Oxidation and Quench Behavior of Cold Spraying Cr-Coated Zircaloy Fuel Cladding Under Severe Accident Scenarios [in press]

The oxidation performance and quench behavior of
cold spraying Cr coated Zircaloy-4 cladding tubes were investigated from 1100°C up to 1500°C in steam. The coated samples displayed significantly improved oxidation resistance, good thermal shock resistance and high post-quench ductility during oxidation at 1100°C and 1200°C for 1 hour accompanied by subsequent quench in water. However, substantial bending of the coated tubes was observed during oxidation at 1100°C, which led to loss of protective effect of the coatings on the tensile (convex) side. The underlying mechanisms for the occurrence of bending phenomenon at such temperature seems to be related with the residual stress state and high-temperature creep behavior of the coated cladding. Once the oxidation temperature exceeds the Cr-Zr eutectic temperature (~1330°C), oxygen drives the Cr diffusing inwardly (owing to the low solubility of Cr in ZrO2) and the formation of liquid phase contributes to rapid degradation of the coated cladding, connected with a much faster oxidation rate compared to the uncoated reference sample.
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