Pressureless joining of SiC ceramics with magnesia‐alumina‐silica glass ceramics

Abstract

Liquid phase sintered SiC ceramics were joined using magnesia‐alumina‐silica (MAS) glass‐ceramic fillers without applied pressure. Four different filler compositions with 9.3–25.2 wt.% MgO, 20.7–33.6 wt.% Al2O3, and 49.2–68.1 wt.% SiO2 were studied. The effects of filler composition and joining temperature (1450–1600°C) on the joint strength were investigated. All compositions exhibited an optimum joining temperature at which the maximum joint strength was obtained. A low joining temperature resulted in poor wetting of the SiC substrate due to the high viscosity of the filler. Whereas a high joining temperature caused dewetting and large unfilled sections in the interlayer due to the deleterious interfacial reactions. The joint strength was inversely proportional to the interlayer thickness, which was a function of filler composition and joining temperature. The SiC ceramic joined at 1525°C with MgO‐25 wt.% Al2O3‐60 wt.% SiO2 filler exhibited a four‐point bending strength of 286 ± 40 MPa.