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.     

Metastable manganese austenite as a structural base of high-stability steels conditions of dynamic contact loading

Important regular features of the structure and special features of the behavior of metastable manganese austenite under conditions of quasistatic deformation and dynamic contact loading are considered. Based on the correlation of the energy of packing defects of manganese austenite with the kinetics of deformation martensitic transformations { , } and the capacity for deformation strengthening and relaxation of stresses, principles for choosing the base composition of metastable austenitic steels with a high operating stability for different conditions of dynamic contact loading are established.     

Isothermal formation of the ε-phase after phase hardening in ferromanganese alloys

Conclusions The investigations carried out show that isothermal formation of the -phase can be controlled not only by alloying, but also by means of repeated phase transitions. Reduction of the temperature at which the formation of the -phase commences intensifies the isothermal transformation near the martensite point and at room temperature. The latter is valid if the -transformation during continuous cooling begins not lower than the temperature at which the isothermal soaking is carried out, otherwise the intensity of the isothermal process decreases, and the lower the commencement of the -transformation with respect to the temperature isothermal line, the more the intensity drops. It was found that if the -phase forms at –60, –70°C, there is a complex dependence between the rate of the isothermal process and the temperature.It was demonstrated that when the -transformation temperature is fairly low, austenite can be supercooled by rapid cooling and the -phase may form during heating. Given the same supercooling rate, the transformation of austenite into -phase during heating is more complete when the heating rate is slow.It was noticed that if in continuous cooling the -phase forms at –60, –70°C, preliminary supercooling broadens the temperature range over which the isothermal -transformation is observed. The intensity of the process is influenced by the heating rate after supercooling.It was found that the maximum amount of -phase forming in the alloy G19 during continuous cooling after repeated phase transitions and subsequent isothermal soaking does not exceed 50–55%.It was discovered that isothermal soaking at room temperature in between repeated phase transitions intensifies the stabilization of the austenite.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 2–8, April, 1965     

Plating Kinetics and Quality of Copper-Organic Coatings

During the cathodic deposition of copper from sulfate electrolytes containing -caprolactam, the process inhibition is shown to be caused by adsorption of electroactive complexes formed in the surface layer via an interaction between the metal ions and adsorbed additive molecules. A correlation between the metal nature and the catalytic or inhibiting effect of -caprolactam, which can polymerize at the electrode due to electric current, is revealed. It is found that composition and properties of copper-organic coatings can be controlled by varying the -caprolactam concentration.     

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.     

On the oxidation ofα-Fe andε-Fe2 N1−z II. Residual strains and blisters in the oxide layer

The development of residual strains in the iron-oxide layers growing on -Fe and -Fe₂N_1–z at 673 K in O₂ at 1 atm was investigated by X-ray diffraction at room temperature. After correction for thermal-strain development due to cooling after oxidation, it was found that tensile growth strains occur in magnetite and compressive growth strains occur in hematite. The growth strains in the oxides on -Fe are (in absolute sense) 2–3 times as large as those in the oxides on -Fe₂N_1–z. Buckling of the oxide layer occurs in the case of an -Fe substrate, which is attributed mainly to relaxation of the growth strains in magnetite and hematite. Thermal-strain development during cooling enhances the tendency for buckling. Buckling is not observed for oxide layers on -Fe₂N_1–z, which could be due to the smaller values of absolute strain in the oxide layer on -nitride. The absolute values of the growth strains in the oxide layer on -nitride being smaller is attributed to microstructural changes in the nitride layer during oxidation.     

The Effect of the ε-Caprolactam Concentration on the Electrodeposition of Nickel–Polymer Coatings

It is shown that an increase in -caprolactam concentration in sulfate nickel-plating baths enhances its adsorption on Ni cathode, which is followed by the formation of its complexes with nickel ions in the solution. The first process decelerates the electrode reaction, and the second one facilitates it. In the interval of the maximum deceleration of the process, nickel–polymer coatings with the greatest content of -caprolactam and the highest surface conductivity, substantially exceeding that of pure metal, are formed.     

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.     

