纳米级稠化剂颗粒沉积膜在乏脂润滑中的作用机制研究

利用双光束干涉法对点接触区乏脂润滑成膜特性规律以及接触区附近润滑剂的微观迁移特性进行了观测.在试验条件下,接触区会经历充分润滑—乏脂—沉积膜润滑—分离油润滑等润滑状态.借助原子力显微镜,探测到沉积膜是润滑脂的稠化剂被碾压破碎而沉积在滚压轨道表面的一层纳米级颗粒薄膜;而分离油是在剪切过程中润滑脂内逐渐释放基础油.试验初始,接触区周围的润滑脂池因乏脂而迅速消失,但分离油会逐渐形成"第二相油池"以实现回流补给.沉积膜增大了基础油在滚动轨道表面的接触角,阻碍回流补给,但其会随运动逐渐磨损,此后分离油将进入接触区补充润滑膜.初步发现,当分离油不充足时,沉积膜有利于保护润滑轨道.

Mechanism of Nano-Scale Thickener Deposited Film in Starved Grease Lubrication

The behaviour of grease lubricating film in and the micro-scale migration of lubricant around a point contact under starved condition was studied by using relative optical interference intensity method. Under laboratory conditions, the contact would experience fully flooded phase - starving phase - deposited film lubrication phase - bled oil lubrication phase, successively. By using atomic force microscope (AFM), the deposited film was detected. It was formed from the sheared thickener debris during the rolling process and was of nano-scale. Infrared measurement showed that bled oil was basically base oil which was gradually squeezed out of the bulk grease during the operation. In the very beginning of the experiment, the initial grease reservoir around the contact was lost due to starvation, however, bled oil would reform a second phase oil reservoir to replenish the contact in the long run. Thickener deposited film would increase the contact angle of bled oil on the rolling surface which prevented bled oil from replenishing the rolling track. But this deposited film would be consumed during overrolling, after which the bled oil would reflow back to the contact. Evidence showed that the nano-scale thickener deposited film contributed to protecting rolling surface when bled oil was insufficient.