Effect of W Content on Tribological Performance of CrWN Coating under Dry Friction and Oil Lubrication Conditions

The effects of W content on the tribological properties of CrWN coatings under dry friction and PAO lubrication conditions were investigated by scanning electron microscope, X-ray diffractometer, nano-indentation tester, 3D profile-meter, and reciprocating tribometer. The results show that the microstructure of CrWN coatings prepared by ion beam assisted deposition is changed from dense columnar crystals to coarse columnar crystals and then to fibrous crystals. The hardness is first increased and then decreased with the increase of W content, and the maximum hardness is obtained when the W content is 9.96 at%. Under dry friction condition, the friction coefficients of CrWN coatings decrease first and then almost unchange with the increase of W content; however, under PAO oil lubrication condition, the friction coefficients of CrWN coatings gradually decrease with the increase of W content. Under dry friction, the introduction of W into CrN coatings at a low content will aggravate the wear of CrN-coated samples and their counterpart balls; but the wear resistance of CrN-coated samples and their counterpart balls are obviously improved by W doping under PAO oil lubrication condition.