Electroplating of Copperorganic Coatings from Perchlorate and Chloride Baths Containing ε-Caprolactam

The mechanisms of reactions, which occur both in solution and at the electrode during copper plating from perchlorate and chloride baths in the presence of -caprolactam capable of electrochemical polymerization are studied. It is shown that the formation of complexes by additive molecules with metal ions in the bulk of solution enhances its inhibiting effect and improves the quality of Cu-organic coatings. Complex formation also favors the increase in the adsorption of anions at the electrode. By varying the concentration of -caprolactam, it is possible to control the deposition rate and the composition and properties of the coatings.     

Control of the phase composition and nitrogen content in the nitride layer in the nitriding of the steel 38Kh2MYuA

It is known that in order to obtain a high-hardness, wear- and corrosion-resistant article a nitrided layer of nitride (+)-phases should be formed on its surface. However, in some cases, for example, in nitriding high-speed die steels and steel 38Kh2MYuA, the formation of brittle nitride surface layers should be eliminated and only a zone of internal nitriding (a+ + MN) should be formed in order to provide the requisite hardness and wear resistance. The article concerns preparation of nitrided layers with different compositions on the widely used 38Kh2MYuA nitralloy.     

Dose-Response Functions as Estimates of the Effect of Acid Precipitates on Materials

This paper presents a brief summary of the findings of the 8-year exposure program of the European Economic Commission, United Nations (UN EEC), on estimating the effect of acid precipitates on materials, including historical and cultural monuments. Presented and discussed are dose-response functions for structural metals and alloys (bronze, copper, weathering steel, zinc, aluminum, nickel and tin), stone materials (limestone and sandstone), paint coatings and glasses. The effects of dry and wet precipitates are discriminated and expressed as separate doze-response functions. The corrosion damage to the majority of materials is most of all aggravated by dry precipitates of sulfur dioxide, while copper and tin suffer concurrently from ozone. In the equations the term pertaining to the dry precipitates includes a complex temperature effect. Unlike the correlations obtained upon four years of tests, the new functions include an exposure time parameter which enables one to calculate the corrosion rate at any period of time and to estimate the service life of the object at a given critical rate of corrosion.     

Interdiffusion Behavior of Ni–Cr–Al–Y Coatings Deposited by Arc-Ion Plating

Ni–Cr–Al–Y coatings were deposited on the Ni3Al–base superalloys IC-6 and K17 by arc-ion plating. The results indicated that a small amount of substrate atoms, such as Co, Ti, Mo, etc., existed in the Ni–Cr–Al–Y coatings near the substrates, probably due to sputter and antisputter. For the alloy K17, the impeding effect of Al was not obvious, because the temperatures of the substrate and the coating were high (420–480°C) during the deposition process and interdiffusion was accelerated. However, for alloy IC-6 which contains Al, as well as a high concentration of Mo, the diffusion of Cr was impeded. Vacuum heat treatment at 1050°C drastically increased diffusivities and the presence of Al and Mo was not enough to prevent some Cr diffusion. Thus, the coating became more uniform and close to the desired composition.     

Influence of the Anion Nature and the Metal-to-Additive Ratio on the Effectiveness of ε-Caprolactam during Cadmium Electrodeposition

The rate and mechanism of cadmium(II) electroreduction from electrolytes containing -caprolactam were found to significantly depend on the metal-to-additive ratio. Whatever the anion nature, the process sharply accelerates in the presence of an excess of cadmium cations, which form activated surface complexes with adsorbed -caprolactam molecules as bridging ligands. With an excess of the additive, metal depolarization due to the "-effect still persists in perchlorate media; in iodide solutions, -caprolactam inhibits this process. The formation of a dense adsorbed film composed of -caprolactam molecules and I^– anions at the electrode ensures a high throwing power of the electrolyte and makes it possible to obtain uniform elastic organocadmium plating.     

Improvement of cyclic high-temperature corrosion resistance of pack-aluminized heat-resistant stainless steels

Modification of pack aluminizing for heat-resistant stainless steels was studied to improve corrosion resistance by controlling the microstructure of the coating layer. The major process parameters examined include the pack powder composition, coating time, and temperature. Depending on the combination of these parameters, the microstructure of the coating layer can be controlled to form either a continuous layer of internal-diffusion barrier (IDB) or an interdiffusion zone (IZ). At the coating-process temperatures, the IDB forms as a mixture of - and -aluminide, whereas the IZ forms as a mixture of -ferrite and -aluminide. But the phase shown in the IZ at room temperature is formed by transformation from the phase during cooling. Even though the hardness of the IDB is higher than the other phases present in the coating layer, the aluminide coating layer with the IDB shows outstanding cyclic high-temperature corrosion resistance. As long as the stable IDB forms, the corrosion resistance increases with the thickness of the aluminide-coating layer.     

