Austenitic 12Kh18N10T Research Articles

Roughness of the nuclear reactor pipe inner surface depending on the reactor operating time

During operation of nuclear reactors, there are various factors that affect the nuclear plant piping leading to erosion of the pipe inner surface and an increase of its micro-relief (roughness). Metal corrosion occurs and spreads faster on a surface having a higher value of the roughness parameter. Failure through erosive wear of the parent metal takes place predominantly in the pipe bend area. The roughness of the pipe inner surface has a sizeable effect on the signal attenuation in the process of the pipe wall ultrasonic testing. Defective main pipeline segments were cut out during preventive repairs from which samples with different operating times were taken. Five defective pipe segments of the austenitic 12Kh18N10T grade steel cut out of a high-pressure reheater’s piping and five defective pipe segments of the perlite-class steel of grade 20, after different operating times, were used to determine experimentally the actual value of the pipe inner surface roughness. Besides, a piece of a new Ø273 × 12 pipe of the 12Kh18N10T steel and a piece of a Ø159 × 6 pipe of grade 20 steel were cut out. The inner surface roughness was measured for different segments. Dependences of the roughness value on the operating time and the pipe segment type have been obtained. Company specimens were fabricated with the inner surfaces having the roughness corresponding to various pipe operating times. This made it possible to take into account the influence of the inner surface roughness on the signal attenuation in the process of the weld integrity ultrasonic testing and during ultrasonic measurements of the weld adjacent zone grain size value following the weld repair.

Study of structural non-homogeneity impact on mechanical properties of dissimilar weld joints of carbon steel 20 and corrosion-resistant austenitic 12Kh18N10T steel

The paper is devoted to identifying features of structural non-homogeneities formation in dissimilar welded joints of carbon steel 20 to corrosion-resistant austenitic 12Kh18N10T steel, obtained by tungsten inert gas welding (TIG), as well as studying of their influence on the mechanical characteristics of welded joints under static and cyclic loading. Differences in the formation of a diffusion carbide interlayer in weld metal alloyed with nickel and manganese are established. When austenite is alloyed with nickel, bulk carbon diffusion occurs, while in manganese austenite boundary diffusion becomes the main mechanism for carbon diffusion, which occurs mainly along grain and sub-grain boundaries of austenite. As a result of mechanical tests, it was established that under static tension welded joint works under conditions of strengthening by a soft (ferritic) layer due to the restraint of transverse deformations by more solid (carbide) layer. The limits of soft interlayer dimensions, under which the softening of welded joint does not occur, are established that will allow to proceed to the extreme temperature-time parameters of heat treatment and operation of welded joint.

Повышение трибологических свойств аустенитной стали 12Х18Н10Т наноструктурирующей фрикционной обработкой

Повышение трибологических свойств аустенитной стали 12Х18Н10Т наноструктурирующей фрикционной обработкой

Numerical 3D-modeling of spall and shear fractures in shells of austenitic 12Kh18N10T steel and 30KhGSA steel under their spherical and quasi-spherical explosive loading

To pursue VNIIEF–VNIITF joint investigations, this paper briefly describes the experimental setup and provides numerical 3D-computation results (LEGAK-3D technique) on special features in the convergence dynamics of steel shells under their quasi-spherical explosive loading in the system with the 40-mm outer radius of the explosive layer. The computation results were compared with the data experimentally registered for shells of the 30KhGSA steel, both as-received and quenched to HRC 35…40, and the austenitic 12Kh18N10T stainless steel. The comparison was also made with laser-interferometry results obtained directly under explosive loading, as well as with gamma-tomography and scanning electron microscopy investigations of the recovered shells.

Cumulation of a spherically converging shock wave in metals and its dependence on elastic-plastic properties, phase transitions, spall and shear fractures

Consideration is given to results of experimental and theoretical investigations how alpha-epsilon phase transition in the unalloyed iron and the 30 KhGSA steel and its absence in the austenitic 12Kh18N10T stainless steel influence processes under explosive deformation of spheres made of these materials. Polymorphous transition is shown to significantly effect on: amount of explosion-products energy transferred to a sphere, evolution of the converging-wave structure and its parameters, profiles of stress wave and temperature T(R, t) for some Lagrangian particles along the sphere radius, character of energy cumulation under spherical convergence of waves.

Corrosion of austenitic steels and their components in vanadium-containing chloride melts

The corrosion of austenitic 12Kh18N10T, 10Kh17N13M2T, and 03Kh17N14M3 steels and their components (Cr, Fe, Ni, Mo) in NaCl-KCl-VCl2 melts with 5 wt % V at 750°C is studied. The rates and mechanisms of corrosion of the materials under these conditions are determined. The processes that occur during contact of the metals and steels with vanadium-containing chloride electrolytes are investigated.

