Abstract

Carbon-bonded foam structures are used for metal melt filtration, especially in the steel and iron metallurgy. A recent approach is coating the filters with so called “active” and “reactive” layers. Besides the usual mechanical filtration effect, these layers were effective to withdraw the impurity particles by surface energy effects (“active”) or due to reactions with the filter substrate, the coating and gases or alloying elements in the melt (“reactive”).

In this investigation the influence of such surface coatings on carbon-bonded foam structures were evaluated by Young‘s modulus (E) at room and high temperatures using the impulse excitation method, where a prismatic sample is excited by a projectile, resulting in an oscillation. By this technique the resonance frequency of the material can be obtained and used to accurately determine E up to 1450 °C in air and inert gas atmosphere, according to ASTM 1876.

Alumina, alumina-carbon and a carbon-nanotubes containing carbon coating, were applied on the ceramic substrate and the samples were heat treated at 1400 °C in a pet coke filled retort.

These measurements and their evaluation are key aspects to provide a better understanding of the thermo-mechanical behavior of carbon-bonded foams during metal melt filtration.