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

液体和固体形式的润滑广泛应用于机械设备中，目的是减少摩擦和磨损，从而提高部件的使用寿命。由于其对环境的不利影响和低蒸发点，在某些机械系统中有以固体润滑剂取代液体润滑剂的趋势。最近的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，每种方法减少摩擦的能力是有限的，因为表面纹理逐渐磨损，而在无纹理表面上，润滑剂倾向于逃离接触区域。本课题的重点是研究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，在各种条件下，包括：高温、潮湿、接触负荷和真空。选择电泳沉积（EPD）作为涂层技术，可以高精度地将多壁碳纳米管（CNTs）和洋葱样碳（OLCs）纳米颗粒均匀沉积在衬底上。通过结合这两种方法，可以克服各自的局限性，实现高效、长期的润滑。摩擦计测量将在最先进的设施中进行，以便评估润滑系统在不同环境中的摩擦行为。将分析其性能和磨损机制，并将其与二硫化钼和石墨等传统固体润滑剂进行比较。此外，还将对CNTs和OLCs的润滑性能进行评价和比较。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CNTs/OLCs的结构变化（即缺陷密度的变化）。最后，原子探针层析成像、HR-TEM和EDX将用于研究近表面微观结构的物理化学变化，如晶界氧化、碳化物形成、沉淀和碳分布。所获得的知识将是最相关的高效率和低能耗的工程系统的发展。

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.