INTERACTION STUDIES OF CERAMIC VACUUM PLASMA SPRAYING FOR THE MELTING CRUCIBLE MATERIALS

Abstract

Candidate coating materials for re-usable metallic nuclear fuel crucibles, TaC, TiC, ZrC, ZrO₂, and Y₂O₃, were plasmasprayed onto a niobium substrate. The microstructure of the plasma-sprayed coatings and thermal cycling behavior were characterized, and U-Zr melt interaction studies were carried out. The TaC and Y₂O₃ coating layers had a uniform thickness, and high density with only a few small closed pores showing good consolidation, while the ZrC, TiC, and ZrO₂ coatings were not well consolidated with a considerable amount of porosity. Thermal cycling tests showed that the adhesion of the TiC, ZrC, and ZrO₂ coating layers with niobium was relatively weak compared to the TaC and Y₂O₃ coatings. The TaC and Y2O₃ coatings had better cycling characteristics with no interconnected cracks. In the interaction studies, ZrC and ZrO₂ coated rods showed significant degradations after exposure to U-10 wt.% Zr melt at 1600℃ for 15 min., but TaC, TiC, and Y₂O₃ coatings showed good compatibility with U-Zr melt.