放电等离子烧结制备超细晶WC-3Co硬质合金的组织和性能

采用高能球磨制备纳米WC-3Co粉末,再通过放电等离子烧结(spark plasma sintering,SPS)制备超细晶WC-3Co硬质合金。研究SPS工艺参数对合金致密度、显微组织和力学性能的影响,并对SPS和热压工艺(hotpressing,HP)进行对比。结果表明:SPS可实现WC-3Co粉末的低温快速致密化。升高温度或提高压力都使得合金的致密度提高,同时导致WC晶粒长大。SPS较HP升温速率快且烧结时间更短,合金组织更加均匀,在1 300℃保温5 min、烧结压力为40 MPa的条件下所制备的合金具有最佳综合性能,其平均晶粒度为0.32μm,相对密度、硬度、抗弯强度、断裂韧性分别为99.3%、2257 HV30、1 906 MPa、10.36 MPa.m1/2。而在1 450℃、压力为50 MPa、保压5 min条件下,热压合金的致密度、硬度和断裂韧性分别为99.6%、2 264 HV30和11.01 MPa.m1/2,但抗弯强度只有1 301 MPa,平均晶粒度为0.47μm。

Microstructure and properties of superfine WC-3Co cemented carbides prepared by spark plasma sintering

WC-Co mixed powders were prepared by high-energy ball milling,and then spark plasma sintering(SPS) process was used to prepare superfine WC-3Co cemented carbides.The effects of process parameters on the density,microstructure and properties of WC-3Co cemented carbides were investigated,and both SPS and hot pressing(HP) molding process were compared.The results show that WC-Co mixed powder compacts sintered by SPS can achieve rapid densification at low temperature.The density of WC-3Co cemented carbides and WC grain size increase with increasing sintering temperature and sintering pressure.Compared with HP,SPS has a faster heating rate and shorter sintering time,and can get more uniform microstructure.The best mechanical properties of WC-3Co cemented carbides with grain size of 0.32 m are obtained after sintering at 1 300 ℃ for 5 min under 40 MPa.The relative density,hardness,transverse rupture strength(TRS) and fracture toughness(KIC) are 99.3%,2257 HV30,1 906 MPa and 10.36 MPa.m1/2,respectively.However,higher density,hardness and fracture toughness but poor TRS are obtained when WC-Co mixed powder compacts are sintered by HP.Its relative density,hardness,TRS and fracture toughness are 99.6%,2 264 HV30,1 301 MPa and 11.01 MPa.m1/2,respectively,and grain size is 0.47 m.