Interfacial and Cross-sectional Studies of Thermally Cycled Alumina-Monel Brazed Joint

Abstract

Alumina and monel superalloy was successfully joined by active metal brazing technique using Ticusil (68.8Ag-26.7Cu-4.5Ti in wt%) filler alloy in a vacuum furnace at 910°C for 10 min under a vacuum of 5×10^–6 Torr. Phase analysis of the monel-filler alloy and alumina-filler alloy interfaces was conducted by X-ray diffraction analysis. Interfacial and cross-sectional microstructural investigation and determination of elemental composition were performed by scanning electron microscopy and energy dispersive X-ray analysis. No crack was found at the joint interfaces after thermal cycling test for 100 cycles between 50° and 600°C. Microhardness was estimated by Vickers hardness tester at the cross-section of the joint after thermal cycling test. Typical brazing strength of the thermally cycled joint was above 23 MPa. Helium leak tests indicated good hermiticity of the thermally cycled brazed joints.

GRAPHICAL ABSTRACT

Keywords:

• Al₂O₃-monel joint
• Thermal cycling test
• Microstructural study
• Microhardness
• Brazing strength
• Helium leak test