直接碳化原位合成WC-Co复合粉的反应过程

Reaction process of WC-Co composite powder by direct carbonized and in-situ synthesize

以偏钨酸铵(AMT)、可溶性钴盐、有机碳源为原材料,采用喷雾转化、直接碳化原位合成法,成功制备出WC-Co复合粉末。利用XRD、SEM等分析方法对粉末样品物相组成、微观形貌、粒度分布进行了研究。研究表明,由于Co对W碳化的促进作用,在900℃时,W就被完全碳化为WC,远低于W正常被碳化完全的温度;W的碳化过程主要依靠钨粉颗粒表面与含碳气氛热解后沉积在钨颗粒表面上的碳元素的反应以及碳向钨粉颗粒内部的扩散来实现,属固-固反应;由于生成W2C的自由能比WC的更低,W很快先被碳化为W2C,然后再进一步碳化为WC;W/Co/C碳化反应体系沿WCo3,Co6W6C,W2C-Co,WC-Co步骤进行反应;随着温度的升高,反应体系可不经过前两步,而直接生成W2C-Co,再进一步碳化为WC-Co复合粉。

Using ammonium metatungstate(AMT),soluble cobalt salt,and organic carbon source as the raw materials,the WC-Co composite powder was fabricated by spray conversion method and direct carbonized in-situ synthesize method.The phase compositions,powder morphology of WC-Co composite powder were characterized by XRD,SEM.Results show that W was carbonized completely at 900 ℃ because of the promoting effect of Co phase,the carbonize temperature in this experiment of W was lower than the normal carbonize temperature far;The carbonization process of W depends on the reaction of the surface of tungsten powder particles and carbon which resolved from carbon atmosphere,and the diffusion of carbon to the inside of W particles,was a solid-solid reaction,W was carbonized into W2 C firstly,and then carbonized into WC further because of the Gibbs free energy of W2 C is lower than WC;The W/Co/C system reacted along the specific steps of WCo3,Co6W6 C,W2C-Co and WC-Co;With the increasing of carbonize temperature,the reaction system can skip the first two steps,and generated W2C-Co directly,then carbonized into WC-Co composite powder further.