表面状态对核级316LN不锈钢电化学腐蚀行为的影响

表征了打磨态和机械抛光态316LN不锈钢表面的粗糙度、表面残余应变和表面电子功函数的分布,并研究了打磨态和机械抛光态样品在硼酸盐溶液中电化学腐蚀行为的差异.与机械抛光态316LN不锈钢相比,打磨处理后样品表面较为粗糙,且表面的微观残余应变较大,近表面产生约50 μm的加工硬化层.表面粗糙度和微观应变的增加引起打磨态表面电化学活性的增大,从而促进316LN不锈钢在硼酸盐溶液中腐蚀.机械抛光处理降低了表面钝化膜的载流子密度(供体和受体),并增大了钝化膜的阻抗,提高了钝化膜的致密性和保护性,能够有效抑制金属的进一步腐蚀.     

AISI304不锈钢在冷加工过程中的微观组织变化

在不同温度下对AISI304不锈钢进行不同方式、不同程度冷加工,用铁素体测量仪测定马氏体相变量,研究了冷加工与马氏体相变的关系;将AISI304不锈钢在低温(液氮,-70#℃)条件下进行不同程度拉伸,采用透射电镜观测位错分布,研究了冷加工与位错密度的关系.结果表明:冷加工在一定条件下可以产生形变诱发马氏体,其含量随冷加工变形量的增大而增加;同时,冷加工导致AISI304不锈钢中金属晶粒拉长,其位错密度随冷加工变形量的增加而增大.     

铬硅锰氧化物夹杂诱发316L不锈钢点蚀行为研究

采用原位分析法及化学浸泡法并结合扫描电镜和能谱仪分析,对316L不锈钢中三种典型铬硅锰氧化物夹杂诱发不锈钢点蚀行为进行分析,并探究其腐蚀机理。结果表明,在质量分数为6%的FeCl_3溶液浸泡腐蚀下,316L不锈钢中三种典型铬硅锰氧化物夹杂耐蚀性从大到小的顺序依次为:单一贫铬相(w(Cr)15%)铬硅锰氧化物夹杂单一富铬相(w(Cr)15%)铬硅锰氧化物夹杂MnS与铬硅锰氧化物复合相夹杂;单一相夹杂诱发的点蚀是以小孔腐蚀的形式始发于夹杂物内部,其部位靠近夹杂与基体界面处;而对于MnS与铬硅锰氧化物复合相夹杂诱发的点蚀,首先是夹杂外层包裹的硫化物在较短时间内发生溶解,使得夹杂与基体交界处产生微缝隙,进而导致不锈钢点蚀的产生;铬硅锰氧化物夹杂中铬含量过高(w(Cr)15%)或过低(w(Cr)6%),均会降低不锈钢的抗腐蚀性能。     

304不锈钢在西沙海洋大气环境中的腐蚀行为

采用扫描电镜、能谱、电化学阻抗谱和拉曼光谱等分析测试手段,研究了西沙群岛苛刻海洋大气环境下,经过不同时间暴露后304不锈钢的腐蚀行为和机理.304不锈钢在西沙大气暴露后的腐蚀类型主要是以局部腐蚀的点蚀为主,腐蚀产物主要由β-FeOOH、γ-Fe₂O₃和Fe₃O₄组成.随暴露时间的延长,不锈钢表面钝化膜的稳定性变差,点蚀数目增加、点蚀坑深度增大日.表面腐蚀产物覆盖率也逐渐增多.与其他部位相比,点蚀更容易在表面划痕处产生.提高表面加工精度,有助于提高其耐腐蚀性能.     

409L和430铁素体不锈钢耐局部腐蚀性能

采用电化学测试技术与化学浸泡实验相结合,对比研究了409L和430铁素体不锈钢热轧板材耐点蚀和耐晶间腐蚀的能力.结果表明:409L不锈钢的击穿电位与保护电位的差小、钝化膜的修复能力较强,表现为小尺度的浅点蚀孔;430不锈钢的击穿电位较高,耐点蚀能力高于409L不锈钢,但430不锈钢热轧态的条带组织有明显的腐蚀微电池效应,表现为比较严重的全面腐蚀;409L不锈钢含Cr量低,且其热轧态未经过稳定化处理,使得409L不锈钢耐晶间腐蚀能力劣于430不锈钢.经微观分析:409L不锈钢为沿着基体等轴晶界的典型晶间腐蚀形貌特征,而430不锈钢在轧向碳化物(M23C6)与基体的相界面上呈现分层腐蚀痕迹.     

