Residual stress measurements of hot isostatically pressed silicon nitride rolling elements

Abstract

Ceramic materials used in rolling element bearing applications show some practical advantages over traditional bearing steels. Silicon nitride has been found to have a combination of properties suitable for certain high speed, low mass and high stiffness applications. The measurement of residual stresses is an important aspect of surface engineering to assist in correct design specification. An X-ray method was used since it is the only practical and non-destructible means of measuring residual stress of these materials at the pre-test and post-test stages. A pre-test survey of test sample residual stress within hot isostatically pressed silicon nitride supplied from selected manufacturers is presented. Experimental testing, surface examinations and residual stress measurements are described for case study silicon nitride failures. The role of the residual stress before and after fatigue testing is discussed. A modified four ball machine is employed to produce the accelerated rolling contact fatigue failures.