Non-destructive characterisation of pearlitic steel microstructure at room temperature and in-situ microstructure development during heat treatment using electromagnetic sensors

Pearlitic steels are important engineering materials in various high-strength applications. Their mechanical properties are influenced by microstructure control using chemical composition and/or thermomechanical processing. In the current study, a novel, non-destructive technique is presented for the characterisation of key microstructure parameters that are essential for strength, both at room temperature and during dynamic heat treatment. The pearlite interlamellar spacing in a 0.81 wt% C steel has been accurately measured at room temperature using an electromagnetic (EM) sensor. Furthermore, the spheroidisation process in 100Cr6 pearlitic steel has been monitored at elevated temperatures. A strong linear relationship between the EM sensor signal and the pearlite interlamellar spacing is demonstrated, indicated by an R² value of 0.91. Additionally, the capability of this method to track the spheroidisation process in real-time during constant heat treatment offers potential avenues for process optimisation in pearlitic steels.