高锰氮双相不锈钢25Cr-2Ni-10Mn-xW-N的组织和性能研究

研究了钨含量对新型高锰氮双相不锈钢25Cr-2Ni-xW-10Mn-N(x=1.5,3.0,4.5)的显微组织、力学性能以及耐腐蚀性能的影响。结果表明:该系不锈钢固溶处理后具有典型的铁素体+奥氏体双相组织,随着固溶温度的增加,铁素体含量上升。随着钨含量的增加,σ相析出增加,铁素体体积分数增大,耐点蚀性增强,屈服强度上升,断裂延伸率和冲击韧性降低。此类钢作为结构材料具有广阔的应用前景。     

Effects of Rare Earth Metals addition and aging treatment on the corrosion resistance and mechanical properties of super duplex stainless steels

Effects of rare earth metals addition and aging treatment on corrosion resistance and mechanical properties of super duplex stainless steels were investigated using optical/SEM/TEM metallographic examination, an X-ray diffraction test, a potentiodynamic anodic polarization test and a tensile test. The performance of the experimental alloy with 0.32% REM addition was compared with commercial super duplex stainless steel such as SAF 2507 when they were exposed to solution annealing heat treatment and aging treatment. The corrosion resistance in Cl⁻ environments and mechanical properties of the experimental alloy were found superior to those of the commercial duplex stainless steel. The REM with larger atomic radii than those of Cr, Mo and W may fill vacancies inside the matrix and around the grain boundaries, retarding formation of harmful intermetallic σ and η phases. In addition, fine REM oxides/oxy-sulfides (1–3 μm) seemed to enhance the retardation effects. With REM additions, strength and ductility increased due to the phase and grain refinement caused by fine REM oxides and oxy-sulfides.     

Development of high Mn-N duplex stainless steel for automobile structural components

A new high Mn-Ni free (duplex stainless steel) DSS containing 18Cr-6Mn-1Mo-0.2N has been developed by examining the effects of manganese on the corrosion and mechanical properties of high Mn SSs containing 18Cr-4 ∼ 11Mn-0 ∼ 2Ni-0 ∼ 1Mo-0.2N. The alloy with 45% ferrite is found to be an optimum alloy with much higher mechanical strength and similar corrosion resistance compared with those of standard SS304. In addition, the alloy was free of precipitation of sigma phase and Cr-nitride when exposed to high temperatures due primarily to relatively low contents of Cr, N and Mo. With an increase in Mn content, the resistance to pitting and metastable pitting corrosion of high Mn DSS decreased since the number of (Mn, Cr) oxides, acting as preferential sites of pitting, increased with the Mn content.     

Hochlegierte korrosionsbeständige Stähle für Chemie‐, Energie‐ und Meerestechnik – Rückblick und Ausblick

High‐alloyed corrosion resistant steels for the chemical process industry, power engineering and marine technology – past and future Today's most common high‐alloyed corrosion resistant steels are in their majority characterised by very low contents of carbon and sulphur and, in many cases, by substantial amounts of nitrogen as an alloying constituent. Their broad use in the chemical process industry, power generation and marine technology has become possible when new metallurgical processes for steel making had been introduced in the 1960s. The time before had seen mainly stabilised grades, being highly alloyed with copper in many cases, which have disappeared to a large extent in our days. The superferritic grades (ferritic steels with ≥ 25% chromium) had been the materials of great expectations in the 1970s, but have found a very limited application only in the chemical industry since then, e.g. for the handling of hot concentrated sulphuric acid, due to the high risks of low ductility cracking of these materials at greater wall thickness. These risks can be managed better if the highly alloyed ferritic phase is present in a finely dispersed compound with an austenitic phase where the ferritic part is adding its advantages, higher strength and resistance to stress corrosion cracking, to the duplex compound. This can result in low weight and corresponding cost saving. The application of the corrosion resistant duplex grades will expand further as much as users will better learn the special requirements of manufacturing of these materials and to take advantage of their unique properties. However, the most important alloy developments since the 1960s have been seen in the field of the austenitic stainless steels being highly alloyed with chromium, molybdenum and nitrogen. Especially the austenitic 6% Mo grades as e.g. X1NiCrMoCuN25‐20‐7 – alloy 926 (1.4529) have found many applications in chemical process industry, power generation and marine technology. Higher alloyed grades as e.g. X1NiCrMoCu32‐28‐7 – alloy 31 (1.4562) are excelling in extraordinary resistance to corrosion by acids and pitting attack. In addition today's upper limits of alloying austenitic corrosion resistant grades have been explored with grade X1CrNiMoCu33‐32‐1 – alloy 33 (1.4591) for chromium additions up to about 33% and with grade X1NiCrSi24‐9‐7 – alloy 700 Si (1.4390) for additions of silicon up to about 7%, providing a high corrosion resistance mainly in oxidising acids. When considering the prospects of further development of the corrosion resistant duplex grades the ferritic phase within these materials is both offering chances and setting limits. The high‐alloyed austenitic corrosion resistant steels have a potential being unexplored so far in the alloy range where molybdenum and nitrogen are becoming more prominent compared to the chromium content.     

