超细硬质合金WC-10Co-0.8(VC/Cr_3C_2)的烧结特征

超细硬质合金粉末粒度细小,具有高的比表面积和缺陷密度,因而具有较高的烧结活性,呈现出与普通硬质合金不同的烧结特征。因此,针对超细硬质合金特点制定合适的烧结工艺在生产超细硬质合金中是至关重要的。真空烧结超细硬质合金WC-10Co-0.8(VC/Cr3C2)的结果表明:1320℃烧结温度下的超细硬质合金,较1350℃和1380℃的密度和硬度低,WC晶粒细而孔隙度高。1350℃比1380℃具有更高的横向断裂强度(TRS)。WC-10Co-0.8(VC/Cr3C2)超细硬质合金的适宜烧结温度为1350℃。差热分析(DTA)对烧结过程中的热效应分析表明:出现液相温度为950℃,1300℃结束。同时氧化杂质被还原导致质量的损失和气体的产生。晶粒长大抑制剂VC和Cr3C2的加入,提高了氧化物杂质还原温度。

Sintering Features of Ultra Fine Cemented Carbides WC-10Co-0.8 (VC/Cr3C2)

The powders of ultra fine cemented carbides have high specific surface areas and defect concentrations, so it has high sintering activity. The ultra fine cemented carbides present different features from common cemented carbides. It is very important to make out suitable sintering technology for ultra fine cemented carbides. The ultra fine WC-10Co-0.8 (VC/ Cr3C2) cemented carbides were made by vacuum sintering in different temperatures. The results of the microstructure and the mechanical properties have been contrasted. It shows that alloy sintered in 1320℃ has lower hardness and density than that sintered in 1350℃ and 1380℃, but the porosity is higher and WC grain is finer. The alloy sintered in 1350℃ has higher transverse rapture strength than that in 1380℃. The optimum sintering temperature of the ultra fine grain WC-10Co-0.8 (VC/ Cr3C2) cemented carbides is 1350℃. Calorific effects in the course of sintering have been analyzed by differential thermal analysis. Liquid phase emerges in 950℃ and ends in 1300℃.At the same time, the courses of mass loss and the major gaseous phases evolution are also analyzed. Oxidate impurity in the grain growth inhibitors VC and Cr3C2 would increase reducing temperature.