The effect of hot plastic deformation on the structure and properties of new corrosion-resistant nitrogen-bearing 08Kh17N2AF ferritic–martensitic steel has been investigated. Research data for wedgelike specimens have shown that rolling with a steel reduction up to 70

The influence of preliminary plastic tensile deformation (εpd = 9.5–26

High-temperature X-ray diffraction is used to study the peculiarities of the thermal expansion of VNS9-Sh (23Kh15N5AM3-Sh) TRIP steel; 20Kh15AN3MD2 steel without the TRIP effect (both steels belong to the Fe–Cr–Ni–Mn system), and multiphase heat-resistant coatings with the compositions c-ZrO2 + α-Al2O3 + γ-Al2O3, α-Al2O3 + γ-Al2O3 + t-ZrO2, and Si + SiC. The studies are performed at temperatures up to 1000°C. VNS9-Sh steel with a larger lattice parameter of the α phase as compared to that of 20Kh15AN3MD2 steel (2.890–2.892 and 2.888 Å, respectively) is shown to have a lower linear thermal expansion coefficient (LTEC): (7.6–7.9) × 10–6 and (10.3–10.9) × 10–6 K–1, respectively. It is confirmed that high-temperature X-ray diffraction is an efficient method for estimating the LTEC of multiphase coatings and that the single-crystal LTEC characteristics of phases with tetragonal and hexagonal lattices can be estimated on polycrystalline objects. For phases with tetragonal and hexagonal structures, we are the first to use LTEC representation in the form of a second-rank tensor, which allows us to increase the accuracy of estimating LTEC.

Low-alloy high-nitrogen steels with various nitrogen and chromium concentrations after diffusion saturation of the surface with boron are subjected to metallographic analysis and wear tests. The structure and phase composition of the diffusion layers after boriding and hardening heat treatment are investigated. The structure of the diffusion layers consists of borides FeB and Fe2B and excess phases Cr2(C,N) and (Cr,Fe)B2. The results of wear tests under dry sliding friction conditions demonstrate that, after thermochemical treatment and subsequent heat treatment, the wear rate of the samples decreases by 2 times, and the coefficient of friction is more stable for samples after boriding with 5 wt

X-ray diffraction is used to determine the influence of the reduction during cold rolling of wedge steel 20Kh15AN3MD2 samples on the quantitative phase composition, the texture, and the residual macrostresses in the α and γ phases. When the reduction increases, the fraction of the γ phase decreases from 82

X-ray diffraction methods were used to study the influence of the degree of deformation during tensile testing on the phase composition, texture and stress state of the α- and ɣ-phases of the VNS9-SH alloy. It is shown that during testing to failure, the amount of the α-phase increases on the surface from 75 to 91% and from 45-50 to ~70% in the subsurface layers. To assess the susceptibility of two-phase steels to the trip effect, a parameter of austenite metastability is proposed in the form of the relative fraction of decomposed austenite at individual stages of tensile deformation. It has been established that in the initial steel strip 0.3 mm thick, as a result of the positive volumetric effect of the transformation ɣ = α, compressive stresses are formed in austenite, reaching a value of –1000 MPa on the surface, in contrast to tensile stresses in martensite. Their presence is associated with heating of the metal, the cooling of which leads to tensile stresses in martensite due to its significantly lower temperature coefficient of linear expansion value compared to austenite.

Рентгеновским методом определяли влияние величины обжатия при холодной прокатке клиновых образцов стали 20Х15АН3МД2 на количественный фазовый состав, текстуру и остаточные макронапряжения a- и g-фаз. С увеличением обжатия доля g-фазы уменьшается от 82% в исходном горячекатаном состоянии до 74% при обжатии 10% и до 60% при увеличении обжатия до 70%. Тип текстуры аустенита характеризуется компонентами, типичными для текстуры прокатки ГЦК металлов - это текстура «латуни» ({110} ), которая не меняется при обжатии 10%, а затем существенно увеличивается при обжатии 20% и остается на том же уровне вплоть до обжатия 70%. Текстура a-фазы характеризуется тремя компонентами: {110} , {211} и {001} , первые два - это текстуры превращения, которые доминируют в исходном состоянии, а после обжатия 30% усиливается третий компонент, соответствующий текстуре прокатки ОЦК a-фазы. Оценка остаточных напряжений показала, что в g-фазе формируются сжимающие напряжения величиной 600-1100 МПа, а в a-фазе - растягивающие напряжения величиной 1200-1600 МПа.

