Combining advanced carbon nanoparticle coatings and laser textured surfaces for enhanced lubricity

液体和固体两种形式的润滑广泛应用于各种机械设备中，目的是减少摩擦和磨损，进而提高部件的使用寿命。由于固体润滑剂对环境的有害影响和较低的蒸发点，在某些机械系统中有用固体润滑剂取代液体的趋势。最近一种减少摩擦的方法是通过直接激光干涉图案化(DLIP)引入定义良好的表面形貌。然而，每种方法的减摩能力都受到限制，因为表面织构逐渐磨损，而在无织构的表面，润滑剂往往会逃离接触区。本研究重点研究了一种新型固体润滑系统的摩擦学性能，该系统将碳纳米颗粒涂层结合在DLIP结构钢表面上，在各种条件下，包括：高温、湿度、接触载荷和真空。采用电泳法(EPD)作为涂层技术，可以将多壁碳纳米管(CNTs)和洋葱状碳(OLCs)纳米颗粒均匀沉积在基片上，且具有很高的精度。将这两种方法结合起来，可以克服各自的局限性，实现高效、长期的润滑。将在最先进的设备中进行摩擦仪测量，以评估润滑系统在不同环境中的摩擦性能。所产生的性能和磨损机理将进行分析，并与传统的固体润滑剂，如二硫化钼和石墨进行比较。此外，还对碳纳米管和有机碳纳米管的润滑性能进行了评价和比较。由此产生的磨损轨迹将通过拉曼光谱进行检测，以表征界面的摩擦化学变化和碳纳米管/有机碳纳米管的结构变化(即缺陷密度的变化)。最后，利用原子探针层析、高分辨透射电子显微镜和能谱分析技术研究了近表面微观结构的物理化学变化，包括晶界氧化、碳化物形成、析出和碳分布等。所获得的知识将对开发高效率和低能耗的工程系统具有极大的相关性。

Lubrication in both, liquid and solid forms, is used in a wide span of mechanical devices with the aim of reducing friction and wear and subsequently, improving the component’s duty life. Due to their detrimental impact on the environment and low evaporation point, there is a trend to replace liquid with solid lubricants in certain mechanical systems. A recent approach to reducing friction is the introduction of a well-defined surface topography by direct laser interference patterning (DLIP). However, the capability of each method to reduce friction is restricted, since surface textures are gradually worn off whereas on untextured surfaces the lubricant tends to escape the contact area.The present proposal focuses on the research of the tribological performance of a new solid lubrication system which combines carbon nanoparticle coatings on DLIP structured steel surfaces under a variety of conditions including: elevated temperatures, humidity, contact load and vacuum. Electrophoretic deposition (EPD) is chosen as the coating technique, allowing to homogeneously deposit films of multiwall carbon nanotubes (CNTs) and onion-like carbon (OLCs) nanoparticles onto the substrates with high precision.By combining both approaches, their individual limitations can be overcome and result in an efficient, long-term lubrication. Tribometer measurements will be conducted in state of the art facilities, so as to assess the frictional behaviour of the lubrication system in diverse environments. Resulting performance and wear mechanisms will be analysed and compared to conventional solid lubricants like MoS2 and graphite. Furthermore, the lubricating performance of CNTs and OLCs will be evaluated and compared. Resulting wear tracks will be examined by Raman spectroscopy to characterise tribo-chemical changes of the interface and structural changes of the CNTs/OLCs (i.e. change of defect density). Finally, atom probe tomography, HR-TEM and EDX will be used to investigate physico-chemical alterations in the near surface microstructure such as grain boundary oxidation, carbide formation, precipitation and carbon distribution. The acquired knowledge will be of utmost relevance for the development of high-efficiency and low energy consumption engineering systems.