两步碳化制备纳米WC粉末及其合金性能

Properties of Ultrafine WC-Co Cemented Carbide Prepared from Tungsten Carbide Nanopowders through a Two-Step Carbonization Method

研究了两步碳化工艺对氢还原/碳化制备的纳米WC粉末及其WC-Co合金性能的影响。结果表明,WC粉末的晶粒聚集和异常粗大颗粒主要是由于碳化初期钨颗粒因烧结合并增粗,而钨粉碳化不完全主要是由于碳化后期的温度偏低,利用先低温碳化后高温碳化的两步碳化工艺不仅能够有效抑制纳米颗粒烧结合并增粗,而且可以使钨粉充分碳化,得到颗粒细小、均匀,W2C含量极少的WC粉末;采用1120℃碳化加1180℃碳化的两步碳化工艺制备出的138 nm的WC粉末,W2C含量少于0.5%(质量分数),以其为原料制备的WC-Co烧结体显微组织结构均匀,为超细晶硬质合金,综合性能优良,洛氏硬度HRA高达93.7,抗弯强度高达4380 MPa。

The effects of a two step carbonization method on properties of tungsten carbide nanopowders and the cemented carbides have been studied. It is shown that the grain aggregation and abnormal coarse grains are mainly due to the sintering combination of agglomerated particles of tungsten or tungsten carbide nanopowders during carbonization process and incomplete carbonization is attributed to the low carbonization temperature. The two step carbonization method （the first step carbonization temperature 1120 ℃, and the second step carbonization temperature 1180 ℃） can effectively inhibit the sintcring combination phenomenon between nanoparticles, and can carburize the tungsten nanopowders fully. Therefore homogenous tungsten carbide nanopowders are obtained and the content of W2C of the nanopowders is only 0.5%. Microstruetures of ultrafine WC-Co sintered composites prepared from the powders through the two step carbonization method are uniform; the properties of the alloy are excellent, and the HRA hardness and bending strength are 93.7 and 4380 MPa, respectively