摘要
采用光学金相检测、扫描电镜分析、能谱分析等方法对WC-6Co硬质合金渗碳处理后的成分和梯度组织结构进行分析。结果表明:对硬质合金渗碳处理后可形成显微组织和钨、钴含量的梯度分布,其特征是合金表层和次表层的η相已经完全消失,属正常的WC+γ两相组织,合金的芯部依然是含η相的三相组织,中间形成了一个富钴层;碳原子的扩散和液相钴的流动是形成梯度的原因;在各渗碳温度下,合金的梯度结构厚度均随渗碳时间的增加而增加;在渗碳时间和渗碳温度相同的情况下,合金的梯度层厚度均随合金初始总碳含量的增加而增厚。渗碳处理后外表面的WC晶粒可能会产生一定的粗化现象。
A WC-Co gradient cemented carbides was prepared by carburizing WC-Co cemented carbides with different carbon content. The microstructure of the alloy was investigated by optical microscopy, SEM and EDS analysis. The results show that microstructure with gradient tungsten content and cobalt content is obtained by carburizing the WC-Co cemented carbides with lower carbon content. The microstructure of the carburized layer with gradient characteristics consists of the surface layer without η phase and the cobalt-rich sub-surface layer with normal WC ＋ γ phases, and tungsten content slightly decreases but cobalt obviously increases from surface layer to core, a cobalt-rich layer forms in the middle layer, whereas η phase still exists in the core. The formation of gradient microstructure is possibly attributed to the inward carbon diffusion and the inward flow of liquid cobalt during carburization. The results also show that the thickness of gradient structure increases with the increase of carburizing time and the carbon content of the original WC-Co cemented carbides in the same conditions. A certain degree of coarsing of WC grain in the surface layer is observed for carburized cemented carbides.
出处
《材料热处理学报》
EI
CAS
CSCD
北大核心
2008年第1期116-119,123,共5页
Transactions of Materials and Heat Treatment
基金
国家自然科学基金资助项目(50323008)
关键词
硬质合金
渗碳处理
梯度组织
cemented carbides
carburizing treatment
gradient structure
