Interpreting the Effects of Interfacial Chemistry on the Tribology of Diamond-Like Carbon Coatings against Steel in Distilled Water

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Three commercially available Diamond‐Like Carbon (DLC) coatings were investigated to help understand the dynamics of transfer layer formation and decay, when sliding against AISI 52100 steel balls in distilled water. Optimum tribological behaviour was observed during interfacial sliding between the transfer layer and DLC coating. Alternatively, shear of the carbonaceous transfer layer from the contact region resulted in growth of an iron oxide layer comprised of magnetite, maghemite and hematite, as identified by Raman spectra. Three‐ body abrasive wear involving iron oxide wear particles explained the high wear rate of the DLC coatings in the case of shear. Friction was controlled by the formation of a transfer layer, reducing adhesive interactions between surfaces. Subsequently, a gradual increase in friction was observed, and suggested to relate to an increase in the shear strength of the transfer layer due to adsorption of oxidative species. This was modelled using the Elovich equation for gas adsorption kinetics.