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Summary of common carbide physical properties

WC = 195.8 is a black hexagonal crystal with metallic luster and hardness similar to that of diamond. It is a good conductor of electricity and heat. Melting point 2870 ℃, boiling point 6000 ℃, relative density 15.63 g / cm3 (18 ℃).

Cr3C2, orthorhombic crystal system, grayish white. Melting point 1890 ℃, theoretical density 6.75g/cm3, microhardness 1300kg / mm2, thermal expansion coefficient 11.7 × 10-6℃-1。 It has good oxidation resistance at high temperature and does not oxidize at 1100 ℃ in air for 4H. Cr3C2 is usually synthesized from Cr2O3 and carbon black in an inert or reducing atmosphere. The cemented carbide particles made of it and nichrome alloy can be used as high-temperature, wear-resistant, oxidation resistant and acid resistant coatings by plasma spraying. They are widely used in aircraft engines and petrochemical machinery and components, which can greatly improve the service life of machinery.

Co, atomic number 27, atomic weight 58.93, peripheral electron arrangement 3d74s2, located in Group VIII of the fourth cycle. The metal has a radius of 125.3 Pico meters, a first ionization energy of 763 kJ / mol, and an electronegativity of 1.8. The main oxidation number is + 1, + 3 and + 4. Silver white metal, hard and ductile, ferromagnetic, density 8.9g/cm3, melting point 1495 ℃, boiling point 2870 ℃. It does not react with air and water at normal temperature. Cobalt tetroxide is formed by burning in white heat, and it can also decompose water vapor. It can be directly combined with halogen. It can be dissolved in hydrochloric acid, sulfuric acid and nitric acid. It can be slowly eroded by hydrofluoric acid, ammonia and sodium hydroxide solutions. Used for making superhard heat-resistant alloys, magnetic alloys and alloys for cutting tools. The isotope 60Co is a radioactive source used in medical treatment, scientific research and production. In 1735, the Swede Bronte calcined the diamond ore to get cobalt. The main cobalt ores are cobaltite and arsenic cobalt. First, cobalt ore is converted into cobalt oxide, and then cobalt is prepared by aluminum reduction.

Ni, atomic number 28, atomic weight 58.71, peripheral electron arrangement 3d84s2, located in Group VIII of the fourth cycle. The metal has a radius of 124.6 Pico meters, a first ionization energy of 741.1kj/mol, an electronegativity of 1.8, and a main oxidation number of + 2, + 3 and + 4. Silver white metal with good ductility, medium hardness and ferromagnetism. Density: 8.902g/cm3, melting point: 1453 ℃, boiling point: 2732 ℃. The chemical properties are more active. It has good corrosion resistance. It is difficult to oxidize in the air at room temperature. It is not easy to react with concentrated nitric acid. It can resist alkali corrosion. The fine nickel wire is combustible, reacts with halogen when heated, and slowly dissolves in dilute acid. It can absorb a considerable amount of hydrogen. It is used for making stainless steel, corrosion-resistant alloys, batteries, chemical utensils, ceramic products, and catalysts. In 1751, the Swede kronseit first made nickel from red arsenic nickel ore. The main minerals are red arsenic nickel ore and needle nickel ore. After the ore is calcined into oxide, it is reduced with water gas or carbon to obtain nickel.

VC property: silver white crystal. The density is 5.25 ~ 5.4g/cm3. Melting point 2750 ℃. Slightly harder than quartz. It can be prepared by reducing vanadium pentoxide with coke. It is mainly used for manufacturing vanadium steel.

TAC = 192.96, carbon content of 6.224%, yellowish brown powder, hard and heavy, with high chemical stability and good high-temperature performance. The density is 14.5% g / cm3, melting point: 3875 degrees, boiling point: 5500 degrees. Tantalum carbide powder is an important cermet material. The tool made of it can withstand high temperatures below 3800 degrees, and its hardness is comparable to that of the famous diamond As a grain refiner of tungsten based cemented carbide, it can obviously improve the alloy properties, and its content can reach 0.5-5% of the output of tungsten carbide based cemented carbide.

Tic = 59.91, carbon content 20.05%, off white powder, with NaCl type cubic crystal structure, density 4.93g/cm3, melting point 3160 degrees, boiling point 4300 degrees Because of its high melting point, high hardness and good chemical stability, it is mainly used to manufacture cermet, heat-resistant alloy and cemented carbide. Adding 6% - 30% titanium carbide to WC Co cemented carbide to form tic WC solid solution with WC can significantly improve the red heat, wear resistance, oxidation resistance, corrosion resistance and other properties of the alloy, which is more suitable for processing steel than WC Co cemented carbide. Tungsten free cemented carbide can also be made by using alloys such as Ni Mo as binder, which can improve turning speed, precision and finish of machined parts.

