Steam Oxidation of Zirconium–Yttrium Alloys from 500– $$1100\,^{\circ }\text {C}$$ 1100 ∘ C

The steam oxidation kinetics, oxide formation, and hydrogen uptake of nuclear-grade Zr with 0.01–12 wt% yttrium were studied. Metallography and diffraction of the as-received material showed yttrium remained trapped in solid solution in concentrations up to 2 wt%; therefore, steam oxidation focused on 0.01–1 wt% Y samples. Thermogravimetric analysis was performed in a steam–argon environment at $$500\,^{\circ }\text {C}, 700\,^{\circ }\text {C}, 900\,^{\circ }\text {C}$$ , and $$1100\,^{\circ }\text {C}$$ at atmospheric pressure. At $$500\,^{\circ }\text {C}$$ and $$700\,^{\circ }\text {C}$$ , increasing the yttrium concentration increased the total weight gain by up to 300% and caused an increase the oxidation power-law exponent. At $$900\,^{\circ }\text {C}$$ , increasing the yttrium concentration caused a much smaller increase in the weight gain, and resulted in a decrease in the oxidation power-law exponent. At the highest temperature, $$1100\,^{\circ }\text {C}$$ , increasing the yttrium concentration had a minimal effect on the kinetics. Transmission synchrotron diffraction and cross-sectional optical microscopy showed significant hydrogen uptake at $$500\,^{\circ }\text {C}$$ and $$700\,^{\circ }\text {C}$$ through the formation of $$\delta$$ and $$\gamma$$ zirconium hydrides. The volume of these two hydride phases increased with increasing yttrium concentration. This hydrogen uptake appears to be linked to the increase in the steam oxidation power-law exponent observed at $$500\,^{\circ }\text {C}$$ and $$700\,^{\circ }\text {C}$$ .