Exfoliation corrosion of aluminum alloys and their protection by coatings with metal-filled primers

Exfoliation corrosion (EC) is shown to represent a special type of stress corrosion which develops under the surface of aluminum high-alloyed alloys like 16T and B95T1. Protection against EC by using common paint coatings (PCs) is ineffective. Indoor tests demonstrate that EC can be almost completely suppressed by using PCs with zinc-filled primers (ZFPs). After 2-year tests in sea tropics, common PCs do not prevent the appearance and development of EC. At the same time, samples protected by PCs that involve ZFP EP-057 demonstrate the total absence of EC including bare surface areas up to 5 and even 10 mm wide where the coating has failed. Similar results are obtained in 6-year tests in north sea atmosphere. Potentiodynamic studies of different protection schemes confirm the electrochemical protection mechanism of aluminum alloys against EC by using ZFPs. It is shown that ZFPs can also be used during maintenance works. The advantages of metal-filled primers based on polyurethane over those based on epoxy resin are shown.Translated from Zashchita Metallov, Vol. 41, No. 1, 2005, pp. 40–51.Original Russian Text Copyright © 2005 by Sinyavskii, Kalinin, Gladyshev, Yakimova.     

Marine Corrosion Tests of Galvanic Coatings for Ship Instruments. XI. Gold and Palladium Coatings on Brass

The corrosion peculiarities and the protective and decorative characteristics of gold and palladium coatings were investigated in containers simulating the casings for ship's equipment of watertight and splashproof types. The coatings (3 and 6 m thick) were applied to 62 brass specimens either directly or with a 12 m-thick silver sublayer (Ag12/Au3, Ag12/Pd 2, m). The specimens plated were tested by exposure for 14–20 years at coastal corrosion stations in cold (Murmansk), moderately humid (Vladivostok), and humid subtropical (Batumi) climates. The dezincification products of the brass substrate emerging through the pores of the coating form stains and salt films on its surface. Clogging the pores, the products become responsible for the blistering of the plate. The corrosion weight loss linearly correlate with the surface accumulation of chlorides; the thicker the coating, the smaller the damaged area of the substrate, but the deeper the corrosion centers. The technical service life of protective coatings is refined.     

Effect of microalloying elements on the structure and properties of low-carbon and ultralow-carbon cold-rolled steels

Cold-rolled steels used for the forged components of automobiles should exhibit high, partly mutually-exclusive properties: high forgeability with desirably high strength, resistance to aging combined with hardenability at temperatures for drying paint coatings, etc. Satisfaction of these requirements is provided to a considerable degree by microalloying. The final mechanical properties of cold-rolled steel depend on such structural parameters of hot-rolled strip as texture, the amount of dissolved C and N atoms in -solid solution, and ferrite grain size. With constant hot rolling production schedules these structural parameters are governed by steel composition, in particular by the type of microalloying. In this work the effect is considered for dispersed microalloying elements, i.e., phosphorus, boron, titanium, and nïobium, on the final mechanical properties of low- and ultralow-carbon steels.I. P. Bardin Central Scientific Research Institute of Ferrous Metallurgy. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 21–28, March, 1994.     

水性超疏水复合涂料的制备及其机械稳定性

目的为了实现超疏水表面在实际生产生活中大规模应用,研制了一种具有大面积、低成本、可设计性和无有机溶剂等优点的水性超疏水涂料。方法以纳米级的气相二氧化硅和水性氟碳树脂为主要原料,以水为溶剂,通过氟硅烷疏水改性后获得了一种具有自清洁效应的超疏水涂料,借助场发射扫描电子显微镜、接触角测量仪、延时拍摄等手段对其进行了表征。结果该水性涂料可喷涂于各种软硬表面获得超疏水表面,其接触角均大于150°,滚动角均小于10°。水滴撞击实验表明,树脂增强的超疏水涂料经总体积为600 m L的连续水滴撞击后,其静态接触角依然大于150°,滚动角依然保持在10°以内。经砂纸打磨40周期后,水滴依然可以从其表面滚落。结论研制了一种以水为主要溶剂且价格低廉的水性超疏水涂料,将其喷涂于各种软、硬基底上均可获得均匀的超疏水涂层。该涂层还可以通过添加水性树脂来有效地增强其机械稳定性。     

