Abstract
In this work, (Au79Ni17Pd4)96Ti4 (wt.%) filler alloy was designed and employed to join SiC ceramics. The effects of brazing temperature and soaking time on the microstructure and fracture morphology of joints were investigated. The results show that the joint obtained can be described as SiC/reaction layer/braze/reaction layer/SiC. The reaction layer was composed of TiC and Au (Si, Ti). The wettability of the filler alloy toward the SiC ceramics was analyzed. The braze zone was mainly constituted by Pd2Si, Ni2Si, and Au (Ni, Si). A large number of nano-sized TiC particles were distributed within the Au (Ni, Si) layer. The formation mechanism of the braze containing different phases was discussed. The brazing temperature and soaking time had a significant effect on the reaction layer at the SiC/braze interface and TiC particles within the Au (Ni, Si) layer, while they showed a negligible effect on the Pd2Si and Ni2Si within the braze. The inherent reason was also clarified in detail. The joint fractography indicated that a good bonding was achieved between the filler alloy and SiC, while joint fracture was primarily induced by the thermal stresses residing after the brazing cycle.
Highlights
Developing advanced energies to reduce the consumption of traditional fossil fuels is becoming necessary over the world
The SiC ceramics used had a purity of 97 wt.% and contained no free Si
The filler alloy was composed of Au, Ni, Pd, and Ti foils, which were purchased from Alfa Aesar
Summary
Developing advanced energies to reduce the consumption of traditional fossil fuels is becoming necessary over the world. Zirconium alloys are widely adopted as nuclear-fuel cladding materials in commercial light-water reactors (LWR) [2,3]. The current work focuses on developing a new high-temperature filler alloy for the joining of SiC ceramics. A new high-temperature filler alloy containing Au, Ni, Pd, and Ti was designed to achieve the high-quality bonding of SiC ceramics. Based on the above analysis, the filler alloy with the composition of (Au79 Ni17 Pd4 ) Ti4 (wt.%) was designed to join the SiC ceramics It can be found from Au–Ni–Pd ternary phase diagram [17] that the melting point of Au79 Ni17 Pd4 (wt.%) is approximately 1423 K. The effects of brazing temperature and holding time on microstructure and fracture morphology of the joints were studied
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