烧结工艺对低Co超细晶硬质合金性能的影响

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

低Co超细晶硬质合金具有比常规的超细晶硬质合金更高的硬度、耐磨性、红硬性,在精密机械、加工刀具、特种耐磨材料及零件、拉拔模具等领域有其独特的优势和广泛的应用。本文以超细WC粉和球形Co粉为原料,采用真空烧结或低压烧结制备低Co超细晶硬质合金。采用低压烧结技术可成功制备出硬度为2110 HV30,矫顽力为55.7 kA/m,抗弯强度为2 250 MPa的低Co超细晶硬质合金。采用SEM、金相显微镜、维氏硬度计、矫顽磁力仪、材料实验机等研究烧结工艺对合金显微组织和物理机械性能的影响。结果表明:提高烧结温度或采用低压烧结,可以使低Co超细晶硬质合金中的孔隙度减少,强度提高。低压烧结制备的合金晶粒度大于真空烧结制备的合金晶粒度,但是采用真空烧结制备的合金中易出现WC晶粒异常长大现象。

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.