Two-step joining of reaction bonded silicon carbide (RBSC) using borosilicate glass

Abstract

The borosilicate glass was used to join reaction bonded silicon carbide through two steps, namely: laser cladding and low-temperature heat treatment. The wettability and microstructure of the laser cladding glass layer were examined, while joint microstructure and strength were analyzed at various temperatures and times. The results show that the laser cladding layer improved the wetting of glass on the substrate, formed a good interfacial bond, and reduced the joining temperature. The joints primarily consist of the glass phase, the boron-rich phase, and a few crystals. The high-strength joints obtained after heating the joint interface at 950 °C for 30 min had a flexural strength of 250 ± 20 MPa, a 68% improvement compared with direct connection under the same conditions. The joints also exhibit good thermal shock resistance and high-temperature strength. At 400 °C (thermal shock temperature) and 600 °C (test temperature), the residual flexural strengths were 122 ± 25 and 152 ± 12 MPa, respectively.