Subjects -> METALLURGY (Total: 58 journals)
Showing 1 - 10 of 10 Journals sorted alphabetically
Acta Metallurgica Slovaca     Open Access   (Followers: 2)
Advanced Device Materials     Open Access   (Followers: 6)
American Journal of Fluid Dynamics     Open Access   (Followers: 44)
Archives of Metallurgy and Materials     Open Access   (Followers: 9)
Asian Journal of Materials Science     Open Access   (Followers: 4)
Canadian Metallurgical Quarterly     Hybrid Journal   (Followers: 21)
Complex Metals     Open Access   (Followers: 2)
Energy Materials : Materials Science and Engineering for Energy Systems     Hybrid Journal   (Followers: 24)
Graphene and 2D Materials     Open Access   (Followers: 6)
Handbook of Ferromagnetic Materials     Full-text available via subscription   (Followers: 1)
Handbook of Magnetic Materials     Full-text available via subscription   (Followers: 2)
High Temperature Materials and Processes     Open Access   (Followers: 6)
Indian Journal of Engineering and Materials Sciences (IJEMS)     Open Access   (Followers: 11)
International Journal of Metallurgy and Alloys     Full-text available via subscription   (Followers: 1)
International Journal of Metals     Open Access   (Followers: 7)
International Journal of Minerals, Metallurgy, and Materials     Hybrid Journal   (Followers: 11)
International Journal of Mining and Geo-Engineering     Open Access   (Followers: 4)
Ironmaking & Steelmaking     Hybrid Journal   (Followers: 5)
ISIJ International - Iron and Steel Institute of Japan     Full-text available via subscription   (Followers: 26)
Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional’nye Pokrytiya (Proceedings of Higher Schools. Powder Metallurgy аnd Functional Coatings)     Full-text available via subscription   (Followers: 2)
JOM Journal of the Minerals, Metals and Materials Society     Hybrid Journal   (Followers: 35)
Journal of Central South University     Hybrid Journal   (Followers: 1)
Journal of Cluster Science     Hybrid Journal  
Journal of Heavy Metal Toxicity and Diseases     Open Access  
Journal of Iron and Steel Research International     Hybrid Journal   (Followers: 11)
Journal of Materials & Metallurgical Engineering     Full-text available via subscription   (Followers: 2)
Journal of Materials Processing Technology     Hybrid Journal   (Followers: 21)
Journal of Metallurgical Engineering     Open Access   (Followers: 4)
Journal of Sustainable Metallurgy     Hybrid Journal   (Followers: 3)
Materials Science and Metallurgy Engineering     Open Access   (Followers: 6)
Metal Finishing     Full-text available via subscription   (Followers: 20)
Metallurgical and Materials Engineering     Open Access   (Followers: 7)
Metallurgical and Materials Transactions A     Hybrid Journal   (Followers: 41)
Metallurgical and Materials Transactions B     Hybrid Journal   (Followers: 32)
Metallurgical and Materials Transactions E     Full-text available via subscription   (Followers: 2)
Metallurgical Research and Technology     Full-text available via subscription   (Followers: 8)
Metallurgy and Foundry Engineering     Open Access   (Followers: 2)
Mining, Metallurgy & Exploration     Hybrid Journal  
Powder Diffraction     Full-text available via subscription   (Followers: 1)
Powder Metallurgy     Hybrid Journal   (Followers: 36)
Powder Metallurgy and Metal Ceramics     Hybrid Journal   (Followers: 8)
Powder Metallurgy Progress     Open Access   (Followers: 5)
Practical Metallography     Full-text available via subscription   (Followers: 6)
Rare Metals     Hybrid Journal   (Followers: 3)
Revista de Metalurgia     Open Access  
Revista del Instituto de Investigación de la Facultad de Ingeniería Geológica, Minera, Metalurgica y Geográfica     Open Access  
Revista Remetallica     Open Access   (Followers: 1)
Revue de Métallurgie     Full-text available via subscription  
Russian Metallurgy (Metally)     Full-text available via subscription   (Followers: 4)
Science and Technology of Welding and Joining     Hybrid Journal   (Followers: 7)
Steel Times lnternational     Partially Free   (Followers: 19)
Transactions of the IMF     Hybrid Journal   (Followers: 14)
Transactions of the Indian Institute of Metals     Hybrid Journal   (Followers: 5)
Tungsten     Hybrid Journal  
Universal Journal of Materials Science     Open Access   (Followers: 3)
Welding in the World     Hybrid Journal   (Followers: 7)
Welding International     Hybrid Journal   (Followers: 11)
Вісник Приазовського Державного Технічного Університету. Серія: Технічні науки     Open Access  
Similar Journals
Journal Cover
Powder Metallurgy and Metal Ceramics
Journal Prestige (SJR): 0.221
Number of Followers: 8  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1573-9066 - ISSN (Online) 1068-1302
Published by Springer-Verlag Homepage  [2626 journals]
  • Microstructure and Wear Behaviour of 17-4 Precipitation Hardening
           Stainless Steel with Various Ti Content
    • Abstract: In this study, the wear behaviour of aged 17-4 PH SS (precipitation hardening stainless steel) that contains 0.5, 1, 1.5, and 2% of Ti was examined. The mixed elemental powders (in wt.%: 17 Cr, 4 Cu, 4 Ni, 1 Mn, 1 Si, 0.3 Nb, 0.07 C, and Fe remaining) were cold-pressed (800 MPa), and the pre-formed 17-4 PH SS green compacts were sintered at 1300°C for 60 min in a 0.1 Pa vacuum and at 4 °C/min heating rate and cooled down in furnace to room temperature. Alloys with different amounts of titanium were aged at 480°C for 1, 4, and 8 h. Scanning electron microscopy, X-ray diffraction analysis, and density and hardness measurements were employed to characterize the aged alloys. The pin-on-disc apparatus was used for wear testing. The wear testing was performed under the sliding speed of 0.8 m/sec, two various loads (of 30 and 45 N), and at five different sliding distances of 600, 1200, 1800, 2400, and 3000 m. Research results showed that in 17-4 PH SS, the weight loss and density decreases with a higher titanium content, while their hardness increase. Thus, a higher amount of Ti addition contributes to lower weight losses. The friction coefficient shows the highest value in the samples containing 0.5% Ti and the lowest in the alloy containing 2% Ti. M23C6 and M3C carbides are formed in the microstructure of the material, as expected. From the SEM images of worn surfaces, the adhesive and oxidative wear mechanisms were determined as dominant. Due to the choice of composition with the highest hardness and corresponding sintering conditions, the wear resistance of alloys can be increased significantly.
      PubDate: 2020-11-29
       
