LAUSR

Abstract The study was to investigate the modifying effect of the active element Zr on the properties of mechanical alloyed (MA) AgCu28–4.5Ti brazing alloys, especially the joint performance of cubic boron nitride (cBN)/45 steel brazed with AgCu28–4.5Ti–4Zr active brazing alloy. The brazing process was carried out using an Nd:YAG pulsed laser device under a high purity argon atmosphere. The granularity distribution and composition analysis of the MA brazing alloys, microstructural examinations and phase analysis were performed using a laser granularity analyzer, scanning electron microscopy (SEM) equipped with energy dispersion spectrometry (EDS), and X–ray diffraction (XRD) techniques. The results indicate that the alloy particles are refined, sizes are uniform, and the formation of the hard-brittle phase is reduced owing to the addition of the active element Zr. The wettability of the brazing alloy containing Zr is enhanced. The reaction of the active element Zr with Ag or Cu inhibits the combination of Ti with Ag or Cu under rapid laser heating and cooling, and further promotes the generation of Ti B and Ti N compounds. The joining mechanism is derived from the formation of a continuous reaction layer between cBN and the brazed alloy, containing a sub-outer structure of TiB, TiB2, TiN, ZrB2, and an outer structure consisting of AgZr2, Cu10Zr7. This multi-layered structure, which is from cBN to 45 steel, realizes the metallurgy combination of the brazing alloy and cBN particles. The friction and wear tests indicate that the reliable connection of cBN to steel is realized.