Q235焊缝表面镍基合金熔覆层在NaCl溶液中的腐蚀行为  

Corrosion Behavior of Nickel-based Alloy Cladding Layer on Q235 Weld in Na Cl Solution

作　　者：柴廷玺 晏丽琴 徐宏彤 蒋锴 刘鹏 CHAI Ting-xi;YAN Li-qin;XU Hong-tong;JIANG Kai;LIU Peng(School of Bailie Mechanical Engineering,Lanzhou City University,Lanzhou 730070,China;School of Electronic 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,兰州730070 [2]兰州城市学院电子工程学院,兰州730070

出　　处：《表面技术》2023年第3期276-286,共11页Surface Technology

基　　金：甘肃省自然科学基金(20JR10RA281);甘肃省高等学校科研项目(2020A-128)。

摘　　要：目的采用激光、等离子熔覆技术在低碳钢焊缝表面制备镍基耐腐蚀涂层,提高钢管焊缝表面的耐蚀性能。方法通过浸泡腐蚀、动电位极化法、交流阻抗法,研究不同试样在质量分数为3.5%的NaCl溶液中的腐蚀行为。利用OM、SEM、EDS和XPS分析腐蚀试样表面、截面的微观组织和腐蚀产物成分。结果采用激光、等离子熔覆技术均可制得成形良好、表面光滑、无宏观裂纹的涂层,且表现出良好的抗点蚀能力;等离子熔覆层晶粒相较于激光熔覆层晶粒更均匀、细小,析出的碳化物(Cr_(23)C_(6)、Cr_(7)C_(3))、硼化物(CrB)等硬质点提高了涂层的硬度,对于抗蚀性有着积极的作用。试样的耐蚀性排序为等离子熔覆层>激光熔覆层>基体。浸泡失重腐蚀实验表明,基体、激光熔覆层、等离子熔覆层的腐蚀速率分别为0.1829、0.1256、0.1027 g/(m^(2)·h)。从极化曲线看出,激光熔覆层(-0.5034 V)、等离子熔覆层(-0.5466 V)的自腐蚀电位相较于基体(-0.8584 V)发生了正移。基体、激光熔覆层、等离子熔覆层的自腐蚀电流密度分别为0.0749、0.0358、0.0033 A/m^(2)。从电化学阻抗谱看出,等离子熔覆层的容抗弧半径最大,激光熔覆层的次之,基体的最小。涂层在腐蚀初期以金属阳极溶解为主,Cl^(-)破坏了涂层表面的钝化膜,导致表面出现点蚀坑,点蚀进一步加剧,腐蚀产物膜层中的结合水与Ni^(2+)、Cr^(3+)反应,生成了Cr(OH)_(3)、Ni(OH)_(2),Cr(OH)_(3)、Ni(OH)_(2),进一步脱水后,分解成Cr_(2)O_(3)、CrO_(3)、NiO,形成由氧化物、氢氧化物组成的腐蚀产物膜,阻碍了溶液Cl^(-)穿过腐蚀产物渗透到涂层表面,提高了涂层的耐蚀性。结论涂层具有优良耐蚀性的本质原因是腐蚀产物膜对腐蚀介质起到了物理阻隔作用。The work aims to prepare Ni60 nickel based corrosion resistant coatings on the weld surface of Q235 low carbon steel by laser cladding technology and plasma cladding technology.Corrosion resistance of the sample in 3.5%NaCl solution was tested by weight-loss corrosion and electrochemical corrosion tests.The microstructure morphology,chemical composition,coating phase and electronic structure of corrosion product film on the surface of the corrosion sample were tested by OM,SEM,EDS,XRD and XPS,so as to reveal the corrosion resistance mechanism of Ni60 corrosion-resistant coating.The results showed that the Ni60 corrosion-resistant coating with good formation,low porosity,dense and smooth and no macro crack can be prepared on the surface of Q235 weld by laser and plasma cladding technology.The grain size of plasma cladding coating was smaller than that of laser cladding coating.This was because the laser cladding coating was a multipass lap coating,and the cladding area was heated twice during the cladding process,which lead to the temperature rise of the previous cladding coating and grain growth.Microstructure near the fusion line in the laser cladding coating was plane crystal,and the cladding layer was columnar crystal.The phase of laser cladding coating was composed of γ-(Ni,Fe),Fe_(3)Ni_(2),CrB,FeNi_(3),Cr_(23)C_(6),Cr_(7)C_(3).The microstructure of plasma cladding coating from fusion line to cladding layer was planar crystal,equiaxed crystal,equiaxed crystal and dendrite mixed zone.The phase of plasma cladding coating was γ-(Ni,Fe),FeB,CrB and FeNi_(3).The precipitation of carbides,borides and solution strengthened austenitic matrix in the coating improved the hardness of the coating,which had a positive effect on improving the pitting resistance of the coating.Corrosion rates of matrix,laser cladding coating and plasma cladding coating were 0.1829,0.1256 and 0.1027 g/(m^(2)·h)respectively.From the polarization curve,it can be seen that the self-corrosion potential of laser cladding layer(-0.5034 V)and pl

关 键 词：Q235焊缝 激光熔覆层 等离子熔覆层 NI60涂层 腐蚀行为 

分 类 号：TG174.4[金属学及工艺—金属表面处理]