丝状锈的微观分析

1 前言腐蚀是人们日常生活中常见的一种材料破坏或变质现象。按照腐蚀本身所显示的形式,可以划分为均匀腐蚀或全面腐蚀、电偶腐蚀、缝隙腐蚀、孔蚀、晶间腐蚀、磨损腐蚀和应力腐蚀等。丝状腐蚀属     

新型铸造Ni－Cu合金的成分设计及腐蚀行为的研究

本文设计了新型铸造Ｎｉ－Ｃｕ合金的化学成分，并通过多种腐蚀试验方法研究了该合金的均匀腐蚀、晶间腐蚀及点蚀行为。试验结果表明，铸造Ｎｉ－Ｃｕ合金具有良好的均匀腐蚀与局部腐蚀性能。此外，该合金还具有较好的综合机械性能与铸造性能。     

油气田用Inconel718合金腐蚀性能研究综述

综述了油气田用Inconel 718合金抗均匀腐蚀、点蚀、晶间腐蚀、电偶腐蚀、氢脆和应力腐蚀等常见腐蚀性能,分析了Inconel 718合金耐蚀性能良好的主要原因,着重阐述了Inconel 718合金热处理工艺对各种腐蚀行为的影响,并提供了合理的热处理工艺对应的安全服役环境。最后展望了高温高压含H2S腐蚀环境下Inconel 718合金的选材依据、应用前景,以及Inconel 718合金性能提高的热点和难点。     

氮含量对高纯奥氏体不锈钢耐蚀性能的影响及机理的研究

采用电化学、化学浸渍、ＸＰＳ、ＡＥＳ、物理化学相分析等方法研究了氮对高纯奥氏体不锈钢０００Ｃｒ１９Ｎｉ１４耐点蚀、晶间腐蚀和应力腐蚀开裂性能的影响并对其作用机理进行了探讨。结果表明，氮的加入可以显著改善钢的耐点蚀性能；高纯奥氏体不锈钢加氮（≤０．２０％）合金化敏化热处理不会引起晶界贫铬，在沸腾６５％ＨＮＯ３中主要是均匀腐蚀；在含有Ｃｒ６＋的硝酸溶液中，当氮含量不超过０．０８６８％时对晶间腐蚀影响很小，而氮含量超过０．０８６８％时氮含量增加则晶间腐蚀加剧。因此认为氮元素在晶界偏聚以及高氮钢中氮化铬在晶界的析出是晶间腐蚀加剧的原因；在沸腾４２％ＭｇＣｌ２溶液中的慢应变速率实验（ＳＳＲＴ）结果显示，适当量的加入氮，可以降低固溶态钢的应力腐蚀敏感性，而对敏化态钢没有影响。     

1420合金的应力腐蚀断裂行为

采用电化学方法和慢应变速率拉伸(SSRT)技术，研究了时效制度对1420Al-Li合金的时效动力学及抗应力腐蚀性能的影响。通过透射电镜、扫描电镜观察与分析，探讨了不同时效处理工艺下1420合金的显微组织、慢应变速率拉伸断口形貌及其影响机制。结果表明，与120℃／12h相比，采用120℃，6h 190℃，6h处理不仅可以缩短合金到达时效峰值的时间，提高合金的强度，使其断裂强度、断裂时间、延伸率以及总断裂能等都得到显著提高，同时也改善了合金的抗应力腐蚀性能。     

微量Zn对Al-Cu-Mg合金力学性能及晶间腐蚀的影响

采用扫描电子显微镜（SEM）、电子背散射衍射（EBSD）、电导率测试及常温拉伸实验,结合剥落腐蚀测试、晶间腐蚀测试和电化学测试研究了微量Zn对Al-Cu-Mg合金组织与性能的影响。试验结果表明,微量Zn的添加明显提高了合金T3态（预拉伸+自然时效）的塑性。随着Zn含量的增加,T3态合金点蚀电位提高,S相、阴极相和铝基体之间的电位差减小,点蚀的形成和晶间腐蚀的传播更加困难,合金的晶间腐蚀敏感性降低。     

铸造钛合金ZTC4的腐蚀与腐蚀行为

采用不同的试验方法研究了铸造钛合金ＺＴＣ４的腐蚀与腐蚀德全等结果表明，该合金具有优良的均匀腐蚀，点蚀，晶间腐蚀与磨蚀性能，是处于ＮＨ４Ｃｌ介质中高速旋转件的理想材料。     

