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.     

Austenitic stainless steels strengthened by phase strain hardening and aging

Conclusions Nonmagnetic stainless steels of the Kh12N12T3 and Kh12N14T3 type have good mechanical properties after phase strain hardening and aging (_0.2 = 685 - 785 MPa, _b = 1275 MPa, 20%) as compared with the properties of Fe-Ni-Ti austenitic steels with 26–30% Ni. After phase strain hardening and aging the stability of these steels is high with respect to the transformation during cold treatment.IFM UNTs AN SSSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 57–60, June, 1981.     

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.     

Phase and structural transformations in deformation and heat treatment of 08Kh15N5D2T steel tubing

Conclusion Annealing in the intercritical area of the -transformation or hardening from a continuous furnace with subsequent tempering in the -transformation range included in the production plan for cold-rolled 08Kh15N5D2T tubing do not restore the original workability of the steel since the residual austenite is stabilized toward the -transformation in deformation. Annealing at 650°C does not lead to complete recrystallization and detexturing of the metal. To obtain this it is recommended that rapid electric heating for hardening with subsequent tempering be introduced into the production plan for rolling of tubing.Ural Polytechnic Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 7–11, August, 1990.     

Effect of preliminary heat treatment on phase transformations and properties of steel Kh15N5D2T (VNS-2)

Conclusions Preliminary heat treatment has a substantial effect on the kinetics of the transformation, the amount of retained austenite, the grain size, and the work of crack propagation in steel Kh15N2D2T after final heat treatment.N. I. Lobachevskii Gorki Physicotechnic Institute of Gorki State University. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 63–64, May. 1978.     

Use of Low-Active Circulating-Gas Aluminizing for Repairing the Nozzle-Set Containers of a Turbine

The cause of damage in internal and external containers of the nozzle set of the first stage of the TV3-117 engine is shown to be the intercrystallite gas corrosion of the materials of which they are produced (alloy KhN38VT and steel 12Kh18N10T, respectively). It is shown that low-active circulating-gas aluminizing can be used for repairing the parts, increasing their high-temperature strength, and curing micro- and macrocracks.     

Effect of nitrogen and chromium on the mechanical properties of austenitic steels at −196°C

Conclusion Nitrogen lowers and chromium raises (with >3% N) the strength (_b0.2), ductility (, ), and fracture toughness of austenitic stainless steel of the Kh(18-24)N20 type in the aged condition. The effect of chromium on the properties is due to a change in the solubility of nitrides.I. P. Bardin Central Scientific-Research Institute of Ferrous Metallurgy. Translated from Metallovedenie Termicheskaya Obrabotka Metallov, No. 8, pp. 6–8, August, 1979.     

Structural changes during aging of maraging steel 03Kh11N10M2T

Conclusions Electron microscopic and Mossbauer spectroscopic studies showed that aging of steel 03Kh11N10M2T produces complex structural changes due to redistribution in martensite of titanium, molybdenum, nickel, and chromium atoms, and precipitation of Ni₃Ti even with brief holding (5 sec at 525°). Also, a partial transformation occurs in previously deformed samples during aging at 525°. There are good correlations between the structural changes and the changes observed in the properties of steel 03Kh11N10M2T during aging.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 28–32, October, 1974.     

Brass Depassivation in Neutral Chloride Media

The influence of the composition of Cu–Zn alloys and of the content of chloride ions in solution on the initial stages of brass depassivation in a borate buffer was studied. It was demonstrated that the pitting resistance of brasses decreases from to ( + ) brass. The pit initiation was attributed to nucleophilic substitution of corrosive anions for the passivating species in the adsorbed complex. It was shown that pit initiation on brasses, as for copper, predominantly follows the dissociative mechanism.     

Effect of Continuous and Isothermal Hardening on the Wear Resistance of Tools Produced from High-Speed Steels

The effect of isothermal hardening on the red-hardness (heat resistance) of steel R18 is studied. A complex dependence of the red hardness on the temperature of isothermal hardening and the hold time is shown. Tools from steel R18 are shown to have maximum heat resistance and wear resistance after bainitic hardening in the pre-transformation range.     

Protection of Sintered Steels against Corrosion in Neutral Media with an N-M-1 Inhibitor

The effect of an N-M-1 inhibitor (a salt of cyclohexylamine and C₁₀ to C₁₆ aliphatic acids) on the corrosion of sintered powder steels 13 and 141 (with the 14 to 17% porosity) in distilled or tap water at 20 to 80°C, as well as in 0.05 M Na₂SO₄ solution, is studied by gravimetric and electrochemical methods. The protective concentration of the inhibitor is lower in distilled, than in tap water or sodium sulfate solution. The protective action decreased with an increase in temperature. In tap water or sodium sulfate solution, the corrosion-inhibiting effect is weaker for 13 than for 141.     

