Characterisation of work-hardening in Hadfield steel using non-destructive eddy current method

It is accepted that work-hardening of Hadfield steels during plastic deformation results in the formation of mechanical twinning, which, in turn, varies the mechanical properties up to a certain depth below the surface. In this research, considering the necessity of applying non-destructive evaluation (NDE) methods for inspecting microstructure and mechanical properties, eddy current technique has been employed to characterise the work-hardening of the Hadfield steel subjected to hammering treatment. The microstructures of the specimens subjected to a various amounts of work-hardeningwere characterised using optical and scanning electron microscopes as well as X-ray diffraction analysis. The hardness profiles were also plotted to measure the hardened depth due to the amount of hammer impacts. It was found that an increase in mechanical twinning which is the main cause of material work-hardening increases the hardness at the surface and depth of the specimens. Evaluating the relationships of hardened depth and surface hardness with eddy current outputs proved the applicability of the proposed NDE method to characterise the work-hardening of the Hadfield steel in relation to the amount of its plastic deformation.