High-Temperature Properties of Mixed α'/β'-SiAlON Materials |
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Authors: | Hagen Klemm,Mathias Herrmann,Thomas Reich,Christian Schubert,Lutz Frassek,Gerhard Wö tting,Ernst Gugel,Georg Nietfeld |
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Affiliation: | Fraunhofer Institute of Ceramic Technologies and Sintered Materials, IKTS, Dresden 01277, Germany;Cremer Forschungsinstitut, CFI, 96472 Rödental, Germany;H. C. Starck, Goslar 38642, Germany |
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Abstract: | The mechanical behavior of mixed α'/β'-SiAlON materials was studied at elevated temperatures. Two different α'/β'-SiAlON compositions along the Si3N4-Y2O39AlN composition line in the Si3N4-Al2O3AlN-YN3AlN plane (α'-SiAlON plane) were prepared using three different raw-material mixtures. Six different materials were obtained with significantly lower values in α'-SiAlON than expected. The high-temperature properties of the materials studied were influenced strongly by the chemical composition (α' content and grain-boundary phase) of the SiAlONs. A high content of α'-SiAlON was beneficial in terms of creep behavior of the materials. The same materials, however, were characterized by a considerably degradated fracture behavior at elevated temperatures in air because of a crack-growth process enhanced by the poor oxidation resistance of these materials. It was concluded that, despite some superior features of the materials studied, a long-term application of mixed α'/β'-SiAlON materials at 1400°C in air is problematical. A combination of all properties required for such applications was not observed. For that reason, it is suggested that the real high-temperature potential of these materials in air should be limited to temperatures <1300°C. |
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