Korrosionsprobleme in chlorhaltigen Medien: Lösungsmöglichkeiten durch einige nichtrostende Spezialstähle

Corrosion problems in chloride containing media: possible solution by some stainless special steels The increasing water pollution forces the chemical industry to use water with increasing chloride content for cooling and other purposes. This trend brings about increasing corrosion danger, in particular pitting, stress corrosion cracking and corrosion fatigue as well as crevice corrosion. The present paper deals with some steels characterized by resistance to these specific corrosion phenomena. A steel containing (%) 21 Cr., 7.5 Ni, 2.5 Mo, 1.5 Cu, to 2 Mn, to 1 Si and 0.06 C is particularly resistant to stress corrosion cracking. It contains 30 to 50% ferrite in an austenitic matrix. Even in Mg chloride solutions it may be kept under a load of 7 kg/mm² without stress corrosion occurring (with a steel of the 18 10 CrNiMo type the admissible load is only 2 kg/mm²). A steel containing (%) 25 Ni, 21 Cr, 4.5 Mo, 1.5 Cu, to 1 Si, to 2 Mn, and 0.02 C has a broad passivity range and is resistant to general corrosion in acid reducing media and phosphoric acid of all concentrations. A ferritic steel containing (%) 26 Cr. 1 Mo and minor additions of C, Mn, Si, Cu, Ni and nitrogen is resistant to stress corrosion cracking in neutral chloride solutions and general corrosion in oxidizing and neutral media, even against hydrogen sulfid and organic acids; it is beyond that lergely resistant to pitting in chloride solutions.     

Corrosion susceptibility of peened friction stir welded 7075 aluminum alloy joints

Effects of surface treatment techniques like laser and shot peening on stress corrosion cracking (SCC) susceptibility of friction stir welded (FSW) 7075 aluminum alloy joints were investigated. This study had two parts; the first part investigated the peening effects on stress corrosion cracking susceptibility in FSW samples by slow strain rate testing in a 3.5% NaCl solution. The second part of the study investigated the effects of peening on corrosion while submerged in a 3.5% NaCl solution with no external loads applied. No signs of corrosion pitting or SCC were evident on any of the tensile samples during the slow strain rate testing. The FSW plates exposed in 3.5% NaCl solution for 60 days were inspected periodically for signs of corrosion and stress corrosion cracking in the areas expected to have residual stresses due to welding. Pitting corrosion was seen on the samples, but even after 60 day exposure no stress corrosion cracking was detected on any of the peened or unpeened samples.     

Untersuchungen zum Einfluss des Stickstoffs auf das Lochkorrosionsverhalten hochlegierter austenitischer Cr‐Ni‐Mo‐Stähle

Investigation of the influence of nitrogen on the pitting corrosion of high alloyed austenitic Cr‐Ni‐Mo‐steels Austenitic stainless steels (18% Cr, 12% Ni, Mo gradation between 0.5 to 3.6%) had been gas‐nitrided. By stepwise removal, samples could be prepared with various surface content of nitrogen up to 0.45%. The susceptibility against pitting corrosion of these samples had been tested by two methods: – determination of the stable pitting potential in 0.5 M NaCl at 25°C – determination of the critical pitting temperature in artificial sea water (DIN 81249‐4) The influence of nitrogen to both determined parameter can be described well by PRE = Cr + 3,3 · Mo + 25 · N That means for the investigated steel composition and the used corrosion system there is no influence of molybdenum on the effectiveness of nitrogen.     

1Cr18Mn14N不锈钢在HCl溶液中的空蚀行为

利用磁致伸缩空蚀实验机研究了1Cr18Mn14N不锈钢在HCl溶液中的空蚀行为，利用扫描电镜(SEM)跟踪观察了试样表面的空蚀形貌，测量了静态和空蚀条件下的极化曲线和电化学阻抗谱(EIS)，分析了腐蚀和氢对空蚀损伤的影响,结果表明：在0．1mol／LHCl溶液中，加工硬化能力高的1Cr18Mn14N不锈钢的抗空蚀性能优于水轮机常规用材0Cr13Ni5Mo；当盐酸浓度增大为0．5mol／L时，阳极溶解和氢的共同作用促进1Cr18Mn14N不锈钢表面裂纹的形核和失稳扩展，裂纹扩展、连接引起材料大量脱落，使1Cr18Mn14N不锈钢的抗空蚀性能大大劣化，反而不如0Cr13Ni5Mo不锈钢．     

