Microstructure and stress corrosion cracking of the fusion boundary region in an alloy 182-A533B low alloy steel dissimilar weld joint

Stress corrosion cracking (SCC) in the fusion boundary (FB) region of an Alloy 182-A533B low alloy steel (LAS) dissimilar weld joint in high temperature water doped with sulfate was studied following a microstructure characterization of the FB region. The microstructure characterization suggested the type-II and type-I boundaries in the dilution zone (DZ) adjacent to the FB had lower resistance to SCC growth than the FB. Crack propagating perpendicular to the FB in the DZ was observed to be blunted by pitting at the FB, followed by the reactivation from the pitting by localized oxidation along the grain boundary in LAS.     

The atmospheric corrosion kinetics of low carbon steel in a tropical marine environment

The atmospheric corrosion kinetics of low carbon steel exposed for up to 36 months in marine and industrial sites was studied by weight loss measurements. The results show that the mechanism and kinetics of the atmospheric corrosion process presents transition behaviour in marine environments with high chloride ion content and high relative humidity, whereas no transition appears in industrial environment. The average corrosion velocity in marine site reaches a maximum during the period of transition and then fluctuates in a certain range; however, the instantaneous corrosion velocity follows different exponential functions before and after the period of transition.     

Corrosion properties of friction-stir processed cast NiAl bronze

Friction-stir processing (FSP) was adopted to modify the microstructure of a cast Cu-9Al-4.5Ni-4Fe NiAl bronze alloy (NAB). After FSP, the initial coarse microstructure of the cast NAB was transformed to a fine structure, and the porosity defects were eliminated. The microstructure modification changed the corrosion behavior of the NAB in a 3.5% NaCl solution. In a static immersion corrosion test, the FSP NAB exhibited significantly greater corrosion resistance compared to the cast counterpart. The polarization curve and electrochemical impedance spectroscopic (EIS) results indicated that the FSP NAB showed slightly lower electrochemical corrosion resistance.     

Discontinuous oxidation and erosion-oxidation of a CeO2-dispersion-strengthened chromium coating

A CeO₂-dispersion-strengthened chromium coating was developed on a carbon steel using a two-step process: prior electrodeposition of a Ni-CeO₂ nanocomposite film and subsequent chromization using a conventional pack cementation method. Compared to the CeO₂-free coatings prepared on the carbon steel without and with pre-electrodeposition of a pure Ni film, the CeO₂ dispersed chromium coating offered profoundly improved discontinuous oxidation resistance at 900 °C in 5% O₂ + N₂ and in 5% O₂ + 1000 ppm SO₂ + N₂, and erosion-oxidation resistance in a laboratory-scale fluidized-bed combustor (FBC), mainly because of the development of a denser, less wrinkled and more adherent chromia scale.     

High temperature corrosion behaviour of a gradient NiCoCrAlYSi coating II: Oxidation and hot corrosion

The high temperature oxidation and hot corrosion behaviour of a NiCoCrAlYSi coating and a gradient coating were investigated. The gradient coating showed better performance of re-healing alumina scale due to its possession of more β phase as Al reservoir. The degradation process of the gradient coating was favorably retarded by the formation of Cr(W)-rich σ precipitates in the interdiffusion zone. The corrosion results also confirmed an improved corrosion resistance of the gradient coating. The improved high temperature performance of the gradient coating owes to the Al enrichment of Al in the outer layer.     

Effect of hydrostatic pressure on the corrosion behaviour of Ni-Cr-Mo-V high strength steel

Effect of hydrostatic pressure on the corrosion behaviour of Ni-Cr-Mo-V high strength steel was investigated by electrochemical measurements and SEM observation. The electrochemical noise (EN) data was analyzed based on non-linear dynamic theory. The experimental results revealed that hydrostatic pressure decreased the corrosion resistance of Ni-Cr-Mo-V steel and the corrosion at high hydrostatic pressure was more uniform due to the higher initiation rate and lower growth probability of metastable pitting.     

Oxidation behavior and electrical property of ferritic stainless steel interconnects with a Cr-La alloying layer by high-energy micro-arc alloying process

Chromium volatility, poisoning of the cathode material and rapidly decreasing electrical conductivity are the major problems associated with the application of ferritic stainless steel interconnects of solid oxide fuel cells operated at intermediate temperatures. Recently, a novel and simple high-energy micro-arc alloying (HEMAA) process is proposed to prepare LaCrO₃-based coatings for the type 430 stainless steel interconnects using a LaCrO₃-Ni rod as deposition electrode. In this work, a Cr-La alloying layer is firstly obtained on the alloy surface by HEMAA using Cr and La as deposition electrode, respectively, followed by oxidation treatment at 850 °C in air to form a thermally grown LaCrO₃ coating. With the formation of a protective scale composed of a thick LaCrO₃ outer layer incorporated with small amounts of Cr-rich oxides and a thin Cr₂O₃-rich sub-layer, the oxidation rate of the coated steel is reduced remarkably. A low and stable electrical contact resistance is achieved with the application of LaCrO₃-based coatings, with a value less than 40 mΩ cm² during exposure at 850 °C in air for up to 500 h.     

十七烯基咪唑啉的制备及其缓蚀性能评价

以十七烯基咪唑啉产率及其缓蚀效率为指标设计正交实验,优选出最佳制备工艺路线。采用FTIR,MS-ESI谱和紫外吸收表征咪唑啉结构及产率,以失重法为主探讨其在盐酸溶液中对Q235钢的缓蚀效率与缓蚀剂浓度、酸浸温度、酸浸时间的关系,并用SEM表征Q235钢表面腐蚀形貌。结果表明,最佳工艺条件下制备的十七烯基咪唑啉缓蚀剂在1 mol/L的盐酸腐蚀介质中对Q235钢具有优良的缓蚀性能。     

扰动溶液中模拟剥离涂层底部Q345钢阴极极化水平

利用分段电极测量了阴极保护下矩形模拟剥离涂层底部Q345钢的电位和电流分布,研究了浓度为0.5 mol/L的静态溶液及充氧动态溶液中,不同阴极保护电位、缝隙宽度以及漏点尺寸条件下缝内阴极极化水平。结果表明,充氧扰动作用减弱了缝内阴极极化水平,致使钢片在扰动溶液环境中比在静态溶液需要更高水平的阴极保护,才能有效抑制缝内金属腐蚀。缝隙宽度和漏点尺寸对充氧扰动改变缝内极化水平的影响明显。     

质子辐照对AL-6XN在高温高压水中的腐蚀行为影响

利用扫描电镜、能谱分析和X射线衍射研究质子辐照前后的奥氏体不锈钢AL-6XN在高温高压水中的腐蚀行为。结果表明,未辐照的样品在高温高压水中生成了完整的氧化膜,样品增重随着浸泡时间的增加而增加,温度越高腐蚀增重越显著。经过质子辐照后的材料在290℃/10 MPa水中氧化膜发生了严重的溶解,浸泡后样品出现了失重,在550℃/25 MPa超临界水中外层氧化膜发生了剥落,且浸泡时间越长氧化膜剥落越严重。质子辐照不影响氧化膜的元素组成和相结构,同时建议了质子辐照后奥氏体不锈钢在高温水中氧化膜剥落的模型。