General and pitting corrosion of chromium-manganese steels in halogen solutions

We develop methodical foundations for evaluation of the reliability and longevity of 60Kh3G8N8V, 12Kh18AG18Sh, and 05Kh18AG19Sh new chromium-manganese steels, which are used in the power industry, and give recommendations concerning the improvement of their reliability. We study the regularities of the influence of operating fracturing factors on the corrosion-mechanical resistance of these steels. Contact with chloride solutions at elevated temperatures significantly lowers the corrosion resistance of chromium-manganese steels due to worsening of the protective properties of a passive film. In addition, anodic polarization upon contact with copper and the products of its corrosion results in pitting corrosion of steels and their corrosion cracking. We substantiate the necessity and show the prospects of electrochemical protection of steels against corrosion cracking in chloride solutions and in solutions with copper (II) cations. Translated from Fizyko-Khimichna Mekhanika Materialiv. Vol. 36, No. 3, pp. 7–15, May-June, 2000.     

Cryogenic-alloy strength and cracking resistance under dynamic loading

Test results are given on 12Kh18N10T and 03Kh20N16AG6 steels and on AMg6 alloy designed to give the dynamic strength and cracking resistance at strain rates of 0.36 m/sec in the temperature range 77–293 K. Cooling raises the strength, plasticity, cracking resistance, and resistance to crack growth in AMg6 alloy. Cooling the two steels increases the strength and cracking resistance, but reduces the plasticity and crack propagation resistance. Compact specimens with small natural thicknesses can be used to determine the correct critical values for the cracking resistance J_Ic for 03Kh20N16AG6 steel and AMg6 alloy. It is possible to determine correctly the critical values for the cracking resistance for 12Kh18N10T steel at 77 K.Translated from Problemy Prochnosti, No. 9, pp. 48–53, September, 1992.     

Effect of cooling to 4.2 K on the strength and cracking resistance of the parent metal in welded joints in 07Kh13N4AG20 steel

The results are presented of experimental examination of short-term strength and cracking resistance of the parent metal and welded joints in 07Kh13N4AG20 steel in the temperature range 293–4.2 K. The mechanical characteristics of the welded joint in the examined steel are compared with the characteristics of 12Kh18N10T and 03Kh20N16AG6 steels. The results show that the mechanical properties and crack propagation resistance of the weld metal in 07Kh13N4AG20 steel are similar to those of the parent metal.Translated from Problemy Prochnosti, No. 9, pp. 45–48, September, 1990.     

Mechanical properties of chromium-manganese austenite steels in a hydrogen environment

We study the influence of gaseous hydrogen on the mechanical properties of hardened and deformed specimens of 07Kh13G20AN4 and 03Kh13N9G19AM2 steels under a pressure of 35 MPa in the temperature range 293–773 K. We establish that hydrogen causes the strain martensite transformation of nitrogen-containing austenite stable in air. Formation of a polygonal dislocation substructure by means of preliminary mechanical or thermomechanical treatment significantly decreases the tendency of steels toward hydrogen degradation. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 35, No. 5, pp. 75–78, September–October, 1999.     

Mechanical properties of martensitic steels in gaseous hydrogen

We present the regularities of hydrogen degradation of 03Kh12N10MT, 15Kh12N2MFAV and 13Kh11N2V2MF steels under a pressure of 30 MPa within the temperature range of 293–673 K. The minimum values for plasticity, low-cycle fatigue, and static crack resistance, which do not decrease with an increase in pressure of hydrogen atmosphere and content of the absorbed hydrogen, are found. The difference between temperature dependences of the coefficients of influence of hydrogen on static and cyclic crack resistance of martensitic steels with various content of austenite is established. The main fractographic features of the influence of hydrogen on the micromechanism of fracture of steels under different types of loading and temperatures are determined.     

Specific features of the deformation of steels in hydrogen

We have studied the effect of hydrogen on the mechanical properties of foils made of 08Kh18N12T steel under uniaxial tension. The initial stages of deformation in hydrogen require forces smaller by a factor of 3–5. In the case of biaxial tension of membranes made of this steel, their deformation ability also increases. The effect of hydrogen on the axial residual stresses of the first kind in 08Kh18N12T, 40Kh, and ShKh15 steels manifests itself in the activation of tensile deformation (inducing of compressive stresses). We have recorded a 30% increase in the fatigue limit of an austenitic alloy in hydrogen with a pressure of 30 MPa (the reference medium is air). __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 4, pp. 84–88, July–August, 2008.     