316L不锈钢在含氯高温醋酸溶液中的自钝化行为

研究了316L不锈钢在85 ℃,含0.2% KCl的60%醋酸溶液中的自钝化行为. 通过测试试样的恒电流阴极极化曲线,以及恒电流阴极极化后开路电位随时间的变化曲线,提出了316L不锈钢钝化膜的结构模型. 该模型认为316L不锈钢钝化膜由三层构成:最外层主要是由Fe的氧化物以及少量Cr的氧化物组成;第二层主要是Cr的氧化物,含有少量Fe,Mo和Ni的氧化物;最底层主要是Mo,Ni的氧化物和少量的Fe原子. 研究发现: 316L不锈钢在实验醋酸溶液中,经10 mA阴极电流极化15 min后钝化膜生长参数γ最大,而经0.45 mA阴极电流极化30 min后钝化膜生长参数γ最小;316L不锈钢在实验醋酸溶液中,经10 mA阴极电流极化30 min后,自钝化电位最小,而经1 mA阴极电流极化15 min后,自钝化电位最大. 钝化膜结构模型能很好地解释316L不锈钢在实验醋酸溶液中的上述电化学行为.     

Damage mechanism at different transpassive potentials of solution-annealed 316 and 316l stainless steels

Electrochemical impedance spectroscopy (EIS), anodic polarization and scanning electron microscopy techniques were used to investigate the damage mechanism in the transpassive potential region of AISI 316 and AISI 316L solution-annealed stainless steels (SS) with different degrees of sensitization. Depending on the DC potential applied during EIS tests, the AC responses in the transpassive region included three different regions:the first one associated with anodic dissolution of the passive layer, the second one contributed to the dissolution at the area near grain boundaries, and the last one attributed to pitting corrosion. In addition, the fitting results to experimental data showed that as the DC bias during the EIS test increases the charge transfer resistance (R_ct) decreases. Moreover, the R_ct values decreased as the sensitization temperature increases but the AISI 316L SS samples exhibited a higher resistance to intergranular corrosion than 316 SS samples.     

304不锈钢在模拟压水堆一回路水中高温电化学腐蚀行为

通过模拟压水堆一回路水环境,研究了氯离子浓度和溶解氧对304不锈钢高温电化学腐蚀行为的影响.动电位极化曲线结果表明,氯离子浓度主要影响高电位下的二次钝化效应,低电位下影响效果不明显,结合X射线光电子能谱对氧化膜元素成分的分析发现二次钝化效应与氧化膜中Fe/Cr元素含量比密切相关.电化学阻抗谱和扫描电镜结果表明,随着氯离子浓度增加,氧化膜阻抗逐渐降低,表面外层氧化物颗粒和间隙逐渐增大,耐腐蚀性能降低.随着溶解氧含量的升高,304自腐蚀电位逐渐升高,钝化电流密度降低,钝化区间缩小,表面氧化膜阻抗逐渐增加.     

Effects of chitosan inhibitor on the electrochemical corrosion behavior of 2205 duplex stainless steel

The effects of chitosan inhibitor on the corrosion behavior of 2205 duplex stainless steel were studied by electrochemical measurements, immersion tests, and stereology microscopy. The influences of immersion time, temperature, and chitosan concentration on the corrosion inhibition performance of chitosan were investigated. The optimum parameters of water-soluble chitosan on the corrosion inhibition performance of 2205 duplex stainless steel were also determined. The water-soluble chitosan showed excellent corrosion inhibition performance on the 2205 duplex stainless steel. Polarization curves demonstrated that chitosan acted as a mixed-type inhibitor. When the stainless steel specimen was immersed in the 0.2 g/L chitosan solution for 4 h, a dense and uniform adsorption film covered the sample surface and the inhibition efficiency (IE) reached its maximum value. Moreover, temperature was found to strongly influence the corrosion inhibition of chitosan; the inhibition efficiency gradually decreased with increasing temperature. The 2205 duplex stainless steel specimen immersed in 0.4 g/L water-soluble chitosan at 30℃ displayed the best corrosion inhibition among the investigated specimens. Moreover, chitosan decreased the corrosion rate of the 2205 duplex stainless steel in an FeCl₃ solution.     

