CuPCr钢显微组织对全浸海水腐蚀行为的影响

为考察CuPCr型耐海水腐蚀钢不同显微组织的腐蚀行为,采用热轧后不同冷却方式分别获得贝氏体和铁素体+珠光体组织,进行模拟海水腐蚀的全浸加速腐蚀实验,并利用失重法测量腐蚀速率,采用SEM,XRD和电化学方法评价钢的腐蚀行为.结果表明:贝氏体组织能够在更短时间内形成比较致密的锈层,其耐蚀性能明显优于铁素体和珠光体组织.碳元素在贝氏体中的均匀分布减少了微电池数量,因而能够降低钢的腐蚀电流密度.     

E690海洋平台用钢力学性能和海洋大气腐蚀行为

以传统的E36海洋平台钢为对比钢,研究三种E690海洋平台钢的组织和力学性能,以及模拟海洋大气环境下的腐蚀行为.通过失重法测得实验钢在不同腐蚀时间下的腐蚀速率,利用扫描电镜和X射线衍射仪观察并测定了锈层的形貌特征和相组成,采用电子背散射衍射技术对实验钢的晶界类型进行分析.结果表明:以贝氏体组织为特征的E690海洋平台钢具有优异的力学性能,-40℃的冲击值超过了200J;晶界类型主要为3°～15°的亚晶界和大于50°的大角度晶界;E690海洋平台钢周浸16 d后的锈层致密且腐蚀速率已趋于稳定,最低腐蚀速率为0.84 mm.a-1,远低于组织为铁素体+珠光体钢的1.4 mm.a-1,实验钢的锈层主要由Fe3O4、α-FeOOH、β-FeOOH及γ-FeOOH四种晶态相和非晶无定形物组成.通过分析得出,热处理工艺和组织构成对材料的初期腐蚀行为有重要影响,而化学成分和锈层自身的致密性对材料后期腐蚀行为起决定作用.     

低碳贝氏体钢在薄液膜下的初期腐蚀

用质量分数3.5%的NaCl溶液作为腐蚀液,滴于低碳铁素体钢、09CuPCrNi钢和低碳贝氏体钢的表面并形成薄液膜,用金相显微镜观测薄液膜下三种钢的初期腐蚀.低碳铁素体钢和09CuPCrNi钢均出现了明显的晶界择优腐蚀,而低碳贝氏体钢没有出现明显的晶界择优腐蚀.钢基体的电化学阻抗谱和极化曲线测量结果显示低碳贝氏体钢具有最高极化电阻和最小腐蚀电流,表明细晶组织的低碳贝氏体钢的初期腐蚀速率低于其他两种钢.     

碳含量和组织类型对低合金钢耐蚀性的影响

研究了不同碳含量和显微组织的低合金钢的耐腐蚀性能和腐蚀行为,并与商业耐候钢09CuPCrNi进行了相应的比较.通过金相显微镜、扫描电镜观察,轧后水冷钢的主体组织为板条状贝氏体,轧后空冷钢为针状铁素体、粒状贝氏体、M/A小岛和少量渗碳体(珠光体)的混合物.用干湿循环加速腐蚀实验对耐蚀性测定结果表明:低碳钢(0.03%C)和轧后水冷的较高碳含量钢(0.1%C)的耐蚀性均明显优于09CuPCrNi;低碳含量钢的组织类型对其耐蚀性影响不大;较高碳含量情况下,单相贝氏体钢的耐蚀性优于由铁素体、渗碳体(珠光体)等构成的复相组织钢;轧后水冷时,不同碳含量的钢耐蚀性差别不大;轧后空冷时,低碳含量钢的耐蚀性优于较高碳含量钢.用扫描电镜对锈层进行观察,可以看出耐蚀性较好的样品在腐蚀后期形成了致密的内锈层.     

