Effect of fracture properties and surface morphology on wear of DLC coatings at severe contact condition

The present study shows how the fracture properties and surface morphology of diamond-like carbon (DLC) coatings affect their wear properties. Nine types of DLC coatings with different carbonaceous structures and surface roughness were prepared. Fracture toughness was quantitatively evaluated from the crack length on the coatings. Subsequently, wear tests were conducted under boundary lubrication to evaluate the wear properties. The results showed that the wear rate of DLC coatings with rough surfaces decreased with increasing fracture toughness, while that of smooth DLC is independent of fracture toughness. In the DLCs with rough surface, it was found that brittle fracture occurred, and the fracture significantly increased the wear rate. Additionally, the ratio of the stress intensity factor to the fracture toughness value (K/KIC) was presented, showing comprehensive wear behaviors.