Corrosion Behaviors of Zr-Sn-Nb-Fe-Mo Alloy in High Temperature and High Pressure Water

The corrosion resistance of Zr-Sn-Nb-Fe-Mo alloy in 360 ℃/18.6 MPa deionized water was studied by autoclave corrosion test. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and laser Raman spectroscopy were used to analyze the microstructure of the alloy before and after corrosion. The results showed that the corrosion weight gain of the alloy after 300 days of corrosion reduced by more than 30% compared to ZIRLO alloy. Zr(Nb,Fe)₂ and Zr(Nb,Fe,Mo)₂ second phase particles with HCP structure generated in the alloy were dispersed uniformly. After 260 days of corrosion, there were obvious cracks in the oxide film parallel to the oxide film/substrate interface. The significant reduction of t-ZrO₂ in the tetragonal phase was an important factor that caused cracks in the oxide film and accelerated alloy corrosion. The Zr(Nb,Fe,Mo)₂ second-phase particles generated by adding Mo element played a role in delaying oxidation and reducing the internal stress in the oxide film.