Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract: The corrosion performance of Ni free and Mn alloyed high nitrogen austenitic stainless steels (HNSSs), including uniform corrosion, intergranular corrosion, crevice corrosion, pitting corrosion and repassivation,was investigated by means of immersion test and electrochemical test. The effect of cold work and sensitization treatment on the microstructure, characteristic of passive film and corrosion resistance of the HNSSs was examined. It was found that the solution-annealed (SA) HNSSs had much weaker resistance to uniform- and intergranular- corrosion compared to the SA 316LSS. The sensitization- treatment (ST) hardly affected the uniform corrosion resistance of all the steels, but resulted in rapid degradation of the resistance to intergranular-corrosion, especially for the Mo free HNSSs. The SA HNSSs had a better resistance to crevice- and pitting- corrosion than the SA 316LSS, in particular the Mo bearing HNSSs. The ST degraded the resistance to crevice- and pitting-corrosion of the HNSSs. The cold work degraded the pitting-corrosion resistance of the HNSSs in chloride- containing solutions through thinning the passive film and decreasing the stable oxides in the passive film, but it improved the repassivation ability of the HNSSs. The ST-induced precipitation of χ phase degraded the corrosion resistance and repssivation ability of the HNSSs, and such degradation became aggravated with increasing cold work degree. Furthermore, the relevant corrosion mechanism is also discussed.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract: Pure Al plates were exposed in different atmospheres for 12 months at three typical test sites respectively: i.e. a rural site at Xishuangbanna of Yunnan province, an industrial site at Jiangjin of Sichuan province and a coastal site at Wanning of Hainan province. Then the corroded Al plates were characterized by means of EIS technique and SEM. The results indicate that the corrosion resistance of pure Al is the worst in the coastal atmosphere, the best in the rural atmosphere and the middle in the industrial atmosphere. Different thick layers of corrosion products were formed on Al surface in the rural and industrial atmosphere. In the contrast, a few corrosion products were formed dispersedly in the coastal atmosphere. The rate controlling step may be the diffusion of corrosive ions for the corrosion process in the coastal atmosphere, while the charge transfer for those in the rural and industrial atmospheres.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: none
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: none
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: none
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《材料研究学报》
Abstract: Nano-flake barium phosphate was prepared by hydrothermal synthesis, and then the effect of which as pigment on the corrosion behavior of epoxy coating was investigated by means of electrochemical impedance spectroscopy (EIS) and salt spray tests. The results show that the nano-flake barium phosphate in the epoxy coating can react with iron oxide, the corrosion product of metal substraste, to generate an insoluble FePO4 as a barrier on the corrosion spot, thereby to enhance the corrosion resistance of the coating; Among others, an epoxy coating with 5 mass% nano flake barium phosphate shows the highest corrosion resistance.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《材料研究学报》
Abstract: Polyurethane coatings with two kinds of sillitin, i.e. M type and Z type sillitin respectively as filler were prepared and sprayed on hot dip galvanized steel sheets. The coatings exhibited better mechanical properties than the simple polyurethane coating, i.e. the wear resistance and the hardness of the polyurethane coating may be enhanced by 57.1% and 14.5%, as well as 85.7% and 41.8% for the addition of M type and Z type sillitin respectively. The coatings with the two types of sillitin exhibited also better corrosion resistance. The reason is that two types of sillitin are of a special structure composed of micro- sized granular silica and nano- flake kaolin clay, and the sillitin possesses high amount of nanoflake, which may be beneficial to the enhancement of the permeation resistance and mechanical properties of the coatings.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract: The corrosion behaviour of low alloy steel containing Ni and Cu was studied because it is a promising candidate canister material for the disposal of high-level radioactive waste (HLW) in China. Due to the intensely radioactive nature of HLW, the waste has to be prevented from reaching the biosphere for many tens of thousands of years. Deep geological disposal is now considered to be the most preferable option for isolating HLW and it relies on series of natural and engineered barriers, e.g. a metallic canister. However, as soon as the waste package is settled, groundwater would seep back slowly through the outer barriers and ultimately arrive at the surface of the canister. Accordingly, there comes the