Development of Au-Pd-Co-Ni-V Brazing Alloy for Joining Si3N4 to Si3N4

Abstract

Brazing technique, as one of the reliable joining techniques, has been investigated by a great number of research work for ceramic joining, and, since 90’s in the last century, development of new high-temperature brazes for the joining of ceramic to ceramic and ceramic to metal had become a research focus. In the present paper, one Au-Pd-Co-Ni-V alloy was newly designed for Si₃N₄ joining. It was fabricated into brazing foils with a thickness of about 0.15 mm through several cycles of rolling at room temperature and heat treatment. Joining of Si₃N₄ to Si₃N₄ was carried out in the brazing temperature range from 1423 K to 1483 K. A SEM equipped with an XEDS was used for microstructural analysis of the Si₃N₄/Si₃N₄ joints. Furthermore, the interfacial reaction products were determined by XRD method. The Si₃N₄/Si₃N₄ joints brazed at 1443 K for 10 min using the newly developed filler metal exhibits a three-point bend strength of 320.7 MPa at room temperature, and the strength values are 220.8 MPa, 216.9 MPa and 102.9 MPa at 973 K, 1073 K and 1173 K respectively. The corresponding interfacial reaction products were identified as VN and Pd₂Si. The mechanism of the interfacial reactions was discussed.

Key words: Si₃N₄; brazing; interfacial reaction; joint strength