Tin is golden yellow, melting point 2950 ℃, density 5.43. It is stable to water and non-oxygen acids other than hydrofluoric acid. Because of its high melting point, high hardness, high-temperature chemical stability and excellent thermal and electrical conductivity, titanium nitride is suitable for the field of high temperature resistance and wear resistance. High speed steel chip cutting tools with titanium nitride coating are superior to corresponding high speed steel tools. It can reduce wear, improve chip generation rate and prolong tool service life. Titanium nitride is used as gold paint in the jewelry industry, mainly for coating watch cases. It can be prepared by direct reaction of titanium and nitrogen at 1200 ℃. The coating can be formed by vapor deposition of ticl4-n2-h2 mixed gas.

Moc2 = 203.9, melting point: 2687 degrees, density: 9.18g/cm3, dark gray. The theoretical density is 9.2g/cm3. Melting point: 2690 ℃. Mohs hardness 7. Microhardness 1800kg / mm3 (load 50g). Elastic modulus 22100kg / mm2. Thermal conductivity: 6.7 × 106W/(m·K)。 Decomposition above 2300 ℃. (ceramics with monocarbonate molybdenum (MOC) as the main crystal phase). The theoretical density is 8.88g/cm3. Melting point: 2700 ℃. Generally, molybdenum carbide powder is made first (by direct conversion of molybdenum and carbon, reduction and integration of metal oxide and carbon, vapor deposition and self propagating high-temperature synthesis), and then sintered in carbon tube furnace, molybdenum wire furnace and high-frequency vacuum furnace under vacuum or reducing atmosphere (reaction sintering, hot pressing sintering and hot isostatic pressing sintering are mostly used). It is mainly used as superhard tool materials, wear-resistant materials, heating body materials and high-temperature structural materials.

ZrC, gray, face centered cubic lattice. Melting point 3540 ℃, theoretical density 6.66 g / cm3, thermal expansion coefficient 6.7 × 10-6 ℃ - 1, microhardness 2600kg / mm2, resistivity 57-75/ μ The temperature at which strong oxidation begins is 1100-1400 ℃. Insoluble in hydrochloric acid, but soluble in nitric acid. The powder is generally prepared by reducing ZrO2 with carbon, and then is shaped and sintered to become ceramics. Refractory crucible, and cathode electron emitting material.

VC silver white crystal. The density is 5.25 ~ 5.4g/cm3. Melting point 2750 ℃. Slightly harder than quartz. It can be prepared by reducing vanadium pentoxide with coke. It is mainly used for manufacturing vanadium steel.

HFC has a theoretical density of 12.7 g / cm3 and a melting point of 3890 ℃, which is the highest melting point among known single compounds. Volume resistivity: 1.95 × 10-4 Ω· cm (2900 ℃), thermal expansion coefficient 6.73 × 10-6/℃。 Hafnium dioxide (HfO2) and carbon are usually used to synthesize powders in an inert or reducing atmosphere. The reaction temperature is 1900 ~ 2300 ℃, and high-density ceramic desserts are produced by hot pressing sintering or hot isostatic pressing. Hafnium carbide can form solid solutions with many compounds (such as ZrC, TAC, etc.). For example, the composite carbide with hfc-4tac has a two-phase microstructure: one phase is the eutectic of hafnium carbide tantalum carbide; And the other is a needle like free graphite phase with a shape ratio of 50:1. This "hypoeutectic" hafnium carbide (HFC) product has good thermal stability and high melting point, and can be used as throat material of rocket nozzle.

AlN is a white to blue solid. Rhombic or hexagonal crystals. The relative density is 3.05 (25 ℃), and the Mohs hardness is 9-10. Melting point: 2150 ~ 2200 ℃ (4.357) × l05Pa)。 Sublimation at 2000 ℃. It can be decomposed into aluminum hydroxide and ammonia by water. Ammonia can be smelled in humid air. It also decomposes in acids and bases. It is produced industrially by reacting bauxite with coal and nitrogen. Aluminum powder was prepared by heating in nitrogen flow in the laboratory. It is also an effective catalyst for the conversion of hexagonal boron nitride into cubic boron nitride.