Effect of Ultra-High Pressure Sintering on Microstructure and Mechanical Properties of WC-8Co Cemented Carbide
The effects of different sintering pressures(4.0～6.0 GPa)on the microstructure and mechanical properties of WC-8Co cemented carbide samples were studied by using a cubic press at identical tempera-ture(1 400 ℃)and holding time(6 min).The results show that the sintering of the WC-8Co cemented carbide samples can be completed within 6 min at 1 400 ℃ and ultra-high pressure of 4.0～6.0 GPa.As the sintering pressure increases,the average size of WC grains in WC-8Co cemented carbide samples gradually increases with local WC grains even growing abnormally,resulting in a gradual decrease in the coercivity,Vickers hardness and fracture toughness of the cemented carbide samples.Within the investigated pressure range,the mechanical properties of the WC-8Co cemented carbide samples reach the best at a sintering pressure of 4.0 GPa.And under the testing conditions of a load of 30 kgf(294 N)and a holding time of 10 s,the Vickers hardness and fracture toughness of the sample are 15.2 GPa and 14.9 MPa·m1/2,being very close to the mechanical properties of commercial YG8 cemented carbide(Vickers hardness of 15.6 GPa and fracture toughness of 15.9 MPa·m1/2)under the same testing conditions.As the sintering pressure increases,the fracture forms of the cemented carbide samples gradually transition from the domi-nant intergranular fracture to a combination of intergranular fracture and transgranular fracture,with an increasing proportion of transgranular fracture.
ultra-high pressure sinteringWC-8Cocemented carbidemicrostructuremechanical propertyfracture form
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