FeS/Cu-Bi无铅轴承材料可控制备及其摩擦学特性研究

To meet the increasing demand of Pb-free development, a noval research project is proposed to improve the friction and wear properties of the Pb-free Cu-Bi bearing materials. Using an in-situ synthesis technology, the interfacial bonding between FeS and the Cu alloy matrix are enhanced. Based on the excellent boundary lubrication performances of FeS, the anti-friction and adhesion-resistant synergetic effects between FeS and Bi are developed. The basic issues concerning the FeS synthesis, i.e., alloying design, atomization comminuting process, ball-milling reduction and etc, are studied to reveal the regularity and mechanism of the in-situ synthesis of FeS in the Cu alloy powders. The study is believed to establish a theoretical foundation for realizing the in-situ synthesis of FeS/Cu alloy powders and controllable fabricating the FeS/Cu-Bi bearing materials. Friction and wear properties of the FeS/Cu-Bi bearing materials under a boundary lubrication condition are systematically investigated to identify the synergetic mechanisms between FeS and Bi. Effects of liquid-solid lubricating film from transformation of FeS on slowing down its tendency to frictional surfaces, segregation and spalling process of Bi are discussed in terms of microscopic tests. In addition, effects of the tendency to frictional surfaces and segregation of Bi on formation and improvement of liquid-solid lubricating film are also analyzed. The relationships among the segregation effects of Bi and FeS and tribological properties of bearing materials are investigated to clarify the synergetic effects of FeS and Bi at anti-friction and adhesion resistance. The research results contribute to developing the new-type Pb-free Cu matrix bearing materials.

针对无铅化发展需求，基于原位合成技术改善FeS与基体界面结合，利用FeS良好边界润滑特性，使其与Bi协同发挥减摩、抗粘着作用，从而提高无铅铜基轴承材料摩擦磨损性能。进行合金化设计、雾化制粉、球磨还原等FeS原位合成基础问题研究，了解铜合金粉末中FeS原位合成规律与机制，为实现原位合成FeS/Cu合金粉末及其FeS/Cu-Bi轴承材料的可控制备提供理论基础。系统开展FeS/Cu-Bi轴承材料边界润滑条件下的摩擦磨损特性研究，明晰Bi、FeS协同作用规律；结合微观测试分析，探讨FeS转移形成液-固润滑膜对减缓Bi向摩擦表面趋附、析出与剥落进程的影响以及Bi的趋附、熔融析出对液-固润滑膜的形成与完善作用，建立Bi、FeS向摩擦表面的趋附、转移及其相互影响与轴承材料摩擦磨损特性间的关联，揭示Bi、FeS在减摩、抗粘着方面的协同作用机制。研究结果对发展新型无铅铜基轴承材料具有重要指导作用。

针对无铅环保化发展趋势，本项目以无毒低熔点金属元素Bi与FeS作为固体润滑剂取代铜铅轴承材料中的Pb，实现无铅化。通过机械合金化与粉末冶金成型方法优化制备FeS/Cu、FeS/Cu-Bi铜合金粉末及其复合材料，实现界面结合良好以及FeS、Bi弥散、均匀分布的铜合金粉末与复合材料的可控制备。开展不同工况摩擦磨损性能试验研究，系统地探讨FeS/Cu、FeS/Cu-Bi铜基复合材料的摩擦磨损特性；结合SEM、EDS、XPS、XRD等微观测试分析，揭示Bi、FeS的转移效应与减摩润滑膜特性，明晰FeS、Bi在减摩、抗粘着方面的协同作用机制。. 研究表明：(1)机械合金化使得FeS颗粒不断细化逐渐被“揉混”到Cu合金的结构内部或附着于铜合金颗粒表面，制备出FeS与Cu界面结合良好并均匀、弥散分布的混合粉末；由此制备的铜基复合材料界面结合好，FeS与Bi在铜合金基体中均匀、弥散分布。（2）含适量FeS的普通FeS/Cu材料具有较好的减摩耐磨性能， FeS固体润滑膜起到自润滑作用；FeS含量较高时，FeS颗粒易团聚，与基体界面结合差而易产生孔隙，材料强度、硬度下降，减摩耐磨性能变差；适量Bi的添加，有利于固体润滑膜的完整性与附着性，材料减摩耐磨性能提高。（3）适当时间机械合金化制备的FeS/Cu材料减摩耐磨性能明显改善；摩擦作用下FeS被挤出材料表面沿表面铺展或转移到对偶件表面形成润滑减摩膜，具有较好的减摩耐磨作用；机械合金化材料摩擦副表面形成的润滑膜与基体结合更加牢固，转移膜连续完整，减摩耐磨性能更好。（4）适当时间机械合金化制备的FeS/Cu-Bi材料摩擦学性能更优，材料中均匀、弥散分布的FeS、Bi有利于摩擦界面间固体润滑膜与润滑转移膜的形成和完善，FeS与Bi相互协同，固体润滑膜与润滑转移膜破损、脱落程度减轻而更加连续、致密和稳定，发挥良好的减摩自润滑作用。. 本项目揭示了Bi、FeS在减摩、抗粘着方面的协同作用机制，为发展新型FeS/Cu-Bi无铅铜基轴承材料提供理论基础，具有重要的理论研究意义。