Effects of rare earth metals addition on the resistance to pitting corrosion of super duplex stainless steel - Part 1

To elucidate the effects of rare earth metals addition on the resistance to pitting corrosion of super duplex stainless steel, a metallographic examination, potentiodynamic and potentiostatic polarization tests, a SEM-EDS and a SAM analysis of inclusion, austenite phase and ferrite phase were conducted. The addition of rare earth metals to the base alloy led to the formation of (Mn, Cr, Si, Al, Ce) oxides and (Mn, Cr, Si, Ce) oxides, which improved the resistance to pitting corrosion and caused a decrease in the preferential interface areas for the initiation of the pitting corrosion.     

Influence of cold work and sigma phase on the pitting corrosion behavior of 25 chromium super duplex stainless steel in 3.5% sodium chloride solution.

The effect of cold work (up to 16% strain) and sigma phase precipitation (at 850 °C for 10 and 60 min) on the pitting resistance of 25 chromium super duplex stainless steel were investigated in 3.5% sodium chloride solution at 70 and 90 °C. Anodic polarization scans for cold worked samples revealed immunity to pitting attack at 70 °C even with 16% strain. At 90 °C, the alloy still showed high pitting resistance, pitting occurring at about 600 mV (SCE) for the 16% plastic strain samples. A serious deterioration of the pitting corrosion resistance was found after heating the alloy at 850 °C for 10 min resulting in a clear drop in the pitting potential at 90 °C. After heating for 60 min, the material showed rapid deterioration of pitting corrosion resistance at 70 °C.     

Stainless steel reinforcing bars – reason for their high pitting corrosion resistance

In harsh chloride bearing environments stainless steel reinforcing bars offer excellent corrosion resistance and very long service life for concrete structures, but the high costs limit a more widespread use. Manganese bearing nickel‐free stainless steels could be a cost‐effective alternative. Whereas the corrosion behavior of stainless steels in alkaline solutions, mortar and concrete is quite well established, only little information on the reasons for the high pitting resistance are available. This work reports the results of pitting potential measurements in solutions simulating alkaline and carbonated concrete on black steel, stainless steel DIN 1.4301, duplex steel DIN 1.4462, and nickel‐free stainless steel DIN 1.4456. Duplex and nickel‐free stainless steels are fully resistant even in 4 M NaCl solutions with pH 13 or higher, the lower grade DIN 1.4301 shows a wide scatter between fully resistant and pitting potentials as low as +0.2 V SCE. In carbonated solutions with pH 9 the nickel‐free DIN 1.4456 shows pitting corrosion at chloride concentrations ≥3 M. This ranking of the pitting resistance can be rationalized based on XPS surface analysis results: both the increase of the Cr(III)oxy‐hydroxide and Mo(VI) contents in the passive film and a marked nickel enrichment beneath the film improve the pitting resistance. The duplex DIN 1.4462 shows the highest pitting resistance, which can be attributed to the very high Cr(III)oxy‐hydroxide, to a medium Mo(VI) content in the film and to a nickel enrichment beneath the film. Upon time, the protective properties of the surface film improve. This beneficial effect of ageing (transformation of the passive film to a less Fe²⁺ containing, more hydrated film) will lead to higher pitting potentials. It can be concluded that short‐term solution experiments give conservative results in terms of resistance to chloride‐induced corrosion in reinforced concrete structures.     

