Formation of tribochemical reaction layers on a metal modified amorphous carbon coating a-C:H:Zr (ZrCg)

The aim of this paper is to analyze the formation of tribochemical reaction layers on a metal and hydrogen containing diamond-like carbon (DLC) coating in tribological contacts using a molybdenum dialkyl dithiophosphate (MoDTP-) and zinc dialkyl dithiophosphate (ZnDTP-) formulated lubricant. Therefore the industrially relevant gear oil polyalkylene glycol (PAG) as well as the additives MoDTP, ZnDTP and anglamol 99, containing Sulphur and Phosphorus (S-P), were used as lubricant in pin-on-disc (PoD) tribometer tests. The study was conducted using the DLC coating a-C:H:Zr (ZrCg). Chemical analyses on the wear tracks of the DLC coated specimens prove the formation of tribochemical reaction layers. •The DLC coating assumes additive functions.•Detailed Raman analyzes of wear tracks on DLC coatings after tribological tests.•Tribochemical reaction layer formation due interaction lubricant, additive and DLC.•Relaxation of DLC coating by interaction with tribochemical reaction layer.