Interfacial Reactions in the Joining of Si3N4/Si3N4 with Newly Developed CuNiTiB Brazing Alloy

Abstract

Joing of Si3N4/Si3N4 was carried out with a newly developed Cu68Ni10Ti21B1 brazing alloy. With the powdered new brazing alloy, the shear strength of the joints reaches 233 MPa. With the rapidly-solidified foils of the brazing alloy, the three-point bend strength of the joints is raised to 406 MPa at room temperature and this value is kept until 723K. The interfacial reactions of the joint and its effects on the joint strength are discussed. The lattice matching between Si3N4 and Ti5Si3 is better than that between Si3N4 and TiN. So the formation of Ti5Si3 rather than TiN at the interfaces is favorable to the joint strength. Adding element Ni to Cu-Ti alloy can weaken the activity of Ti in the alloy, which is favorable to decrease the thickness of interfacial reaction layer and in the result the joint strength is increased. An adding a small amount of B in the new alloy can decrease its liquidus temperature.