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1.
The corrosion of pure Ni and of binary Ni-Ti alloys containing 5, 10, and 15 wt.% Ti respectively in molten (0.62Li,0.38K)2CO3 at 650°C under air has been studied. The corrosion of the single-phase Ni-5Ti alloy was slower than that of pure Ni, forming an external scale composed of NiO and TiO2. The two-phase Ni-10Ti and Ni-15Ti alloys underwent much faster corrosion than pure Ni, producing an external scale containing NiO and TiO2, and a thick internal oxidation zone of titanium mainly involving the intermetallic compound TiNi3 in the original alloys. The rates of growth of the external scales for the Ni-Ti alloys were reduced with the increase of their titanium content, while the internal oxidation was significantly enhanced. The corrosion mechanism of the alloys is also discussed. 相似文献
2.
The corrosion behavior of two Ni-Al alloys and four Ni-Nb-Al alloys was studied over the temperature range of 600° C to 1000° C in a mixed-gas of H2/H2O/H2S. The parabolic law was generally followed, although linear kinetics were also observed. Multiple-stage kinetics were observed for the Ni-Al alloys. Generally, the scales formed on Ni-13.5Al and Ni-Nb-Al alloys were multilayered, with an outer layer of nickel sulfide with or without pure Ni particles and a complex inner scale. The outer scale became porous and discontinuous with increasing temperature. Very thin scales formed on Ni-31Al. The reduction in corrosion rate with increasing Al content is ascribed to the formation of Al2O3 and Al2S3 in the scale. Platinum markers were found at the interface between the outer and inner scales. 相似文献
3.
The corrosion behavior of eight Fe-Nb-Al ternary alloys was studied over the temperature range 700–980°C in H2/H2O/H2S atmospheres. The corrosion kinetics followed the parabolic rate law for all alloys at all temperatures. The corrosion rates were reduced with increasing Nb content for Fe-x Nb -3Al alloys, the most pronounced reduction occurred as the Nb content increased from 30 to 40 wt.%. The corrosion rate of Fe-30Nb decreased by six orders of magnitude at 700°C and by five orders of magnitude at 800°C or above by the addition of 10 wt.% aluminum. The scales formed on low-Al alloys (3 wt.% Al) were duplex, consisting of an outer layer of iron sulfide (with Al dissolved near the outer-/inner-layer interface) and an inner complex layer of FexNb2S4(FeNb2S4 or FeNb3S6), FeS, Nb3S4 (only detected for Nb contents of 30 wt.% or higher) and uncorroded Fe2Nb. No oxides were detected on the low-Al alloys after corrosion at any temperature. Platinum markers were found to be located at the interface between the inner and outer scales for the low-Al alloys, suggesting that the outer scale grew by the outward transport of cations (Fe and Al) and the inner scale grew by the inward transport of sulfur. The scales formed on high-Al alloys (5 wt.% Al) were complex, consisting primarily of Nb3S4, Al2O3 and (Fe, Al)xNb2S4, and minor amounts of (Fe, Al)S and uncorroded intermetallics (FeAl and Fe2Nb). The formation of Nb3S4 and Al2O3 blocked the transport of iron through the inner scale, resulting in the significant reduction of the corrosion rates. 相似文献
4.
The corrosion behavior of Ni-Mo alloys containing up to 40 wt.% Mo was studied over the temperature range of 550–800C in a mixed gas of H2/H2O/ H2S. The scales formed on all alloys contained only sulfides and were doublelayered. The outer scale was single-phase Ni3S2. Depending on the alloy composition and reaction conditions, the inner scale was: (1) a mixture of MoS2 plus Ni3S2 with/without Ni, (2) MoS2, or (3) MoS2 plus intermetallic particles and/or double sulfide Ni2.5Mo6S6.7. Neither internal oxidation nor internal sulfidation were observed at lower temperatures. Internal sulfidation was however observed at higher temperature when the scale apparently melted. The parabolic law was generally obeyed for the most concentrated alloys. For the two more-dilute alloys the kinetics were mostly linear. A decrease in the corrosion rate occurred with increasing Mo content of the alloy and may be attributed to the presence of increasing volume fractions of MoS2 and/or of a double Ni-Mo sulfide in the inner region of the scale. For the two most concentrated alloys this may also be due to the presence of a number of particles of the unsulfidized intermetallic compound, which is Ni3Mo for Ni-30Mo, but NiMo for Ni-40Mo. 相似文献
5.