groundwater-induced dissolution of the canister and subsequent transport of radionuclides through the barriers. That is to say, the effectiveness of radionuclide retention and isolation depends mostly and finally on the corrosion resistance of metallic canisters in deep groundwater environments. In this work, the test solution is deaerated 0.1 mol/L NaHCO3+0.1 mol/L NaCl, simulating the deep groundwater environment. The evolution of corrosion of NiCu low alloy steel in the test solution was investigated by electrochemical measurments. XRD was used to illustrate the composition of formed corrosion products. SEM was used to observe the electrode surface morphology and the cross section of the rust layer. The electrochemical results showed that low alloy steel has a lower corrosion rate and is less prone to localized corrosion than low carbon steel. In order to understand the mechanism of alloying elements, EDS and EPMA were used to analyse the distribution of alloying elements cross-sectional. XPS and E-pH diagram were used to estimate the possible existence form of alloying elements. By means of EDS and EPMA, it was founded that Ni is concentrated in the inner rust layer while the enrichment of Cu is not so obvious. XRD, XPS and E-pH results indicated that Ni and Cu are existed in the form of NiFe2O4 and CuFeO2 respectively.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract: The service degradation and life assessment of key components in light water reactor nuclear power plants (NPPs) mainly depend on the accumulation of service property data of component materials, understanding of environmental degradation mechanism, and construction of evaluation models or methods. The current ASME design fatigue code does not take full account of the interactions of environmental, loading and material's factors. In the present work, based on the corrosion fatigue tests in simulated NPPs' high temperature pressurized water, the environmental fatigue behavior and dominant mechanism of nuclear-grade low alloy steel have been investigated. A design fatigue model was constructed by taking environmentally assisted fatigue effects into account and the corresponding design curves were given for the convenience of engineering applications. The process for environmental fatigue safety assessment of NPPs' components was proposed, based on which some tentative assessment cases have been given.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract: The atmosphere in many cities along the coastal lines such as Qingdao in China has been polluted with SO2 due to the development of industry, and the atmosphere therefore has been changed to coastal-industrial atmosphere. The corrosion behavior and mechanism of steels in coastal-industrial atmosphere with the co-existence of SO2 and Cl- are different from that in the coastal atmosphere containing only Cl- or the industrial atmosphere containing only SO2. In addition, pH value is diverse in different coastal-industrial atmosphere. However, there are only few researches on the effect of pH value on the corrosion evolution of steels in the coastal-industrial atmosphere. Almost all the atmospheric corrosion data of steels were obtained by the field exposure test, which could not reflect the dependence of the atmospheric corrosion evolution of steels on pH value due to the difficulties in controlling the field conditions. In this work, the effect of pH value on the corrosion evolution of Q235B steel in the simulated coastal-industrial atmospheres has been investigated by the dry/wet cyclic corrosion test (CCT), XRD and EIS. The results indicate that, when the content of SO2 is lower, changing pH value has no effect on the corrosion of the steel. When the content of SO2 is higher, the corrosion rate of Q235B steel influenced by changing pH value shows an extreme phenomenon, that is, when the pH value being a certain value between the "higher" and the "lower", the corrosion rate of Q235B steel reaches the maximum value. When the SO2 content is certain, changing pH value almost has no effect on the rust composition. To some extent, the existence of SO2 inhibits the formation of b-FeOOH. With the increasing of SO2 content, the relative contents of b-FeOOH and g-FeOOH are decreasing, and g-FeOOH maybe reduced back to Fe3O4 or transform to a-FeOOH. With the corrosion process prolongs, the rust evolution shows almost the same trend. In addition, when the content of SO2 in the simulated coastal-industrial atmosphere is lower, the Q235B steel mainly follows Cl- corrosion mechanism, and the influence of pH value on corrosion behavior of the steel is not obvious. When the content of SO2 is higher, the Q235B steel also follows Cl- corrosion mechanism in the early stage; with prolonging the dry/wet cyclic corrosion test number, H2SO4 regeneration mechanism accelerates corrosion of the steel as the effect of SO2 on corrosion increasing significantly.