WC-Co硬质合金的相转变

用高温 X射线衍射装置对低碳 WC- 2 0 Co合金混合料进行了从室温到130 0℃连续升温过程的动态相转变研究。结果表明 ,以低碳 WC粉为原料的 WC- Co系合金在真空烧结升温过程中是通过钨和碳原子的扩散作用消耗原料中的游离态钴和WC(90 0℃以下是 W2 C和单质钨 )进行的脱碳型不平衡相转变。除 90 0℃以下由原料中的 W2 C(和单质钨 )及游离态钴生成η1 相外 ,10 0 0℃以上升温过程中生成的高温相η化合物和金属间化合物与原料中固有的 W2 C(和单质钨 )含量无关 ,也与钴的同素异构相变无关。烧结降温期间高温相通过增碳作用平衡转变成游离态钴和 WC,室温合金中的η1 相含量完全取决于原料中 W2 C(和单质钨 )的含量

PHASE TRANSFORMATION IN WC-Co CEMENTED CARBIDES

The phase transformation in low-carbon WC-20Co mixture powder heated continuously from room temperature to 1300℃ was studied by high-temperature X-ray diffraction apparatus.The results show that,there is a decarbonization disequilibrium phase transformation in WC-Co cemented carbides made from low-carbon WC raw powder by means of consuming free cobalt?WC(above 900℃) or W 2C?W(below 900℃) in raw material by diffusion of W and C atoms when vacuum-heating sample,The high-temperature phases η-type compounds and metal-to-metal compounds formed when heating sample to above 1000℃ are all irrelevant to W 2C and W which lead to forming the η 1-phase below 900℃ and to the hcp Co→fcc Co allotropic phase transformation.The phase component in low-carbon WC-Co sample slowly cooled from 1300℃ to room temperature shows that,the high-temperature phases have transformed to free cobalt and WC by carbonization type equilibrium phase transformation when cooling slowly sample and the η 1-phase content in sample at room temperature is decided alone by the W 2C (and W) content in raw material.