12Kh18N10T Steel Research Articles

Determination of the Mechanical Characteristics of the Metal of the Equipment of Nuclear Power Stations from Hardness Measurement and Indentation Data

The main normative documents for the nuclear power industry of Ukraine, which regulate the determination of mechanical characteristics from hardness measurement data, are considered and analyzed. It has been shown that the use of these documents for monitoring the technical condition of the equipment of nuclear power stations, in particular of the metals of the bypass pipeline of the high-pressure pump SAOZ of the core emergency cooling system (08Kh18N10T steel), coil from the welded joint zone of the Du 600 inlet branch pipe of the IRA30S02 non-return valve (16GS steel), and the body shell of the dismounted PV2500-97-10A (09G2S steel) high-pressure heater calls for their more detailed justification. To determine the mechanical characteristics of metals and to increase the reliability of their evaluation in nondestructive monitoring, a standard developed by the Pisarenko Institute of Problems of Strength of the National Academy of Sciences of Ukraine is used. According to this standard, the evaluation is made not only on the basis of hardness measurement data, but also by the method of instrumented indentation. It has been shown that this method is more efficient for the determination of the strength characteristics of steels. The difference between the ultimate strength and yield strength values according to this standard and those obtained in tensile tests is not over 8.6% and not over 6.6%, respectively. When diagnosing the technical condition of the metal of pipelines, indentation tests allow one to determine strength characteristics not only in the axial and tangential directions, but also in the radial direction.

The corrosion resistance investigation of the austenitic nitrogen Cr-Mn-Ni-Mo-N steel in the cast and deform state

In the article are given the analyzing corrosion resistance data of nitrogen containing steels. The resistance on the pitting, crevice corrosion with high nitrogen containing is estimated. The corrosion resistance of the steel 05Kh22AG15N8M2F in the condition after cold deforming in chloride containing substances is defined. Laboratory and field tests two types of steels 05Kh22AG15N8M2F and 12Kh18N10T are provided. It’s determined that the samples of the steel 05Kh22AG15N8M2F are demonstrating larger corrosion resistance at the laboratory and field investigations in comparison with the steel 12Kh18N10T. The properties of the steel 05Kh22AG15N8M2F with known AISI 316 are compared. It is established that the steel 05Kh22AG15N8M2F a top of AISI 316 on the resistance to the pitting corrosion and the critical pitting temperature. Pitting Resistance Equivalent (PREN) for the steel 05Kh22AG15N8M2F and the critical pitting temperature are determined.

Structure and properties of corrosion-resistant steel obtained by selective laser melting

The objects of study were stainless steel powder 12Kh18N10T of the 20–63 μm fraction and experimental samples obtained on the basis of it by selective laser melting (SLM). The powder was obtained by spraying with argon at a temperature of 1640 °C and a pressure of 27 bar. The particles have the dendritic-cellular structure, with a decrease in their size (<35 μm), the cellular structure prevails, and the dendritic one almost disappears. The distinctive particle size is d50 = 37 μm, d100 = 67 μm. The differential distribution curve is close to the Gaussian form, and asymmetry is associated with satellite and the presence of a small number of particles less than 20 microns in size. The fluidity of the powder was 3,27 g/s, and the bulk density was 4,41 g/cm3. The density of the 12Kh18N10T steel samples grown at the Concept Laser M2 facility with a laser power of 180 W and a speed of 700 mm/s averaged 7,89 g/cm3. Since the density of compact steel is 7,95 g/cm3, the obtained material has enough high density. The microstructure of the 12Kh18N10T sample was described by continuity, the absence of pores and cracks. It was a solid solution of austenite. The average size of coherent scattering regions in the grain volume was 19 nm. The observed arcuate boundaries of parallel semicircular tracks are due to heat removal during crystallization through SLM. The elongated crystallites in the tracks are oriented inward from this boundary. The microhardness of the samples in the transverse plane of the thin section is higher than the microhardness of the planar plane. But the microhardness of the samples obtained from the powder by the SLM is higher than that of the standard compact alloy. Tensile strength and elongation are 651 MPa and 47 %, respectively. The increase in strength is probably due to the grinding of structural parameters in SLM. The fracture surface of the samples is characterized by a pronounced viscous type.

Mechanical Properties Under Cyclic Loading of Rolled Ordered Materials Produced from Continuous Elastic Fibers. II. Fatigue Resistance, Vibration Strength, and Vibration Deformation

Ribbons with a porosity varying from 22 to 0.5% have been produced by rolling a multilayer knitted-mesh package made of 12Kh18N10T steel wire bundles 30 μm in diameter. Experimental and generalized analytical dependences of fatigue characteristics and their combinations on the porosity and rolling strain have been established using resonant cyclic loading techniques. Corrections have been introduced into the expressions for vibration strength and vibration strain to allow for the significance of their components.

