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通过分析NZ2合金在360℃、18.6 MPa含锂水和400℃、10.3 MPa蒸汽中腐蚀后氧化膜的晶体结构,研究了腐蚀过程中氧化膜晶体结构的转变及其对锆合金耐腐蚀性能的影响.结果表明:NZ2合金腐蚀后氧化膜的结构以单斜氧化锆为主,还有一定量畸变了的四方氧化锫.四方氧化锆主要由氧化膜内的压应力稳定.随着腐蚀时间的延长,氧化膜与金属间的界面向前推进,当氧化锆中的压应力不足以稳定四方相时,四方氧化锆转变为单斜氧化锆.从氧化膜与金属间的界面到氧化膜的外表面,四方相的含量不断降低,界面处的四方相含量最高.NZ2合金在360℃含锂水中腐蚀时,氧化膜内四方相向单斜相的转变速度比在400℃蒸汽中腐蚀时四方相向单斜相的转变速度低得多.四方相向单斜相的转变是决定锆合金抗腐蚀性能的主要因素,四方相转变得越快,其含量越低,腐蚀速率越高.
By analyzing the crystal structure of oxide film of NZ2 alloy after being corroded in 360 ℃, 18.6 MPa lithium-containing water and steam at 400 ℃ and 10.3 MPa, the crystal structure transition of oxide film and its effect on the corrosion resistance of zirconium alloy were studied. The results show that the structure of the oxide film after the corrosion of NZ2 alloy is monoclinic zirconia and a certain amount of distorted tetragonal zirconia.The tetragonal zirconia is mainly stabilized by the compressive stress in the oxide film.With the extension of the corrosion time, When the compressive stress in zirconia is not enough to stabilize the tetragonal phase, the tetragonal zirconia is transformed into monoclinic zirconia, and from the interface between the oxide film and the metal to the outer surface of the oxide film, The content of tetragonal phase is continuously decreased and the tetragonal phase content is the highest at the interface.The transformation speed of tetragonal phase monoclinic phase in the oxide film is higher than that of tetragonal phase monoclinic phase The transition speed is much lower.The transformation of tetragonal phase monoclinic phase is the main factor that determines the corrosion resistance of zirconium alloy, the faster the tetragonal phase transition, the lower the content, the higher the corrosion rate.