Nb对锆合金表面及氧化膜中杂质元素C分布的影响

Influences of Nb on Impurity C Distribution in Surface and Oxide Film of Zirconium Alloys

摘要:

以Zr-0.75Sn-0.35Fe-0.15Cr-xNb合金为研究对象，在360 ℃/18.6 MPa去离子水中进行580 d静态高压釜实验，借助SIMS检测碳元素由氧化膜表面到氧化膜/基体界面的浓度梯度分布，通过XPS分析基体表面碳的化合价态。实验结果表明：Zr-0.75Sn-0.35Fe-0.15Cr合金轧制面（S_N）上氧化膜中C浓度明显高于横向垂直面（S_T）氧化膜中的C浓度，添加0.15wt% Nb可以显著降低S_N面氧化膜中的C浓度，减小不同表面氧化膜的C浓度分布差异。不含Nb合金S_N表面的碳/锆比值随温度升高增幅更大，说明Nb与Zr在与C的结合方面可能存在竞争关系。结合Zr-0.75Sn-0.35Fe-0.15Cr合金在实验条件下表现出的腐蚀各向异性特征，从Nb对杂质元素C分布影响的角度讨论了C与各向异性腐蚀的关系。

Abstract:

Zr-0.75Sn-0.35Fe-0.15Cr-xNb alloys were investigated, and static autoclave tests were conducted in deionized water at 360 ℃ and 18.6 MPa for 580 d. Secondary ion mass spectrometry was employed to characterize the concentration gradient distribution of carbon from the oxide film surface to the oxide/matrix interface, and X-ray photoelectron spectroscope was used to analyze the valence states of carbon on the substrate surface. The experimental results show that the C concentration in the oxide film on the rolling surface (S_N) of the Zr-0.75Sn-0.35Fe-0.15Cr alloy was significantly higher than that on the surface perpendicular to the transversal direction (S_T). Adding 0.15wt% Nb can considerably decrease the C concentration in the oxide film and reduce the difference in carbon concentration distribution among oxide films on different surfaces. The C/Zr ratio on the S_N surface of the Nb-free alloy increases more obviously with the rise of temperature, suggesting a potential competitive relationship between Nb and Zr in C binding. In conjunction with experimental observations of corrosion anisotropy of the Zr-0.75Sn-0.35Fe-0.15Cr alloy, this study explored the relationship between C and anisotropic corrosion from the perspective of the effects of Nb on impurity C distribution.