304不锈钢晶间腐蚀的研究

实验使用化学腐蚀法对304不锈钢进行晶间腐蚀测定,通过在不同的腐蚀条件下对304不锈钢进行侵蚀,并进行金相拍照,利用SPSS软件进行了蚀刻宽度数据的统计分析,采用K-S单样本检验分析晶间腐蚀沟槽宽度的统计特性。结果表明:304不锈钢在稀硫酸溶液中的晶间腐蚀沟槽宽度符合正态分布;敏化热处理会加重304不锈钢的晶间腐蚀程度,晶间腐蚀沟槽宽度随敏化热处理时间增长而增大。     

汽轮机转子钢晶间腐蚀沟槽宽度的统计特征研究

用化学腐蚀法对30Cr2MoV汽轮机转子钢进行晶间腐蚀测定,测出晶间腐蚀沟槽宽度。对沟槽宽度进行正态分布、对数正态分布、威布尔分布的统计拟和检验。统计检验方法采用柯尔莫哥洛夫一斯米尔诺夫（K—S）检验法检验。检验结果表明：晶间腐蚀沟槽宽度服从对数正态分布和威布尔分布。     

316L奥氏体不锈钢厚板焊接工艺及接头性能研究

根据316L奥氏体不锈钢的焊接性,制定了316L厚板的焊接工艺,采用钨极氩弧焊和焊条电弧焊的组合焊接工艺对316L厚板进行了焊接,并对焊接接头进行了力学性能、金相检测和晶间腐蚀试验。结果表明,所获得的焊接接头无缺陷,力学性能合格,焊缝组织为奥氏体和少量δ铁素体,焊接接头无晶间腐蚀倾向。焊接工艺合理,满足316L奥氏体不锈钢厚板焊接生产要求。     

轻水堆核电站—回路管道事故分析及对策

对由应力腐蚀裂纹引起的轻水堆核电站—回路管道事故作了分析,提出了相应的对策:开发了核能用316LN不锈钢:制定了降低焊接残余应力和防止焊接热影响区组织敏化的四种施工方法:管内壁堆焊法;管内面水冷焊接法;焊后固溶热处理法和高频加热残余应力改善法.这样即可基本上解决管道晶间应力腐蚀问题.     

用化学腐蚀法检测老化30Cr2MoV汽轮机转子钢热脆化程度的研究

根据试验用30Cr2MoV汽轮机转子钢化学成分和材料性能等特点,尝试了用硝酸和醋酸的混合液作为蚀刻液对老化汽轮机转子钢进行化学腐蚀实验.得到腐蚀晶界沟槽宽度与韧脆转变温度(FATT50)的关系,并讨论了影响FATT50的其它影响因子.用MINITAB软件对影响FATT50的所用参数进行多元线性全回归分析,建立了FATT50的预测模型.用预测模型计算各钢样的FATT50,所得FATT50的预测值与测量值之间的误差范围在±15℃之内,预测精度较高.     

承压式热水器不锈钢内胆的腐蚀与防护

端盖环焊缝及其附近区域的腐蚀是承压式热水器不锈钢内胆失效的主要形式,其腐蚀失效主要表现为点腐蚀、晶间腐蚀及缝隙腐蚀。本文结合不锈钢材质、热水器内胆的成形及焊接工艺、端盖与筒体结合处的结构设计等几方面分析了不锈钢材料腐蚀失效的主要原因,并提出晶间腐蚀、缝隙腐蚀等常见腐蚀失效形式的预防措施。     

垃圾焚烧环境中典型材料的腐蚀性研究

模拟垃圾焚烧炉内环境,在550℃条件下,开展了T91、TP347H、TP347HFG、TP310S、UNS 6625等材料的腐蚀实验研究。采用减重法和壁厚法分别计算腐蚀速率,利用光学显微镜和配有能谱仪的扫描电镜对试样件腐蚀后的形貌结构、元素含量进行分析。结果表明:垃圾焚烧炉中积灰腐蚀严重,可采用改善受热面清洁状况及优化受热面材质的方法减轻;在相同条件下,镍基合金材料UNS 6625由于其氧化物在氯化物熔盐中的热稳定性好,腐蚀速率小,耐腐蚀性好,可用于垃圾焚烧炉中的高温部位;不锈钢材料表面的晶粒细化后,能有效改善材料的抗腐蚀性能;在工程现场,壁厚法仅适用于无晶间腐蚀的材料,不适用于不锈钢材料;不锈钢材料的腐蚀情况判断应将晶间腐蚀考虑在内,并结合SEM-EDS分析。     

杂质氯离子对新型四元硝酸盐腐蚀性的影响

为了探究低氯离子含量（0.01%~0.05%,质量分数）对熔盐与金属材料腐蚀过程的影响,该文采用失重法研究316L不锈钢与氯离子质量分数为0.01%、0.03%、0.05%的混合硝酸盐的腐蚀行为。结果发现,在经过360 h的腐蚀实验后,316L不锈钢在氯离子质量分数为0.03%的熔盐中具有最小的失重量,其为0.4381 mg/cm²。采用SEM、EDS、XRD等方法对316L不锈钢表面形貌进行分析,结果表明,在添加氯离子后不锈钢的腐蚀产物中出现Ca（OH）₂,在Ca（OH）₂的形成过程会消耗氢氧根离子,从而降低了不锈钢失重量。     

