Theoretical Study on High Pressure Liquid Sintering ofPolycrystalline Diamond Compact

Based on the theoretical analysis of the interaction between diamond and melted cobalt under HP/HT conditions,the effect of temperature and carbon content of the melted cobalt on the sintering process of diamond dissolution and polycrystalline diamond growth are discussed.It is suggested that the diamond is preferable to graphite to dissolve in the melted cobalt under HP/HT and there are three sintering mechanisms in the diamond-cobalt sintering system,that is,the mechanism of diamond rearrangement,dissolution and precipitation and formation of the direct bonding of diamond to diamond.The melted cobalt with different carbon content and temperature can play an important role to weak or cease the covalent bond of diamond at its surfaces, to promote the rearrangement of diamond,to realize the transportation of diamond atoms and finally to form the diamond to diamond bonding structure of polycrystalline diamond.According to the high pressure liquid sintering theory of diamond proposed in this paper,some experimental phenomena found during the HP/HT sintering process of polycrystalline diamond compacts could be explained rationally.