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选用织构相同的Zr-0.72Sn-0.32Fe-0.14Cr-x Nb(x=0,0.12,0.28,0.48,0.97,质量分数,%)合金片状样品,利用高压釜在500℃,10.3 MPa过热蒸汽中进行500 h的腐蚀实验,用TEM和SEM分别观察了合金的显微组织和氧化膜断口形貌,研究了Nb含量对锆合金耐腐蚀性能的影响.结果表明,5种合金样品都未出现疖状腐蚀,并且各自的轧面(SN面)、垂直于轧向的截面(SR面)和垂直于横向的截面(ST面)上氧化膜的厚度没有明显差异,没有腐蚀各向异性的特征.当Nb含量超过0.28%后,腐蚀250 h后合金的腐蚀速率随着Nb含量的增加而增加,合金的耐腐蚀性能变差.Nb的添加会对合金中第二相的晶体结构产生影响,低Nb的合金中主要含fcc结构的Zr(Fe,Cr)2或Zr(Fe,Cr,Nb)2型第二相,而高Nb的合金中主要含hcp结构的Zr(Fe,Cr,Nb)2型第二相.
The same flaky Zr-0.72Sn-0.32Fe-0.14Cr-xNb (x = 0,0.12,0.28,0.48,0.97, mass fraction,%) alloy flake samples were selected and sintered at 500 ℃, 10.3 MPa The corrosion experiments were conducted in superheated steam for 500 h. The microstructure and oxide film fracture morphology of the alloy were observed by TEM and SEM respectively. The effect of Nb content on the corrosion resistance of zirconium alloy was also studied. The results show that all five alloy samples No pitting corrosion occurred, and there was no significant difference in the thickness of the oxide film on the respective rolled surface (SN surface), the cross section perpendicular to the rolling direction (SR surface) and the cross section perpendicular to the transverse direction (ST surface), and no corrosion anisotropy When the content of Nb exceeds 0.28%, the corrosion rate of the alloy increases with the increase of Nb content after 250 h of corrosion, and the corrosion resistance of the alloy becomes worse.The addition of Nb can cause the crystal structure of the second phase in the alloy , The second phase of Zr (Fe, Cr) 2 or Zr (Fe, Cr, Nb) 2 mainly containing fcc structure in the low Nb alloy and the second phase of the hcp structure mainly containing Zr (Fe, Cr , Nb) 2 type second phase.