Effect of Different Transition Layer Structures on Cr-DLC Coating Properties

In order to improve the wear resistance of the parts under high load condition and prolong their service life, the composite process of cathodic vacuum arc ion plating and microwave plasma-assisted chemical vapor deposition was used to prepare Cr-DLC coatings on bearing steel surface with three transition layers, namely, no load layer, periodic(Cr/CrN) _xload layer and CrN_x gradient load layer, respectively.Raman spectroscopy and X-ray diffraction(XRD) were used to study the chemical composition and structure of Cr-DLC coatings under different Cr target currents.Scanning electron microscopy (SEM) was used to observe the microstructure of DLC coatings with three kinds of transition layers.The mechanical and tribological properties were evaluated by nano indentation, micro scratch and friction and wear tests.The results show that the Cr-doped DLC coating is a typical a-C:H film, which is embedded with Cr C grains, and its nanohardness can reach more than 30 GPa.The Cr-DLC coating with gradient CrN_x load layer has the best mechanical properties and wear resistance, and the strongest load capacity, with a binding strength of 52 N to the substrate material.and a wear rates of 13.8×10^-7mm³/(N·m) which is 1.5%that of the substrate material.The high-load friction test shows that Cr-DLC coating with gradient load layer can remain undamaged for 1 000 s under 800 N load, and Falex test shows that maximum load capacity of the coating reaches 5 000 N.