Numerical 3D-modeling of spall and shear fractures in shells of austenitic 12Kh18N10T steel and 30KhGSA steel under their spherical and quasi-spherical explosive loading

To pursue VNIIEF-VNIITF joint investigations, this paper briefly describes the experimental setup and provides numerical 3D-computation results (LEGAK-3D technique) on special features in the convergence dynamics of steel shells under their quasi-spherical explosive loading in the system with the 40-mm outer radius of the explosive layer.The computation results were compared with the data experimentally registered for shells of the high-purity and technical-purity unalloyed iron, the 30KhGSA steel, both as-received and quenched to HRC 35...40, and the austenitic 12Kh18N10T stainless steel. The comparison was also made with laser-interferometry results obtained directly under explosive loading, as well as with gamma-tomography and scanning electron microscopy investigations of the recovered shells.

Cumulation of a spherically converging shock wave in metals and its dependence on elastic-plastic properties, phase transitions, spall and shear fractures

Consideration is given to results of experimental and theoretical investigations how alpha-epsilon- phase transition in the unalloyed iron and the 30KhGSA steel and its absence in the austenitic 12Kh18N10T stainless steel influence processes under explosive deformation of spheres made of these materials. Polymorphous transition is shown to significantly effect on:- amount of explosion-products energy transferred to a sphere,- evolution of the converging-wave structure and its parameters, profiles of stress wave and temperature T(R,t) for some Lagrangian particles along the sphere radius,- character of energy cumulation under spherical convergence of waves.

Structure and fatigue properties of 08Kh18N10T steel after equal-channel angular pressing and heating

The structure of corrosion-resistant austenitic 08Kh18N10T steel is studied after equal-channel angular pressing (ECAP), heating, and subsequent cyclic tests. After ECAP, an oriented mainly subgrain structure with a structural element size of 100–250 nm and a high fraction of deformation twins forms in the austenite of the steel, and 42 vol % of lath martensite appears. Dynamic twinning, martensitic transformation, dynamic recovery, and even recrystallization take place in the 08Kh18N10T steel during cyclic deformation in the course of fatigue tests according to the scheme of repeated tension. The fatigue strength increases after ECAP due to the refinement and twinning of an austenite structure and the appearance of martensite. The fatigue limit is maximal after ECAP and heating at 550°C for 20 h due to a high annealing twin density in a predominantly austenitic recrystallized matrix, intense dynamic twinning, and martensitic transformation during cyclic deformation.

Phase and structural transformations in corrosion-resistant steels upon high-pressure torsion and heating

High-pressure torsion (HPT) at a pressure of 6 GPa and room temperature is found to form a nanocrystalline structure in corrosion-resistant austenitic 05Kh15N9D2TAMF and 08Kh18N10T steels and a submicrocrystalline structure in corrosion-resistant ferritic 08Kh18T1 steel and armco iron. X-ray diffraction analysis of both austenitic steels reveals the γ → α and γ→ ɛ→ α martensitic transformations during HPT at room temperature. After HPT, the strain hardening in the austenitic and ferritic steels is approximately the same and mainly determined by nano- and submicrocrystalline structures, and the role of alloying and phase composition weakens. The thermal stability of the hardening in the austenitic and ferritic steels is almost the same, ∼400°C. As a result of HPT, the austenitic 08Kh18N10T and ferritic 08Kh18T1 steels acquire an axial texture with the predominant 〈211〉γ direction in austenite and the 〈110〉α and 〈311〉α directions in martensite and ferrite, respectively. The axial texture is retained in both steels up to a heating temperature of 750°C.

Formation of stress field gradients during the high cycle fatigue of an austenitic corrosion-resistant steel

The formation of long-range stress fields in an austenitic 08Kh18N10T steel during high cycle fatigue is studied by transmission electron microscopy, and their gradient character is revealed. This character manifests itself in a decrease in the stress field amplitude as the distance from the source of bending-torsion of the crystal lattice increases.

Formation of a submicrocrystalline structure in austenitic 08Kh18N10T steel during equal-channel angular pressing followed by heating

The structure and mechanical properties of austenitic 08KhN10T steel subjected to equal-channel angular pressing (ECAP) at room temperature (ɛ = 3.2) and subsequent heating are studied. In the course of ECAP, the steel undergoes a martensitic transformation; the martensite content reaches 45%. Upon heating, martensite (ferrite) transforms into austenite. The partly submicrocrystalline oriented structure of the 08Kh18N10T steel in the austenitic (55%)-martensitic (45%) state (formed upon ECAP) provides its high strain hardening (σ0.2 = 1315 N/mm2), as compared to the initial state (σ0.2 = 250 N/mm2), and high plasticity δ = 11%. After heating to 550°C, the steel has a predominantly submicrocrystalline austenitic (80%)-ferritic (20%) structure, σ0.2 = 1090 N/mm2, and δ = 11%.