Nondestructive evaluation of aged 1Cr-1Mo-0.25V steel using first harmonics

We present a new procedure to evaluate the first harmonics in a 1Cr-1Mo-0.25V steel. 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 a frequency close to the exciting one. Results obtained for the first harmonics and Vickers hardness on the annealed samples, show the peak width of the first harmonics and Vickers hardness decreased as aging time increased. The correlation between Vickers hardness and the peak width of the first harmonics could be evaluated nondestructively.