Coating sensing strategy for understanding the governing factors of tribofilm growth on diamond-like carbon

Tribofilms formed on coating surface can replace the original surface materials and dominate the final tribological behaviors. In-situ identification techniques of additive-derived tribofilm significantly contribute to understanding the tribo-chemical reaction mechanisms between additives and coatings. Here, a Raman-based profilometry was employed for in-situ identifying tribo-chemical products formed on a-C:H surface based on their distinct optical properties. By combining diverse characterization techniques, the effectiveness of Raman-based method was verified, and a surface-dependent tribofilm growth mechanism was proposed. It is suggested that the tribo-chemical reaction between additive-derived tribo-products and a-C:H is mainly governed by the Lewis acid-base property of coating surface under low contact pressure and temperature condition, highlighting the critical role of chemical property of coating surface in initiating tribofilm growth.