Preparation Of Multi-Component Compound Bonded Polycrystalline Diamond By In Situ Reaction Of Nano-Diamond

The traditional bond of polycrystalline diamond（PCD）is usually metal bond or ceramic bond,but both haveadvantages and disadvantages.The metal bonded PCD material has more toughness and less hardness,while the ceramic bonded PCD material has higher hardness but higher brittleness,which is not an ideal choice for bonding.The multicomponent compounds as the bond of PCD can improve the disadvantages of the traditional pure metal or ceramic bond,but the reaction between the compounds is difficult,and the sintering temperature is very high,which leads to the poor bonding between the diamond and the matrix in PCD.Therefore,in this study,PCD with multi-component is prepared by in-situ reaction.And nano-diamond is used as the carbon source of in-situ reaction to prepare multi-component containing Ti₃SiC₂ phase.The existence of intermediate phase Ti C can improve the hardness of PCD,and Ti₃SiC₂ phase also has a certain effect on the tenacity of PCD,so the properties of PCD can be enhanced.In this paper,Ti powder,Si powder and diamond with different particle sizes were used as starting materials.Firstly,the temperature range of Ti₃SiC₂ synthesized was explored under normal pressure.Then,PCD was preparated under the high pressure and high temperature by using in-situ reaction in the thermodynamic stability zone of diamond,which was mainly composed of micron diamond micro-diamond.The C atoms on surface of micro-diamond chemically reacted with Ti and Si to form Ti C,SiC and Ti₃SiC₂.Nano-diamond could be used as a carbon source to react with Ti and Si to form Ti C,SiC and Ti₃SiC₂.Excessive nano diamond could be retained after sintering,which weakens the scaffolding effect of micro-diamond.Therefore PCD materials could be obtained with uniform performance.The experimental results show that:1.In situ spark plasma sintering can be carried out with nano diamond as carbon source at atmospheric pressure.When the synthesis pressure is 30 MPa,the synthesis temperature range of Ti₃SiC₂ is 1200-1450°C,the maximum density is 99.95%,and the Vickers hardness is 8.79 GPa,which is consistent with the temperature range of Ti₃SiC₂synthesized by graphite powder as carbon source,and the Vickers hardness and density are improved.2.Under the condition of high pressure and high temperature,polycrystalline diamond containing a small amount of Ti₃SiC₂ phase can be prepared by using micro-diamond and nano-diamond as the carbon source of in-situ reaction respectively,and the carbon atoms with high activity react with Ti and Si to form hard phases such as Ti C and SiC,which improves the strength of polycrystalline diamond.3.When the sintering condition is located in the phase stable region of diamond,nano-diamond can be used as carbon source to prepare PCD at 5.5 GPa and 1450°C.4.Diamond with different particle size ratio is used as carbon source,and the content of diamond in the starting material is 90%.Under the condition of high temperature and high pressure,some diamonds participate in the in-situ sintering reaction,and some unreacted diamonds remain as diamond structure.Nano-diamond has good fluidity at high pressure and high temperature,and is filled in the non pressure zone composed of micro-diamond particles,so that the phase structure of PCD is evenly distributed.