Fabrication of high nitrogen austenitic stainless steels with excellent mechanical and pitting corrosion properties

A series of high nitrogen austenitic stainless steels were successfully developed with a pressurized electroslag remelting furnace. Nitride additives and deoxidizer were packed into the stainless steel pipes, and then the stainless steel pipes were welded on the surface of an electrode with low nitrogen content to prepare a compound electrode. Using Si₃N₄ as a nitrogen alloying source, the silicon contents in the ingots were prone to be out of the specification range, the electric current fluctuated greatly and the surface qualities of the ingots were poor. The surface qualities of the ingots were improved with FeCrN as a nitrogen alloying source. The sound and compact macrostructure ingot with the maximum nitrogen content of 1.21wt% can be obtained. The 18Cr18Mn2Mo0.9N high nitrogen austenitic stainless steel exhibits high strength and good ductility at room temperature. The steel shows typical ductile-brittle transition behavior and excellent pitting corrosion resistance properties.     

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.     

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.     

硫化碱蒸发设备新材料耐腐蚀性能的研究

本文通过一系列金属均匀腐蚀试验,论证了耐晶间腐蚀、点腐蚀、缝隙腐蚀、应力腐蚀开裂性能,选定了超纯高铬铁素体不绣钢EB30Cr-2Mo作为硫化碱蒸发器的新型耐腐蚀材料,从而为改变我国目前落后的硫化碱蒸发工艺提供了可靠条件。     

工业纯钛和00Cr25Ni22Mo2不锈钢的缝隙腐蚀

采用在不同温度及不同介质中化学浸泡法和电化学测试方法,对工业纯钛和００Ｃｒ２５Ｎｉ２２Ｍｏ２不锈钢之间产生的缝隙腐蚀行为进行研究。结果表明：在有缝隙的情况下,００Ｃｒ２５Ｎｉ２２Ｍｏ２不锈钢在氧化性介质中的缝隙腐蚀速率明显大于在还原性介质中的缝隙腐蚀速率;工业纯钛则恰恰相反。温度对缝隙腐蚀有较大影响,随温度升高,００Ｃｒ２５Ｎｉ２２Ｍｏ２不锈钢的缝隙腐蚀加重并伴有点蚀产生;工业纯钛在１（ｍｏｌ·Ｌ－１）Ｈ２ＳＯ４溶液中,随温度升高缝隙腐蚀速率增加明显,高于８３℃伴有点蚀产生。电化学实验表明,存在缝隙情况下,在２５℃１（ｍｏｌ·Ｌ－１）Ｈ２ＳＯ４溶液中,工业纯钛的维钝电流密度小于００Ｃｒ２５Ｎｉ２２Ｍｏ２不锈钢的维钝电流密度,工业纯钛的击穿电位比００Ｃｒ２５Ｎｉ２２Ｍｏ２不锈钢的高约８００ｍＶ;而在８５℃,工业纯钛的维钝电流密度大于００Ｃｒ２５Ｎｉ２２Ｍｏ２不锈钢的,而且工业纯钛的击穿电位下降明显,两者的击穿电位十分接近     

Intergranular corrosion behavior of high nitrogen austenitic stainless steel

The intergranular corrosion (IGC) behavior of high nitrogen austenitic stainless steel (HNSS) sensitization treated at 650-950℃ was investigated by the double loop electrochemical potentiodynamic reactivation (DL-EPR) method. The effects of the electrolytes, scan rate, sensitizing temperature on the susceptibility to IGC of HNSS were examined. The results show that the addi-tion of NaCl is an effective way to improve the formation of the cracking of a passive film in chromium-depleted zones during the reactivation scan. Decreasing the scan rate exhibits an obvious effect on the breakdown of the passive film. A solution with 2 mol/L H₂SO₄+1 mol/L NaCl+0.01 mol/L KSCN is suitable to check the susceptibility to IGC of HNSS at a sensitizing temperature of 650-950℃ at a suitable scan rate of 1.667 mV/s. Chromium depletion of HNSS is attributed to the precipitation of Cr₂N which results in the susceptibility to IGC. The synergistic effect of Mo and N is suggested to play an important role in stabilizing the passive film to prevent the attack of IGC.     

