高温钎焊立方氮化硼界面微结构

Microstructure of high temperature brazing cubic boron hitride grits

以Ag Cu Ti合金为钎料采用真空钎焊的方法在优化的钎焊温度和时间下 ,实现了立方氮化硼 (CBN)与砂轮基体的牢固连接。运用扫描电镜 (SEM)、X射线能谱仪(EDS)及X射线粉末衍射仪 (XRD)对连接界面的微观组织以及CBN表面生成物的三维形貌、化学成分、物相结构进行了综合分析。结果表明 ,钎料中的元素Ti向CBN表面扩散富集 ,生成了针状TiB2 和TiN ,在磨粒与钎料界面形成化学冶金结合 ,这是CBN与Ag Cu Ti钎料间有良好浸润性和高结合强度的主要原因。

In order to develop new generation monolayer brazed CBN (cubic boron nitride) grinding wheels, Ag-Cu-Ti active filler alloy was utilized to braze CBN grits to steel substrate in vacuum furnace. The microstructure and the element distribution of the joining interface, as well as the topography and the phase structure of the compounds on the surface of brazed CBN grits, were analyzed by scanning electron microscopy, energy dispersion spectrometer and X-ray diffraction. The results show that Ti in the filler alloy transfers preferentially to the surface of the CBN grit to form a layer of needle-like Ti-nitride and Ti-boride compounds by the interaction reaction between Ti and N (or B) at high temperature. Thus, the chemical metallurgical joining is formed in the interface between CBN grits and Ag-Cu-Ti alloys. Finally comparative grinding tests were performed with monolayer brazed CBN grinding wheels and electroplated ones, and the result indicates that the brazed wheels show higher joining strength to the CBN grits than the latter.