A mechanism assessment for the anti-corrosion of zirconia coating under the condition of subcritical water corrosion

[Display omitted] •Tetragonal ZrO2 is stabilized to ambient temperature by Ar8+ irradiation.•A spontaneous martensitic transformation is triggered by an interface distortion.•Both oxygen defects and irradiation distortion help to stabilize T-phase.•Bombardment induced ZrO2 has superior stability against corrosion compared with as deposited.•The well persistence of T-ZrO2 endows enhanced barrier effect to oxygen. Natural grown ZrO2 cannot effectively protect Zr alloy due to the poor phase stability. In this work, a pre-defected ZrO2 coating was fabricated on Zr alloy and further bombarded by Ar8+. A spontaneous martensitic transformation in ZrO2 coating was triggered by lattice distortion and gradient mismatch on the interface. Additionally, Ar8+ bombardment induced the formation of interstitial-vacancy pairs in ZrO2. DFT modeling proved that the interstitial-vacancy pairs were superior in stabilizing T-phase ZrO2, compared with native oxygen vacancies. A mechanism for enhanced corrosion resistance was proposed based on the unique interface and defect state.