Fe-Cr合金在450℃的KCl及KCCI-ZnCl2盐膜中的腐蚀

研究了Fe-10Cr,Fe-25Cr两种合金在450℃于K,Zn氯化物中的腐蚀.结果表明,与在KCI-ZnCl2熔盐中的腐蚀不同,合金无论在固态的KCl还是熔融态的KCI-ZnCl2盐膜下均发生了加速腐蚀,且在混合盐膜下的腐蚀更为严重,合金的耐蚀性不随Cr含量的增加而得到改善;Fe-Cr合金在上述两种腐蚀条件下的耐蚀性差异与氧的供应量有关,并导致保护性的氧化膜具有不同的热力学稳定性.     

CeO2薄膜对Fe-Cr合金的高温水蒸气氧化行为影响

研究了Cr含量为9 mass％和19 mass％的Fe-Cr合金表面沉积CeO2薄膜在600℃~770℃水蒸气中的氧化行为.结果表明,对9 mass％Cr含量的Fe-Cr合金,沉积稀土薄膜并没有改变氧化膜结构和明显降低氧化速率.对于19 mass％Cr含量的Fe-Cr合金,沉积稀土薄膜可促进Cr向外扩散和阻碍O向内扩散,合金表面形成连续的Cr氧化物,合金的氧化速率降低.关键词：      

喷丸对Fe-Cr合金的高温水蒸气氧化行为影响

研究了表面处理喷丸对Cr含量为9 mass％和19 mass％的Fe-Cr合金在通过600℃～770℃温度区间高温水蒸气氧化行为的影响.结果表明,喷丸工艺可降低Fe-Cr合金在高温水蒸气中的氧化速率,提高其抗高温水蒸氧化能力.对9 mass％Cr含量的Fe-Cr合金,喷丸并没有改变氧化层结构,仍为Fe氧化物;对19 mass％Cr含量的Fe-Cr合金,喷丸促进了Cr向外扩散,形成了Cr氧化物.     

Fe-Cr合金内部硫化物的电子衍射相分析

在Fe-Cr合金的高温硫化腐蚀行为研究过程中,发现有内部硫化物形成。用电子探针测定了试样横截面中Fe、Cr及S元素的浓度分布,用透射电镜电子衍射法分析了硫化物的相结构。结果表明内部硫化物形成时,其物相成分及类型与周围合金基体中的Cr含量有关,在Cr含量较低的内部硫化层外侧,形成单斜晶系的(Cr,Fe)3S4相,在Cr含量较高的内侧,形成六方晶系的(Cr,Fe)7S8相。     

晶粒细化对Fe-Cr、Ni-Cr合金氧化行为的影响

采用机械合金化法制备块体纳米晶Fe-20Cr、Ni-20Cr合金,并研究其在1000℃空气中的氧化行为.结果表明：由于晶粒细化,加快了Cr向合金表面的扩散速度,增加了活泼组元Cr氧化物的形核位置,降低了Fe-Cr、Ni-Cr合金形成单一连续Cr2O3氧化膜所需的临界Cr浓度,故机械合金化Fe-20Cr、Ni-20Cr合金氧化后形成了单一的Cr2O3外氧化膜,且氧化速率明显小于普通晶粒大小的熔炼Fe-20Cr、Ni-20Cr合金.      

Co—2Y和Co—5Y合金在600—800℃空气中的氧化行为研究

本文研究了Ｃｏ－２Ｙ与Ｃｏ－５Ｙ（原子分数,％,下同）合金在６００－８００℃空气中的氧化行为,纯Ｃｏ在三个温度下的氧化符合抛物线规律。Ｃｏ－Ｙ合金在８００℃下的氧化符合抛物线规律,而在７００℃时则接近于立方速率规律,在６００℃时Ｃｏ－２Ｙ合金氧化仍遵循立方速率规律,而Ｃｏ－５Ｙ合金则偏离立方和抛物线。Ｃｏ－Ｙ合金表面形成的氧化膜为Ｃｏ的氧化物和Ｙ２Ｏ３的混合物,Ｙ２Ｏ３的分布继承了金属间化合物相Ｃ     

