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 p ractical advantages over traditional bearing steels. The contribution of th is present study is to provide understanding of surface crack defect charac teristics and the subsequent rolling fatigue modes of failure. Surface defe cts such as pressing faults and ring cracks are characterised using light m icroscopy. Experimental bench testing using an accelerated rolling contact fatigue rig produces results which identify the relationship between fatigu e failure modes and surface defects. The rolling contact tests are performe d on silicon nitride/steel elements using a variety of lubricants. Ball sur faces are examined before testing using a dye-penetrant technique and light microscopy. Post-test surfaces and failures are examined using light and s canning electron microscopy. A model of surface crack propagation in lubric ated contact is described. The boundary element model is used to investigat e the growth mechanism of ring crack defects during rolling contact. (C) 19 99 Elsevier Science S.A. All rights reserved.