The effect of Acetobacter sp. and a sulfate-reducing bacterial consortium from ethanol fuel environments on fatigue crack propagation in pipeline and storage tank steels

This paper evaluates the effects of microbiologically influenced corrosion (MIC) on fatigue-crack growth of candidate materials useful in expanding bio-ethanol usage, including a storage-tank steel (ASTM A36) and two pipeline steels (API 5L X52 and X70). The microbiological species sampled and cultivated from an ethanol fuel production stream are responsible for both acetic acid and hydrogen sulfide production that lead to significant increases in fatigue-crack growth rate across a wide range of stress-intensity-factor amplitudes (ΔK). The mechanism for increased fatigue damage is hydrogen uptake through adsorption into the steel, which embrittles material ahead of the growing fatigue crack.     

Effect of partial replacement of carbon by nitrogen on intergranular corrosion behavior of high nitrogen martensitic stainless steels

The microstructure evolution and intergranular corrosion (IGC) behavior of high nitrogen martensitic stainless steels (MSSs) by partial replacing C by N were investigated by using microscopy, X-ray diffraction, nitric acid tests and double-loop electrochemical potentiokinetic reactivation (DL-EPR) tests. The results show that the partial replacement of C by N first reduces and then increases the size and content of precipitates in high nitrogen MSSs, and converts the dominant precipitates from M₂₃C₆ to M₂N, furthermore first improves and then deteriorates the IGC resistance. The high nitrogen MSS containing medium C and N contents provides good combination of mechanical properties and IGC resistance.     

Effect of Cl~- Concentration on the SCC Behavior of 13Cr Stainless Steel in High-Pressure CO_2 Environment

An effect of Cl-concentration on the stress corrosion cracking(SCC) behavior of 13 Cr stainless steel was investigated by employing electrochemical measurements and the slow strain rate tensile tests.These tests were conducted in various solutions with different concentrations of NaCl at 90℃under 3 MPa CO_2 with 3 MPa N_2.The results indicate that the passive film of the specimen formed in the 10% NaCl solution has the best protective effect on the matrix.The SCC susceptibility does not increase with increasing the chloride ion concentration,the lowest SCC susceptibility occurs when the NaCl concentration is 10%,and the specimens show higher SCC susceptibility in the 5% NaCl and 20% NaCl solutions.     

Influence of microstructure on the chemical inhomogeneities in nanostructured longitudinal magnetic recording media

Energy-filtered transmission electron microscopy and spectrum imaging at nanometer spatial resolution were used to correlate microstructure, specifically crystallographic texture and grain-boundary character, with the chemical inhomogeneities in sputtered CoCrPtB thin-film media. These data show that the average Cr grain boundary segregation is reduced in the sputtered CoCrPtB material with a strong (1 1 0)_Co texture compared to a microstructure with a weak (1 0 0)_Co texture.     

海洋工程结构与船舶的腐蚀防护——现状与趋势

船舶与海洋工程装备具有高技术、高投入、高产出、高附加值、高风险的特点,同时也要求高安全性和高可靠性。船舶与海洋工程结构主要采用金属材料。在海洋环境这种高腐蚀环境中长期服役的金属材料必须采取腐蚀防护措施。文章概述了目前我国海洋工程结构和船舶的腐蚀现状,介绍了目前采用的腐蚀防护技术的现状与问题,包括常用的多种涂料(油漆)、包覆技术、电化学保护(牺牲阳极和外加电流阴极保护技术)以及表面处理技术、缓蚀剂、结构健康监测与检测、寿命评价与可靠性评估等。指出了各类技术的发展趋势,例如以涂料为例,追求高固体份、无(弱)溶剂化、水性化、无重金属化、高性能化、多功能化、低表面处理化、节省资源化、智能化、低成本是涂料发展的国际趋势。提出了我国应该采取的措施和建议。     

Tensile properties and microstructures of Al composite reinforced with BN particles

Al–4.5 wt% Mg alloys reinforced with and without BN were fabricated by pressureless infiltration method and then their tensile properties and microstructures were analyzed. Since the spontaneous infiltration of molten metal occurred at a temperature of 800 °C for 1 h under nitrogen atmosphere, it was possible to fabricate the Al composites reinforced with BN and control alloy without BN. A large increase in strength in the case of the control alloy is related to the in situ formation of AlN particles as well as grain size refinement. In the composite reinforced with BN, additional AlN was formed by the interfacial reaction of the BN and Al melt as well as AlN by the in situ reaction. In addition, the grain size in the composite reinforced with 7.5 vol% BN further decreased to about 4.0 μm and exhibited approximately 3.5 times reduction in the grain size of the commercial alloy. Consequently, a further strengthening in the composite resulted from both the BN artificially added and AlN formation (by the in situ reaction and interfacial reaction) and grain refinement.     

纳米复合海洋涂料在船舶防腐蚀应用研究

主要研究纳米二氧化硅浓缩浆和纳米氧化锌浓缩浆对海洋环氧涂料和聚氨酯涂料性能的影响。通过盐雾试验、氙灯老化试验、人工海洋加速老化试验研究海洋腐蚀环境中纳米复合涂料的耐腐蚀性和抗老化性。通过三步法制备高稳定分散的纳米氧化物浓缩浆,并利用纳米二氧化硅浓缩浆和纳米氧化锌浓缩浆改性海洋船舶环氧底漆和聚氨漆酯船壳漆,制备海洋纳米复合涂料。利用 TEM透射电镜、 FTIR红外光谱、 XPS光电子能谱、光泽度仪、表面接触角测试仪和粘结强度测试仪等研究海洋船舶漆的耐腐蚀性、抗老化性及表面防污性能。纳米二氧化硅浓缩浆的红外光谱分析和粘度测试及纳米氧化锌浓缩浆的透射电镜观察表明高分子分散剂的长碳链位阻效应保证了纳米粒子的均匀稳定分散。不含有纳米二氧化硅浓缩浆的环氧漆粘结强度是4.4 MPa,而含有1.0％纳米二氧化硅浓缩浆的环氧漆粘结强度增加到5.6 MPa。通过氙灯老化试验测试涂层的光泽度变化,纳米复合聚氨漆酯漆的光泽度高于不含纳米氧化锌的普通聚氨漆酯漆光泽度。聚氨漆酯漆在海洋循环加速老化试验后 C/O值减少20.1％,而含有1.2％纳米氧化锌浓缩浆的纳米复合聚氨漆酯漆老化后 C/O 值仅减少10.7％,抗氧化性提高。通过对海洋加速循环老化试验中纳米复合聚氨漆酯漆的测试分析表明1.2％纳米氧化锌浓缩浆提高了海洋船舶聚氨酯面漆的抗老化性和表面接触角。纳米浓缩浆可增强纳米复合涂料在海洋重腐蚀环境中耐腐蚀、抗老化等性能。