Fe-Cr合金在TiO陶瓷上的润湿及其机理

Fe Cr合金对一氧化钛的润湿性能较差 ,在熔点温度下各成分的Fe Cr合金在一氧化钛上的润湿角都在 90°左右。当铬含量≤ 5 0 %时 ,Fe与TiO间存在界面反应 ,生成Fe2 Ti和Ti3 O2 。但界面反应的产生 ,并不能有效改善其润湿性。随着润湿温度的升高 ,合金的润湿性略有改善。在Fe Cr合金中添加少量的表面活性物质Si,可改善Fe Cr合金在一氧化钛上的润湿性。因为在润湿过程中Si在界面的富集 ,不仅降低了界面能和液相表面张力 ,有效改善了合金的润湿性 ,而且阻止了Fe与TiO间的界面反应 ,使反应型润湿转变为非反应型润湿。添加合金元素Si1.5 %以上 ,可使润湿角降至 2 5°左右。     

Fe-15Ce合金在H2-CO2、H2-H2S及H2-H2S-CO2气氛下的腐蚀

研究了600℃时Fe-15Ce合金在H2-CO2、H2-H2S及H2-H2S-CO2 3种气氛中的腐蚀行为，Fe-15Ce合金腐蚀后发生了Ce的内氧化或形成了复杂的腐蚀产物膜，而未出现Ce的选择性氧化或硫化，这主要是合金中存在着两相及Ce在Fe中极低的溶解度的结果。Fe-15Ce合金在本实验条件下的氧化-硫化腐蚀速度低于相同温度、压力下的纯硫化。     

Fe-Y合金在600～800℃H_2-CO_2-H_2S中的腐蚀

研究了纯Fe、纯Y、Fe-15Y和Fe-30Y合金在600～800℃高硫压(10-3Pa)-低氧压(10-19Pa于600℃或10-15Pa于700℃和800℃)混合气中的腐蚀行为.Y在600℃和700℃发生加速腐蚀,但在800℃形成的腐蚀膜有保护性.加入Y能够降低合金的腐蚀速率,但在所有条件下,合金都形成FeS最外层膜、由两金属的化合物组成的中间层和由α-Fe和Y的硫氧化物的细微混合物所组成内硫化-氧化区.Fe似以相当高的速率穿过中间层形成FeS外层.在合金/氧化膜界面内侧不产生Y的贫化现象.从Y在Fe     

Fe-Cr合金在650℃共晶(Li,K)2CO3熔盐中的腐蚀电化学阻抗谱研究

应用电化学阻抗技术并结合物相分析技术研究了合金元素Cr对Fe在 650℃ (Li,K) 2 CO3 共晶熔盐中的腐蚀行为的影响 .结果表明 ,加入 5 %和 1 0 %Cr不能改善Fe的耐腐蚀性能 ,而加入 2 0 %和 2 5 %Cr则能显著提高其耐腐蚀性能 ;Fe及Fe Cr合金腐蚀电化学阻抗谱呈双容抗弧特征 ,合金腐蚀受荷电粒子在氧化膜中的迁移控制 .提出将合金表面形成的氧化膜理想化为一电容器 ,并建立了氧化物电容与双电层电容相串联的等效电路来描述合金腐蚀的阻抗特征 .此外 ,根据所提等效电路对合金腐蚀电化学阻抗谱进行了解析 .     

High-Temperature Corrosion of Iron at 900°C in Atmospheres Containing HCl and H2O

The corrosion behavior of iron at 900°C in gas mixtures of O₂/N₂, H₂O/O₂/N₂, HCl/H₂O/O₂/N₂, H₂O/N₂, and HCl/H₂O/N₂ was observed. Parabolic oxide-scaling kinetics were observed in all cases, except HCl/H₂O/N₂ containing 2.5% HCl. This gas produced linear weight-loss kinetics caused by FeCl₂ vaporization. Lower HCl concentrations in H₂O/N₂ led to no chloride formation. In all cases, the reaction products reflected a close approach to local equilibrium between scale and gas. The presence of H₂O led to oxide-scale-surface faceting, and in the presence of free oxygen, to acceleration of the sublayer growth of FeO.     