稀土对超高强度钢耐海洋大气腐蚀性能的影响

目的提高超高强度钢耐海洋大气腐蚀的性能。方法采用周期浸润腐蚀试验箱模拟一般条件下海洋大气腐蚀试验,通过金相显微镜和扫描电子显微镜观察低合金超高强度钢的组织和夹杂物的形貌,采用失重法和电化学阻抗技术分析腐蚀动力学规律及电化学行为规律。结果稀土在低合金超高强度钢中具有细化组织和变质夹杂物的作用,稀土增强了锈层的致密性,使得低合金超高强度钢的耐蚀性能显著提高,且随着稀土含量的增加,锈层电阻值逐渐增大,即稀土提高了锈层对基体的保护能力。结论在低合金超高强度钢中添加稀土能够细化组织、变质夹杂物。稀土低合金超高强度钢的夹杂物主要为球形稀土复合氧硫化物。稀土质量分数为0.08%的低合金超高强度钢的耐腐蚀性能最好。     

固溶温度对2507双相不锈钢力学性能及耐蚀性的影响

利用光学显微镜、扫描电镜、XRD、拉伸试验机和电化学综合测试仪等研究了不同固溶温度对2507超级双相不锈钢组织、力学性能和耐蚀性的影响。采用Thermo-Calc热力学软件计算了2507双相不锈钢的热力学平衡相图,并与测试结果进行了对比。研究结果表明,经1050 ℃及以上温度固溶后,σ相溶解;随着固溶温度的升高,铁素体相含量增加,奥氏体相含量降低,α/γ相体积分数比增加;1050~1100 ℃固溶30 min并水冷时,双相不锈钢具有较好的综合力学性能,屈服强度、抗拉强度和伸长率分别大于600 MPa、840 MPa和35%。1050 ℃固溶30 min时,双相钢可获得较好的耐蚀性能。     

航天轴承新贵:60NiTi合金

在NiTi系合金大家族中,等原子比的NiTi合金具有形状记忆效应和超弹性。相比于等原子比NiTi合金,60NiTi合金不会发生热弹性马氏体相变,不具有形状记忆效应和超弹性,但是它在硬度、耐腐蚀性和弹性性能等方面具有出众的潜能,在航天领域上展现了良好的应用前景。固溶态60NiTi合金同时具备结构稳定性、超强的耐腐蚀性、出色的耐磨性,已成为航天轴承候选新材料。     

Influence of regulated modification of nitride layer by oxygen on the electrochemical behavior of Ti–6Al–4V alloy in the Ringer's solution

The corrosion behavior of oxynitrided Ti–6Al–4V alloy was investigated in the Ringer's solution (simulated body fluid) at a temperature of 37°C. The oxynitriding of the alloy was carried out by leaking controlled oxygen‐containing medium into the reaction chamber at the final stage of the nitride formation. It was determined that oxynitriding improved corrosion resistance of Ti–6Al–4V alloy as it provided lower corrosion current density by 1.3–1.5 times and higher corrosion potential. In this paper, we analyzed that the resistance of the double layer had increased with the increase of the oxygen content in titanium oxynitride. Its value was higher compared with untreated alloy, indicating higher corrosion resistance of the oxynitrided one.     

Siliziumnitrid — ein korrosionsbeständiger Hochtemperaturwerkstoff

Silicon nitride — a corrosion resistant refractory material Silicon nitride as a material having high temperature strength (flexural strength at 1500° C still 15–20 kp/mm²) is, in addition, highly corrosion resistant. This resistance applies to mineral acids (although results are somewhat scattering), and even HF produces but slow dissolution. Oxide slags and glass melts attack but slowly, and it is resistant to many salt melts, not, however to hydroxide solutions or molten alkalies. Nonoxidising gases have no effect, in oxidising atmospheres a protective SiO₂ layer is formed which yields good resistance up to 1600° C. Hydrogen does not react up to 1250° C with silicon nitride. Molten metals attack vehemently when the corresponding silicides are formed easily. The reaction with copper takes place in the air only, not in the vacuum.     

