Recent years, since the development of mining and energy exploration as well as some large-scale infrastructure construction projects, tungsten carbide for mining, such as tungsten carbide buttons, bits, picks, mills, DTH drills and some supporting tools has been widely used and the market demands increased gradually. With the rapid development of metallurgical industrial technology of our country, in gas, fuel oil, natural gas drilling, some demands of mechanical mining equipment and large and medium pore diameter drill with carbide ore also increased. Mining tools take advantage of WOB and rotation of the impact load itself broken rock, drill and buttons during operation when subjected to high impact loads at the same time by twisting, bending, stretching, compression and other complex stress. And it subjected to the wear and corrosion by rocks, rock dust, mineral water, etc. at high-speed rotation. So it requires that tungsten carbide used for mining not only has high hardness and toughness, but also has good wear and corrosion resistance.
In order to combine wear resistance with toughness, relevant researchers develop many new types of carbide, such as ultra-fine or nano cemented carbide, high-temperature powder based carbides, functional gradient tungsten carbide, low-Co and coarse grain carbide, double binder phase and double crystalline structure, etc. Double binder phase was developed by American company, which fully dense WC-Co pellets embedded in Co matrix to remain the similar wear resistance of common alloys. The binder phase can be any bonding metal, alloy or another kind of cemented carbide.
The most outstanding characteristic is that the hard phase is not a hard compound (WC), which is composed of refractory metal compound and Co sintered hard material into crystalline pellets (WC-Co) composition and mixed with binder metal for secondary sintering. Compared with most of double phase tungsten carbide, double binder phase carbide has greater design freedom (size, hardness, toughness, strength of base and so on), which has been widely used in rolling cutter bits, impacting bits, dragging bits and other tools. Double crystalline tungsten carbide is also called as non-uniform grain carbide. Since the WC grain size distribution curve has two peaks, it can be also known as bimodal-structure tungsten carbide. This kind of structure coarse grain WC can provide good ductility and toughness, and a certain proportion of fine grain WC is able to provide high wear resistance.
