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 a round the coercive force. The apparatus is based on the detection of the vo ltage induced in a coil using a lock-in amplifier tuned to the exciting fre quency. Results obtained for the first harmonics and Vickers hardness on th e aged samples show that the peak interval of the first harmonics (PIFH) an d Vickers hardness decrease as ageing time increases. The correlation betwe en 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. (C) 2001 Elsevier Science B.V. All rights reserved.