Zr-702锆板TIG焊接接头硫酸环境腐蚀性能研究

Study on Corrosion Behavior of Zr-702 zirconium plate TIG welded joint in sulfuric acid environment

摘要:

采用99.999％高纯Ar作为保护气体进行Zr-702锆板的TIG焊接实验,采用静态等温失重法,研究了Zr-702焊接接头在250 ℃,15%(ω)硫酸介质中浸泡时长对其腐蚀性能的影响,探究其腐蚀机理。研究结果表明：在相同温度与浓度,不同浸泡时长的硫酸介质中,焊接接头的腐蚀速率均大于母材的腐蚀速率,当浸泡时长为2天时,焊接接头与母材均具有良好的耐腐蚀性能；当浸泡时长大幅增加至180天时,焊接接头与母材腐蚀速率均有明显升高,浸泡时长对焊接接头与母材的腐蚀速率影响较大；通过对浸泡时长为180天的试样进行成分组织性能表征分析可知,焊接接头焊缝区和热影响区均析出大量氢化锆,母材或母材区氢化锆数量相对较少；Zr-702的母材在硫酸介质中的腐蚀为均匀腐蚀和氢腐蚀共同作用,焊接接头因各区存在明显组织梯度而存在电位差,故其腐蚀为电偶腐蚀和氢脆联合作用的局部腐蚀。

Abstract:

TIG welding experiment of Zr-702 zirconium plate was carried out with 99.999% high purity Ar as shielding gas. The Zr-702 welding joint was studied at 250%, 15%(ω) by static isothermal weight loss method. Influences of soaking time in sulphuric acid medium on its corrosion performance and explore its corrosion mechanism. The results show that the corrosion rate of welded joint is higher than that of base metal in the same temperature and concentration and different soaking time in sulfuric acid medium. When soaking time is 2 days, both welded joint and base metal have good corrosion resistance. The corrosion rate of welded joint and base metal increases significantly when the soaking time increases to 180 days, and the corrosion rate of welded joint and base metal is greatly affected by the soaking time. According to the characterization and analysis of composition, structure and properties of 180-day soaked samples, a large amount of zirconium hydride was precipitated in weld zone and heat-affected zone of weld joint, and the amount of zirconium hydride in base metal or base metal zone was relatively small. The corrosion of Zr-702 base metal in sulphuric acid medium is the combination of uniform corrosion and hydrogen corrosion. Potential difference exists in weld joint due to obvious structural gradient in each zone. Therefore, its corrosion is the local corrosion combined by galvanic corrosion and hydrogen brittleness.