The SPS Preparation Process,Microstructures And Properties Of Binderless Cemented Carbide

Binderless cemented carbide refers to Co doping of 0.5 wt.%or less.Binderless cemented carbide material has high hardness,strength,good wear resistance and thermal conductivity,so it has been the important direction of the cemented carbide development.Because of the less of the binding phase,the style of the grow up in sintering is solid phase grew up.So high requirements are putting forward on the size of powders,sintering equipment and sintering process.In the present study,WC-Co and WC-Co-Ti(CN)composites were prepared by using high energy ball-milling and spark plasma sintering method with WC(2 ?m),Co and Ti(CN)raw powders.And the influence of high energy ball-milling process,sintering temperature,holding time,Co contents and Ti(CN)contents on the sintering densification,microstructure and mechanical properties of the WC material were studied in detail.This paper has an important guiding significant on the production and application of the WC cemented carbide with high property.The experimental results were shown as following.(1)The diamater of WC powder can achieve 150 nm from 2 ?m under the high energy ball-milling which the ratio of ball was 10:1 and the milling time was 60h.(2)With the increase of the sintering temperature,the relative density,Vikers hardness and fracture toughness of the material were increased.And with the increase of the holding time,the relative density,Vikers hardness and fracture toughness of the material all first increased and then decreased.In the sintering temperature of 1500? and holding time at 3 min of SPS,the relative density,porosity,Vickers hardness,fracture toughness and grain size of WC material were 98.72%,0.56%,25.02 GPa,7.82 MPa·m1/2 and 210 nm.(3)The doping of a small amount of Co can greatly decrease the sintering shrinkage temperature,accelerating the WC sintering densification process.But with the increase of Co content,grains of materials had an abnormal grew up phenomenon.And the hardness of material presented first increased and then decreased.When the Co doping was 0.8 wt.%,the relative density,Vickers hardness,fracture toughness and grain size of WC material were 98.93%,24.64 GPa,8.01 MPa·m1/2 and 520 nm.The material phase was WC,and there were no Co,W2C and ? phase appeared.(4)Adding Ti(CN)can promote the densification of WC sintering,and it can also decrease the sintering temperature of WC-0.5Co-xTi(CN)composite.With the increase of the content of Ti(CN),the grains of materials had an abnormal grew up phenomenon and the wear characteristics property presented first increased and then decreased.When adding 5 wt.%Ti(CN),the relative density,Vickers hardness,fracture toughness the coefficient of friction,volume wear rate and grain size of WC-0.5Co-xTi(CN)composite were 99.15%,24.03 GPa,6.60 MPa·m1/2,0.64,1.2126×10-7 mm3/(N·m)and 380 nm.The phases of composite were WC,Ti(CN),(W,Ti)C and TiC.