Study On Technique And Properties Of WC-10Co Cemented Carbide In Microwave Sintering

WC-Co cemented carbide is a kind of tool materials which has excellent performances, the ultra-fine WC-Co has both higher strength and higher hardness especially. Therefore, it finds wide application in many fields. So far, many methods have been used in fabricating nanoscale WC-Co powders, but some difficulties are encountered to get nanocrystalline WC-Co cermet in sintering. It is because of limitation of sintering technology development. Current technology can not control WC crystalline grain growth during sintering, effectively. Nowadays, international scientific researchers put their emphases on the three aspects: preparation of nano-powder, sintering technology and grain growth inhibitors.In this study, 0.2μm WC and 0.8μm Co powder are used, which are offered by the Xiamen Golden Egret Special Alloy Company. A little inhibitors for grain growth is put in the two kinds of powders, then, they are ground in wet state and mixed in a satellite ball mill. The fine powder mixture ground are pressed into sample chips inφ17×5 mm size. The sample chips are sintered in a microwave field. Finally some parameters of product are measured. The analyses on experimental results are carried out through the measurements of density, fracture toughness, SEM (Scanning Electronic Microscope), Rockwell hardness. Our focus are put on the effects of dewaxing time, sintering temperature, soaking time and other parameters on sintering technique, as well as effects of different inhibitors for crystalline grain growth on performances of WC-Co cermet.The experimental results show that sintering WC-10Co cermet in electric field of microwave has more uniform heating rate. In experiments, dewaxing for 20min at 610℃, then heating to 1320℃for soaking 15 min can get a kind cermet with more uniform WC crystalline grain, which has normal texture, without decarbonation and graphite phases. Suitable amount inhibitors can inhibit WC crystalline growth. Performances of the cermet made with inhibitor are apparently better than that of cemented carbide without inhibitors. When the percentage of inhibitor VC+Cr₃C₂ reaches 0.6% in weight(wt), the WC crystalline grains in cermet are fine and uniform, whose inhibitor effects reaches optimum and whose performances also reach optimum . Small amount of phosphorous (P) doped in WC-Co powders can decrease sintering temperature, effectively, and inhibit growth of WC grain growth to some extents. Doping 0.3%wt P in WC-10Co cermet can get perfect densification at 1250℃of sintering temperature, which decrease sintering temperature by 70℃, whose Rockwell hardness is HRA92.2, whose fracture toughness is 8.71MPa.m^1/2, and whose crystalline grains are fine and uniform.