METHOD AND DEVICE FOR MEASURING SURFACE-HARDENED LAYER

A method comprises a calibration curve creation step (S2, S3, S4) in which a calibration curve is created on the basis of hardened surface layer depth obtained by performing a destructive test on one of two samples in pairs, and at least propagation time of a first peak of a first wave of waveform of a signal outputted with the other in pairs in a non-destructive test, the samples in pairs being prepared such that carburization depth varies gradually from pair to pair, a waveform measurement step (S5) in which waveform of a signal outputted with a to-be-inspected piece is obtained, a propagation time obtaining step (S6) in which at least propagation time of a first peak of a first wave of the waveform of the signal outputted with the to-be-inspected piece is obtained, and a hardened layer depth estimation step (S7) in which the hardened surface layer depth of the to-be-inspected piece is obtained using the calibration curve, on the basis of the propagation time obtained with the to-be-inspected sample.