Process-reliable adjustment of subsurface zone properties in the machining of high-strength and ductile steels using an adaptive manufacturing system

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Influencing the component subsurface zone is an elementary step in the manufacturing process. A combination of martensitic hardening of a subsurface zone and near-net-shape manufacturing represents a great potential to produce components with wear-resistant subsurface zones in an energy- and time-saving way. In the first funding period, an in-process soft sensor was developed and a deeper understanding of the transformation of austenitic microstructural constituents into martensite in a turning process was obtained. The aim of the proposed project is to investigate a dynamic feedforward loop for the process-safe adjustment of subsurface zone properties in the machining of high-strength and ductile steels by means of a deformation-induced austenite-martensite transformation. The combination of the geometry to be adjusted, the surface quality and the subsurface condition in the final machining by means of a multi-stage turning process is considered. On the basis of the detected initial state, the appropriate process parameters are set using the knowledge of the interrelationships of the phase transformation in the turning process in order to be able to generate the desired properties in the process. For this purpose, disturbing influences on the transformation of retained austenite during external longitudinal turning under cryogenic cooling in the process are evaluated. The setting of desired target states is based on the modelling of local transformation processes in a technological NC simulation, taking process-related uncertainties into account. With the help of a dynamic subsurface zone model, the prediction of the in-process eddy current characteristics is to be made on the basis of the subsurface zone microstructure. All elements are incorporated into the dynamic feedforward control for the targeted adjustment of the austenite-martensite transformation in the process. Research into the possibilities and limits of the method provides fundamental knowledge on the robustness of setting various specified target values by means of dynamic feedforward control.