Initial characterization of V―4Cr―4Ti and MHD coatings exposed to flowing Li

Abstract A mono-metallic V–4Cr–4Ti thermal convection loop was operated in vacuum (∼10 −5  Pa) at a maximum Li temperature of 700 °C for 2355 h and Li flow rate of 2–3 cm/s. Two-layer, physical vapor deposited Y 2 O 3 –vanadium, electrically insulating coatings on V–4Cr–4Ti substrates as well as tensile and sheet specimens were located in the flow path in the hot and cold legs. After exposure, specimens at the top of the hot leg showed a maximum mass loss equivalent to ∼1.3 μm of metal loss. Elsewhere, small mass gains were observed on the majority of specimens resulting in an increase in hardness and room temperature yield stress and a decrease in ductility consistent with the observed uptake of N and C from the Li. Specimens that lost mass showed a decrease in yield stress and hardness. Profilometry showed no significant thickness loss from the coatings.