纯氧气氛下硬质合金及其原料的热稳定性

来源期刊：中南大学学报(自然科学版)2004年第6期

论文作者：张立 陈述 SCHUBERT W D 黄伯云 吴恩熙

文章页码：931 - 934

关键词：硬质合金;稀土;差热分析;热稳定性

Key words：cemented carbides; rare earth; DTA; thermostability

摘    要：采用差热分析法研究了纯氧气氛下WC粉、Co粉、RE-Co预合金粉、WC-8Co硬质合金的热稳定性以及稀土对硬质合金热稳定性的影响。研究结果表明:费氏粒度分别为0.51μm和0.93μm的WC粉和Co粉分别在392℃和282℃就开始明显氧化,由于湿磨过程的活化作用与破碎作用,硬质合金混合料的热稳定性进一步降低,因此,在制备硬质合金混合料特别是超细硬质合金混合料的过程中对湿磨介质、混合料干燥方式与干燥温度等应进行严格选 择与控制;在湿磨过程中,稀土以RE-Co预合金粉形式加入制备成含稀土的硬质合金,在混合料制备过程中RE-Co预合金粉不会发生明显氧化,其热稳定性与硬质合金基本原料WC粉和Co粉的热稳定性相当;稀土的添加量对WC-Co硬质合金的热稳定性影响不大,在合金中加入稀土不能使合金的明显氧化起始温度得到显著提高;在约700℃,WC-8Co硬质合金发生明显氧化,因此,WC-8Co硬质合金的实际使用温度应低于700℃。

Abstract: Differential thermal analysis (DTA) was used in the study of the thermostability of WC powder, Co powder, RE-Co powder and WC-8%Co cemented carbides, and the effect of rare earth on the thermost ability of cemented carbides in oxygen. The results showthat WC withd FSSS of 0.51μm and Co withd FSSS of 0.93μm are oxidized at 392℃and 282℃, respectively. Because of the activation and fragmentation during the wet-milling, the thermost ability of cemented carbide slurry becomes worse. Therefore, it is very important to choose the wet-milling liquid media, the way to dry the slurry and the drying temperature during the preparation of the cemented carbide powders, especially the ultra fine cemented carbide powders. When rare earth is added in the form of rare earth and cobalt pre-alloyed powder in the preparation of rare earth doped cemented carbide, the pre-alloyed powders are notoxidized markedly just like tungsten carbide and cobalt. Rare earth in cemented carbide cannot visibly improve the thermostability of cemented carbide in oxygen. WC-8%Co ce-mented carbide is oxidized at about 700℃. Therefore, the tool prepared by WC-8%Co cemented carbide should be used below 700℃.