Observation of Surface Deformation of SUJ2 Plate Thrust Bearings Under High Pressure Loads

SUJ2 is often used as bearing steel. Flaking of the bearings is caused by rolling contact fatigue. In the present work, the rolling contact fatigue tests of SUJ2 were carried out under high surface pressures of 5.30, 6.27, and 7.00 GPa. 5.30, 6.27, and 7.00 GPa were for 1310.2 N (eleven balls), 6502.0 N (three balls), and 9061.7 N (three balls), respectively. Their theoretical values of contact radius ‘a’ were 343.6 µm (5.30 GPa), 406.3 µm (6.27 GPa), and 453.9 µm (7.00 GPa). Three specimens were made for each pressure before RCF tests. After the RCF tests, specimens were not broken under 5.30 GPa. Two specimens were broken, but one of them was not under 6.27 GPa. Under 7.00 GPa, all three samples were broken. We measured roughness, width, and depth of contact track after the RCF tests. Ra values under 5.30 GPa at 1.2 × 107 cycles are less than 1.0 µm. Ra values under 6.27 and 7.00 GPa were less than 4.5 µm. Depth of contact track was approximately 5–15 µm. It was concluded that there are little differences between theoretical contact conditions and empirical features.