Low-Temperature MOCVD Deposition of Vanadium Carbide on F/M Steel for Mitigating Fuel-Cladding Chemical Interaction

Fuel-cladding chemical interaction is recognized as a significant challenge in metallic fuel/steel cladding systems due to the formation of low-melting-point intermetallic eutectic compounds between fuel and steel cladding constituents. To address this, the study explores diffusion barrier coatings applied via metal-organic chemical vapor deposition, chosen for its low processing temperature under 600°C, thus preventing thermal degradation of steel cladding. In this study, we successfully developed thin, dense coatings ranging from a few to several micrometers in thickness. These coatings are composed predominantly of a mixture of V₂C and vanadium carbide (VC) phases. Following the coating process, the T91 ferritic/martensitic (F/M) steel substrates remained intact with no noticeable decarburization or reduction in microhardness near the VC coating. Further testing through diffusion couple experiments at 550°C for 100 h revealed that an 8-µm-thick VC coating layer can effectively prevent interdiffusion between cerium and T91 F/M steel. Leveraging optimized processing conditions on flat coupon samples, this deposition was also applied to an archived EBR-II HT-9 steel cladding. These results demonstrate promising applications for sodium-cooled fast reactors (SFRs).