  • Electrochemical Corrosion of Composite Ceramics and Thermal Spray Coatings
           in the ZrB 2 –SiC–AlN System
    • Abstract: Polarization studies of the ZrB2–SiC–AlN compact ceramic material and thermal spray coatings of the same composition were conducted in a 3% NaCl solid solution to analyze their cathodic and anodic behavior. The compact ceramic material was produced by hot pressing, the plasma-sprayed coating 240 μm thick was deposited onto a C/C–SiC graphite substrate, and the detonation-sprayed coating 340 μm thick was applied to 12Kh18N9T stainless steel. The microstructure and phase composition of the compact sample and thermal spray coatings were examined. The microstructure was heterophase in all cases. The compact sample and plasma-sprayed coating contained SiC, AlN, and ZrB2 as the main phases, and the detonation-sprayed coating additionally had a small amount of nickel and zirconium oxide. Electron microprobe analysis showed that the plasma-sprayed coating had 20 wt.% oxygen; i.e., the coating contained oxide phases in the amount not revealed by X-rays. The compact ceramic sample showed exceptionally high resistance to electrochemical oxidation: electrochemical potential, Ecorr, at which corrosion current occurs is very high and constitutes +1.51 eV. For the detonation- and plasma-sprayed coatings, Ecorr = –0.25 and –0.05 eV, respectively. The great resistance of the compact ceramic material to electrochemical oxidation correlates with its resistance to high-temperature oxidation above 1700°C. This is due to the formation of an Al2O3–SiO2 mullite film on the surface. The lower resistance of the coatings to electrochemical oxidation compared to the compact material is associated with their increased porosity.
      PubDate: 2020-11-28
       
  • Detonation-Sprayed Coatings of (Ti, Cr)B 2 –NiAlCr Composite Materials
           II. Mechanical and Tribotechnical Properties
    • Abstract: The mechanical and tribotechnical properties of detonation-sprayed coatings produced from (Ti, Cr)B2–NiAlCr composites were studied. The influence of various preliminary substrate treatment methods and refractory-to-metal ratio in the spray material on the coating–substrate adhesion strength, σad, was analyzed. Spraying a sublayer had no significant effect on the coating adhesion strength. The adhesion strength σad increased by 25–30% with the metal content changing from 25 to 75%, while σad = 120–145 MPa even at 25% NiAlCr. The hardness of the coatings changed within rather narrow limits (HV0.2 = 7–12 GPa), but the refractory-to-metal ratio varied over a wide range. The coatings containing a minimum amount of the metal component (25%) were predicted to have higher hardness, HV0.2 = 10–12 GPa, though it was almost half the hardness of the sintered compact material. At equal contents of the refractory and metal components, HV0.2 = 9–10 GPa; for the material containing 75% of the metal component, HV0.2 = 7–8 GPa. The tribotechnical properties of the coatings were studied in dry sliding friction conditions with ball-ondisk tests. At the initial friction stage, high pressures appeared in the contact zone (P ≥ 500 MPa). Therefore, in addition to high hardness, the coatings should have high strength. At 50–75% (Ti, Cr)B2, besides abrasion processes, brittle fracture and spalling of the coatings occurred. The best characteristics were shown by the coating produced from the material containing 25% (Ti, Cr)B2. Since the (Ti, Cr)B2 particles are fine, wetted well by the NiAlCr alloy, and uniformly distributed over the starting material and associated coating, even their relatively low content (25%) promotes high abrasion resistance and adhesion.
      PubDate: 2020-11-28
       
