Dual-Sensor Electromagnetic Non-Destructive Testing for Material State Assessment of different Quenched and Tempered Steels in the Context of Circular Production

Electromagnetic non-destructive testing enables the assessment of material states in remanufactured ferromagnetic components in the Circular Factory. This study investigates the combined use of Magnetic Barkhausen Noise (MBN) and Eddy Current Testing (ECT) for the characterization of quenched and tempered CrMo steels with different carbon contents. All materials were fully martensitically hardened under identical austenitization conditions and tempered at different temperatures to generate distinct tempering states. Microhardness and surface residual stress measurements were used as reference methods to capture the coupled evolution of microstructure and stress during tempering. MBN and ECT measurements were performed under constant magnetization conditions to ensure comparability. The dual-sensor approach is evaluated for the classification of variations in the tempering states in Q&T steels relevant to remanufacturing. The results show distinct magnetic responses across tempering stages and carbon levels, indicating the suitability of combined MBN and ECT for robust inline monitoring of material states in circular manufacturing.