Structural-phase State Research Articles

Formation of structural-phase state of Ti–Al materials with Hf-additives obtained by hydride technology

The paper describes the structural and phase composition of TiHf50, AlHf50, TiAl49Hf2 composite materials obtained by the “hydride” technology. A three-component phase diagram for Ti-Al-Hf at 1150°C is constructed. The structural state of TiAl49Hf2 alloys was predicted based on reference lattices found in the USPEX code with the VASP interface; quantum-chemical calculations of the TiAl49Hf2 energy were additionally performed in the CASTEP code. It is shown that solid solutions dominate in the TiAl49Hf2 alloy sample, in which the main elements dominate: Al10 – Ti9Al23 – Ti8. Hf atoms can be introduced into the interstitial sites [-0.257 0.042 0.2545] (St-Hf-27), [0.0053 -0.0120 -0.0765] (St-Hf-143), [0.5 0.5 0.5] (St-Hf). The introduction of hafnium into the specified lattice sites does not violate the stabilizing effect in the TiAl49Hf2 systems. It is shown that the maximum microhardness value (4.9 GPa) was obtained when testing the TiHf50 sample (for comparison: for the TiAl50 system – 1.2 GPa, for the TiAl49Hf2 system – 2.2 GPa).

Formation of structural-phase state of Ti–Al materials with Zr-additives obtained by hydride technology

The structural and phase composition of TiZr50, AlZr50, TiAl49Zr2 composite materials obtained by the hydride technology was investigated. A model three-component phase diagram was constructed for Ti–Al–Zr at a temperature of 1150°C. The structural state of TiAl49Zr2 alloys was predicted based on reference lattices (USPEX code with VASP interface), quantum-chemical calculations of the energy of TiAl49Zr2 were carried out in the CASTEP code. Solid solutions dominate in TiAl49Zr2, in the composition of which the main elements are predominant: Al10–Ti9Al23–Ti8. Zr atoms can be introduced into the interstitial sites [– 0.257 0.042 0.2545] (St–Zr–27), [0.0053–0.0120–0.0765] (St–Zr–143), [–0.3251–0.3983 0.4880] (St–Zr– 75). The introduction of Zr into the specified lattice sites does not violate the stabilizing effect in the TiAl49Zr2 systems. All reference lattices are stable. In the TiAl49Zr2 alloy, the main phases are Al10Ti9Zr, Al23Ti8Zr, the contributions of which to the theoretical intensity are 78.57 and 21.43%. In the AlZr50 sample, the phases ZrAl, Zr2Al3, ZrAl2.

Study of structural and mechanical properties of composite ceramics of the AlMgB14–TiB2 system

AlMgB14 ceramics is known as a material characterized by increased hardness in combination with a low friction coefficient. Composite structures based on this ceramics have even higher strength characteristics. In the present work, we investigate the structural-phase states and physicomechanical properties of composite ceramics of the AlMgB14–TiB2 system with a variable TiB2 content, obtained by hot pressing the initial batch based on AlMgB14 and TiB2 ceramic powders preliminarily synthesized by the method of self-propagating high-temperature synthesis. It was found that the resulting materials are characterized by a composite structure represented by TiB2 inclusions distributed in the AlMgB14 matrix. The phase composition of the resulting composites is similar to the phase composition of the initial batch, with 5 to 9 wt. % of the MgAl2O4 spinel phase being formed. The microhardness of AlMgB14–TiB2 composites is up to 19.9 GPa (the hardness of AlMgB14 ceramics obtained by a similar method without additives is 7 GPa). The three-point bending strength of AlMgB14–TiB2 composite materials is 309 MPa.

Mechanisms of hardening of heavy-loaded rails made of hypereutectoid steel during long-term operation

Using transmission electron microscopy methods, the structural-phase states and defective substructure were studied at distances of 0; 2 and 10 mm from the surface along the central axis and rounding radius of rails head fillet. Differentially hardened long rails of the DT400IK category made of hypereutectoid steel have been studied after operation on the Trans-Baikal Railway (passed tonnage equal to 234.7 million tons gross). It has been established that steel strength characteristics are determined by certain physical mechanisms. A qualitative assessment of the contributions from crystal lattice friction, solidsolution strengthening, strengthening of the pearlite component, incoherent cementite particles, grain boundaries and subboundaries, dislocation substructure and internal stress fields was carried out, and their hierarchy was established. A quantitative assessment of the additive yield strength of steel in different directions was carried out depending on the distance from the rolling surface. It is shown that the main mechanisms of strengthening are strengthening by incoherent particles, long-range stress fields and substructural strengthening. The additive yield strength on the fillet surface is significantly greater than on the rolling surface of the head along the central axis.