  • Thermodynamic Properties and Phase Equilibria in Ba–Sn Alloys
    • Abstract: The mixing enthalpies for liquid Ba–Sn alloys were determined by isoperibolic calorimetry at 1300 K over the entire composition range. Large exothermic mixing effects ( ∆Hmin = –54.8 ±± 1.8 kJ/mole at xBa = 0.56) were found. They are indicative of strong interaction between different components and of short ordering in the liquid alloys. The thermochemical properties of the melts and barium stannides and the phase equilibria in the Ba–Sn system were used to calculate the activities of components, molar fractions of associates, and formation enthalpies and entropies for liquid BaxSn1–x alloys with the ideal associated solution (IAS) model. Two associates, BaSn and Ba2Sn, were selected for the calculation. The calculated activities of components in the Ba–Sn melts show very large negative deviations from the ideal solution, which is consistent with their thermochemical properties. The maximum concentration of each associate is approximately 0.65 for respective compositions. The calculated formation enthalpies for BamSnn intermetallics are quite high exothermic values that agree well with the published data for BaSn3 and only qualitatively for Ba2Sn. The formation enthalpy for the associate agrees with that for the respective BaSn intermetallic and is slightly less exothermic for Ba2Sn. This all indicates that the bonding energies between different atoms in the respective intermetallics and melts are close to each other and quite high. The formation entropy for the Ba2Sn associate is lower and that for BaSn is higher in magnitude. This demonstrates different degrees of ordering in BaSn and Ba2Sn associates and intermetallics. This may be due to different changes in the oscillation frequencies of atoms and other factors. The calculated liquidus curve of the Ba–Sn phase diagram agrees with data for the Sn–Sr system.
      PubDate: 2020-11-28
       
  • Structural State of High-Entropy Fe 40–x NiCoCrAl x Alloys in
           High-Temperature Oxidation
    • Abstract: The evolution of phase composition and mechanical properties and the formation of oxide layers on Fe40–xNiCoCrAlx (x = 5 and 10 at.%) alloys in long-term oxidation at 900 and 1000°C were studied. In the initial cast state, depending on the aluminum content and valence electron concentration, the alloys contain only an fcc solid solution (VEC = 8 e/a) or a mixture of fcc and bcc phases (VEC = = 7.75 e/a). Thin continuous oxide scales containing Cr2O3 and NiCr2O4 spinel formed on the surface of both alloys oxidized at 900°C for 50 h. A further increase in the annealing time to 100 h leads to the formation of aluminum oxide Al2O3 in the scale on the Fe30Ni25Co15Cr20Al10 alloy, having high protective properties. An increase in the oxidation temperature to 1000°C results in partial failure of the protective layer on the alloy with 10 at.% Al. Long-term holding at 900°C (100 h) + 1000°C (50 h) does not change the phase composition of the Fe35Ni25Co15Cr20Al5 alloy matrix, being indicative of its high thermal stability. In the two-phase Fe30Ni25Co15Cr20Al10 alloy, the quantitative ratio of solid solutions sharply changes: the amount of the bcc phase increases from 4 to 54 wt.% and its B2-type ordering is observed. The mechanical characteristics of the starting alloys and those after long-term high-temperature annealing were determined by automated indentation. The hardness (HIT) and elastic modulus (E) of the cast Fe35Ni25Co15Cr20Al5 alloy are equal to 2 and 147 GPa, respectively, and decrease to 1.8 and 106 GPa after a series of long-term annealing operations. The Fe30Ni25Co15Cr20Al10 alloy shows the opposite dependence: HIT increases from 2.5 in the initial state to 3.1 GPa after annealing and E decreases from 152 to 134 GPa. This indicates that the Fe30Ni25Co15Cr20Al10 alloy is promising as a high-temperature oxidation-resistant and creep-resistant material.
      PubDate: 2020-11-28
       