304 L不锈钢焊缝在混凝土模拟孔隙液中的点蚀行为

采用动电位极化曲线、电化学阻抗谱、Mott-Schottky曲线等电化学方法研究了以308 L为焊丝的304 L不锈钢焊接接头在不同氯离子含量的混凝土模拟孔隙液中腐蚀行为和电化学规律。随Cl-增加,304 L不锈钢焊接接头的三个区域(母材、焊缝和热影响区)在混凝土模拟孔隙液中的自腐蚀电位、点蚀电位及电荷转移电阻降低,钝化膜中载流子密度和焊接接头的点蚀坑数量增加。在同浓度的腐蚀溶液中,308 L的焊缝区域耐蚀性最佳,热影响区次之,304 L基体表现出低的电荷转移电阻和高的掺杂浓度使得母材的耐蚀性最差。     

Pitting corrosion and crevice corrosion behaviors of high nitrogen austenitic stainless steels

Pitting corrosion and crevice corrosion behaviors of high nitrogen austenitic stainless steels (HNSS) were investigated by electrochemical and immersion testing methods in chloride solution, respectively. The chemical constitution and composition in the depth of passive films formed on HNSS were analyzed by X-ray photoelectron spectrum (XPS). HNSS has excellent pitting and crevice corrosion resistance compared to 316L stainless steel. With increasing the nitrogen content in steels, pitting potentials and critical pitting temperature (CPT) increase, and the maximum, average pit depths and average weight loss decrease. The CPT of HNSS is correlated with the alloying element content through the measure of alloying for resistance to corrosion (MARC). The MARC can be expressed as an equation of CPT=2.55MARC-29. XPS results show that HNSS exhibiting excellent corrosion resistance is attributed to the enrichment of nitrogen on the surface of passive films, which forms ammonium ions increasing the local pH value and facilitating repassivation, and the synergistic effects of molybdenum and nitrogen.     

温度和Cl-质量分数对304不锈钢耐点蚀性能的影响

采用线性极化技术和动电位循环伏安法2种电化学测试技术,研究温度和氯离子的质量分数对304不锈钢耐点蚀性能的影响,从而得到二者对点蚀的影响规律.结果表明:随着温度的升高和氯离子质量分数的增大,304不锈钢点蚀坑的孔径和数量均变大,电流密度也变大,击穿电位Eb负移,钝化区变窄,因此二者的升高使钝化膜的修复能力变差,点蚀敏感性增加.同时得到Eb与温度、Cl-质量分数都呈线性关系:温度每升高10℃,Eb向负方向移动约30 mV.Cl-质量分数每增加0.5%,Eb向负方向约移动10 mV.Eb-Ep随着温度或Cl-质量分数的升高而变大,但其与温度或Cl-质量分数并不成线性关系.     

Microstructures and mechanical properties of dissimilar Nd:YAG laser weldments of AISI4340 and AISI316L steels

This paper presents studies on the microstructure and mechanical properties of AISI 316L stainless steel and AISI 4340 low-alloy steel joints formed by the Nd:YAG laser welding process. The weld microstructures and heat affected zones (HAZs) were investigated. Austenitic microstructures were observed in all of the samples. The sizes of the HAZs changed when the heat input was varied, and the 316L sides exhibited a larger HAZ. The cooling rates were calculated by measuring the solidification dendrite arm spacing. It is shown that high cooling rates lead to an austenitic microstructure. Tensile tests were carried out, and the results revealed the tensile properties of both the base metals and the weldments. The hardness test results agreed well with the tensile test results.     

304和316L不锈钢的高温电化学腐蚀行为

通过模拟压水堆一回路水环境,研究了溶液温度和溶氧量(DO)对304和316L不锈钢高温电化学腐蚀行为的影响.结果表明:随着溶液温度升高,在304和316L不锈钢表面所形成的氧化膜的保护性能降低;随着DO升高,304和316L不锈钢的自腐蚀电位升高,自腐蚀电流密度降低,钝化区缩小;304和316L不锈钢表面形成了双层氧化膜,外层氧化膜颗粒尺寸和颗粒间隙随着温度的升高而增大,随着DO增加而减小;在所用实验条件下,316L不锈钢表现出比304更优异的抗腐蚀性能.     

