Tribological properties of DLC coating under lubricated and dry friction condition

Abstract Increasing demands on reducing abundant use of environmentally hazardous lubricants like chlorinated paraffin oil in production motivates extensive research on dry friction condition. However, the dry friction condition is not favourable, and it causes high friction and severe wear problems. This paper presents the tribological behaviour of a new hard coating, namely double-layer DLC/TiAlN, deposited onto the tool steel surface via a Physical Vapour Deposition (PVD) process. A pin-on-disk tribometer was used to study the long-term performance of DLC/TiAlN coated tool steel under lubricated and dry friction conditions. Surface damage after the experiment was observed by using a light optical microscope (LOM) and also, analysed by measuring wear scar profiles with a tactile roughness profilometer. The results were compared with uncoated tool steel. Based on the experimental result, applying the DLC/TiAlN coating to the tool steel surface has led to a significant reduction of friction and almost no wear scar was observed. The study proved that the DLC/TiAlN coating contributes to the better wear life of the tool steel, thereby improving the tool lifetime.