The scaling of a Fe-20Cr alloy in H2-H2O-H2S mixtures

The scaling of an Fe-20Cr alloy has been studied in H₂-H₂O-H₂S mixtures between 973 and 1223 K. According to a simplified phase diagram, Cr₂O₃ and FeS should be the thermodynamically stable compounds in the gas mixtures chosen. The reaction followed a mixed rate law between linear and parabolic, indicating that the reaction rate at the scale-gas interface was comparable with the diffusion rate in the scale. At a constant H₂/H₂S ratio the scaling rate initially decreased slightly with increasing water-vapor pressure. A further increase of the water-vapor pressure resulted in localized sulfide formation, while the other parts of the surface were covered with a Cr₂O₃ film. Only Cr₂O₃ formed above a critical water-vapor content. Three zones could be distinguished when a sulfide scale is formed. The outer zone consisted of practically pure FeS; the intermediate zone was a solid solution of (Fe,Cr)S, partially decomposed to FeCr₂S₄ and metal during cooling; and the inner zone contained small Cr₂O₃ inclusions in an (Fe,Cr)S matrix.     

铝合金表面氧化层在燃烧气氛中的退化行为

目的通过对300、400、500℃热空气和燃烧气氛中5052铝合金表面氧化层退化行为的分析,研究基于火灾后金属材料表面产物分析来确定火场中是否存在助燃剂的方法。方法使用高温氧化实验装置对火场中的燃烧气氛进行模拟,用光学显微镜、扫描电子显微镜(SEM)、X射线衍射仪(XRD)和精密分析天平对5052铝合金在300、400、500℃空气和燃烧气氛中表面氧化物的退化行为进行研究,并对氧化物层的组织结构进行分析。结果 5052铝合金表面氧化物层与外界环境气氛和温度密切相关,在温度较低的热空气中表现出较好的抗氧化性能,表面生成的氧化物层完整致密;高温燃烧气氛使5052铝合金的氧化速度显著提高,表面生成的氧化物层结构疏松,并随时间的延长出现失稳氧化。结论火灾中铝合金表面氧化层的微观结构记录了火场的相关信息,这些信息不但是对传统残留物宏观形貌证据的有效补充,还可作为火场中是否有助燃剂存在的辅助证据使用。     

The Corrosion of Cu–Al Binary Alloys in H2/H2S/H2O Atmospheres at 400–900°C

The corrosion behavior of pure Cu and of three Cu–Al alloys containing 1, 5, and 10 wt.% Al was studied at 400–900°C in a H₂/H₂S/H₂O gas mixture. Both Cu–1Al and Cu–5Al alloys had the single-phase structure of α-Cu, while Cu–10Al was the intermetallic compound Cu₃Al. In general, the corrosion behavior of all the alloys followed the parabolic rate law, and the corrosion rate constants generally increased with increasing temperature but decreased with increasing Al content. The scale formed on pure Cu was an exclusive single layer of Cu₂S, while the scales formed on Cu–Al alloys were heterophasic and duplex, consisting of an outer layer of Cu₂S and an inner layer of Cu₂S and CuAlS₂. X-ray diffraction results showed no evidence of oxides and the amount of CuAlS₂ increased with increasing Al content. The formation of Cu₂S and CuAlS₂ on higher Al-content alloys resulted in a subsurface phase transformation from α-Cu (for Cu–5Al) or from Cu₃Al (for Cu–10Al) to Cu₃Al + Cu₉Al₄. The formation of CuAlS₂ in the inner layer of Cu–Al alloys was responsible for the reduction of corrosion rates, as compared to those of pure Cu.     

