Influence of surface and material technologies on the loss of lubrication performance of gears

Enabling gears to withstand loss of lubrication in gearboxes without secondary oil supply systems can reduce weight and space demand and thus fuel consumption. This study investigates the potential of surface and material technologies on the loss of lubrication performance of gears. Thereby, superfinished, coated, and nitrided gears are compared to ground gears. Systematic experiments under loss of lubrication are performed at a back-to-back gear test rig with circumferential speeds of up to 20 m/s and Hertzian pressures in the pitch point of up to 1723 N/mm². Torque loss, pinion bulk temperatures, and tooth flank surface are analyzed. The results show that surface and material technologies can greatly influence frictional behavior and damage initiation of gears operating under loss of lubrication. With the materials and conditions tested, superfinishing yields to accelerated rise of frictional losses and thus scuffing. Coatings lead to significantly enhanced service life under loss of lubrication by friction reduction and scuffing avoidance.