Self-propagating high-temperature synthesis (SHS) or combustion synthesis (CS) is a rapidly developing research area. SHS materials are being used in various fields, including mechanical and chemical ...engineering, medical and bioscience, aerospace and nuclear industries. The goal of the present paper is to provide a comprehensive state-of-the-art review and to analyse a critical mass of knowledge in the field of SHS materials and coatings. We also briefly discuss the history and scientific foundations of SHS along with an overview of the technological aspects for synthesis of different materials, including powders, ceramics, metal-ceramics, intermetallides, and composite materials. Application of CS in the field of surface engineering is also discussed focusing on two main routes for applying SHS to coating deposition: (i) single-step formation of the desired coatings and (ii) use of SHS-derived powders, targets or electrodes in the coating deposition processes.
Light (density <2.7g×cm−3) yet strong (tensile strength >350MPa) metal matrix composites (MMCs) are highly anticipated for aerospace and automotive industries. The MMCs application fields can be ...significantly expanded if they possess enhanced strength at elevated temperatures also. In the present study, Al-based composites loaded with either micro- or BN nanoparticles (BNMPs and BNNPs) with up to 10wt% of BN phase were produced via spark plasma sintering (SPS) of ball-milled Al-BN powder mixtures. A dramatic increase in the composite tensile strength compared to pure Al samples (up to 415%) was demonstrated during tensile tests both at 20°C and 500°C. BNMPs were found to be a more preferred additive compared with BNNPs due to the formation of more homogeneous and uniform morphologies within the ball-milled powder mixtures and resultant SPS products. The most impressive tensile strength of 170MPa at 500°C was achieved for an Al-7wt% BNMPs SPS composite, as compared to a value of only 33MPa for a pure Al SPS-produced sample. The reinforcement mechanism was uncovered based on detailed X-ray diffraction analysis, differential scanning calorimetry, Raman spectroscopy, scanning and high-resolution transmission electron microscopy and energy-dispersion X-ray analysis. Microscale BN, AlB2 and AlN inclusions acting within Al-matrices in the frame of Orowan strengthening mechanism, and pre-formed during ball-milling-induced pre-activation of Al-BN powder mixtures, finally crystallized during SPS processing and ensured the dramatically improved tensile strength and hardness of the resultant composites.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Hexagonal boron nitride (h-BN) nanosheets, spherical W nanoparticles, and their combinations were utilized as lubricant additives to synthetic PAO6 oil. The addition of W NPs led to a decrease in the ...coefficient of friction and wear rate. Molecular dynamics (MD) simulations and in situ TEM mechanical tests showed that the positive effect of adding spherical W NPs can be attributed to their rolling and sliding in the tribological contact zone. Adding BN nanosheets to PAO6 also improved the tribological performance of friction pairs: MD simulations suggest that the exfoliation and sliding of BN layers under tribological contact can contribute to the reduction of friction and wear. Moreover, a synergistic effect from the simultaneous addition of W and BN nanoparticles was observed: the CoF and wear reached minimum values among all tested suspensions. The formation of W/BN core/shell structures by wrapping of W nanoparticles by h-BN sheets provided superior macroscale lubricity.
•h-BN nanosheets and spherical W nanoparticles are studied as additives to PAO6 oil.•Adding W and BN NPs leads to a decrease in the friction coefficient and wear rate.•Exfoliation and sliding of h-BN NPs contribute to friction and wear reduction.•W NPs can withstand a high applied load and slide or rotate in the direction of applied load.•Formation of W/BN core/shell structures provides superior macroscale lubricity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The offshore and coastal infrastructure needs additional protection from wear, corrosion, and tribocorrosion. Herein, electrospark deposition (ESD) was employed to deposit composite TaC-(Fe,Mo,Ni) ...and (Ta,Zr)C-(Fe,Mo,Ni) coatings with a metallic matrix (similar in elemental composition to that of stainless steel) reinforced with carbide nanoparticles. The coatings were produced using TaC–Mo–Ni and TaC–ZrC–Mo–Ni electrodes under different energy regimes by varying frequency, voltage, and pulse duration to obtain different carbide contents. The obtained coatings have a bilayer composite structure: core-shell TaC–ZrC crystallites embedded in an Fe-based metal matrix with a (Ta,Zr)C network (zone 1) and approximately 5 nm Fe-based nanocrystallites surrounded by amorphous interlayers (zone 2). The tribological properties of TaC-(Fe,Mo,Ni) and (Ta,Zr)C-(Fe,Mo,Ni) coatings were superior to those of uncoated AISI 304 stainless steel, both in the 3.5% NaCl solution and in 3.5% NaCl + SiC suspension. The electrochemical characteristics of the best coatings were comparable to those of the stainless steel. Tribocorrosion tests indicated that when load is applied, the open-circuit potential values of steel reduce more significantly than those of the coatings.