Corrosion of Three Commercial Steels Under ZnCl2 –KCl Deposits in a Reducing Atmosphere Containing HCl and H2S at 400–500°C

The corrosion of three commercial steels in a reducing atmosphere containing HCl plus H₂S in the presence of ZnCl₂–KCl deposits has been investigated at 400–500°C and compared with the corrosion of the same materials in a similar gas mixture free from H₂S. The presence of H₂S in the gas accelerated the corrosion of the three commercial steels beneath ZnCl₂–KCl deposits. All materials suffered from severe corrosion with partial detachment and spalling of the external scales. Degradation of the steels resulted from the penetration of chlorine-containing species through the scale formed initially down to the metal matrix, because chorine-rich species were detected close to the alloy/scale interface. Although the corrosion resistance generally increased with increasing Cr content, even the high-Cr stainless steel SS304 is still unable to provide good corrosion resistance against the ZnCl₂–KCl deposits in the presence of H₂S due to the bad adherence of the scales to the alloy. The mechanisms of attack are discussed on the basis of thermodynamic considerations and of the active-oxidation model.     

Sulfidation properties of Fe-Cr alloys at 1073 K in H2S-H2 atmospheres of sulfur pressures 10−2 and 10−5 Pa

An investigation is reported on the sulfidation properties of Fe-Cr alloys over their complete compositional range in H ₂ S -H ₂ atmospheres at 1073 K. Sulfidation of alloys containing less than 60 at. % Cr obeyed parabolic kinetics and alloys of larger chromium content and chromium followed linear kinetics. Scales were composed of two distinct layers: an outer columnar grained sulfide and an inner equiaxed grained sulfide layer of increased relative thickness and porosity at larger alloy chromium contents. The scales on quenched specimens were composed of either (CrFe) ₅ S ₆ or (FeCr)S plus small amounts of (FeCr) ₃ S ₄ at =10 ^–2 Pa and of (CrFe) ₅ S ₆ at =10 ^–5 Pa. Internal sulfidation was most pronounced in the high chromium content alloys and at the low sulfur pressure. The parabolic sulfidation rate at =10 ^–2 Pa was large and of practically constant value irrespective of alloy composition. These kinetics at =10 ^–5 Pa, however, increased from a very low value by three orders of magnitude as the alloy chromium content was increased from 5–60 at.%.     

Cu-20Ni-30Cr合金在700℃和800℃纯氧气中的氧化

研究了三元复相合金Cu-20Ni-30Cr（at%）在700℃和800℃纯氧气中的氧化行为，合金由三相组成，具有最大Cu浓度和最小Cr浓度的α相为合金的基体，中间浓度的Ni和Cr的β相和富Cr的γ相以颗粒状态分布在合金基体中。合金在2个温度下的氧化动力学曲线偏离抛物线规律，其氧化增重随时间延长而降低，合金氧化速率随温度升高而加快，合金形成了复杂的氧化膜结构，外层为富Cu氧化物，中间层为尖晶石层，最内层为不规则但连续的Cr2O3膜，合金中的复相组织限制Cr在合金中的扩散，抑制了外氧化膜的形成。     

Cu在Zr-2.5Nb-0.5Cu合金及其腐蚀生成氧化膜中的存在形式

用电子显微镜研究了合金元素Cu在Zr-2.5Nb-0.5Cu合金及其腐蚀生成氧化膜中的存在形式。合金基体中的元素Cu主要以四方结构的CuZr2第二相形式存在,CuZr2相中会富集杂质元素Fe。合金经过550℃,25MPa超临界水条件深度腐蚀后,伴随着合金基体发生的H致β相变,CuZr2第二相也发生了相消溶、扩散及凝聚长大过程。在腐蚀生成的氧化膜中,合金元素Cu以非晶氧化物的形式存在于氧化锆的晶界。     

用不同气氛和不同温度的氧化法制备氧化锌纳米线的研究

在不同气氛中和低于锌熔点的350～400℃温度下,在锌箔上用直接氧化法制备了氧化锌纳米线。研究表明,在400℃以下的空气中加热会形成低密度的氧化锌纳米线;在400℃空气中加热时,氧化锌纳米线的密度明显增大。当在氧气与氩气的混合气氛中于400℃加热时,氧化锌纳米线的密度也明显增大。混合气体的流量越大,氧化锌纳米线的密度越大,纳米线越直。氧化锌纳米线的晶体结构为六方晶体,直径为20～150 nm,长度为几μm至十几μm。用直接氧化法可在低温无催化剂条件下制备出纳米材料。