烧结曲线(MSC)在200nm WC-Co硬质合金晶粒长大模拟中的应用

Sintering Curve during Simulation of Grain Growth of 200 Nanometer WC/Co Hardmetal

利用Master S intering Curve晶粒长大方程模拟了200 nm WC-Co硬质合金固相烧结和液相烧结过程中WC晶粒的长大曲线,并与实际烧结实验相比较。烧结实验选用的WC的粒度为200 nm,采用球磨混料,经过普通模压,压制压力为200 MPa,制备出直径为20 mm、厚度为3~5 mm的压坯。烧结实验在管式炉中进行,烧结气氛为高纯氢气,加热速率为10℃.m in-1,烧结时间为10 m in。结果表明：Master S interingC ruve模型在WC-Co硬质合金烧结过程中具有很好的适用性。计算出的晶粒长大随烧结温度的变化与实际烧结实验具有很好的一致性。经过固相烧结,200 nm的WC长大到254 nm,烧结激活能为450 k.Jmol-1,但体积扩散和晶界扩散机制的区别不是很明显。经过液相烧结WC颗粒继续长大到287 nm,此时固液相的界面反应控制整个烧结过程,烧结激活能为474 k.Jmol-1。压坯烧结激活能的增加,将显著抑制在烧结过程中WC晶粒的长大。

In order to control the grain growth,the simulation of 200 nanometer WC grain growth of WC/Co hardmetal during the solid phase sintering and liquid phase sintering process was researched.The research included application of master sintering curve to calculate grain growth of WC and comparing with sintering experiment.The particle size of WC used for sintering experiment and mixing by ball milling was 200 nm.The green compacts with thickness of 3~5 mm were prepared through ordinary molding,and the pressing pressure was 200 MPa.Sintering experiment was carried out in tubular furnace,while sintering atmosphere was high purity hydrogen and heating rate was 10 ℃ · min-1.Every sample preserved in preset temperature for 10 min.The result showed that the simulation results had a good consistency with the actual sintering experiment.After solid phase sintering process,the WC grains grew from 200 nm to 254 nm and the sintering energy was 450 kJ · mol-1;and then after liquid phase sintering process,the WC grains reached 287 nm and the activation energy for sintering was 474 kJ · mol-1.