Affiliations: [a] General Testing Division, Thailand Automotive Institute, Muang, Samutprakarn 10280, Thailand | [b] Institute for Scientific and Technological Research and Services, King Mongkut’s University of Technology Thonburi, Bangmod, Thungkru 10140, Thailand
Correspondence:
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Corresponding author: Isaratat Phung-On, Institute for Scientific and Technological Research and Services, King Mongkut’s University of Technology Thonburi, 126 Prachautit Rd., Bangmod, Thungkru 10140, Thailand. E-mail: [email protected].
Abstract: This study presents an application of the swept-frequency eddy current (SFEC) technique for characterization of aging conditions of 5Cr-0.5Mo heat resistant steel by a U-shaped, eddy current probe. An optimal eddy current probe was established and employed to investigate the specimens under different simulated service conditions. Sweep frequencies from 500 to 10,000 Hz were generated to measure the impedance changes using a precision LCR meter. As results, the normalized impedances showed the highest differences in each aging condition at the frequency of 3,200 Hz. Microstructural observations were utilized to give details of the differences in microstructures among aged conditions, which related to the carbide precipitation characteristics of the specimens. In addition, a micro-hardness was tested on the carbide colonies in complement the aged conditions. The results showed that the hardness correlated well to the normalized impedances obtained from the swept-frequency eddy current testing.
