Zr-1Nb-xCu合金在400℃过热蒸汽中的耐腐蚀性能

Corrosion Resistance of Zr-1Nb-xCu Alloys in Super-Heated Steam at 400 ℃

摘要:

采用静态高压釜腐蚀试验研究了在Zr-1Nb锆合金基础上添加Cu的Zr-1Nb-xCu（x=0~0.5，质量分数，%)合金在400 ℃/10.3 MPa过热蒸汽中的耐腐蚀性能，用TEM和SEM分别观察了合金的显微组织和氧化膜的断口形貌。结果表明，当Zr-1Nb合金中添加的Cu含量不超过0.2％时，大部分Cu都固溶在α-Zr中，合金中析出的第二相主要为尺寸细小的β-Nb，这时合金在400 ℃/10.3 MPa过热蒸汽中的耐腐蚀性能会随着合金中Cu含量的增加而得到明显的提高；当Zr-1Nb合金中添加的Cu含量超过0.2％时，合金中析出了Zr2Cu型第二相，且析出的Zr2Cu型第二相会随着Cu含量的增加而数量增多，尺寸增大。在Zr-1Nb-0.35Cu合金中，析出了适量的Zr2Cu型第二相，这对改善合金在400 ℃/10.3 MPa过热蒸汽中的耐腐蚀性是有利的；但是在Zr-1Nb-0.5Cu合金中，由于析出了数量较多且尺寸较大的 Zr2Cu型第二相，在400 ℃过热蒸汽中腐蚀时将诱发疖状腐蚀，对合金的耐腐蚀性能是有害的。

关键词:锆合金;合金元素Cu;耐腐蚀性能;显微组织;疖状腐蚀

Abstract:

The effect of Cu content on the corrosion resistance of Zr-1Nb-xCu alloys (x=0~0.5, mass fraction, %) was investigated in superheated steam at 400 ℃ and 10.3 MPa by autoclave tests. The microstructure of the alloys and the fracture surface of oxide films on the corroded specimens were observed by TEM and SEM, respectively. The results show that when the addition of Cu in the Zr-1Nb alloys is below 0.2%, the main second phase particles (SPPs) are β-Nb in smaller size, and Cu mainly dissolved in the α-Zr matrix, the corrosion resistance of the alloys is improved markedly with the increase of Cu content. When the addition of Cu is above 0.2%, the SPPs of Zr2Cu are precipitated. The size and amount of Zr2Cu particles become larger with the increase of Cu content. The Zr-1Nb-0.35Cu alloy, in which the SPPs of Zr2Cu are moderate in size and amount, shows the best corrosion resistance. However, the Zr-1Nb-0.5Cu alloy, in which the SPPs of Zr2Cu are larger and more, shows the worst corrosion resistance and nodular corrosion appeares during the autoclave tests in superheated steam at 400 ℃.

Key words:zirconium;alloy, alloying;element Cu, corrosion;resistance, microstructure, nodular;corrosion