The cemented carbide substrate consists of two parts: one is the hardened phase and the other is the bond metal.
The hardening phase is the carbide of the transition metals in the periodic table of the elements, such as tungsten carbide, titanium carbide, and tantalum carbide. Their hardness is high, the melting point is above 2000°C, and some even exceed 4000°C. In addition, nitrides, borides, and silicides of transition metals have similar characteristics and can also act as hardened phases in cemented carbides. The presence of a hardened phase determines the extremely high hardness and wear resistance of the alloy.
The bond metal is generally an iron group metal, commonly used cobalt and nickel.
When the cemented carbide is manufactured, the raw material powder used has a particle size between 1 and 2 microns and has a high purity. The raw materials are proportioned according to the prescribed composition ratio, and the alcohol or other medium is added to wet grinding in a wet ball mill so that they are fully mixed and crushed. After being dried and sieved, a forming agent such as wax or glue is added and then dried and passed. Sieve the mixture. Then, when the mixture is pelletized, pressed, and heated to a temperature close to the melting point of the binder metal (1300 to 1500°C), a eutectic alloy is formed between the hardening phase and the binder metal. After cooling, the hardened phases are distributed in a grid of bonded metals that are closely linked to each other to form a solid body. The hardness of cemented carbide depends on the content of hardened phase and the grain size, that is, the higher the content of hardened phase and the finer the grains, the greater the hardness. The toughness of cemented carbide is determined by the bonding metal. The higher the bonding metal content, the greater the bending strength.
In 1923, Germany's Schlatter added 10% to 20% of cobalt to the tungsten carbide powder as a binder, invented a new alloy of tungsten carbide and cobalt. The hardness is second only to diamond, which is artificial in the world. The first cemented carbide. When a tool made of this alloy cuts steel, the cutting edge wears quickly and even the edge cracks. In 1929, Schwarzkopf of the United States added a certain amount of compound carbides of tungsten carbide and titanium carbide to the original composition, which improved the performance of cutting steel. This is another achievement in the history of cemented carbide.
Carbide has a series of excellent properties such as high hardness, wear resistance, strength and toughness, heat resistance, corrosion resistance, etc., especially its high hardness and wear resistance, and it remains basically unchanged even at a temperature of 500°C. , It still has high hardness at 1000°C. Carbide alloys are widely used as tool materials, such as turning tools, milling cutters, planers, drills, boring tools, etc. They are used to cut cast iron, non-ferrous metals, plastics, chemical fiber, graphite, glass, stone, and general steel materials. They can also be used for cutting. Heat-resistant steel, stainless steel, high manganese steel, tool steel and other difficult-to-machine materials. The cutting speed of the new carbide tool is now several hundred times that of carbon steel.
Cemented carbide can also be used to make rock drilling tools, mining tools, drilling tools, measuring tools, wear parts, metal grinding tools, cylinder linings, precision bearings, nozzles and so on.
In the past two decades, coated carbide has also come out. In 1969, the titanium carbide titanium layer tool was successfully developed in Sweden. The substrate of the tool is tungsten titanium cobalt hard alloy or tungsten cobalt carbide. The thickness of the surface titanium carbide coating is only a few microns, but compared with alloy cutters of the same grade, The service life is increased by 3 times and the cutting speed is increased by 25% to 50%. The fourth generation of coating tools emerged in the 1970s and can be used to cut difficult-to-machine materials.
Superalloy
Superalloys usually work at high temperatures above 700°C (or even 1000°C) and must have special properties such as oxidation resistance and high temperature strength.
Oxidation-corrosion is the weak point of metal, and under high temperature conditions, the oxidation corrosion reaction of metal will be greatly accelerated, as a result of which the metal surface will be rough, affecting its accuracy and strength, and in severe cases it will even cause the part to be scrapped. If working under high temperature conditions with corrosive media (such as phosphorus, sulfur, and vanadium in gas after combustion of high-temperature and high-pressure gasoline), the corrosion effect is stronger, so high-temperature alloys must have high resistance to oxidative corrosion.
Superalloys work at extremely high temperatures and must have sufficient resistance to creep (ie, the slow and continuous deformation of a solid material under certain stress) to ensure that it passes under certain conditions of temperature and stress. For a long period of time, the total deformation is still within a certain allowable limit.
High-temperature alloys work at high temperatures or work under alternate temperature conditions, are more prone to fatigue failure than normal temperatures, or cause considerable fatigue stress due to repeated and rapid changes in heat and cold during work. Superalloys must have good resistance to fatigue (ie, sudden breaking of materials or parts under long-term changing loads).
In order to meet the needs of the latest high-tech, high-temperature alloys based on refractory metals (W melting point 3400°C, Re3160°C, Ta2996°C, Mo2615°C, Nb2415°C) can work in a high-humidity environment above 1500°C and are suitable for manufacturing. Spacecraft components working in high temperature and high stress environments. Among refractory metals, Ta and Nb alloys are characterized by high temperature resistance and corrosion resistance, as well as high strength and hardness. Some niobium-based alloys can work in the range of 1300-1600°C, which is 300-500°C higher than that of nickel-base alloys. A niobium-based alloy developed at home, containing W8% and Hf2%, still has high strength, good machinability, and weldability at an ultra-high temperature of 2000°C. It is a more ideal superalloy. Cermets are also sometimes included in superalloys.
