TiC含量对WC-8Co超细晶硬质合金力学性能和微观组织的影响

采用放电等离子烧结技术制取不同TiC含量的WC-8Co硬质合金。分析了TiC含量对WC-8Co基硬质合金刀具材料的致密度、力学性能和微观组织的影响。实验结果表明,随着TiC含量增加,WC-8Co硬质合金常温综合力学性能先提高后降低,添加5%(质量分数)TiC的WC-8Co硬质合金具有较好的综合力学性能。当烧结温度和压力分别为1 250℃、50 MPa时,WC-5TiC-8Co硬质合金材料致密度、维氏硬度、断裂韧性以及室温下的抗弯强度分别达到98.85%、19.49 GPa、9.46 MPa·m1/2和1 893 MPa。硬质合金致密化烧结曲线和组织显微形貌的分析结果表明,随着TiC含量增加,硬质合金的致密化烧结的起始温度向更低的温度偏移,Co相流动性变差,从而导致致密化烧结条件变差。试样中孔隙增多,是硬质合金维氏硬度和力学性能下降的主要原因。

Effects of TiC Content on the Mechanical Properties and Microstructure of Ultrafine Grained WC-8Co Cemented Carbides

WC-8 Co cemented carbide with different TiC contents was prepared by spark plasma sintering technology.The effects of TiC content on the relative density,mechanical properties and microstructure of WC-8 Co cemented carbide were analyzed.The experimental results show that with the increase of TiC content,the comprehensive properties of WC-8 Co cemented carbide increase firstly and then decrease at room temperature.WC-8 Co cemented carbide with 5%(mass fraction) TiC has better comprehensive mechanical properties.When the sintering temperature and pressure are 1 250 ℃ and 50 MPa,density,Vickers hardness,fracture toughness and flexural strength at room temperature of WC-5 TiC-8 Co cemented carbide are 98.85%,19.49 GPa,9.46 MPa·m1/2 and 1 893 MPa,respectively.The analysis results of cemented carbide densification sintering curve and microstructure morphology show that with the increase of TiC content,the starting temperature for sintering densification of the cemented carbide shifts to a lower temperature,resulting in the fluidity of Co phase deteriorating and the densification sintering condition worsening.The pores in the samples increase,leading to the decrease of Vickers hardness and mechanical properties of cemented carbide.