Effect of brazing temperature on microstructure and mechanical properties of GH4169/AgCuTi+W/Si3N4 joint

Abstract

Nickel-based superalloy (GH4169) and Si3N4 ceramics were connected by AgCuTi composite active filler and high purity W foil which acts as interlayer. The effects of temperature on the microstructure evolution and mechanical properties of GH4169/ Si3N4 brazed joint were systematically studied. The results show that the effective connection of GH4169/Si3N4 brazed joint can be realized by using AgCuTi+W composite filler. The microstructure of the joint is GH4169/TiNi3+TiCu+TiCu2+Ag(s, s)+Cu(s, s)+W+TiN+Ti5Si3/Si3N4. When the brazing temperature is low, the Ti element in liquid filler diffuses to less of the ceramic interface with the filler, and no obvious reaction layer is formed； when the brazed temperature increases to 880 ℃, Ti is enriched on the ceramic side, forming a thickness of 2 μm TiN and Ti5Si3 reaction layer. At this time, the shear strength of the joint is the highest, reaching 190.9 MPa. With the increase in brazing temperature, the content of Ti-Cu compound，which is a brittle compound, increases and the mechanical properties of the joint are greatly reduced. The fracture results show that during the shear process, the crack initiates in the interlayer, and then diffuses into the Si3N4 ceramic matrix， and finally breaks on the side of Si3N4 ceramic.

Keywords

• nickel-base superalloy
• si3n4 ceramics
• brazing
• microstructure
• mechanical property