WC-Co复合粉的喷雾造粒及松装密度的影响因素

Spray granulation of WC-Co composite powders and influencing factors of apparent density

利用短流程原位反应合成技术制备超细WC-Co复合粉,其平均粒径为300 nm,对此复合粉进行喷雾造粒以制备具有超细结构的热喷涂粉末。采用标准漏斗法测量造粒粉末的松装密度,并利用SEM观察其形貌与结构,结合实验测定结果与理论计算结果研究料浆成分、喷雾干燥温度及初始粉末粒径对造粒粉末松装密度的影响规律。结果表明：料浆固含量最高可达70%（质量分数）,此时造粒粉末松装密度达到2.31 g/cm3;随粘结剂含量的增高,造粒粉末松装密度先增高后降低,最佳含量为2.5%（质量分数）;分散剂最佳含量为1%~2%（质量分数）;干燥温度显著影响造粒粉末形貌结构及松装密度,最佳温度为150℃;喷雾造粒粉末的最高密度实质上取决于初始粉末粒径。

Spray granulation was carried out using the ultrafine WC-Co composite powders with an average particle size of 300 nm as the raw material which was rapidly synthesized by the technique of in situ reactions.The standard funnel method and scanning electron microscope（SEM） were employed to measure the apparent density and characterize the morphologies and structures of the granulated powders,respectively.Moreover,the influences of the slurry composition,the drying temperature and the particle size of raw powders on the apparent density of the granulated powders were studied by combining the experimental and theoretical calculation results.The results indicate that the apparent density of the granulated powders reaches 2.31 g/cm3 as the solid content of the slurry increases up to 70%（mass fraction）.But with the increase of the organic binder content,the apparent density of the granulated powders firstly increases,and then drops down.The optimum binder content and dispersant content is 2.5%（mass fraction） and 1%-2%（mass fraction）,respectively.The spray drying temperature greatly influences the morphology and the apparent density of the granulated powders and the optimum value is 150 ℃.The highest density of granulated powders essentially depends on the particle size of the raw powders.