The present study provides the mechanical properties of a new generation of refractory composites based on coarse-grained Al2O3 ceramic and the refractory metals Nb and Ta. The materials were manufactured by refractory castable technology and subsequently sintered at 1600 °C for 4 h. The mechanical properties and the damage behavior of the coarse-grained refractory composites were investigated at high temperatures between 1300 and 1500 °C. The compressive strength is given as a function of temperature for materials with two different volume fractions of the refractory metals Ta and Nb. It is demonstrated that these refractory composites do not fail in a completely brittle manner in the studied temperature range. The compressive strength for all materials significantly decreases with increasing temperature. Failure occurred due to the formation of cracks along the ceramic/metal interfaces of the coarse-grained Al2O3 particles. In microstructural observations of sintered specimens, the formation of tantalates, as well as niobium oxides, were observed. The lower compressive strength of coarse-grained Nb-Al2O3 refractory composites compared to Ta-Al2O3 is probably attributed to the formation of niobium oxides. The formation of tantalates, however, seems to have no detrimental effect on compressive strength.

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Materials for steel‐melt filtration have to fulfill different thermomechanical requirements and especially withstand the thermal shock attack in the beginning of casting. In particular, carbon‐bonded alumina materials provide an excellent thermomechanical performance and have been used in functional components such as submerged entry nozzles, stoppers, and sliding gates for several years. The present study investigates the mechanical high‐temperature behavior of Al2O3‐C foam filter structures with coatings based on carbon nanotubes+Al2O3‐nanosheets (CNT‐ANS) and carbon nanotubes+Al2O3‐nanospheres (CNT‐ANB) at 1100 and 1450 °C. The foam filters are tested in an electromechanical testing machine under argon atmosphere in quasi‐static compression. The tests show a brittle material behavior at 1100 °C with higher compressive strength of the coated filter samples. At 1450 °C, a loss of strength occurs, accompanied by an increase in plastic deformation. Rupture of struts and behavior of the coatings are microstructurally analyzed by scanning electron microscopy. As the mechanical load during the tests is much longer than in real immersion tests, the high‐temperature performance is considered trustworthy.

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The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adem.202100642.