Formation of a tritium-resistant surface of stainless steel by chromium diffusion coating

An attempt has been made to depress the tritium sorbability (ad- and ab-sorbability) of the surface of stainless steel by a method of chromium diffusion coating. The chromium layer was generated on a stainless steel surface from mixed powders of metallic Cr, NH4C1 and A12O3 in ar Ar atmosphere. The surface layer formed under an optimum condition, to provide an effective surface in suppressing the sorption of tritium, was determined to be roughly 1.5 μm in thickness. The surface layer was constituted of an outer layer of deposited chomium that was covered with very thin passive film and a inner diffusion layer which was formed by a mutual diffusion of the deposited chromium and the constituents of stainless steel. These results led to the conclusions that the diffusion coating of the surface with chromium brought the chemical stability and probably the higher density of surface layer, and that the resulting thin stable double layer was realized as a durable and tritium-resistant surface of stainless steel. (orig.)