Tribological Film Formation on Hydrogenated DLC/Steel Contacts From Fully Formulated Automotive Lubricants

Tribological film formation from fully-formulated synthetic automotive lubricants on hydrogenated DLC/steel contacts was compared with that on steel/steel contacts. Four DLC coatings containing various metal dopants (W and Si) were evaluated. Lubricants formulated with organic friction modifiers performed better on DLC/steel than on steel/steel in both sliding and rolling/sliding contacts (lower friction and wear). In contrast, lubricants formulated with MoDTC friction modifiers had higher sliding contact friction on DLC/steel than on steel/steel. No evidence was observed for tribological film formation on the DLC surfaces.