关键词: 立方氮化硼磨粒, 热力学分析, 显微组织分层, 银铜钛合金, 原子扩散

Abstract: 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.

Key words: Cubic boron nitride grain, Microstructure delamination, Silver-copper-titanium alloy, Thermodynamic analysis