弯曲形变热处理对纯镍N6焊缝晶界特征分布及腐蚀行为的影响  

Effect of Bending Deformation and Heat Treatment on Grain Boundary Character Distribution and Corrosion Behavior for Pure Nickel N6 Weld

作　　者：柴廷玺 徐宏彤 俞友军 晏丽琴 王志全 Chai Tingxi;Xu Hongtong;Yu Youjun;Yan Liqin;Wang Zhiquan(School of Bailie Mechanical Engineering,Lanzhou City University,Lanzhou 730070,China)

机构地区：[1]兰州城市学院培黎机械工程学院,甘肃兰州730070

出　　处：《稀有金属材料与工程》2023年第10期3590-3599,共10页Rare Metal Materials and Engineering

基　　金：甘肃省科技重大专项(145RTSA004);甘肃省高等学校科研项目(2020A-128)。

摘　　要：对纯镍N6等离子弧焊缝进行“U”形弯曲形变及热处理加工(grain boundary engineering,GBE),借助电子背散射衍射(EBSD)对比分析non-GBE和GBE样品晶界特征分布及对腐蚀行为的影响。结果表明:焊缝经“U”形弯曲形变+900℃退火10min后,低ΣCSL晶界比例提高到54.1%,并形成具有Σ3^(n)取向关系的大尺寸晶粒团簇;退火过程中再结晶形核点增加,晶粒尺寸由468μm减小到146μm。GBE样品耐蚀性高于non-GBE样品,GBE样品自腐蚀电流密度(0.2113 A·m^(-2))小于non-GBE样品(0.8138 A·m^(-2)),且GBE样品的容抗弧半径、阻抗模值|Z|、相位角θ均大于对应non-GBE样品。2种样品表面均发生了点蚀,腐蚀行为可概括为:腐蚀初期,Cl^(-)破坏样品表面局部区域钝化膜形成点蚀坑。随浸泡时间延长,阳极金属附近Ni2+浓度达到饱和或过饱和状态,Ni^(2+)与膜层中结合水反应生成Ni(OH)_(2),部分Ni(OH)_(2)脱水分解为NiO,组成的腐蚀产物膜沉积在样品表面,阻止Cl^(-)穿过腐蚀产物渗透到样品表面,点蚀受到控制。The pure nickel N6 plasma arc weld was subjected to U-shaped bending deformation and heat treatment(grain boundary engineering,GBE).The grain boundary character distribution of non-GBE and GBE samples and its influence on corrosion behavior were studied.The results show that the proportion of low ΣCSL grain boundaries increase to 54.1% by U-shaped bending deformation and subsequent annealing at 900℃ for 10 min,and simultaneously the large-size highly-twinned grain-cluster microstructure is formed.The recrystallization nucleation sites increase and the grain size decreases from 468μm to 146μm during annealing.The corrosion resistance of GBE sample is higher than that of non-GBE sample,the self corrosion current density of GBE sample is less than that of non-GBE sample,and the capacitive arc radius,impedance modulus and phase angle of GBE sample are greater than those of non-GBE samples.Pitting corrosion occurs on the surface of two samples.The passivation film on the surface is destroyed by Cl^(-)in the 3.5% NaCl solution and forms pitting pits at the initial stage,with the prolongation of immersion time,the concentration of Ni^(2+)near the anode metal reaches saturation or supersaturation,the bound water in the corrosion product film reacts with Ni^(2+)forming Ni(OH)_(2),and then the Ni(OH)_(2) are dehydrated and decomposed into NiO.Corrosion products cover the surface of the sample and form a dense corrosion product film,which are composed of NiO and Ni(OH)_(2).The corrosion product film has a protective effect,which prevents Cl^(-)from penetrating through the corrosion products to the sample surface and the pitting is controlled.

关 键 词：纯镍N6焊缝 形变热处理 晶界特征分布 低ΣCSL晶界 腐蚀行为 

分 类 号：TG146.15[一般工业技术—材料科学与工程] TG456.2[金属学及工艺—金属材料] TG156.93[金属学及工艺—金属学]