Effects of chloride ion concentration and pH values on the corrosion behavior of Cr12Ni3Co12Mo4W ultra-high-strength martensitic stainless steel

The effects of Cl- ion concentration and pH values on the corrosion behavior of Cr12Ni3Co12Mo4W ultra-high-strength martensitic stainless steel (UHSMSS) were investigated by a series of electrochemical tests combined with observations by stereology microscopy and scanning electron microscopy. A critical Cl- ion concentration was found to exist (approximately 0.1wt%), above which pitting occurred. The pitting potential decreased with increasing Cl- ion concentration. A UHSMSS specimen tempered at 600°C exhibited a better pitting corrosion resistance than the one tempered at 400°C. The corrosion current density and passive current density of the UHSMSS tempered at 600°C decreased with increasing pH values of the corrosion solution. The pits developed a shallower dish geometry with increasing polarization potential. A lacy cover on the pits of the UHSMSS tempered at 400°C accelerated pitting, whereas corrosion products deposited in the pits of the UHSMSS tempered at 600°C hindered pitting.     

氮在奥氏体不锈钢中的作用

论述了在奥氏体不锈钢中适量加氮可以提高奥氏体组织稳定性、力学性能和部分抗腐蚀能力；表面渗氮技术，如等离子体源渗氮，使得奥氏体不锈钢的力学性能，抗腐蚀性能更加优异，同时指出有关氮化物析出的原因、条件以及对力学性能、抗腐蚀性能的一些负面影响，研究结果表明，由于氮价格十分低廉，可以部分甚至全部取代镍以及合金化展出现的优良性能，氮已经成为奥氏体不锈钢重要的合金化元素，氮合金化的研究日益受到各方面的关注。     

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。     

温度对13Cr不锈钢在高 CO2 分压环境中腐蚀行为的影响

通过高温高压电化学测试,获得不同实验温度下13Cr不锈钢的循环伏安曲线、交流阻抗谱和Mott-Schottky曲线,结合ZSIMPWIN软件和扫描电子显微镜分析,研究高温高CO2 分压环境下,温度对13Cr不锈钢腐蚀电化学行为的影响. 在高温高CO2 分压环境下,随温度升高,13Cr不锈钢发生腐蚀的倾向增加,表面钝化膜稳定性下降,点蚀敏感度增加.     

高温渗氮工艺对无镍不锈钢模拟体液环境下耐蚀性的影响

文章采用高温渗氮工艺得到高氮无镍不锈钢,以提高医用不锈钢的安全性和耐蚀性。实验结果表明:渗氮层氮质量分数可达1.0%,与原材料相比氮质量分数增加了2倍;在0.9%NaCl生理盐水和模拟血浆溶液中具有优异的耐蚀性,在加热温度1 200℃、氮气压力0.3MPa、保温时间24h条件下得到的高氮奥氏体不锈钢在0.9%NaCl生理盐水中的点蚀电位约1 200mV,大大高于渗氮前(约320mV)的水平。     

Comparative study on the corrosion behavior of X52, 3Cr,and 13Cr steel in an O2–H2O–CO2 system: products,reaction kinetics,and pitting sensitivity

The corrosionbehaviors of X52, 3Cr low-alloy steel, and 13Cr stainless steel were investigated inanO2–H2O–CO2 environment at varioustemperaturesand O2–CO2partial-pressure ratios. The results showed thatthe corrosion rates of X52, 3Cr, and 13Cr steels in-creased with increasing temperature. The corrosion ratesslowly increased at temperaturesless than100℃ and increased sharply when the temperature exceeded100℃. In the absence of O2, X52, 3Cr, and 13Cr exhibited uniform corrosion morphology and FeCO3 was the main corrosion product. When O2 was introduced into the system, various forms of Fe2O3 appeared on the surface of the samples. The Cr content strongly influenced the corrosion resistance. The 3Cr steel with a low Cr content was more sensitive to pitting than the X52 or 13Cr steel. Thus, pitting occurred on the surface of 3Cr when 1.25 MPa of O2 was added; this phenomenon is related to the non-uniform distribution of Cr in 3Cr.     

Ni-Cr-Mo-Cu-Mx合金耐晶间腐蚀及点蚀性能

向镍基耐蚀合金中添加Ti、Fe元素,采用手工电弧炉熔炼制备新型Ni-Cr-Mo-Cu-Mx耐蚀合金,用化学浸泡法、电化学法(极化曲线法、循环伏安法)对其耐晶间腐蚀和耐点蚀能力进行研究.结果表明:在Ni-Cr-Mo-Cu合金中加入Ti元素可以增强其耐晶间腐蚀能力,减弱其耐点蚀的能力;加入Fe元素会降低Ni-Cr-Mo-Cu合金耐晶间腐蚀的能力,但提高该合金耐点蚀的能力;实验合金晶间腐蚀与点蚀的电化学行为和特征与其浸泡腐蚀的结果是吻合的.     

