Wetting and joining of surface-oxidized SiC ceramic with calcium lithium aluminosilicate glass filler

Abstract

A novel strategy was developed to join SiC ceramics via a two-step method (i.e., SiC surface was modified by pre-oxidation treatment before bonding) using CaO-Li2O-Al2O3-SiO2 (CLAS) glass as the joining material. The wetting behavior, joint microstructure, bonding strength, fracture characteristics, and joining mechanism were investigated. Due to the formation of the SiO2 layer on the SiC surface by the pre-oxidation, the wettability of CLAS glass solder on the SiC matrix was significantly improved and the interfacial bonding was also enhanced. The microstructure of the joint revealed that the nanoscale eutectic structure composed of wollastonite and spodumene and the rod-shaped anorthite with micron-size were the main products in the joint seam. Besides, the content and size of anorthite in the joints increased with the increase of the joining temperature. Compared with one-step joining, the two-step method can obtain more reliable SiC/SiC joints due to the strong interfacial bonding. As a result, the optimal shear strength of 127 MPa was achieved at a joining temperature of 1240 °C, which was 119% higher than that obtained by the one-step joining method.