The Corrosion of Alloy Steels under Antirust Compounds in the Presence of Microbes

The kinetic corrosion characteristics of 352-, 302, and 30 steels with rust-preventive compounds applied are investigated in an industrial neutral electrolyte, depending on whether a compound is infected with microorganisms or not. The effect of microorganisms and their metabolites on the corrosion of steels greased with the compounds are assessed.     

Effect ofθ-alumina formation on the growth kinetics of alumina-forming superalloys

Alumina-forming ODS superalloys are excellent oxidation-resistant materials. Their resistance relies upon the establishment of a stable, slow-growing, and adherent -alumina. In the present investigation, these alloys exhibited unstable and relatively less adherent -alumina phase, which increased the oxidation rate in the transient stage and converted into -alumina in the later part of the exposure. The oxide-growth process was found to depend upon various parameters such as temperature, time, and presence of an active elecment in the superalloy. Characterization carried out by XRD, SEM/EDAX, and AES on oxidized ODS and non-ODS alloys demonstrated a significant influence of the active element, Y, on the transformation of - to -alumina. SIMS analysis of two-stage oxidation at 900°C for two different durations evidently showed that the change in the transport process is due to -to--alumina transformation. On the basis of these results, a new and consistent mechanism is proposed to explain the influence of -alumina and its transformation on growth kinetics and the effect of yttrium on the transformation leading to good scale adherence and oxidation resistance.     

Control of the structure of two-phase titanium alloys in thermomechanical working

Conclusions The embryos of - and -phases obtained in +-titanium alloys in hardening and aging are preserved in cold working and become centers of growth of these phases in subsequent aging. As a result it is possible to obtain -phase or more uniformly distributed -phase in cold-worked and aged alloys.Moscow Institute of Electronic Machine Building. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 53–55, May, 1984.     

Analysis of fatigue curves for alloy 36NKhTYu in the quenched and annealed conditions

Conclusion The limiting cycle amplitude in alloys is determined by friction stress which hinders dislocation movement, and in the region of stresses satisfying the condition _m + _{m f} it does not depend on the magnitude of the static component of the stress cycle.Novosibirsk Pedagogical Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 21–23, March, 1991     

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.     

Two-phase ferritic-martensitic steels

Conclusions The results of laboratory and production experiments showed that the main condition for providing the necessary combination of properties of two-phase ferritic-martensitic steels (high tensile strength, low yield strength, high plasticity and work hardenability) is obtaining the specified quantity of the hardening phase (martensite) in the structure (20–28% M to obtain _t 550 MPa or 10–18% M for _t 450 MPa). The specified ratio of the structural constituents under conditions of mass production of two-phase ferritic-martensitic steels may be guaranteed only with the use of steels containing carbon and alloy elements within the necessary limits and also with strict observance of the heat-treatment cycle. Without the use of metallographic measurements as the criteria for obtaining the optimum structural condition in addition to the required values of strength and plasticity it is necessary to use the _0.2/_t ratio, which must not be greater than 0.5–0.6 with the absence of yield points on the tensile curve (without special temper rolling).As the result of the combination of work done in the Central Scientific-Research Institute of Ferrous Metallurgy together with plants of the Ministries of Ferrous Metallurgy and of the Automobile Industry at present the production is being introduced and experimental production lots of heat-treated two-phase steels of the following types with guaranteed mechanical properties are being supplied:At the Novolipetsk Metallurgical Combine cold-rolled 0.7–2.0-mm sheet of 06KhG(S)Yu and 06G2SYu steels with _0.2 = 260–320 MPa, _t 550 MPa, ₄ 30%, and _0.2/_t 0.5–0.6.At the Cherepovets Metallurgical Combine hot-rolled 2–6-mm sheet of 09G2(S) steel with _0.2 = 260–320 MPa, _t 550 MPa, ₄ 25%, and _0.2/_t 0.5–0.6.At the Beloretsk Metallurgical Combine (billets melted and rolled at the Cherepovets Metallurgical Combine) heat-treated cold-drawn wire up to 10.5 mm in diameter of 06KhGR steel with _0.2 250 MPa, _t 530 MPa, and ₁₀ 30%.For successful development of the production and use of two-phase ferritic-martensitic steels the combined work of the designers of machine building plants on determination of the most effective types of parts, of engineers on correction of the method taking into consideration the specifics of the properties of two-phase ferritic-martensitic steels, and of users on determining the service properties of parts of these steels is necessary. The fulfillment of such a combination of work will make possible th timely formulation of the further work of the metallurgical industry and determination of the required volume and product range of rolled products of two-phase ferritic-martensitic steels.I. P. Bardin Central Scientific-Research Institute of Ferrous Metallurgy. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 11, pp. 25–29, November, 1984.     

