Surface Damage Under Extreme Conditions Existed in Aircraft Bearings

The extreme conditions of aircraft bearing steel M50 have been simulated by a two-disk test rig for investigating the surface damage of the ball/raceway contact surfaces. The slide/roll ratio are 0.12 and 0.15, correspondingly, the rolling speed are 43.2m/s and 49.5m/s. Aircraft engine oil 4050 as the supplied oil has been maintained at approximately 80°C in the tests. The ultimate Hertzian contact stresses of the surface damage obtained from the experiments are 3.8GPa in 0.12 slide/roll ratio and 3.5GPa in 0.15 slide/roll ratio. The damage mode is scuffing in 0.12 slide/roll ratio and it is oxidation, thermal fatigue and scuffing in 0.15 slide/roll ratio. Cracks in the contact areas originate from surface layer in the two slide/roll ratios.