Corrosion behavior of Ti‐xNb‐13Zr alloys in Ringer's solution

Ti‐6Al‐4V alloy has been widely used in restorative surgery due to its high corrosion resistance and biocompatibility. Nevertheless, some studies showed that V and Al release in the organism might induce cytotoxic effects and neurological disorders, which led to the development of V‐free alloys and both V‐ and Al‐free alloys containing Nb, Zr, Ta, or Mo. Among these alloys, Ti‐13Nb‐13Zr alloy is promising due to its better biomechanical compatibility than Ti‐6Al‐4V. In this work, the corrosion behavior of Ti, Ti‐6Al‐4V, and Ti‐xNb‐13Zr alloys (x = 5, 13, and 20) was evaluated in Ringer's solution (pH 7.5) at 37 °C through open‐circuit potential measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy. Spontaneous passivity was observed for all materials in this medium. Low corrosion current densities (in the order of 10^?7 A/cm²) and high impedance values (in the order of 10⁵ Ωcm² at low frequencies) indicated their high corrosion resistance. EIS results showed that the passivating films were constituted of an outer porous layer (very low resistance) and an inner compact layer (high resistance), the latter providing the corrosion resistance of the materials. There was evidence that the Ti‐xNb‐13Zr alloys were more corrosion resistant than both Ti and Ti‐6Al‐4V in Ringer's solution.     

不同固溶制度对6082铝合金力学性能和腐蚀性能的影响

采用拉伸力学性能试验、电导率性能试验、剥落腐蚀试验、晶间腐蚀试验、光学显微镜、扫描电镜、透射电镜等研究了不同固溶工艺对轨道交通用6082合金板材力学性能和腐蚀性能的影响。结果表明:530~560℃固溶及180℃时效处理后,6082合金板材的屈服强度和抗拉强度随着固溶温度升高而升高,而伸长率几乎保持不变。在530~560℃不同温度固溶处理的时效态6082板材的剥落腐蚀等级均为N级,显示出良好的耐剥落腐蚀性能,最大晶间腐蚀深度随着固溶温度升高而增加。不同温度固溶处理后时效态6082合金板材的晶界处均没有沉淀物析出,晶界附近的无沉淀析出带(PFZ)越宽,最大晶间腐蚀深度越深。     

Autoklaven-Untersuchungen der Spannungsrißkorrosion von Fe-Cr-Ni-Legierungen in NaCl/Co2/H2S-Medien

Autoclave investigation of stress corrosion cracking behaviour of Fe-Cr-Ni alloys in NaCl/CO₂/H₂S-environment In oil and gas production, the corrosion problems increase as the depth of the reservoirs increases. The oil and gas products contain chloride-rich waters and mixtures of H₂S and CO₂ at high pressures and temperatures. Materials that can be used under these conditions are only high strength high alloy steels and nickel base alloys. These materials must be assessed for corrosion resistance under these conditions. The environment contain chloride ions and hydrogen sulphide, which are known to be critical components for SCC. With the aid of autoclave experiments, the fields of corrosion resistance for the materials no. 1.4462, 1.4563 and 2.4618 were determined as a function of temperature and hydrogen sulphide pressure. The base environment was a 5 Molar sodium chloride solution at 20 bar carbon dioxide. While the corrosion resistance of the duplex steel, material no. 1.4462, decreases markedly as the strength of the material and the hydrogen sulphide pressure increase, the two austenitic materials are completely resistant up to 300 °C and hydrogen sulphide pressure of 15 bar. Only at 300 °C and high partial pressures of hydrogen sulphide the material no. 1.4563 did fail, when stressed to stress levels higher than the YS. The crack path was predominantly transgranular with minute fractions of intergranular cracking. The microstructure appears to have no effect. All results indicate that a mixed mechanism of hydrogen- and chloride induced SCC is operting, while a corrosion enhancement due to interaction of both critical components takes place.     