Construction of deformation diagrams in experiments on impact compression of tablets-specimens with allowance for radial inertia

By means of the numerical modelling of the deformation process in axisymmetric formulation, using the LS-DYNA software complex, the influence of radial inertia on construction of dynamic deformation diagrams of different metals and alloys (12Kh18N10T steel, aluminium) at strain rates from 104 to 105 sec−1 is studied in this article. Using the experimental-computational method, the verification of Dharan and Hauser analytical method was carried out. It allowed to define twice precisely the contribution of the radial inertia forces in construction of the true dynamic deformation diagrams at impact loadings.

Corrosion of Various Types of Stainless Steel in Chloroaluminate Melts

The corrosion behavior of austenitic steels AISI 316L (analog of 03Kh16N15M3), 12Kh18N10T (analog of AISI 321) and 06KhN28MDT and ferritic and ferritic–martensitic steels 12Kh13 (analog of AISI 410), 08Kh17T (analog of AISI 439), and 16Kh12MVSFBR is studied in chloroaluminate melts at a temperature of 550°C. The corrosion rates of these steels in a KCl–AlCl3 electrolyte are determined. The corrosion damage of the stainless steel surfaces is shown to have a continuous inhomogeneous character and to be characterized by etching off the most electronegative elements, namely, chromium, iron, and manganese.

Additive Technologies for Design of Structural Materials on the Basis of the Nanocenter of the National Research Center Kurchatov Institute—CRISM Prometey

At present, additive technologies which employ metal-powder compositions of various alloys as building materials are in demand. These technologies in some cases represent the only tool during the construction and recovery of bulk products of almost any shape and degree of complexity. In this work, the structure and mechanical properties of the specimens fabricated via selective laser melting from the powders of 12Kh18N10T and 03Kh16N15M3 stainless austenite steels are evaluated.

Mechanical Properties Under Cyclic Loading of Rolled Ordered Materials Produced from Continuous Elastic Fibers. I. Elasticity and Energy Dissipation

Ribbons with a porosity varying from 22% to conditional 0.5% have been produced by rolling a multilayer knitted-mesh package made of 12Kh18N10T steel wire bundles 30 μm in diameter. Resonant cyclic loading techniques have been employed to plot the experimental dependences of the elastic and damping properties on the porosity and compressive strain of the material. It is shown that the main factor influencing the material’s properties is porosity when it is higher than 5% and plastic strain when porosity is lower than 5%.

Differentiation of the Multicomponent System Na,K,Sr∥Cl,NO3: Phase Diagram and Physicochemical Properties of Salt Mixtures in the System NaNO3—NaCl—KNO3—Sr(NO3)2

The differentiation of the quaternary reciprocal system Na,K,Sr∥Cl,NO3 was performed based on graph theory using special software. Stable and metastable complexes of the system were found using a matrix of reciprocal pairs of salts. For the first time, by physicochemical analysis methods (differential thermal, visual polythermal, and X-ray powder diffraction analyses using the method of thermal analysis of successive projections of the composition polytope), the quaternary system NaNO3-NaCl-KNO3-Sr(NO3)2, which is a stable complex of the quaternary reciprocal system Li,Ca,Ba∥F,WO4, was studied and the coordinates of invariant points were determined. The density and electrical conductivity were determined, volumetric changes were calculated, and the corrosion of 12Kh18N10T steel in eutectic and peritectic salt mixtures was investigated.

Formation of Transition Zones Under Spark Plasma Sintering of Dissimilar Steels

Results of mathematical simulation of the distribution of the concentrations of carbon and alloying elements in the zone of interaction of dissimilar microvolumes formed by spark plasma sintering of particles of steels 12Kh18N10T and U8 at various sintering temperatures and times, results of investigations of the structure of the specimens, and results of a regression analysis of experimental data are presented. The laws of formation of transition zones are described with the use of regression analysis based on the generalized lambda-distribution and on the method of truncated least squares. The processed data make it possible to identify the effect of the sintering mode on the structure of the transition zones. The results of the diffraction studies and their statistical analysis prove the results of the statistical simulation of the chemical composition.

