Roller burnishing of hard turned surfaces

In a hard roller burnishing operation, a hydrostatically borne ceramic ball rolls over the component surface under high pressures. The roughness peaks are flattened and the quality of the workpiece surface is improved. When combined with hard turning, this process provides a manufacturing alternative to grinding and honing operations. The studies determined optimum working parameter ranges. Parameter settings were shown to be noncritical in this process, since constant surface qualities were attainable over wide setting ranges. A second phase of the studies examined the improvements obtained for various original roughnesses. Reductions of 30 to 50 % in mean peak-to-valley height R-z are, for example, achievable, depending on the original roughness. Structure analyses and residual stress measurements were used to examine the effects of the process on the workpiece surface zone. Hard roller burnishing transforms tensile residual stresses present in the surface zone after hard turning into compressive residual stresses. Hard roller burnishing has no effect on the formation of white layers in the surface zone. (C) 1998 Elsevier Science Ltd.