On the Removal of Aluminide Coating from Blades of Gas Turbin Engine

The peculiarities of removing -11 coating from 32 type alloy in an acidic etching bath depending on the concentration and ratio between the amounts of potassium bichromate and ammonium heptamolybdate additives are studied with gravimetrical and electrochemical methods. The results are explained by the peculiarities of bichromate and molybdate ions adsorption at the surface and their oxidizing properties. Baths providing sufficiently quick removal of the coating at a minimum alloy surface etching are recommended.     

Calculations of parabolic reaction rate constants

The oxidation kinetics of only a very limited number of pure metals or binary alloys can be described by the simplest parabolic law, m²=k_pt, Thus for a transient period of faster kinetics, the steady state parabolic law is given by (m–m_i)² = k_p(t–t_i) when the initial weight gain m_i does not contribute to steady state rate control. In such a case, a plot of the kinetics data as m vs t^1/2 is inherently superior to the m² vs t plot for an accurate determination of the steady state parabolic rate constant, as well as for the analysis of the transient, faster kinetics.     

High-temperature thermoplastic strengthening of steels St3sp and 09G2S

Conclusions We worked out a regime of high-temperature thermoplastic treatment of steels St3sp and 09G2S consisting in austenization at 1020°C, strain (=200%, =5.7%) at 940°C with subsequent cooling at a rate >100°C/sec.As a result of such treatment the tensile strength of steel St3sp is increased to 1230 N/mm², of steel 09G2S to 960 N/mm², and the conventional yield strength to 1100 and 840 N/mm², respectively.N. É. Bauman Moscow State Technical University. All-Union Research Institute of Metallurgical Machinery Construction. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 18–19, July, 1991.     

Oxidation Behavior of Two-Phase γ + σ Nb-Ti-Al Alloys

The oxidation behavior of a series of single-and two-phase Nb-Ti-Al alloys, selected from the sameextended + tie-line, was investigated at1200°C in air. The single-phase alloy suffered from extensive internal oxidation andoxidized at a much higher rate than the single-phase alloy. In a two-phase + microstructure, the phase was preferentiallyattacked to form internal alumina andTi-rich nitride. This preferential attack of limited the extent to which the phase wasinternally oxidized, but also interrupted the formationof a continuous alumina scale. The single-phase alloyalso did not form a continuous alumina scale. Theinability of the phase to form continuousalumina was attributed to a combination of nitrideformation and internal oxidation. The oxidation behaviorof the two-phase + Nb-Ti-Al alloys isdiscussed in terms of mechanisms developed for theoxidation of binary, two-phase alloys.     

Role of Adsorbed Metal Complexes in Cadmium Electrodeposition from Iodide-Containing Aqueous Ethanol

Structurization phenomena in a mixed solvent were found to determine, by affecting the solvation degree of an anion, its adsorptivity at the electrode and, consequently, the surface concentration of the nonaqueous solvent. The formation of activated Cd²⁺ complexes with iodide anions in an adsorbed layer is usually accompanied by accelerating the electrode reaction. The desalting effect of the mixed solvent in the zones of its structural stabilization is mainly manifested as the enhanced adsorptivity of iodide anions and the correspondingly facilitated discharge of metal ions. The highest discharge rate was found at ₂ 0.9 when the structure of EtOH is ordered with monomeric water molecules. The highest surface concentration of EtOH and the lowest rate of cadmium electroreduction correspond to a structurally disordered mixture ( ₂ 0.4).