机械与热综合活化法制备超细WC-Co粉末

Synthesis of ultrafine WC-Co composites by integrated mechanical and thermal activation process

研究了WO3、Co3O4和石墨混合粉末经高能球磨活化后再分步进行还原和碳化反应制备超细WC Co粉末的过程。结果表明:球磨30h后,粉末粒径达到70～100nm。450～700℃温度范围内球磨粉在流动H2和Ar混合气体中经2h还原时,随着还原温度的升高,WO3还原反应顺序为WO3→WO2.9→WO2.72→WO2→W,700℃时可实现完全还原;Co3O4在450℃完全还原为Co,随着温度的进一步升高和时间的延长,Co与W反应转变为Co3W;最终还原产物由W、Co、Co3W和石墨组成;在700～1000℃温度范围内还原粉在流动Ar中碳化时,随着碳化温度的升高,碳化反应按W(Co3W)→Co6W6C→Co3W3C→W2C→WC的顺序进行,在900℃下还原粉在2h内可完全碳化,得到WC颗粒尺寸约为200～300nm的WC Co复合粉末。

Synthesis of ultrafine WC-Co powders was investigated using WO_3, Co_3O_4 and graphite powders as starting materials by high energy ball milling followed by reduction and carburization. The results show that particle sizes of powder mixtures milled 30h are in the range of 70100nm. When the milled mixture is reduced in a flowing gas mixture of H_2 and Ar at different temperatures ranging from 450 to 700℃ for 2h, the reaction sequence of WO_3 to W appears as WO_3→WO_(2.9)→WO_(2.72)→WO_2→W with the increase of temperature, and WO_3 reduction completes at 700℃. Reduction reaction of Co_3O_4 to Co can be finished in 2h at 450℃ and the reduced Co keeps reacting with W to transform into Co_3W with the increase of reduction temperature and time. The final product of reduction reaction is composed of W, Co, Co_3W and graphite. The reduced mixture is carburized in a flowing Ar in temperature range of 7001000℃, carburization reaction takes place following the routine W(Co_3W)→Co_6W_6C→Co_3W_3C→W_2C→WC, and the carburization reaction completes at 900℃ in 2h. The size of the WC grain in the final WC-Co composite powders is in the range of 200300nm.