SPS Sintering Process And Properties Of Ultra-fine Grained WC-based Cemented Carbide Tool Materials

In order to improve the comprehensive mechanical properties of cemented carbide,an ultrafine grained cemented carbide material with high hardness and high toughness was fabricated.We take WC-Co cemented carbide as the research object and combine the advantages of SPS to improve the properties of cemented carbide by adding inhibitor VC and reinforcing phase CBN,and study its mechanical properties and microstructures.The effect of Co content on mechanical properties and microstructure of WC-Co cemented carbide was studied.The experimental results show that with the increase of Co content,the hardness of WC-Co cemented carbide decreases,but the fracture toughness,flexural strength and densification degree increase.Meanwhile,the average grain size of WC increases from 227 to 374 nm and the mode of crack propagation gradually changes from crack deflection to mixed mode of crack deflection and crack bridging.The effects of VC and CBN content on the properties of the materials were investigated.With the increased of VC content,the WC grain was reduced and the density and mechanical properties of the material were deteriorated.The phase composition of the material was analyzed by XRD,and the chemical compatibility between the components was good.Comparing WC-6Co with WC-6Co-0.2VC,the hardness and fracture toughness of the latter were improved.When the BN content was 1wt.%and the VC content was 0.2wt.%,the cemented carbide material was optimal,and its WC grain size,density,hardness and fracture toughness are 247 nm,98.3%,20.17±0.5 GPa and 12.19±0.12 MPa m^1/2;The bending tests were carried out at different temperatures.When the ambient temperature was above 400?,the material began to oxidize,the surface volume of the material expanded dramatically,the oxide layer fell off or obvious cracks were formed.The friction and wear properties of different cutting tools were studied.When cemented carbide and bearing steel were dual pairs,the friction coefficient and wear rate increased with the increase of Co content,and the main wear form was abrasive wear.When titanium alloy ball and stainless steel ball were friction pairs,the friction coefficient fluctuates little with the change of Co content,and the wear form was mainly the combination of adhesion wear and abrasive wear.At the same time,it was found that the sliding speed and normal load also had a great influence on the wear resistance of the material.Finally,We found that the wear rate and friction coefficient of WC-8Co-0.2VC-1BN were lower than those of commercial YG8 by comparing different cutting tools.Adding CBN to WC-8Co could reduce the friction coefficient but which would increase the wear of cemented carbide.Comparing the cutting performance of cemented carbide tools with different Co content,We found that the cutting performance of the tools was the best when the Co content was8wt.%.The main wear forms of the tools were abrasive wear,adhesion wear and oxidation wear.As the depth of cut and the cutting speed increase,tool wear increases and tool life decreases.A Taylor equation between cutting speed,depth of cut and tool durability was established.According to the results of orthogonal experiments,the equation of cutting force of the tool was established for reference for subsequent research.Comparing the cutting life of different cutting tools,We found that CYG8 had the highest service life and commercial YG8 had the lowest service life.Comparing the wear resistance of cutting tools,it could be seen that CYGVB8 cemented carbide had the best wear resistance,followed by CYGV6.CBN could enhance the wear resistance of cutting tools and refined grain could enhance the bonding strength of materials.