai. Tribological Properties of CoCrFeNiWx High-Entropy Alloys at Room Temperature and 900 ℃[J]. Tribology, 2024, 44 (3): 1−11. doi: 10.16078/j.tribology.2023005

CoCrFeNiWx高熵合金在室温及900℃下的摩擦磨损性能

Tribological Properties of CoCrFeNiWx High-Entropy Alloys at Room Temperature and 900 ℃

  • 摘要: 采用真空电弧熔炼技术制备了CoCrFeNiWx (x=0.25、0.5、0.75及1.0)系列高熵合金,研究了W元素含量对合金晶体结构、显微组织、力学性能以及室温与900 ℃摩擦学性能的影响. 结果表明:合金中W含量较低时形成单相面心立方(FCC)固溶体,W含量较高时会促进金属间化合物μ相的形成,随着W含量提升,合金显微组织由FCC胞状树枝晶(x=0.25)转变为FCC树枝晶及晶间层片状(FCC+μ)共晶组织(x=0.5、0.75),最后转变为FCC基体上分布的粗大树枝状μ相(x=1.0). 由于W元素的固溶强化及原位生成金属间化合物μ相的第二相强化作用,使合金的强度和硬度等力学性能显著增加的同时塑性降低. 在试验载荷为10 N,滑动速度0.3 m/s的测试条件下,CoCrFeNiWx系列高熵合金与Si3N4陶瓷球配副时的球-盘摩擦试验结果表明:W元素的添加显著改善了合金的室温耐磨性,但对摩擦系数的影响较小;而900 ℃摩擦时,摩擦表面形成的多元复合氧化物摩擦釉质层具有良好的减摩抗磨作用,特别是W元素氧化产生的WO3显著降低了摩擦系数,从而显著提升了合金的高温摩擦磨损性能. 本文中研究的系列高熵合金中,CoCrFeNiW0.75高熵合金室温下的屈服强度为863 MPa,抗压强度达1250 MPa,900 ℃仍能保持446 HV的硬度,并在室温及900 ℃下均具有良好的摩擦磨损性能,具有良好的工程应用前景.

     

    Abstract:
    In aerospace and aviation industry, there is an urgent need for the materials with good mechanical properties, wear resistance performance and self-lubricating properties at high temperatures. High entropy alloys (HEAs), also known as multi-principal element alloys are a kind of novel metal materials that contain five or more elements in near equiatomic proportions with four core effects: high entropy, sluggish diffusion, severe lattice distortion, and cocktail effects. Because of their unconventional structures, the HEAs exhibit excellent strength, hardness, fracture toughness, wear resistance and high temperature stability, all these advantages make HEAs have promising for high temperature applications in the field of aerospace and equipment manufacturing.
    In this study, in order to obtain a HEA with excellent mechanical properties and tribological properties, a series of CoCrFeNiWx (x=0.25, 0.5, 0.75 and 1.0) HEAs were prepared by vacuum arc melting. The effects of W content on the crystal structure, microstructure, mechanical properties and tribological properties of CoCrFeNiWx HEAs at room temperature as well as 900 ℃ were studied. The experimental results suggested that single-phase face-centered cubic (FCC) solid solution was formed in the alloy with low W content, and the intermetallic compound μ-phase was promoted when the W content was higher than x=0.25. With the increase of W content, the microstructure of the CoCrFeNiWx HEAs evolved from single-phase cellular dendritic FCC structure (x=0.25) to dendritic FCC plus interdendritic lamellar (FCC+μ) eutectic structure (x=0.5, 0.75), and then to coarse dendritic μ phase on FCC matrix (x=1.0).
    Due to the effect of solution strengthen of W atoms and the precipitation strengthen of the in-situ formed intermetallic compound μ- phase, the mechanical properties such as yield strength and compressive strength of the HEAs are significantly increased while the plasticity is decreased. The Vickers hardness of the CoCrFeNiWx HEAs were improved significantly with the increasing W content both at room temperature and 900 ℃, especially the CoCrFeNiW0.75 and CoCrFeNiW HEAs still maintained higher hardness at 900 ℃, which indicated that the addition of W was helpful to improve the high-temperature softening resistance of the CoCrFeNiWx HEAs.
    Ball-on-disk sliding friction and wear tests of CoCrFeNiWx HEAs coupled with Si3N4 ball were carried out under a contact load of 10 N and a sliding speed 0.3 m/s at room temperature and 900 ℃, the results showed the addition of W element significantly improved the room temperature wear resistance of CoCrFeNiWx HEAs, but made little contribution to the friction coefficient. At 900 ℃, the friction coefficients and wear rates of the CoCrFeNiWx HEAs was sharply reduced with the increase of W content, which was mainly attributed to the fact that the multi-component composite oxide glaze layer mainly composed of Fe2O3, CoO, Co3O4, Cr2O3, NiO and WO3 formed on the worn surface had a good friction reduction and anti-wear effect at high temperature, especially the WO3 played an important role in the reduction of friction coefficient. The detailed characterization of the worn surface revealed that abrasire wear and fatigue wear were the dominant mechanisms of CoCrFeNiWx HEAs at room temperature but oxidative wear at 900 ℃.
    Among these W contained HEAs studied in this paper, the CoCrFeNiW0.75 HEA had a yield strength of 863 MPa, a compressive strength of 1 250 MPa, and a hardness of 446 HV at 900 ℃, both good tribological and wear properties at room temperature and 900 ℃, which had a good prospect of engineering application.

     

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