Technological solutions for applying special coatings to increase wear resistance of machine parts and components

Subject of research: technology for applying alloyed diamond-like coating (DLC), the influence of the atmosphere of the working area on the results of work. Purpose of research: search for the optimal alloyed diamond-like coating for loaded parts of a car transmission in order to ensure the required service life of the unit. Methods of research: all coatings, the research results of which are described in this article, were obtained by reactive magnetron sputtering. Main results of research: an analysis of the structural-phase state of a number of coatings is provided: containing chromium, titanium and silicon, obtained by magnetron sputtering in argon-acetylene-nitrogen atmospheres. Data are presented on the phase composition and size of coherent scattering regions, as well as the relationship between the structure and mechanical properties of the APP. A basic scheme for tribological testing of coatings has been determined, and the obtained nanocomposite structures of the APP are analyzed.

Formation of Structural-Phase State and Elastic and Durometric Properties of Biocompatible Cold-Rolled Titanium Ti–Nb–Zr-Based Alloys during Aging

The methods of scanning electron microscopy, X-ray diffraction analysis, and microindentation are used to study the effect of alloying with zirconium (within 3 to 6 at %) and complex Zr + Sn and Zr + Sn + Ta additions on the evolution of the structure, phase composition, and properties (effective modulus of elasticity, hardness, and wear-resistance parameters) of quenched biocompatible β-titanium (at %) Ti–6% Nb–% Zr, Ti–6% Nb–% Zr, Ti–6% Nb–% Zr, Ti–6% Nb–% Zr–% Sn, and Ti–6% Nb–% Zr–% Sn–0.7Ta alloys during aging (at 400°C for 4, 16, and 64 h) after multipass cold rolling with a total degree of strain of 85%. As compared to the quenching, the cold rolling of the studied Ti–b–r alloys is shown to suppress the occurrence of the β → ω transformation in the course of aging and to favor the acceleration of the decomposition of β solid solution with the formation of nonequilibrium αl phase in the course of aging. The increase in the zirconium content from 3 to 6 at % in the cold-rolled ternary Ti–6% Nb –х% Zr alloys and introduction of complex Zr + Sn and Zr + Sn + Ta additions to the Ti–6% Nb alloy instead of only zirconium addition hinder the decomposition processes of the β phase during aging; this impacts the intensity of variations of the effective modulus of elasticity and microhardness. The aging of the cold-rolled alloys under study was found to allows us to obtain the higher values of the parameters H/Er and (Н is the hardness and Er is the resolved modulus of elasticity) associated with the wear resistance as compared to those for the widely used medical Ti–Al–V alloy. The compositions of the alloys and conditions of their treatment are determined, which allow us to obtain the combination of the highest-level properties.

Structure and Mechanical Properties of Microwave-Absorbing Co-C Coatings Obtained by Magnetron Sputtering

This article is devoted to the study of microwave-absorbing properties of Co-C coating applied by magnetron sputtering. This article presents the main results of the manufacturing of a Co-C coating by magnetron sputtering, and the evaluation of experimental and computational research data on the relationship between the structure and properties of the obtained films. The structure of Co-C systems has been modeled to control the resulting structures using X-ray diffraction analysis. The structural-phase state of the resulting thin-film Co-C systems and the microwave-absorbing properties of coatings were studied using the transmission line method, consisting of a vector network analyzer, an air coaxial line, a software program, and an external computer. It has been established that on the resulting Co-C film the reflection coefficient in the frequency range of 8.2–12.4 GHz varies in the range of 900 → 718 mU, with reflection losses of −0.86 → −2.57 dB, and a standing wave coefficient of 19 → 6.8. An analysis of the obtained data indicates the presence of losses of electromagnetic energy in the studied frequency range.

