12Kh18N10T Steel Research Articles

Predicting the Effects of Cryogenic Treatment and Impact-Oscillatory Loading on Changes in the Strength Properties of Stainless Steels

Abstract New experimental results concerning the strength properties of stainless steels are analyzed. In particular, the strength properties of steels were improved at room temperature using the preliminary impact-oscillatory loading (IOL) in liquid nitrogen. Mechanical tests performed on stainless steel 12Kh18N10T have found the IOL conditions (deformation of the material during pulse loading—εimp = 9.69%), under which the ultimate strength of steel increases by 32.2% compared to the initial state under subsequent static tensioning. Metallographic analysis of the deformed steel revealed twinning in the microstructure. This accounts for a significant increase in ultimate strength under subsequent static tensioning. A method for estimating the ultimate strength of stainless steels of different chemical compositions by changing the percentage of the main chemical elements is proposed. To test this technique, stainless steel 12Kh18N9 was chosen. Similar studies using this steel at εimp = 9.5% in liquid nitrogen followed by static tensioning at room temperature have confirmed the effectiveness of the proposed approach.

The effects of cryogenic treatment and impact-oscillatory loading on changes in the mechanical properties and structural condition of stainless steel 12Kh18N10T

Research findings are presented dealing with the combined effect of cryogenic treatment + impact-oscillatory loading applied in different sequences on changes in the mechanical properties of stainless steel 12Kh18N10T. One-hour long cryogenic treatment and impact-oscillatory loading (IOL) applied at room temperature were shown to be practically unable to change the mechanical properties of the steel. At the same time, IOL pre-applied at a temperature of liquid nitrogen followed by static tensioning at room temperature proved to cause significant changes in the mechanical properties of the steel. Under further static tensioning, when IOL εimp = 2.7 … 12.5 % (assigned intensity range of introducing impulse energy into steel) or, more specifically, when εimp = 9.69 %, the ultimate strength of the steel was found to reach its maximum value, increasing by 32,2 % compared to baseline, while ductility decreased by 26 %. Specific physical investigations using the TEM microscope were conducted. The analysis of the steel structure of a specimen pre-subjected to IOL in liquid nitrogen at εimp = 9.63 % indicates that under such complex loading conditions the well-known mechanism of plastic deformation by sliding changes into plastic deformation by twinning upon further static tensioning, and the strength of the steel increases.

The effect of various types of hot plastic deformation on the structure formation of a pipe billet made from 08Kh18N10T steel

The effect of various types of hot plastic deformation on the structure formation of a pipe billet made from 08Kh18N10T steel

Causes of low casting ability for continuously cast billets from 08Kh18N10T steel and development of measures directed on increase of casting sequence

Causes of low casting ability for continuously cast billets from 08Kh18N10T steel and development of measures directed on increase of casting sequence

Accelerated corrosion tests of a contact pair austenitic stainless steel – titanium alloy

The results of accelerated corrosion tests of a pair of austenitic stainless steel — titanium alloy under conditions of elevated temperatures and high concentrations of corrosive agents are presented, conditions for the developing the mechanism of local corrosion being the same. The proposed approach included provoking the appearance of microstress concentrators by three-point loading of test samples with subsequent forced development of local types of corrosion through simultaneous exposure to an increased concentration of corrosive agents and temperatures at a fixed exposure in an autoclave. The results of modeling the corrosion process in a titanium alloy being in contact with stainless steel are assessed proceeding from the data obtained from metallographic studies of the state of surface layers of the metal and the morphology of corrosion products on prepared sections of the surface of templates cut from the samples under study. We considred a pair of steel 08Kh18N10T — titanium alloy VT-5. It is shown that the contact of samples under conditions of accelerated corrosion tests does not lead to a significant development of local types of corrosion of the titanium alloy. On the contrary, analysis of the state of the surface layers of the samples of stainless steel revealed the presence of deep corrosion pits, triggering the intergranular corrosion. In this case, corrosion of austenitic steel, both in the presence and in the absence of contact with titanium, proceeded in three stages: the initiation and fusion of pitting; formation of knife corrosion ulcers; propagation of intergranular cracks into the depth of steel. The proposed methodology of corrosion testing can be used to predict the possible nature of the development of metal corrosion under operating conditions that form local zones of static stresses in structural materials, and for prompt response to extend the design life of the equipment at thermal and nuclear power facilities.

Chemical Vapor Deposition of Tantalum Carbide in the TaBr5–CCl4–Cd System

The tantalum carbide coatings were deposited on substrates made of 12Kh18N10T steel, ZhC6 alloy, and molybdenum by reduction of TaBr5 and CCl4 vapors with cadmium vapors at temperatures of 950–1000 K. The average deposition rate of coatings on molybdenum was ~5 μm/h, on ZhC6 alloy was ~6 μm/h, and on 12Kh18N10T steel was ~8 μm/h. The coatings were formed as columnar grains on the substrate surface and as a diffuse layer in the substrate material. The surface layers contained mainly tantalum monocarbide TaCy (y = 0.72–0.86) and a small fraction of tantalum. The coatings on the surface of ZhC6 alloy and 12Kh18N10T steel flaked off with increasing thickness, which was due to different thermal expansion of the coating and substrate, as well as concentration inhomogeneity and phase transitions in the substrate material during coating deposition and during the heating and cooling processes.

