几种不锈钢及Ni-Dy两相合金在熔融盐中的腐蚀行为

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	几种不锈钢及Ni-Dy两相合金在熔融盐中的腐蚀行为
	刘颖
学位类型	博士
导师	曾潮流
	2011
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	腐蚀科学与防护
关键词	不锈钢 Ni-dy合金熔融盐腐蚀 (Li Na k)2co3 Licl-li2o Stainless Steels Ni-dy Alloys Molten Salt Corrosion (Li Na k)2co3
摘要	"太阳能热动力发电站的储能系统和核电站的乏燃料的处理面临着一个同样的问题，即结构材料和熔盐的兼容性问题。了解金属材料在熔融盐里的腐蚀行为，对材料的选择至关重要。本文采用浸泡的方法研究了不锈钢及镍镝合金分别在熔融碳酸盐和熔融LiCl-Li2O中的腐蚀行为，取得的成果如下：研究了304、310、316三种奥氏体不锈钢分别在600oC、700oC、800oC熔融(Li, Na, K)2CO3中，于空气气氛下的腐蚀行为。不锈钢的腐蚀速率随着温度的升高而增大。304和316不锈钢都生成了三层结构的氧化膜，而310不锈钢的氧化膜由外层的LiFeO2和内层的LiCrO2组成。当覆盖气氛由空气被无氧化性的N2取代时，304和316不锈钢在700oC熔融 (Li, Na, K)2CO3中的腐蚀速率减小。向熔融(Li, Na, K)2CO3中加入10 wt.% (Na, K)Cl加速了不锈钢特别是310不锈钢的腐蚀。循环进行的氯化-氧化反应是不锈钢腐蚀速率增大的原因。研究了B2205奥氏体不锈钢、B409M与B439M铁素体不锈钢、Ni及Ni-Dy两相合金分别在700oC熔融LiCl及LiCl-5 wt.%Li2O中，于空气气氛下的腐蚀行为。不锈钢在两种熔融盐中均遭受了严重的腐蚀。腐蚀速率随着合金中Cr含量的增大而降低，原因可能是Cr含量高的不锈钢形成了相对富Cr的氧化膜。Dy使Ni在熔融LiCl中的腐蚀速率增大，这可能是由于生成了蒸汽压比NiCl2高的DyCl3。在熔融LiCl-Li2O中腐蚀时，Ni-1Dy和Ni-3Dy的腐蚀速率略小于 Ni，而Ni的腐蚀速率略小于Ni-5Dy和Ni-10Dy。"
其他摘要	"The compatibility between structural vessel material and the molten salts is a big issue encountered by the energy storage system for solar thermal power station and by the treatment of spent uranium-oxide based nuclear fuel. It is of great importance to clarify the corrosion behavior of metallic materials in molten salts for the selection of appropriate structural materials. In this dissertation, the corrosion behavior of several stainless-steels and binary Ni-Dy alloys in molten carbonates and molten LiCl-Li2O, respectively, was examined by immersion method. The main achievements are as follows: The corrosion behavior of austenitic 304ss, 310ssand 316ss stainless steels in an eutectic (Li, Na, K)2CO3 in air was investigated at 600oC, 700oC, 800oC, respectively. The three alloys suffered from fast corrosion at three temperatures, among which 310ss showed the best corrosion resistance. Moreover, the corrosion rates of the steels were increased by increasing the temperature. Both 304ss and 316ss have formed a three-layered scale composed of an outer LiFeO2 layer, a middle LiFe5O8 layer and an inner mixed layer of FeCr2O4, LiCrO2 and some uncorroded metallic phases rich in Ni and Fe, while the scales formed on 310ss consisted of outer LiFeO2 and an inner LiCrO2 layer. Using no-oxidizing N2 instead of air as the cover gas helped to reduce the corrosion of 304ss and 316ss in molten (Li, Na, K)2CO3 at 700oC. However, the corrosion of 310ss was accelerated to a certain extent. The addition of chlorides to molten carbonate may improve their fluidity, but probably producing a more corrosive melt. The corrosion experiments at 700 oC confirmed that the addition of 10 wt.% eutectic (Na, K)Cl to molten (Li, Na, K)2CO3 accelerated the corrosion of the alloys, especially 310ss. The corrosion rate of 304ss is slightly higher than that of 316ss, while 310ss still exhibits the best corrosion resistance. The cyclic chloridation/oxidation reactions are responsible for the accelerated corrosion. The corrosion behavior of austenitic B2205, ferritic B409M and B439M stainless steels and of Ni and binary Ni-Dy alloys containing 1, 3 ,5 and 10 wt.%Dy, respectively, in molten LiCl and LiCl-5 wt.%Li2O in air at 700oC was also investigated. The three stainless steels suffered fast corrosion in both melts, with a lower corrosion rate for the higher Cr-containing steels due to the formation of a Cr-rich scale. Moreover, the presence of Li2O in the melt decreased the corrosion of the steels due to the fact that Li2O promotes the formation of insoluble Li-containg products. The addition of Dy to Ni increased its corrosion rate in molten LiCl at 700oC, with a more evident effectiveness for a higher Dy content, probably due to the formation of DyCl3 with a higher vapor pressure than NiCl2. In molten LiCl- Li2O the corrosion rates of Ni-1Dy and Ni-3Dy were slightly lower than that of pure Ni, which, hower, was corrded more slowly than both Ni-5Dy and Ni-10Dy. Though a regular effect of Dy on the corrosion of Ni in molten LiCl-Li2O was not observerd, the corrosion rate of Ni-Dy alloys was increased by increasing the content of Dy."
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64262
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	刘颖. 几种不锈钢及Ni-Dy两相合金在熔融盐中的腐蚀行为[D]. 北京. 中国科学院金属研究所,2011.