Post-Processing of Inconel 718 Alloy Fabricated by Additive Manufacturing: Selective Laser Melting

The review analyses Inconel 718 (IN718) alloy, which is the nickel-based superalloy and has great application in industries due to its superior mechanical properties even at elevated temperatures by means of the solid-solution strengthening and precipitation strengthening. However, because of the tool over-wear, poor part surface integrity, high hardness and low thermal-conductivity properties, it is difficult to manufacture finished products with using conventional machining methods. It is especially urgent for the products of complex designs. In this regard, justification is given for the widespread use of modern additive manufacturing (AM) for the fabrication of the products from IN718. The most popular is AM based on the selective laser melting (SLM) technique, which can fabricate complex geometries with superior material properties. At the same time, the metal parts fabricated by SLM suffer from excessive residual porosity, residual tensile stress in the near-surface layer, and the formation of a relatively rough surface. In addition, the SLM-inherited surface defects can cause stress concentration to initiate cracks, reducing the fatigue strength of the printed parts. The review focuses on identifying potential solutions to the surface-finish complex additive manufactured to improve the surface properties to meet the industry requirements. Therefore, the improvement of the IN718-alloy-parts’ surface properties printed by the SLM becomes especially relevant. Currently, different surface post-processing technologies are being developed to obtain the expected surface quality of the SLM-components. As demonstrated, the finish surface enhancement treatments led to significant improvement in the wear resistance, corrosion resistance, increase in fatigue life, and tensile strength of the metallic materials. Therefore, adapting surface post-processing technologies has become a growing area of interest as an effective tool for improving the functionality and service lifetime of SLM IN718-alloy components. The review aims to analyse the main results of the most systematic studies of the currently developed surface post-treatments aimed to improving the surface-structure quality and properties of the IN718 parts fabricated by SLM. These results contribute to a better understanding of the role of the various-parameters’ effects on the surface improvements during the surface post-processing and changes in the structure–phase state, and physical, chemical and mechanical properties. Examples of the effects of a series of surface post-processing methods are presented: laser polishing, mechanical magnetic polishing, cutting finish-machining operations, shot peening, sandblasting technique, ultrasonic-impact treatment, and electrochemical polishing.

Pt nanoclusters as co-catalysts for efficient photocatalytic hydrogen evolution

Photocatalytic water splitting for hydrogen production is an ideal strategy to relieve the energy crisis. In this work, Pt nanoclusters are employed as a co-catalyst to modify g-C3N4 for optimizing the photocatalytic hydrogen evolution performance. Compared with the pristine g-C3N4, the Pt nanoclusterss/g-C3N4 nanocomposites exhibit dramatic enhancement toward H2 production, where the H2 evolution rate of CN-Pt-C2 is nearly 425.1 times higher than pristine g-C3N4. The phase structure, morphology, optical properties, and surface chemical states of the fabricated samples are fully investigated. Based on the systematical characterizations, the reason for the enhanced H2 generation performance is disclosed. It is expected this work can provide a valuable reference for the fabrication of a co-catalyst-based photocatalytic system.

Research on microstructure, mechanical property and wear mechanism of AlCoCrFeNi/WC composite coating fabricated by HVOF

In this study, HVOF spraying technology was utilized to prepare AlCoCrFeNi/WC composite coatings with varying WC content on 40CrMnMoA steel substrate. The microstructure, elemental distribution, phase structure and chemical valence states of wear scratches of the composite coatings were analyzed using the SEM, EDS, XRD and XPS. Microhardness was measured using single-point digital microhardness tester, while nanohardness and elastic modulus were determined using a nano-indenter. The bonding strength of the composite coatings was evaluated using a tensile tester. Friction and wear tests were conducted to assess the wear behavior of the composite coatings. The results indicated that the microstructure, microhardness, nanohardness and elastic modulus of AlCoCrFeNi HEA coating increased with the addition of WC, attributed to the hard phase effects of WC. However, the bonding strength first decreased and then increased. Compared to the W 0 coating, the wear rates of the other composite coatings decreased by 30.5 %, 46.1 %, 65.3 %, and 82.1 %, respectively, which demonstrating that the effect strengthening of WC. After the friction and wear tests, the wear mechanism of the W 0 and W 1 coatings represents adhesive wear, abrasive wear and severe oxidation wear. In contrast, the W 2 and W 3 coatings exhibited slight adhesive wear, slight abrasive wear and slight oxidation wear, while the W 4 coating showed the slightest abrasive wear, the slightest adhesive wear and the slightest oxidation wear.

