tribolayer

Tribolayer, in tribology, denotes a thin film that forms on sliding surfaces during contact as a result of wear, adhesion, chemical reactions, and adsorption of species from lubricants or the environment. Tribolayers can be transient or persistent and may exist on one surface or be shared with the counterface as a transfer film.

They may be inorganic such as oxides, carbides, or nitrides; carbon-based films from graphite or diamond-like carbon; organic films from lubricants; or mixed composites. Formation mechanisms include tribochemical reactions with the environment, oxidation, sulfidation, adsorption of lubricant additives, and physical transfer of material from one surface to another.

Tribolayers typically range from a few nanometers to tens of nanometers in thickness, with properties such as hardness, shear strength, and adhesion that influence their behavior. They can reduce friction and wear by providing a low-shear interface or by protecting the substrate from direct contact. However, some tribolayers may spall, abrade, or change wear mechanisms if they are unstable or become excessively thick.

Characterization and applications: Tribolayers are studied with techniques such as electron microscopy, surface spectroscopy (XPS, Raman), atomic force microscopy, and ellipsometry. In engineering, tribolayers are formed intentionally through coatings and lubricant formulations to achieve boundary lubrication. They are central to engine oil additives, ceramic coatings, and wear-resistant surfaces.