The Microstructure and Shear Strength of SiC Joints Brazed with SiC Particle Reinforced Si-24Ti Alloy

Abstract

To refine the microstructure and increase the joint strength of SiC ceramic brazed with Si-24Ti (wt.%), carbon nanotubes (CNT) were added into Si-24Ti brazing alloy to form SiC particles in the braze zone. The effect of the amount of CNT in the brazing alloy on the microstructure and shear strength of joints was investigated. The microstructure and element distribution of the joint was studied by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS). The results indicated that the addition of the proper amount (1-3 wt.%) of CNT could refine the microstructure of joints and achieve high-quality SiC joints. The shear strength of the joint brazed with 3 wt.% CNT addition reached the maximum value of 108 MPa, which was 21.3% higher than that of without CNT (89 MPa). However, when the amount of CNT increased to 5 wt.%, the shear strength of joint decreased to 55 MPa, due to the formation of cavity in the joint. The strengthening mechanism of in-situ formed SiC particle in the composite brazing alloy was evaluated.