PDC Bit Cutter Manufacture

PDC bits cutter is called Polycrystalline Diamond Compact Cutter. This synthetic material is 90-95% pure diamond and is manufactured into compacts that are set into the body of the bit. The high friction temperatures generated with these types of bits resulted in the polycrystalline diamond breaking up and this resulted in the development of Thermally Stable Polycrystalline Diamond – TSP Diamond. 

PCD (Polycrystalline Diamond) is formed in a two-stage high temperature, high-pressure process. The first stage in the process is to manufacture the artificial diamond crystals by exposing graphite, in the presence of a Cobalt, nickel, and iron or manganese catalyst/solution, to a pressure above 600,000 psi. At these conditions diamond crystals rapidly form. However, during the process of converting the graphite to diamond, there is volume shrinkage, which causes the catalyst/solvent to flow between the forming crystals, preventing intercrystalline bonding and therefore only a diamond crystal powder is produced from this part of the process.

In the second stage of the process, the PCD blank or ‘cutter’ is formed by a liquid phase sintering operation. The diamond powder formed in the first stage of the process is thoroughly mixed with catalyst/binder and exposed to temperatures over 1400 ℃ and pressures of 750,000 psi. The principal mechanism for sintering is to dissolve the diamond crystals at their edges, corners, and points of high pressure caused by a point or edge contacts. This is followed by epitaxial growth of diamonds on faces and at sites of the low contact angle between the crystals. This regrowth process forms true diamond-to-diamond bonds excluding the liquid binder from the bond zone. The binder forms a more or less continuous network of pores, co-existing with a continuous network of the diamond. Typical diamond concentrations in the PCD are 90-97 vol.%.

If one requires a composite compact in which PCD is bonded chemically to a tungsten carbide substrate, some or all of the binder for the PCD may be obtained from the adjacent tungsten carbide substrate by melting and extruding the cobalt binder from the tungsten carbide. 

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