The aim of this paper is to present the theoretical principles of two new technique propose by Fraunhofer Institute for Non-destructive Technique from Saarbrucken â Germany. The ultrasonic backscattering technique is a powerful tool for nondestructive determination of the hardening depth in introduction hardened components. It allows one to measure the depth of the heat affected zone because the welding procedure or the heat treatments. This technique can be applied to hardening depth in the range = 2 mm and the typical measuring accuracy is ± 0.4 mm. The advantages of this method is the on-line measurements and that is no special calibration required. The magnetic Barkhausen noise technique is based on the different microproperties of the structure of the ferromagnetic steel after a complete magnetisation. The signals are detected by a tape recorder heads or by small coils, which exhibit the voltage induced by the discrete change of the field orientation. If the interaction depth reaches deep enough, signals from different microstructure states hardened surfaces above, a tough ground material lead to a multipeak structure in M (H). Finally, the author presents some experimental results obtained during a shot practice stage at the Fraunhofer Institute for Non-destructive Technique.
