Page 129 - 《摩擦学学报》2021年第6期

914 摩 擦 学 学 报 第 41 卷

Therefore, in this study, a new type of CoCrFeMoNiC x MEAs with low cost and good performance has been designed
and prepared. The design strategies of the MEAs were as follows: firstly, in order to achieve low-cost, the Fe content of
the MEAs was more than 60% and the total content of Co, Cr, Ni and Mo was less than 40%; secondly, for improving
the strength and the hardness of the MEAs, C was used for interstitial solution strengthening. The CoCrFeMoNiC x (x=0,
1, 2, 3, 4 and 5) MEAs were prepared by vacuum induction melting technology, and the effects of carbon content on the
microstructures, mechanical and tribological properties of the MEAs were systematically studied.
The CoCrFeMoNiC x MEAs with different C content mainly consisted of BCC phase. The lattice constant of the
MEAs was increased by the interstitial solution of C, which caused the diffraction peaks shift to small angles in XRD
spectrum with increase C content. The interstitial solid solution of C induced severe lattice-distortion in BCC phase,
which could effectively improve the mechanical properties of the MEAs. In the MEA without C, all the elements were
homogeneously distributed in the alloy. By comparison, when the C content was higher than 2%, small amounts of stripe
carbides were formed in BCC grains. With the increase of C content, the mechanical properties of the CoCrFeMoNiC x
MEAs were significantly improved by the combination of the interstitial solution strengthening of C and the second
phase strengthening of strip carbides. Among the CoCrFeMoNiC x MEAs, the MEA with 5% C content (C 5 MEA)
exhibited good comprehensive mechanical properties. The Rockwell hardness, yield strength, compression strength,
0.5
fracture strain and fracture toughness of the C 5 MEA were 34.1 HRC, 997 MPa, 2 088 MPa, 43.2% and 41.2 MPa·m ,
respectively.
The addition of C had little effect on the friction coefficient of the MEAs, which always remained between 0.58 ~
0.71. However, the addition of C could significantly improve the wear resistance of the MEAs. The wear rates of the
CoCrFeMoNiC x MEAs decreased obviously with the increase of C content. The wear mechanisms of the MEAs
included abrasive wear, plastic deformation and fatigue wear at room temperature. The good wear resistance of the
MEAs with high C content was mainly attributed to as follows. On the one hand, with the increase of C content, the
strength and hardness of the MEAs were improved obviously. It was difficult for the Si 3 N 4 counterpart to plough the
MEAs with high strength and hardness, and thus the effect of abrasive wear and plastic deformation were reduced. On
the other hand, the formation of the tribo-oxide films on the worn surface during sliding could isolate the direct contact
between the Si 3 N 4 counterpart and the MEAs, which played a key role in improving the wear resistance of the alloys.
Therefore, the wear resistance of the alloy was significantly improved with the increase of C content.
Key words: medium-entropy alloy; CoCrFeMoNiC x ; microstructure; mechanical properties; wear resistance

高熵合金作为近年发展起来的一类新型金属材 为563 MPa，断裂延伸率高达52%，并且该合金的强度
料，由于其相结构简单和力学性能优良，已成为材料 和塑性随温度的降低呈现升高的趋势，在77 K的低温
科学领域的研究热点之一 [1-4] . 截止目前，已开发出包 下其断裂应变接近70%，表现出良好的低温塑性和韧
括过渡金属高熵合金、难熔高熵合金和轻质高熵合金 性 [9-10] . 香港城市大学Liu等 [11] 研究了CoCrFeNiMo x
等 [5-6] 在内的数百种高熵合金. 根据混合熵(ΔS mix )的高 系列高熵合金，发现添加Mo元素析出的硬质σ相和
低，可将合金材料分为高熵合金(ΔS mix >1.61R)、中熵 μ相不仅没有脆化合金本身，反而极大提高了其力学
合金(0.69R≤ΔS mix ≤1.61R)和低熵合金(ΔS mix <0.69R) 性能，拉伸强度接近1 200 MPa，断裂延伸率达到19%.
三 大 类 . Gludovatz等 在 2016年 发 现 中 熵 合 金 然而，大多过渡金属高熵合金中含有的Co、Cr、Ni和
[7]
[8]
CoCrNi同样具有优异的力学性能，该合金由单一的面 Mo等元素较为昂贵，必然会限制其在工业领域的大
心立方(FCC)固溶体组成，具有高的固溶强化特征和 规模应用.
良好的延展性，其强度和韧性优于大多数常规合金和 基于此，在本研究中通过提高合金体系中廉价元
高熵合金. 中熵合金设计理念的提出为研制兼具良好 素Fe的含量，控制合金的制备成本，同时掺杂C元素进
强度、硬度、塑性和韧性的新型合金材料提供了全新 行间隙固溶强化，获得一种低成本、高性能的中熵合
思路. 金. 本文作者采用感应熔炼技术制备了CoCrFeMoNiC x
目前，以Co、Cr、Fe和Ni等为主要组分的过渡金属 (x=0、1、2、3、4和5)系列中熵合金，研究了C元素的掺
高熵合金是研究最多，也是相对成熟的高熵合金体系. 杂及其含量对合金微观组织和力学性能的影响及其
例如，最早报道的CoCrFeNiMn高熵合金是最为经典 作用机制，结合其显微组织和力学性能对摩擦磨损机
的合金体系，该合金由FCC相组成，室温下拉伸强度 理进行了探讨和分析. 在本文中对中熵合金力学性能