Research On Preparation Of WC-cBN Composites By Different Sintering Methods

Cemented carbides with superior strength and hardness,high elastic modulus and low thermal expansion coefficient,have been taking an important role in the industrial areas of cutting tools and wear resistant components.However,higher requirements are put forward for material processing with the emergence of various new materials,so conventional cemented carbide is not competent for demanding work.The mechanical properties of WC-Co cemented carbide can be adjusted by changing ductile binder phase Co content and WC grain size.Generally,the toughness increases with the increase of binder phase content and the hardness decreases with the increase of WC grain size.However,Co is rare and expensive resource,reducing corrosion resistance of conventional WC-Co hard materials as binder phase.The substitution of part or all of the cobalt has been investigated in recent years.Due to cubic boron nitride(cBN)has very high hardness which is only next to that of diamond,however its thermal stability and chemical stability are superior to diamond,and it has the potential to reconcile the hardness and toughness of WC-Co composites and to obtain good comprehensive properties as the second phase hard particles.Therefore,WC-cBN composite is expected to become a new generation of outstanding cutting tool material.In the present study,WC,Co,and cBN powders were used as raw materials.WC-cBN composites were prepared using SPS method with different Co contents and at different sintering temperatures.The WC-FeCoNi-cBN composites with partial substitution of Co by metal Fe and Ni were prepared by different sintering methods at different sintering temperatures.The relative density,phase composition,microstructures,mechanical properties and corrosion resistance of the WC-cBN composites were investigated in detail.The experimental results were shown as follows.(1)The best Co content of WC-Co-cBN composites sintered by SPS was 10 wt%.(2)When the SPS sintering temperature was 1250?,the WC-Co-cBN composite material with the size of WC being 223 nm had the best comprehensive performance of which the relative density,Vickers hardness,fracture toughness and flexural strength were 98.0%,23.5 GPa and 13.1 MPa·m1/2,respectively.(3)When the SPS sintering temperature was 1250?,the WC-FeCoNi-cBN composite material with the size of WC being 226 nm had the best comprehensive performance of which the relative density,Vickers hardness,fracture toughness and flexural strength were 97.1%,22.4 GPa and 12.4 MPa·m1/2,respectively.(4)When the HP sintering temperature was 1300?,the WC-Co-cBN composite material with the size of WC being 286 nm had the best comprehensive performance of which the relative density,Vickers hardness,fracture toughness and flexural strength and flexural strength were 99.3%,21.0 GPa,14.9 MPa-m1/2 and 1436 MPa,respectively.