Ti3AlC2 suffers severe Na2SO4-induced corrosion attacks at temperatures higher than 800 °C in air. A convenient and efficient pre-oxidation method is proposed to enhance the corrosion resistance of Ti3AlC2. The corrosion weight-changes of the pre-oxidized samples were decreased by about four orders of magnitude compared with those of the untreated specimens. The mechanism on improvement of corrosion resistance was investigated by means of thermogravimetric analysis, X-ray diffraction and scanning electron microscopy/energy-dispersive spectroscopy. A continuous and adherent α-Al2O3 scale was prepared by high-temperature pre-oxidation treatment in air. The preformed dense Al2O3 scale has good compatibility with the Ti3AlC2 substrate, and consequently, can act as an efficient barrier against corrosion. Long-time corrosion tests demonstrate that the Al2O3 scale conserves after corrosion attack and is capable of long-term stability. 相似文献
6.
The corrosion behavior of seven Ni-Mo-Al alloys was investigated over the temperature range of 600–950°C in a mixed-gas atmosphere of H
2/H
2O/H
2
S. The parabolic law was followed at low temperatures, while linear kinetics were generally observed at higher temperatures. At a fixed Mo content, the transition from parabolic to linear kinetics shifted to higher temperature with increasing Al concentration. Double-layered scales generally formed on alloys having a low Al content, consisting of an outer layer of nickel sulfide and a complex inner scale. The thickness of the outer scale and the inner scale decreased as the Al content increased. The outer scale became porous and discontinuous with increasing Al content and temperature. Al
2
O
3
was detected in the scales of all alloys corroded at higher temperatures ( 800°C), even though the amount of Al
2
O
3
was very small in some cases. The decrease in corrosion rate with increasing Al content may be attributed to the formation of Al
2
O
3,Al
0.55
Mo
2
S
4,and Al
2
S
3
in the inner scale. 相似文献
7.
为了研究Cu元素对Ni基合金定向结构涂层耐腐蚀性能的影响,向Ni60合金粉末中添加了5%Cu(质量分数,下同),制备了定向结构Ni60/Cu复合涂层。采用电化学试验和浸泡试验,评估了涂层在不同浓度H2SO4溶液中的电化学腐蚀特性和浸泡腐蚀性能,探讨了涂层在不同浓度H2SO4溶液中的腐蚀行为。结果表明,涂层在不同浓度H2SO4溶液中的腐蚀均表现为活化-钝化-过钝化的过程,电化学阻抗谱在整个时间常数内具有典型的容抗特征,H2SO4溶液浓度从5%增至80%时,电荷转移电阻先减小后增大,涂层的耐腐蚀性呈现先降低后升高的趋势。随着H2SO4溶液浓度的增加,涂层表面的腐蚀程度先加剧后逐渐减缓,且在H2SO4溶液浓度为40%时,腐蚀电位移至最负,腐蚀电流密度增至最大。但在H2SO4溶液浓度达到80... 相似文献
8.
The corrosion of Fe-Mo alloys containing up to 40 wt.% Mo was studied over the temperature range 600–980C in a H2/H2O/H2S mixture having a sulfur pressure of 10–5 atm. and an oxygen pressure of 10–20 atm. at 850C. All alloys were two-phase, consisting of an Fe-rich solid solution and an intermetallic compound, Fe3Mo2. The scales formed on Fe-Mo alloys were bilayered, consisting of an outer layer of iron sulfide (FeS) and of a complex inner layer whose composition and microstructure were a function of the reaction temperature and of the Mo content of the alloys. No oxides formed under any conditions. The corrosion kinetics followed the parabolic rate law at all temperatures. The addition of Mo caused only a slight decrease of the corrosion rate. Platinum markers were always located at the interface between the inner and outer scales, indicating that outer scale growth was primarily due to outward diffusion of iron, while the inner scale growth had a contribution from inward diffusion of sulfur. 相似文献
9.
