The effect of bearing steel composition and microstructure on debris dented rolling element bearing performance

Because of continuous improvements in bearing steel cleanliness, surface damage created by debris has become more influential in determining the fife of rolling element bearings. The metallurgical structure of a bearing raceway can be modified to optimize strength and damage tolerance. The correct balance between raceway strength and damage tolerance can significantly improve bearing life in contaminated environments. Retained austenite is known to add a degree of damage tolerance to hardened bearing steel. Samples made of ASTM A295 52100 steel were heat treated to obtain increasing amounts of retained austenite. Indentations were placed into the steel sample surfaces using a Rockwell 3 ON Superficial Hardness Tester. These indentations were examined and measured using light interferometry. The changes in the dent morphologies with increasing amounts of retained austenite will be discussed. A test program has been developed to investigate the influence of microstructure on the life of debris dented rolling element bearings. Groups of 35 mm bore radial ball bearings were dented with either a Rockwell 30N Superficial Hardness Tester, or with hard powder metal particles. These bearings were then fatigue tested with uniform contact stress, speed and clean lubricant with a marginal lubrication film. The performance of different bearing steels and heat treatments were investigated, and test results from the two denting methodologies will be provided.