城轨车用不锈钢薄板焊接接头抗晶间腐蚀性能的试验研究

对城市轨道车辆选用的SUS304和SUS301L不锈钢薄板分别进行了MAG电弧焊和电阻点焊工艺试验,并参照GB/T4334.3—2000标准对SUS304钢MAG焊接头和SUS301L钢点焊接头进行了晶间腐蚀试验。试验结果表明,选用合适的MAG焊工艺,焊态下的接头与母材抗腐蚀速率相当。经过700℃×2h敏化处理后,接头的腐蚀速率明显增加;点焊接头的腐蚀速率与母材相当,点焊参数对接头腐蚀性能的影响不大。     

In元素对Sn-Bi-Zn传热储热合金高温容器相容性的影响

合金材料与容器壳体的相容性是影响传热储热系统使用寿命的重要因素之一.本文选用前期开发的Sn-Bi-Zn系传热储热合金,添加In元素进行改性,研究700℃下液态合金对20碳钢、304不锈钢、316不锈钢结构材料的腐蚀作用.实验采用恒温全浸泡腐蚀法,通过扫描电子显微镜(FE-SEM)和EDS光谱仪分析腐蚀前后合金基体和容器...     

Evaluation of material degradation in in-service high temperature structural component by a chemical etching test

An etching test using a picric acid solution with a wetting agent was found to have great potential for the nondestructive evaluation of grain boundary embrittlement caused by phosphorus segregation in both CrMo and CrMoV steels, and by carbide or sigma phase precipitation in austenitic stainless steel. A line pipe (CrMo) and a steam turbine rotor (CrMoV) were tested on-site to demonstrate whether the etching test would be a useful tool. The ΔFATT value estimated by the etching test agreed reasonably well with the ΔFATT determined by an electrochemical method for the turbine rotor steel. A good correlation was found between the degree of intergranular corrosion and the material deterioration of SUS316 stainless steel used as a superheater of a fossil fuel boiler.     

Influence of fluoride ions on corrosion performance of 316L stainless steel as bipolar plate material in simulated PEMFC anode environments

Corrosion performance of 316L stainless steel as a bipolar plate material in proton exchange membrane fuel cell (PEMFC) is studied under different simulated PEMFC anode conditions. Solutions of 1 × 10⁻⁵ M H₂SO₄ with a wide range of different F⁻ concentrations at 70 °C bubbled with hydrogen gas are used to simulate the PEMFC anode environments. Electrochemical methods, both potentiodynamic and potentiostatic, are employed to study the corrosion behavior. Scanning electron microscope (SEM) and atomic force microscope (AFM) are used to examine the surface morphology of the specimen after it is potentiostatic polarized in simulated PEMFC anode environments. X-ray photoelectron spectroscopy (XPS) analysis is used to identify the compositions and the depth profile of the passive film formed on the 316L stainless steel surface after it is polarized in simulated PEMFC anode environments. Mott–Schottky measurements are used to characterize the semiconductor passive films. The results of potentiostatic analyses show that corrosion currents increase with F⁻ concentrations. SEM examinations show that no localized corrosion occurs on the surface of 316L stainless steel and AFM measurement results indicate that the surface topography of 316L stainless steel becomes slightly rougher after polarized in solutions with higher concentration of F⁻. From the results of XPS analysis and Mott–Schottky measurements, it is determined that the passive film formed on 316L stainless steel is a single layer n-type semiconductor.     

Chromium nitride/Cr coated 316L stainless steel as bipolar plate for proton exchange membrane fuel cell

Chromium nitride/Cr coating has been deposited on surface of 316L stainless steel to improve conductivity and corrosion resistance by physical vapor deposition (PVD) technology. Electrochemical behaviors of the chromium nitride/Cr coated 316L stainless steel are investigated in 0.05 M H₂SO₄ + 2 ppm F⁻ simulating proton exchange membrane fuel cell (PEMFC) environments, and interfacial contact resistance (ICR) are measured before and after potentiostatic polarization at anodic and cathodic operation potentials for PEMFC. The chromium nitride/Cr coated 316L stainless steel exhibits improved corrosion resistance and better stability of passive film either in the simulated anodic or cathodic environment. In comparison to 316L stainless steel with air-formed oxide film, the ICR between the chromium nitride/Cr coated 316L stainless steel and carbon paper is about 30 mΩ cm² that is about one-third of bare 316L stainless steel at the compaction force of 150 N cm⁻². Even stable passive films are formed in the simulated PEMFC environments after potentiostatic polarization, the ICR of the chromium nitride/Cr coated 316L stainless steel increases slightly in the range of measured compaction force. The excellent performance of the chromium nitride/Cr coated 316L stainless steel is attributed to inherent characters. The chromium nitride/Cr coated 316L stainless steel is a promising material using as bipolar plate for PEMFC.     

