Properties Of Diamond-WC-Co Composites Synthesized At High Temperature And High Pressure

Diamond composite sheets are widely used in oil,natural gas drilling and other fields.When it works,the residual stress generated at the interface makes the PCD layer and the cemented carbide layer delamination or the overall fracture of the composite sheet,which will affect the life of the tool and reduce the efficiency of production.In order to extend the life of the diamond composite sheet tool,a gradient material combining the transition layer and the diamond composite sheet has become a current research hotspot.Therefore,in this study,diamond,WC,and Co were used as initial raw materials.Using high temperature and high pressure method can reduce the sintering temperature of the material,shorten the holding time,inhibit the growth of crystal grains,and avoid the advantages of diamond graphitization,etc.The pure WC bulk and diamond-WC-Co composite material with excellent mechanical properties are prepared by changing the content of Co.The experimental results show:(1)The hardness of the pure WC bulk materials obtained under the conditions of 5.5 GPa,1300 ℃ and holding temperature for 300 s is 30.7 GPa.X-ray diffraction analysis results show that the characteristic peaks of the synthesized non-binder phase WC bulk are consistent with the peaks of the initial powder,and no other impurity peaks appear.According to the scanning electron micrograph,the grain size and grain distribution of the sample obtained under the condition of 1300℃ are uniform,the grain size is small,and the grain boundaries are more,so the hardness is the largest.(2)A dense diamond-WC-Co composite bulk was successfully prepared under the conditions of 5.5 GPa and 1100～1500 ℃.The performance of the sintered samples with different doping ratios was characterized by X-ray diffraction,Raman spectroscopy,scanning electron microscopy,and Vickers hardness tester.The analysis found that the optimal experimental conditions for samples prepared with different ratios were 1 250 and holding ℃for 2 min.The prepared diamond-90wt%WC-5wt%Co composite bulk has a maximum hardness of 23.6 GPa and a relative density of 96%.The highest hardness of the diamond-90wt%WC-5wt%Co composite bulk is higher than that of most commercial cemented carbides.The mass fraction of diamond is 5%(20% by volume),and its content is relatively small.so diamond is dispersed in the cemented carbide matrix and does not form a skeleton.At the same time,diamond particles play a toughening role in the diamond-hard alloy composite material.Compared with the traditional sintering method,when the cobalt content is less than or equal to 5wt%,the high temperature and high pressure method can avoid the graphitization of the diamond surface without coating it,and can also reduce the sintering temperature,promote the sintering densification,and improve the mechanical properties of the material.The results of this study provide data for the preparation of the transition layer between the diamond layer and the cemented carbide layer,and provide a solution for improving the difficult situation of deep mining of mineral resources.