Zr-0.7Sn-0.35Nb-0.3Fe-xGe合金在高温高压LiOH水溶液中耐腐蚀性能的研究

STUDY ON THE CORROSION RESISTANCE OF Zr-0.7Sn-0.35Nb-0.3Fe-xGe ALLOY IN LITHIATED WATER AT HIGH TEMPERATURE UNDER HIGH PRESSURE

利用静态高压釜腐蚀实验研究了Zr-0.7Sn-0.35Nb-0.3Fe-xGe(x=0.05,0.1,0.2,质量分数,%)系列合金在360℃/18.6 MPa/0.01 mol/L LiOH水溶液中的耐腐蚀性能;利用TEM和SEM分别观察了合金基体的显微组织和氧化膜的显微组织.结果表明:Ge可以显著改善Zr-0.7Sn-0.35Nb-0.3Fe合金在高温高压LiOH水溶液中的耐腐蚀性能,当Ge含量为0.1%时,合金的耐腐蚀性能最佳.在Zr-0.7Sn-0.35Nb-0.3Fe-xGe系列合金中发现尺寸较小的hcp结构的Zr(Fe,Cr,Nb)_2型、Zr(Fe,Cr,Nb,Ge)_2型第二相和尺寸较大的四方结构的Zr_3Ge型第二相.腐蚀220 d的Zr-0.7Sn-0.35Nb-0.3Fe-0.1Ge合金氧化膜致密,厚度较薄,几乎没有微孔隙和微裂纹,ZrO_2柱状晶较多.这说明添加适量的Ge不仅可以有效延缓氧化膜中空位扩散凝聚形成微孔隙和微孔隙发展形成微裂纹的过程,还可以延迟ZrO_2由柱状晶向等轴晶的演化,从而改善合金的耐腐蚀性能.

The corrosion resistance of Zr 0.TSn 0.35Nb 0.3Fe xGe （x=0.05, 0.1, 0.2, mass fraction, %） alloys was investigated in lithiated water with 0.01 mol/L LiOH at 360 ℃/18.6 MPa by autoclave tests. The microstructures of the alloys and oxide films on the corroded specimens were observed by TEM and SEM. The results show that the corrosion resistance of the Zr 0.TSn 0.35Nb 0.3Fe alloys in lithiated water at high temperature under high pressure is markedly improved by Ge addition. The alloy with 0.1%Ge shows the best corrosion resistance. In Zr-0.7Sn 0.35Nb-0.3Fe-xGe alloys, there exists fine Zr（Fe, Cr, Nb）2 and Zr（Fe, Cr, Nb, Ge）2 second phase particles （SPPs） with a close-packed hexagonal crystal structure （hcp） and coarse Zr3Ge SPPs with a tetragonal crystal structure （TET）. The oxide films formed on the Zr 0.TSn 0.35Nb 0.3Fe-0.1Ge alloys cor roded for 220 d are compact and thin. The micro-pores and micro-cracks are hardly detected andmany ZrO2 columnar grains exist in the oxide films formed on the Zr 0.7Sn-0.35Nb-0.3Fe-0.1Ge alloys. This indicates that the suitable amount of Ge could not only delay the process that the vacancies diffuse to form micro-pores and micro-pores develop to form micr^cracks, but also could retard the evolution from ZrO2 columnar grains to ZrO2 equiaxed grains.