碳源对喷雾转化法制备WC-Co复合粉末的影响

摘要

以偏钨酸铵、醋酸钴、有机碳源或炭黑经喷雾干燥后的前驱体粉末为原料,在N2气氛中进行原位还原碳化,制备超细WC-Co复合粉末.采用DSC研究还原碳化过程中的相变过程,并用XRD分析不同工艺下复合粉末的物相组成,利用SEM分析复合粉末经磷酸浸蚀前后的微观形貌,结合纳米测量软件测量浸蚀前后晶粒粒度分布.结果表明:2种碳源的粉末在低于900℃的温度下可发生还原反应,以有机碳为碳源的粉末较炭黑的还原温度低.在950℃的碳化温度条件下,炭黑为碳源的复合粉末所需要的碳化时间长,制备得到的晶粒大,WC的晶粒度为0.29μm,WC-Co复合粉末二次颗粒是由金属钴粘结细小的碳化钨晶粒而成.有机碳制备的晶粒细小并且较均匀,WC的晶粒度为0.16μm,碳化钨晶粒间会形成烧结颈,经过磷酸浸蚀后,其烧结颈结构不会破坏.%In this paper,ultrafine WC-Co composite powders were prepared by in situ reduction of the carbona-tion in N2 atmosphere,with ammonium tungstate acid,cobalt acetate,organic carbon or precursor powder of carbon black by spray drying as raw materials.The phase-change of reduction-carbonization process was studied by DSC.Phase constitution was determined by using x-ray diffractometer.Morphology of the final products be-fore and after etch was observed by using SEM.Particle size distribution of the final products before and after etch was analyzed by nano measurer.Results showed that the different carbon sources of powders can be re-duced at temperatures below 900 ℃.The reduction temperature of organic carbon source is lower than the tem-perature of carbon black.At 950 ℃,composite powders using carbon black as carbon source need long time to prepare WC-Co composite powders.The obtained grains are large and the grain size of WC is 0.29μm.The sec-ondary particles of the WC-Co composite powders are composed of metal cobalt bonding fine tungsten carbide grains.However,the grains of WC-Co composite powders prepared with organic carbon as carbon source are small and uniform.The grain size of WC is 0.16μm.The sintering neck is formed between tungsten carbide and tungsten carbide,which cannot be undermined by phosphoric acid etch.