FATIGUE PREDICTION OF THIN HARD COATINGS ON THE STEEL RACES OF HYBRIDBEARINGS USED IN HIGH-SPEED MACHINE-TOOL SPINDLES

The rotational speed requirements of high speed spindles led to the de velopment of angular contact hybrid bearings with ceramic balls and PV D coated steel races. The present paper describes the determination an d verification of critical coating fatigue stresses as well as their a pplication in coating fatigue calculations of hybrid bearing steel rac es. The fatigue limits of low temperature deposited PVD coatings were determined by the application of the impact rest and its FEM simulatio n and validated through their successful application to the prediction of coating life in rolling contact fatigue tests of coated specimens. Furthermore, a computer program that performs the quasi-static simula tion of bearing operation yields the necessary kinematic and dynamic p arameters for a FEM simulation of the stress field occurring in coated rings. For the investigated bearings, an adequate fatigue performance of their coated races was computationally exhibited. The PVD coated h ybrid bearings illustrated the predicted behavior in long duration tes ts, conducted in full scale test rigs.