  • Effect of Heat Treatment on the Physicochemical Properties of Ultrafine
           ZrO 2 –Y 2 O 3 –CeO 2 –Al 2 O 3 –CoO Powders
    • Abstract: Variations in the phase composition, specific surface area, and morphology of structural components in the ultrafine powder of composition (wt.%) 70 (90 ZrO2 (3 Y2O3, 2 CeO2)–10 Al2O3)–30 CoAl2O4 (70ZA30CoA), produced by hydrothermal synthesis combined with mechanical mixing, were studied in the heat treatment process up to 1300°C. The study employed Xray diffraction, scanning and transmission electron microscopy, petrography, and BET. The formation of CoAl2O4 in the 70ZA30CoA powder in the heat treatment process was accompanied by reversible phase transformations: T-ZrO2 → M-ZrO2 → T-ZrO2. The M-ZrO2 content increased from 15% to 46% in the temperature range 850–1000°C and decreased to 13% after heat treatment to 1150°C. The process involved slight coarsening of the primary T-ZrO2 particles, while the size of the primary M-ZrO2 particles remained practically unchanged. The phase transformation was due to a decrease in the free energy of the ultrafine 70ZA30CoA powder, representing a thermodynamically nonequilibrium system. The phase composition changed color of the 70ZA30CoA powder in the following sequence: gray → gray blue → dark cyan → bright blue. Morphological analysis of the structural components showed that the CoAl2O4 formation and reversible T-ZrO2 → M-ZrO2 phase transformation were accompanied by shape change, loosening, and subsequent sintering of the agglomerates. The chain-like agglomerates of various shapes and sizes indicate that the 70ZA30CoA powder sinters actively at 1300°C. The decrease in the specific surface area from 46 to 1 m2/g depending on the heat treatment temperature was determined by the development of three structural transformation processes: formation of CoAl2O4, phase transition of the ZrO2 solid solution, and sintering of the 70ZA30CoA powder. The established regularities are of fundamental importance for the microstructural design of ZrO2 composites such as ZrO2–Y2O3–CeO2–Al2O3–CoO materials of blue and other colors for various applied purposes.
      PubDate: 2020-11-28
       
  • Effect of Processing Parameters on the Structure and Properties of Powder
           Fe–Al Intermetallic Compounds Obtained by Sintering and Impulse Hot
           Pressing
    • Abstract: The paper examines the effect of high-energy grinding and post-treatment conditions on the structure and physical and mechanical properties of iron aluminide Fe–15 wt.% Al obtained by sintering and impulse hot pressing. It was shown that the grinding of a mixture of iron and aluminum powders in a planetary mill results in the formation of lamellar particles whose morphology is preserved in the alloy structure after sintering and impulse hot pressing. After grinding, sintered intermetallic compounds obtained from powder mixtures demonstrate low physical and mechanical properties due to the low quality of grain boundaries. The use of impulse hot pressing for compaction of samples from milled powders at temperatures of 850–1150°C significantly increases the density of intermetallic compounds compared to sintered materials of a similar composition—from 5 to 6.5 g/cm3. The increase in the temperature of impulse hot pressing contributes to an increase in mechanical characteristics, where the maximum values of bending strength and fracture toughness are 880 MPa and 21 MPa · m0.5, respectively. Subsequent hightemperature annealing (1350–1450°C) leads to an improvement of the quality of grain boundaries with the formation of a predominantly discontinuous grid, coagulation of impurity segregation, and, as a result, to a sharp increase in bending strength and fracture toughness, which are 1400 MPa and 27 MPa · m0.5, respectively. It was shown that the interparticle rupture observed in the samples after impulse hot pressing at relatively low temperatures changes to transcrystalline after hightemperature annealing.
      PubDate: 2020-11-28
       
  • High-Density Mo–W–Cu Pseudoalloys Based on Homogenous Mo–25% W
           Powder Alloy Produced by Reducing Oxide Powders in Moving Layers
    • Abstract: The article aimed to obtain a structural material with increased plasticity and density of 98.5–99.5% based on (Mo–25% W)–20 vol.% Cu pseudoalloys with a homogeneous refractory skeleton obtained by a single-time pressing and sintering of the dispersed mixture at temperatures 1400–1500°C. The production of a dispersed granulated Mo–25% W alloy with a powder particle size of 0.1–0.3 μm through the decomposition of complex ammonium paramolybdate and paratungstate salts into oxide compounds xWO3 · yMoO3 with their subsequent reduction by hydrogen in a rotary chamber was studied. Considering the temperature and decomposition time of complex salts in the moving layers, the physical and technological properties (such as phase composition, oxygen content, specific surface, bulk density, and tap density) of complex oxide powders xWO3 · yMoO3 and metal Mo– 25% W powders after reduction by hydrogen were compared with the corresponding properties of powders obtained in a stationary tube furnace in fixed layers. Temperature dependencies of porosity in (Mo–25% W)–20 vol.% Cu pseudoalloys after sintering at the temperature between 900 and 1500°C has been examined. It has been established that compaction of dispersed powder mixtures of (Mo–25% W)–20 vol.% Cu and homogenization of Mo–25% W alloy after sintering begin at the temperature 300°C lower than when sintering mechanical mixtures of commercial metal powders. It has been shown that (Mo–25% W)–20 vol.% Cu pseudoalloys obtained by liquid-phase sintering at 1500°C for 1 hour have the following characteristics: at 20°C, the ultimate tensile strength σt == 490 MPa, relative elongation δ = 1.1, Brinell hardness HB = 3.3 GPa, and at 500°C— σt == 370 MPa, δ = 4.4, and HB = 2.7 GPa.
      PubDate: 2020-11-27
       
