Evaluation of Fatigue Damage in Steels for Turbine Blades of Nuclear Plant by Magnetic Barkhausen Noise

In order to study the feasibility of the Magnetic Barkhausen Noise (MBN) technique for low cycle fatigue damage non-destructive testing (NDT) of X4CrNiCuMo steel for nuclear power turbine blades, the axial low cycle fatigue tests are carried out on X4CrNiCuMo steel specimens for turbine blades. The relationships between the MBN signal and microstructure, fatigue damage are studied by means of the MBN technique, transmission electron microscope (TEM) and metallographic microscope. The results showed that the MBN signal is very sensitive to low cycle fatigue damage. The MBN signal exhibits three main stages during the fatigue life. At the beginning of the test the MBN signal decreased rapidly, then it increased continuously and finally the signal suddenly dropped and then increased before failure. These successive stages can be associated to the typical stages of the low cycle fatigue life of metals such as cyclic hardening, cyclic softening and surface crack initiation and propagation. Thus, the MBN technique used in this paper can be an important reference for the fatigue damage assessment of turbine blades.