Abstract—The phase composition of a VNS9-Sh TRIP steel strip 0.8 mm thick is determined using layer-by-layer X-ray diffraction (XRD) analysis using Mo, Co, or Cu radiation. The influence of the type of radiation on the efficiency of quantitative phase analysis of thin-sheet TRIP steels is examined using the obtained results. The parameter “information depth” is accepted as an efficiency characteristic. The information depth is the layer thickness the scattering intensity from which amounts 90

The structure and mechanical properties of martensitic–ferritic nitrogen-bearing 08Kh17N2AF steel after quenching in the temperature range 800–1200°C are studied. This steel after quenching from 950°C is found to have a high strength (σu = 1290 MPa, σ0.2 = 850 MPa) and impact toughness at +20°C (KCU = 0.8 MJ/m2) but a low impact toughness at –70°C (KCU = 0.3 MJ/m2) as a result of the formation of a martensitic–ferritic–austenitic structure containing ∼82

Abstract—The structure and mechanical properties of rods of low-alloy martensitic steels with an overequilibrium nitrogen content, which are melted in a vacuum induction furnace with subsequent electroslag remelting under nitrogen pressure and are manufactured by free forging, are studied. The distribution of alloying elements and the hardness along the rod length is found to be uniform. The α → γ transformation temperature on hearting, Ac1 = 662°C and Ac3 = 838°C, of the steels are determined by differential scanning calorimetry. The structure of these steels contains a small amount of disperse particles of manganese sulfides and vanadium nitrides. Quenching and low tempering of the steels are shown to lead to a good combination of a high strength (σu = 2150–2170 MPa, σ0.2 = 1450–1480 MPa), ductility (δ = 12–14

The data on the effect of carbon and nitrogen on the stacking fault energy (SFE) of austenitic steels are summarized. Threshold values of SFE characterizing the stability of austenite are given. The effective value of SFE for high-nitrogen austenitic steels is found to be 20–25 mJ/m2. At this value, these steels have the best combination of strength, ductility, and impact strength at a retained high stability of austenite to the γ–ε–α transformation during cooling and plastic deformation.

The structure of specimens at different stages of thin strip fabrication (from ingot to cold-rolled strip) is investigated. Alloy 97NL-VI strip specimen properties are studied, including determination of the level of strength properties, and specific electrical resistance. Strip microstructure is studied by X-ray structural analysis after various heat treatment versions. The effect of various heat treatment regimes on the level of physicomechanical properties is studied.

The effect of annealing on the phase composition, the lattice parameters, and the linear thermal expansion coefficient (LTEC) of the α and γ phases in VNS9-Sh TRIP steel is studied by high-temperature X-ray diffraction. Annealing at 450°C does not lead to a change in the single-phase martensitic structure of the cold-rolled TRIP steel, but annealing at 600°C is accompanied by partial decomposition of the α phase with the precipitation of 46

The crack growth characteristics are investigated in situ in a scanning electron microscope column during the tension of nonmagnetic 04Kh18AG20 steel specimens with a overequilibrium nitrogen content (0.98 wt % N) and various vanadium contents. The character of crack nucleation and propagation in steel after quenching from 1200°С and after subsequent aging at 650°С for 5 h is shown to be the same. The critical shear crack size at the maximum load is 300 μm in vanadium-free 04Kh18AG20 steel and 120 μm in vanadium-bearing 04Kh18AG20F steel. Corrosion-resistant nickel and vanadium-free austenitic 04Kh18AG20 steel (0.98 wt % N) after quenching from 1200°C is recommended for heavy-duty nonmagnetic structures.

