White layers in hard turned surfaces are identified, characterized and measured as a function of tool flank wear and cutting speed. White layer depth progressively increases with flank wear. It also increases with speed, but approaches an asymptote. A thermal model based on Jaeger? s moving heat source problems (J.C. Jaeger, Moving source of heat and the temperature at sliding contacts, in: Proceedings of the Royal Society, NSW, vol. 56, pp. 203-224) is applied to simulate the temperature field in machined surfaces and to estimate white layer depth in terms of the penetration depth for a given critical temperature. The analysis shows good agreement with the trend in experimental results. White layer formation seems to be dominantly a thermal process involving phase transformation of the steel, possibly plastic strain activated; flank wear land rubbing may be a primary heat source for white layer formation. A strong material dependence of surface alteration is also observed. Published by Elsevier Science Ltd.
Citation: International Journal of machine Tools and Manufacture
Pub Type: Journals
Hard turning, phase transformation, surface integrity, White layer