高熵合金增强铜基摩擦材料的界面调控及摩擦磨损机理研究

The friction material is very important to the safe operation of high-speed trains. Copper based friction materials have been widely applied due to their excellent comprehensive properties. However, the low interfacial bonding strength between the iron friction component and the copper matrix is a main constraint on the improvement of mechanical property and wear resistance. In view of this, FeCoNiCr high-entropy alloy particles with high wear resistance and copper intersolubility will be used as the friction component in this project. The high-entropy alloy powder with different Al+Ti content and double phase structure of FCC+BCC will be prepared by atomization technology. Copper based friction materials reinforced by high-entropy alloy will be prepared by powder metallurgy. The interdiffusion behavior of high-entropy alloy/copper couple will be studied, and the influences of powder properties and sintering process on the interfacial microstructure will be investigated. The mechanism of interfacial diffusion and the controlling mechanism of interfacial structure will be revealed. Moreover, the tribological properties of copper based friction materials will be investigated, establishing the correlation mechanism between high-entropy alloy properties, interface structure, system conditions and their tribological behavior. The microstructure evolution of the tribolayer will be revealed, and the friction and wear mechanism of the materials will be discussed. This study aims to provide theoretical and experimental proofs for the optimization of component design, enhancement of interface bonding and improvement of wear resistance of metal based friction materials.

摩擦材料对于高铁的安全运行至关重要，铜基摩擦材料因综合性能优异而被广泛应用，然而，铜基摩擦材料存在铁摩擦组元与铜基体烧结时无扩散而引起界面结合强度低的问题，严重制约其力学性能和耐磨性的提高。针对该问题，本项目提出采用高耐磨及与铜互溶的FeCoNiCr系高熵合金作为替代摩擦组元，拟通过雾化法制备Al+Ti含量不同FCC+BCC双相结构的FeCoNiCr系高熵合金粉体，并采用粉末冶金工艺制备高熵合金增强铜基摩擦材料。利用扩散偶技术研究高熵合金/铜基体界面元素的扩散行为，并研究粉末特性及烧结制度对界面结构的影响，揭示界面扩散传质机制与界面的调控机理。研究铜基摩擦材料的摩擦磨损性能，建立高熵合金摩擦组元特性、界面结构和系统条件与材料摩擦磨损行为的关联机制；探明摩擦层组织结构的演变规律，揭示摩擦材料的摩擦磨损机理。本研究将为金属基摩擦材料组元设计优化、界面结构强化以及耐磨性的提高提供理论和实验依据。

本项目针对高铁铜基摩擦材料存在铁摩擦组元与铜基体烧结时无扩散而引起界面结合强度低的问题，提出采用高耐磨及与铜互溶的FeCoNiCr系高熵合金作为替代摩擦组元，并采用粉末冶金工艺制备高熵合金增强铜基摩擦材料。本项目重要研究成果如下：1）探明在高达380 km/h的制动速度下对高速列车用铜基摩擦材料的磨损机制主要为氧化、剥层和剥落，磨损表面形成了由CuO和Fe2O3组成的约2 μm厚的纳米摩擦层，摩擦层相比原始表面具有更高的摩擦系数和耐磨性；2）揭示了高熵合金颗粒含量对铜基摩擦磨损性能的影响，添加FeCoNiCrAl高熵合金可显著提高铜基摩擦材料的摩擦系数、制动时间和吸收功；3）明确了高熵合金增强铜基摩擦材料中石墨与高熵合金的相互作用机理，CoCrFeMnNiCx具有FCC相和M7C3相组成的双相结构，碳化物提高了材料的硬度，CoCrFeMnNiC0.6具有最高的耐划伤性和耐磨性；4）建立了一种金属基复合材料的摩擦模型，成功地实现了复合材料摩擦表面润滑膜的覆盖率的定量表征，构建了摩擦系数、润滑膜覆盖率和润滑剂体积分数之间的关系。本研究将为铜基摩擦材料组元设计优化、界面结构强化以及耐磨性的提高提供理论和实验依据。截止目前，相关研究成果已发表标注基金资助的SCI检索论文10篇；培养硕士3人顺利答辩获学位，其中一篇获江苏省优秀专业学位硕士学位论文。