SiC-Matrix Composite Materials for Advanced Jet Engines
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SiC-Matrix Composite Materials for Advanced Jet Engines
R. Naslain and F. Christin
fabricated, show a high durability when exposed under load to corrosive environments such as combustion gas. On the basis of these properties, SiC CMCs are promising materials for advanced jet engines. Their use in this field is envisaged exclusively for the fabrication of nonrotating parts in military jet engines, including combustion chambers and afterburner parts (e.g., exhaust cones, flame holders, or exhaust nozzle flaps).8–13 Some of these parts have already been bench- or flight-tested successfully and qualified, and a few are in volume production. This article gives an overview of the state of the art in SiC CMCs and offers examples of the application of SiC CMCs in the field of advanced jet engines.
Processing Abstract SiC-matrix composites consist of ceramic fibers embedded in a silicon carbide matrix produced by gas-, liquid-, or solid-phase routes, yielding materials that differ in matrix crystallinity, residual porosity, and thermal properties. These composites can be highly engineered in terms of the nature of the reinforcement, the interphase used to control the fiber-matrix bonding, the matrix, and the seal coating used . SiC-matrix composites are refractory ceramics displaying outstanding mechanical and thermal properties at high temperature. Their durability in oxidizing atmospheres and under load exceeds 1000 h at temperatures of up to 1200C. They have been used to fabricate different components of the hot zone of jet engines with significant weight savings and an increase in performance. This article reviews the state of the art in the processing, materials design, and properties of these composites as well as their applications in advanced jet engines. Keywords: composites, C/SiC, jet engines, processing, SiC/SiC, ultrahigh-temperature materials.
Introduction There are two main driving forces behind the introduction of ceramics in the hotstructure zone of jet engines. The first is the demand for higher operating temperatures in order to achieve greater engine efficiency and a reduction in NOx/CO emissions. The second is an important weight savings, coming from the fact that structural ceramics have a much lower density than nickel- or cobalt-based superalloys and that ceramics can be used uncooled. Covalent nonoxide monolithic ceramics such as silicon carbide display attractive properties. They are refractory, light, rigid, strong, and creep-resistant. Further, SiC is oxidation-resistant up to 1500C, due to the formation of a protective silica scale in the so-called passive oxidation regime. Unfortunately, monolithic SiC ceramics are intrinsically brittle and unreliable, which has precluded their use in such a demanding application as jet engines. SiC-based ceramic-matrix composites (CMCs) consist of ceramic fibers (SiC or C fibers) embedded in a SiC matrix by dif654
ferent processing routes.1–3 They display most of the properties of monolithic SiC ceramics and are also tough and reliable when the fiber-
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