The hardening phase is the carbide of the transition metals in the periodic table of the elements, such as tungsten carbide, titanium carbide, and tantalum carbide. Their hardness is high, the melting point is above 2000°C, and some even exceed 4000°C. In addition, nitrides, borides, and silicides of transition metals have similar characteristics and can also act as hardened phases in cemented carbides. The presence of a hardened phase determines the extremely high hardness and wear resistance of the alloy.
The bond metal is generally an iron group metal, commonly used cobalt and nickel.
When the cemented carbide is manufactured, the raw material powder used has a particle size between 1 and 2 microns and has a high purity. The raw materials are proportioned according to the prescribed composition ratio, and the alcohol or other medium is added to wet grinding in a wet ball mill so that they are fully mixed and crushed. After being dried and sieved, a forming agent such as wax or glue is added and then dried and passed. Sieve the mixture. Then, when the mixture is pelletized, pressed, and heated to a temperature close to the melting point of the binder metal (1300 to 1500°C), a eutectic alloy is formed between the hardening phase and the binder metal. After cooling, the hardened phases are distributed in a grid of bonded metals that are closely linked to each other to form a solid body. The hardness of cemented carbide depends on the content of hardened phase and the grain size, that is, the higher the content of hardened phase and the finer the grains, the greater the hardness. The toughness of cemented carbide is determined by the bonding metal. The higher the bonding metal content, the greater the bending strength.
In 1923, Germany's Schlatter added 10% to 20% of cobalt to the tungsten carbide powder as a binder, invented a new alloy of tungsten carbide and cobalt. The hardness is second only to diamond, which is artificial in the world. The first cemented carbide. When a tool made of this alloy cuts steel, the cutting edge wears quickly and even the edge cracks. In 1929, Schwarzkopf of the United States added a certain amount of compound carbides of tungsten carbide and titanium carbide to the original composition, which improved the performance of cutting steel. This is another achievement in the history of cemented carbide.
Carbide has a series of excellent properties such as high hardness, wear resistance, strength and toughness, heat resistance, corrosion resistance, etc., especially its high hardness and wear resistance, and it remains basically unchanged even at a temperature of 500°C. , It still has high hardness at 1000°C. Carbide alloys are widely used as tool materials, such as turning tools, milling cutters, planers, drills, boring tools, etc. They are used to cut cast iron, non-ferrous metals, plastics, chemical fiber, graphite, glass, stone, and general steel materials. They can also be used for cutting. Heat-resistant steel, stainless steel, high manganese steel, tool steel and other difficult-to-machine materials. The cutting speed of the new carbide tool is now several hundred times that of carbon steel.
Cemented carbide can also be used to make rock drilling tools, mining tools, drilling tools, measuring tools, wear parts, metal grinding tools, cylinder linings, precision bearings, nozzles and so on.
In the past two decades, coated carbide has also come out. In 1969, the titanium carbide titanium layer tool was successfully developed in Sweden. The substrate of the tool is tungsten titanium cobalt hard alloy or tungsten cobalt carbide. The thickness of the surface titanium carbide coating is only a few microns, but compared with alloy cutters of the same grade, The service life is increased by 3 times and the cutting speed is increased by 25% to 50%. The fourth generation of coating tools emerged in the 1970s and can be used to cut difficult-to-machine materials.
Superalloy
Superalloys usually work at high temperatures above 700°C (or even 1000°C) and must have special properties such as oxidation resistance and high temperature strength.
Oxidation-corrosion is the weak point of metal, and under high temperature conditions, the oxidation corrosion reaction of metal will be greatly accelerated, as a result of which the metal surface will be rough, affecting its accuracy and strength, and in severe cases it will even cause the part to be scrapped. If working under high temperature conditions with corrosive media (such as phosphorus, sulfur, and vanadium in gas after combustion of high-temperature and high-pressure gasoline), the corrosion effect is stronger, so high-temperature alloys must have high resistance to oxidative corrosion.
Superalloys work at extremely high temperatures and must have sufficient resistance to creep (ie, the slow and continuous deformation of a solid material under certain stress) to ensure that it passes under certain conditions of temperature and stress. For a long period of time, the total deformation is still within a certain allowable limit.
High-temperature alloys work at high temperatures or work under alternate temperature conditions, are more prone to fatigue failure than normal temperatures, or cause considerable fatigue stress due to repeated and rapid changes in heat and cold during work. Superalloys must have good resistance to fatigue (ie, sudden breaking of materials or parts under long-term changing loads).
In order to meet the needs of the latest high-tech, high-temperature alloys based on refractory metals (W melting point 3400°C, Re3160°C, Ta2996°C, Mo2615°C, Nb2415°C) can work in a high-humidity environment above 1500°C and are suitable for manufacturing. Spacecraft components working in high temperature and high stress environments. Among refractory metals, Ta and Nb alloys are characterized by high temperature resistance and corrosion resistance, as well as high strength and hardness. Some niobium-based alloys can work in the range of 1300-1600°C, which is 300-500°C higher than that of nickel-base alloys. A niobium-based alloy developed at home, containing W8% and Hf2%, still has high strength, good machinability, and weldability at an ultra-high temperature of 2000°C. It is a more ideal superalloy. Cermets are also sometimes included in superalloys.