Research and Development on Evaluation of Surface Damage and Performance of Gear Pairs under Extreme Environment

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To evaluate the tooth flank damage and the driving performance under extreme environments, a gear test rig employed in high vacuum was designed and developed. The tribological research was performed in high vacuum as well as under normal enrivonment and at high temperature. Friction and wear characteristics of fine ceramics at high temperature were elucidated with Sialon, Al_2O_3 and ZrO_2, which were the typical fine ceramics. The wear and suffing performance of the wear resisting steel (WRS), which was a newly developed steel, was examined. The friction and wear characteristics of WRS was superior and the electroless Ni-P alloy plated WRS had high scuffing capacity at high specific sliding, but the sulfurized WRS was not so improved. The influence of the surface modification treatment on the rolling contact fatigue and the scuffing capacity of rollers was examined. The rolling contact fatigue strength and the scuffing capacity of the electroless Ni-P alloy plated rollers were larger than those of the non-coated rollers and the improvement of scuffing capacity was remarkable at high specific sliding. Friction and wear characteristics of surface modified gears and rollers in high vaccum were examined by spur gear and two cylinder tests. In case of rollers the wear rate of electroless Ni-P alloy plating was larger than that of Sn plating, but in case of gear pair that was the other way about. In case of sulfurizing the initial friction coefficient was low and the torque loss was small under the low pressure where the wear of the sulfurized layr was small. The initial friction coefficient of the Sn plating increased under the low contact pressure, where wear particles were transferred onto the frictional surface, while the friction coefficient decreased, and the torque loss and the change of tooth profile were the smallest after the surface modified layr worn uniformly.