Nondestructive evaluation of aged 1Cr-1Mo-0.25 V steel by harmonic analysis of induced voltage

We present a new procedure to evaluate degradation of 1Cr-1Mo-0.25 V steel using the first harmonics analysis of induced voltage. The method is based on the existence of the first harmonics in the differential magnetization around the coercive force. The apparatus is based on the detection of the voltage induced in a coil using a lock-in amplifier tuned to the exciting frequency. Results obtained for the first harmonics and Vickers hardness on the aged samples show that the peak interval of the first harmonics (PIFH) and Vickers hardness decrease as ageing time increases. The correlation between Vickers hardness and the PIFH could well be used to evaluate degradation of 1Cr-1Mo-0.25 V steel nondestructively. We compare PIFH with the various properties, for example, yield strength, tensile strength, and electrical resistivity