Effects of sintering on properties of ultrafine cemented carbide with low cobalt content

Low Cobalt ultrafine cemented carbide has higher hardness,higher red hardness and better wear resistance than conventional ultrafine cemented carbide,therefore it is widely used as precision parts,cutting tools,special wear resistant material and components as well as drawing dies,etc.In the present study,2.5% Co ultrafine cemented carbide was fabricated by low pressure sintering using ultrafine WC powders and spherical Co powders as raw materials.The samples density,porosity,coercive force,transverse rupture strength and hardness were measured by using scanning electron microscope,metallograph,vickers hardometer,mechanical test system,etc.The effects of sintering technology on properties of low cobalt ultrafine cemented carbide were studied.The micro-morphology of raw material powders and the microstructure of cemented carbides were studied by SEM.The results show that,the hardness,transverse rupture stress and coercive force are 2110 HV30,2 250 MPa and 55.7 kA/m,respectively,increasing sintering temperature or using low pressure sintering can reduce pores in cemented carbides and then improve their strength;the WC average particle size of cemented carbide sintered in low pressure sintering furnace is larger than those sintered in vacuum furnace and there is the phenomenon of abnormal growth of WC in the alloys sintered in vacuum furnace.