  • Effect of Submicron SiC Particles on the Properties of Alcocrfeni High
           Entropy Alloy Coatings
    • Abstract: The high entropy alloy (HEA) coatings are potential candidates for advanced application in the protection of steel and other traditional alloys due to their excellent physical and mechanical performance. The AlCoCrFeNi alloy series were favorably studied due to comparably low cost and stable performance. In this research, the AlCoCrFeNi coatings were prepared through surface mechanical abrasion treatment (SMAT). The process implied the comprehensive effect of cold welding and friction. The submicron-size SiC particles were added into the raw materials in different amounts. For SMAT, a high-energy ball milling method was adopted to promote the alloying of metals, disperse SiCp, and combine the powder to the carbon steel substrate. Afterward, the phase composition, microstructure of coatings, and distribution of reinforcement were detected through XRD and SEM analysis, separately, and the effect of SiC particles content on the properties of the coatings was analyzed. The results show that the addition of submicron-sized SiC significantly improved the density and stiffness of the HEA coating and diminished defects and surface roughness. Сoatings containing SiC display enhanced adhesion force and wear resistance. The proposed mechanism is that the submicron SiC particles promoted mechanical alloying of pure metal and intensified the adherence and cold welding of the coating. Especially, herein, the addition of 15 wt.% SiC granted the best comprehensive properties of the coating. Excessive SiC content led to the deterioration of coating plasticity and the growth of cracks.
      PubDate: 2020-11-27
       
  • Effect of Powder Metallurgy Process and its Parameters on the Mechanical
           and Electrical Properties of Copper-Based Materials: Literature Review
    • Abstract: As the world is shifting towards renewable sources of energy, the demand for copper is increasing due to its excellent electrical and corrosion resistance properties. Although, because of low strength and wear resistance, the use of pure copper is quite limited. Various reinforcing materials are added to the Cu matrix to fabricate high-strength and wear-resistant copper matrix composites. Powder metallurgy is the most commonly used metal matrix composite fabrication method for Cu-based materials. Properties of a powder metallurgy product depend on the process parameters such as compaction pressure, sintering temperature, sintering time, type and rate of reinforcement, size of matrix and reinforcing elements, etc. In the present work, the influence of the above-mentioned parameters on mechanical and electrical properties of copper-based materials produced by the powder metallurgy method is reviewed in detail. The literature survey revealed that SiC, graphite (Gr), TiC, and graphene (Gn) are the most commonly used reinforcement additives in the Cu matrix for improvement of the strength and wear resistance of Cu-based materials. It has been established that the strength and wear resistance increase after the addition of the mentioned reinforcers, although the electrical conductivity decreases. For enhanced mechanical and electrical properties, a 4–6% weight fraction of micron-sized reinforcers, such as SiC, TiC, and graphite, and a 0.25–1% weight fraction of nano-sized reinforcers, such as CNTs and graphene, are considered the optimum reinforcement range for the Cu-matrix. Small particle size of 3–5 μm of matrix material (Cu) improves mechanical and electrical properties. The size of nano-reinforcers, such as CNTs, should be sufficiently larger (30–50 nm) to avoid agglomeration. Besides, factors contributing to better properties are the optimum range of compaction pressure of 550–650 MPa, sintering temperature of 800–900°C, and sintering time of 60–90 min.
      PubDate: 2020-11-27
       
  • Structure and Properties of TiAl-Based Alloys Doped with 2 at.% Mo
    • Abstract: Arc-melted Ti100–xMo2Alx alloys (where x is 44, 46, 48, and 50 at.% Al) that were produced from pure components were examined by X-ray diffraction and scanning electron microscopy with electron microprobe analysis (SEM/EDX). The melting points and solid-phase transformations were studied by differential thermal analysis (DTA) and the mechanical properties by fracture toughness, bending, and compression tests. The CALPHAD approach was used for thermodynamic calculation of phase equilibria in the composition region under study. The cast alloys mainly consist of a lamellar structure formed by lamellas of γ-TiAl and α2-Ti3Al phases with submicron thickness and a cubic Ti55Mo4–6Al39–40 phase of A2 type (β) or B2 type (β0). In the γ-TiAl-based alloys, molybdenum behaves as a low-melting dopant, enriching the grain periphery. The standard mechanical characteristics of the alloys were determined and their structural sensitivity was analyzed. All studied alloys demonstrate excellent high-temperature strength. The yield stress is 400–600 MPa in the temperature range 20–750°C. The strength slightly increases at 300 and 600°C under dynamic strain ageing. The strain hardening parameters were established over a wide range of test temperatures. The temperature dependence of the strain hardening coefficient and strain hardening index was analyzed for alloys in different phase and structural states. In the temperature range from 20 to 600°C, the strain hardening index and coefficient were found to vary slightly. The strain hardening index increased from n = 0.6 to n = 0.95 with aluminum content changing from 44 to 50 at.%, which indicates that the strain hardening mechanism changes with variation in the alloy phase constituents.
      PubDate: 2020-11-27
       
