To evaluate the effect of yield stress on hydrogen embrittlement (HE) of martensitic and ferritic steels, the effect of hydrogen (H) capture by structural inhomogeneities (hydrogen traps) and the effect of plastic deformation and stress on the mechanism of stress corrosion cracking (SCC) are considered. In the presence of hydrogen, the brittle fracture of high-strength martensitic steels consists of flat areas of intergranular fracture at the initial austenitic grain boundaries and quasi-brittle cracks at the boundaries of martensite blocks. In low-strength steels, brittle fracture manifests itself in the form of transgranular fracture of ferrite grains. The decrease in the characteristics of martensitic steels with an increase in the yield strength occurs due to an increase in the hydrogen concentration at the stage of anodic dissolution (AD) due to the growth of the carbide/matrix interface. The reason for the growth hydrogen concentration in ferritic steels is a large mechanical overstress, an increase in the number of active dissolution centers, the formation of an electrochemical pearlite-ferrite pair, and an increase in surface roughness with increasing deformation. It is concluded that the bell-shaped dependences of the critical stress of the transition from AD to SCC and other characteristics of mechanical tests on magnitude of the yield stress are due to different mechanisms of hydrogen accumulation in martensitic and ferritic steels.

The features of diffusion in two-phase (duplex) stainless steel (DSS), interaction the effect of hydrogen with trap sites in various steel structures, the influence of plastic deformation, local stresses and hydrogen concentrations on localized corrosion and hydrogen embrittlement Available data indicate that the diffusivity of DSS is insensitive to plastic deformation and increase in dislocation density, but it is influenced by grain boundaries and interfaces α/γ-phases The influence of hydrogen on stability is considered γ-phases, formation of second phases and hydrogen trap semi-coherent grain boundaries. The mechanisms that ensure crack propagation are discussed: brittle, associated with decohesion in the region of maximum hydrostatic stress, and plastic in the austenite phase—due to shear decohesion along the slip plane. Reviewed the influence of the yield stress of duplex steel on the susceptibility to hydrogen embrittlement, as well as on correlation of the steel embrittlement index with the total amount of absorbed hydrogen.

To evaluate the effect of yield stress on hydrogen embrittlement (HE) of martensitic and ferritic steels, the effect of hydrogen (H) capture by structural inhomogeneities (hydrogen traps) and the effect of plastic deformation and stress on the mechanism of stress corrosion cracking (SCC) are considered. In the presence of hydrogen, the brittle fracture of high-strength martensitic steels consists of flat areas of intergranular fracture at the initial austenitic grain boundaries and quasi-brittle cracks at the boundaries of martensite blocks. In low-strength steels, brittle fracture manifests itself in the form of transgranular fracture of ferrite grains. The decrease in the characteristics of martensitic steels with an increase in the yield strength occurs due to an increase in the hydrogen concentration at the stage of anodic dissolution (AD) due to the growth of the carbide/matrix interface. The reason for the growth hydrogen concentration in ferritic steels is a large mechanical overstress, an increase in the number of active dissolution centers, the formation of an electrochemical pearlite-ferrite pair, and an increase in surface roughness with increasing deformation. It is concluded that the bell-shaped dependences of the critical stress of the transition from AD to SCC and other characteristics of mechanical tests on magnitude are due to different mechanisms of hydrogen accumulation in martensitic and ferritic steels.

The influence of metallurgical factors on stress corrosion cracking of steels of different classes in an aggressive NACE solution at 25°C is analyzed. The dependences of the stress leading to the transition from active corrosion to the mechanism of hydrogen embrittlement (critical stress) on the yield stress and the coefficient of stress concentration are plotted. The relationship between the critical stress, conditional yield stress, and overstress values is revealed. It is concluded that the loss of corrosion resistance for unalloyed steels with a yield stress below 500 MPa is caused by an increase in the hydrogen concentration during deformation of the material in a corrosive environment.

Проведен анализ влияния металлургических факторов на коррозионное растрескивание под напряжением сталей разного класса в агрессивном растворе NACE при 25oC. Получены зависимости напряжения перехода от активной коррозии к механизму водородного охрупчивания (критического напряжения) от величины предела текучести и коэффициента концентрации напряжений. Выявлена связь между критическим напряжением, условным пределом текучести и величиной перенапряжения. Сделан вывод о том, что потеря коррозионного сопротивления для нелегированных сталей с пределом текучести ниже 500 MPa обусловлена увеличением концентрации водорода в процессе деформации материала в коррозионной среде. Ключевые слова: коррозионное растрескивание под напряжением, водородное охрупчивание, предел текучести, коэффициент стойкости, сталь.

