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.
EP741NP superalloy was fabricated by laser powder bed fusion (LPBF) and subsequently subjected to different heat treatments including hot isostatic pressing (HIP), solution + aging, ...HIP + solution + aging. The structural features of the alloy in the as-built condition as well as after heat treatment were studied and compared to its mechanical characteristics such as hardness, tensile strength, impact strength, and compression strength at elevated temperatures. It was found that LPBF samples have a fine-grained columnar-cellular microstructure formed from colonies of primary dendrites and poor mechanical properties caused by structural defects (pores and isolated microcracks). The Laves phases of different compositions (Cr2Nb, Co2Nb and Cr2Hf) were detected in the interdendritic space. HIP contributes to elimination of microcracks, precipitation of the γ′ phase (0.5–7 μm in size), dissolution of the Laves phases, and formation of MeC carbide phases. A combination of these events increases strength and ductility of the alloy. Solution followed by aging without HIP results in formation of the fine-grained γ′ phase with size ranging from 150 nm to 2 μm, elimination of the Laves phases, and precipitation of MeC carbides (Cr23C6), which enhances strength. Ductility, however, remains low as the alloy structure still contains microcracks. The LPBF samples subjected to combined post-treatment (HIP + solution + aging) exhibit the maximum mechanical properties due to the elimination of structural defects during HIP and formation of the fine-grained γ/γ’ microstructure during solution and aging.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Powders of heat-resistant NiAl-8Cr-6Co-xMo-1 Nb-0.9Hf (x = 0, 2, 4 and 6 at% Mo) alloys were successfully obtained by high-energy ball milling (HEBM) and combustion synthesis. Powders with the grain ...size of 10–55 µm were characterized by high flowability (up to 30 s) and bulk density (up to 3.1 g/cm3) due to the absence of submicron-sized particles. Compacted samples having a finer-grained (<5 µm) structure were produced from the combustion-synthesized powders by hot isostatic pressing (HIP). Molybdenum doping gave rise to a duplex structure consisting of NiAl and (Cr, Mo) grains. High-resolution electron microscopy (HRTEM) and selected area electron diffraction studies of the fine structure of the alloys detected that there are nanoparticles of refractory compounds (Co2Nb, Cr2Nb, (Hfx, Nby)C, and Ni2AlHf) along the grain boundaries and in grain bulk, which improve resistance to viscoplastic strain at temperatures above 800 °C. Molybdenum was shown to affect the mechanical properties of the base alloy in compression tests at 500–1100 °C. Two predominant mechanisms of alloy deformation were identified: glide of matrix dislocations and mechanical twinning.
•Heat-resistant NiAl-8Cr-6Co-(0…6)Mo-1 Nb-0.9Hf (% at.) alloys obtained by HIP of combustion synthesized powders are investigated.•Thermally stable compounds (Cr2Nb, Co2Nb, (HfxNby)C and Ni2AlHf) responsible for the high-temperature strength were detected using HRTEM.•Thermomechanical behavior of NiAl-8Cr-6Co-xMo-1 Nb-0.9Hf alloys under compressive stresses at 900 C were investigated.
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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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•Coatings on Cf/C-SiC were obtained by melting of ZrSi2-MoSi2-ZrB2 SHS-powder layers.•The oxidation kinetics at 1650 °C in static air obeys the logarithmic law.•Heterogeneous ...borosilicate glass, ZrO2 and SiO2 layers are formed during oxidation.•The glass phase was doped with Zr and the secondary Mo/MoO2, Mo3Si, Mo5Si3 phases were formed.•The ZrSi2 end-to-end oxidation determines the exhaustion of the coatings protective effect.
In this work, we investigate the oxidation resistance of the coatings manufactured by reactive impregnation of Cf/C-SiC composites with a melt derived from layers of ZrSi2-MoSi2-ZrB2 powder composition synthesized by SHS and alternating layers of SHS powders and elemental Si. Oxidation resistance tests were conducted in static conditions at 1650 °C in air and under an air plasma torch at 2200 °C. The performance of the coatings in these conditions is defined by the emergence and evolution of the heterogeneous oxide films based on zirconia-modified borosilicate glass. The protective oxide layers effectively inhibit the oxygen influx and further oxidation of the substrate. The increase of temperature above 1750−1800 °C resulted in evaporation of the glass phase from the surface and formation of porous thermally insulating ZrO2-based layer with Mo/MoO2, Mo3Si, and Mo5Si3 inclusions. The gradient of temperature across the coatings’ thickness allows for a partial retainment of the glassy phase in the coatings’ lower layers due to the decrease of partial pressures of boron and silicon suboxides, resulting in an additional degree of protection against oxygen diffusion. The specimens were characterized in terms of the temperature and time boundaries of their performance, mass loss kinetics, catalytic activity, and spectral emissivity of the coatings. The limiting factors of the coatings’ performance are outlined.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The kinetics of the pulsed electrospark deposition of coatings onto a nickel alloy substrate in air using compositions of SHS Mo-Si-B electrodes were investigated. The optimal frequency–energy regime ...of electrospark treatment (E=0.048J, I=120 A, f=3200Hz, and τ=20μs) characterized by the minimum roughness of the coating surface was determined. The structure, phase composition, and properties of the coatings were comprehensively studied. The wear patterns of the coatings were analysed in tribological tests. The coatings were shown to significantly enhance the hardness, as well as heat and wear resistances, of the nickel alloy and are recommended for use in the protection of critical components.