Effect of Heating on the Structure, Phase Composition, and Micromechanical Properties of the Metastable Austenitic Steel Strengthened by Nanostructuring Frictional Treatment

The influence of heat treatment in the 100–900°С temperature range on the phase composition, structure, and micromechanical characteristics of the surface layer of the 12Kh18N10T steel subjected to nanostructuring frictional treatment (FT) with a sliding indenter has been studied. This study considered opportunities for strengthening metastable austenitic steel using combined thermomechanical treatments. Annealing at 400–450°C allows for the retention of nanocrystalline martensitic–austenitic structures formed in the surface layer of the steel and a significant increase in the micromechanical characteristics owing to the strengthening of the strain-induced martensite. The annealing of the steel at 650°C leads to the formation in the surface layer of an austenitic predominantly submicrocrystalline and nanocrystalline structure with a hardness of 630 HV 0.025, which is almost 3 times higher than the hardness of steel in the initial quenched state. The transmission electron-microscopic studies of the surface layer of the austenitic steel deformed by FT made it possible to reveal the retention of highly dispersed austenitic regions in addition to the recrystallized regions upon heating to 800°C, as well as the absence of abnormal growth of recrystallized austenite grains upon heating to 900°C.

Study of a Welded Joint of 12Kh18N10T Steel Using Acoustic and Magnetic Methods

The paper presents results from studies on the influence of plastic deformation on magnetic and acoustic characteristics of a welded joint material of 12Kh18N10T (analogue AISI 321) austenitic steel. We have shown that an inhomogeneous structure in the heat-affected zone causes a nonuniform distribution of acoustic parameters and magnetic properties of the welded joint material. The formation of the martensitic phase occurs upon plastic deformation, which influences the properties of the whole material and has elastic moduli differing from that of the original austenitic phase. The increase in the volume fraction of martensite leads to the decrease in the elastic moduli of the material and, as a consequence, to the decrease of ultrasonic waves velocity. The variation of ultrasonic waves velocities leads to significant errors upon measurements of the material parameters under study, for instance, of a sheet thickness using ultrasonic thickness measurement. The formation of martensite changes also the magnetic properties of the material. We have found the dependence of the shear ultrasonic wave velocity on a parameter governed by the change in the phase composition of the austenitic steel upon plastic deformation. We have developed an algorithm for the determination of the thickness of the welded joint metal undergoing pressure forming and plastic deformation upon operation of constructions. We have shown that the additional measurement using the magnetic method of the parameter governed by the change in the phase composition of the steel upon deformation substantially decreases the errors of the thickness measurement of the welded joint metal.

Application of the internal protective layer from stainless steel to the surface of long-length pipes with an explosive welding

This study is devoted to obtaining long-length two-layer corrosion-resistant tube blanks by explosion welding for their subsequent rolling into tubing. The technological scheme of the process was developed, which allowed ensuring high-quality adhesion of the internal corrosion-resistant layer from austenitic stainless steel 08Kh18N10T with a tube blank made of 37G2F hollow structural steel. In the course of study on the experimental production of bimetallic pipes of 2.4 meters in length, the following problems were solved: 1) the choice of optimal collision regimes of the tube elements thrown on each other; 2) the development of the necessary technological equipment to maintain the alignment of the main elements; 3) ensuring full filling of the internal surface of the device with solid-liquid filler without contact with the welding gap (sealing with welded joints); 4) reducing the degree of lateral dispersion of the explosive due to the assembly enhancing in the ground and use a metal formwork; 5) estimation of the relative narrowing of the outer diameter of the bimetallic tube after explosion welding; 6) carrying out ultrasonic control of the continuity of connection of the obtained two-layer pipes in order to reveal the mistreatment zones along the length of the blanks.

Forging of High-Alloy Steel Ingots

The forging of high-alloy 13Kh17N14M3 and 08Kh18N10T steel ingots (mass 5.3, 1.5, and 1.2 t) is considered. Five forging technologies based on microshear are considered: natural shear in forging by traditional tools, insertion hammers; and hybrid hammers; and applied shear in forging by hammers with working surfaces that cross in the transverse vertical plane. In forging with macroshear, the reduction is 1.78, while the total reduction in the ingot is 2.44. For all the forgings, the deformation of the metal is satisfactory, with no residual cast structure. The mechanical properties of the metal considerably exceed the standard requirements.

Influence of the External Polarization Potential on the Tribocorrosion Behavior of 08Kh18N10T Steel

We study the influence of external polarization with different potentials on the tribocorrosion behavior of 08Kh18N10T steel in contact with a corundum ball in a 3% NaCl solution. It is shown that the mechanical factor shifts the potential of pitting formation to the negative side by 0.17 V as compared with the surface without friction. The running-in time, friction coefficient, and material losses in the process of tribocorrosion qualitatively correlate with each other and depend on the applied electrode potential. It is shown that hydrogen released in the contact zone under the conditions of cathodic polarization embrittles the surface layers participating in the contact interaction. Moreover, hydrogen reduces oxide films and prevents their rapid formation on steel, which intensifies its wear. In addition, hydrogen facilitates deformation and increases the deformation zone near the friction track. Under the anodic polarization, we observe an increase in the number of pits in the friction area.