Ti－6A1－4V合金的腐蚀与磨蚀行为的研究

本文采用多种试验方法，研究了Ｔｉ与Ｔｉ－６Ａ１－４Ｖ的腐蚀与磨蚀行为。试验结果表明，Ｔｉ－６Ａ１－４Ｖ合金具有优良的均匀腐蚀、点蚀、晶间腐蚀与磨蚀性能。     

铸造钛合金ZTC4的腐蚀与磨蚀行为

采用不同的试验方法研究了铸造钛合金ＺＴＣ４的腐蚀与磨蚀行为。结果表明，该合金具有优良的均匀腐蚀、点蚀、晶间腐蚀与磨蚀性能，是处于ＮＨ４Ｃｌ介质中高速旋转件的理想材料。     

Ti—6Al—4V合金的腐蚀与磨蚀行为的研究

本文采用多种试验方法，研究了Ｔｉ与Ｔｉ－６Ａｌ－４Ｖ的腐蚀与磨蚀行为。试验结果表明，Ｔｉ－６Ａｌ－４Ｖ合金具有优良的均匀腐蚀，点蚀，晶间腐蚀与磨蚀性能。     

Stress Corrosion Behavior of Low-temperature Liquid-Nitrided 316 Austenitic Stainless Steel in a Sour Environment

Low-temperature nitridation is a widely used surface heat treatment. Low-temperature liquid nitridation was applied to 316 austenitic stainless steel and an S-phase (expanded austenite) layer was achieved on the alloy surface. The effect of the S-phase layer on corrosion resistance and stress corrosion cracking was investigated in a sour environment. When a bending stress of 164 MPa (80 pct yield stress, YS) was applied, no macroscopic corrosion cracking and pits were observed on the nitrided samples and the S-phase layer stayed intact. Although no macroscopic corrosion cracking was observed on the non-nitrided samples under 205 MPa (100 pct YS), some pits were formed on the alloy surface. This could be attributed to the high stresses and hardness, and the excellent corrosion resistance of the S-phase layer introduced by low-temperature nitridation. Supersaturated nitrogen atoms in the S-phase layer can effectively prevent the decrease in pH of the corrosive medium and accelerate the alloy repassivation kinetics. However, when the bending stress was increased to 205 and 246 MPa (100 pct YS, 120 pct YS), macroscopic cracks were observed in the presence of both tensile stress and a corrosive medium.

     

Mg-5Gd-3Y-0.8Zr合金的微观组织及耐NaCl溶液腐蚀性能研究

系统研究了Mg-5Gd-3Y-0.8Zr合金的微观组织和耐蚀性能,通过静态失重法测定了其在NaCl溶液中的腐蚀速率。结果表明:铸态合金主要由基体α-Mg和方块状β相(Mg_5Gd、Mg_(24)Y_5)组成,时效处理后分布在晶界处的共晶β相数量明显增加;在NaCl溶液中腐蚀12 h以后镁合金的腐蚀速率明显增加,在3.5%Na Cl(质量分数)溶液中腐蚀24 h后,镁合金已被严重腐蚀,表面布满腐蚀坑和未脱落的白色腐蚀产物;镁合金易产生沿晶腐蚀,方块状共晶β相颗粒可有效阻止表面腐蚀沿晶界向镁合金内部扩展,从而提高镁合金的耐蚀性。     

Effects of environment on high-temperature fatigue crack growth in a superalloy

Fatigue crack growth rate measurements were made on Inconel alloy 718 samples at 650°C in fourteen different gaseous environments. Minor amounts of either oxygen or sulfur bearing species in the environment produced large increases in crack growth rates. Aggressive environments promoted intergranular crack growth. Kinetic factors rather than thermodynamic ones appear to be the variables dominating the effects of an environment on crack growth. Environments that markedly increased the crack growth rate did not produce significant corrosion attack on unstressed samples. Thus conventional high temperature corrosion tests may not be useful for predicting service performance of stressed components.     

Composition and corrosion resistance of cerium conversion films on 2195Al-Li alloy

The Ce conversion films on 2195Al-Li alloy without and with post-treatment were studied and the corrosion resistance was evalu-ated as well. The surface morphology was observed by scanning electron microscopy (SEM), and the chemical composition was characterized by X-ray photoelectron spectroscopy (XPS). The corrosion behaviors of 2195Al-Li alloy and conversion coating were assessed by means of potentiodynamic polarization curves. The experimental results indicated that after post-treatment the surface quality was improved signifi-cantly. According to XPS, the conversion coating after post-treatment was mainly composed of CeO2, Ce2O3, Ce-OH and a little MoO3 and MoO2. The results of potentiodynamic polarization curves revealed that the conversion coating with post-treatment possessed better corrosion resistance than bare alloy and Ce conversion coating without post-treatment.     

