航空航天、高速列车、新能源汽车领域的快速发展对其核心部件材料提出了宽温域下同时具备优异的耐磨性能、润滑性能和力学性能的要求，零部件宽温域条件下的力学性能和摩擦学性能直接关系到机械装备的可靠性和稳定性。本文采用放电等离子烧结技术，设计三组不同的CoCrFeNi高熵合金(HEA)基自润滑复合材料，分别是：①添加Ag和Mo到HEA基自润滑复合材料中；②添加Ni/MoS₂、Ag和Cr₂O₃到HEA基自润滑复合材料中；③HEAMo_x-Ni/MoS₂-Ag-Cr₂O₃(x=0.2、0.5和1) 自润滑复合材料。采用扫描电子显微镜(SEM)、能谱分析仪(EDS)和X射线衍射仪(XRD)，研究各添加相对基体微观组织及物相组成的影响规律。利用硬度仪和万能力学性能试验机，阐明复合材料强韧化机理。使用高温摩擦磨损试验机开展复合材料宽温域的摩擦磨损性能研究，借助SEM、EDS和拉曼光谱(Raman)进一步分析磨损表面成分和结构，确定不同氧化物的形貌，结构和形成温度，揭示复合材料在不同温度下的摩擦磨损机制，最终获得25-800℃范围拥有宽温域自润滑的高熵合金基复合材料HEAMo₁-Ni/MoS₂-Ag-Cr₂O₃。具体研究内容及结论如下：

首先，添加Ag和Mo至HEA基体中并制备三种不同的自润滑复合材料。采用XRD、SEM和EDS分析复合材料的微观组织形貌和物相组成，结果表明HEA-Ag-Mo复合材料由HEA基体、组织结构单一的富Ag相和复杂的富Mo相组成。力学性能测试结果表明三种复合材料均有良好的塑性，塑性应变均超过45%，共同添加Ag和Mo提高了材料的硬度和强度，摩擦磨损实验表明Ag和Mo在提高HEA基体宽温域摩擦学性能方面起着互补的作用，特别是在800℃下，HEA-Ag-Mo复合材料具有较低的摩擦系数0.32和磨损率3.2×10^-5 mm³/N.m。Ag和Mo协同添加的润滑机理是，在常温条件下，富Ag相起到了润滑剂的作用，富Mo相改善了抗磨性能；在400℃时，扩散形成的细小Ag颗粒起到了减摩的作用；在800℃时，高温下摩擦化学反应形成氧化镍和钼酸银(Ag₂MoO₄)相，该釉层对HEA-Ag-Mo复合材料的高温摩擦学性能起着抗磨减磨的重要作用。

然后，添加Ni/MoS₂、Ag和Cr₂O₃至HEA基体并制备三种不同的自润滑复合材料。结合XRD，SEM和EDS分析材料的微观组织形貌和物相组成，得到复合材料由基体的FCC相、Ag相、Ni相、MoS₂相和Cr₂O₃相组成，添加相分布在HEA基体粉末的边界。力学性能测试结果表明Ni/MoS₂、Ag和Cr₂O₃的加入提高了材料的硬度和屈服强度，HEA-Ni/MoS₂-Ag-Cr₂O₃复合材料具有最高的硬度382 HV和屈服强度430 MPa，但其塑性应变仅为20%。摩擦磨损实验表明HEA-Ni/MoS₂-Ag-Cr₂O₃复合材料在宽温域范围内具有最小的摩擦系数，尤其800℃下的摩擦系数仅为0.42，同时较小的磨损率3.2×10^-6 mm³/N.m。在中低温条件下，Ni/MoS₂和Ag起到了润滑作用，Cr₂O₃提高了抗磨性；在高温时，由摩擦化学反应形成氧化镍和多种钼酸银(Ag₂MoO₄和Ag₂Mo₂O₇)相，该釉层对HEA-Ni/MoS₂-Ag-Cr₂O₃复合材料的高温摩擦学性能起着抗磨减摩的重要作用。

最后，制备不同Mo含量的HEAMo_x-Ni/MoS₂-Ag-Cr₂O₃(x=0.2、0.5和1)自润滑复合材料。结合XRD，SEM和EDS分析复合材料的微观组织形貌和物相组成，结果表明Mo含量为0.2时，复合材料由FCC相、Ag相、Ni相、MoS₂相和Cr₂O₃相组成，Mo含量为0.5和1时，含量的增加一方面促进了硬质σ相形成，另一方面由于Mo原子固溶产生了明显的晶格畸变。力学性能测试结果表明Mo原子的固溶强化作用和硬质σ相的第二相强化效果显著提高了复合材料的硬度，其硬度从432 HV增加到502 HV。摩擦磨损实验表明HEAMo_0.2-Ni/MoS₂-Ag-Cr₂O₃复合材料在宽温域范围内具有好的减摩性，800℃下的摩擦系数仅为0.23，三种复合材料在室温到800℃范围内的磨损率均低于10^-5 mm³/N.m，尤其是HEAMo₁-Ni/MoS₂-Ag-Cr₂O₃在800℃的磨损率仅为3.15×10^-6 mm³/N.m。在中低温条件下，Ni/MoS₂和Ag起到了润滑作用，Mo原子的固溶强化作用和硬质σ相提高了抗磨性，在高温下，Ni/MoS₂和Ag发生摩擦化学反应，磨痕表面由氧化镍相和多种钼酸银(Ag₂MoO₄、Ag₂Mo₄O₁₃和Ag₂Mo₂O₇)相组成，该釉层对HEAMo₁-Ni/MoS₂-Ag-Cr₂O₃复合材料的高温摩擦学性能起着抗磨减摩的重要作用。