High Temperature Corrosion of 12Kh18N10T Steel in Molten Lithium and Potassium Chlorides with a Cerium Trichloride Addition

The high temperature corrosion of the 12Kh18N10T steel in molten lithium and potassium chlorides with a cerium trichloride addition is studied at 773 K. The CeCl3 concentration is varied from 0.2 to 5 mol %. Cerium is used as an analog of plutonium. The electrolyte composition is close to the compositions of the real electrolytes used for processing of nitride spent nuclear fuel. The main research method is gravimetry, with holding a steel sample in a melt for 1–24 h. In addition, atomic adsorption and electron-probe microanalysis are used.

Corrosion of 12Kh18N10T Steel in the LiCl–KCl–nNdCl3 Melt

The high-temperature corrosion of a 12Kh18N10T steel in the melt of lithium and potassium chlorides and neodymium trichlorides is investigated at a temperature of 773 K. The NdCl3 concentration is varied from 0.2 to 5 mol %. In this study, neodymium is an analog of uranium. The composition of the electrolyte is close to the composition of the electrolytes used for processing nitride spent nuclear fuel (SNF). The main investigation technique is gravimetry, which includes aging of the steel in the melt for 1–24 h. Atomic absorption and electron microprobe analyses are also used.

Adhesive-Strength Evaluation via the Pull-Out Method in a Binder—Elementary-Filament System at Various Treatments of Filaments

The adhesive strength of binders with elementary filaments that have been used for the production of LUP carbon tape covered by different types of coatings is evaluated via the pull-out method. Two types of single-layer coatings are considered, one of which is based on titanium of the VT1-0 brand while the other is made of 12Kh18N10T steel, as well as a bilayer coating composed of a titanium layer coated by a stainlesssteel layer. The adhesive strength is determined for thermoreactive (epoxy with amine hardener) and thermoplastic (polyamide) types of binders. The best adhesive strength (more than 30%) of binders is achieved when the LUP carbon tape is covered with stainless steel.

Studying the Effect of Microscopic Medium Inhomogeneity on the Propagation of Surface Waves

Based on the analysis of literature data, it has been shown that a system of microcracks rapidly nucleates and develops in a surface layer of several grain sizes under fatigue loading. This brings about changes in the elastic modulus and density of the material. These can be described in the form of material’s effective characteristics. The problem of the propagation of a surface wave has been solved for a microscopically inhomogeneous medium with dispersion and insignificant surface-layer variations. Using the example of testing 08Kh18N10T steel samples for low-cycle fatigue, it has been shown that the propagation speed of surface waves changes at a higher rate than that of bulk (longitudinal and shear) waves; this can be used in the tasks of testing materials at early stages of fatigue failure.

Structure of a Carbon Steel–Stainless Steel Bimetal

Bimetallic samples may be produced by casting St3 structural steel between sheets of Kh18N9T stainless steel in a mold, with subsequent hot rolling of the three-layer sheet. Such samples have a structure in which Kh18N9T stainless steel appears at the outer edge on both sides, while the core consists of St3 structural steel. Analysis of the boundary between the steels confirms the absence of defects: it is continuous and of high quality. The microstructure of the junction is investigated by optical, scanning-probe, and electron microscopy. Three structural components are observed from the pearlitic to the austenitic steel: a weakened section of the ferritic layer; a strengthened section of the ferritic layer; and a dark-etching layer at the austenitic steel. The following results are obtained by scanning-probe microscopy—in particular, the constantforce contact method—and optical metallography: on approaching the boundary from the St3 steel, a carbon- free layer with purely ferritic structure is observed, rather than the usual structure for low-carbon steel, which consists of a ferrite matrix with pearlite colonies. On approaching the boundary from the Kh18N9T steel, a carburized layer is observed. In addition, the boundary includes an intermediate carbide layer (depth up to 50 μm). The change in microhardness in the region where the St3 structural steel meets the external layer of Kh18N9T stainless steel indicates considerable increase in strength of the materials. Elemental microanalysis of the St3 steel–Kh18N9T steel boundary reveals the change in concentration of the alloying elements on approaching the boundary. The presence of chromium in St3 steel and the increase in carbon concentration in Kh18N9T stainless steel confirm that two opposing diffusional fluxes are formed: the diffusion of carbon from the St3 steel; and the diffusion of alloying elements from Kh18N9T steel. The resulting carbides explain the increased hardness of both steels close to the boundary.