A model for single asperity perturbation on lubricated sliding contact with DLC-coated solids

• A simplified numerical model for complex lubricated contact condition is proposed.
• We define a lubricant normal behavior based on EHD approximations.
• Taking into account the lubricant significantly decrease the calculated asperity load.
• The asperity load highly depends on its dimension and on the coating properties.
• Standard scratch tests can be non-representative of the actual scratch conditions.

In lubricated sliding contact systems with DLC coated solids, recent studies have shown that DLC coatings are highly sensitive to asperities breaking through the lubricant film within the contact area. Those asperities produce damages similar to those obtained from scratch tests, from where coating delamination can initiate and propagate. To better understand the link between scratches and coating delamination, endurance tests can then be performed on coating with controlled initial scratches. To ensure the scratches’ representativity with respect to the actual asperities’ contact condition, one has to estimate the load transmitted by such asperities as well as the induced perturbation on surface and subsurface stresses. In this paper, a simplified numerical model corresponding to such problems is presented. It is consistent with elasto-hydrodynamic (EHD) lubrication approximations and can be used on coated or uncoated systems. As a simplified model, it can be run quickly on multiple configurations, enabling the creation of representative scratch maps for the given lubricated contact conditions.