冷凝液硫含量对SUS444铁素体不锈钢腐蚀行为的影响

利用冷凝液浸蚀-高温氧化循环腐蚀法模拟汽车排气系统内部服役环境,借助失重分析、腐蚀形貌观察及腐蚀产物分析,研究了SUS444不锈钢在不同硫含量的冷凝液中的腐蚀行为。结果表明,随着腐蚀循环次数的增加,不锈钢表面不断沉积的FeSO_4·7H_2O、Fe(NH_4)(SO_4)_2及Fe_4(SO_4)_5(OH)_2·18H_2O等硫酸盐物质加速了不锈钢的腐蚀进程,其点蚀深度及腐蚀速率均随冷凝液中硫含量的升高而增加。     

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.     

Pitting corrosion resistance of a novel duplex alloy steel in alkali-activated slag extract in the presence of chloride ions

In this study, two types of reinforcing steels (conventional low-carbon steel and a novel duplex alloy steel with Cr and Mo) were exposed to chloride-contaminated extract solutions (ordinary Portland cement (OPC) extract and alkali-activated slag (AAS) extract) to investigate their pitting corrosion resistance. The results confirm that the pitting corrosion resistance of the alloy steel is much higher than that of the low-carbon steel in both extract solutions with various NaCl concentrations. Moreover, for each type of steel, the AAS extract contributes to a higher pitting corrosion resistance compared with the OPC extract in the presence of chloride ions, likely because of the formation of flocculent precipitates on the steel surface.     

低温盐浴渗氮对Custom 465钢耐蚀及耐磨性的影响

为了提高Custom 465马氏体沉淀硬化不锈钢的耐磨性,分别在440、480和520℃对580℃时效后的样品进行了2 h的盐浴渗氮,使用显微硬度计、X射线衍射仪、电化学工作站、球盘式摩擦磨损仪、表面轮廓仪、扫描电镜等设备,研究渗氮温度对Custom 465钢表面物相、硬度、渗层显微形貌、耐蚀性及耐磨性的影响. 随着渗氮温度升高,耐蚀性逐渐降低,但表面硬度增加,520℃处理后表面硬度增大到1240 HV,较未处理试样的400 HV明显上升,渗层厚度达到22μm. 440℃渗氮后表面物相为氮在马氏体基体中过饱和的α'N ,点蚀电位降低约60 mV;480℃时有少量CrN相析出,引起点蚀电位降低约180 mV,同时磨损体积下降约43%;520℃时CrN相的含量明显升高,自腐蚀电位降低约70 mV,无明显的稳态钝化区,磨损体积降低82%,减磨效果明显.     

不锈钢缝隙腐蚀诱发过程的快速研究

本文通过对带缝试样施加小幅值恒定阳极极化电流的方法,人为地突出了缝隙微区的影响和作用,为寻求一种既能缩短缝隙腐蚀研究周期,又能较少地干拢腐蚀体系自身反应的实验技术进行了初步的尝试。实验结果表明,不锈钢钝化膜表面的性质与缝内溶液的状态是影响缝隙腐蚀诱发过程的两个重要因素。     

Effects of chromium on the corrosion and electrochemical behaviors of ultra high strength steels

The effects of chromium on the corrosion and the electrochemical behaviors of ultra high strength steels were studied by the salt spray test and electrochemical methods. The results show that ultra high strength steels remain martensite structures and have anodic dissolution characteristic with an increase of chromium content. There is no typical passive region on the polarization curves of an ultra high strength stainless steel, AerMet 100 steel, and 300M steel. However, chromium improves the corrosion resistance of the stainless steel remarkably. It has the slowest corrosion rate in the salt spray test, one order of magnitude less than that of AerMet 100 and 300M steels. With the increase of chromium content, the polarization resistance becomes larger, the corrosion potential shifts towards the positive direction with a value of 545 mV, and the corrosion current density decreases in electrochemical measures in 3.5wt% NaCl solutions. Because of the higher content of chromium, the ultra high strength stainless steel has a better corrosion resistance than AerMet 100 and 300M steels.     

南海东部海域不锈钢紧固件的腐蚀失效分析

【目的】为配合南海东部海区的海洋环境调查,研究该海区不锈钢紧固件发生的腐蚀现象。【方法】使用奥氏体不锈钢紧固件,利用海洋平台钢桩和不锈钢钢缆紧固相应的调查设备,通过一年的海试,检查该类不锈钢紧固件的腐蚀情况。【结果】不锈钢紧固件腐蚀严重,不同形状的材料腐蚀部位和程度不同。不锈钢的腐蚀主要表现为点蚀和隙缝腐蚀等局部腐蚀,严重时穿孔、断裂失效。【结论】建议在海洋金属结构中尽量使用同牌号同批次的同种金属材料,以确保材料电极电势相同,减小宏观电池的形成;若确实需要使用异种金属,必须对异种材料间进行电绝缘。