原位合成复合粉制备超细WC-Co硬质合金

Ultra-fine Grain Cemented Carbide Fabricated from WC-Co Composite Powder by In-situ Synthesis

摘要:

以偏钨酸铵、可溶钴盐、可溶碳源为原料,经喷雾转化、煅烧、低温还原碳化制备超细晶WC-Co复合粉；采用同样成分配比及工艺,在煅烧后增加短时球磨工艺,制备出另一种超细晶WC-Co复合粉；分别以两种复合粉为原料,用放电等离子直接烧结制备超细WC-Co硬质合金。采用SEM、XRD、钴磁仪、矫顽磁力计、维氏硬度计等对复合粉形貌、合金显微组织与性能进行表征分析。结果表明,未短时球磨的粉末呈现出球形结构,WC颗粒被Co相粘结在一起,可观察到烧结颈并有异常长大晶粒,经过短时球磨工序制备的粉末为分散颗粒,两种粉末中Co相同时以fcc与hcp的结构存在,粉末WC晶粒度约为0.26 μm；未短时球磨的粉末制备的合金存在少量孔隙,致密度较低,有异常长大晶粒。短时球磨能有效提高粉末颗粒的分散性,减少烧结体中的显微组织缺陷,制备的合金综合性能得到提高。

Abstract:

Using ammonium metatungstate, soluble cobalt salt, soluble carbon as the raw materials, ultrafine WC-Co composite powder was synthesized by spraying conversion, calcination, in-situ reduction and carbonization route. The composite powder fabricated by the similar route, only increased a short-time ball milling process after the calcination, was more disperse. Ultrafine WC-Co cemented carbides were prepared by spark plasma sintering with this two kinds of powders. The morphology, microstructure and mechanical properties of composite powders and cemented carbides were characterized by SEM, XRD, Vickers hardness tester and so on . The results show that the composite powder fabricated via the route without short-time ball milling process is spherical and has obvious sintering characteristics. WC particles are bonded together, the sintering neck and abnormal grain growth can be observed obviously. Powder fabricated via the route with a short-time ball milling process is more disperse. The fcc-Co and hcp-Co were existed in all two kinds of powders, the grain size of WC is 0.26 μm. There are a few pores exists in the alloy prepared by the spherical composited powder. The density is lower and the WC has abnormal growth. The mechanical properties of the alloy prepared by the dispersed composite powder are better.