New applications of molybdenum alloys

The main way to solve the low temperature ductility and high temperature oxidation of molybdenum is to develop an advanced composite material based on molybdenum disilicide (MoSi₂).Mo0sub>2 formed by contact between molybdenum and oxygen sublimates at 800℃ and gets a kind of yellow and white pith when condensing, which causes serious engineering problems for the advantage of molybdenum in high temperature strength and creep resistance. A self - healing silicon - rich coating was used for this purpose. The mo-si-b composite material with molybdenum disilicide as matrix has excellent high temperature strength and oxidation resistance, but poor ductility. In order to solve the ductility problem, the composition range of this molybdenum-silicon-boron composite has been determined recently, and its high temperature mechanical properties are comparable to those of TZM alloy except its excellent antioxidant properties. The matrix of the composite was Mo₅SiB(T2), and molybdenum was the second phase. The ductility of composites is improved by metal phase, and the self-healing oxide skin can be formed by matrix phase. At present, the composite material of mo-6ti-2.2si-1.1b made by adding titanium at the same time is exposed to the air at 1370℃ for 2 hours, and the changes are almost invisible to the naked eye, which is superior to TZM. This is a remarkable achievement for molybdenum-based alloys.