Barrier oxide chemistry and hydrogen pick-up mechanisms in zirconium alloys

Journal article, 2016

The chemistry of barrier oxide layers formed on zirconium alloys was investigated using atom probe tomography (APT). Grain boundary segregation of Fe and Ni was observed. The Zr(Fe, Cr)2 particles maintain a constant Zr:Fe:Cr ratio through the oxide until they reach an oxygen content of approxi- mately 50 at%, when Fe depletion occurs. Enrichment of hydrogen along oxide crystallite boundaries was observed, which is interpreted as a sign of ingress being localized to grain boundaries. TEM revealed poros- ity networks around particles and oxide grain boundaries. It is proposed that pores are local reduction sites where H2 evolves on transition metal sites.