X-Ray Diffraction Study of Phase Composition and Residual Stress in Cr–Zr Coatings for Accident Tolerant Fuel Systems..

Chromium based coatings are among the most promising candidates for enhancing the accident tolerance of zirconium alloy fuel claddings. In this work, oxide phase formation and XRD derived residual stress of Cr–Zr coated zirconium cladding were systematically investigated. X ray diffraction analysis revealed the formation of Cr₂O₃ and ZrO₂ oxides, including both tetragonal and monoclinic ZrO₂ phases, following high temperature oxidation obtained by confocal plasma device. The strong reflection at ~36° originates mainly from Cr₂O₃ (110), while peak asymmetry indicates a minor contribution from tetragonal ZrO₂. Residual strains were quantified from diffraction peak broadening and converted to residual stresses using phase specific elastic moduli. The results show that tetragonal ZrO₂ exhibits the highest compressive residual stress, followed by Cr₂O₃, while monoclinic ZrO₂ displays significantly lower values due to stress relaxation associated with the tetragonal to monoclinic phase transformation. The coexistence of hard Cr₂O₃ and stress relieving ZrO₂ phases results in a mechanically graded oxide scale, which is expected to improve spallation resistance and mechanical integrity under accident relevant conditions.