奥氏体不锈钢在高温钠中的质量迁移效应研究

本文应用光学显微镜、扫描电镜、X射线衍射仪、俄歇能谱仪分析国产316Ti和321奥氏体不锈钢在650℃流动钠中浸泡4000、5000、8000、10000n后试样表面组成相类型、化学成分和显微组织沿横截面变化及试样表面腐蚀形貌。研究结果表明,国产316Ti和321奥氏体不锈钢在高温流动钠中浸泡后有明显的质量迁移效应。液态钠中所含碳向钢中扩散,钢中Ni、Cr合金元素向流动钠中扩散,引起钢增碳和Ni、Cr元素减少,钢表面的化学成分和组成相及显微组织发生明显变化。其表面组成相为铁素体、奥氏体和M_(23)C_6型碳化物,无σ相·随浸泡时间延长,表面铁素体量增多。表面组织为粒状α+M_(23)C_6+γ;次表层组织为晶界α+M_(23)C_6+γ;心部组织为σ+γ或晶界α+M_(23)C_6+σ+γ,在晶界铁素体层和心部组织之间有一无α、无σ相的碳化物沉淀区(M_(23)C_6+γ)。随浸泡时间继续延长,表层粒状铁素体层深增加,晶界铁素体层和碳化物沉淀区向心部延伸。试样表面产生腐蚀沟槽、晶界腐蚀和腐蚀坑及腐蚀裂纹,浸泡时间再延长,腐蚀加剧。321钢比316Ti钢质量迁移效应明显,腐蚀抗力差。     

三种桥梁耐候钢在模拟海洋大气环境中的耐蚀性能比较

通过室内周期浸润加速腐蚀实验,结合腐蚀形貌观察、物相分析及电化学测试,对三种耐候桥梁钢Q355NHD、Q450NQR1、Q460q在模拟海洋大气环境(3.5%NaCl溶液)下的腐蚀行为进行对比研究。结果表明,三种耐候钢在实验周期内,腐蚀速率均呈先增大后减小的趋势。腐蚀前期,耐蚀性差异主要是由显微组织决定的,以铁素体和珠光体复相组织为主的Q355NHD、Q450NQR1钢腐蚀速率高于以粒状贝氏体为主的Q460q钢。腐蚀后期,微量合金元素在锈层中富集使其致密化,显著提高了三种钢的耐蚀性能。其中Q460q钢锈层最为致密,锈层保护因子α/γ*和电化学阻抗值|Z|最大,在该环境下表现出了最佳的耐蚀性能。     

超低碳贝氏体高强度钢的腐蚀性能研究

为了对超低碳贝氏体高强度钢(ULCB)在海洋环境下的腐蚀性能进行研究,模拟海洋全浸带的环境,通过加速腐蚀试验,对ULCB钢的腐蚀性能和另外两种耐海洋腐蚀钢样进行了耐蚀性能对比.在对SEM,XRD和极化曲线分析后发现,三种耐蚀钢在海水全浸带中的腐蚀主要是点蚀的发生.微观组织是影响钢耐蚀性能的重要因素:铁素体 珠光体组织加速钢的点蚀发生;ULCB钢板条状贝氏体组织细密而均匀,没有明显的晶界,因而钢中微电池的数量大大减少,使其耐蚀性能提高.     

Mn-Cu耐候钢在模拟工业大气环境下的腐蚀行为

利用干湿交替加速腐蚀实验和电化学实验研究了实验钢在模拟工业大气环境下的腐蚀演化行为.结果表明,在腐蚀初期腐蚀速度随循环周期的增加而增大,在后期随循环周期的增加而降低,耐候钢的腐蚀速度与SPA-H钢相当但低于16Mn钢.在腐蚀初期,细晶粒耐候钢比粗晶粒腐蚀速度快,在后期腐蚀速度基本一致.耐候钢锈层分为内外两层,内锈层致密主要由α-FeOOH和少量γ-Fe2O3组成,晶粒尺寸对腐蚀产物的组成影响不大.16Mn钢锈层主要由α-FeOOH,γ-Fe2O3和Fe3O4组成.在腐蚀后期,Cu的作用使耐候钢的耐腐蚀性能优于16Mn钢.电化学实验表明,腐蚀产物促进阴极过程,抑制阳极过程.细晶粒有利于保护性内锈...     

含钼耐候钢的腐蚀性能

通过显微组织观察、周浸加速腐蚀实验、锈层微观分析、锈层交流阻抗特征分析等方法,研究了合金元素钼含量对耐候钢腐蚀性能的影响.合金元素钼可以促进钢中贝氏体组织的形成,促使锈层更加致密,对钢基体具有更好的保护性,有利于提高钢的耐腐蚀性能.随着钢中钼含量的增加,实验钢锈层的腐蚀电位正移,自腐蚀电流密度减小,锈层的阳极溶解反应受到明显阻碍,锈层具有更好的保护性.     