Hydrogen Permeability of Proton-Irradiated Reactor Steels with Oxide Films

The influence of oxidation and proton irradiation on the hydrogen permeability of 12Kh18N10T, ÉP-838, and 10Kh9VFA reactor steels is investigated. The critical temperatures of thermal desorption of implanted hydrogen are determined. It is shown that, unlike hydrogen penetration, the proton irradiation of oxidized specimens increases their thermal stability.     

Fatigue crack growth in thin steel sheets

Surface fatigue crack growth is considered for thin steel sheets composed of two steels widely used in cryogenic engineering: 12Kh18N10T and 07Kh13N4AG20. Specimens with thicknesses of 4, 8, and 12 mm have been tested at 293 and 77 K (in liquid nitrogen). There is a boundary between the zones affected by the rear and front edges of the specimen in the plane of semielliptical crack growth, which affects the stress and strain patterns near the crack front. The boundary between the zones is approximated by a second-order curve. The thickness and the temperature affect the slope of the curve. The kinetic features are seen at points in the crack front at such boundaries.Translated from Problemy Prochnosti, No. 2, pp. 27–34, February, 1992.     

Hydrogen permeability of reactor steels

The hydrogen permeability of 12Kh18N10T, 316SS, and 10Kh9VFA reactor steels and EP-838 and Kh12G20V alloyed chrome-manganese steels is studied in the intact state, after thermal treatment, alloying, application of protective coatings, oxidation, irradiation with H⁺ ions, and in the presence of welded joints. We compute the permeation of hydrogen P _c corresponding to the ecologically safe level of losses of tritium through the reactor equipment into the environment and show how the changes in the structure and modification of the surface agree with this value. The permeability and solubility of hydrogen in welded joints of the investigated steels are determined.     

On the Effect of Loading System Rigidity on Strain Resistance and the Fracture of Alloy Specimens on Deep Cooling

The results of investigating the effect of loading system stiffness on the parameters of low-temperature intermittent yield and the mechanical characteristics of the steels 03Kh20N16AG6 and 12Kh18N10T and the titanium alloy 3M at 4.2 K at different development stages of plastic strain instability are presented. Criteria of fracture by the adiabatic-shear mechanism are considered. An analysis of the stiffness components of an electrohydraulically driven testing machine is given. The necessity of laying down stiffness regulations for conventional mechanical tests of materials has been shown.     

Strength and crack resistance of chromium-nickel-manganese 03Kh19AG3N10 steel in the temperature range 293–4.2 K

We present the results of the experimental investigation of the characteristics of strength and crack resistance of chromium-nickel-manganese 03Kh19AG3N10 steel in the temperature range 293–4.2 K under static (in the initial state and under the action of pulses of electric current) and dynamic loads. We consider some distinctive features of the process of the discontinuous yield of steel at a temperature of 4.2 K and its influence on the kinetics of fracture processes. The comparative analysis of temperature dependences of the characteristics of strength, plasticity, and crack resistance of 03Kh20N16AG6, 03Kh20N16AG6Sh, and 07Kh13N4AG20 steels extensively used in cryogenic engineering and 03Kh19AG3N10 steel demonstrates that 03Kh19AG3N10 steel can be used in the temperature range 293–4.2 K. Translated from Problemy Prochnosti, No. 3, pp. 90–95, May–June, 1997.     

Low-temperature strengthening of structural alloys under the action of strong magnetic fields

Results are presented for an experimental study of the effect of strong constant and pulsed magnetic fields on the mechanical properties and deformation features of steels 03Kh20N16AG6, 03KM3AG19, and 12Kh19N10T at temperatures of 293-4.2 K. Relationships are presented connecting the level of critical stresses with magnetic field parameters and the possibility is substantiated of using the low-temperature strengthening effect for steels in determining permissible stresses for structural elements subjected to the effect of strong magnetic fields.Translated from Problemy Prochnosti, No. 6, pp. 48–52, June, 1990.     

Effect of Deformation Rate on the Strength and Deformability of Alloys at 4.2 K

The results of investigating the effect of deformation rate and loading conditions in the presence of a prestrain on the parameters of low-temperature intermittent yield and the mechanical properties of the steels 03Kh20N16AG6 and 12Kh18N10T and the titanium alloy 3M have been considered, taking into account the stepwise development of jumplike deformation. Kinetic criteria of the loss of plastic-deformation stability are given, and the fracture conditions during deformation jump and after its end have been formulated. The necessity of improving the standards for testing materials under deep chilling conditions has been shown.     

