含Nb奥氏体不锈钢中NbC的液态Pb-Bi共晶腐蚀行为及其对氧化层形成的影响  

Corrosion Behavior of NbC and Its Effect on Corrosion Layer Formation in Liquid Lead-Bismuth Eutectic of Nb-Containing Austenitic Stainless Steel

作　　者：吴炀 谢昂 陈胜虎[1] 姜海昌[1] 戎利建[1] WU Yang;XIE Ang;CHEN Shenghu;JIANG Haichang;RONG Lijian(CAS Key Laboratory of Nuclear Materials and Safety Assessment,Institute of Metal Research,Chines Academy of Sciences,Shenyang 110016,China;School of Materials Science and Engineering,University of Science and Technology of China,Shenyang 110016,China)

机构地区：[1]中国科学院金属研究所中国科学院核用材料与安全评价重点实验室,沈阳110016 [2]中国科学技术大学材料科学与工程学院,沈阳110016

出　　处：《金属学报》2025年第2期287-296,共10页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目,No.51871218;中核集团领创科研项目。

摘　　要：新型Nb稳定化奥氏体钢被视为铅冷快堆的候选结构材料,在制备或服役过程中会产生初生或二次NbC,NbC在液态铅铋中的腐蚀行为及其对材料耐腐蚀性能的影响目前尚不明确。采用SEM、EPMA、XRD、TEM等手段研究了一种含Nb奥氏体不锈钢分别在550和600℃静态饱和氧液态Pb-Bi共晶(LBE)中的腐蚀性能,重点考察了腐蚀过程中初生NbC的演化行为及其对氧化层形成的影响。结果表明,550℃下初生NbC的氧化倾向与其在样品中的分布位置有关,位于样品原始表面的NbC易发生氧化,而位于样品内部的NbC则不会发生氧化,这是由于内氧化层中的氧分压尚未达到NbC氧化所需的平衡氧分压。温度提高至600℃后,氧分压达到了NbC氧化的平衡氧分压,位于样品原始表面以及样品内部的NbC均会发生氧化。NbC氧化成Nb_(2)O_(5)的Pilling-Bedworth比(PBR)大于2,对周边区域的氧化层产生较大的压应力,导致氧化态NbC周围氧化层中产生微裂纹。同时,NbC氧化伴随着CO_(2)气体的产生,位于样品内部的NbC氧化产生的CO_(2)降低了氧化层致密性,使得氧化层的生长速率加快。The lead-cooled fast reactor is considered one of the promising Generation IV nuclear energy systems.Structural materials used in the construction of pressure vessels and internals for this reactor include 300 series austenitic stainless steels.Nb-containing austenitic stainless steels are developed to improve corrosion properties,mechanical properties,and irradiation resistance.However,coarse primary NbC carbides are formed during solidification in these steels and cannot be eliminated through subsequent hot working and heat treatment.Recently,researchers have found different oxidation behaviors between secondary phase particles and the matrix,which affect the material's corrosion properties.However,the oxidation behaviors of primary NbC are rarely reported.This study analyzes the corrosion behaviors of a solution-treated Nb-containing austenitic stainless steel plate after exposure to oxygensaturated liquid lead-bismuth eutectic(LBE)at 550 and 600~oC using SEM,EPMA,XRD,and TEM.The results show that the oxidation probability of NbC is correlated with its location in the samples at 550~oC.NbC at the initial surface is easily oxidized,while NbC within the interior is difficult to oxidize due to the low equilibrium oxygen partial pressure in the inner oxide layer,which suppresses the oxidation of NbC.However,NbC at the initial surface and within the interior are prone to be oxidized as the temperature increases to 600~oC.Compared to the matrix,NbC oxidizes into Nb_2O_5,resulting in a higher PillingBedworth ratio(PBR).This leads to high compressive stress and resultant microcrack formation in the surrounding oxide layer.Additionally,the presence of CO_(2)generated during the oxidation of NbC within the interior reduces the compactness of the oxide layer,leading to a higher growth rate.

关 键 词：含Nb奥氏体不锈钢 初生NbC Pb-Bi腐蚀 氧化机制 

分 类 号：TG174[金属学及工艺—金属表面处理]