| Abstract Scope |
In the concentrating solar power industry, there is an increasing demand for ceramic-based components connected to metal heat transfer networks for increased efficiency and reduced risks. One of the main technical barriers to achieving such synergy lies in reliably joining ceramic to metal with acceptable mechanical, thermal and chemical stabilities. In this study, multi-principal element alloys (MPEAs) are being designed and evaluated for joining SiC to Ni-base superalloy IN740H. The core benefits of MPEAs are the vast design space, phase stability within a wide composition range and excellent mechanical properties, facilitating ceramic-to-metal joining for structural applications. To join SiC and IN740H, vacuum furnace brazing and diffusion bonding methods were evaluated as candidate joining techniques. Diffusion bonding was performed under vacuum at elevated temperature and pressure using a graphite hot press. Light optical microscopy (LOM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were employed to characterize the joint quality and interface microstructures. Additionally, microhardness mapping and shear testing were conducted to reveal the correlation between the interface reactions and dissimilar joint strengths. It was found that brazing generally yielded more severe reactions and greater diffusion at the dissimilar joint interface, forming pores and thick layers of brittle phases. In comparison, the impact of diffusion bonding parameters on the formation of brittle phases at the ceramic-to-metal interface were studied and demonstrated thinner reaction layers than vacuum furnace brazes and leading to stronger bonds. Keywords: Multi-principal element alloys, high entropy alloys, ceramic-to-metal joining, diffusion bonding, brazing. |