Structure and Mechanical Properties of Maraging and Low-Carbon Martensitic Steels

The structure, mechanical properties, and crack resistance after tempering of maraging steel 03Kh11N10M2T (EP-678) and low-carbon martensitic steel 12Kh2G2NMFT are studied. The range of tempering temperatures ensuring the combination of properties required for massive parts (_r #x2265; 1300 MPa, _0.2 1100 MPa, KCT 0.2 MJ/m²) is determined. It is shown that steel 12Kh2G2NMFT is better adaptable to manufacture because it is hardened by air-cooling.__________Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 32 – 35, January, 2005.     

Effect of rapid cyclic electrothermal treatment on the structure of nickel steel

Conclusions The high dislocation density of austenite undergoing the transformation is due to the influence of fresh dislocations that occur during the transformation in virtue of its martensitic character and to dislocations inherited from the original phases.Since the increase of the dislocation density in austenite causes an increase in the number of martensite crystals, it can be assumed that the increase in the number of phase nuclei is due to an increase in the density of fresh dislocations. In this case the refining of martensite is due to an increase in the number of nuclei and to the barrier effect of elements of the substructure. The formation of atmospheres of impurity atoms at dislocations in alloys with carbon stabilizes the austenite and intensifies recrystallization processes. Cementite particles in phase are not inherited by austenite with heating to the transformation temperature.Institute of Metal Physics, Academy of Sciences Ukrainian SSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 20–23, January, 1975.     

Structure of carburized Fe-Ti and Fe-Ti-Cr alloys

One method for the production of material of a new class is the use of the ferrite austenite + carbide transformation. The transformation occurs under specific temperature-concentration parameters of carburization of low-carbon ferritic iron-carbide-forming element alloys. Ferrite decomposes with formation of austenite-carbide colonies similar to eutectoid ones. The colonies are preferentially oriented in the direction of carbon flow, i.e., normal to the carburized surface. Fe-Ti and Fe-Ti-AE alloys, where AE is the alloying element, are of special interest in this connection. Titanium carbide is extremely hard and, when used as an agent reinforcing the surface layer, increases the hardness and wear resistance of the alloy. In addition, TiC dissolves impurities poorly, and therefore in the alloying of Fe-Ti alloys by elements improving their thermal stability or corrosion resistance, its formation will not deplete the matrix. However, the addition of a third component to the Fe-Ti alloy may cause degeneration of the structures of the colonies. The present work is devoted to the effect of different concentrations of chromium on the structure of carburized Fe-Ti alloys.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 4–7, May, 1995.     

Effect of the tempering temperature and time on the structure and phase composition of the AMg6 alloy

Conclusions It was determined that the decomposition of the solid solution in the AMg6 alloy begins at the grain boundaries. After a certain time interval the plate-like -phase precipitates within the grains. After a longer tempering time the platelets coagulate and take on a rounded form.At temperatures of 200 and 250°C the metastable -phase is not completely converted into the -phase, and even after a very long tempering time there is still a considerable amount of the -phase in the structure.At a temperature of 150°C or lower, only the metastable -phase occurs in the alloy even after tempering as long as 9 months.Translated from Metallovedenie i Termichesakaya Obrabotka Metallov, No. 9, pp. 59–61, September, 1966.     

Nitrogen-containing superlow-carbon austenitic steel 02Kh25N22AM2

At present the equipment for manufacturing carbamide mineral fertilizers is produced from domestic steel 03Kh17N14M3 having carbamide quality. Imported equipment also used in the industry is produced from steel of the 25–22–2 (Cr -Ni-Mo) type shipped by various firms, namely, 2RE69 (Sandvik, Sweden), 254SFER (Avesta, Sweden), 2522LCN (VDM, Germany), DM 1.4466 (Germany), and X2CrNiMo 25–22–2 (Dalmine, Italy). The imported steels are used because in some units steel 03Khl7Nl4M3 does not provide the requisite corrosion resistance in an intensified process of carbamide manufacturing. We currently possess domestic high-alloyed steel for producing new and repairing imported equipment operating under the severe conditions of carbamide synthesis. The present paper concerns the structure, mechanical properties, and corrosion resistance of industrially produced steel 02Kh25N22AM2 (ChS-108) and the recommended range of its application.Inventor's Certificate No. 1686028, Stainless steel,Byull. Oikryl. Izobrei., No. 39 (1991).Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 27 – 31, February, 1996.     