Liujie Xu Shizhong WeiJiwen Li Guoshang ZhangBaozhu Dai 《International Journal of Refractory Metals and Hard Materials》2012,30(1):208-212
The conventional molybdenum alloys, lacking of hard particles enhancing wear property, have relative poor wear resistance though they are widely used in wear parts. To resolve the above question, Mo alloys reinforced by in-situ Al2O3 particles are developed using powder metallurgy method. The in-situ α-Al2O3 particles in molybdenum matrix are obtained by the decomposition of aluminum nitrate after liquid-solid incorporation of MoO2 and Al(NO3)3 aqueous solution. The α-Al2O3 particles well bonded with molybdenum distribute evenly in matrix of Mo alloys, which refine grains of alloys and increase hardness of alloys. The absolute density of alloy increases firstly and then decreases with the increase of Al2O3 content, while the relative density rises continuously. The friction coefficient of alloy, fluctuating around 0.5, is slightly influenced by Al2O3. However, the wear resistance of alloy obviously affected by the Al2O3 particles rises remarkably with the increasing of Al2O3 content. The Al2O3 particles can efficiently resist micro-cutting to protect molybdenum matrix, and therefore enhances the wear resistance of Mo alloy. 相似文献
10.
The corrosion behavior of 11 Fe-Mo-Al ternary alloys was studied over the temperature range 700–980°C in H2/H2O/H2S mixed-gas environments. With the exception of Fe-10Mo-7Al, for which breakaway kinetics were observed at higher temperatures, all alloys followed the parabolic rate law, despite two-stage kinetics which were observed in some cases. A kinetics inversion was observed for alloys containing 7 wt.% Al between 700–800°C. The corrosion rates of Fe-20Mo and Fe-30Mo were found to be reduced by five orders of magnitude at all temperatures by the addition of 9.1 or higher wt.% aluminum. The scales formed on low-Al alloys (5 wt.% Al) were duplex, consisting of an outer layer of iron sulfide (with some dissolved Al) and a complex inner of Al0.55Mo2S4, FeMo2S4, Fe1.25Mo6S7.7, FeS, and uncorroded FeAl and Fe3Mo2. Platinum markers were always located at the interface between the inner and outer scales for the low-Al alloys, indicating that outer-scale growth was due mainly to outward diffusion of cations (Fe and Al), while the inner scale was formed primarily by the inward flux of sulfur anions. Alloys having intermediate Al contents (7 wt.%) formed scales that consisted of FeS and Al2O3. The amount of Al2O3 increased with increasing reaction temperature. The high-Al-content alloys (9.1 and 10 wt.%) formed only Al2O3 which was responsible for the reduction of the corrosion rates. 相似文献
11.
The corrosion behavior of Ni-Nb alloys containing up to 40 wt.% Nb was studied over the temperature range of 550–800°C in a mixed H2/H2O/H2S gas. The scales formed on all alloys were multilayered. The outer scale was single-phase Ni3S2, while the structure and constitution of the inner scale depended on alloy composition and reaction conditions. Internal oxidation has been found in Ni-20Nb and Ni-30Nb, external oxidation has been observed on Ni-34Nb. Platinum markers were located at the interface between the outer scale and inner scale. The decrease in corrosion rate with increasing Nb content may be attributed to the presence of increasing amounts of Ni-Nb double sulfides as well as to the presence of Nb2O5 in the inner region of the scale. 相似文献
12.
High-purity nickel has been reacted with 96% O2+4% SO2 at 700–900°C. The reaction has been studied at 700°C as a function of the total gas pressure (0.06–1 atm) and at 1 atm as a function of temperature (700–900°C). The reaction mechanism changes with the effective pressure of p(SO3) in the gas. When NiSO4 (NiO + SO3 = NiSO4) is formed on the scale surface, the scale consists of a two-phase mixture of NiO + Ni3S2; in addition, sulfur is enriched at the metal/scale interface. A main process in the reaction is rapid outward diffusion of nickel through the Ni3S2 phase in the scale; the nickel reacts with NiSO4 to yield NiO, Ni3S2, and possibly NiS as an intermediate product. When NiSO4 cannot be formed, the scale consists of NiO, and small amounts of sulfur accumulate at the metal/scale interface. It is proposed that the reaction under these conditions is primarily governed by outward grain boundary diffusion of nickel through the NiO scale, and in addition, small amounts of SO2 migrate inward through the scale—probably along microchannels. 相似文献
13.
