| PCBN(Polycrystalline cubic boron nitride)is composed of countless , exiguous and disorderly arranged CBN single microcrystal. It is non-orientated on macroscopy without split glaze, which will reduce the impact on cleaving. With the wear and tear of cutting tools, PCBN will continuously show out new crystal。The material of PCBN(Polycrystalline cubic boron nitride)cutting tools is divided into polycrystalline cubic boron nitride sinter (PCBN sinter) and compound polycrystalline cubic boron nitride (PCBN compound cutting slice) according to it's component and manufacturing technique. PCBN has good chemical resistance , and show good thermal stability under 1200℃high temperature, so the relative high temperature on the top end of cutting tool will not have a bad impact on it. On the contrary, the high temperature can speed up cutting when we are cutting hard iron alloy. CBN single microcrystal is sintered with binder or without binder under high temperature and high pressure, as simplify the difficulty of implementing high-pressure equipment in directly transforming and make it feasible to sinter CBN single microcrystal. The techniques of sintering PCBN include two basic ones of sintering with binder and that without binder. The binder mainly make CBN single microcrystal to hard cluster. At the same time, the physical and chemical properties of phase need to be considered, and binder must form the compatible component with CBN single microcrystal. The phase should have thermal resistance and wear resistance. CBN polycrystalline need to be sintered under high temperature and high pressure. Sintering is influenced by many factors, such as different assembling techniques, pressure, temperature, sintering hours and the performance of raw material and so on. The article take sintering PCBN with Ti/Al bond for example to discuss the effect rule of these factors. Sintering reaction of PCBN with Ti/Al binder is the same as the others. In the beginning of the sintering ,because of cBN,binder grain mechanical physics extrusion,break up and slightly plasticity shape under the Aluminum melt point ,the material becomedensifieation。Melting Al/ Ti Alloying full into the hole, so cBN grain can Maximizing rerrangement. Under the high sintering temperature ,Al,Ti and N,B could synthesize phases of AlN,TiN,TiB2,AlB2 and so on which are difficult to be melted。In the experiment ,we use three different types construction arrangement:graphite tube,Graphite tube and Molybdenum cup,Graphite tube + Molybdenum cup+ NaCl tube to sintering PCBN。The result show that in three different types construction arrangement,the mainly compose of PCBN is the CBN and CBN binder。In the extent of press and temperature,do not discover reversible react between the cBN and hBN。In addition, for predigesting construction arrangement and reducing cost,the same time preventing from impurity going into the PCBN, the way of assembling can adopt the graphite tube and molybdenum cup。The effects of the sintering temperature on the physical property of PCBN is investigated in this paper that show it is greater. The wear resistance ration of PCBN obtained from T4 to T5, 95Mpa is higher than the other experiment conditions. Onthe sintering way the sintering reaction that could synthesize the binder phase of TiN,Al2N3 and TiB is complete, while the effects of temperature on the grain of CBN is as small as possible.
|
PDF Full Text Request