回火马氏体钢中氢的扩散行为及其氢脆敏感性

通过TDS方法研究了氢在18Cr2Ni4W和25CrNi2MoVNb两种低温回火马氏体钢中的扩散行为,同时结合慢应变速率拉伸实验研究了这两种马氏体钢的氢脆敏感性。结果表明,与18Cr2Ni4W钢相比,25CrNi2MoVNb钢因碳含量较高和晶粒显著细化作用使抗拉强度从1300 MPa级提高到了1500 MPa级后,其氢脆敏感性也明显增加。通过试样充氢后放置试验,测定氢在25CrNi2MoVNb钢和18Cr2Ni4WA钢中的扩散系数分别为7.87×10-7 cm2/s和3.99×10-7 cm2/s。可见,氢在25CrNi2MoVNb钢中更容易扩散,因而在充入相同可扩散氢时,25CrNi2MoVNb钢性能损失更大。     

1500 MPa级40CrNi3MoV钢的氢脆敏感性

通过慢应变速率拉伸实验研究了Si含量分别为0.25%和1.16%的1500 MPa级40CrNi3MoV钢的氢脆敏感性,即充氢后缺口试样抗拉强度下降率,冲击实验用来测试1 mA/cm2电流密度下充氢后试样的断裂韧性值,分析氢致裂纹的扩展方式.结果表明,由于Si抑制回火过程中碳化物的形核和长大,高Si含量的40CrNi3MoV钢中回火析出的碳化物被细化且弥散分布,作为氢陷阱使氢分布均匀,抑制了氢向裂纹尖端扩散,高Si含量的40CrNi3MoV钢的氢脆敏感性较低.     

玻璃喷丸处理提高304不锈钢焊接接头抗应力腐蚀性能的研究

基于对304不锈钢焊接试板表面喷丸处理前后的表层残余应力X射线衍射测量，研究了在42％沸腾MgCl2溶液中，表面玻璃喷丸和铸钢喷丸对304不锈钢焊接试板应力腐蚀开裂敏感性的影响，比较了采用不同铸钢喷丸和玻璃喷丸处理工艺的304不锈钢焊接试板抗应力腐蚀开裂的能力．试验结果表明：未喷丸处理的焊接试板6h就发生开裂，50％、100％覆盖率的铸钢喷丸焊接试板分别在试验310h和3500h开裂，而200％覆盖率的铸钢喷丸焊接试板，50％、100％、200％覆盖率的玻璃喷丸焊接试板经历3500h也未见开裂．因此，喷丸处理工艺能够很好地提高焊接构件抗应力腐蚀开裂能力；且在同样喷丸强度下，焊接接头经玻璃喷丸工艺处理后的抗应力腐蚀能力明显优于铸钢喷丸处理工艺．     

低合金高强度抗应力腐蚀开裂海洋软管用钢的开发

通过合金成分设计,轧制、热处理工艺的探索,开发了低合金高强度海洋软管用钢,其屈服强度大于600 MPa且满足抗氢脆、抗氢致开裂、抗应力腐蚀开裂性能,并通过全浸腐蚀实验对该钢的海水腐蚀行为进行了研究。结果表明,采用低C、低Mn并复合添加耐蚀元素Cr、Mo和采用合理的热轧、冷轧、调质处理工艺,可获得满足抗应力腐蚀开裂性能的600 MPa级高强钢。耐蚀元素的添加使实验钢具有良好的耐海水腐蚀能力,腐蚀稳定状态下的平均年腐蚀速率为0.11 mm/a。     

Stress Corrosion Cracking Behavior of Peened Friction Stir Welded 2195 Aluminum Alloy Joints

The surface treatment techniques of laser and shot peening were used to investigate their effect on stress corrosion cracking (SCC) in friction stir welded (FSW) 2195 aluminum alloy joints. The investigation consisted of two parts: the first part explored the peening effects on slow strain rate testing (SSRT) in a 3.5% NaCl solution, while the second part investigated the effects of peening on corrosion while submerged in a 3.5% NaCl solution with no external loads applied. For the SSRT, the laser-peened samples demonstrated superior properties to the other samples, but no signs of corrosion pitting or SCC were evident on any of the samples. For the second part of the study, the FSW plates were inspected periodically for signs of corrosion. After 60 days there were signs of corrosion pitting, but no stress corrosion cracking was noticed in any of the peened and unpeened samples.     

