(1. 中南大学 粉末冶金国家重点实验室，长沙 410083；2. 湘潭大学 机械工程学院，湘潭 411105；3. 株洲硬质合金集团有限公司，株洲 412000)
摘 要: 对缺碳硬质合金采用渗碳处理制备梯度硬质合金，利用显微组织分析和维氏硬度测试等方法，研究渗碳工艺对梯度硬质合金的梯度结构和硬度的影响。结果表明：渗碳处理后随着渗碳时间延长，梯度层厚度增大，长时间渗碳还会出现梯度结构消失现象；渗碳时表面层WC晶粒长大，且渗碳时间越长晶粒长大越严重；渗碳后梯度硬质合金的表面硬度明显提高；渗碳后合金的表面硬度明显高于烧结态合金的表面硬度；随着渗碳时间的延长，合金表面硬度先增大后减小；合金的硬度在截面上沿梯度方向呈连续梯度变化，合金表面层因WC含量较高、钴含量较低而具有较高的硬度，中间层因钴含量较高、WC含量较低，其硬度较低。
关键字: WC-Co硬质合金；梯度结构；渗碳；硬度
（1. State Key Laboratory of Powder Metallurgy , Central South University , Changsha 410083, China;2. School of Mechanical Engineering, Xiangtan University, Xiangtan 411105, China;3. Zhuzhou Cemented Carbide Group Ltd., Zhuzhou 412000, China）
Abstract: Gradient cemented carbides were prepared by carburizing carbon-deficient cemented carbides. The effects of carburizing processes on the gradient structure and hardness of WC-Co gradient cemented carbides were investigated by optical microscopy, scanning electron microscopy and Vickers hardness test. The results show that the thickness of gradient structure increases with prolonging of carburizing time and the gradient structure disappears after long time carburizing. WC grains in the surface layer grow after carburizing and the growth degree increases with carburizing time. The surface hardness of as-carburized alloys is obviously higher than that of as sintered alloys, which increases firstly then decreases with prolonging carburizing time. The hardness of as-carburized alloys in the cross section varies continuously and gradiently along gradient direction, namely the hardness is higher in the surface layer for higher WC content and lower cobalt content, which is lower in the middle layer for higher cobalt content and lower WC content.
Key words: WC-Co cemented carbides; gradient structure; carburizing; hardness
