Performance comparison of Al-Si-Ti and Co-Si-V-Ti braze alloys in the vacuum brazing of reaction-bonded silicon carbide

Abstract

AlSiTi and CoSiVTi braze alloys were used in the active metal brazing of reaction-bonded silicon carbide (RB-SiC). The brazing tests were conducted in vacuum furnace under different isothermal holding temperatures (1200 to 1300 °C). The wetting behavior, interfacial microstructure, elemental diffusion, and morphology of fractured joint surface after mechanical testing were investigated using scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Both braze alloys demonstrated good wettability and spreadability on RB-SiC under tested conditions. During brazing, elements from the braze alloys diffused through the base substrate (BS) and reacted with RB-SiC to form silicides, leading to the formation of a diffusion-affected zone (DAZ). Shear strength of joints produced by the above two braze alloys under different brazing conditions were also measured, and the results showed a maximum shear strength of 95 MPa and 43 MPa for braze joints produced by AlSiTi braze alloy and CoSiVTi braze alloy, respectively.