Estimation of microstructure, deformation and fatigue fracture in different steel grades using emission technique in Barkhausen effect

In this paper, use of Magnetic Barkhausen Emission technique for characterization of microstructures, deformation and fatigue damage in different steels is discussed. Based on the two stage magnetization process modeled by the authors, the size of the grain/lath and carbides in ferritic steels could be correlated with MBE parameters. The influence of morphology of cementite (lamellar and spheroidized) on the MBE behavior has been understood. Various stages of tensile deformation, viz. (i) perfectly elastic, (ii) micro-plastic yielding, (iii) macroyielding, and (iv) progressive plastic deformation in ferritic steels could be identified using the MBE parameters. The hardening depth and its quality with respect to the microstructure in induction hardened specimens could also be established using the MBE technique. MBE is found to be highly sensitive in detection of stress induced martensite in stainless steels with metastable austenite phase. Different stages of fatigue damage in 9Cr-1Mo steel, vez. (i) cyclic hardening, (ii) softening, (iii) saturation and (iv) crack initiation could be identified using the MBE parameters.