Material properties of Cemented Carbides
Hard alloy with high hardness of refractory metal carbides (WC, TiC) micron powder as the main ingredient, with cobalt or nickel (Co) (Ni), molybdenum (Mo) as the binder, powder metallurgy products in vacuum furnace or hydrogen reduction sintering furnace. IV, B, V, B, VI, B group of metal carbides, nitrides, boride, etc., because of hardness and melting point is particularly high, collectively referred to as cemented carbide. The structure, characteristics and application of hard gold content are described with carbide as the key point. IV, B, V, B, VI, B group metals and carbon formed in the metal type carbide, because the carbon atom radius is small, can be filled in the gaps of the metal lattice, and retain the original lattice form of metal, forming interstitial solid solution. Under appropriate conditions, such solid solution can continue to dissolve its constituent elements until it reaches saturation. Therefore, their composition can change in a certain range (such as the composition of titanium carbide in TiC0.5 ~ TiC changes), chemical formula does not conform to the rules of valence. When the dissolved carbon content exceeds a certain limit (such as titanium carbide in Ti: C=1: 1), the lattice type will be changed, the original metal lattice metal lattice into another form, then the interstitial solid solution called interstitial compounds.
Metal carbides, especially B, B, IV V VI B metal carbide melting point is above 3273K, the TAC hafnium carbide, respectively 4160K and 4150K, is the highest point currently know material. Most of the carbide hardness large, their microhardness is higher than 1800kg mm2 (micro hardness is hardness says one way for hard alloy and hard compound, microhardness 1800kg mm2 is equivalent to a diamond a Mohs hardness of 9). Many carbides are difficult to break down at high temperatures, and their antioxidant power is stronger than their constituent metals. Titanium carbide has the best thermal stability in all carbides, and is a very important metal type carbide. However, in an oxidizing atmosphere, all carbides are readily oxidized at high temperatures, which can be said to be a major weakness of carbides. In addition to carbon atoms, nitrogen atoms and boron atoms can also enter the voids of the metal lattices and form interstitial solid solutions. They are similar to the gap carbide in that they can conduct electricity, heat conduction, high melting point, high hardness and great brittleness at the same time. The matrix of cemented carbide consists of two parts: one is a hardening phase, and the other is a bonding metal. Is the hardening phase transition metal carbides in the periodic table of elements, such as tungsten carbide, titanium carbide, tantalum carbide, their hardness is very high, the melting point of 2000 DEG C, and some even more than 4000 DEG C.
