Characterization of ceramic plasma-sprayed coatings, and interaction studies between U-Zr fuel and ceramic coated interface at an elevated temperature

Candidate coating materials for re-usable metallic nuclear fuel crucibles, HfN, TiC, ZrC, and Y₂O₃, were plasma-sprayed onto niobium substrates. The coating microstructure and the thermal cycling behavior were characterized, and U-Zr melt interaction studies carried out. The Y ₂O₃ coating layer had a uniform thickness and was well consolidated with a few small pores scattered throughout. While the HfN coating was not well consolidated with a considerable amount of porosity, but showed somewhat uniform thickness. Thermal cycling tests on the HfN, TiC, ZrC, and Y₂O₃ coatings showed good cycling characteristics with no interconnected cracks forming even after 20 cycles. Interaction studies done on the coated samples by dipping into a U-20wt.%Zr melt indicated that HfN and Y₂O₃ did not form significant reaction layers between the melt and the coating while the TiC and the ZrC coatings were significantly degraded. Y₂O₃ exhibited the most promising performance among HfN, TiC, ZrC, and Y₂O₃ coatings.