Effect of substrate material on the corrosion of TiN-coated stainless steels in simulated anode and cathode environments of proton exchange membrane fuel cells

A physical vapor deposition (PVD) TiN coating has been used to increase the corrosion resistance of two stainless steel materials for bipolar plate application in proton exchange membrane fuel cells (PEMFCs). Our earlier studies had shown that a TiN coating on SS410 and SS316L increased the corrosion resistance of SS410 and SS316L significantly. In this study, we examine how the substrate affects the corrosion of TiN-coated stainless steel in the simulated anode and cathode environments. Potentiodynamic and contact resistance test results show that the polarization resistance and contact resistance of TiN-coated SS410 and TiN-coated SS316L are almost the same. However, in the simulated anode condition, the corrosion current density of TiN-coated SS410 is positive and the corrosion current density of TiN-coated SS316L is negative. Inductively coupled plasma optical emission spectrometry (ICP-OES) test results also show that the metal ion concentration is much higher for TiN-coated SS410 at the anode side. At the cathode side, the potentiostatic and ICP-OES tests show that the corrosion of TiN-coated SS410 and TiN-coated SS316L are in the same range. Therefore, the substrate has an effect on corrosion in the simulated anode working conditions of PEMFCs. In order to be the suitable bipolar plate materials, both the coating and substrate need to have a higher corrosion resistance.     

Thermal nitridation of chromium electroplated AISI316L stainless steel for polymer electrolyte membrane fuel cell bipolar plate

The electrical and corrosion properties of surface-nitrided AISI316L stainless steel are evaluated to assess the potential use of this material as a bipolar plate for a polymer electrolyte membrane fuel cell. Chromium is electroplated on the surface of the AISI316L stainless steel before nitridation. The nitriding condition is selected so as to form Cr₂N nitride only and the result is compared with that of a CrN + Cr₂N nitride coating. The stainless steels with the Cr₂N nitride protective coating layer exhibit better interfacial contact resistance and corrosion resistance than the as-rolled or (CrN + Cr₂N)-coated AISI316L stainless steels.     

Stress corrosion cracking behaviour of 316L stainless steel exposed to CO2–H2S–Cl− environments in the absence and presence of methyldiethanolamine (MDEA)

Stress corrosion cracking (SCC) behaviour of 316L stainless steel in CO₂–H₂S–Cl^? environments with and without methyldiethanolamine (MDEA) was investigated by slow strain rate testing and scanning electron microscopy (SEM). The results show that elongation ratio, reduction in area ratio (RAR) and time to failure ratio (TTFR) of 316L stainless steel were low in CO₂–H₂S–Cl^? environments. The corresponding fractography exhibited flat brittle fracture with quasi-cleavage pattern, indicative of high SCC susceptibility. Hydrogen penetration and corrosion pits could be responsible for the high SCC susceptibility of 316L stainless steel in this condition. For the CO₂–H₂S–Cl^? environments in the presence of MDEA, 316L stainless steel possessed high ER, RAR and TTFR (nearly 100%). High SCC resistance of 316L stainless steel could be associated with MDEA induced removal of H₂S/CO₂ and absorption on the steel surface.     

Corrosion of metals and salt hydrates used for thermochemical energy storage

Solar energy can be efficiently used if thermal energy storage systems are accordingly designed to match availability and demand. Thermal energy storage by thermochemical materials (TCM) is very attractive since these materials present a high storage density. Therefore, compact systems can be designed to provide both heating and cooling in dwellings. One of the main drawbacks of the TCM is corrosion with metals in contact. Hence, the objective of this study is to present the obtained results of an immersion corrosion test following ASTM G1 simulating an open TCM reactor, under humidity and temperature defined conditions. Four common metals: copper, aluminum, stainless steel 316, and carbon steel, and five TCM: CaCl₂, Na₂S, CaO, MgSO₄, and MgCl₂, were studied. Aluminum and copper show severe corrosion when combined with Na₂S, aluminum corrosion is more significant since the specimen was totally destroyed after 3 weeks. Stainless steel 316 is recommended to be used as a metal container material when storing all tested TCM.     

Improved corrosion resistance and interfacial contact resistance of 316L stainless-steel for proton exchange membrane fuel cell bipolar plates by chromizing surface treatment

The electrochemical performance and electrical contact resistance of chromized 316 stainless-steel (SS) are investigated under simulated operating condition in a proton-exchange membrane fuel cell (PEMFC). The corrosion resistance of the chromized stainless steel is assessed by potentiodynamic and potentiostatic tests and the interfacial contact resistance (ICR) is examined by measuring the electrical contact resistance as a function of the compaction force. The results show that the chromizing surface treatment improves the corrosion resistance of the stainless steel due to the high-chromium concentration in the diffuse coating layer. On the other hand, the excess Chromium content on the surface increases the contact resistance of the steel plate to a level that is excessively high for commercial applications. This study examines the root cause of the high-contact resistance after chromizing and reports the optimum process to improve the corrosion resistance without sacrificing the ICR by obtaining a chrome carbide on the outer layer.