Effect of Carbon Addition on the Microstructure and Properties of Ultrafine-Grained WC-6Co Cemented Carbide AITranslate

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Chinese Library Classification Number:TG135.5[一般工业技术—材料科学与工程]

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Using ultrafine-grained WC-6Co-0.7Cr₃C₂-0.4VC cemented carbide as the research object,six groups of mixed powders with different carbon additions(mass fraction)were blended,and then cemented carbide samples with different carbon contents were fabricated via pressing and sintering.The effects of carbon addition on the microstructure and physical-mechanical properties of the cemented carbide were analyzed using metallographic microscope,scanning electron microscope(SEM),magnetic saturation tester,coercivity meter,water displacement method,Vickers hardness tester,and mechanical testing machine.The results show that the cemented carbides with carbon additions of 5.74%and 5.78%are in the WC+Co two-phase region.When the carbon addition is below 5.74%,the decarburization phase(ηphase)appears in the substrate.When the carbon addition exceeds 5.78%,the snowflake-like carburization phase(C phase)forms.As carbon addition increases,the relative saturation magnetization of the cemented carbide initially rise gradually and then slightly decreases,while coercivity and density generally decline.The Vic-kers hardness progressively decreases,the fracture toughness initially increases,then decreases,and finally slightly recovers,and the transverse rupture strength(TRS)rises sharply before gradually declining.When the carbon addition is controlled within the range of 5.74%to 5.78%,the cemented carbide remains in the WC+Co two-phase region,achieving an optimal balance of hardness,strength,and toughness.The fracture surface of the cemented carbide with a carbon addition of 5.66%exhibits dotted decarburization phase,which acts as fracture origins and reduces the strength and toughness of the cemented carbide.In contrast,the fracture surface of the two-phase cemented carbide with a carbon addition of 5.74%exhibits a uniform microstructure without defects.However,the fracture surface of the cemented carbide with a carbon addition of 5.86%contains black carburization phase,which degrades the strength,hardness,and toughness of the cemented carbide.