Recent Advances on the Corrosion Resistance of Low-Density Steel: A Review

This paper reviews the previous literature on the alloy composition design of low-density steel (LDS), focusing on the effect of Al, Mn, Ni, and other alloy elements on the formation of the steel matrix and second phase, and provides classification. The microstructure of LDS after processing includes the matrix structure, к-carbide, and B2 (FeAl, NiAl, or MnAl) phase of ferritic LDS, austenitic LDS, and dual-phase LDS. The influence of alloy elements on the corrosion resistance of LDS is derived from the addition of Al and Mn for metallurgy. Additionally, the influence of Cr and Mo addition on the corrosion resistance improvement was studied. The electrochemical properties of the corrosion process in LDS are discussed. Further, the microstructure of LDS affects the corrosion resistance properties including pitting corrosion, hydrogen embrittlement, and SCC (stress corrosion cracking). Finally, future research directions are proposed.     

喷丸对预腐蚀后铝合金疲劳性能的影响

目的分析喷丸对铝合金腐蚀损伤构件疲劳性能的影响,为飞机构件的维修提供有效指导。方法以未喷丸、三面喷丸、三面喷丸腐蚀后再三面喷丸3类不同表面状态的7075铝合金试样为研究对象,改变Na Cl溶液质量分数、时间、温度,获得两种程度不同的腐蚀损伤,通过疲劳寿命、断裂位置、断口形貌,分析表面喷丸状态对铝合金疲劳性能的影响。结果腐蚀损伤较轻时,喷丸试样的疲劳寿命为未喷丸试样的7.84倍,喷丸试样腐蚀后若再喷丸处理,疲劳寿命是不再喷丸试样的1.62倍。未喷丸试样的断裂位置位于截面突变颈部区域,另两类喷丸试样的断裂位置则在夹持段前端。未喷丸试样的裂纹在断口表面的边缘位置形成,喷丸试样的中心区域形成光滑平整的稳态扩展区。腐蚀损伤严重时,喷丸处理仍然会提高铝合金的疲劳寿命,但3类不同表面状态试样的疲劳寿命差距会缩小;从试样断裂位置、断口形貌看,3类试样的差异也会弱化。结论铝合金腐蚀损伤件若腐蚀前进行表面先喷丸处理,疲劳性能会有明显提升;若腐蚀后再喷丸处理,疲劳性能还会进一步提升;喷丸处理还会削弱铝合金外形截面突变处的应力集中,抑制疲劳裂纹在构件表面的萌生及延伸。     

Mitigation of Stress Corrosion Cracking Susceptibility of Machined 304L Stainless Steel Through Laser Peening

The paper describes an experimental study aimed at suppressing stress corrosion cracking susceptibility of machined 304L stainless steel specimens through laser shock peening. The study also evaluates a new approach of oblique laser shock peening to suppress stress corrosion cracking susceptibility of internal surface of type 304L stainless steel tube. The results of the study, performed with an indigenously developed 2.5 J/7 ns Nd:YAG laser, demonstrated that laser shock peening effectively suppresses chloride stress corrosion cracking susceptibility of machined surface of type 304L stainless steel. In the investigated range of incident laser power density (3.2-6.4 GW/cm²), machined specimens peened with power density of 4.5 and 6.4 GW/cm² displayed lower stress corrosion cracking susceptibility considerably than those treated with 3.2 and 3.6 GW/cm² in boiling magnesium chloride test. Oblique laser shock peening, performed on machined internal surface of a type 304L stainless steel tube (OD = 111 mm; ID = 101 mm), was successful in introducing residual compressive surface stresses which brought about significant suppression of its stress corrosion cracking susceptibility. The technique of oblique laser shock peening, in spite of its inherent limitations on the length of peened region being limited by tube internal diameter and the need for access from both the sides, presents a simplified approach for peening internal surface of small tubular components.     

