Rolling contact fatigue behaviour of heat resistant bearing steels at highoperational temperatures

An approach was made to estimate the endurance limit in rolling contact fat igue in dependence of the operational conditions for the bearing steels M50 (AMS 6491), M50 Nit (AMS 6278) and the nitrogen-alloyed Cronidur 30 (AMS 5 898) by investigating the changes in the residual stress profiles after 5 m illion cycles of over-rolling. Real main shaft bearings with a pitch diamet er of 168 mm have been tested. To simulate the heat generated in the turbin e engines even under boundary operational conditions oil inlet temperatures between 80 degrees and 210 degrees C have been applied, the rotational spe ed has been varied between 2500 and 14 000 r/min and the interference fit h as been changed to produce different hoop stress levels.