Zr-XSn-1Nb-0.3Fe（X=0~1.5）合金的腐蚀行为研究

Corrosion Behavior of Zr-XSn-1Nb-0.3Fe（X=0~1.5） Alloys

通过高压釜腐蚀实验研究了Zr-XSn-1Nb-0.3Fe合金（X=0~1.5,质量分数,%）在360℃/18.6 MPa纯水、360℃/18.6 MPa/0.01 mol·L-1 LiOH水溶液以及400℃/10.3 MPa过热蒸汽中的耐腐蚀性能。结果表明,随着Sn含量从1.5%降低至0.6%,合金试样腐蚀增重降低;进一步降低Sn含量时,合金在纯水和蒸汽中的腐蚀增重没有明显变化,但在LiOH水溶液中的腐蚀增重反而增加。采用透射电镜表征腐蚀前的显微组织发现,随着Sn含量的变化,合金中第二相的大小及类型相接近,但面密度随着Sn含量的增加而减少。采用激光拉曼光谱分析腐蚀过程中氧化膜晶体结构表明,腐蚀初期氧化膜的结构以m-ZrO2和t-ZrO2为主,随着腐蚀时间的增加,t-ZrO2转变为m-ZrO2;t-ZrO2转变越快,t-ZrO2含量越低,腐蚀速率越高。

To better understand the effect of tin on the corrosion behavior of Zr-Sn-Nb-Fe alloy, Zr-XSn-1Nb-0.3Fe（X=0 wt%~1.5 wt%） sheets were prepared and corroded by a static autoclave in 360℃/18.6 MPa pure water, 360℃/18.6 MPa/0.01 mol·L-1 Li OH aqueous solution and400℃/10.3 MPa superheated steam. The characteristics of the precipitates were analyzed by TEM, the crystal structure transformation of the oxide film during corrosion and its effect on the corrosion resistance of alloys were characterized by laser-Raman spectrometry. Results show that the corrosion mass gain decreases when tin content decreases from 1.5 wt% to 0.6 wt%. As tin content decreases from 0.6 wt% to 0, the corrosion mass gain hardly changes in pure water and steam. However, it is found that the corrosion mass gain increases in Li OH aqueous solution. The microstructural characteristic indicates that the crystal structure and mean size of the precipitates in all tested alloys are almost the same even though the tin considerably changes, but the area fraction of precipitates in the alloy decreases with the tin content increasing when all of the samples are heat-treated in the same condition. It is observed that the oxide film of alloys consists mostly of m-ZrO2 and t-ZrO2 when alloys are corroded in a short time. With the prolongation of corrosion time, the t-ZrO2 transforms to m-ZrO2. The higher the transformation rate, the lower the t-ZrO2 content in the oxide film and the higher the corrosion rate of alloy specimens.