Cu-P-RE耐候钢的耐蚀性能

通过干湿周浸加速腐蚀实验研究了不同稀土含量的耐候钢和对比普碳钢的腐蚀行为及其耐蚀性能.采用失重法测得了各试样的腐蚀率;结果发现,稀土耐候钢的腐蚀率远远低于普碳钢的,不同稀土含量的耐候钢的耐腐蚀性不尽相同.采用电化学交流阻抗技术对带锈钢样的表面锈层结构及电化学反应过程进行了研究,提出在本实验条件下钢电化学腐蚀的等效电路模型,计算出锈层电阻、极化阻抗等表征锈层性能的电化学元件参数值.稀土耐候钢锈层中存在半无限扩散和有限厚度扩散两种过程,有限厚度扩散极化阻抗反映了耐候钢内锈层的保护性能.     

锈蚀钢筋混凝土偏心受压柱承载力试验研究

试验研究了低锈蚀率钢筋对偏心受压构件承载力的影响.将4根钢筋混凝土柱置于湿盐砂中外通直流电加速锈蚀,锈蚀完毕后与3根未锈蚀柱进行偏心受压试验,试验在5 000 kN长柱试验机上进行.另外对锈蚀钢筋进行了拉伸试验.结果表明,偏心距较小时,锈蚀柱截面应变仍符合平截面假定;偏心距相同时锈蚀柱的承载力及刚度比完好柱明显降低.锈蚀钢筋的名义屈服强度、名义极限强度随锈蚀率呈线性降低;随钢筋锈蚀率增大,钢筋的延性降低更快.     

基于概率密度演化理论的锈蚀钢梁时变可靠度分析

为了得到锈蚀钢梁时变可靠度,对9组试件分别开展了加速腐蚀试验和单调拉伸试验.测得了锈蚀深度三维坐标数据和锈蚀钢材名义屈服强度,统计分析了锈蚀深度和名义屈服强度概率模型.建立了锈蚀钢梁功能函数,结合概率密度演化理论得到了锈蚀钢梁时变失效概率和可靠指标,并与蒙特卡洛方法(MCS)计算结果进行了对比.结果表明:钢板表面锈蚀深度和名义屈服强度服从正态分布;随着腐蚀时间增加,锈蚀深度均值和标准差不断增大;随着失重率增加,名义屈服强度均值不断减小而标准差不断增大;概率密度演化方法与MCS计算结果较接近,说明本文提出的方法的有效性;锈蚀深度和强度的随机性对锈蚀钢梁可靠度影响较大.     

碳化物及合金元素对酸液膜中晶粒腐蚀形态的影响

选用10#钢、65#钢和W6Mo5Cr4V2Al钢为实验材料,利用光学显微镜、扫描电镜和电子探针对其在酸性环境中腐蚀后的晶粒微观形貌和合金元素的分布进行观察分析,考察合金元素和碳化物的存在形式对晶粒腐蚀形态的影响.结果表明,晶粒的腐蚀形貌与碳化物分布有关,钢中碳元素以固溶形式存在或钢中添加Cr,Al元素,可显著提高钢的耐酸蚀性;在以电化学腐蚀为主的酸性环境中,组织中各相电极电位的高低才是晶粒是否易被腐蚀的本质;晶界是否易被腐蚀也主要与晶界处物相的电极电位高低有关.     

X65管线钢抗H_2S腐蚀的试验研究

研究了不同显微组织管线钢抗H2S腐蚀的行为·结果表明,酒钢生产的X65管线钢,当显微组织是以针状铁素体为主的混合型组织时,管线钢具有优良的抗H2S腐蚀性能·经硫化氢腐蚀试验后,除出现程度不等的氢鼓泡外,试样断面上基本没有产生裂纹·氢鼓泡是由于钢中夹杂物处吸收由腐蚀而产生的氢所引起的·当钢表面上因腐蚀而释放出原子态氢后,由于硫化氢的催化作用,促进原子氢向钢中扩散,并在夹杂物与基体的界面上聚集形成分子氢·随着过程的进行,产生很高的压力,从而形成鼓泡·     

Effect of the frequency of high-angle grain boundaries on the corrosion performance of 5wt%Cr steel in a CO<Subscript>2</Subscript> aqueous environment

The corrosion behavior of 5wt%Cr steel tempered at different temperatures was investigated by immersion testing and electrochemical testing in a CO₂ aqueous environment. When the tempering temperature exceeded 500℃, the corrosion rate increased. The corrosion layers consisted of Cr-rich compounds, which affected the corrosion behaviors of the steels immersed in the corrosive solution. The results of electrochemical experiments demonstrated that 5wt%Cr steels with different microstructures exhibited pre-passivation characteristics that decreased their corrosion rate. Analysis by electron back-scattered diffraction showed that the frequency of high-angle grain boundaries (HAGBs) and the corrosion rate were well-correlated in specimens tempered at different temperatures. The corrosion rate increased with increasing HAGB frequency.     

