Formation of Cr2O3 layers on coolant duct materials for suppression of hydrogen permeation

Oxidation control of candidate duct materials for liquid cooled blanket systems (i.e. SS316, SS316L, Inconel 600 and Hastelloy X) was studied to form a single composition Cr2O3 layer on the surfaces for (i) making a stable and robust underlayer for ceramic coating fabrication by the metal organic decomposition (MOD) method and (ii) suppression of hydrogen permeation by the Cr2O3 layer itself. In heat treatments of the bare plates at 700 degrees C in air of atmospheric pressure and air of reduced pressure of 5 Pa, oxidized Fe and/or Ni diffused to the outermost surfaces of the oxide layers and a single composition layer of Cr2O3 could not obtained on the surfaces. However, the Cr2O3 surface layers could be formed by a heat treatment of chrome plated plates at 700 degrees C in air of atmospheric pressure. MOD coatings were successfully fabricated on the stable Cr2O3 surface layers. The preliminary evaluation of deuterium permeation through the Cr2O3 covered plates showed that the permeation reduction factors (PRFs) of the Cr2O3 layers would be 1-2 orders. (C) 2017 Elsevier B.V. All rights reserved.