Mg-Li合金表面浅绿色超疏水复合膜层的制备及耐蚀性能研究

通过微弧氧化着色技术在Mg-Li合金表面生成浅绿色类陶瓷膜层,并在着色膜表面有机镀膜复合改性。用蒸馏水在镀膜表面的静态接触角以及动电位极化曲线和电化学阻抗谱测试,分别研究复合改性前后润湿性及耐蚀性。结果表明,微弧氧化着色表面通过有机镀膜生长了一层有机薄膜,接触角由近0°变为169.2°,实现了超亲水到超疏水的功能转化。Mg-Li合金基体经微弧氧化着色改性后,耐蚀性能明显提高,经复合改性后耐蚀性能进一步提高;与基体相比,超疏水复合膜在0.1 mol/L NaCl溶液中的动电位极化腐蚀电流密度减小3个数量级,电化学阻抗提高3个数量级。     

Enhanced corrosion resistance of Ni–W alloy with inclusion of TiN nanoparticles by electrodeposition method

Abstract

Electrodeposition of Ni–W–TiN nanocomposite on mild steel substrate from an ammoniacal citrate bath containing dispersed titanium nitride has been demonstrated. The structure, surface morphology, composition and corrosion resistance properties of the nanocomposite deposits have been characterised by using various techniques. X-ray diffraction analysis (XRD) of the electrodeposited Ni–W–TiN nanocomposite shows that it is fcc crystalline. Scanning electron micrography (SEM) reveals smaller grains and uniform distribution of the titanium nitride in the alloy matrix. The microhardness of the nanocomposite coatings is higher than that of the alloy. The corrosion resistance of the electrodeposited nanocomposite evaluated by electrochemical impedance and Tafel polarization studies showed that the Ni–W–TiN nanocomposite is more corrosion resistant than the Ni–W alloy deposit. The finer grain and uniform distribution of the titanium nitride in alloy matrix favour the enhanced microhardness and corrosion resistance of the nanocomposite.     

船用钛合金微弧氧化膜的性能及其研究进展

钛合金密度小、比强度高、可加工性好及耐海水腐蚀性强,是一种优秀的船舶材料.然而钛合金较低的耐磨性能、耐高温氧化性能及其对异种金属的电偶腐蚀等制约了其在船舶中实际应用.通过微弧氧化在钛合金表面原位生长氧化物陶瓷层,可显著改善钛合金的以上性能.文中综述了国内外船用钛合金微弧氧化研究进展及微弧氧化对钛合金的耐磨性、耐蚀性、结合强度及抗高温氧化性能的研究现状,展望了微弧氧化技术改善船用钛合金表面性能的发展趋势.     

2507超级双相不锈钢中σ相的析出行为

利用扫描电镜、透射电镜、X射线衍射仪、电化学工作站等试验及手段,研究了2507(S32750)超级双相不锈钢经700～1000 ℃时效不同时间后σ相的析出规律及其对冲击性能和腐蚀性能的影响规律。结果表明:σ相析出速度很快,析出量随时效时间的延长先增加后逐步减少,在850~900 ℃时效后σ相的析出量最大。σ相的析出严重降低材料的冲击及腐蚀性能,建议时效温度不低于950 ℃。     

Corrosion resistance of different steel grades in the geothermal fluid of Molasse Basin

Long‐term corrosion resistance of carbon steels grade API L80 and API Q125 has been evaluated by means of electrochemical measurements and exposure tests in the Molasse Basin, one of the most important geothermal fluids in Europe. In addition, the localized corrosion resistance of the duplex stainless steel alloy 2205 and the austenitic stainless steel grade 316L was determined at 100 and 150 °C. In general, investigated materials showed a remarkable resistance to uniform and localized corrosion. Their corrosion behaviour at service conditions is discussed in this paper.