Structural-phase state and properties of heat and wear resistant cast irons of Cr–Mn–Ni–Ti system additionally alloyed with Al and Nb

The paper presents the data on phase composition and structure forming for the alloys, on distribution of elements among the alloy structural components, on variation of wear resistance, scale resistance, growing stability and mechanical properties of cast iron of Cr–Mn–Ni–Ti–Al–Nb system depending on different aluminium and niobium content and thermal ac-cumulating capacity of a casting mould. Complex carbides (Nb, Ti)C are forming in white cast iron during niobium alloying. Quantitative metallographic analysis of (Nb, Ti)C carbides and (Cr, Fe, Mn)7C3 complex carbides was carried out on the samples with examined composition. Aluminium provides favourable influence on forming of the thin protective spinel-type films with minimal amount of defects; diffusion through such oxide film is very difficult. Joint alloying by aluminium and niobium leads to simultaneous increase of heat resistance and wear resistance. Wear resistance increased as a result of enlargement of the part of primary carbides (Nb, Ti)C with high hardness in the structure of cast iron. Composition of oxide films includes aluminium, which strengthens their protective properties and rises of the alloy scale resistance. It is found for the first time that niobium doping leads to secondary solidification during cooling in the casting mold. Dispersion particles of М7С3 carbides are forming in solid state, thereby no structure degradation occurs during testing at increased temperatures, and growing stability rises. On the basis of the complex of the conducted researches the rational composition of heat and wear resistant cast iron is offered at the following ratio of components, wt. %: 2.1–2.2 C; 4.5–5.0 Mn; 18.0–19.0 Cr; 1.0–1.2 Ni; 0.4–0.6 Ti, 2.0 Nb; 2.0 Al. Wear resistance increased 1.2 times compared to cast irons before the introduction of aluminum and niobium, and scale resistance – 2.4–4.5 times depending on the type of casting mold, the index of growth resistance is equal to zero for cast irons cast in dry SLM

Role of Quenching Temperature Selection in the Improvement of the Abrasive (Al2O3) Wear Resistance of Hybrid Multi-Component Cast Irons.

In this paper, enhancing the tribological characteristics of novel cast metallic materials-hybrid multi-component cast irons-by applying a strengthening heat treatment is described. The experimental materials were the cast alloys of a nominal composition (5 wt.% W, 5 wt.% Mo, 5 wt.% V, 10 wt.% Cr, 2.5 wt.% Ti, Fe is a balance) supplemented with 0.3-1.1 wt.% C and 1.5-2.5 wt.% B (total of nine alloys). The heat treatment was oil-quenching followed by 200 °C tempering. The quench temperature (QT) varied in the range of 900-1200 °C, with a step of 50 °C (with a 2-h holding at QT). The correlation of the QT with microstructure and properties was estimated using microstructure/worn surface characterization, differential scanning calorimetry, hardness measurement, and three-body-abrasive wear testing (using Al2O3 particles). The as-cast alloys had a multi-phase structure consisting of primary and/or eutectic borocarbide M2(B,C)5, carboborides M(C,B), M7(C,B)3, M3(C,B), and the matrix (ferrite, martensite, pearlite/bainite) in different combinations and volume fractions. Generally, the increase in the quenching temperature resulted in a gradual increase in hardness (maximally to 66-67 HRC) and a decrease in the wear rate in most alloys. This was due to the change in the phase-structure state of the alloys under quenching, namely, the secondary carboboride precipitation, and replacing ferrite and pearlite/bainite with martensite. The wear rate was found to be inversely proportional to bulk hardness. The maximum wear resistance was attributed to QT = 1150-1200 °C, when the wear rate of the alloys was lowered by three to six times as compared to the as-cast state. With the QT increase, the difference in the wear rate of the alloys decreased by three times. The highest abrasive resistance was attributed to the alloys with 1.1 wt.% C, which had a 2.36-3.20 times lower wear rate as compared with that of the reference alloy (13 wt.% Cr cast iron, hardness of 66 HRC). The effects of carbon and boron on hardness and wear behavior are analyzed using the regression models developed according to the factorial design procedure. The wear mechanisms are discussed based on worn surface characterization.

Structural-Phase State Of Austenitic 20GL Steel After Thermal Treatment by Normalizing and High-Temperature Tempering

Structural-Phase State Of Austenitic 20GL Steel After Thermal Treatment by Normalizing and High-Temperature Tempering

Increasing Exploitation Durability of Two-Layer Cast Mill Rolls and Assessment of the Applicability of the XGBoost Machine Learning Method to Manage Their Quality.

