微波烧结制备WC-12Co硬质合金

Fabrication of WC-12Co cemented carbide by microwave sintering

以88%WC+12%Co混合料粉为原料,采用微波烧结制备WC-12Co硬质合金,研究烧结温度与保温时间对合金密度和硬度以及显微组织的影响。结果表明,在1400～1475℃范围内,随烧结温度升高,WC晶粒长大不明显,合金密度和硬度增大。在1475℃的烧结温度下保温0min,烧结周期1.5～2h,烧结合金的相对密度达99.8%,硬度为87.5HRA,烧结样品显微组织结构均匀,但保温时间超过30min后由于晶粒异常长大以及钴相分布不均匀,导致合金的密度和硬度急剧下降。采用辅助加热材料和保温材料以及设计合理的样品摆放,可降低样品中不同部位的温度梯度,从而获得形状良好的合金样品。

Microwave sintering technique was used to consolidate WC-12Co hard alloy,and the effects of sintering temperature and holding time of temperature on the density,hardness and microstructure of the prepared hard alloy were studied to enhance its performance and decrease the production cost. It is obvious that the WC grains grow slightly,the density and hardness of the alloys is increasing. Experiment evidently shows that the alloys with relative density as high as 99.8%,HRA 87.5 and homogeneous microstrue as well could be achieved when sintered at 1 475 ℃ without holding stage and the overall sintering cycle is in the range of 1.5？2 hours. However the abnormal grain growth and Co phase inhomogeneous distribution are observed,which cause decreasing of density and hardness,in case of temperature holding over than 30 min. Temperature gradient in samples is depressed after using auxiliary heating material/thermal insulator and placing samples properly,and as a consequence the sintered parts remain a good geometrical shape.