钼对铸造双相不锈钢组织及耐点蚀性能的影响

研究了钼含量对铸造双相不锈钢显微组织及耐点蚀性能的影响。探讨了耐点蚀性能、含钼量、组织彼此之间的关系。结果表明：随钼含量增加，钢中ｒ相含量逐渐减少。当钼含量超过一定量后，组织的均匀程度降低，并存在Ｘ相。随钼含量的增加，钢的耐点蚀性能逐渐提高；当钼量超过一定量后，耐点蚀性能明显降低，耐点蚀性能与组织的均匀程度及Ｘ相的存在有关。     

合金元素对316 LN 不锈钢的力学性能和点蚀性能的影响

研究了N、Cr、Mo和Ni四种合金元素含量的变化对核电主管道用固溶态316LN不锈钢的晶粒尺寸以及常规力学性能和点蚀性能的影响.随着N含量的升高,316LN的晶粒明显细化,其在固溶处理过程中晶粒长大趋势也减小. N含量的升高可改善316LN的力学性能和耐点蚀性能,但是当N质量分数达到0.20%时,其耐点蚀性能又开始变差.晶粒细化对316LN强度的影响远小于N含量对316LN强度的影响. Cr及Ni含量对316LN的晶粒尺寸及抗拉强度、屈服强度等力学性能影响不大;Cr含量增加可轻微改善316LN的抗点蚀能力,Ni元素对316LN的耐点蚀性能影响不大,但可增大钝态的腐蚀速度从而不利于钝化膜的稳定.随Mo含量增加,316LN的晶粒尺寸略有减小,强度增大,延伸率显著降低,耐点蚀能力改善.     

Preparation of high-performance ultrafine-grained AISI 304L stainless steel under high temperature and pressure

Bulk ultra-fine grained (UFG) AISI 304L stainless steel with excellent mechanical properties was prepared by a high-temperature and high-pressure (HTHP) method using nanocrystalline AISI 304L stainless steel powders obtained from ball milling. Samples were sintered in high-pressure conditions using the highest martensite content of AISI 304L stainless steel powders milled for 25 h. Analyses of phase composition and grain size were accomplished by X-ray diffraction and Rietveld refinement. By comparing the reverse martensite transformation under vacuum and HTHP treat, we consider that pressure can effectively promote the change in the process of transformation. Compared with the solid-solution-treated 304L, the hardness and yield strength of the samples sintered under HTHP are considerably higher. This method of preparation of UFG bulk stainless steel may be widely popularised and used to obtain UFG metallic materials with good comprehensive performance.     

一种奥氏体不锈钢的空泡腐蚀行为

采用一种新型的奥氏体不锈钢作为耐空泡腐蚀涂层,先表面堆焊,然后进行TIG（钨极惰性气体保护焊）表面重熔改性加工．根据ASTM G32／92标准,空泡腐蚀由超声波振动设备完成．利用X射线衍射仪和扫描电镜（SEM）对试样的空泡腐蚀行为进行了跟踪观察,并对试样的空泡腐蚀率进行了测定．结果表明：在空泡腐蚀过程中,先后发生了相变和马氏体片层的扭曲断裂．空泡冲击能诱发奥氏体到马氏体的相变,并被其吸收;当相变达到饱和点时,马氏体片层开始吸收冲击能,同时逐渐发生扭曲和断裂,最终马氏体片层断裂产生的碎片大量剥落,该材料的空泡腐蚀潜伏期结束．     

Properties of passive film formed on 316L/2205 stainless steel by Mott-Schottky theory and constant current polarization method

Semiconductor properties of the passive films formed on 316L and 2205 stainless steel were studied by Electrochemical Impedance Spectroscopy(EIS) in the high-temperature acetic acid.The results showed that the corrosion resistance of 2205 was higher than that of 316L,and the passive films formed on 316L and 2205 stainless steel showed p-type and n-type semiconductor behavior,respectively.Destruction and self-repairing of passive films were studied by using the constant current polarization method.The result...     

pH值对高温高压水中304L不锈钢应力腐蚀开裂的影响

在高温高压水环境中,采用慢应变速率拉伸试验方法,研究了不同pH值对304L不锈钢应力腐蚀开裂行为的影响规律,并通过扫描电镜对试样断口形貌进行观察与分析.结果表明:在300℃时,304L不锈钢在弱酸性和弱碱性溶液中的应力腐蚀开裂敏感性较大,且酸性越强,敏感性越大.在中性溶液中,304L不锈钢的强度和塑性损失较小,应力腐蚀敏感性较小,断口分析与之吻合.