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Study On Niobium Carbide Properties And NbC Application

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Update time : 2020-02-13 13:11:03

Niobium carbide is a green cubic crystal with metallic luster and belongs to  the sodium chloride type cubic crystal system. Niobium carbide is a metal  carbide with the chemical formula NbC.
 

Characteristics of Niobium Carbide:

The melting point of niobium carbide is 3500 ℃, and its microhardness is>  23.5 Gpa (> 2400 kg / mm2), which is harder than corundum. Niobium carbide  has an elastic modulus of 338000 N / mm2, a thermal expansion coefficient of  6.65 × 10 ^ (-6) / K, a thermal conductivity of 14 w / (m · K), and a  resistivity of 35 μΩ · cm.
 

Niobium carbide is insoluble in cold and hot hydrochloric acid, sulfuric  acid, and nitric acid, and it is soluble in hot hydrofluoric acid and nitric  acid mixed solution. It is stable at 1000 ~ 1100 ℃, and quickly oxidizes to  niobium pentoxide above 1100 ℃. Niobium carbide is fusible in compounds such as  titanium carbide, zirconium carbide, and tungsten carbide, and together forms a  homogeneous solid solution mixture.


 

Fields of NbC Application:

1.NbC application in composite materials
 

(1) Composite ceramics

As one of the raw materials of multiphase ceramic materials, the manufactured  multiphase ceramic materials are often used in the fields of wear-resistant  parts, cutting tools and electrodes due to their high hardness, high melting  point, excellent chemical stability, and conductivity.
 

(2) Hard alloy

Not only can be used as an inhibitor of cemented carbide grain growth but  also can form a third dispersed phase with the exception of WC and Co together  with other carbides, which can significantly improve the thermal hardness and  resistance to thermal shock Antioxidant ability. Because niobium carbide has the  advantages of improving the hardness of the alloy and improving the fracture  toughness of the alloy, it can be used to prepare hard alloy cutting tool  materials with excellent cutting performance.
 

(3) Surfacing electrode

The hard niobium carbide hard phase enters the structure of the surfacing  layer, so that the welding layer has a better wear-resistant skeleton, and the  wear resistance is greatly improved. The wear resistance of this electrode  surfacing is 1.2 ~ 1.8 times higher than that of quenched 45 steel (HRC50), and  2.4 ~ 3.6 times higher than Fe-Cr-C-B type wear-resistant alloy.
 

(4) Aerospace components

It is used as preparation material for parts of many aerospace equipments  such as turbine rotors, gas rudders, blades, engine nozzle linings, and  structural parts of nuclear reactors.
 

2. NbC application in coating materials
 

(1) Mold steel surface coating

As a metal carbide, niobium carbide has high hardness, heat resistance, and  abrasion resistance. Therefore, coating it on steel shows that it can improve  the wear resistance of the mold surface.


 

(2) Coating of metal workpieces

The niobium carbide layer is compounded on the surface of the base of the  metal workpiece, which greatly improves the surface hardness, which can reach  HV2800 or higher, and at the same time, increases the working temperature and  tissue density of the workpiece, thereby extending its service life.
 

(3) other niobium carbide coatings

The high-temperature parts of the spacecraft are coated with niobium carbide,  which can significantly increase their service life. In the electronics  industry, the material of the middle layer of the electron emission tube uses  ultra-fine cobalt-containing niobium carbide, which has a significant effect on  increasing the emissivity of the gate surface, reducing the gate temperature and  reducing the thermal emission of the gate, thereby extending the electron  emission tube's life.
 

3. NbC application in the production of metal niobium

Our country mainly uses indirect reduction to produce metallic niobium. The  produced niobium carbide is used as a reducing agent, which interacts with  niobium pentoxide to produce crude metallic niobium, and then is refined to  obtain metallic niobium with higher purity. Besides, niobium carbide can  directly reduce niobium pentoxide to form pure metal niobium.