The matrix of cemented carbide consists of two parts: one part is the hardening phase; the other part is the bonding metal.
The hardened phase is the carbide of transition metals in the periodic table, such as tungsten carbide, titanium carbide, and tantalum carbide. In addition, nitrides, borides, and silicides of transition metals have similar properties and can also act as hardening phases in cemented carbide. The existence of the hardened phase determines the alloy's extremely high hardness and wear resistance.
Binder metals are generally iron group metals, commonly cobalt and nickel.
When manufacturing cemented carbide, the particle size of the selected raw material powder is between 1 and 2 microns, and the purity is very high. The raw materials are batched according to the prescribed composition ratio, and alcohol or other media are added to wet grinding in a wet ball mill to make them fully mixed and pulverized. After drying and sieving, a type of molding agent such as wax or glue is added. Sieve the mixture. Then, the mixture is granulated, pressed, and heated to a temperature close to the melting point of the binder metal (1300-1500 °C), the hardened phase and the binder metal will form an eutectic alloy. After cooling, the hardened phases are distributed in the grid composed of the bonding metal and are closely connected with each other to form a solid whole. The hardness of cemented carbide depends on the hardened phase content and grain size, that is, the higher the hardened phase content and the finer the grains, the greater the hardness. The toughness of cemented carbide is determined by the binder metal, and the higher the binder metal content, the greater the flexural strength.
Superalloys usually work in a high temperature environment above 700 °C (even 1000 °C), and must have special properties such as oxidation resistance and high temperature strength. The weakness of metal is that it is easy to be oxidized and corroded, and under high temperature conditions, the oxidation and corrosion reaction of metal will be greatly accelerated, resulting in rough metal surface, affecting its accuracy and strength, and even scrapping parts in severe cases. If it works under high temperature conditions with corrosive media (such as high temperature and high pressure gasoline containing phosphorus, sulfur, and vanadium in the gas after combustion), the corrosion effect will be stronger, so the superalloy must have high oxidation corrosion resistance. ability. Superalloys work at extremely high temperatures and must have sufficient creep resistance (that is, the solid material undergoes slow and continuous deformation under the action of a certain stress) to ensure that it is under certain temperature and stress conditions. After a long period of work, the total deformation is still within a certain allowable limit. Superalloys are more prone to fatigue damage than normal temperature due to working at high temperatures or under conditions of alternating temperature changes, or fatigue damage caused by the formation of considerable thermal stress due to repeated rapid thermal changes during the working process. Superalloys must have good fatigue resistance (that is, the phenomenon of sudden fracture of materials or parts under the action of long-term changing loads).