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract: The electropolished (EP) alloy 690TT samples were first oxidized in the simulated B and Li containing primary water with 2.5 mg/L H2 at 325 ℃ and 15.6 MPa for 720 h, and then half of the samples were continuously immersed in this solution with 2.0 mg/L O2 for another 720 h. The microstructures and chemical composition of the oxide films formed under the above two conditions were analyzed. The results show that the dual layered oxide film formed under the single hydrogen water chemistry is mainly composed of spinel oxides. The outer layer is composed of big oxide particles rich in Ni and Fe and the underlying loose needle-like oxides rich in Ni. The inner layer is continuous Cr-rich oxides. The oxide film formed on EP alloy 690TT under the hydrogen/oxygen water chemistry also shows a dual layered structure. The surface morphology and chemical composition of the outer layer are similar to the oxide film formed under the hydrogen water chemistry. However, the inner layer is changed to the nano-sized NiO. The stable phase region in the potential-pH diagram for the Ni oxides is enlarged by the later dissolved oxygen. As a result, the oxygen promotes the fast growth of the outer needle-like oxides rich in Ni. Further, the oxygen promotes the dissolution of the inner Cr-rich oxides formed under the hydrogen water chemistry and increases the corrosion rate of the EP alloy 690TT. Electropolishing treatment can not reduce the corrosion rate of alloy 690TT in the simulated primary water with sequentially dissolved hydrogen and oxygen.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract: High level radioactive waste (HLW) is an extremely dangerous by-product of the global nuclear industry. Due to its intensely radioactive nature and ultra long half-life, HLW has to be safely managed and disposed for thousands of years, isolated from the biosphere. Deep geological repository (DGR) is considered to be the most feasible option worldwide because of its operability, stability, durability, environmental protection and so on. Basically, DGR relies on a multibarrier system and it consists of metallic canisters, backfill materials and a stable geologic formation. Since radionuclides could be moved into the biosphere by action of groundwater, both the geologic formation and backfill materials have to be of very low hydraulic permeability and metal canisters have to be corrosion resistant and prevent contact between the groundwater and the radioactive waste for as long as possible. Low carbon steel has been selected and studied as a candidate canister material in many countries because its long industrial experience, high-strength, low cost and it is less prone to localized corrosion than materials that passivity, but its larger corrosion rate may also set an insuperable barrier for the practical application. Recently, our studies revealed that NiCu low alloy steel is a more promising candidate for the canister material compared with the popular one, low carbon steel, since the former performs a more acceptable corrosion rate without increasing much cost and has better resistance to localized corrosion in environments with high concentration of Cl- . In this work, effects of SO42-, another ubiquitous species in deep groundwater, on the corrosion behavior of NiCu low alloy steel during immersion in simulated deep groundwater environments were investigated by in situ electrochemical measurements and surface analysis techniques. Results show that the addition of SO42- can promote the substrate dissolution during the initial stage of immersion. In the later stage, SO42- weakens the protectiveness of formed films and consequently, active dissolution prevails on the electrode surface rather than the prepassivation. Concentrated SO4 2- and HCO3 - can both promote the formation of Fe6(OH)12CO3. The main components of corrosion products are a-FeOOH, Fe3O4 and Fe6(OH)12CO3, and uniform corrosion is observed.
Subjects: Materials Science >> Materials Science (General) submitted time 2017-11-21 Cooperative journals: 《金属学报》
Abstract:采用2 MeV质子束在360 ?C对国产核用304不锈钢试样进行了辐照实验,利用显微硬度仪,透射电子显微镜(TEM)和三维原子探针(3DAP)等研究了材料的辐照损伤,分析了辐照剂量对辐照损伤演化的影响规律。结果表明,304不锈钢辐照损伤微观结构以位错环和少量孔洞为主,位错环的数量密度为1022 m-3量级,平均尺寸小于10 nm。材料在晶界和位错环处发生元素偏析,其中Cr、Ni在晶界和位错环处偏析程度相近,而Si在位错环处的偏析程度数倍于晶界。位错环平均尺寸和数量密度、晶界偏析程度以及辐照硬化程度均随辐照剂量增加而增加,并在3-5 dpa范围内趋于饱和。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-15 Cooperative journals: 《金属学报》
Abstract:利用多种分析手段深入分析了Inconel690TT和Incoloy800MA合金管材及其在高温高压水环境中腐蚀行为。结果表明,沿管材厚度方向从内壁至外壁,Inconel690TT合金管材∑3晶界偏离理想晶界的程度逐渐增大,KAM应变水平也逐渐增大,管材外壁为最薄弱区;Incoloy800MA合金管材∑3晶界偏离理想晶界的程度均匀,且主要集中于0-1o的小偏差范围内,KAM应变水平的变化也趋于平缓。溶氧的高温纯水中,Inconel690TT合金表面腐蚀产物为双层膜结构,外层为富Fe尖晶石与NiO小颗粒,内层膜为NiO相且疏松多孔,不能对基体起到良好的保护作用,局部区域腐蚀深度可达716 nm;Incoloy800MA合金表面腐蚀产物为双层膜结构,外层为颗粒状尖晶石相,内层膜为粉状多晶尖晶石相。相同条件下,溶氧的高温纯水中Incoloy800MA合金的内层膜厚度显著小于Inconel690TT合金,平均腐蚀深度仅为150 nm左右。结果表明,在溶氧高温高压纯水环境中Incoloy800MA合金相比于Inconel690TT合金耐蚀性更优。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-14 Cooperative journals: 《中国腐蚀与防护学报》
Abstract:本文利用划伤技术研究了690TT合金在325℃高温含氧硼锂水中的裂纹萌生和生长情况. 试样的表面和截面显微分析结果表明,划伤沟槽底部局部萌生了典型的沿晶应力腐蚀裂纹. 由于应力集中,在慢速率拉伸阶段划伤沟槽底部产生了机械裂纹,而机械裂纹成为恒载过程中690TT合金沿晶应力腐蚀裂纹萌生和生长的先导. 尖端接近晶界或者沿着晶界的机械裂纹可继续出现沿晶应力腐蚀裂纹. 690TT合金在恒载荷条件下对应力腐蚀开裂仍有一定的敏感性.
