Low-temperature joining of SiC ceramics with Y2O3-Al2O3 interlayer by SiO2-based liquid phase extrusion strategy

Abstract

In order to reduce the joining temperature of SiC ceramics by glass-ceramic joining, some oxides were usually introduced into to Y2O3–Al2O3 for reducing the eutectic temperature. However, the joints might have poor high-temperature resistance due to the low melting point of the joining layer. In the present work, based on novel SiO2-based liquid phase extrusion strategy, joining of SiC ceramics with Y2O3–Al2O3 interlayer was carried out by using Y2O3–Al2O3–SiO2 as the filler through spark plasma sintering (SPS). The SiO2-free interlayer of Y2O3–Al2O3 was used for comparison. It was found that SiC joints using Y2O3–Al2O3 could be only joined at a high temperature of 1800 °C, and the thickness of the interlayer was about 20 μm. The shear strength of the joint obtained at 1800 °C was 89.62 ± 4.67 MPa and the failure located in the SiC matrix. By contrast, reliable joining of SiC ceramics could be finished at as low as 1550 °C by extrusion of SiO2-containing liquid phase when using Y2O3–Al2O3–SiO2 as the interlayer, alongside the interlayer thickness of only several microns. The joint strengths after joining at 1550 °C was 84.90 ± 3.48 MPa and the failure located in matrix position. The joining mechanism was discussed by combining the detailed microstructure analysis and phase diagram.