The Effect of MOD Process Parameters on Performance of Er₂O₃ Coating for Liquid Blanket Application

Previous studies by the authors showed that hydrogen permeation reduction factor (PRF) of Er₂O₃ coating on ferritic steels by Metal Organic Decomposition (MOD) depends on the Cr level of the substrate steels and the annealing conditions. The reason of the dependence was attributed to the composition of the oxide layer formed beneath the coating. The PRF was shown to be larger when Cr₂O₃ layer was formed than when Fe₂O₃ layer was formed. This paper reports further investigation of the effect of temperature and oxygen partial pressure of the annealing on the composition of the oxide layer. A diffusion modeling of Cr and O was performed to account for the experimental data. The results showed that the data can be well explained assuming that Cr₂O₃ layer is formed when supply of Cr exceeds that of O at the substrate surface.