The characterization of the thin oxide film formed over Fe3C at 300°C

The oxide formed over polished iron-carbon alloys at 300°C and in a 100 Torr dry oxygen atmosphere was primarily due to the oxidation of the ferrite phase, but a thin protective oxide film ( 150 Å) was formed on the carbide phase. The protective nature was attributed to the existence of a kinetic barrier of CO and CO₂ at the carbide-oxide interface. The initial oxide film formed on the carbide phase comprised many small, randomly oriented crystallites; approximately 70 Å in size, of -Fe₂O₃. This film then underwent a grain growth process via a strain-induced grain boundary migration accompanied by a phase transformation from -Fe₂O₃ to -Fe₂O₃. This transformation produced a tensile stress in the oxide film which was later relieved by the generation of cracks along the newly grown grain boundaries. These cracks exposed fresh carbide surface, released the gas barrier at the carbide-oxide interface, and provided rapid diffusional paths for further oxidation. As a result, the oxide film (-Fe₂O₃) was reduced to Fe₃O₄ and raised ridges appeared at the crack sites. Once the cracks were healed, the film again became protective.This research was supported by grant number DA-18-035-98(A) from the Chemical Research Laboratory, Edgewood Arsenal, Department of the Army. This paper is based on work performed as part of a thesis submitted by H. J. Kim to Lehigh University in partial fulfillment of the requirements for the Ph.D. degree in Metallurgy and Materials Science.     

Oxidation properties of Fe-5Cr-4Al (wt.%) alloys in oxygen at temperatures 1000°C–1320°C

Oxidation kinetics of a parent Fe-5Cr-4Al alloy subjected to two types of anneals were investigated at temperatures ranging from 1000°C to 1320°C. The alloy annealed at 850°C exhibited a rapid transient oxidation stage associated with growth of nodules containing iron oxides and internal precipitation of -Al₂O₃ in the alloy beneath these nodules. The nodules nucleated and grew from sites located in the regions of the alloy grain boundaries during the period of rapid alloy grain growth. Nodular growth virtually ceased when a continuous -Al₂O₃ film formed at the nodule-alloy interface. The alloy subjected to anneal at 1000°C and at the reaction temperature to stabilize the alloy grain size tended upon oxidation to form a protective -Al₂O₃, layer by parabolic kinetics at temperatures to 1250°C. If this alloy was oxidized in stages at 1000°C, a protective -Al₂O₃ scale was formed up to 1320°C. The temperature coefficient of the parabolic oxidation kinetics was consistent with diffusion processes at boundaries of the -Al₂O₃ grains playing an essential role during growth of this protective oxide layer.     

Corrosion Resistance of Molybdenum in Mercury

Corrosion resistance of an -50 alloy in mercury is studied at 473 and 573 K under conditions of thermal cycling. The high corrosion resistance of the alloy, caused by very low solubility of its components in mercury, is demonstrated.     

Effect of Deformation and Heat Treatment on the Structure and Properties of Quenched and Aged Alloy 36NTYu

Variation of the structure and mechanical properties of alloy 36NTYu after various kinds of treatment (quenching with aging at 750°C, deformation with degree = 50 – 98%, annealing at 750°C) studied by mechanical tensile and fatigue tests is described. The changes in the dislocation structure and lamellar segregations of -phase in the treatment process are determined. It is shown that the fatigue limit and the friction stress are well correlated.     

Variability of Stress in Alumina Corrosion Layers Formed in Thermal-Barrier Coatings

Residual stress distributions have been measured and mapped usingphotoluminescence, piezo spectroscopy in thermally grown alumina oxides(TGO) formed on platinum-aluminide bond coats with thermal-barrier coatings(TBC) of thickness 0, 3, and 200 m. When there is a 3-m TBC or noTBC, the residual stress varies substantially with position and the meanstress is much lower than expected from simple thermoelastic, plane-stressanalysis. This is partly explained by the stress being relaxed by surfaceroughness, but stress mapping indicates that local fracture hasoccurred. The stress in the TGO formed under 200 m TBCs appear muchmore uniform and the mean value is approximately equal to the estimatedthermoelastic plane stress. This could be due to the extra constraintimposed by the TBC. The luminescence line width is much greater forspecimens with 200-m TBC and is too large to be explained by varyingmacroscopic stresses due to interface roughness. The effects of oxidationtime and reactive-element additions to the substrate at the level of30 ppm, on the residual stress, are relatively minor over the rangesexplored in these experiments.     

