White layers and thermal modeling of hard turned surfaces

White layers in hard turned surfaces are identified, characterized and meas ured 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 sour ce problems (J.C. Jaeger, Moving source of heat and the temperature at slid ing contacts, in: Proceedings of the Royal Society, NSW, vol. 56, pp. 203-2 24) is applied to simulate the temperature field in machined surfaces and t o estimate white layer depth in terms of the penetration depth for a given critical temperature. The analysis shows good agreement with the trend in e xperimental results. White layer formation seems to be dominantly a thermal process involving phase transformation of the steel, possibly plastic stra in activated; flank wear land rubbing may be a primary heat source for whit e layer formation. A strong material dependence of surface alteration is al so observed. Published by Elsevier Science Ltd.