高强度马氏体钢显微组织对腐蚀行为影响的研究进展

The high strength martensite steels are widely used in aerospace, ocean engineering, etc., due to their high strength, good ductility and acceptable corrosion resistance. This paper provides a review for the influence of microstructure on corrosion behavior of high strength martensite steels. Pitting is the most common corrosion type of high strength stainless steels, which always occurs at weak area of passive film such as inclusions, carbide/intermetallic interfaces. Meanwhile, the chromium carbide precipitations in the martensitic lath/prior austenite boundaries always result in intergranular corrosion. The precipitation, dislocation and grain/lath boundary are also used as crack nucleation and hydrogen traps, leading to hydrogen embrittlement and stress corrosion cracking for high strength martensite steels. Yet, the retained/reversed austenite has beneficial effects on the corrosion resistance and could reduce the sensitivity of stress corrosion cracking for high strength martensite steels. Finally, the corrosion mechanisms of additive manufacturing high strength steels and the ideas for designing new high strength martensite steel are explored.     

Incubation and development of corrosion in microstructures of low alloy steels under a thin liquid film of NaCl aqueous solution

Electrochemical measurement, optical microscopy, and scanning electron microscopy were employed to investigate the corrosion behavior of some low alloy steels. The steels were held under a thin liquid film of 0.5wt% NaCl aqueous solution. It is found that the steels with the same chemical composition but different microstructures exhibit obviously different corrosion behaviors. However, the corrosion behavior of the steels with different compositions but the same microstructures may be similar in the present investigation. The corrosion rate of bainite is slower than that of ferrite and pearlite. The corrosion products of bainite are uniform and fine. The size of carbon-rich phases produces a great impact on the corrosion of the steels, whether in the initial stage or in the long term. It is easy to induce large pitting for carbon-rich phases with large size, which damages the compactness of the rust layer.     

Effect of microstructure on corrosion behavior of high strength martensite steel——A literature review

The high strength martensite steels are widely used in aerospace, ocean engineering, etc., due to their high strength, good ductility and acceptable corrosion resistance. This paper provides a review for the influence of microstructure on corrosion behavior of high strength martensite steels. Pitting is the most common corrosion type of high strength stainless steels, which always occurs at weak area of passive film such as inclusions, carbide/intermetallic interfaces. Meanwhile, the chromium carbide precipitations in the martensitic lath/prior austenite boundaries always result in intergranular corrosion. The precipitation, dislocation and grain/lath boundary are also used as crack nucleation and hydrogen traps, leading to hydrogen embrittlement and stress corrosion cracking for high strength martensite steels. Yet, the retained/reversed austenite has beneficial effects on the corrosion resistance and could reduce the sensitivity of stress corrosion cracking for high strength martensite steels. Finally, the corrosion mechanisms of additive manufacturing high strength steels and the ideas for designing new high strength martensite steel are explored.     

拉伸疲劳对钢筋锈蚀临界氯离子浓度的影响

采用不同应力水平和次数对Q235钢筋进行拉伸疲劳试验,在饱和Ca(OH)2模拟液中,采用自腐蚀电位法和电化学阻抗谱法测定钢筋锈蚀的临界氯离子浓度,同时通过扫描电镜观察拉伸疲劳作用引起的钢筋显微结构变化。结果表明:在拉伸疲劳作用下,钢筋锈蚀的临界氯离子浓度随着拉伸疲劳应力水平的增大和疲劳次数的增加而减小;拉伸疲劳会使钢筋晶粒细化,晶界、相界增多,并且随着拉伸疲劳应力水平的增大和疲劳次数的增加,这种变化就越明显;钢筋晶粒的细化以及晶界的增多会引发短路扩散,降低钢筋锈蚀的临界氯离子浓度。