Hard turning and grinding are finishing processes for the manufacture of precision components, such as bearings, gears and cams. However, the effects of distinct surface integrity by hard turning versus grinding on rolling contact life are poorly understood. Four representative surface types were prepared: as‐turned, as‐ground, turned and polished and ground and polished. Surface integrity was characterized by surface topography, microstructure and micro/nanohardness. Fatigue tests were performed with an acoustic emission sensor and the signal processing software. The surface topographies show that skewness of the as‐ground surface is much more negative than the as‐tuned one while other surface parameters are equivalent. The turned surface has a thicker strain hardened zone and a thinner thermal affected zone than those of the ground one. The ground surface has higher micro‐ and nanohardness on surface and in the subsurface than the turned one. The amplitude of acoustic emission signal is the most stable and sensitive signal to fatigue failure. The turned surface may have a longer life (> 84%) than the ground one with equivalent surface finish. The fatigue lives of the bearing assembly are nearly identical for the turned surface versus the polished surface and the turned polished surface versus the ground and polished surface. In addition, polishing may not necessarily improve fatigue life of the machined surface, but increase bearing assembly life as much as 40%.
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Warren et al. (2007) studied this question.
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