Leakage currents accelerate surface degradation of metal contacts via small scale arcing across lubricating films, but recent observations suggest that metallic nanoparticle additives in lubricants may be useful to improve contact performance. These findings prompted a study that examined electrically induced surface pitting of steel contacts in the presence of several lubricating greases including some containing nanometer-sized colloidal silver (Ag) particles. Reciprocating rolling sphere-on-disk experiments were conducted under electro-tribological loads employing polyurea greases derived from mineral and synthetic base oils with and without additives. Friction forces and electrical resistance were monitored continuously during the tests; surface changes were characterized by means of optical spectroscopy, stylus profilometry, and scanning electron microscopy (SEM) including compositional analysis using energy dispersive spectroscopy (EDS). The observations demonstrate that surface pitting induced by arcing occurs mainly at the points were the rolling motion changes direction and that eroded metal is deposited along the wear grove. Micron-sized pits are formed which contain carbon and oxygen indicating that arcing causes decomposition of the hydrocarbon lubricants. Numerous findings indicate a significant inhibition of pitting is induced by the Ag nanoparticles; some greases containing other additives exhibit a similar, although less pronounced, effect.

漏电流通过润滑膜上的小规模电弧加速金属触点的表面退化，但最近的观察表明润滑剂中的金属纳米颗粒添加剂可能有助于改善接触性能。这些发现促使一项研究在多种润滑脂（包括一些含有纳米级胶体银（Ag）颗粒的润滑脂）存在的情况下检查钢触点的电致表面点蚀。使用源自矿物和合成基础油（含或不含添加剂）的聚脲润滑脂，在电摩擦负载下进行往复滚动球盘实验。在测试过程中连续监测摩擦力和电阻；通过光谱学、触针轮廓测定法和扫描电子显微镜 (SEM) 来表征表面变化，包括使用能量色散光谱 (EDS) 进行成分分析。观察结果表明，由电弧引起的表面点蚀主要发生在滚动运动改变方向以及被侵蚀的金属沿着磨损槽沉积的点处。形成微米大小的凹坑，其中含有碳和氧，表明电弧放电导致碳氢化合物润滑剂分解。大量研究结果表明，Ag 纳米粒子可显着抑制点蚀；一些含有其他添加剂的润滑脂也表现出类似的效果，尽管不太明显。