Brazing ZrO₂ ceramic and TC4 alloy using Ag-Cu+WC composite filler

Novel Ag-Cu+WC composite filler was developed to braze ZrO₂ ceramic and TC4 alloy. The interfacial microstructure and formation mechanism of the joints were investigated. The effect of brazing temperature on the microstructure and mechanical properties of the joints was analyzed. It is found that the typical microstructure of the joints was ZrO₂ ceramic/TiO+Cu₃Ti₃O/TiCu+TiC+W+Ag_(s,s)+Cu_(s,s)/TiCu₂/TiCu/Ti₂Cu/TC4 alloy. During brazing, the in-situ formed TiC and W reinforced phases through reacting between WC particles and active Ti served as nucleation site for Ti-Cu intermetallic compounds, Ag-based solid solution and Cu-based solid solution and suppressed the growth of brittle Ti-Cu intermetallic compounds adjacent to TC4 alloys. Hence, the microstructure of the joints was optimized and the mechanical properties were improved. As the brazing temperature increased, the thickness of reaction layers in the joints gradually increased, and the reaction between WC particles and active Ti enhanced. The maximum shear strength of joints achieved 82.1 MPa when brazing at 890 °C for 10 min, which increased by about 57.3% than that of the joints without WC addition.