The corrosion behavior of pure Nb and three Nb Al alloys containing 12.5, 25, and 75 at.% Al was studied over the temperature range of 800–1000°C in a H2/H2S/H2O gas mixture. Except for the Nb-12.5Al alloy consisting of a two phase structure of -Nb and Nb3Al, other alloys studied were single phase. The corrosion kinetics followed the parabolic rate law in all cases, regardless of temperature and alloy composition. The parabolic rate constants increased with increasing temperature, but fluctuated with increasing Al content. The Nb-75Al alloy exhibited the best corrosion resistance among all alloys studied, whose corrosion rates are 1.6–2.2 orders of magnitude lower than those of pure-Nb (depending on temperature). An exclusive NbO2 layer was formed on pure Nb, while heterophasic scales were observed on Nb-Al alloys whose compositions and amounts strongly depended on Al content and temperature. The scales formed on Nb-12.5Al consisted of mostly NbO2 and minor amounts of Nb2O5, NbS2, and -Al2O3, while the scales formed on Nb-25Al consisted of mostly Nb2O5 and some -Al2O3. The scales formed on Nb-75Al consisted of mostly -Al2O3 and Nb3S4 atT 900°C, and mostly -Al2O3 , Nb3S4 and some AlNbO4 at 1000°C. The formation of -Al2O3 and Nb3S4 resulted in a significant reduction of the corrosion rates. 相似文献
14.
利用高温高压CO2腐蚀模拟实验以及ESEM, EDS, XPS和SEM等分析技术, 研究了4种不同含Cr量的X65管线钢的腐蚀速率、腐蚀形态和腐蚀产物膜结构特征. 结果表明: 含Cr量高的钢平均腐蚀速率小, 无Cr和含1\%Cr的钢的腐蚀形态为局部腐蚀, 含3%和5%Cr的钢的腐蚀形态为全面腐蚀. 在高温高压CO2腐蚀环境中, 含Cr钢的腐蚀产物膜为FeCO3和Cr(OH)3竞争沉积形成的多层结构, 其中1Cr-X65和3Cr-X65的腐蚀膜具有3层结构, 5Cr-X65的腐蚀膜是双层结构. Cr在腐蚀产物膜层中出现局部富集, 远高于基体中的Cr含量. 高含Cr量使腐蚀产物膜中的Cr(OH)3含量高, 并提高了腐蚀膜的保护性能, 从而引起腐蚀形态发生转变, 腐蚀速率降低. FeCO3和Cr(OH)3共沉积层膜对低铬钢的抗CO2腐蚀性能具有关键的影响. 相似文献
15.
The oxidation of two NiNb alloys containing 15 and 30 wt% Nb has been studied at 600–800 °C in pure oxygen under 1 atm O2 at 600–800 °C. The scales formed on both alloys under all conditions show an external scale, generally duplex, containing an outermost layer of nearly pure NiO and an innermost region of NiO mixed with the double NiNb oxide NiNb2O6. Moreover, the samples corroded at all temperatures also show a region of internal oxidation composed of a mixture of alpha nickel and niobium oxides (Nb2O5 or/and NbO2), which formed from both alloy phases Ni8Nb and Ni3Nb. No important depletion of niobium was observed in the alloy close to the interface with the zone of internal oxidation, while the depth of this region is generally much higher than measured for the corrosion of the same alloys under low oxygen pressures at the same temperatures. The corrosion mechanism of these alloys is examined with special reference to the effects of the low solubility of niobium in nickel. 相似文献
16.
Polycrystalline Ti3SiC2 suffered from serious hot corrosion attack in the mixture of 75wt.%Na2SO4 + 25wt.%NaCl melts at 850 °C. In order to improve the hot corrosion resistance of this material, pre-oxidation treatment was conducted at 1200 °C in air for 2 h. A duplex oxide scale with an outer layer of TiO2 and an inner layer of a mixture of TiO2 and SiO2 was formed during the pre-oxidation. Because the outer oxide layer of the pre-oxidation treated specimens could inhibit hot corrosion process, they exhibited good hot corrosion resistance in the mixture of 75wt.%Na2SO4 + 25wt.%NaCl melts at 850 °C for 50 h. However, during the hot corrosion the outer layer of TiO2 would degrade gradually. Once the outer layer damaged, the hot corrosion rate increased sharply, the corrosion behavior was similar to Ti3SiC2 corroded under the same conditions. The microstructure and phase compositions of the hot corrosion samples were investigated by SEM/EDS and XRD. 相似文献
17.
