Yttrium-aluminium-perovskite-fibre/molybdenum-matrix composites: Strength, fracture toughness and oxidation resistance

Abstract

Thermal efficiency of a gas turbine depends on the highest temperature of the thermal cycle in a machine. Nickel supperalloys used in modern gas turbines have approached their physical limit. Hence, transportation and energy technologies call for new generations of heat resistant materials. Among four families of future heat resistant materials, metal matrix composites (MMCs), ceramic matrix composites, alloys based on refractory metals, and high entropy alloys, materials of the first family, MMCs, are characterized by an attractive balance between strength and fracture toughness. The only choice of the matrix for really high temperature composites is a refractory metal, for example, molybdenum. Since composites are to be exploited in extremely hard environments and the requirements to various important properties of future materials of practical importance often contradict each other, the choice of a particular fibre/matrix combination is to be based on the results of studies of a large number of variants. In the present work, molybdenum matrix composites reinforced with fibres based on yttrium-aluminium perovskite (YAP) have been obtained for the first time using the internal crystallization method. The fabrication technology and fibres microstructures are briefly discussed. Strength, fracture toughness and oxidation resistance are discussed in details. The composites proved to be sufficiently strong at temperatures up to 1400 °C and of are characterized by low notch sensitivity at room temperature. Oxidation resistance of the molybdenum matrix of the composites at temperatures 1000 and 1100 °C is much better than that of pure molybdenum.