Mechanical Properties And Preparation Of Polycrystalline Cubic Boron Nitride

PcBN has high hardness,high wear resistance,good chemical stability and thermal conductivity,which are suitable for processing all kinds of nodular cast iron,high temperature alloy and other difficult processing materials.But its'poor toughness,difficult to sintering and other problems also limit the application of PcBN.Therefore,to tackle these problems,we use the multi-anvil apparatus to sinter PcBN by high temperature and high pressure sintering method,and study the effect of binder system,content and sintering conditions on the properties of PcBN materials.XRD was used to emphasis explore phases composition,SEM was used to detect microstructures.The results were showed as follows:The main properties of PcBN with Al-Ni-Si₃N₄ as binders are as follows:when the sintering temperature was 1550?.Relative density reached its maximum value of 99.57%.Optimum value of bending strength and Vickers hardness were 456.9 MPa and 43.71 GPa,respectively.Meanwhile,maximum value of fracture toughness was7.45 MPa·m^1/2,and the highest value of abrasive ratio was 1.44.Additionally,the mechanical properties of PcBN improved when Al-Si₃N₄ were used as binders.It was showed that bending strength was increased by 32.5%,reaching 605.3 MPa,compared to unmodified basic binder system.Relative density increased from 99.57%to 99.62%.Vickers hardness reached 54.1 GPa.Also,dense microstructure was obtained,as well as the unchanged fracture mode.Fracture toughness of PcBN slightly reduced,and reached 7 MPa·m^1/2.The main properties of PcBN with Al-Si-SiC as binders are as follows:maximum value of relative density and bending strength were 99.39%and 630.5 MPa,respectively.After incorporating with GO,the bending strength and fracture toughness of cBN/GO composites were improved by 23.5%and 27.5%,while with a little sacrificing of relative density and Vickers hardness.The increase in bending strength was mainly due to the load bearing of GO and the extreme well bonding between cBN matrix and GO.And the improvement of fracture toughness was ascribed to GO bridge,pullout and interface sliding,as well as dissipating the driven force of crack deflection.