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排序方式: 共有813条查询结果,搜索用时 625 毫秒
81.
渐开线齿轮点蚀成因新释 总被引:2,自引:0,他引:2
对现有点蚀成因的理论作了评述,并根据流体力学润滑原理分析了齿面下剪应力的分布规律。最后据此对点蚀成因及所表现的特点进行了新的解释。 相似文献
82.
W. Ensinger O. Lensch Th. Kraus Ch. Sundermann B. Enders 《Surface & coatings technology》2002,150(2-3):227-231
Tubes are often required to exhibit better performance in corrosion and wear behavior than the material the tube is made of can offer. The situation can be improved when the tube is coated with a protective film. This can be achieved by sputter coating with an ion beam. A sputter target is located inside the tube. Energetic ions are accelerated into the tube and impinge onto the target. Thus, material is sputtered from the target onto the inner walls of the tube. Two apparatus for coating tubes of different lengths and diameters are described. Aluminum and stainless steel tubes were coated with amorphous carbon films. Results on adhesion, corrosion performance in aqueous media and thickness uniformity are shown. 相似文献
83.
In engineering storage sites for Carbon Sequestration the CO2-induced corrosion of injection pipe steels is a relevant safety issue when emission gasses are compressed in deep geological layers. The reliability of the steels suitable for the geological onshore CCS-site (Carbon Capture and Storage) at Ketzin, Germany, is demonstrated in laboratory experiments in equivalent corrosive environment (T = 60 °C, p = 1-60 bar, aquifer water, CO2-flow rate of 3 L/h, 700-8000 h exposure time). Corrosion kinetics and microstructures were characterized using specimens of the heat treated steel 42CrMo4 (1.7225) used for casing, and specimens of the martensitic stainless injection-pipe steel X46Cr13 (1.4034). 相似文献
84.
溶液pH值与氯离子对青铜腐蚀的影响 总被引:6,自引:0,他引:6
青铜文物在大气中的腐蚀实质上是金属表面在水膜下的电化学过程,故可以用电化学方法进行研究。青铜的阳极极化曲线表明青铜是一种弱纯化金属,在含氯离子和含氧气的溶液中容易发生点蚀。 相似文献
85.
Bangyi CHEN Chenghao LIANG Daojun FU School of Chemical Engineering Dalian University of Technology Dalian China State Key Laboratory for Corrosion Protection Shenyang China 《材料科学技术学报》2005,21(2):226-230
Electrochemical test technology and surface analysis method were employed to investigate the pitting corrosion of Cu-Zn-AI shape memory alloy in simulated uterine fluid. The results showed that the breakage of the breaking-renovating equilibrium of surface layers resulted in the pitting corrosion of Cu-Zn-AI shape memory alloy in simulated uterine fluid. The development of pitting corrosion was controlled by dissolution of surface layers. The critical pitting corrosion potential was 1.70 VSCE. The kinetics equation for the development of pitting corrosion for Cu-Zn-AI shape memory alloy in simulated uterine fluid was io=465.68 t-0.5+1.5. Pitting appearances of pits could be two types: tortoise-shell, and anomaly abscess. Cl- ion facilitated the pitting corrosion of Cu-Zn-AI shape memory alloy by competing adsorption and concentrating on alloy surface at high positive potential. 相似文献
86.
Effect of aluminum on microstructure, mechanical properties and pitting corrosion resistance of ultra-pure 429 ferritic stainless steels has been investigated. Aluminum can significantly increase the ratio of equiaxed crystal grains, but the promotion effect has great relation with aluminum content. Aluminum can stabilize ferrite phase and significantly reduce recrystallization temperature. Increased aluminum content can also lead to the precipitate of AlN and Al2O3 at higher temperature. The increased amount of AlN may partly contribute to the reduced nitrogen element to form austenite at high temperature, hence the high temperature phase transformation of α + γ → α occurs. The fine and large number of Al2O3 particles can refine grain size and then promote recrystallization. The highest intensity of γ-fiber texture {1 1 1}〈1 1 2〉 is observed in the steel with 0.19 wt.% aluminum, which can improve the formability of steels. With the increase of aluminum content, the tensile strength increases linearly but the elongation and plastic strain ratio first increase then decrease, the working hardening index varies slightly among the steels. Appearance of Al2O3 inclusions with small size and decreased content of MnS benefit pitting corrosion resistance. However, the large dimension Al2O3 inclusions have significantly negative influence on pitting corrosion resistance. 相似文献
87.
