Corrosion of laser joined silicon carbide in gasification environment

Abstract

The production of synthesis gas from renewable fuels is an emerging technology. The aggressive process environment in fuel production systems poses a major challenge, potentially causing corrosion within currently used metallic heat exchangers. To improve the reliability and stability of silicon carbide heat pipes, which belong to an innovative heat exchanger design, the corrosion of involved materials due to contact with steam, ash and alkaline (earth) metals needs to be investigated. Exposures of laser joined SSiC connections with wood ash caused the formation of gas inclusions and an infiltration of the joint with alkaline (earth) metals that lead to crack formations, as revealed by energy dispersive X-ray spectroscopy analysis. It was shown that the use of silicon carbide heat pipes joined with solder materials of both the Mg-Al-Si and the Y-Al-Si systems is possible. A further result was that the gasification temperature has to be limited to ,8508C.

Recent advances in joining of SiC-based materials (monolithic SiC and SiCf/SiC composites): Joining processes, joint strength, and interfacial behavior

“…By comparison with the CVD-SiC joint strengths using CA as interlayer, the SLO shear strength was only ~40 MPa, while the average THG shear strength arrived at ~100 MPa [12,[91][92][93]. Moreover, the 4PB strengths of SiC and SiC f /SiC joint fluctuated in the range of 94.5-236 MP while using YAS as interlayer except a minimum shear strength [18,[94][95][96][97][98][99].…”

Pressureless joining of SiC ceramics with magnesia‐alumina‐silica glass ceramics

“…The intricate shaped SiC hardware is fabricated by joining simple shaped parts. Thus, there is continued research thrust to develop economical joining techniques fulfilling the structural and functional requirements of the target applications 12–45 …”

“…The application of metallic filler joining is limited to low‐temperature structural applications due to its poor high‐temperature strength and oxidation resistance and poor irradiation tolerance 14,21,22 . The nonmetallic filler joining technique includes polymer‐derived ceramic joining, 23,24 transient eutectic‐phase joining using SiC‐based mixed oxide additives, 14,25,26 and glass‐ceramic joining 27–44 . In general, the polymer‐derived ceramic joints processed at 1200−1400°C have poor irradiation tolerance attributed to the intrinsic irradiation instability of amorphous structures with excess carbon and oxygen formed during the pyrolysis 14,23,24 .…”

“…In comparison to the technique discussed above, glass‐ceramic joining is an inexpensive and simple technology that can be readily used in industries for joining large and complex SiC hardware for nuclear and structural applications. The glass‐ceramic joints are processed at intermediate temperatures (1050−1600°C) without an applied pressure and exhibit high joint strengths, appreciable irradiation tolerance for certain compositions, tunable thermal and mechanical properties, high‐temperature strength retention (<1000°C), high oxidation resistance, and self‐healing above glass softening point 27–44 . The glass‐ceramic joining is made by preparing an oxide glass by melt quench technique, which is subsequently powdered and applied as a slurry on SiC substrates.…”

“…To date, the researchers have investigated the effects of filler composition, surface treatment, and annealing on the joint strength of SiC ceramics joined using glass‐ceramic fillers 27–44 . To our knowledge, there is no systematic report on the effects of joining temperature and composition in the MgO‐Al 2 O 3 ‐SiO 2 (MAS) glass‐ceramic system.…”