Cold cracking studies on low alloy steel weldments: effect of filler metal composition

Abstract

The resistance to hydrogen cracking of Cr - Mo, Ni - Cr - Mo and Si - Mn steels which are employed in armoured vehicle construction was evaluated under implant test conditions. Austenitic stainless steel filler (AWS E312), which is reported to be resistant to hydrogen assisted cracking, was used to study the cracking tendency of all the three steels. Four other fillers, namely a nickel based filler (ENiCrFe-3), a low carbon, low alloy steel, a mild steel (AWS E6013) and a matching filler for Cr - Mo, were employed to evaluate their relative cracking tendency. Cr - Mo and Ni - Cr - Mo steels exhibited high cracking tendency while Si - Mn steel was resistant to cracking with the E312 filler. Cr - Mo steel was resistant to cracking with the nickel based filler, the low carbon, low alloy steel and the matching filler. The observed cracking tendency of the steels is linked to a susceptible interface/fusion boundary microstructure.     

Comparative study of stress corrosion cracking susceptibility of Fe18Cr10Mn- and Fe18Cr10Mn1Ni-based high nitrogen stainless steels

The stress corrosion cracking (SCC) behavior of Fe18Cr10Mn1Ni(0.3–0.8)N alloys was investigated in aqueous NaCl environment by using slow strain rate test method, and the results were compared to those of Ni-free counterparts. The addition of N tended to improve the SCC resistance of Fe18Cr10Mn- and Fe18Cr10Mn1Ni-based alloys. The alloying Ni magnified the beneficial effect of N on the SCC susceptibility and, eventually, the Fe18Cr10Mn0.8N alloy was immune to SCC in 2 M NaCl solution at 50 °C. The SCC behavior of the present alloys was found to be closely related to the repassivation tendency and the resistance to pitting corrosion.     

Passivierungsverhalten und Spannungsrißkorrosion von Eisen-Mangan-Chrom-Legierungen in Natriumchlorid-Lösung

Passivation behaviour and stress corrosion cracking of iron-maganese-chromium alloys in sodium chloride solution Electrochemical experiments with MnCr steels (20–28% Mn, up to 12% Cr) in 3% NaCl solution. High Mn contents reduce the passivation tendency, while increasing Cr contents broaden the range of passivity. The formation of surface layers is due primarily to a direct reaction with the solution (good adhesion, high protective value) and, secondarily, to precipitation from the solution (porosity, low protective value). The tendency to form secondary layers increases as the Cr content is reduced. In oxygen containing solution there is a pronounced corrosion in the pitting range. At low Cr contents, stress corrosion cracking is mostly transcrystalline, at higher Cr contents (8–12%) it is intercrystalline, in particular when Cr carbide precipitations are present at the grain boundaries. In the range of transcrystalline corrosion the susceptibility to selective corrosion extends beyond the pitting potential. At higher Cr contents there may be pitting without any indication of stress corrosion cracking.     

喷丸对23Co14Ni12Cr3Mo超高强度钢 表面性能的影响

针对23Co14Ni12Cr3Mo超高强度钢材料，研究喷丸强化对其表面性能的影响。采用扫描电镜、白光干涉仪等设备，分析喷丸强化对试样表面形貌、粗糙度、硬度、残余应力、元素含量等的影响。结果表明:喷丸强化后，试样表面留有大量弹坑，产生明显塑性变形；表面粗糙度增大，算术平均粗糙度为1.33 μm；硬度显著增大，最表层硬度由喷丸前的HV 476增加至HV 497，硬化层深度约150 μm；试样表层的残余压应力值由375 MPa增加至475 MPa，最大残余压应力值约518 MPa，位于距表面50 μm深度处，喷丸形成的残余压应力层深度约为134 μm；喷丸后试样中C、Si、Cr等各元素的质量分数均略有增加。喷丸在一定程度上改善了23Co14Ni12Cr3Mo钢材料的表面性能，有利于提高其疲劳抗力和耐腐蚀性。     

Corrosion characteristics of the wrought Ni‐Cr‐Mo alloys

This paper concerns the wrought, nickel‐chromium‐molybdenum (Ni‐Cr‐Mo) alloys, a family of materials with a long history of use in the chemical process industries. Their attributes include resistance to the halogen acids and resistance to pitting, crevice attack, and stress corrosion cracking in hot, halide salt solutions. The purpose of this paper is to characterize the performance of the Ni‐Cr‐Mo alloys in several key chemicals, using iso‐corrosion diagrams. These indicate the expected corrosion rates over wide ranges of concentration and temperature. Furthermore, the differences between individual Ni‐Cr‐Mo alloys, and their behavior relative to the stainless steels are defined. The data indicate benefits of both a high chromium content and a copper addition, as used in Hastelloy® C‐2000® alloy.     

