Study On Synthesis And Properties Of High Toughness Polycrystalline Diamond

Polycrystalline diamond plays an increasingly important role in modern industry due to its high hardness,good wear resistance,high thermal conductivity,long service life and good processing quality.In this paper,the medium-bonded polycrystalline diamond with Si-Ti-B-Al system and Si-SiC-B system as binder were prepared by HPHT,and the sintered polycrystalline diamond with Co-Ti-W system as binder was prepared.The effects of sintering temperature,binder system and content on the properties of polycrystalline diamond were investigated.The medium-bonded polycrystalline diamond was used as the basic component to introduce the reinforcing phase SiC whisker.The effect of SiC whisker content on the mechanical properties of polycrystalline diamond and the toughening mechanism of SiC whiskers were investigated.The density,flexural strength and wear ratio of the medium-bonded polycrystalline diamond increased first and then decreased with the increase of sintering temperature.When the sintering temperature was 1450°C and the binder content was 15 wt.%,Si-Ti-B-Al type polycrystalline diamond had the best comprehensive performance.The density of the sample was 99.7%,the flexural strength was 675 MPa,the wear ratio was 12.88,the hardness was 53.3 GPa,and the fracture toughness was 4.50 MPa·m^1/2.Under the same conditions,the density of Si-SiC-B type polycrystalline diamond was99.75%,the flexural strength was 700 MPa,the wear ratio was 13.38,the hardness was58.6 GPa,and the fracture toughness was 5.23 MPa·m^1/2.The density,flexural strength and wear ratio of sintered polycrystalline diamond prepared by using Co-Ti-W system as binder increased first and then decreased with the increase of sintering temperature.When the sintering temperature was 1450°C and the binder content was 13 wt.%,Co-Ti-W type polycrystalline diamond had the best comprehensive performance.At this time,the density of the sample was 99.65%,the flexural strength was 637 MPa,the wear ratio was 11.80,the hardness was 63.2 GPa,and the fracture toughness was 5.42 MPa·m^1/2.Under this condition,the initial oxidation temperature of Co-Ti-W type polycrystalline diamond was 764°C,which is improved compared with the traditional sintered polycrystalline diamond（700°C）,but its thermal stability was still much lower than that of the medium-bonded polycrystalline diamond（>900°C）.The fracture toughness of PCD-SiC_w composites increased first and then decreased with the increase of SiC_w contents.When the SiC_w content was 10 wt.%,the fracture toughness of PCD-SiC_w composites reached the maximum value of 7.3MPa·m^1/2.It was much higher than PCD(⁴.5 MPa·m^1/2)without added SiC_w.The toughening mechanism of SiC_w were mainly crack deflection,whisker pull-out and whisker bridging.