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•Composite Ta(Zr)C-(Fe,Mo,Ni) coatings obtained by electrospark deposition in vacuum.•Carbide grains with core-shell structure: Zr-rich core, Ta-rich shell.•Coatings with enhanced tribological properties in 3.5% NaCl and SiC suspension.•In stationary corrosion Ta(Zr)C carbides protect Fe-based matrix.•At polarization, corrosion is determined by dissolution of more active matrix phase.
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•Hard Mo-Si-B and Mo-Al-Si-B coatings with h-MoSi2 phase as a main component.•Mo-Si-B possess higher hardness, improved oxidation resistance and better thermal stability.•Coatings ...withstand short-term oxidation at 1600 (Mo-Al-Si-B) and 1700°C (Mo-Si-B).•Oxidation is accompanied by phase transformations with formation of MoB and Mo5Si3 phases.
Mo-Si-B and Mo-Al-Si-B coatings were deposited by DC magnetron sputtering of MoSiB and MoAlSiB composite targets fabricated by the self-propagating high-temperature synthesis method. The structure, element and phase composition of coatings were studied by means of scanning and transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive spectroscopy, and glow discharge optical emission spectroscopy. To evaluate their oxidation resistance, the coatings were annealed in air in the temperature range of 1200–1700°C during different time slots between 10min and 5h. The obtained results demonstrated that the Mo-Si-B coatings possess higher hardness, improved oxidation resistance and better thermal stability compared with their Mo-Al-Si-B counterparts. The 7-μm thick Mo-Si-B coatings were shown to successfully withstand oxidation during short-time exposure for 10min at a temperature as high as 1700°C due to the formation of protective silica scale. The oxidation of Mo-Al-Si-B coatings was accompanied by the diffusion of aluminum to the coating surfaces and the formation of a single Al2O3 layer at 1200–1300°C and a double Al2O3-SiO2 layer at 1500°C which were less protective against oxidation. The surface oxidation processes were also accompanied by phase transformations inside the oxygen-free part of both Mo-Si-B and Mo-Al-Si-B coatings with the formation of MoB and Mo5Si3 phases.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Hard-yet-tough coatings are required to protect structural materials, cutting, stamping, and forging tools operating under harsh conditions that combine wear, corrosion, and elevated temperatures. To ...reveal the high potential of niobium (Nb) as an additive to binary Ti-based coatings, single-layer and multilayer Nb-doped TiC coatings were obtained by pulsed arc evaporation (PAE), electro-spark deposition (ESD) in vacuum, and combination of these methods. Structure, elemental, and phase compositions were studied by means of X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The coatings were characterized in terms of their hardness, elastic modulus, tribological properties, and electrochemical behavior in 3.5% NaCl solution. Tribological tests were carried out under various conditions, such as applied load (5 and 10 N), medium (air and 3.5% NaCl solution), and counterpart material (Al2O3 and 440C steel). Thin PAE coating (1.8 μm thick) consisted of 2–5 × 50–100 nm (Ti,Nb)C crystallites, elongated in direction of the coating growth, embedded in an amorphous matrix (75% sp2 + 25% sp3-hybridized carbon). Thick ESD coating (20 μm) contained TiC grains uniformly distributed in an eutectic Fe(Co)-Fe2(Ti,Nb) matrix with a minor content of Ti-Ni and γ-Fe phases. The single-layer PAE coating demonstrated superior tribological performance both in air and 3.5% NaCl solution, as well as high oxidation resistance during tribocorrosion tests. As a top layer in the PAE/ESD coating, it provided wear protection of less wear-resistant ESD sublayer. It is assumed that the main benefit of the ESD sublayer in the PAE/ESD coating may be that it provides enhanced toughness and high thickness, which prevents a soft substrate from high stress-induced plastic deformation.