The analysis of data on stress corrosion cracking of different classes steels in sour H2S-CO2-Cl- solutions is carried out. The dependence of the time to failure and speed of stationary corrosion on the outside (the concentration of the solution components, temperature, the value of the tensile stress) and internal (the degree of alloying of Cr, Ni, Mo, the yield strength of steel) of the corrosion parameters is obtained The resulting expression will allow to evaluate the corrosion behavior and the possibility of using steel in an aggressive environment without long and expensive field tests.

We have analyzed the data on stress corrosion cracking of steels of various grades in acidic H2S–CO2–Cl– solutions. For the active region of corrosion, we have obtained the dependence of the lifetime and the steady-state corrosion rate on external (concentration of solution components, temperature, and tensile stress) and internal parameters of corrosion (Cr, Ni, and Mo doping level and conditional yield stress for steel). The resultant dependences will make it possible to estimate the corrosion behavior and the possibility of using steel in an aggressive environment without resorting to durable and costly natural tests.

The effects of various parameters on metabolism was analyzed in several homeothermic animals, including mammals, passerine birds, and humans. A Boltzmann equation was obtained for the basal metabolic rate, with the activation energy coinciding in magnitude with the energy of enzymatic cleavage of macroergic P–O bonds in adenosine triphosphate acid molecules. A dependence was obtained to relate the lifespan with the body temperature, body mass, basal metabolic rate, and Rubner’s constant.

The influence of the dislocation mobility on the creep rate in aluminum has been estimated. In a steady state of creep, the dislocation mobility is varied by pinning dislocations using impurity atoms during heating. It has been shown that the change in the creep rate is proportional to the fraction of impurity atoms that migrate from the solid solution of deformed aluminum toward the dislocations.

The parameters of intergranular fracture of copper during creep under tension at T = 773 K and σ = 12.5 MPa are determined, and the contribution of grain-boundary porosity to the increase in the creep rate at stage III is estimated. The increase in the creep rate is shown to occur due to the pore-induced decrease in the grain boundary area, an increase in the mobile-dislocation density, and the deformation of the material because of the formation of pores and cracks.

The effect of uniform pressure on the activation parameters of the kinetic equation that describes the exponential dependence of the steady-state creep rate and the lifetime of polycrystalline metals on stress and temperature is estimated. It is shown that, under pressure, the parameters that determine the behavior of a metal under load are the activation energy and the internal stresses. The dependence of these parameters on the applied pressure is revealed.

A parameter is proposed to estimate the possibility of pore coalescence in deformed materials. It is shown that pore accumulation does not lead to the formation of macrocracks and subsequent fracture during uniaxial loading in the region of an exponential relation between the strain rate and the stress.

The influence of omnidirectional pressure on microporosity developing in the neck of 45-μm-thick copper sheets tested for creep is considered. Comparing these data with a porosity measured in cylindrical specimens leads us to conclude that the transition from cleavage failure to shear fracture observed in copper under pressure is related to a decrease in the mean hydrostatic tension in the neck.

The activation parameters are estimated at the steady stage of creep during tension of aluminum and lead in the range of the exponential and power stress dependences of the steady-state creep rate. A jump of the effective activation energy is shown to occur in the stress dependence of the creep rate at T ⩾ 0.5 T m . This jump is approximately equal to the difference between the activation energies of self-diffusion and pipe diffusion.

The results of estimation of activation parameters in the region of exponential (I) and power (II) dependences of the steady-state creep rate of polycrystalline copper on stress were represented. It is shown that the elastic long-range stress produced by dislocations in region I can be determined directly from the dependence of the creep rate on the stress. An energy criterion of the transition from creep region I to region II is proposed.

The fracture activation energy is determined from the stress dependences of the lifetimes of Al and 6h-Fe measured at moderate and low test temperatures. The shear stresses are analyzed with allowance for the temperature dependence of the shear modulus and the athermal component of stresses.

The effect of various types of intermediate plastic deformation on the high-temperature creep of polycrystalline aluminum is studied. Intermediate deformation is performed after testing for 0.44 of the time to failure t f via the single or multiple action of a hydrostatic pressure of 1000 MPa on porosity or via tension or compression at atmospheric pressure. Intermediate deformation is shown to decrease the creep rate, to increase the time to failure, and to increase the grain size. The change in the creep rate is maximal upon the cyclic (in the same test time intervals) action of pressure. A relation between the creep rate and the grain size has been reveled. The detected decrease in the creep rate is assumed to be caused by a decrease in the density of mobile dislocations (due to recrystallization).

The intermediate action of hydrostatic pressure on the high-temperature creep of copper is studied at various creep stages. Tests performed at a constant tensile stress of 12.5 MPa at 773 K show that the application of a pressure at the creep third stage decreases the steady-state creep rate and extends the time to failure. At the steady-state stage of creep, the effect of the pressure may be ignored. At pressures of up to 1 GPa, this effect is found to be only related to healing of grain-boundary porosity. At higher pressures, the steady-state creep rate is governed by porosity healing and structural changes.