High-temperature oxidation and nitridation behavior of PEO-coated ZIRLO alloy in nitrogen-containing environments at 900 and 1000° C

摘要

Zirconium alloys have been applied as fuel cladding materials in the light water reactors (LWRs) during the past few decades The zircaloys may be exposed in nitrogen-containing environments in the case of open or failed reactor pressure vessels as well as during accidents of spent fuel pools and transport casks[1,2]. Hence, the degradation of zirconium alloys in nitrogen -containing atmospheres need to be investigated. A compact oxide coating of ~10 μm thick on ZIRLO alloy was fabricated by plasma electrolytic oxidation (PEO). The morphologies, compositions, phase constituents before and after exposures in N2 and N2+steam environments at 900 and 1000° C were characterized. The PEO coating greatly enhanced the corrosion resistance of ZIRLO alloy in the N2+steam atmosphere at 900 and 1000° C. The kinetic curves transformed from parabolic behavior for bare alloy and exponential behavior for PEO -coated alloy at pre-transition stage to linear at post-transition stage, due to the formation of ZrN and its re-oxidation.