Pressing the coarse-grained WC−10Co cemented carbide assisted by ultrasonic vibration
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摘要: 为改善粗晶WC−10Co硬质合金在常规压制过程中粉末流动性差、颗粒大小分布不均匀以及合金力学性能差等问题，提出了一种纵向超声辅助压制的工艺方法，研究了压制力、高径比、预压超声时间以及超声振幅等因素对压坯密度、表面质量和合金力学性能的影响。结果表明，与常规压制相比，在超声振动作用下，粉末颗粒发生剧烈碰撞，颗粒间流动性增强，压制力在80～100 MPa之间，压力越大，密度增益越明显；减小高径比，增加预压超声时间，增大超声振幅，压坯密度提升显著；在超声振动作用下，压坯表面质量有所提升，压坯弹性后效下降0.16%；烧结后合金孔隙减少，晶粒大小分布均匀，粗大晶粒减少，在硬度和密度变化较小的情况下，断裂韧性提升了5.83%～16.10%，抗弯强度明显下降。Abstract: The suppression technology assisted by longitudinal ultrasonic vibration was proposed to solve the problems of poor powder fluidity, uneven particle size distribution, and poor mechanical properties for the coarse-grained WC−10Co cemented carbides. The effects of compression force, height-diameter ratio, ultrasonic time of preloading, and ultrasonic amplitude on the compact density, compact surface quality, and mechanical properties of the alloys were discussed. The results show that, compared with the conventional pressing, the powder particles have the violent collision under the effect of ultrasonic vibration, enhancing the fluidity between particles. The density increases with the pressing force increase from 80 to 100 MPa. The compact density increases significantly, when the height-diameter ratio reduces, the ultrasonic time of preloading increases, and the ultrasonic amplitude increases. At the same time, the surface quality of the compacts is improved, and the elastic aftereffect is decreased by 0.16%. The pores of the alloys are reduced, the grain size is evenly distributed, and the coarse grain is reduced after sintering. With the little change in hardness and density, the fracture toughness increases by 5.83%~16.10%, while the bending strength decreases obviously.
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Key words:
- cemented carbides /
- ultrasonic vibration /
- fluidity /
- compact density /
- mechanical properties
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图 1 实验用粗晶WC–10Co混合料粉末扫描电子显微形貌：（a）WC粉；（b）Co粉；（c）WC−10Co混合料
Figure 1. SEM images of the coarse-grained WC−10Co mixture powders for experiment: (a) WC powders; (b) Co powders; (c) WC−10Co mixture
图 5 预压超声时间与压坯密度之间关系
Figure 5. Relationship between the ultrasonic time of preloading and billet density
图 6 压坯与模壁接触情况：（a）常规压制表面；（b）超声压制表面
Figure 6. Contact between the compact and die wall: (a) conventional pressed surface; (b) ultrasonic pressed surface
图 8 合金横截面断口金相组织：（a）常规压制；（b）超声压制
Figure 8. Metallographic images of the alloy fracture in cross section: (a) conventional pressing; (b) ultrasonic pressing
图 9 WC−10Co硬质合金扫描电子显微形貌和WC晶粒尺寸分布：（a）,（b）常规压制；（c）,（d）超声压制
Figure 9. SEM images and WC grain size distribution of the WC−10Co cemented carbides: (a), (b) conventional pressing; (c), (d) ultrasonic vibration pressing
表 1 原始粉末性能参数
Table 1. Performance parameters of the raw powders
原料 费氏粒度 / μm 质量分数 / % 松装密度 /
(g·cm−3)总碳 游离碳 氧 WC 9.6 6.11 0.01 0.01 5.7 Co 1.2 0.02 — 0.30 — 
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表 2 常规压制与超声压制WC−10Co硬质合金力学性能
Table 2. Mechanical properties of the WC−10Co cemented carbides by conventional pressing and ultrasonic pressing
试样 密度 / (g·cm−3) 硬度，HV20 断裂韧性 / (MPa·m2) 抗弯强度 / MPa 常规压制 14.58 1158 20.97 2544 14.57 1170 22.28 2556 14.57 1161 21.02 2420 超声压制 14.62 1163 23.67 2427 14.60 1156 23.58 2150 14.62 1159 24.34 2356
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