Vacuum brazing of TZM alloy to ZrC particle reinforced W composite using Ti-28Ni eutectic brazing alloy

Abstract

Reliable brazing of TZM alloy and ZrC particle reinforced (ZrCp) W composite was achieved in this study by using Ti-28Ni eutectic brazing alloy. The typical interfacial microstructure of TZM/Ti-28Ni/ZrCp-W brazed joint consisted of a Ti solid solution (Ti(s, s)) layer, a continuous Ti2Ni layer and a diffusion layer mainly composed of W particles and (Ti, Zr)C particles. With an increase of brazing temperature, more ZrC particles and W particles entered the molten brazing alloy, which broadened the brazing seam and diminished the Ti2Ni layer, resulting in the disappearance of the Ti2Ni layer eventually. Meanwhile, more Ti(s, s) stripes were observed on the TZM side. The presence of continuous Ti2Ni intermetallic phase and Ti(s, s) stripes structure in joints deteriorated the joining properties, which resulted in the formation of brittle fracture under shear test. In addition, the fracture path was related to the brazing temperature, and cracks initiate and propagate in the continuous Ti2Ni layer at lower temperatures. However, the fracture path tended to be located at the TZM substrate close to the interface between TZM and the brazing seam when the brazing temperature exceeded 1040°C. The optimal room temperature shear strength reached 120.5MPa when brazed at 1040°C for 10 min and the fracture surface exhibited cleavage fracture characteristics, and the shear strength at high temperature of 800°C for the specimens with highest shear strength at room temperature reached 77.5MPa.