STUDY OF THE RELATIONSHIP BETWEEN FATIGUE CHARACTERISTICS AND ELASTIC MODULUS OF METASTABLE AUSTENITIC STEELS

This work is devoted to studying the influence of cyclic deformation on the elastic moduli of metastable austenitic steel. The estimated calculation of the modules of the strain-induced martensite and the modules of the matrix of the material (austenite) in the Voigt approximation. The modulus calculations were made according to the ultrasonic wave velocity measurements taking into account changes in the density of the material due to the difference in the volumes of the unit cells of the matrix and the ??-martensite. The volume fraction of ??-martensite and its change during cyclic deformation were determined by the eddy-current method. The influence of the strain cycle amplitude on the increase in the volume fraction of martensite was studied. The dependences of the relative change in Young's modulus, shear modulus, volume compression modulus on the number of loading cycles for metastable steel 12Kh18N10T are given. Relationships between the moduli change and the characteristics of cyclic loading of steel are obtained: the hardening of the material and the energy density in the cycle, used to calculate the service life using the methods of deformable solid mechanics. Studies shown that the critical change in the modules corresponding to the appearance of a microcrack depends on the strain cycle amplitude.The maximum change in the modules of metastable steel 12Kh18N10T was 4.5%; that by an order more than in steels that don't undergo phase transformations. A high degree of correlation between the change in elastic moduli and the fatigue characteristics of metastable austenitic steel is revealed: the hardening of the material and the energy density in the cycle. Correlations between the fatigue life of 12Kh18N10T steel and the change in elastic modulus – shear modulus and Young's modulus are obtained, which makes it possible to assess the state of the studied steel based on acoustic measurements.

Effect of long-term exposures at elevated temperature on heat resistance of 08Kh18N10T steel

Effect of long-term exposures at elevated temperature on heat resistance of 08Kh18N10T steel

Study of electrochemical properties of austenitic chromium-nickel steel 12Kh18N10T in concentrated sulfuric acid

Study of electrochemical properties of austenitic chromium-nickel steel 12Kh18N10T in concentrated sulfuric acid

Electrochemical Treatment of the Surface of 12Kh18N10T Steel Parts Produced by Selective Laser Melting

Electrochemical Treatment of the Surface of 12Kh18N10T Steel Parts Produced by Selective Laser Melting

Strength and Relaxation and Corrosion Resistance of Ultrafine-Grained Austenitic 08Kh18N10T Steel Produced by ECAP: III. Deformation Behavior at Elevated Temperatures

Strength and Relaxation and Corrosion Resistance of Ultrafine-Grained Austenitic 08Kh18N10T Steel Produced by ECAP: III. Deformation Behavior at Elevated Temperatures

Fretting Wear of Metal–Metalopolymer Friction Couples

Test results on fretting wear of metalopolymer materials in a friction couple with structural materials—cast iron 20 and stainless steel 12Kh18N10T—performed over the direct and reverse test schemes are presented. As the metalopolymer material, we took the BELZONA 1111 two-component paste-like material based on a mixture of a metal–ceramic alloy with high-molecular polymers and oligomers.

DIAGNOSTICS OF INTERELECTRODE GAP’S CONDITION USING VIBROACOUSTIC EMISSION

This work is devoted to the study of the interelectrode gap’s condition during wire electrical discharge machining. The experiments were carried out on workpieces made of chromium-nickel anti-corrosion steel 12Kh18N10T and duralumin D16 with a brass tool CuZn35 with a diameter of 0.25 mm in deionized water. The developed diagnostic tool based on vibroacoustic emission recorded oscillations with a frequency of 4 … 8 kHz accompanying the processing.

