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Application Of Metallic Cobalt In The Aerospace Field

wallpapers Industry 2020-12-25
Cobalt, element symbol Co, silver-white ferromagnetic metal, the surface is silver-white and slightly pink, located in the 4th period, group VIII in the periodic table, atomic number 27, atomic weight 58.9332, close-packed hexagonal crystal, common valence is +2 , +3. Cobalt is a lustrous steel gray metal, relatively hard and brittle, ferromagnetic, and its magnetism disappears when heated to 1150°C. The valence of cobalt is +2 and +3.
The most widely used alloy in aerospace technology is nickel-based alloy, and cobalt-based alloy can also be used, but the "strength mechanism" of the two alloys is different. The high strength of nickel-based alloys containing titanium and aluminum is due to the formation of a phase strengthening agent composed of NiAl(Ti). When the operating temperature is high, the phase strengthening agent particles will turn into solid solution, and the alloy will quickly lose strength.
The heat resistance of cobalt-based alloys is due to the formation of refractory carbides. These carbides are not easily converted into solid solutions and have low diffusion activity. When the temperature is above 1038°C, the superiority of cobalt-based alloys is fully demonstrated.
For the manufacture of high-efficiency high-temperature engines, cobalt-based alloys are just right. In the structural materials of aviation turbines, cobalt-based alloys containing 20% to 27% chromium are used, and the materials can achieve high oxidation resistance without protective coatings. The mercury supplied by the nuclear reactor allows the turbine generator of the heat medium to operate continuously for more than one year without maintenance.
It is reported that the boiler of the generator used in the American test is made of cobalt alloy. Cobalt is one of the few metals that can maintain magnetism once magnetized. Under the action of heat, the temperature at which magnetism is lost is called the Curie point. The Curie point of iron is 769°C, nickel is 358°C, and cobalt can reach 1150°C. The coercive force of magnetic steel containing 60% cobalt is 2.5 times higher than that of general magnetic steel. Under vibration, general magnetic steel loses almost 1/3 of its magnetism, while cobalt steel loses only 2% to 3.5% of its magnetism. Therefore, the advantages of cobalt in magnetic materials are obvious.

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