Comparative study on the joining performance of TiH_2 and ZrH_2 modified AgCu_(28) brazing alloys with pulsed laser welding-brazing

摘要

Brazed alloys between cubic boron nitride (cBN) grits and matrix extremely affect the service life of the grinding wheel. The aim of this study was to investigate the addition of elemental Zr to improve the connection effect of alloys. The plates of pure titanium (Ti) Gr. 1 and AISI 1045 steel had been applied to conduct the welding-brazing experiments with active brazing alloys of AgCu28-4.5Ti and AgCu28-4.5Ti-4Zr. Brazing alloys was heated with an Nd:YAG pulsed laser welding-brazing system under inert argon gas atmosphere. Transition zones between the brazed alloys and matrices were investigated with scanning electron microscope (SEM), energy dispersion spectrometer (EDS), and X-ray diffraction (XRD) analyses. In addition, hardness of the brazed layer was analyzed as well as tribology. The results showed that the active element, zirconium (Zr), significantly accelerated the bidirectional diffusion and improved the gradient evolution of the main elements in the transition zones. Compared to Zr-free brazing alloys, the active element, Zr, inhibited the overproduction of the hard-brittle phase of Cu3Ti and formed other intermetallic compounds, such as AgZr2 and Cu10Zr7, which were beneficial to the metallurgical joint. A brazed layer with a lower friction coefficient, a more uniform hardness distribution, and better ductility was obtained, though the wear resistance slightly decreased. A solid solution product of Zr-Cu was formed during laser welding-brazing process, which strengthens the brazed layer and improves its overall performance.