Breakaway characterization of Zircaloy-4 oxidized in steam and in oxygen at high temperatures using HT- XRD analysis

Effects of Hydrogenation on the Corrosion Behavior of Zircaloy-4

“…Some researchers suggest that the initial stage of corrosion results in the formation of a compact t-ZrO 2 oxide film, and as the thickness of the oxide film increases, the compressive stress in the outer oxide film gradually diminishes, leading to a gradual transformation of t-ZrO 2 into loose m-ZrO 2 . The phase transformation in the oxide film can induce cracks and other defects, thereby accelerating zirconium alloy corrosion [39][40][41]. Based on our findings, it can be concluded that hydrogenation has little effect on the t-ZrO 2 phase content in the oxide film, and there is no direct correspondence between the t-ZrO 2 content and the corrosion resistance of Zircaloy-4 in 360 • C/18.6 Mpa/Li + B aqueous solution samples corroded for 70 days is presented in Figure 11 and Table 1.…”

Parallel mechanism of growth of the oxide and α-Zr(O) layers on Zircaloy-4 oxidized in steam at high temperatures

“…Several explanations have been suggested in the literature such as the destabilizing effect of the tetragonal-to-monoclinic phase transformation in the oxide layer [11,16,17]. A recent study using HT XRD analysis demonstrated that this phase transformation is not the main cause of the breakaway oxidation [18]. Other hypotheses suggest that the stress relaxation in the oxide after a certain incubation time [19,20] and the formation of an interconnected network of micropores can cause a direct access of the oxidizing gas to the metal/oxide interface [21,22].…”