Measurements of acoustic emission due to thermocycling of oxidized high temperature alloys

The ring down counts and energy of acoustic emission (AE) signals emitted during thermal cycling of oxidized IN-519, HASTELLOY X, and INCOLOY 800 H were measured. The HT alloys were oxidized in situ under a controlled oxidation potential defined by the H₂O/H₂ ratio. The hydrogen permeation was also continuously measured. A correlation between AE and changes of the hydrogen permeation which both occur during the thermal cycling procedure was observed. On the basis of the measurements some characteristic properties of the investigated oxide scales are derived.