Physical-chemical interactions between DLC coatings and additivated lubricants

全球对全球变暖威胁的认识和减少温室气体排放的需求导致对摩擦学系统能效的要求不断提高。在机械零件上沉积类金刚石碳膜(DLC)是提高传动系统效率的一项重要技术，因为它在摩擦学接触中具有良好的摩擦磨损性能。因此，全润滑条件下碳基涂料的应用日益受到人们的关注。对于在润滑条件下的摩擦学应用，必须考虑碳基涂层表面与润滑剂之间的相互作用。这是一个特别有趣的研究课题，因为工业上使用的润滑剂通常是为与未涂覆的铁基材料接触而开发的。在这方面，必须指出，与润滑剂及其添加剂的摩擦化学反应导致摩擦化学层的形成，不能像在铁基表面那样在类金刚石碳涂层上发生。这直接导致了研究的需要。IOT和FZG的这项联合研究计划的目的是研究在边界摩擦和混合摩擦以及弹性流体动力润滑(EHL)条件下类金刚石碳涂层梯度碳化锆(ZrCg)与添加剂润滑剂之间的物理和化学相互作用。作为第一步，将采用中频磁控溅射(MFMS)方法沉积类金刚石涂层。在此之后，将使用销盘式摩擦试验机、双盘式摩擦机和齿轮效率试验台进行摩擦学模型试验，并使用不同的标准润滑剂和添加剂组合。在摩擦学试验的基础上，应用聚焦离子束/扫描电子显微镜、二次中性质谱仪和显微拉曼光谱等综合物理化学分析手段，研究碳基涂层与润滑剂/添加剂在润滑条件下的摩擦学接触过程中的物理化学相互作用。深入了解DLC涂层摩擦化学反应层的形成和组成机理，将有助于理解DLC涂层在润滑条件下的摩擦学行为。

The worldwide awareness of the threat of global warming and the demand for reduction of greenhouse gases result in continuously rising demands on energy efficiency of tribological systems. An important technology for efficiency improvement of drive systems is the deposition of diamond-like carbon coatings (DLC) on machine elements due to their favorable friction and wear behavior in tribological contacts. Therefore, the application of carbon based coatings under full lubrication is increasingly coming into focus. Regarding tribological applications under lubricated conditions, interactions between carbon based coated surface and lubricant have to be taken into consideration. This is especially an interesting research topic, as the industrially used lubricants are usually developed for the application in contact with uncoated iron based materials. In this regard, it must be noted that tribo-chemical reactions with lubricants and their additives, which leads to the formation of a tribo-chemical layer, cannot occur on diamond-like carbon coatings as on iron based surfaces. This leads directly to the need for research. The aim of this joint research proposal of IOT and FZG is to investigate physical and chemical interactions between the diamond-like carbon coating graded zirconium carbide (ZrCg) and additivated lubricants under boundary and mixed friction as well as under elastohydrodynamic lubrication (EHL) conditions. As a first step, the diamond-like coating ZrCg will be deposited by means of middle frequency magnetron sputtering (mfMS). After that tribological model tests using a pin-on-disc-tribometer, a twin-disc tribometer and gear efficiency test-rig will be carried out with different combinations of standard lubricants and additives. Basing on tribological tests, the application of comprehensive physical-chemical analytics as Focused Ion Beam/Scanning Electron Microscopy, Secondary Neutral Mass Spectroscopy and Micro Raman Spectroscopy will be used to investigate physical and chemical interactions between the carbon based coating ZrCg and lubricants/additives in tribological contacts unter lubricated conditions. Gaining valuable insights about the mechanisms govern the formation and composition of tribochemical reaction layers on DLC coating will make a valuable contribution to understanding the tribological behavior of DLC coatings unter lubrication.