Microstructure evolution of Si3N4/Si3N4 joint brazed with Ag–Cu–Ti + SiCp composite filler

The Si3N4 ceramic was brazed by Ag–Cu–Ti + SiCp composite filler (p = particle) prepared by mechanical mixing. Effects of the content of Ti and SiC particles on microstructure of the joint were investigated. A reliable Si3N4/Si3N4 joint was achieved by using Ag–Cu–Ti + SiCp composite filler at 1173 K for 10 min. A continuous and compact reaction layer, with a suitable thickness, forms at the Si3N4/braze interface. The SiC particles react with Ti in the brazing layers, forming Ti3SiC2 thin layers around the SiC particles themselves and Ti5Si3 small particles in the Ag[Cu] and Cu[Ag] based solid solution. The higher content of SiC particles in the filler (≥10 vol%) depresses interfacial bonding strength between the Si3N4 substrate and composite brazing layer due to the thinner reaction layer and the bad fluidity of the filler. The Ti3SiC2 → TiC + Ti5Si3 reaction occurs when Ti concentration around SiC particles in the filler increases.