Water lubrication of silicon nitride in sliding
Water lubrication of silicon nitride in sliding
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DOI：
10.1023/b:tril.0000044489.44053.be
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发表时间：
2004-10-01
影响因子：
3.2
通讯作者：
Ives, LK
中科院分区：
文献类型：
--
作者：
Jahanmir, S;Ozmen, Y;Ives, LK
几项研究表明，自配氮化硅在水中的摩擦系数在一定的磨合期后从最初的高值降低到约0.002。由于磨损表面变得非常光滑，低摩擦归因于在界面处由薄水膜引发的流体动力润滑。混合润滑的可能性，即，还提出了通过水的流体动力润滑和由于在磨损表面上存在胶体二氧化硅而产生的边界润滑。我们的研究的目的是调查负载，速度和表面粗糙度的持续时间的磨合期的影响。结果证实，当形成足够尺寸的磨痕以降低接触应力时，在磨合期之后获得低摩擦系数。在摩擦系数相当高的磨合期内，对于更光滑的表面以及更高的负载和速度，磨合期较短。发现低摩擦行为是不稳定的，并且偶尔观察到高摩擦尖峰。磨痕和磨痕表面含有一系列平行于滑动方向的条纹，表现出塑性变形、分层和断裂。表面膜破裂可能会形成与高摩擦尖峰相关的条纹。虽然这些结果与提出的流体动力润滑或混合润滑的机制是一致的，但有人提出，低摩擦行为也可能与覆盖有氢封端的氧化物膜的两个硬的弹性变形表面之间的基本相互作用有关。
Several studies have shown that the coefficient of friction of self-mated silicon nitride in water decreases from an initially high value to about 0.002 after a certain run-in period. Since the worn surfaces become extremely smooth, the low friction is attributed to the initiation of hydrodynamic lubrication by a thin water film at the interface. The possibility of mixed lubrication, i.e., hydrodynamic lubrication by water and boundary lubrication due to the presence of colloidal silica on the wearing surfaces, has also been proposed. The purpose of our study is to investigate the influence of load, speed, and surface roughness on the duration of the run-in period. The results confirmed that a low coefficient of friction is obtained following a run-in period when a wear scar of sufficient size is developed to reduce the contact stress. The run-in period, during which the coefficient of friction is fairly high, was shorter for smoother surfaces and at higher loads and speeds. The low friction behavior was found to be unstable and occasional high friction spikes were observed. The surfaces of the wear tracks and wear scars contained a series of striations parallel to the sliding direction and exhibiting plastic deformation, delamination and fracture. The striations that appeared to be associated with the high friction spikes, could form as a result surface film breakdown. Although these results are consistent with the proposed mechanisms of hydrodynamic lubrication or mixed lubrication, it is proposed that the low friction behavior may be also related to fundamental interactions between two hard and elastically deforming surfaces covered with hydrogen-terminated oxide films.