•Coatings obtained by PED process with MoSiB electrodes improve the hardness, heat and wear resistances of Ni alloy•Optimal regimes of PED process facilitates the coating with roughness 6-8 μm and 100% continuity•Oxidation at 700 °C leads to a weight loss of the samples with PED coatings because of the volatile MoO3•Electrodes with compositions Mo5SiB2–2%Mo3Si–2%Mo and MoSi2–9%MoB–2%Mo5Si3 were recommended for PED of Ni alloys
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The kinetics and stages of phase formation in the combustion wave of the MoAlB mixture are studied. The phase diagrams in the Mo-Al-B system were built using the AFLOW and Materials Project ...databases. The time-resolved X-ray diffraction analysis demonstrate that the MoAlB phase crystallizes from the melt without formation of any intermediate compounds. The structure of the synthesized ceramics was MoAlB lamellar grains 0.4 µm thick and ~2–10 µm long. Compact samples characterized by homogeneous structure and low residual porosity were obtained by hot pressing of SHS powders. The ceramic MoAlB has a layered structure, which is consistent with the morphology of the synthesis products. Mechanical and thermophysical properties are measured for samples obtained under optimal HP conditions at 1300 °C. The calculated value of the oxidation rate for MoAlB at 1200 °C for 30 h was 2.21∙10−5 mg/(cm2∙s). Oxide layer ~14 µm thick consists of elongated polygonal Al2O3 grains.
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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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•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
Abstract
The procedure for in situ TEM measurements of bonding strength (adhesion) between diamond and the metal matrix using a Hysitron PI 95 TEM Picoindenter holder for mechanical tests and ...Push-to-Pull devices was proposed. For tensile tests, dog-bone shaped lamellae 280–330 nm thick and ~ 2.5 µm long were used as objects of study. The lamellae were manufactured using the focused ion beam technology from the metal–diamond interface of diamond-containing composite material with a single-phase binder made of Fe–Co–Ni alloy. The experimentally determined bonding strength was 110 MPa.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Ti–Al–Nb–Mo–B alloy was successfully produced via high-energy ball milling (HEBM), self-propagating high-temperature synthesis (SHS) and hot isostatic pressing (HIP) techniques. HEBM was used to ...prepare powder mixtures with different types of microstructure and homogeneous distribution of the components. After SHS in thermal explosion mode powder grains with a microgradient structure were synthesized: their central part consists of α2-Ti3Al and the peripheral part consists of γ-TiAl. Compacted samples with duplex fine-grained structure and high thermomechanical properties (σ0.2 = 1245 MPa and 524 at 20 °C and 800 °C, respectively) have been obtained using the HIP technology. It was found, that mechanical twinning is the preferential deformation mechanism of the studied Ti–Al–Nb–Mo–B alloy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The creep process of coarse-grain WC-6%Co hardmetals with uniform microstructure comprising rounded WC grains undoped and doped with 0.2 wt% TaC was studied under uniaxial compressive loads in two ...temperature ranges of 300–500 K and 600–970 K. The amount of TaC added to WC–Co was below its solubility limit, so that the microstructure of the hardmetal doped with TaC did not contain grains of the second carbide phase (Ta,W)C of the order several microns in size. The creep activation energy in the medium-low temperature range (T = 300 … 500 K) is quite low and lies between 13 kJ/mol and 25 kJ/mol. The activation energy noticeably increases at higher temperatures and varies from 50 kJ/mol to 90 kJ/mol in the temperature range of 600–970 K. As a result of doping the WC-6%Co hardmetal with tantalum carbide the creep resistance significantly increases. In the temperature range of 600–900 K the doping leads to reducing creep rates by a factor of up to nine.
•The creep process of coarse-grain WC-6%Co hardmetals undoped and doped with 0.2 wt% TaC was studied.•The low-temperatures creep of the WC-6%Co hardmetals is characterized by low activation energy (13–25 kJ/mol).•In the temperature range of 600–900 K the TaC doping leads to reducing creep rates by a factor of up to nine.
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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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