Ceramic Coatings for Metallic Components in Supercritical Water-cooled Reactors

Abstract

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.