On the Relationship of Magnetic Response to Microstructure in Cast Iron and Steel Parts

Nondestructive eddy current technique has long been used to detect discontinuities in materials. However, recently, its application has been extended to characterize materials' microstructure and properties. In the present article, four mild carbon steel bars with different chemical compositions (AISI 1015, 1035, 1045, and 1080) were obtained in annealed condition. Besides, to determine the effect of microstructure, six ductile cast iron bars with the same chemical composition and different pearlite contents were prepared. The pearlite percentage and estimated hardness values were determined by eddy current nondestructive technique, and the results were compared with the data obtained from conventional metallographic and hardness testing methods. The results indicate that the eddy current is a sensitive comparative technique to detect the microstructure (directly) as well as the mechanical (indirectly) changes of mild carbon steel and ductile cast iron parts.