Mechanical properties and structure of deposited wear-resistant metal

Wear-resistant hard-alloy coatings (facings) of high-carbon iron-based alloys, with a composition close to that of tool steels, are used to increase the abrasive-wear resistance of working friction surfaces of products. Our aim here is to study the mechanical properties of the deposited metal after different technological conditions of coating deposition.St. Petersburg Institute of Mechanical Engineering (College of Engineering, Leningrad Metal Works). Scientific-Industrial Firm Burevestnik, St. Petersburg. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 20–23, August, 1994.     

Features of formation of the structure in production of blanks of disks of heat-resistant nickel alloys

Conclusions To provide a high level of mechanical properties in wrought blanks of cast ÉP741NP and ÉP962 alloys it is necessary to form controlled structures. A necklace-type structure formed in homogenizing isostatic treatment, subsequent thermomechanical working including alternation of the operations of deformation in the (+)-area and recrystallization anneals, and final heat treatment is preferable. The temperature conditions of all stages of thermomechanical working are strictly controlled, especially the final operation of deformation and heating for hardening. To eliminate hardening cracks and distortions it is necessary to use molten salts at t=600°C as quenchants. The use of multiple production operations makes it possible to significantly reduce the structural inhomogeneity related to inhertance of the original dendritic structure. However, the structure of the final semifinished product is nevertheless characterized by a difference in occurrence of the processes of polygonization and recrystallization between the former dendritic cells and the interdendritic spaces in deformation and heat treatment.To obtain structurally homogeneous blanks for gas turbine engine parts it is necessary to use basically new methods of remelting such as vacuum double electrode remelting and electron beam remelting with an intermediate vessel.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 25–29, December, 1991.     

Oxidation-sulfidation behavior of Ni aluminide in oxygen-sulfur mixed-gas atmospheres

Oxidation-sulfidation studies were conducted on sheet samples of nickel aluminide, containing 23.5 at. % Al, 0.5 at. % Hf, and 0.2 at. % B in an annealed condition and after preoxidation treatments. Continuous weight-change measurements were made by a thermogravimetric technique in exposure atmospheres of air, a low- gas mixture, and low- gas mixtures with several levels of sulfur. Detailed scanning electron microscopy (SEM), X-ray, and electron microprobe analyses of the corrosion product scale layers were performed. The air-exposed specimens developed predominantly nickel oxide; the specimen exposed to a low- .     

Effect of regimes of ion nitriding on the structure and properties of titanium alloys

Titanium alloys occupy an important place among modern high-strength materials used in the aircraft industry because of their high specific strenth and corrosion resistance and good adaptability to manufacture. However, their use is restricted due to low abrasion resistance and a tendency toward sticking and setting in the operation in friction members. The wear resistance of titanium alloys can be increased by ion nitriding. This work concerns the effect of regimes of ion nitriding on the structure and wear resistance of and ( + ) titanium alloys.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 26 – 28, May, 1996.     

The hot-corrosion behavior of novel CO-deposited chromium-modified aluminide coatings

This paper reports the successful co-deposition of inclusion-free chromiummodified aluminide coatings using a pack-cementation process. The substrate used was the nickel-base superalloy, René 80H. The coatings were of the outward-diffusion type; however, unlike the usual outward-diffusion coatings, the present coatings were relatively free of pack inclusions. The coatings consisted of -Cr precipitates in a matrix of -NiAl. The morphology and distribution of the -Cr precipitates could be adjusted to the extent that two types of coating structures could be obtained. The Type I coating structure contained lamellar -Cr precipitates situated in the surface region of the coating, whereas the Type II coating structure contained small, spheroidal -Cr precipitates distributed throughout the outer of a two-layered coating. Both coating types exhibited significantly improved hot-corrosion resistance in a 0.1% SO₂-O₂ environment at 900°C compared to a commercial aluminide coalting. A study of the corrosion behavior of Type I coatings containing pack inclusions showed that the inclusions were deleterious to the corrosion resistance of the coatings. The corrosion behavior of chromium-aluminide coatings was dependent on both the distribution and amount of -Cr precipitates in the coating.