Comparative study on the load carrying capacities of DLC, GLC and CrN coatings under sliding-friction condition in different environments

DLC, GLC and CrN coatings of different thicknesses were prepared by PVD technology using their respective mature process parameters. Field emission scanning electron microscope (FESEM), laser confocal microscopy, and Raman spectrometer were used to analyze the morphologies and microstructures of the coatings. Nanoindentation measurements and scratch tests were executed to characterize mechanical properties. The load carrying capacities of these coatings in ambient air, distilled water and oil environments were investigated by a reciprocating tribometer with gradually increasing applied load. Results show that the CrN(2 h) coating has the best load carrying capacity in ambient air and base oil, the GLC coating possesses the best load carrying capacity in distilled water. The DLC coating exhibits lower friction when it survives under low load. The different load carrying capacities of these coatings under sliding-friction condition are closely related to their surface roughness, coating thickness and mechanical properties.