Nanotribology is a sub-field of tribology, the study of friction. This science, or technology, describes and investigates how two surfaces behave when in relative motion, and what practical processes take place in the process. Essentially, it deals with friction and wear, and thus with the question of how wear can be prevented – or at least delayed in the long term – through the use of lubricants or other methods. In an industrial context, the focus is primarily on engines, gearboxes, roller bearings, guides and other moving machine components. Incidentally, the foundations of tribology can be traced back to the universal genius Leonardo da Vinci (1452–1519), who, amongst other things, studied the design of gearwheels and gearboxes during his lifetime.
Nanotribology investigates the effects of friction at the nanometre scale and at the atomic level. In addition to the development of suitable lubricants, the focus is on research into the selection of appropriate materials, as well as the treatment and coating of surfaces. Nanotribological principles are of particular interest to industry. They can help to increase the energy efficiency of machinery whilst simultaneously reducing the costs of materials and maintenance. This conserves vital raw material resources and reduces the burden on the environment. According to expert estimates, the global costs of lubricants and wear caused by friction and abrasion in machinery and gearboxes amount to approximately one trillion euros. Nanotribology can help to reduce these costs significantly.
A nanocoating alters the surface structure of a material at a molecular level. Upon contact with the substrate, the nanostructures form an ultra-thin, water- and oil-repellent layer that is firmly bonded to the surface. This prevents contamination from liquids, dust or other dirt. These properties are also known as the ‘lotus effect’. The coating can be applied to almost all materials and is particularly suitable for fine-pored materials and applications requiring high precision. A nanocoating can withstand temperatures of up to 350°C.
In principle, it is possible to apply a nano-coating to machine parts retrospectively, for example when overhauling a gearbox. However, it does not last as long as when applied directly during the production of the machine parts. The nanoparticles are suspended in a solvent. As soon as the solvent evaporates under the influence of heat and a supply of air, the nanoparticles form a web-like structure that is firmly bonded to the surface of the treated parts. The components of the coating have two effects: firstly, they protect the substrate from mechanical stress caused by frictional energy – for example, in heavily loaded gear designs – and, secondly, thanks to the additives incorporated, they ensure that foreign particles cannot become lodged.
The question of the cost of a nano-coating is, naturally, one of the most important for any technical manager or person in charge within a company. It is not possible to quote specific figures at this stage, as this depends on a wide range of individual factors – the type of machine or gearbox in question, the nature of the substrate, the daily operating time and the stress placed on the moving parts. In principle, however, it can be said that a nano-coating saves costs in the long term because it reduces the use of lubricants and extends the intervals between maintenance and repairs.
However, existing plant, machinery and gearboxes can also be protected against wear and tear by adding specific lubricant additives. A prime example is the unique product range offered by REWITEC®. Developed and manufactured in Germany, these products are compatible with all standard lubricants, but can also be supplied mixed into the customer’s own lubricant on request. As additives, they are added to the unit’s lubricant whilst it is in operation and are transported by the lubricant to metal surfaces subjected to friction. There, they utilise the friction energy and passivate the surfaces of bearings, gearboxes and similar units by depositing silicates, reducing surface roughness and thereby having a lasting and positive effect on the service life, energy consumption, operational reliability and performance of gearboxes and rolling bearings.
Alongside cost, the question of the impact on health and the environment is a key factor in the use of nanocoatings. According to current research, nanoscale coatings pose neither a health risk nor an environmental hazard. On the contrary, their beneficial properties actually improve workplace safety by reducing the susceptibility of machinery to damage.