The rapid development in the fields of aerospace, high-speed train and new energy vehicle has put forward the requirements of excellent wear resistance, lubrication and mechanical properties of its core components in a wide temperature range. The mechanical properties and tribological properties of parts in a wide temperature range are directly related to the reliability and stability of mechanical equipment. In this paper, three different groups of CoCrFeNi high entropy alloy (HEA) based self-lubricating composites are designed by discharge plasma sintering technology. They are as follows: (1) Add Ag and Mo to HEA matrix; ② Ni/MoS₂, Ag and Cr₂O₃ are added to HEA matrix. ③ HEAMo_x-Ni/MoS₂-Ag-Cr₂O₃(x=0.2, 0.5 and 1). The scan electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were used to investigate the effects of each additive on the microstructure and phase composition of the matrix. Using hardness tester and universal mechanical property tester, the strengthening and toughening mechanism of composite materials was elucidated. The high temperature friction and wear testing machine was used to study the friction and wear properties of composites in a wide temperature range. The wear surface composition and structure were further analyzed by SEM, EDS and Raman spectroscopy (Raman), and the morphologies, structures and formation temperatures of different oxides were determined, revealing the friction and wear mechanism of composites at different temperatures. Finally, HEAMo₁-Ni/MoS₂-Ag-Cr₂O₃, a high entropy alloy matrix composite with wide temperature range and self-lubrication, was obtained from 25 to 800℃. Specific research contents and conclusions are as follows:

Firstly, the addition of Ag and Mo prepared three different HEA-based self-lubricated composites. The microstructure and phase composition of the composites were analyzed by XRD, SEM and EDS. HEA-Ag-Mo consists of a single Ag-rich phase and a complex Mo-rich phase. The addition of Ag and Mo improves the hardness and strength of the materials. The friction and wear experiments show that Ag and Mo play a complementary role in improving the tribological properties of the HEA matrix in a wide temperature range, especially at 800℃.HEA-Ag-Mo has a low friction coefficient 0.32 and wear rate 3.2×10^-5 mm³/N.m. The lubrication mechanism of the synergistic addition of Ag and Mo is that, At RT, the Ag-rich phase acts as a lubricant, and the Mo-rich phase improves the anti-wear properties. At 400℃, the fine Ag particles formed by diffusion played a role in reducing friction. At 800℃ high temperature, nickel oxide and Ag₂MoO₄ phase are formed by tribological reaction. The glaze layer plays an important role in the high temperature tribological properties of HEA-Ag-Mo.

Then, Ni/MoS₂, Ag and Cr₂O₃ were added to HEA matrix and three different self-lubricating composites were prepared. The microstructure and phase composition of the material were analyzed by XRD, SEM and EDS, and the composite was composed of FCC phase, Ag phase, Ni phase, MoS₂ phase and Cr₂O₃ phase of the matrix. The addition phase was distributed at the boundary of the HEA matrix powder. The mechanical properties test results show that the addition of Ni/MoS₂, Ag and Cr₂O₃ improves the hardness and yield strength of the material. HEA-Ni/MOS₂-Ag-Cr₂O₃ composite has the highest hardness of 382 HV and yield strength of 430 MPa, but its plastic strain is only 20%. Friction and wear experiments show that HEA-Ni/MoS₂-Ag-Cr₂O₃ composites have the smallest friction coefficient in a wide temperature range, especially at 800℃, the friction coefficient is only 0.42, and the wear rate is 3.2×10^-6 mm³/N.m. Under medium and low temperature conditions, Ni/MoS₂ and Ag play a lubricating role, Cr₂O₃ improves the wear resistance; At high temperature, nickel oxide and a variety of silver molybdate (Ag₂MoO₄ and Ag₂Mo₂O₇) phases are formed by tribochemical reaction. The glaze layer plays an important role in anti-wear and anti-friction of HEA-Ni/MoS₂-Ag-Cr₂O₃ composites at high temperature tribological properties.

Finally, the preparation of different levels of HEAMo_x-Ni/MoS₂-Ag-Cr₂O₃(x = 0.2, 0.5, 1) self-lubricating composite materials. The microstructure and phase composition of the composite were analyzed by XRD, SEM and EDS. When Mo content is 0.2, the composite is composed of FCC phase, Ag phase, Ni phase, MoS₂ phase and Cr₂O₃ phase. When Mo content is 0.5 and 1, the increase of content on the one hand promotes the formation of hard σ phase. On the other hand, obvious lattice distortion occurs due to solution of Mo atom. The results of mechanical properties test show that the hardness of the composite is increased from 432 HV to 502 HV by Mo atom solution strengthening and the formation of hard σ phase. Friction and wear experiments show that HEAMo_0.2-Ni/MoS₂-Ag-Cr₂O₃ has good anti-friction property in a wide temperature range, and the friction coefficient at 800℃ is only 0.23. The wear rate of the three composites is lower than 10^-5 mm³/N.m at room temperature to 800℃. Especially, the wear rate of HEAMo₁-Ni/MoS₂-Ag-Cr₂O₃ at 800℃ is only 3.15×10^-6 mm³/N.m. At medium and low temperature, Ni/MoS₂ and Ag play a role in lubrication, Mo atom solution strengthening and hard σ phase improve the wear resistance, at high temperature, Ni/MoS₂ and Ag friction chemical reaction, The grinding surface is composed of nickel oxide phase and a variety of silver molybdate(Ag₂MoO₄, Ag₂Mo₄O₁₃ and Ag₂Mo₂O₇) phases. The glaze layer plays an important role in the high-temperature tribological properties of HEAMo₁-Ni/MoS₂-Ag-Cr₂O₃.