  • The Effect of Matrix and Processed Material Properties on the Performance
           of Diamond Drills
    • Abstract: The results of laboratory tests for drilling of corundum, chamotte, and porcelain with diamond tubular drills in running water, as well as the friction of cylindrical samples of the matrix against these materials, have been described. Bronze containing ultrafine ASM 1/0 diamond powders and molybdenum, as well as bronze without this reinforcement, served as the matrix for the drills and cylindrical samples. The speed of processing corundum, chamotte, and porcelain with diamond drills constantly increased when the concentration of diamond powders raised to 11 wt.%. At the same time, the tool wear significantly reduced, reaching the minimum at 5–9 wt.% of ASM 1/0 concentration (depending on the choice of the test material). The wear of diamond powder increased binsignificantly when the concentration of diamond powders grew to 11 wt.%. Similar results were obtained for the matrix of samples. Thus, the wear of the matrix samples decreased with an increase in the ASM 1/0 concentration. Such a decrease was observed even at 11 wt.% for friction against corundum. During friction against chamotte and porcelain, the wear of the samples reached the minimum at 7 wt.% diamond powders. As in the case with drills, a further increase in the content of ASM 1/0 in the reinforcement led to an increase in wear of the samples. High wear of the drills and samples at a relatively high content (11 wt.%) of ultrafine diamond powders was explained by the porosity that occurred in the matrix. The studies performed allowed concluding that reinforcement containing ultrafine ASM 1/0 diamond and molybdenum powders should be introduced into the matrix of diamond drills to improve their performance and decrease the consumption of abrasive material. The matrix samples containing up to 7 wt.% of ultrafine diamond powders can be successfully used as an abrasive tool for finishing (polishing) a series of nonmetallic materials, in particular, semiprecious and precious stones in jewelry production.
      PubDate: 2020-11-27
       
  • Structure and Wear Resistance of Plasma-Sprayed NiCrBSiC–TiCrC
           Composite Powder Coatings
    • Abstract: The NTC20 and NTC40 composite powders were produced by conglomeration from the NiCrBSiC self-fluxing alloy with additions of 20 and 40 wt.% TiCrC, respectively, using an organic binder. Since the organic binder burnt out in the plasma spray process, components of the composite powders segregated and a certain amount (up to 15–20 vol.%) of the TiCrC particles was lost. The plasma-sprayed NTC20 and NTC40 coatings showed a heterophase lamellar structure, consisting of a nickel-base matrix in which fine chromium boride and carboboride grains (1–2 μm) and TiCrC particles (5–8 μm) were evenly distributed. Electron microprobe analysis revealed a higher content of oxides in the NTC20 and NTC40 coatings compared to the NiCrBSiC coating, which was associated with the oxidation of TiCrC particles in the plasma spray process. The introduction of TiCrC additions into the NiCrBSiC self-fluxing alloy increased porosity of the plasma-sprayed NTC20 and NTC40 coatings (up to 8%) versus the NiCrBSiC coating (5%). Wear tests of the plasma-sprayed NTC20 and NTC40 coatings were performed in dry sliding friction conditions using 65G steel as a counterface. For comparison, a plasma-sprayed coating consisting of the serial NiCrBSiC self-fluxing alloy was tested. Additions of 20 and 40 wt.% TiCrC particles to the NiCrBSiC self-fluxing alloy increased the wear resistance of the plasma-sprayed coatings by 2 to 2.3 times. As the sliding speed increased from 4 to 12 m/sec, the NiCrBSiC coating underwent catastrophic wear (I ≈ 60 μm/km), while the wear rate of the NTC20 and NTC40 coatings remained constant (I ≈ 12–22 μm/km).
      PubDate: 2020-11-27
       
  • Mechanical Properties of Microlayered Ti–Al Materials in Static and
           Cyclic Loading
    • Abstract: The technique for producing microlayered materials by sintering and rolling a package of alternating titanium and aluminum ribbons at 460 and 770°C is presented. The initial package thickness was 2.6 mm and the final thickness after hot rolling was 1.8 mm. Then the preform was rolled at room temperature to a thickness of 0.5 mm. The total strain at 20°C was e = ln1.8/0.5 = 1.3. Some ribbons 0.5 mm thick stratified in the middle and were tested by static and cyclic bending. X-ray diffraction found that the material that was heated and rolled at 770°C contained an hcp titanium phase and a TiAl3 phase. Structural anisotropy in titanium layers was established. The proportional limit of the 0.5 mm thick material was 368 MPa. The elastic characteristics, transmission energy of vibrations, and fatigue strength of the microlayered Ti–TiAl3 samples 0.25 mm thick cut along and across the rolling direction were determined. For this purpose, firstand second-mode resonant bending vibrations of cantilevered samples were excited and dependences of the maximum stresses in the samples on machine (electrodynamic shaker) power, W/Wmax, were found. The destructive fatigue stresses in the samples versus the number of load cycles were determined as well. Young’s modulus of the samples cut out along the rolling direction was 92 and for the samples cut out across the rolling direction was 100 GPa. The microlayered Ti–TiAl3 material along the rolling direction is less perfect than that across the rolling direction since nondestructive stresses are 11% lower along the rolling direction because of greater energy dissipation in anisotropic crystallographic structure, the relative excitation power of vibrations being the same. The ultimate strength determined from 107 cycles (Troll = 460°C) was 303 MPa for the Ti–Al samples along the rolling direction and 299 MPa for the Ti–TiAl3 samples along the rolling direction and 481 MPa for those across the rolling direction.
      PubDate: 2020-11-03
       
