Brazing of CoCrFeNi and CoCrFeMnNi equiatomic alloys using 70Au-8Pd-22Ni filler foil

Abstract

Brazing of CoCrFeNi and CoCrFeMnNi equiatomic alloys using 70Au-8Pd-22Ni (AuPdNi) filler foil by infrared and traditional furnaces was investigated. The wettability of AuPdNi filler on both CoCrFeNi and CoCrFeMnNi substrates is excellent at 1050 °C. CoCrFeNi/AuPdNi/CoCrFeNi joints brazed using infrared and traditional furnaces are composed of Au/Ni-rich solid solutions of different sizes. CoCrFeMnNi/AuPdNi/CoCrFeMnNi joints brazed with an infrared furnace are composed of large globular CoCrFeNi/Ni-rich particles in AuMn intermetallic matrix. In traditional furnace brazed CoCrFeMnNi/AuPdNi/CoCrFeMnNi joints, the AuMn intermetallic compound is uniformly distributed in CoCrFeNi-based and Ni-rich phases. The average shear strengths of both infrared and traditional furnace brazed CoCrFeNi/AuPdNi/CoCrFeNi joints exceed 300 MPa, and all joints fractured at the brazed zone present dimple dominated fracture. In contrast, the traditional furnace brazed CoCrFeMnNi/AuPdNi/CoCrFeMnNi joint has a much lower average shear strength of 173 MPa because of the existence of many solidification shrinkage voids in the brazed zone.