90Nb-10Zr合金在500 ℃过热蒸汽中的腐蚀行为

Corrosion behavior of 90Nb-10Zr alloy in 500 ℃ super-heated steam

摘要:

为深入研究锆合金中β-Nb第二相粒子在500 ℃、10.3 MPa过热蒸汽中的腐蚀行为，利用真空非自耗电弧炉熔炼了β-Nb第二相合金90Nb-10Zr，在静态高压釜中进行500 ℃、10.3 MPa过热蒸汽腐蚀实验，利用XRD、SEM和TEM分析了氧化膜的显微组织。结果表明，90Nb-10Zr合金腐蚀1 h时，外表面与腐蚀介质直接接触被氧化成单斜结构的Nb2O5。腐蚀7 h时，由于腐蚀介质中的氧化性物质需向内扩散才会发生进一步腐蚀，90Nb-10Zr合金表面的氧化膜为双层结构：外层为单斜结构的Nb2O5，内层为四方结构的NbO2；在本研究中没有检测到Zr单独的氧化物。这一氧化过程可以合理解释含Nb锆合金在过热蒸汽中的腐蚀行为与Nb含量的关系。

Abstract:

In order to further study the corrosion behavior of β-Nb second phase particles (SPPs) in zirconium alloys, a bulk 90Nb-10Zr alloy was prepared using vacuum non-consumable arc furnace based on the chemical composition and crystal structure of β-Nb SPPs. The 90Nb-10Zr alloy was corroded in 500 ℃ and 10.3 MPa super-heated steam in a static autoclave for 1 h and 7 h. X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to characterize the microstructure of the oxide film formed on the alloy. The results revealed that the monoclinic Nb2O5 was formed directly when 90Nb-10Zr alloy was corroded for 1 h, because the corrosion medium was directly contact with the outer surface of the alloy. When 90Nb-10Zr alloy was corroded for 7 h, the oxide film on the alloy was double-layer structure: the outer layer was monoclinic Nb2O5 and the inner layer was tetragonal NbO2 since the occurrence of further corrosion required the internal diffusion of the oxidizing substances in the corrosion medium. No single oxide of Zr was detected in this study. This oxidation process can reasonably explain the relationship between the Nb content and the corrosion behavior of Nb-containing zirconium alloy in super-heated steam.