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•TiNbC coatings by pulsed arc evaporation (PAE) and electro-spark deposition (ESD)•PAE coatings consist of elongated TiNbC crystallites in a-C matrix (sp2 + 25% sp3)•PAE coatings show superior tribological performance in air and 3.5% NaCl solution•PAE layer provides substantial wear protection of less wear-resistant ESD sublayer
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Silver is the most famous bactericidal element known from ancient times. Its antibacterial and antifungal effects are typically associated with the Ag ionization and concentration of Ag+ ions in a ...bacterial culture. Herein we thoroughly studied the influence of surface topography and roughness on the rate of Ag+ ion release. We considered two types of biocompatible and bioactive TiCaPCON-Ag films with 1 and 2 at. % of Ag and nine types of Ti surfaces with an average roughness varying in the range from 5.4 × 10–2 to 12.6 μm and different topographic features obtained through polishing, sandblasting, laser treatment, and pulsed electrospark deposition. It is demonstrated that the Ag+ ion release rates do not depend on the Ag content in the films as the main parameter, and it is other factors, such as the state of Ag agglomeration, surface topography and roughness, as well as kinetics of surface oxidation, that play a critical role. The obtained results clearly show a synergistic effect of the Ag content in the film and surface topography and roughness on Ag+ ion release. By changing the surface topographical features at a constant content of bactericidal element, we showed that the Ag+ ion release can be either accelerated by 2.5 times or almost completely suppressed. Despite low Ag+ ion concentration in physiological solution (<40 ppb), samples with specially fabricated surface reliefs (flakes or holes) showed a pronounced antibacterial effect already after 3 h of immersion in E. coli bacterial culture. Thus, our results open up new possibilities for the production of cost-effective, scalable, and biologically safe implants with pronounced antibacterial characteristics for future applications in the orthopedic field.
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IJS, KILJ, NUK, PNG, UL, UM
The present paper gives a detailed description of structural changes in three types of MoCN–Ag coatings (Mo51C15N27Ag7, Mo40C31N23Ag6, and Mo43C14N40Ag3) during dynamic temperature ramp tribological ...tests with particular emphasis on the analysis of wear products to identify adaptive friction mechanisms in the temperature range between 250 and 550°C. Thorough structural characterization using high-temperature XRD, SEM, TEM, GDOES, and Raman spectroscopy provided evidence of various tribo-chemical reactions in the zone of tribological contact affecting lubrication. The coating lubrication in the temperature range between 100 and 400°C was observed to be different. Unlike Mo51C15N27Ag7 coating whose friction coefficient monotonously increased with increasing temperature from 25 to 250°C, the Mo40C31N23Ag6 coating demonstrated low values of friction coefficient up to 250°C due to the tribo-activated formation of carbon-based fibers normal to the sliding direction. The good lubrication of the Mo43C14N40Ag3 coating at elevated temperatures was attributed to almost no wear due to its high hardness and to the formation of a thin tribo-activated MoO3 film at 350°C. However, complete oxidation of the wear track at 400°C resulted in intensive abrasion wear and high friction. Above 400°C, all coatings demonstrated similar values of friction coefficient irrespective of phase composition (melt, Ag6Mo10O33, or MoO3+Ag).
