Observation of Subsurface Cracks on Flat PEEK Race-Alumina Ball Bearing in Water under 1700 N at 1000 rpm

Polymers have features of low friction coefficient, chemically resistant, corrosive resistant, and non-conductive. Hence, many tribology productions of polymers such as bearings, gears, and rollers are developed. However, the mechanism of failure such as rolling contact fatigue has not been explained clearly. In recent studies, the observation of subsurface crack growth was important for understanding the failure mechanisms of the polymer ball bearings in water lubrication. In this research, we conducted overall cross-sectional observations to investigate the growth behaviour of subsurface cracks. The cross-sectional areas of the failure were observed. Moreover, we focused on the crack length, depth, angle and direction of propagation of the subsurface cracks. We concluded that as the distance of crack location from the centre of the contact track increased, the depth and length of the subsurface cracks increased. Most of the subsurface cracks propagated from the inner and outer areas toward the centre of the contact track.