  • Nitriding of Sintered VT1-0 Titanium Alloy
    • Abstract: Components produced from sintered titanium alloys are increasingly used in mechanical engineering but need to be protected for operation in corrosive environments because of porosity. Nitriding is one of the effective protection methods. The objective of the study was to analyze the nitriding kinetics of a sintered VT1-0 titanium alloy at atmospheric (105 Pa) and reduced (1 Pa) nitrogen pressure at 800, 850, and 900°C for 5, 10, and 20 h versus a wrought titanium alloy of the same composition. The study employed discrete gravimetry, hardness measurement, optical and electronic metallography, profilometry, and X-ray diffraction. The nitriding kinetics of the VT1-0 titanium alloy sintered from titanium powder alone and from a mixture of titanium and titanium hydride powders was studied in comparison with wrought titanium. Under the nitriding parameters in question, the weight gain of all samples was described by a parabolic law and the weight gain of the sintered samples was higher than that of the wrought ones. The kinetic parameters of nitriding for the sintered and wrought VT1-0 titanium alloys were determined for the first time in the test temperature–time and gas dynamic conditions. Changes in the surface and near-surface layers depending on metal porosity were shown. After nitriding, the surface microhardness of the sintered titanium was lower than that of the wrought titanium samples because of porosity, and the strengthened surface layer was thicker. The nitride film formed on the sintered titanium alloy was thinner and less distorted than that on the wrought titanium alloy. The results can be used to develop nitriding conditions for sintered VT1-0 titanium products.
      PubDate: 2020-11-03
       
  • Structure and Wear Resistance of FeNiCrBSiC–MeB 2 Electrospark
           Coatings
    • Abstract: The structurization of coatings produced by electrospark deposition (ESD) from the commercial selffluxing FeNiCrBSiC alloy and FeNiCrBSiC-based composites, such as FTB20 (FeNiCrBSiC–20 wt.% TiB2) and FCB20 (FeNiCrBSiC–20 wt.% CrB2), on a steel 45 substrate was studied. The electrospark FeNiCrBSiC coating about 70 μm thick has a globular surface and the FTB20 and FCB20 coatings form a continuous layer up to 50 μm thick over the entire samples. The microhardness does not change across the deposited coating thickness and is 10–14 GPa. The chemical compositions of the ESD coatings and the electrodes are the same, which indicates that the electrode material does not mix with the steel substrate. The structure of the FeNiCrBSiC, FTB20, and FCB20 electrodes and coatings differs significantly because chromium boride and/or titanium boride inclusions refine from 20–25 μm to 1 μm in the ESD process. The heterophase structure of the ESD coatings represents a nickel–iron-base matrix reinforced with fine boride and carboboride particles. The effect of speeds and loads on the wear rate of ESD coatings in dry friction conditions was examined. Electrospark coatings produced from the WC–6% Co hardmetal were tested as wear resistance reference. The wear rate of the FeNiCrBSiC, FTB20, and FCB20 coatings decreases and that of the WC–6% Co coating increases when the speed rises from 4 to 12 m/sec. The wear rate of the ESD coatings becomes one order of magnitude higher when the load increases from 0.1 to 0.4 MPa. Analysis of the friction surfaces showed that wear of the FeNiCrBSiC coating was caused by failure of the globules and that of the FCB20 coating by brittle fracture of the deposited layer. The ESD FTB20 coating has two to three times higher wear resistance than the FeNiCrBSiС coating because of the oxidative wear mechanism whereby protective oxide films develop on the friction surfaces and act as a solid lubricant.
      PubDate: 2020-11-02
       
  • Composite Materials in the TiN–Cr 3 C 2 –C/Matrix System
    • Abstract: The influence of modifying additions on the strength and tribological properties of titanium nitride composites has been examined. The lowest contact angle (25–30°) is shown by the PG12N-01 alloy, containing chromium, boron, silicon, and carbon. Relatively porousless structures can be produced in the TiN–PG12N-01 system when chromium carbide and carbon are introduced into the composite as graphite, contributing to the formation of TiCN to improve wetting and adhesion. Graphite introduced additionally as an impurity remains after sintering as an individual uniformly distributed phase integrated into the overall composite structure. This graphite can successfully act as a dry lubricant, improving the service characteristics. In addition, it activates sintering of the composite allowing it to become almost porousless. The optimum sintering temperature falls in the range 1450–1500°C depending on carbon and metal matrix contents. The resultant composites have 300–500 MPa strength and 16.1 GPa hardness. The highest strength can be reached through an optimum combination of graphite and PG12N-01 matrix. The mechanical characteristics deteriorate when the amount of these components is higher or inadequate. The antifriction characteristics of the materials have been tested by dry end friction (at a speed of 8 m/sec, 50 MPa pressure in the contact area, and 10 km sliding path) against a 65G steel counterface with 60 HRC hardness: friction coefficient has been found to be 0.27–0.3 and wear resistance 0.2 ± 0.02 μm/km. The developed ceramic materials thus have high strength and antifriction characteristics and can be used in dry friction conditions at high speeds and loads.
      PubDate: 2020-10-31
       
