Effect of Surface Morphology of Diamond-Like Carbon Coated on Pre-Structured Substrates on Tribological Behavior under Engine-Oil Lubricated Condition

摘要

In this study, we investigated tribological behavior of the “pre-structured DLC” coatings, which coated on the rough surface substrates treated by micro-shot peening, lubricating with the engine-oil containing MoDTC and ZnDTP additives. The coefficient of friction and wear for the pre-structured DLC were reduced effectively, in comparison with the equivalent DLC materials coated on the polished substrates. XPS analyses on the steel counterface suggested that the friction behavior and wear of DLC coatings were related to the tribo-chemical reactions in terms of the Mo-sulfides formation and the reduction of Mo-oxides, involving transformation and transferring of carbon. We concluded that the pre-structured DLC had the possibility of inhibiting the wear of DLC material, from increasing in the presence of MoDTC, as well as it could enhance the MoS_2 formation to generate low friction. We discussed that different tribochemical reactions occurred in boundary lubrication between DLC materials and additives, either positive or negative, depending on the surface roughness, hydrogen content and mechanical properties of DLC coatings.