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.