Effect of Austenizing Temperature on High-Carbon Steels and Its Characterization by Eddy Current Nondestructive Technique

The objective of this study is to investigate the effect of austenizing temperature on high-carbon steels. Two types of steels, i.e., AISI-440C and AISI-A2 were selected in this regard. Specimens of these steels were austenized from 950 to 1250°C and then air-cooled; this resulted in major microstructural changes in the specimens. These microstructural changes altered the electrical resistivity and magnetic permeability of the materials. XRD studies revealed that about 80% austenite formed when the subject steels were heat-treated to 1200°C. Eddy current technique was applied for the assessment of these microstructural changes, which influence the eddy current response in the coil. Similar hardness trend was observed for both steels. The magnitude of eddy current can be used to estimate the volume fraction of phases present in these steels. This study revealed that a good correlation existed between eddy current measurements and microstructural changes in these steels.