The chemical properties of tungsten and molybdenum and the reaction with gases
Tungsten and molybdenum react with carbon and carbonaceous gases: all kinds of carbonaceous gases and solid carbon (carbon black, coal, graphite) react with tungsten and molybdenum in the range of 1000-1200 ℃, forming carbides (W3C, WC and Mo2C, MOC), and the reaction is intensified at 1400-1600 ℃. Even if there is a small amount of carbide impurity in tungsten and molybdenum, it will make tungsten and molybdenum brittle.
Tungsten and molybdenum react with nitrogen: Tungsten does not react with nitrogen when it is lower than 2000 ℃, but reacts with nitrogen to form nitride wn2 above 2000 ℃. Nitrogen dissolves slowly in molybdenum above 600 ℃. Molybdenum becomes brittle above 1200 ℃. Molybdenum reacts with nitrogen to form nitride above 1500 ℃.
Reaction of tungsten and molybdenum with oxygen and air: tungsten and molybdenum are stable in air at room temperature. They begin to oxidize at about 400 ℃ and rapidly oxidize at higher temperature to form tungsten trioxide and molybdenum trioxide.
Reaction of tungsten and molybdenum with hydrogen: until the melting point temperature, hydrogen does not interact with tungsten and molybdenum, making hydrogen become an important medium in the heat treatment process of tungsten and molybdenum. However, when the temperature is lower than 1200 ℃, tungsten slightly absorbs hydrogen.
Reaction of tungsten and molybdenum with chlorine: when the metal tungsten is heated to 500 ℃, it directly reacts with chlorine to form WCl6. When the temperature is higher, WCl6 is decomposed into wcl5. Iodine vapor has no effect on tungsten.
The reaction of W and Mo with water vapor: W and Mo are easy to oxidize with water vapor, and the effect is more rapid above 600 ℃.
