银铜钛合金与立方氮化硼磨粒钎焊界面显微分层结构及形成机理

Delamination Behavior and Formation Mechanism of the Interfacial Microstructure in the Brazed Joint of Silver-copper-titanium Alloy and Cubic Boron Nitride Grain

采用银铜钛(AgCuTi)合金钎料在加热温度920℃和保温时间5 min工艺下进行立方氮化硼(CBN)磨粒与45钢基体的连接试验,使用扫描电镜、能谱仪、X射线衍射仪分析磨粒与钎料结合界面的组织结构特征与物相组成。结果表明,钎焊过程中,CBN磨粒与AgCuTi合金结合界面出现了显微组织分层现象,从CBN晶体到钎料层由CBN/TiB_2/TiB/TiN/含Ti合金构成,这种过渡结构有利于磨粒与钎料之间的化学键和力学性能过渡。反应热力学分析显示界面反应产物可以依靠置换反应形成;通过对B、N原子的扩散能力差异分析表明,界面新相形核顺序依次为TiN、TiB_2、TiB。

The joining experiments are carried out with heating temperature 920 ℃ for dwell time 5 min on cubic boron nitride （CBN） abrasive grains and 0.45%C steel by using silver-copper-titanium （AgCuTi） alloy as brazing filler. The interfacial microstructure and newly-formed phases are detected with scanning electron microscope （SEM）, energy dispersion spectrometer （EDS） and X-ray diffraction （XRD）. The results show that the delamination phenomenon in the interfacial layer takes place during brazing. From CBN grain to the filler, the interfacial region is composed of a transitional layer, i.e. CBN/TiB2/TiB/TiN/Ti contained allay, which has the remarkable advantage in improving the performance of the brazed joint. The interfacial compounds could be formed in virtue of the displacement reaction according to the thermodynamic analysis. Meanwhile, the formation sequence of the reaction products （TiN TiB2, TiB） is determined by the difference in the diffusion behavior of B and N atoms.