Developing Concepts of Chromium Functions in the Passivation and Pitting of Fe–Cr Alloys

The passivability and pitting resistance of Fe–(0–100)Cr alloys in deaerated acidic sulfate environments (at a concentration of sulfate ions of 0.1 to 1.0 mol/l and pH from 0.5 to 1.8) and neutral borate buffer solutions with a chloride concentration of 0.003 mol/l and pH 7.3 are studied with the use of steady-state and pulse electrochemical methods. Four critical alloy compositions corresponding to the sharp changes in the passivability, repassivability, and pitting resistance of the alloys are discussed: 6.5; 11; 17; and 27% Cr. Based on considering the alloys as purely mechanical mixtures with no sign of any order so that a chromium atom can occupy any lattice point with a probability proportional to the bulk chromium content, the following hypothesis is put forward. It is the crystallographic and electronic structure of Fe–Cr alloys that forms the main reason for the existence of the mentioned critical concentrations. Upon reaching certain critical compositions, chromium atoms either occupy positions in each coordination sphere (6.5% Cr), each elementary cell of an scc lattice (11% Cr), or each quasirhombohedral pore (17% Cr); or a superlattice compound appears (27% Cr).     

Electrochemical Behavior of Nickel Hydride in Sodium Hydroxide Solutions

Electrochemical behavior of nickel hydride Ni₂H (-phase) is studied in 0.01–1 N NaOH by using common (VA) and cyclic (CVA) voltammetry, chronocoulometry, amperometry, and potentiometry. The limiting anodic and cathodic currents in VA and CVA curves are caused by the hydride decomposition via the following scheme Ni₂H -phase Ni + H_abs, where the intermediate -phase contains 0.003 at. % H, that is, one tenth that in the saturated -phase (0.03 at. %). At open circuit, the hydride maintains the equilibrium hydrogen potential. In the first 30 min, the hydrogen ionization from hydride is limited by solid-state diffusion and, later, the hydride decomposition. The anodic process involves ionization of sorbed hydrogen, while the cathodic process represents its electrochemical desorption: H₂O + H_ads + e H₂ + OH^–. The hysteresis observed in the cathodic CVA and open-circuit chronograms of the hydride potential in the beginning of anodic dissolution reflect the changes in the surface coverage of hydride with adsorbed hydrogen. The rate constant of hydride decomposition k, the rate Vitself, and the equilibrium constant K are as follows: k = k = 8 × 10^–5 s^–3, V = 3 × 10^–5 C/cm², and K = 10. The kinetic parameters of hydrogen electrochemical ionization from the hydride are b _a = 0.12 V and = 0.5.     

Wear resistance of complexly alloyed iron-carbon alloys

Conclusions High-carbon chromium alloys alloyed with Ti, Mo, Al, and Cu in the hardened state have much greater wear resistance than the high-chromium alloys used at present in industry as wear-resistant materials for operation in an abrasive medium. The difference between these alloys is particularly great in abrasion against silicon cloth. For instance, the wear resistance _s of the alloy U33Kh11T3M2YuD is 4.5 times greater than of steel R18 and of vanadium pig iron. This is obviously due to that fact that the investigated alloys contained titanium carbides, chromium carbides type M₇C₃, intermetallic phases with Mo, Ti, and Cr, and it is also due to the higher alloying of the - and -phases and the larger carbon content in the -phase.Among the investigated high-carbon chromium-titanium-molybdenum alloys, the most wear resistant were the alloys U33Kh11T3M2YuD and U29Kh14T5M2YuD containing more than 3% Ti; more than 2% Mo, and 2.9–3.2% C, 11–14% Cr, 0.7–1.0% Al, and 0.25–1.0% Cu. Unlike other chromium-titanium-molybdenum alloys, the last-named alloys are characterized by the presence of the carbides TiC and Cr₇C₃ which, according of the data of [6, 7], may be regarded as the most wear resistant. According to the data of [6], the introduction of more than 2% molybdenum into alloys with high content of carbon and chromium (up to 12 and 18%, respectively) ensures reduced brittleness of the carbides, and this is bound to have a favorable effect on the wear resistance of the alloys.Bryansk Institute of Transport Machine Construction. I. P. Bardin Central Research Institute of Ferrous Metallurgy. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 48–50, January, 1985.     

Age hardening of VT35 titanium alloy

VT35 alloy belongs to -titanium alloys that preserve the body-centered lattice of the -phase in hardening from the -region. In an equilibrium state this alloy has an + structure. After hardening, VT35 alloy has a high ductility and a low strength. The subsequent single- or double-stage aging in the biphase region promotes considerable strengthening of the alloy due to segregation of a second phase. VT35 titanium alloy is hardened to a pure -phase by cooling from the single-phase region in water, in air, or with the furnace (at a rate of at least 3 -4 deg/min). This special feature of the alloy is caused by its chemical composition (Ti - 3% Al -15% V - 3% Cr - 3% Sn), which provides a high coefficient of -stabilizationK = 1.5. The present paper concerns the processes of age toughening of a hardened VT35 alloy and the kinetics of the structural transformations in such a treatment.