Effect of modification of the surface on the hydrogen permeability of reactor steels and their welded joints

We study the characteristics of hydrogen permeability of 10Kh9VFA and 12Kh18N10T reactor steels in the intact state and in the presence of welds and analyze the influence of oxidation and irradiation with protons on these characteristics. It is shown that the proton irradiation increases the thermal stability and the degree of protection against the penetration of hydrogen into the oxidized specimens. To determine the contribution of the welds to the solubility of hydrogen, we apply, for the first time, a combined approach, namely, the diffusion coefficient of hydrogen in the weld is found according to the changes in the electric resistance in the process of hydrogenation and the hydrogen permeability of the welded joint is determined from the ratio of the areas of the base metal and the weld. It is shown that the oxide films with structures of chromium spinel formed on the surface of steels decrease their hydrogen permeability by 1.5–2 orders of magnitude.     

Crack resistance of chromium-nickel steels with impact loading under cryogenic temperature conditions

Results are presented for an experimental study of the effect of cooling to 77 K on resistance to crack development of chromium-nickel steels 12Kh18N10T and 03Kh20N16AG6 with impact loading. The crack resistance characteristics with a rate of crack growth of 1.5 m/sec were determined from the deformation diagram recorded during testing. Features are noted for crack advance with cooling under conditions of a dynamically applied load.Translated from Problemy Prochnosti, No. 7, pp. 26–29, July, 1992.     

Corrosion-Mechanical Properties of Materials for Reactor Vessels

We established that, in the course of electrolytic hydrogenation, an aqueous medium of boron regulation with pH 8 significantly accelerates the growth of fatigue cracks in 15Kh2MFA and 15Kh2NMFA hull steels, especially in the metal of welded joints, as a result of hydrogen embrittlement at the tip of a crack. An increase in the strength of steels by means of heat treatment, a decrease in the frequency of alternating loading, and an increase in the stress ratio significantly accelerate the growth of fatigue cracks. We discovered the strongest influence of hydrogenation in the near-threshold region for low values of the stress intensity factor. The tendency toward passivation and the anticorrosive properties of 15Kh2MFA steel (i _cor = 5 mA/m²) are higher than those of 15Kh2NMFA steel (i _cor = 20 mA/m²), which can be explained by the higher inhomogeneity of the structure of the latter. The metal of welded joints has the lowest cyclic corrosion crack resistance and the highest tendency toward hydrogen embrittlement under conditions of stable or transient modes.     

Effect of prior strain on serrated yielding of materials at 4.2 K

Results are considered of an experimental study of the combined effect of various factors (prior strain, loading system stiffness, and strain rate) on features of low-temperature serrated yielding of austenitic steels 03Kh20N16AG6 and 12Kh18N10T. It is shown that with high (quasistatic) loading rates r quite high accumulated elastic energy the presence of prior strain causes a quite sharp reduction in material strain resistance. This effect should be considered in evaluating the operating capacity of the rod structural elements under low-temperature conditions.Translated from Problemy Prochnosti, No. 8, pp. 12–20, August, 1995.     

Effect of aqueous media on the cyclic cracking resistance of steels at 300°C

We investigate the influence of reactor water (of the boron control system) on the fatigue crack growth rates in 15Kh2NMFA and 08Kh18N10T steels at 300°C. Corrosion-fatigue cracking is found to be typical of 15Kh2NMFA steel. The kinetics of the potentials of newly formed steel surfaces in high-temperature reactor water is studied. A phenomenological model that describes the influence of high-temperature aqueous media on the fatigue crack growth rates in steels is developed on the basis of data of corrosion-mechanical and electrochemical investigations. The results obtained by this model are in good agreement with experimental data.Karpenko Physicomechanical Institute, Ukrainian Academy of Science, L'viv. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 30, No. 1, pp. 34–42, January–February, 1994.     

Fatigue Strength of Austenitic and Martensitic–Ferritic Steels for Nuclear Power Plants

We study the influence of boron-controlled media (12 g/liter H₃BO₃) with pH = 3 and 8 at temperatures of 293 and 353°K on the fatigue and cyclic crack resistance of 08Kh18N10T and 12Kh18N10T austenitic steels and 14Kh17N2 martensitic–ferritic steel. It is shown that 14Kh17N2 steel is characterized by the optimal combination of the long fatigue life with high cyclic crack resistance in inert and corrosive media at temperatures of 293 and 353°K, which gives it serious advantages over 08Kh18N10T and 12Kh18N10T austenitic steels.     

Development of an austenitic chromium-manganese steel with high hydrogen resistance

We compare the results of studying the effect of hydrogen on the characteristics of short-time strength and low-cycle durability of austenitic stainless steels and age-hardening alloys. We show that austenitic stainless 06Kh20N16G6AF steel with solid-solution strengthening and the optimal content of nickel, manganese, and nitrogen possesses high mechanical characteristics and is least inclined to hydrogen degradation. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 5, pp. 95–100, September–October, 2005.