Ni3Al添加量对WC-Co硬质合金中WC晶粒形状的影响

采用粉末冶金制备技术，以粗WC粉末、Co粉和WC＋Ni3Al预合金粉末为原料制备出WC-40vol％（Co—Ni，Al）硬质合金。利用扫描电镜和透射电镜研究了不同NbAl含量对WC-40vol％（Co—Ni3Al）硬质合金中WC晶粒形状的影响规律。结果表明：W在Co粘结相中的固溶度接近25．4wt％，而W在Ni，Al粘结相中的固溶度接近9．5wt％，随着NbAl含量的增加，粘结相对W的固溶度减小，合金中的WC晶粒圆钝和细小；WC晶粒表面上出现明显的台阶。相应的，延长烧结时间，WC—Co—Ni3Al硬质合金具有与WC—Co硬质合金相同的WC生长行为，WC-40vol％（Co—Ni3Al）硬质合金中的WC晶粒表面上的台阶处出现明显的刻面。

Effect of Ni3Al Addition on WC Grain Shape in WC-Co Cemented Carbide

Using coarse WC powder, Co powder and WC＋Ni3Al alloy powder as raw material, WC-40 vol%（Co-Ni3Al） cemented carbide was fabricated by conventiona! powder metallurgy technology. The effect of Ni3A1 content on the WC grain shape in the WC-40 vol% （Co-Ni3Al） cemented carbide was investigated by using scanning electron microscope and transmission electron microscopy. The results show that, the solubility of W in the Co binder phase is close to 25.4 wt%, while that is 9.5 wt% in the Ni3Al binder phase. With the increase of Ni3Al content in WC-40 vol%（Co-Ni3Al） cemented carbide, the WC grains become rounder and finer, which is attributed to the lower solubility of W in binder. The surfaces of WC grains are strongly stepped, consequentially with the increase of sintering time, the steps are strongly micro-faceted. Similar WC grain growth behavior in WC-Co-Ni3Al cemented carbide as that in WC-Co cemented carbide is considered to be responsible for the appearance of the faceted WC shape in WC-40 vol%（Co-Ni3Al） cemented carbide.