Ceramic coatings for metallic components in supercritical water-cooled reactors

Zr-2.5Nb, a Zirconium alloy, cannot be used itself as a material of construction for SCWR applications, although it is desirable, from a neutron economy standpoint to use zirconium alloys for in-core materials. Thus, improving the oxidation resistance of zirconium through corrosion-resistant coatings is of interest for the SCWR. Plasma Electrolytic Oxidation (PEO) deposition was used to fabricate oxide coatings on Zr-2.5%Nb substrates from a sodium aluminate solution, which yielded an Al_(0.18)Zr₍₀.₈₂₎O_(1.91) coating. Spray Pyrolysis Deposition (SPD) was also used to fabricate Cr₂O₃ films on Zircaloy substrates. The samples were tested under supercritical water conditions (500^oC, 25 MPa, deaerated) at exposure times of 100 and 250 hours. A reduction in corrosion rates of up to 50% at 100 hours of exposure, and up to 28% at 250 hours of exposure was noted. Both samples show improved corrosion resistance compared to the uncoated substrate. (author)