Ni-Cr合金真空钎焊金刚石界面反应的热力学与动力学分析

采用Ni-Cr合金钎料，适当控制钎焊工艺，实现了金刚石与钢基体的高强度连接。采用扫描电子显微镜(SEM)和能谱仪(EDS)及X射线衍射结构分析了真空加热条件下，Ni-Cr合金钎料与金刚石之间的界面反应，探讨了钎料与金刚石界面处碳化物的形成机理。结果表明，Ni-Cr合金钎料中的Cr和少量Si在金刚石表面富集并与金刚石中的C发生反应生成Cr7C3、Cr3C2碳化物，其中Cr7C3呈笋状生长，Cr3C2呈片状，可能有少量SiC生成。金刚石与钎料的界面形成了金刚石＼SiC、Cr3C2＼Cr7C3钎料的梯度材料，实现了Ni-Cr合金与金刚石的冶金结合。

Thermodynamic studies on interfacial reactions between diamond and Ni-Cr filler metal in vacuum brazing

The high-strength bonding between diamond grit and steel matrix was realized by using Ni-Cr filler metal under controlled brazing technique. The interface between Ni-Cr filler metal and diamond, also the forming mechanism of carbide layer between filler and diamond surface under the condition of vacuum heating were analyzed by using SEM, EDS and X-ray diffraction. Results show that Cr and small quantity of Si of the Ni-Cr filler metal are accumulated on the diamond surface. Meanwhile, the carbide of Cr_7C_3, Cr_3C_2 , and small quantity of SiC are formed by reacting among Cr,Si and C of the diamond. Especially, the Cr_3C_2 distributes as flake on the diamond surface and the Cr_7C_3 distributes as needle-like on the top of Cr_3C_2 . As a result, metallurgical bonding is produced between filler metal and diamond through the forming the serial of diamond-SiC-Cr_3C_2 -Cr_7C_3 between the interface of diamond and filler metal.