Influence of Zn evaporation on wetting of Ag-Cu-Zn brazing alloy on TiC-Ni cermet

Wetting of Ag-Cu-Zn brazing alloy on TiC-Ni cermet was performed. The results show that continuous (Cu, Ni) layer forms at the interface of Ag-Cu-Zn/TiC-Ni cermet at 810 ℃for 10 min with a heating rate of 22.5 ℃/min in vacuum. The whole wetting process contains an incubation stage, a spreading stage, a pinning stage, a receding stage, and an equilibrium stage. The equilibrium contact angel is 27.3°. With the increase of heating rate from 10 ℃/min to 30 ℃/min, the evaporation velocity of Zn strengthens; the lasting time of the spreading process shortens, and the amount of (Cu, Ni) at the interface decreases. As a result, the equilibrium contact angel of Ag-Cu-Zn on TiC-Ni cermet increases with the heating rate. The evaporation of Zn weakens in argon. Only a little (Cu, Ni) forms at the interface of Ag-Cu-Zn/TiC-Ni cermet in argon, although the Ag-Cu-Zn brazing alloy dissolves a great amount of Ni matrix. So the base diameter firstly increases and the contact angle decreases with time, then the base diameter almost remains unchanged, and the contact angle increases slightly.