Abstract
Corrosion is one of the most common wear mechanisms of refractories. Corrosive attacks lead to chemical and microstructural changes. Hot corrosion compromises chemical and/or physical interactions. Thus, the process is complex and not yet fully understood. Currently, corrosion is investigated post mortem by means of X-ray diffraction or scanning electron microscopy. These methods have the drawback that some information is lost on cooling. In-situ measurements, however, take measurements within the process. In resonant frequency and damping analysis (RFDA), a sample is excited to vibrate by a mechanical impulse. The vibrating sample emits an acoustic signal. This is recorded with a microphone and evaluated by means of Fast Fourier Transformation (FFT). We measured the change of the frequency of a low cement castable during the corrosion process. Further simplified experiments with less complex materials were done to confirm the results. Distinctive points of the curves could be correlated to specific corrosion phenomena, like melting or infiltration. The applied methods include a first characterization of the material with open porosity, density and in-situ high-temperature (HT)-RFDA measurements as well as a study of the slag behavior.
Highlights
Refractory materials are most suitable and developed for extreme operating conditions
Materials chosen for the investigation are a dense aluminum oxide ceramic known as alumina, a tabular alumina-based low cement castable (LCC) and aluminum
We performed several basic experiments prior to the corrosion test of the LCC to explain certain phenomena that occur within the process
Summary
Refractory materials are most suitable and developed for extreme operating conditions. The different chemical compositions of material and corrosion medium leads to a gradient of the chemical potential. This makes interactions between these two partners unavoidable. In addition to the chemical attack, the material can be subjected to mechanical stress. If the refractory materials are not precisely tailored to the given process parameters, above-average wear may occur. Due to the chemical and physical interactions, combined with the heterogeneous material behavior, the prediction of the corrosion process, especially with industrial melts and slags, is extremely complex. Predicting the behavior of refractories under corrosive attack is Ceramics 2020, 3, 101–113; doi:10.3390/ceramics3010011 www.mdpi.com/journal/ceramics
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