  • Hot Free Forging of Iron-Based Powder Pellets
    • Abstract: The hand forging of cylindrical powder pellets of small weight (8.0–8.5 g), pressed at 700 MPa from mixtures of iron and graphite powders, was studied. The pre-sintered pellets were heated in charcoal at 1100°C and subjected to double-ended face forging on a heated flat anvil with a hammer with a flat striker and naturally cooled on a steel plate. The vertical setting of the forged pellets was 70-80%. The pellets were cut into samples for analysis. The influence of the graphite content on the compaction process and the mechanical properties of powder materials during hot free face forging have been established. The improvement in the properties of materials with a high graphite content (4 and 12%) was shown to be due to an increase in the number of sections for hot welding of iron grains. It is associated with shear deformation of the pellet material during free forging, contributing to the emergence of new iron–iron contacts. The high characteristics of materials containing 1.7% graphite are due to the action of several mechanisms in parallel: the dissolution of carbon in iron, decrease in total porosity, elimination of interparticle gaps, and grain refinement under shear deformation. The use of a steel shell makes it possible to significantly expand the range of powders and powder composites without rupture of the pellets in hot forging. The combination of experimental results and analytical data allowed us to conclude that hand forging was promising for a quick and cheap screening of formulations for dense powder materials.
      PubDate: 2020-10-31
       
  • The Influence of Thermomechanical Treatment on the Strain Behavior of the
           Fe–Ni–Co–Ti Ferromagnetic Alloy Nanocomposite with Shape Memory
           Effect
    • Abstract: The paper describes mechanical tests of a nanocomposite produced from the ferromagnetic shape memory Fe−Ni−Co−Ti alloy under uniaxial tension over a wide temperature range. The production of the nanocomposite was preceded by preliminary thermomechanical treatment (TMT), involving drawing, quenching, and ageing, for precipitation hardening. The TMT imparted high superelastic strain and shape memory effect to the nanocomposite. The preliminary TMT with strain ψ = = 7.4−22.5% aged at T = 650°C for 5−10 min was experimentally found to correspond to the optimal combination of the maximum superelastic strain and shape memory effect. This contributed to the phase and twinning plastic deformation of the nanocomposite over the test temperature range Ms < Ttest < Af (where Ms is the start temperature of forward martensitic transformation on cooling and Af is the finish temperature of reverse martensitic transformation on heating). A plateau with constant stress was found in the two-phase Mf < Ttest < Ms region on the tensile curve at drawing strain ψ = 22.5%. A significant increase in the preliminary strain (more than 40%) substantially stabilized the austenitic matrix, thus inhibiting the martensitic transformation and reducing reversible effects because the austenite grain size refines when the lattice defect density increases. The austenite grain size distribution was assessed versus the chosen TMT conditions. When the austenite grain size increased, the superelastic strain recovery became higher. The factors leading to greater superelasticity were analyzed within different phenomenological models. The TMT has a crucial role in the variation of structure and mechanical properties, in turn promoting inelastic effects at different temperatures.
      PubDate: 2020-10-31
       
  • Detonation-Sprayed Coatings of (Ti, Cr)B 2 –NiAlCr Composite Materials
           I. Deposition Technique and Composition and Microstructure of Coatings
    • Abstract: Coatings of (Ti, Cr)B2–NiAlCr cermet materials were deposited on structural steel substrates by detonation spraying. The optimal spray conditions depending on the ratio of structural components were determined for the materials developed. The effect exerted on the coating microstructure and composition by the content of refractory and metal components in the sprayed material was examined. A heterophase lamellar microstructure with the phases being distributed quite uniformly was formed. Coatings from materials with a greater content of the metal component have more uniform phase distribution, which largely depends on the process characteristics of the powders. The NiAlCr alloy-base powders have three to four times higher flowability than the (Ti, Cr)B2-base powders, promoting more stable powder supply and spray process as a whole. The coatings thus show higher density and more uniform phase distribution. Various coating structures were analyzed: without a sublayer, with a NiCr detonation-sprayed sublayer, and with an electrospark-deposited sublayer produced from the same material as used for the main coating. The resultant coatings have high-quality adhesive contact with the substrate, both with and without a NiCr detonation sublayer, and their thicknesses can reach 0.8–1 mm. When an electrospark-deposited sublayer with a high (Ti, Cr)B2 content was used, cracks were found at the coating–sublayer interfaces. This is due to higher hardness and lower ductility of the sublayer under the action of accelerated spray particles. Preliminary surface treatment by spraying different types of sublayers hardly influences the microstructure of the coatings and the quality of their contact with the substrate.
      PubDate: 2020-10-31
       
 
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