类石墨非晶碳膜与不同硅油构建的固-油协同润滑研究

Solid-Oil Synergistic Lubrication Constructed by Graphite-Like Amorphous Carbon Films and Different Silicone Oils

硅油由于具有良好的化学稳定性、黏温特性和耐高温等性能,在机械设备的润滑方面发挥了重要作用.但是在边界润滑条件下,硅油在常见金属摩擦副界面的摩擦系数较高且造成的磨损较大,润滑效果不理想.利用类石墨非晶碳与硅油构建固-油协同润滑体系,对比研究了氢离子注入改性前后的类石墨非晶碳膜(GLC)与不同基团封端硅油的固-油复合边界润滑条件下的摩擦学性能.结果表明:类石墨碳膜与硅油复合后表现出显著的固-油协同润滑效应,其摩擦系数低至0.02,磨损率低至5.3×10^(−8 )mm^(3)/(N·m).相比于注入改性的GLC膜,未改性GLC膜与含有极性基团封端的硅油复合表现出更低的摩擦系数.这可能主要源于未改性GLC膜的碳原子主要以sp^(2)杂化键存在,其π电子能够与硅油的极性基团产生偶极诱导作用,使油膜在摩擦界面吸附更为稳固.但是,注入改性的GLC膜由于力学性能的改善,其与多数类型的硅油复合后的抗磨损性能总体优于未注入的GLC膜.

Silicone oils have been widely applied for the lubrication of mechanical devices due to their high chemical stability,good thermal resistance and superior viscosity-temperature properties.However,the lubrication performance of the silicone oils is usually non-ideal for the metal such as stainless steel tribopairs under the boundary lubrication regime because of the high friction coefficient and severe wear.Recently,the solid-oil synergistic lubrication strategy of which thin solid film and coating materials commonly were used has been increasingly employed to develop superior lubrication technologies.Compared with the single oil lubrication and solid lubrication,solid-oil synergistic lubrication has a shorter run-in period,higher stability and lower wear resistance.Amorphous carbon coatings have attracted widely attention in the field of solid lubrication materials due to their high hardness,low friction,superior wear resistance and outstanding chemical inertness.Here,a solid-oil synergistic lubrication system was constructed by using the graphitelike carbon(GLC),a classic amorphous carbon with high fraction of sp^(2) carbon bonds,and silicone oils.The solid-oil lubrication behaviors of GLC films combining different groups of terminated silicone oils under boundary lubrication were comparatively studied to survey the effects of terminated group of silicon oils.The results showed that the graphite-like carbon films exhibited obvious solid-oil synergistic lubrication effects with silicone oils.And the performance of such solid-oil synergistic lubrication system was influenced by terminated group of silicon oils.Meanwhile,the effect of carbon bonds structure on the solid-oil synergistic lubrication behaviors were scrutinized by using different GLC films with and without hydrogen ion implantation which was a common technology of inducing the change of carbon hybridization of amorphous carbon films.The friction coefficient and wear rate of the solid-oil synergistic lubrication system were as low as 0.02 and 5.3×10^(−8) mm^(3)/(N·m)when silicon oil with the polar group of carbinol(hydroxy)was used.It was also found that silicone oils terminated by polar groups could be combined with non-modified graphite-like amorphous carbon to produce better lubrication performance compared with silicone oils terminated by non-polar groups.This might be attributed to the existence of rich sp^(2 )hybrid carbon bonds in original GLC films,and theπelectrons of sp^(2) carbon bonds could generate dipoles with the polar groups of silicone oil to form more stable thin oil films at the friction interfaces.It also should be pointed out that the hydrogen ion implantation did not be beneficial for the reduction of friction coefficient of GLC films when the silicone oils with polar groups were used since the sp^(2 )carbon decrease with the increase of hydrogen implantation.However,the implanted GLC films showed higher wear resistance,which could stem from the improvement of mechanical properties of the modified films.