水化学和腐蚀温度对锆合金氧化膜中压应力的影响

在不同水化学条件下,对Zr-4和N18管状样品进行腐蚀实验,然后用氧化膜卷曲法测量腐蚀样品氧化膜中的压应力,研究腐蚀温度、水化学对氧化膜中压应力随厚度变化的影响规律.实验结果表明,Zr-4和N18样品氧化膜中的压应力均按360℃去离子水>400℃过热蒸汽>360℃L iOH水溶液的顺序依次减小.在360℃L iOH水溶液中腐蚀时,氧化膜中的压应力最低,这与L i+和OH-会渗入氧化膜,降低氧化锆表面自由能,从而加速氧化膜中空位的扩散凝聚、孔隙的形成和微裂纹发展的过程有关.高温使空位的扩散加快,促进了氧化膜中压应力的弛豫过程.

Effect of Water Chemistry and Corrosion Temperature on Compressive Stress of Oxide Films on Zirconium Alloys

To investigate the effect of corrosion temperature and water chemistry on compressive stress with the increase of oxide film thickness,Zr-4 and N18 tubular specimens were corroded in three kinds of water chemistry.Compressive stress of oxide films formed on the outside of the tubular specimens was measured with a curling method of oxide film.Experimental results indicate that compressive stress in oxide films decreases in the sequence of 360 ℃ deionized water >400 ℃ super-heated steam >360 ℃ lithiated water.Li+ and OH-ions incorporated into the oxide films decrease the surface free energy of oxide.As a result,the diffusion of vacancies,formation of pores and development of micro-cracks are enhanced.This is the reason why compressive stress of oxide films formed in 360 ℃ lithiated water is the lowest.Diffusion of vacancies is promoted at higher temperature,resulting in relaxation of compressive stress in oxide films.Therefore compressive stress of oxide films formed in 400 ℃ super-heated steam is lower than that formed in 360 ℃ deionized water.