NDT assessment of a residual life of fatigued damage alloy 800H

In order to assess their potential for NDT purposes, the changes in resonance frequency, in specific electric conductivity, in U(ltra)-S(onic) velocity, in US-critical angle and in US-absorption are correlated with the hight temperature low-cycle fatigue damage and with the remainig life fraction of Alloy 800H. The fatigue damage is quantified in terms of the initiation and growth of surface microcracks by means of the replica method. The evolving dislocation and phase microstructures are characterized in a semi-quantitative way. Neither the US-velocities nor the US-critical angle are significantly influenced by the fatigue damage. The same holds for the specific electric conductivity. However, both the US-absorption and the resonance frequency show significant changes with increasing life fraction, which are suggested to be caused by the evolving dislocation microstructure and by surface cracking, respectively.