高真空下非晶碳基薄膜的长润滑寿命设计与可控制备

Amorphous carbon films were treated as a desiralbe solid lubricant materilas, due to its superior vacuum tribological properties. However, they were often easily worn out under high vacuum, and until now, the intristic failure mechanism was not still well understood. Recently, the wear lifetime did not meet the harsh requirements of high reliablity and long lifetime. As we known, the tribological properties of amorphous carbon films were closely related with the information of atomic scale that near the tribological contact interfaces. However,it was difficult observing the tribological behavior at the atomic scale, which was one of key bottleneck that limited its lifetime and reliablity. In this project, the first principles calculation and molecular dynamics simulation were due to their distinctive advantage in studying the atomic information, combining with the relation of stress and strain,were selected to investigate the intristic failure mechanism under high vacuum. Through composition design and micro-control of multilayer interfaces, the amorphous carbon films exhibited high hardness, low friction coefficient and superior anti-wear properties. The evolution of the composition and the microstructure of transfer film was revealed through the way of interfaces control, especially, we emphasize on the formation process of self-lubricant transfer film near the tribological interfaces. The lifetime extension and steerable fabrication of the amorphous carbon films could be ultimately achieved under high vacuum.

非晶碳基薄膜在高真空环境下具有优异的摩擦学性能，同时也是高真空下理想的固体润滑薄膜材料。但是该薄膜在高真空条件下摩擦过程中通常表现为瞬间突然磨损失效，且迄今为止，这种磨损失效机制仍不清楚，其磨损寿命无法满足高可靠和长寿命的苛刻要求。非晶碳基薄膜材料的摩擦学行为与摩擦接触界面处原子尺度的信息密切相关。然而在原子尺度下原位观察摩擦行为极为困难，也是制约其寿命和可靠性的关键瓶颈之一。本项目拟利用第一性原理计算和分子动力学方法在探究原子尺度信息方面的独特优势，从压缩应力应变关系入手，探索高真空条件下非晶碳基薄膜的本质失效机制。通过薄膜成分设计与多层界面微观调控制备出具有高硬度、低摩擦系数和优异抗磨性能的非晶碳基薄膜。通过摩擦界面调控，揭示高真空条件下的转移膜成分和微结构演化过程，尤其注重摩擦界面处具有自润滑性能摩擦膜的形成过程。实现高真空条件下非晶碳基薄膜的延寿与可控制备。

采用等离子体增强化学气相沉积系统制备了多层类金刚石薄膜，研究了沉积在高速钢、碳化硅和304不锈钢基底上的摩擦磨损性能，摩擦试验结果显示，沉积在高速钢上的类金刚石膜具有最低的磨损率，沉积在不锈钢基底上的类金刚石薄膜具有最低的摩擦系数。基于低磨损率，采用等离子体增强化学气相沉积系统在高速钢基底上沉积了氟、氟硫共掺杂类金刚石薄膜，系统研究了其在高真空下的摩擦磨损性能，研究结果显示，氟掺杂的类金刚石薄膜不仅具有较高的硬度，而且还具有较好的真空润滑性能。氟硫共掺杂类金刚石薄膜降低了膜层的硬度，虽然摩擦系数较低，但是润滑寿命较短。说明硫元素较氟元素更易影响类金刚石真空摩擦磨损性能。因此，采用第一性原理计算方法对硫掺杂类金刚石薄膜的真空润滑机理与失效机制进行了研究。研究结果显示：（1）金刚石界面的碳硫成键方式对其真空摩擦学性能影响较大，S-C-S构型由于其具有较大的界面吸引力导致高摩擦系数，S=C=S构型更易获得低摩擦系数。（2）亚表层S掺杂导致金刚石发生石墨化，在高真空下石墨化将导致膜层的快速磨损失效；表层S掺杂后，在滑动方向界面不但表现出低能垒，而且具有较低的粘着。本项目的研究很好的阐述了氟、硫、氟硫掺杂类金刚石薄膜在高真空下的低摩擦机理和失效机制。