碳化工艺对细晶碳化钨粉末特性与硬质合金晶粒异常长大的影响

Effect of Carbonization Process on Characteristics of Fine WC Powder and Abnormal Grain Growth of Cemented Carbides

硬质合金异常长大晶粒是脆性断裂的断裂源。本文采用相同的钨粉原料,将其分为三组进行碳化,碳化工艺分别为1750℃保温1 h、1650℃保温1.5 h和1550℃保温2 h,制得三种细碳化钨粉,将所得碳化钨粉经相同工艺制备成WC-10%Co硬质合金,比较粉末特性以及合金组织的差异。研究结果表明:不同碳化工艺制备的碳化钨粉末及其所制成的合金表现出不同的性能特性:1550℃保温2 h,碳化钨粉末存在W2C相,合金晶粒异常长大,最大为21μm;1650℃保温1.5 h,合金晶粒异常长大,最大为18μm;1750℃保温1 h,合金晶粒异常长大,最大为14μm。高温短时间碳化有利于获得结晶完整、亚晶尺寸大的碳化钨粉末,其制备的合金金相组织结构均匀,减少了合金晶粒异常长大。

The abnormal grain growth of cemented carbides is the root cause of brittle fractures.In this study,the same tungsten(W)powder was distributed into three groups for carbonization.The carbonization process was performed for 1 h at 1750℃,1.5 h at 1650℃,and 2 h at 1550℃,during which three kinds of fine WC powder were prepared.Then,the WC powder was prepared into WC-10%Co cemented carbides through the same process.The properties of WC powder and differences in the microstructure of cemented carbides were compared.The results show that the WC powder prepared by different carbonization processes and the prepared cemented carbides show different properties.To be specific,WC powder prepared at 1550℃for 2 h shows W2C,and the maximum abnormal grain growth of cemented carbides is 21μm.The cemented carbides of WC powder prepared at 1650℃for 1.5 h display a maximum abnormal grain growth of 18μm,and those of WC powder prepared at 1750℃for 1 h present a maximum abnormal grain growth of 14μm.Therefore,it can be concluded that high temperature and short duration of carbonization are conducive to obtaining WC powder with complete crystals and large sub-grain size,and the cemented carbides prepared are uniform in microstructure,which subdues the abnormal grain growth.