Effect of Ti content on microstructure and strength of Si3N4/Si3N4 joints brazed with Cu–Pd–Ti filler metals

A novel Cu–Pd–Ti filler alloy was adopted to braze silicon nitride ceramic to itself in the form of Cu/(Ti, Pd)/Cu. The reliable Si3N4 joints were obtained. The effect of Ti content on the microstructure and properties of the Si3N4 joints was investigated using EPMA, SEM and three-point bending method. Results indicate that Ti content in the filler has a great impact upon the microstructure of the joints via exerting an influence on the diffusion and spread of liquid filler alloy on the ceramic surface, and subsequently on the formation of reaction layer. When the Ti content is 15 at.%, both the thickness of reaction layer and the bonding strength reach the maximum value of 8 μm and 155.8 MPa, respectively. Reaction phases (Ti5Si3, Pd2Si and PdTiSi) appear in the joint, moreover, the Cu[Pd] solid solution distribute more homogeneously. All the joints failed along one of the two ceramic/interlayer interfaces.