The increase in exploitation durability of two-layer cast rolls with the working layer made of high chromium cast iron allows one to significantly improve the quality of rolled metal as well as to increase the economic efficiency of the manufacturing process. However, it is severely hindered due to the massiveness of castings, the impossibility of both evaluating mechanical properties along the depth of the working layer, and providing the structural uniformity of the working surface and the decrease in stresses. In our research, aiming to enhance the exploitation durability of sheet rolls, it is recommended to achieve structural uniformity by CuMg alloying, which increases the concentration of copper up to 2.78 wt.% in certain zones and, owing to the accelerated austenite decomposition at a high temperature during the cool-down of the castings, led to the reduction in excessive strength and the level of heat stresses in the castings. We propose the regimes of cyclic heat treatments which, due to the decomposition of retained austenite and the fragmentation of structure, control the level of hardness to reduce and uniformize the level of stresses along the length of a barrel. A further improvement in the predictions of exploitation durability using XGboost method, which was performed based on the chemical composition of the working layer of high-chromium cast iron and heat treatment parameters, requires taking into account the factors characterizing exploitation conditions of specific rolling mills and the transformations of structural-phase state of the surface obtained by a non-destructive control method. As the controlled parameter, the hardness measured on the roll's surface is recommended, while the gradient change in mechanical properties along the working layer depth can be feasibly analyzed by a magnetic method of coercive force measuring.

Comparative analysis of the structural-phase state and operational properties of zinc coatings obtained by various methods

Comparative analysis of the structural-phase state and operational properties of zinc coatings obtained by various methods

IMPLEMENTATION OF MAGNETRON SPUTTERING METHOD IN OBTAINING A RADIO-ABSORBING THIN FILM BASED ON CoC

This paper describes the main results of the study of obtaining samples of radio-absorbing CoC films by magnetron sputtering and evaluates the data of experimental and computational studies on the relationship between the structure and properties of CoC films. To eliminate the ferromagnetic effect of cobalt, a composite target was used. The use of the composite target during magnetron sputtering ensures the production of films of a given and necessary composition. Structural-phase state of the obtained films was studied using XRD, SEM and TEM methods. A distinctive feature of the synthesized coating is the absence of a crystalline structure in some areas due to the amorphizing properties of cobalt and its tendency to form metallic glasses. Results obtained by the experiments are in good agreement with computational modeling results. The radio-absorbing properties of the obtained films were confirmed by the results of measuring the reflection loss, standing wave ratio, reflectance, and impedance. Results presented in the article can serve as a baseline for perspective studies in this field.

Investigation of the structural and phase state of detonation multilayer coatings based on NiCr/NiCr–Al2O3/Al2O3 during high-temperature oxidation

This paper presents a study of the structural and phase state of detonation multilayer coatings under hightemperature oxidation. The experiment aimed to find out the effect of high temperatures on the structuralphase state of coatings and their effectiveness in preventing oxidative processes. As a result of the research, it was found that after high-temperature tests, protective phases such as NiCr2O4, Al2O3, and Cr2O3 are formed in the structure of multilayer coatings. These phases were identified to play a key role in preventing intensive oxidation of the metal surface. It was determined that NiCr2O4 provides stability to the metal layer, and Al2O3 and Cr2O3 are effective barriers protecting the surface from aggressive environmental influences. It is important to note that no signs of fracture or detachment were found in the multilayer coatings during the entire experiment. After the first cycle, the uncoated sample experienced peeling of its oxide film, resulting in a significant loss of mass. It was determined that the uncoated steel experiences significantly higher mass loss, indicating a faster formation of oxides on its surface. The experimental data confirm the effectiveness of coatings in protecting against oxidative processes at high temperatures, thereby maintaining the stability and durability of the material under extreme thermal influences.

Influence of Deformation on the Structural–Phase State of Structural Steel and on the Formation of Its Yield Strength and Degree of Hardening

Influence of Deformation on the Structural–Phase State of Structural Steel and on the Formation of Its Yield Strength and Degree of Hardening

Effect of Structural-Phase State on the Deformation Behavior and Mechanical Properties of Near β Titanium Alloy VT22 in the Temperature Range 293–823 K

Effect of Structural-Phase State on the Deformation Behavior and Mechanical Properties of Near β Titanium Alloy VT22 in the Temperature Range 293–823 K

Effect of the Melt Cooling Rate on the Structural-Phase State of the Al–Si Alloy Doped with Metals

Effect of the Melt Cooling Rate on the Structural-Phase State of the Al–Si Alloy Doped with Metals