1Cr18Mn14N双相不锈钢在腐蚀介质中的抗空蚀性能

利用磁致伸缩空蚀实验机研究了1Cr18Mn14N双相不锈钢在3%NaCl和05 mol/L HCl溶液中的空蚀行为.结果表明：在3%NaCl溶液中，低硬度的Cr18Mn14N双相不锈钢的抗空蚀性能优于高硬度的水轮机常规用材0Cr13Ni5Mo.1Cr18Mn14N双相不锈钢的空蚀破坏首先在铁素体相发生，铁素体相的失效方式为脆性失效，而奥氏体相是延性失效.奥氏体相区由滑移和孪生引起的塑性变形耗散了空泡溃灭产生的冲击能量，从而提高1Cr18Mn14N双相不锈钢的抗空蚀性能.在05 mol/L HCl溶液中，1Cr18Mn14N的抗空蚀性能不如0Cr13Ni5Mo，结果与3%NaCl溶液中的正好相反，这是由于阳极溶解和氢共同作用的结果.     

Cl–对冷变形316L奥氏体不锈钢在H2S环境下应力腐蚀的影响

目的研究H2S环境下不同Cl^-浓度对冷变形316L奥氏体不锈钢应力腐蚀行为的影响,探究Cl^-造成影响的原因,为不锈钢安全服役提供理论数据。方法采用力学方法研究了冷变形316L奥氏体不锈钢的力学行为,通过计算延伸率损失表征材料的应力腐蚀敏感性,通过电化学手段表征了点蚀电位。最后为了研究点蚀与基体中氢含量的关系,进行了扩散氢含量的测试,通过测量试样的扩散氢含量,进一步理解应力腐蚀行为。结果随着Cl^-浓度的增加,316L奥氏体不锈钢的延伸率损失逐渐增大,应力腐蚀敏感性增强。断口形貌从杯状的等轴韧窝转变为解理型脆性断裂。动电位极化测试表明,Cl^-浓度的增加,点蚀电位逐渐降低,直至–0.0228V,试样更容易发生点蚀。扩散氢含量的测量进一步显示了点蚀坑的存在促进了氢进入到金属内部。结论 Cl^-对316L奥氏体不锈钢在H2S环境中的应力腐蚀行为有重要影响,随着Cl^-浓度的增加,应力腐蚀敏感性增强,结合点蚀电位的测量结果,可能是由于Cl^-破坏金属表面的钝化膜,产生点蚀坑,裂纹形核并扩展,同时点蚀坑还促进了氢进入金属内部,应力腐蚀敏感性增强。     

Elektrochemisches Verhalten und Deckschichtbildung hochlegierter Manganstähle

Electrochemical behaviour and scaling of high alloy manganese steels Passivating surface layers are considered to be one of the indispensable requirements for stress corrosion cracking of metallic materials. It is shown by potentiostatic and potentiokinetic current density-potential curves that the steel X 40 MnCrN 19 in neutral aqueous chloride solutions has a passive potential region. The passivation behaviour Of precipitation hardened samples is in agreement with the chromium depletion theory. The effect of alloying on the passivation behaviour of low carbon Mn steels is studied in 3 % NaCl solution at 20 and 100 °C Increasing proportions ε-martensite reduce the passivation of susceptibility. Increasing the Mn content has the same effect. The vital factor concerning passivation behaviour, however, is chromium content. Increasing the temperature of the corrodent results in an increased tendency to form scales of steels containing less than 8 % Cr. Long-term corrosion tests have shown, that increasing the Cr content produces a continuous transition from general localized and even pitting Corrosion. Tests made without applied current in aerated solutions have shown, that the variation in time of corrosion potentials depends from the tendency to be passivated of the materials and from the oxygen content of the solutions. In oxygen containing solutions passivable steels exhibit a pronounced corrosion in the pitting region, because with such alloys anodic dissolution current densities equal to those of the limiting diffusion current of oxygen reduction are obtained only at potentials above the pitting potential.