The results of the structure and stacking fault energy (SFE) investigations of low-carbon austenitic steels alloyed with substitutional elements are summarized. An increase in the manganese content in the range 7–20 wt % in Fe–Mn alloys is shown to make austenite stable to the γ–α transformation and unstable to the γ–ε transformation. Ferromanganese steel containing 20 wt % Mn has the maximum number (50–55%) of stacking faults after deformation. The SFE of Fe–Mn alloys is inversely proportional to the manganese content at Mn < 14 wt % and directly proportional at higher manganese concentrations. A temperature dependence of the SFE on the manganese content is found for Fe–Mn alloys. The effect of chromium on the SFE depends on the manganese content. A linear dependence of the SFE on the nickel content in Cr–Ni steels with 10–25 wt % Cr is found in the concentration range 10–25 wt %.

The сrack growth characteristics are investigated in situ in a scanning electron microscope column during the tension of the welded joints of two-phase (γ + δ) and single-phase (γ) 05Kh22AG16N8M steel containing 0.36 and 0.52 wt % N, respectively. A crack in the steel with 0.36% N and its welded joint is shown to form and develop at a low load and strain due to the existence of the σ phase in the steel structure and δ ferrite in the welded joint.

The works on the structure and mechanical properties of aluminum-alloyed austenitic steels are analyzed. Aluminum in aging high-nitrogen Cr–Mn–Ni–V nonmagnetic steels is shown to decrease the strength due to a decrease in the amount of dispersed VN nitrides having precipitated during aging because of the formation of coarse AlN particles hard to dissolve on quenching heating. An additional increase in the strength of aging nonmagnetic Mn–Ni–V–C steels is reached by their alloying with aluminum, which does not form hard to dissolve compounds with carbon. A significant increase in the surface hardness and the wear resistance during nitriding is reached as a result of separate or complex alloying of Mn–Ni–V steels with chromium up to 3% and aluminum up to 1.2%, which increase the nitrided layer thickness. The best combination of the properties of the nitrided layer is achieved after nitriding these steels containing 2.5–3.5% V at 700°C (12 h) in a 80% N 2 + 20% HN 3 medium. In this case, the hardening of the core during aging is related to the precipitation of VC carbides, and that of the nitrided layer, to the formation of VN nitrides. A significant increase in the volume fraction of strengthening phases in manganese steels is reached by complex alloying with Al, Ni, Cu, and V in the amounts that provide the simultaneous precipitation of the VC carbide and NiAl intermetallics during aging. Nonmagnetic 50G17N10Yu4F2 steel with a combined carbide–intermetallic hardening is highly competitive in strength (σ u > 1600 MPa, σ 0.2 > 1400 MPa) with high-strength 18Kh2N4VA ferromagnetic steels and significantly surpasses the well-known aging nonmagnetic high-nitrogen alloys.

The structure and the mechanical properties of low-carbon low-alloy 10Kh3A steel with an overequilibrium nitrogen content (0.20 wt %) are studied after heat treatment under various conditions. The quenching (950°C) and tempering (400°C) temperatures that result in significant hardening of the steel (σu = 1680 MPa, σ0.2 = 1550 MPa) at the retained plasticity (δ = 11%, ψ = 44%) that is high enough for practical application are determined. The strength of the 10Kh3A steel is higher than that of low-alloy nitrogen-free low-carbon 18Kh2N4VA steel, which is alloyed with nickel and tungsten and is widely used for heavily loaded structural members.

The structure and the mechanical properties of the high-strength structural martensitic steels used in manufacturing the mechanism parts subjected to significant cyclic dynamical loads are considered. All the steels have a similar martensitic–bainite structure and a high stability of their mechanical properties. At the same time, their structures are found to contain secondary phases, which can degrade their functional properties. 03Kh11N10M2T maraging steel exhibits fairly high impact toughness for this class of steels despite a brittle character of fracture during bending impact tests.