Thermogravimetric experiments coupled with acoustic emission analysis dedicated to high-temperature corrosion studies

High temperature corrosion of metallic alloys in industrial equipments, such as refinery and petrochemical equipments concerns several phenomena: oxidation, carburization These phenomena can create stresses in the materials, the relaxation of which mostly produces transient elastic waves. Several methods enable the recording and analyzing of these transient elastic waves. Piezoelectric sensors fixed directly on the sample can record elastic waves with a low decrease in energy and frequency at ambient temperature. In case of high temperature environments, a waveguide can also be used to transmit waves from sample to sensors. For this purpose, alumina or platinum are mainly used as waveguide materials. The goal of this study is to assign the acoustic signals to the corrosion phenomena and establish an acoustic signals database. This database will then be useful for the monitoring of industrial equipment using acoustic emission methods. For this purpose, thermogravimetric analysis (TGA) has been coupled with acoustic emission (AE) devices. Simultaneous measurements of the mass variation and of the acoustic signals emitted during the oxidation of samples of zirconium based alloy, Zircaloy-4, at high temperature 900 °C can provide complementary information to increase the level of understanding of high temperature corrosion mechanisms. Our work focuses on a specific waveguide (WG) conception and on the transmission of elastic waves (acoustic signals) through the waveguide at high temperature. Results on experiments concerning the corrosion of zirconium alloy plates under oxidizing atmosphere are presented.