热老化对316LN力学性能和晶间腐蚀敏感性的影响  

Effect of Thermal Aging on Mechanical Properties and Intergranular Corrosion Resistance of 316LN

作　　者：杨宝磊 刘廷光 苏香林 范宇 邱亮 陆永浩 YANG Baolei;LIU Tingguang;SU Xianglin;FAN Yu;QIU Liang;LU Yonghao(Tianjin Heavy Equipment Engineering Research Co.,Ltd.,Tianjin 300450,China;National Center for Materials Service Safety,University of Science and Technology Beijing,Beijing 100083,China;Research Institute of Processing Technology,Inner Mongolia First Machinery Group Co.,Ltd.,North Industries Group Co.,Ltd.,Baotou 014030,China)

机构地区：[1]天津重型装备工程研究有限公司,天津300450 [2]北京科技大学国家材料服役安全科学中心,北京100083 [3]中国兵器工业集团内蒙古第一机械集团有限公司工艺研究所,包头014030

出　　处：《材料研究学报》2023年第5期381-390,共10页Chinese Journal of Materials Research

基　　金：国家重点研发计划(2019YFB1900905);中央高校基本科研业务费专项(FRF-TP-20-019A3)。

摘　　要：将热锻固溶态316LN不锈钢试样在400℃空气中热老化处理400~10000 h,使用金相显微镜、扫描电子显微镜(SEM)、电子背散射衍射(EBSD)和X射线衍射(XRD)等手段分析了固溶态及热老化试样的显微组织,用小冲杆、纳米压痕和维氏硬度测试研究了热老化对这种材料力学性能的影响;用草酸电解侵蚀方法进行晶间腐蚀试验,用EBSD和原子力显微镜(AFM)定量分析了热老化对各类型晶界晶间腐蚀敏感性的影响。结果表明,在400℃热老化10000 h后316LN不锈钢的微米级显微组织、晶粒尺寸、晶界形貌和晶界特征分布都没有明显的变化。但是,热老化使晶粒的晶格常数变小,其原因是固溶在晶粒内的间隙原子和位错等向晶界处扩散迁移,使材料的强度和硬度提高而塑性和抗晶间腐蚀性能降低。各类型晶界的晶间腐蚀敏感性都随着热老化时间的延长而提高,但是CSL晶界的晶间腐蚀敏感性低于随机晶界。Nitrogen enhanced low carbon 316LN stainless steel,as a single-phase austenitic stainless steel,is selected as a candidate material of primary pipe for the third-generation pressurized water reactors.In the present work,the solution annealed 316LN was thermal aged at 400℃for 400,1000,5000 and 10000 hours,respectively.The microstructures of the solution annealed and thermal aged steels were compared by optical microscope,scanning electron microscope(SEM),electron backscatter diffraction(EBSD)and X-ray diffraction(XRD).The effect of thermal aging on mechanical properties of the steels was evaluated by using small punch test,nanoindentation and microhardness tester.The intergranular corrosion resistance of the steels was measured by using electrolytic etching in oxalic acid solution,and the effect of thermal aging on the corrosion resistance of various types of grain boundaries were characterized by using EBSD and atomic force microscope(AFM).The results show that thermal aging at 400℃for 10000 h will not cause microstructural changes in the micron level of 316LN stainless steel.No change was observed in grain size,grain boundary morphology and characteristics of grain boundary distribution,and no new phase was formed during thermal aging.However,after thermal aging,the lattice parameter becomes smaller,which may be ascribed to that the interstitial atoms and dislocations originally dissolved in grains diffused and migrated towards the grain boundaries.This may result in changes of the mechanical properties of the 316LN,including the increase of strength and hardness,and the lower of plasticity and intergranular corrosion resistance.The intergranular corrosion susceptibilities of all types of grain boundaries increase with the extension of thermal aging time,but the susceptibility of coincidence site lattice(CSL)grain boundaries is always lower than that of random grain boundaries.Hence grain boundary engineering,which is a thermomechanical process and could produce high fraction of low-∑CSL grain boundaries i

关 键 词：金属材料 316LN不锈钢 热老化 小冲杆 晶间腐蚀 CSL晶界 

分 类 号：TG142.71[一般工业技术—材料科学与工程]