Stress corrosion cracking of alpha brass in a tarnishing ammoniacal environment: Fractography and chemical analysis

Alloy 260 brass specimens under stress were exposed at room temperature to 15 N aqueous ammonia solution with 8 g/1 of cupric copper predissolved. This environment causes tarnishing of the brass surface and intergranular stress corrosion cracking. Scanning electron microscopy, energy dispersive X-ray analysis, and Auger electron spectroscopy were employed to study fractography, corrosion product composition and distribution within the stress corrosion crack, and fracture surface chemistry characteristic of stress corrosion cracking in this system. A thin oxidized film was detected by Auger spectroscopy at the leading edge of the propagating crack. With continued exposure to the corrosive environment, deposits form on the fracture surface, then coalesce to form a continuous tarnish film that is depleted of zinc. No bulk depletion of zinc was detected in the alloy at the stress corrosion crack leading edge. No evidence of noncrystallographic crack arrest marks was found on the intergranular fracture surface.     

The effect of heat treatment on the fatigue and corrosion fatigue behavior of a CuNiCr alloy

Fatigue experiments were conducted on a CuNiCr alloy (IN838) in air and in 0.5 N NaCl solutions under conditions of free corrosion and of applied anodic currents. The alloy was heat treated to produce a solutionized structure and also to produce a precipitation hardened structure. The fatigue behavior of the solutionized alloy was unaffected by free corrosion although increased corrosion rates resulted in a decrease in fatigue resistance for small applied anodic currents. The age hardened alloy showed a decrease in fatigue resistance under free corrosion conditions and a further decrease in resistance with small applied anodic currents. In both heat treatments fatigue in air resulted in mixed transgranular-intergranular crack initiation and propagation while corrosion increased the relative amount of intergranular cracking. These results can be explained by a consideration of previously developed fatigue and corrosion fatigue models of pure copper and copper aluminum alloys. H. N. Hahn, formerly with Rensselaer Polytechnic Institute     

The effect of cathodic polarization on the corrosion fatigue behavior of a precipitation hardened aluminum alloy

Fatigue experiments were conducted on polycrystalline and monocrystalline samples of a high purity Al, 5.5 wt pct Zn, 2.5 wt pct Mg, 1.5 wt pct Cu alloy in the peak-hardened heat treatment condition. These experiments were conducted in dry laboratory air and in 0.5N NaCl solutions at the corrosion potential and at applied potentials cathodic to the corrosion potential. It has been shown that saline solutions severely reduce the fatigue resistance of the alloy, resulting in considerable amounts of intergranular crack initiation and propagation under freely corroding conditions for polycrystalline samples. Applied cathodic potentials resulted in still larger decreases in fatigue resistance and, for poly crystals, increases in the degree of transgranular crack initiation and propagation. Increasing amounts of intergranular cracking were observed when applied cyclic stresses were reduced (longer test times). The characteristics of cracking, combined with results obtained on tensile tests of deformed and hydrogen charged samples, suggest that environmental cracking of these alloys is associated with a form of hydrogen embrittlement of the process zones of growing cracks. Further, it is suggested that stress corrosion cracking and corrosion fatigue of these alloys occurs by essentially the same mechanism, but that the often observed transgranular cracking under cyclic loading conditions occurs due to enhanced hydrogen transport and/or concentrations associated with mobile dislocations at growing crack tips.     

淬火介质对高强铝合金晶间腐蚀性能的影响

对经过不同淬火介质淬火的高强铝合金的极化曲线特性和晶间腐蚀性能进行了研究。结果表明：经过空气淬火的合金在极化过程中腐蚀电流大,腐蚀速率也大;而经过20℃水淬火合金在极化过程中腐蚀电流最小,腐蚀速率最小。经过空气淬火合金抗晶间腐蚀性能最差,而经过100℃水淬火合金抗晶问腐蚀性能较好,经过20℃水淬火合金抗晶间腐蚀性能最强。     

The effect of heat treatments on the corrosion fatigue properties of 13 Pct Chromium Stainless Steel in 3 Pct NaCI Aqueous Solution

The effect of austenitizing or tempering temperature on the corrosion fatigue properties of 13 pct chromium stainless steel was studied. Three pct NaCI aqueous solution was used as the corrosive environment, and the results were compared with the atmospheric fatigue properties. Strong influence of the tempering temperature on the S-N and FCP behavior of this blading material was found. The damage ratios (corrosion fatigue limit divided by endurance limit) of these various heat treated specimens became very low by this environment. Especially, extremely low corrosion fatigue strength of the specimen tempered at 600 °C was noticed. This microstructure was strategically used to clarify the reduction of pH inside the corrosion pits which were generally formed at the fatigue crack initiation sites. FCP data in the corrosive environment showed higher resistance than the atmospheric ones at the stress intensities below 18 MPa · m^1/2, and which is opposite to the generally known influence of the corrosive environments. As for the fractographic feature, an appearance of the intergranular facets was especially noticed in NaCI aqueous solution environment. The fraction of this intergranular cracking was obtained as a function of the stress intensity factor.