Application of molybdenum
Molybdenum is a refractory metal. Molybdenum and its alloys have been widely used in aerospace, national defense, military industry, electronic and electrical metallurgy and glass industry because of their excellent electrical conductivity, thermal conductivity, corrosion resistance, low thermal expansion coefficient, high hardness and high temperature strength. However, molybdenum begins to oxidize at 400 ℃ in air, which makes its performance decline; MoO3 is oxidized above 725 ℃. The rapid volatilization and formation of white smoke, and with the increase of temperature, the oxidation of molybdenum and molybdenum alloys in high temperature and aerobic environment is greatly restricted. Therefore, it is very important to study and improve the high temperature oxidation resistance of molybdenum and its alloys for expanding their application in the field of materials.
At present, the research on high temperature oxidation resistance of molybdenum and its alloys mainly focuses on two aspects: (1) alloying. The oxidation resistance of molybdenum and molybdenum alloy was improved by alloying technology; (2) surface coating. A layer of anti-oxidation coating was formed on the surface of molybdenum and molybdenum alloy to make it have the ability of oxidation resistance. Alloying can improve the oxidation resistance of molybdenum and molybdenum alloy to a certain extent, but on the one hand, the alloying degree of molybdenum is small, on the other hand, alloying technology will change the properties of molybdenum alloy to a certain extent, so the alloying method has certain limitations. In contrast, the surface coating method can improve the high temperature oxidation resistance of molybdenum and its alloys while maintaining the related properties. The intermetallic compound MoSi2, which has excellent high temperature oxidation resistance due to the formation of dense MoSi2 protective film at high temperature, is considered to be the most suitable high temperature coating material for engineering application and the preferred material for anti-oxidation coating on molybdenum alloy surface.
