The Rolling Contact Fatigue of PVD Coated Spur Gears

The aim of the study was to investigate the resistance to rolling contact fatigue of a-C:H:W and MoS2/Ti coated gears. The investigation of rolling contact 'fatigue was realised by means of a gear test rig using FZG PT C/10/90 pitting test. Four material combinations of gears were tested: wheel and pinion uncoated, wheel and pinion coated, wheel coated and pinion uncoated as well as wheel uncoated and pinion coated. The tests were performed using for lubrication mineral gear oil of API GL-5 performance level and 80W/90 viscosity grade. The results indicate that for the coated/coated pair (wheel and pinion coated) and uncoated/coated pair (uncoated wheel and coated pinion) a significant decrease in the fatigue life compared to the uncoated gears was obtained. The best results were obtained in the case of the coated/uncoated pair (a-C:H:W coated wheel and uncoated pinion) - even fourfold increase in the fatigue life was observed. This shows a very high potential of application of PVD coatings for gears.