Microstructural evolution and mechanical properties of B₄C-TiB₂/GH99 joint brazed with AgCuTi filler

Due to the unique advantages arising from the inherent characteristics of B₄C-TiB₂ ceramic and GH99 alloy, the joining of B₄C-TiB₂ ceramic to GH99 alloy holds significant importance in various fields. In this work, B₄C-TiB₂ ceramic and GH99 alloy was joined by vacuum brazing with AgCuTi filler. The effect of brazing temperature on microstructures and mechanical properties of brazed joints was studied; the microstructures of the ceramic interface were detailly characterized using TEM; and the formation of brazing interface was discussed. The typical microstructure consisted of B₄C-TiB₂ ceramic substrate/ TiB+Cr₃C₂+nano-TiC/ Ag(s,s)+ Cu(s,s)/ TiAl(Ni,Cu)₂+ Ti(Ni_xCu_1-x)₂+ TiCr(Ni,Cu)₂/ dissolution zone of Ag(s,s)/ GH99 substrate. With increasing brazing temperature, both the reaction region and dissolution zone adjacent to GH99 alloy expanded significantly. Concurrently, the reaction layers of Ti(Ni_xCu_1-x)₂ and TiCr(Ni,Cu)₂ exhibited progressive thickening. At higher temperatures, coarse TiAl(Ni,Cu)₂ intermetallic compounds began to form. Furthermore, the reaction layer next to the B₄C-TiB₂ ceramic demonstrated incremental growth with temperature. As the brazing temperature increases, the joint strength exhibits a trend of first increasing and then decreasing. Under the optimal condition of 890 ℃ for 10 min holding time, the maximum average shear strength reaches 87.1 MPa.