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41.
镍阳极氧化膜形成和破坏过程的光电化学响应 总被引:2,自引:0,他引:2
测定了镍表面阳极氧化膜在pH=8.4硼砂-硼酸缓冲溶液中不同电位下的光电流响应。基于阻抗测量结果的计算表明,钝化膜的平带电位和载流子密度分别为-0.68V和1.3×10(20)cm(-3)。对钝化膜和高价氧化膜在形成、生长和破坏过程中的光电流变化进行了现场监测。 相似文献
42.
The performance of cemented carbide inserts coated with various PVD-films in milling Inconel 718 is evaluated by innovative analytical and experimental methods. Three PVD films with different micro and macro structures were applied. The coatings’ strength properties were detected by nanoindentations and by impact tests at various temperatures. These results were considered in FEM calculations of the material removal process to determine the mechanical and thermal loadings of the cutting wedge. Employing this innovative methodology, it is possible to capture proactively the effect of the cutting conditions on tool wear, thus reducing the effort dedicated in traditional sequential cutting experimentation. 相似文献
43.
Electroplated CBN grinding wheels are manufactured with a single layer of abrasive grains. The grinding performance of these plated wheels changes significantly as the wheel wears down. The present investigation was undertaken to understand the transient grinding behavior with electroplated CBN wheels in order to provide a logical basis for process control. In this paper, particular attention is directed to the effect of wheel wear and operating parameters on grinding of a nickel alloy. Wheels were worn to various stages and then used to perform grinding tests under various grinding conditions to measure grinding forces and power and to produce ground specimens. Based on models for grinding with conventional aluminum oxide wheels, a power model for grinding of a nickel alloy with plated CBN wheels was established and validated. Microscopic observations of the ground specimens reveal that thermal damage in the form of a White Etch Layer (WEL) appears only when grinding with a worn wheel under conditions that lead to high temperatures. 相似文献
44.
E.E Abd El Aal 《Corrosion Science》2003,45(4):759-775
The effect of Cl−, Br− and I− anions as aggressive agents on the anodic behaviour of nickel electrode in deaerated Na2B4O7 solutions have been investigated by galvanostatic polarization technique. Lower concentrations of the halide anions have no effect on the mechanism of nickel passivation. An increase in the halide anions concentration causes oscillation of the potential in the oxygen evolution region. This could be attributed to the destruction of the passivity by halide anions and repassivation of the film by anodic current and/or OH− anions. Higher aggressive anion concentrations cause breakdown of the passive film and initiated pitting corrosion. As the temperature increases, the breakdown potential is shifted towards the more negative direction. On the other hand, as the pH of the solution increases, the breakdown potential is shifted toward more positive direction, indicating increased protection of the passive film. The activation energy, , of the oxide film formation in the presence of Cl− anions was calculated and was found to be 21 kJ/mol. 相似文献
45.
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47.
碳在Ni-Cr-W铸造高温合金中作用的研究 总被引:2,自引:0,他引:2
采用真空感应炉、金相显微镜、扫描电镜及X射线衍射等手段 ,研究 115 0℃下C对Ni Cr W高温合金的组织和高温强度的影响。结果表明 ,随C含量增加 ,合金中的碳化物数量逐渐增加 ,形状由小块状、岛状逐步变为连续、半连续网状 ;合金的高温蠕变能力随C含量增加逐渐下降 ,下降到一定值C(w )为 0 .3%后 ,又逐渐上升 相似文献
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49.
Yuuzou Kawahara 《Corrosion Science》2002,44(2):223-245
Corrosion products on two typical materials, SA213-T12 steel and alloy 625 exposed to the actual combustion gas, were analyzed in addition to laboratory tests for penetration of corrosive matter. It has been clarified that corrosion products of oxides containing a little chlorides and sulphides show lamellar structures and that at the alloy-scale interface, chlorination, sulphidation, and oxidation occur under a low PO2-high PCl2 condition. The formation of scale structures and the effect of corrosion-resistant alloying elements can be explained according to the stability tendencies of metals, chlorides, and oxides in the M-Cl-O equilibrium diagrams. The severity of corrosion environments at the interface is influenced by the penetration extent of corrosive matters through deposits and scales, and the protective effects of oxide films derived from alloying elements play an important role in preventing the corrosion. On the other hand, it has been shown that thermal fluctuation characterized in this kind of environment makes the lamellar scale structures and sometimes breaks and peels off the scale, and thus accelerates the corrosion. On the basis of the above mentioned knowledge, a new corrosion model is presented. 相似文献
50.
Nanocrystalline Ni3Al was fabricated through mechanical alloying of elemental powders and spark plasma sintering. The nanocrystalline Ni3Al has a nearly full density after being sintered at 1223 K for 10 min under a pressure of 65 MPa. Isothermal and cyclic oxidations of nanocrystalline Ni3Al were tested at 1173–1373 K with intervals of 100 K. The results indicate that nanocrystalline Ni3Al exhibits excellent isothermal and cyclical oxidation resistance. The oxide scales consist primarily of dense and continuous -Al2O3. The grain refinement is beneficial for improving the oxidation resistance of Ni3Al by providing more nucleation centers for the Al2O3 formation, promoting the selective formation of Al2O3 and improving the adhesion of oxide scales to the matrix. 相似文献