Rolling contact fatigue failure modes of lubricated silicon nitride in relation to ring crack defects

The use of silicon nitride applied to rolling element bearings shows some practical advantages over traditional bearing steels. The contribution of this present study is to provide understanding of surface crack defect characteristics and the subsequent rolling fatigue modes of failure. Surface defects such as pressing faults and ring cracks are characterised using light microscopy. Experimental bench testing using an accelerated rolling contact fatigue rig produces results which identify the relationship between fatigue failure modes and surface defects. The rolling contact tests are performed on silicon nitride/steel elements using a variety of lubricants. Ball surfaces are examined before testing using a dye-penetrant technique and light microscopy. Post-test surfaces and failures are examined using light and scanning electron microscopy. A model of surface crack propagation in lubricated contact is described. The boundary element model is used to investigate the growth mechanism of ring crack defects during rolling contact. (C) 1999 Elsevier Science S.A. All rights reserved.