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-14 Cooperative journals: 《中国腐蚀与防护学报》
Abstract:本文围绕应力腐蚀行为的实验研究方法、影响因素以及应力腐蚀机制的理论分析等几个方面综述了核电结构材料应力腐蚀研究的现状,讨论了研究中亟待解决的问题,指出了研究的发展方向与趋势。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-12 Cooperative journals: 《中国腐蚀与防护学报》
Abstract:通过2年现场大气暴露实验,利用金相显微镜和扫面电子显微镜等手段分析试样表面和截面形貌,研究了U弯受力状态下包铝与无包铝的LY12和LC4两种铝合金在我国西部盐湖大气环境中的腐蚀行为。结果表明,包铝的两种铝合金的腐蚀主要发生在包铝层,以点蚀为主,未观察到包铝层被腐蚀穿透。无包铝的铝合金试样都发生了明显的沿晶应力腐蚀开裂,其中LY12铝合金在拉应力和压应力下都有较多的应力腐蚀裂纹,LC4铝合金只在拉应力下观察到了裂纹;两种铝合金在压应力下都发生了剥层腐蚀,拉应力下受到了抑制。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-04 Cooperative journals: 《金属学报》
Abstract:在HCO3-浓度为0.08mol/L,不同浓度配比的SO42-和Cl-混合溶液中,用循环极化的电化学测试方法和扫描电子显微镜的观察手段,对Cu工作电极的循环极化行为和点蚀表面形貌进行了系统的研究。结果表明,SO42-和Cl-促进Cu的阳极溶解。Cl-降低Cu电极的腐蚀电位,增强其电化学活性。在点蚀敏感区域图中,Cu发生点蚀的临界Cl-浓度为0.02mol/L。当Cl-为低浓度时,SO42-对点蚀敏感性无影响。当Cl-为中浓度时,SO42-抑制点蚀。当Cl-为高浓度时,SO42-先提高后降低点蚀敏感性。无论SO42-浓度的高低,Cl-都能促进点蚀。蚀坑的自催化效应受阴离子影响较大。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-04 Cooperative journals: 《金属学报》
Abstract:轻水堆核电站关键设备的服役损伤与寿命评价主要基于其材料性能数据的积累、环境失效机制的理解和评价模型或方法的构建。目前广泛应用的ASME疲劳设计曲线并未充分考虑环境、载荷、材料交互作用的影响。本文通过模拟核电高温高压循环水腐蚀疲劳试验,研究了核级低合金钢环境疲劳损伤规律与控制机理,构建了一个植入环境效应的疲劳设计模型,给出了便于工程应用的环境疲劳设计曲线,并建立了核电站实际构件的环境疲劳安全评估流程,给出了尝试实施例。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-04 Cooperative journals: 《金属学报》
Abstract:NiCu低合金钢是极具应用前景的高放废物地质处置罐的候选材料。本文对其在模拟深层地下水环境,即除氧0.1 mol/L NaHCO3 + 0.1 mol/L NaCl溶液中,原位监测NiCu低合金钢在长时间浸泡条件下的开路电位变化曲线及阻抗谱的演化,研究电极表面的腐蚀演化规律,并与相同条件下低碳钢的腐蚀行为进行比较。结果表明,NiCu低合金钢在本实验溶液中的耐蚀性要显著优于低碳钢,尤其是其耐局部腐蚀的能力。合金元素Ni富集在内锈层中,可能以NiFe2O4的形式存在,而合金元素Cu的富集不明显,可能的存在形式考虑为CuFeO2。