tribooxidation

Tribooxidation is the formation of oxide on a material’s surface as a result of tribological contact, such as sliding or rolling. Mechanical energy, frictional heating, and the presence of oxidants (oxygen, moisture) promote chemical reactions that produce surface oxides during wear.

Mechanistically, local heating at asperity contacts elevates temperature and shear, accelerating oxidation. The resulting oxide can form as a thin adherent film, or as thicker scales, depending on temperature, time, oxide kinetics, and environment. Lubricants or debris can supply or alter the reactive species.

Oxide layers may be protective, reducing metal-to-metal wear by acting as a hard barrier, or they may be brittle and spall, generating third-body debris and increasing roughness and wear. Oxidation also alters friction by changing surface chemistry and real contact area.

Different materials form characteristic oxides: iron and steels form Fe oxide phases (FeO, Fe3O4, Fe2O3); aluminum forms Al2O3; titanium forms TiO2; stainless steels may develop Cr- and Fe- oxides. The oxide regime depends on temperature, oxygen partial pressure, humidity, and the presence of lubricants.

Assessment uses surface analysis (XPS, Auger, Raman) and cross-sectional microscopy to identify oxide phases and thickness. Tribooxidation influences wear and friction in bearings, gears, braking systems, and other sliding contacts; understanding it informs material choice and lubrication strategies to promote protective oxides.