J.G. Gonzalez-Rodriguez E. Mejia V.M. Salinas-Bravo A. Martinez-Villafañe 《Corrosion Science》2009,51(8):1619-1627
A study of the effect of lithium content (1, 3 and 5 wt.%) and heat treatment (400 °C during 144 h) on the corrosion behavior of Ni3Al alloy has been carried out in a 62 mol.%Li2CO3-38 mol.%K2CO3 mixture at 650 °C using electrochemical techniques. Employed electrochemical techniques included potentiodynamic polarization curves, linear polarization resistance, LPR, electrochemical impedance spectroscopy, EIS, and electrochemical noise, measurements EN. Results have shown that the alloys exhibited an active-passive behavior regardless of the heat treatment. For alloys without heat treatment, the most corrosion resistant was the Ni3Al base alloy, but when they were heat treated, the most corrosion resistant was the alloy containing 3%Li. EIS results showed that for short immersion tests, the corrosion process was under diffusion control, but for longer exposure times, the presence of a protective scale was evident. All the alloys were highly susceptible to a localized type of corrosion according to EN measurements and supported by SEM micrographs. 相似文献
18.
The corrosion of three Fe-xCr alloys (x = 8, 12, 18 wt.%) was examined at 600 °C in reducing atmospheres containing HCl and H2S with two different H2S contents and compared with the behavior of the same materials in H2S-free H2-CO2 and H2-HCl-CO2 mixtures producing similar oxygen and chlorine pressures. Exposure to the low-H2S gas mixture had only a reduced effect on the behavior of Fe-8Cr and Fe-18Cr, but increased significantly the corrosion rate of Fe-12Cr. Increasing the H2S level accelerated the corrosion of all the alloys, but particularly that of Fe-18Cr. In both cases only minor amounts of sulfur and chlorine were present close to the alloy/scale interface. An increase of the Cr content reduced the corrosion rate in both H2S gas mixtures, especially in the range 8-12 wt.% Cr, due to a larger volume fraction of Cr2O3 in the scale. The results have been discussed on the basis of the thermodynamic stability diagrams of the Fe-O-Cl-S and Cr-O-Cl-S systems. 相似文献
19.
采用高温高压实验设备辅以失重法,研究了CO2/H2S腐蚀环境中P110钢的腐蚀性能,用SEM、EDS和XRD等分析了腐蚀产物.分别用电化学充氢及NACE TM0177A法对P110钢进行耐氢损伤试验.结果表明,虽然P110钢在试验环境中的均匀腐蚀速率很小,未发生点蚀,但随着充氢量的增加,强度、伸长率及断面收缩率均降低.... 相似文献
20.
通过化学镀再电化学氧化的方法在铜片表面制备出带有微米微坑和微米微球的均一NiO/Ni(OH)2和B参杂的NiO/Ni(OH)2(B)两种电极材料,采用扫描电镜(SEM/EDX)、X射线衍射(XRD)、X射线光电子能谱(XPS)和电化学技术对所制备的两种电极材料进行表征和电化学性能测试。SEM、XRD和XPS的测试结果表明, 所制备的两种电极材料由Ni、NiO和Ni(OH)2组成,并且NiO/Ni(OH)2(B)中B的参杂量可达14.6wt%。循环伏安测量和恒电流充放电试验表明,两种电极材料均具有较高的电化学活性和可逆性;在1 A/g的充放电电流密度下, 两种NiO/Ni(OH)2和NiO/Ni(OH)2(B)电极材料经历10000次充放电循环后分别给出了1380 和1930F/g的比电容, 显示出较高的比电容特性和良好的电化学稳定性;电化学阻抗谱表明NiO/Ni(OH)2(B)电极材料较NiO/Ni(OH)2电化学反应电阻降低了约2个数量级;Ragone曲线揭示了所制备的两种电极材料具有较高的功率密度和较低的能量密度。B的参杂使得NiO/Ni(OH)2(B)电极材料表面氧化物含量增大并且形成微米微球形貌,增大了电极表面积以及与电解液的接触和润湿作用,降低了电极材料表面能带带隙能,从而导致较小的电化学反应电阻和电导率的提高是其显示优异赝电容性能的主要原因。 相似文献