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

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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.