Effect of Carbon Content on Microstructure and Properties of Ultrafine WC-12％ Co Cemented Carbides
Eight groups of WC-12％Co cemented carbides with different carbon contents were prepared by mixing,pressing,and hot isostatic pressing sintering.The influences of carbon content on the microstruc-ture and mechanical properties of the cemented carbides were analyzed using metallographic microscope,scanning electron microscope,hardness tester,and electromechanical universal test machine.The results show that the WC-12％Co cemented carbides with carbon contents of 5.26％～5.42％are in the WC+γ two-phase zone.When the carbon content is less than or equal to 5.22％,the cemented carbide exhibits flocculent and needle like decarburization phases.When the carbon content is greater than or equal to 5.46％,black flocculent carburized phase appears in the cemented carbides,accompanied by the appearance and aggregation of coarse grains and the segregation of cobalt.As the carbon content gradually increases,the WC grains gradually grow larger,the crystallization tends to be complete,the grain edges tend to be straight,and the grain boundaries become clearer.When the carbon content reaches 5.54％,rounded cor-ners appear at the edges of the WC grains.The cemented carbides with carbon contents of 5.26％～5.42％are in WC and Co two-phase zone,exhibiting superior comprehensive mechanical properties,with hardness maintained at 1 777～1 695 kg/mm2 and bending strength of 3 357～3 290 MPa.
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