The corrosion susceptibility of as-received reinforcing steel bars (rebars) in solutions simulating the pore liquid of alkaline and carbonated concrete has been studied by means of potentiodynamic polarisation tests and polarisation resistance measurements. The effect of different degrees of carbonation and the presence of several chloride contents in the simulated pore solutions was investigated. Results show the beneficial effect of high alkalinity on the localised corrosion of steel caused by chloride ions. From the results of the potentiodynamic tests a critical chloride concentration above which pitting could take place was evaluated for each solution. The chloride threshold values here found are of the same order than those previously reported in the literature for film-free steel. The results obtained in solutions simulating carbonated concrete showed that under weak carbonation conditions carbon steel does not passivate while in the presence of high levels of carbonate and bicarbonate the resistance to localised corrosion is improved. 相似文献
88.
The effect of microstructure on corrosion behaviour of an Al-5.4 wt% Ni alloy fabricated by equal-channel angular pressing (ECAP) was investigated by means of potentiodynamic polarization test. The Al-5.4 wt% Ni alloy samples were severely deformed by ECAP with two strain introduction methods of route A and route BC and the ECAP process was repetitively carried out up to 6 passes (strain 6). The anodic polarization measurements indicated that pitting potential of the ECAPed Al-Ni alloy samples in chloride containing neutral buffer solution increased with ECAP passes. The pitting corrosion resistance of Al-Ni alloy after ECAP by route BC was better than that by route A. It is attributable to that the size of α-Al crystal region was reduced with ECAP passes and route BC was able to obtain more homogeneous α-Al/Al3Ni structure than route A. On the other hand, pitting corrosion resistance of pure Al samples showed an obvious declining with increasing ECAP passes. It was indicated that more homogeneous and finer α-Al/Al3Ni structure obtained by ECAP played a vital role on improving the corrosion resistance of Al-5.4 wt% Ni alloy. 相似文献
89.
自然海水中低合金铸铁点蚀的化学-电化学溶解机理 总被引:4,自引:0,他引:4
根据自然海水中低合金铸铁试验结果,在蚀坑内受扩散和迁移控制的质量传输、化学溶解和电化学溶解的基础上,建立自然海水中铸铁点蚀的化学-电化学溶解模型,并推导出蚀坑内电压分布的方程式。此式表明,蚀坑内的电压取决于蚀坑内各类活性腐蚀因子的化学势梯度和相应粒子的电压降。试验结果表明,自然海水中铸铁表面钝化膜的诱发期的局部破坏与海生物的局部附着和生物粘膜下R(R=wCl-wOH-)值密切相关,在其蔓延生长过程中,蚀坑内外的电压降、蚀坑内活性粒子的活度和pH值密切相关。但自然海水中的卤素离子的存在和摩尔分数对铸铁点蚀影响最大。 相似文献
90.
Hamdy H. Hassan 《Electrochimica acta》2005,51(3):526-535
The corrosion behaviour of steel was studied in aerated near neutral citrate solutions without and with various concentrations of NaCl. The potentiodynamic anodic polarization curve in 0.1 M citrate solution exhibits four anodic peaks A1, A2, A3 and A4 prior to the oxygen evolution reaction. Addition of Cl− ions to the solution enhances the four peaks currents, specially A3, which is followed by pitting corrosion. The negative going scans of the cyclic voltammograms show two anodic reactivation peaks A5 and A6 and one cathodic plateau P1. A diffusion controlled process in the potential range of A1, A2 and P1 was detected by RDE experiments. The potentiostatic current time transients, at different concentrations of NaCl and applied potentials Ea > A3, were studied. The pit nucleation rate (ti−1) is found to increase with increasing the concentration of NaCl and the applied anodic potential. The impedance spectra exhibit four different behaviours depending on the potential range used. They were fitted with a single time constant circuit at Ea < −700 mV. However, at −700 mV < Ea < −480 mV, they were fitted with a circuit with two time constants. At Ea > −480 mV, the second semicircle is replaced by negative polarization resistance which is disappeared at Ea > −300 mV. The electrode impedance was found to decrease with the applied potential. 相似文献