143 / 2023-11-22 16:17:13

Corrosion degradation mechanism of Cr coated Zr-4 alloy under simulated nuclear conditions for accident tolerant fuel

Cr coatings with thickness of about 19μm were synthesized on Zr-4 cladding using plasma enhanced arc ion plating. A Zr-Cr micro-diffusion layer was formed by Cr ions cleaning before deposition. Cr coatings exhibit an obvious columnar crystal structure with average grain size of 1.26μm by SEM and EBSD. A long-term aqueous test at 420℃±3℃、10.3MPa±0.7MPa and isothermal oxidation tests at 900℃～1300℃ in air were conducted to evaluate the Cr coated Zr-4 cladding. All the results showed that the Cr coatings had a significant protective effect to the Zr-4 alloy. However, the corrosion deterioration mechanism is different depending on the corrosion environment. A gradual thinning of Cr coating was observed in long-term aqueous test, but a cyclic corrosion mechanism of Void initiation- Propagation- Cracking at the oxide film interface is the main corrosion characteristic of Cr coating in isothermal oxidation. Different corrosion models are constructed to explain the corrosion mechanism.