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•Low-friction coatings for broad temperature range•Various tribo-chemical reactions in the tribological contact zones at elevated temperatures•Low friction coefficients due to tribo-activated formation of carbon-based fibers•Good lubrication of MoCN–Ag coatings at elevated temperatures due to almost no wear•Tribo-activated formation of silver molybdate rods with turbostratic structure at 550°C
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Al-based composites with enhanced thermomechanical properties are in high demand. However, obtaining a uniform distribution of the strengthening phase in the metal matrix and achieving a strong ...metal/ceramic interface is still a great challenge. In this work, nanoAl/nanoSiC powder mixtures after high-energy ball milling were treated with Ar microwave plasma. Plasma processing was designed to remove the initial oxide film covering Al nanoparticles (NPs) and adsorbed impurities from the surface of SiC NPs, improve the wetting of SiC with Al melt, prevent SiC nanoparticle agglomeration, and ensure their uniform distribution in the metal matrix. During plasma treatment, Al/SiC composite particles were obtained, which were subsequently utilized as ready-made structural blocks with uniformly distributed reinforcing SiC NPs to obtain Al/SiC composites with 5, 10, and 30 wt% of SiC. Spark plasma sintered Al/SiC composites using plasma-treated powder mixtures showed approximately 20% higher tensile strength. The addition of 10% SiC led to an increase in hardness by 480% (145 HV), tensile strength by 70% (317 MPa) and 95% (238 MPa) at 25 °C and 500 °C, respectively, compressive strength by 135% (578 MPa), and wear resistance by 35–50%. The effect of point defects at the Al/SiC interface, such as impurity oxygen atoms and Si monovacancies, on the binding energy and temperature-dependent critical shear stress at the interface was assessed using molecular dynamics simulations with machine learning interatomic potentials. Our study demonstrated that the plasma-chemical treatment of Al/SiC powder mixtures is a promising approach for improving the thermomechanical properties of the Al/SiC composites.
•Al/SiC composites obtained by high-energy ball-milling and spark plasma sintering.•Microwave Ar plasma treatment of nanoAl/nanoSiC powder mixtures prevents SiC agglomeration.•Plasma processing leads to uniform distribution of SiC nanoparticles in Al matrix.•Adding 10% SiC significantly increases composite strength at room and elevated temperatures.•Silicon vacancies and oxygen atom impurities at Al/SiC interface increase critical shear stress.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Powders based on tantalum disilicide and silicon carbide were fabricated by mechanical activation-assisted SHS of reaction mixtures, with SiC concentration varied from 10 to 70%. The single- and ...double-layer composite targets were produced by hot pressing and further utilized for deposition of Si-Ta-C-(N) coatings by magnetron sputtering. The optimal hot pressing regimes, which allowed the production of dense ceramics with a hierarchical structure at 10 and 30% SiC, were determined. These ceramics were characterized by a relative density of 96–97%, hardness of ~19 GPa, and fracture toughness of 6.5–6.7 MPa × m1/2. The nanocomposite Si-Ta-C-N coatings consisted of fcc Ta(Si,C,N) solid solution (TaSi2–30%SiC target) and Ta5Si3 compound (TaSi2–10%SiC target) embedded in an amorphous matrix. Depending on the elemental composition, hardness and Young's modulus of the coatings were 16–26 GPa and 155–268 GPa, respectively. The coatings are characterized by high thermal stability and oxidation resistance at temperatures up to 800 °C. Tribological tests demonstrated the decrease of the coefficient of friction (CoF) of the coatings with increasing temperature: from 0.38 (25 °C) to 0.28 (600 °C) and 0.23 (800 °C). The low wear rate and CoF of the Si-Ta-C-N coatings at elevated temperatures are explained by the formation of a thin (~100 nm) oxide layer and TaSixOy microfibers on the coating surfaces.
•TaSi2-SiC powders were fabricated by mechanical activation-assisted combustion synthesis.•TaSi2-xSiC targets (x = 10, 30) had high relative density, hardness, and fracture toughnes.•Si-Ta-C-(N) coatings consisted of small (<3 nm) Ta(Si,C,N) or Ta5Si3 crystallites embedded in an amorphous matrix.•Si-Ta-C-(N) coatings showed high thermal stability and oxidation resistance at temperatures up to 800 °C.•Si-Ta-C-(N) coatings demonstrated low friction and wear rate at elevated temperatures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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