粘结相Co的切变机制及微观结构的研究  

Study on Shear Mechanism and Microstructure of Cobalt Binder Phase

作　　者：谢晨辉[1,2,3] 周华堂[1,2,3] 彭宇[1,2,3] 

机构地区：[1]硬质合金国家重点实验室,湖南株洲412000 [2]工业(硬质合金及钨制品)产品质量控制和技术评价实验室,湖南株洲412000 [3]株洲硬质合金团有限公司,湖南株洲412000

出　　处：《硬质合金》2013年第5期242-248,共7页Cemented Carbides

基　　金：湖南省自然科学-株洲联合基金重点项目(12JJ8018)

摘　　要：本文以工业纯钴粉、钴基合金、硬质合金作为研究对象,分别运用X射线衍射、金相、扫面电镜能谱、EBSD等分析技术,并结合晶体学的相关知识研究了钴的基本特性、微观结构及其切变机制。通过研磨工业纯钴粉,比较分析研磨前后X射线衍射分析结果,定性描述了钴粉的α-Co向ε-Co的转变过程;实验制备了不同固溶W含量的Co基合金,并对合金金相组织及相结构进行了分析;对淬火后的WC-10%Co硬质合金,研究了在不同回火温度、时间工艺参数条件下合金粘结相Co的微观组织结构变化规律及其主要影响因素;通过离子束抛光制样,运用背散射电子衍射(EBSD)技术研究了WC-20%Co硬质合金中的α-Co与ε-Co形貌特征及其分布状态。实验结果表明:α-Co结构的稳定性较差,α-Co向ε-Co的转变的相变驱动力仅几J/mol;固溶W含量对钴基合金中晶粒的孪晶组织有重要的影响,Co基合金中固溶的W含量越多其孪晶组织越少,且α-Co含量越多;硬质合金淬火后回火实验说明硬质合金粘结相Co的ε马氏体相变过程既可在较高温度、短时间内形成变温马氏体ε-Co,也可在较低温度、长时间下形成恒温马氏体ε-Co,合金内部组织内应力的释放会引起α-Co向ε-Co的转变;EBSD分析发现硬质合金中粘结相大部分是以α-Co结构存在,ε-Co呈条带状,厚度在2μm以下,长度在6μm左右,主要分布在粘结相与WC相的界面处或较厚钴层的中间部位。文中重点论述了硬质合金ε-Co马氏体的基本特征及其切变机制。The basic characteristic and microstructure and shear mechanism of the binder phase of the industrial pure cobalt powder, cobalt-based alloy and cemented carbide were analyzed by X-ray diffraction （XRD）, metallographic microscope, scanning electron microscopy （SEM） and electron back scattering diffraction （EBSD）. The α-Co to ε-Co phase transition of the industrial pure cobalt powder was studied through the grinding experiment. The phase composition andstructure of cobalt-based alloy with various W contents were researched. Effects of process parameters on the binder phase microstructure and its main influence factors of WC-IO%Co cemented carbide after quenching and tempering were studied. The morphology and distribution of the α-Co phase and ε-Co phase of WC-20% Co cemented carbide after ion beam polishing were analyzed. The results show that the driving force of the α-Co to ε-Co phase transition is only a few J/mol and α-Co phase stability is poor. Twin defects decreases and α-Co phase increases with increasing W concentration. The 8 martensite phase transformation of WC-IO%Co cemented carbide after quenching and tempering can be found under two different conditions that temperature-floating martensitic transformation be formed under high temperature and short time, and isothermal martensite can be formed under low temperature and long time. Alloy internal stress can lead to α-Co to ε- Co phase transition. EBSD analysis shows that most of the binding phase exists in the structure of α-Co phase, and the morphology characteristic of ε-Co tends to show banded shape with 2μm in thickness and about 6 μm in length, and ε-Co is distributed in phase interface between the bonder phase and WC or in the middle region of thick cobalt layer.

关 键 词：粘结相 固溶度 ε-马氏体 切变机制 EBSD 位错 层错 孪晶 

分 类 号：TG135.5[一般工业技术—材料科学与工程]