Strength and Relaxation and Corrosion Resistance of Ultrafine-Grained Austenitic 08Kh18N10T Steel Produced by ECAP: II. Relaxation Properties and Intergranular Corrosion Resistance

Strength and Relaxation and Corrosion Resistance of Ultrafine-Grained Austenitic 08Kh18N10T Steel Produced by ECAP: II. Relaxation Properties and Intergranular Corrosion Resistance

Improving shape formation under conditions of plane tensile stress

Thin-walled axisymmetric truncated parts made of sheet billets are actively used in rocket and aerospace engineering. Improvement to their shape formation, based on directed material thickness change will ensure the production of parts with minimum thickness variation. This will also enable aviation and space industry enterprises to attain leading positions, as well as reduce labor costs. This work studies the possibility of obtaining thin-walled axisymmetric parts of truncated tapered shape using one of the methods of sheet metal stamping under flat tensile stress conditions (flanging). The mechanism was identified and the analysis of the stress-strain state of the billet during deformation was carried out. This takes into account the minimizing of the difference between the specified and technologically possible thicknesses. A mathematical model was developed to consider the shaping method based on the process of flanging. Theoretical studies were based on the principles of the plastic deformation theory of sheet materials. This was achieved by the following factors: approximate differential equations of force equilibrium; equations of constraint; plasticity conditions; and fundamental constitutive relations under given initial and boundary conditions. The process of flanging was simulated using the LS-DYNA software package with the following initial data of a conical billet made of 12Kh18N10T steel: cone angle 16.4°, thickness Sbillet = 0.3 mm. The aim was to eliminate errors in designing a tool for future implementation of the method on a manufactured die tooling, as well as to confirm the theoretical conclusions on the selection of technological parameters and achieve minimal thickness variation. The steps of computer modeling are presented, indicating the main process parameters such as material model, mechanical characteristics of the workpiece material, type of elements, kinematic loads, conditions of contact interaction of elements with each other, etc.

Corrosion Behavior of 12Kh18N10T Steel in the LiCl–KCl Melt Containing f-Element Chloride Additives

Corrosion Behavior of 12Kh18N10T Steel in the LiCl–KCl Melt Containing f-Element Chloride Additives

Strength and Relaxation and Corrosion Resistance of Ultrafine-Grained Austenitic 08Kh18N10T Steel Produced by ECAP: I. Microstructure and Strength

Strength and Relaxation and Corrosion Resistance of Ultrafine-Grained Austenitic 08Kh18N10T Steel Produced by ECAP: I. Microstructure and Strength

The impact of residual technological stresses on the opening and stability of through cracks in pipeline elements

The impact of residual stresses in a DN850 pipe (steel 10GN2MFA) with austenitic cladding, welding stresses in the mounting annular seam of the pipeline, and residual stresses arising in a curvilinear branch DN350 (steel 08Kh18N10T) during manufacture by plastic deformation on the opening and stability of through cracks is considered. Calculations of residual stresses are performed using the finite element method (FEM). It is shown that residual stresses cause a change in the size and shape of the outflow channel, the coolant flow rate, and the value of the J-integral at the crack tip. In case of short cracks and relatively low operating stresses, the crack edges can close on the inside of the pipe wall due to the action of residual stresses thus leading to a decrease or cessation of the leak. A reversed effect of residual stresses on extended cracks is observed at rather high operating stresses: change in the shape of the outflow channel (an increase in the opening of the crack edges on the outer surface of the pipe) leads to a decrease in the friction of the coolant flow against the crack edges and, hence, to an increase in the leak volume. The results of testing full-scale models of elements of a straight section of the pipeline with a welded seam and a curvilinear branch DN350 with artificially created defects by internal pressure and bending moment are presented. It is shown that local through cracks develop from initial defects, which remain stable at maximum design loads (normal operating conditions plus maximum design earthquake) which matches the calculation results and meets the requirements of the applicability of the concept of «leak before break».

Qualitative Phase Analysis of Oxide Films on a Steel 12KH18N10T Surface Formed as a Result of Applied Laser Marking

Qualitative Phase Analysis of Oxide Films on a Steel 12KH18N10T Surface Formed as a Result of Applied Laser Marking

Formation of TiN coatings by air plasma spraying

Titanium nitride (TiN) coatings were obtained on the surface of 12Kh18N10T steel by air plasma spraying (APS) of TiN powders using an arc plasmatron made by the authors. The plasmatron has a node of circular input and gas-dynamic focusing of the powder and the output apertures of the nozzle-anode are made in the form of rectangular narrowing-expanding channels (No.34334 RK: IPC H05H 1/42). A study of operation modes of a plasmatron for spraying of powder coatings was carried out. The structural-phase state, microhardness and wear resistance of TiN coatings were systematically investigated. The optimum APS operating mode for deposition of TiN powder was determined: current 250 A, voltage 68 V, argon gas flow 34 L/min, spraying distance 150 mm. To reduce the oxidation of TiN powder in the APS process, a method of creating a nitrogen environment at the outlet of the anode nozzle, nitrogen flow rate 2.3 bar was used. The results of structural analysis showed that TiN is the main phase of the coating. The mechanism of formation of TiN structures was characterized by analyzing SEM results of TiN coating surface morphology and TiN droplets sprayed on the surface of the sample. The results showed that the TiN(1) coating has better wear resistance than the TiN(2) and TiN(3) coatings. The cross-sectional and longitudinal microhardness of the TiN coating was investigated. The highest cross-sectional hardness of TiN coating is 1250 HV0.1, which is in accordance with mode 1.