Microstructure and mechanical properties of Si3N4/Si3N4 joint brazed with Ag–Cu–Ti + SiCp composite filler

Ag–Cu–Ti + SiCp composite filler was used as brazing material to join Si3N4 ceramic. Effects of the content of Ti (4–10 wt.%) and SiC particles (0–15 vol.%) on properties and microstructure of the joints were investigated. A reliable Si3N4/Si3N4 joint was achieved by using Ag–Cu–Ti + SiCp composite filler brazed at 1173 K for 10 min. A continuous and compact reaction layer with suitable thickness was formed at the Si3N4/braze interface. The SiC particles reacted with Ti in the brazing layers, forming Ti3SiC2 thin layers around the SiC particles and Ti–Si phases. However, when the Si3N4/Si3N4 joints were brazed by the filler with the aptotic content of Ti, higher content of SiC particles (≥10 vol.%) in the filler decreased interfacial bonding strength due to bad fluidity of the filler and insufficient reaction between the Ti element and the Si3N4 substrates. The Ti3SiC2 → TiC + Ti–Si reaction occurred when Ti concentration was higher around SiC particles in the filler. The highest average three-point bending strength of 506.3 MPa was retained when x was 8 wt.% for Si3N4/Si3N4 joints brazed with (Ag72Cu28)100−xTix + 5 vol.% SiCp composite filler.