The thermal behavior of green clay samples from the Arumetsa and Füzérradvány deposits (Hungary) ... more The thermal behavior of green clay samples from the Arumetsa and Füzérradvány deposits (Hungary) and the influence of two new types of Estonian oil shale (OS) ashes and cement bypass dust (clinker dust) additives on it were the objectives of this study. Thermal and thermo-dilatometric analysis methods were applied using a Setaram Setsys 1750 thermoanalyzer coupled with a Pfeiffer Omnistar spectrometer and a Setaram Setsys 1750 CS Evolution dilatometer. The kinetic parameters were calculated based on the differential isoconversional method of Friedman. The results of the thermal analysis of clays and blends indicated the emission of physically bound water at 200–250 °C. At temperatures from 200–250 °C to 550–600 °C the release of water is caused by oxidation of organic matter and dehydroxylation of different clay minerals like illite, illite-smectite, mica and kaolin. From blends, in addition, also from the decomposition of portlandite. The emission of CO2 at these temperatures was a...
The paper focuses on the corrosion behavior of Ni-/Fe-based self-fluxing alloy – WC-Co/Cr3C2-Ni c... more The paper focuses on the corrosion behavior of Ni-/Fe-based self-fluxing alloy – WC-Co/Cr3C2-Ni cermet composite coatings manufactured by high velocity oxy-fuel spraying (HVOFS). Microstructure and phase composition of the coatings were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The potentiodynamic tests were conducted in the 3.5 wt.% NaCl solutions under room temperature using a three-electrode cell setup (sample was applied as the working electrode, Pt as the counterelectrode, and Ag/AgCl – as the reference electrode) after 10 min and 24 h of immersion. Stainless steel AISI 316L was used as a reference. Tafel polarization plots were obtained, and corrosion potential Ecorr and corrosion current density icorr were determined. All the studied coatings exhibited more negative Ecorr values than the reference steel, both after short and long immersion time, whereas in the latter case, the difference in the corrosion potentials increased rema...
The present research focuses onto sliding wear of novel plasma transferred arc welded (PTAW) hard... more The present research focuses onto sliding wear of novel plasma transferred arc welded (PTAW) hardfacing with the stainless steel (DIN X3CrNiMo18-13-3) matrix, reinforced with WC/W2C, under the room and elevated temperature. The hardfacing was produced, applying the optimized set of parameters (current – 55 A, reciprocating speed – 1.0 mm/s, oscillation frequency – 0.6 Hz). The average reinforcement content was 29.3 ± 4.0 vol %. The reinforcement consisted of W2C and WC, while M7C3- and M23C6-type (M = Fe, Cr, Mo, W) carbides were the main phases in the matrix. Universal hardness and Young’s modulus were approximately 5.3 and 1.9 times higher, than those of the reference steel (DIN X2CrNiMo18-14-3). The sliding wear of the hardfacing was 4.9 times lower under 20 °C and 3.1 times lower under 300 °C, but 1.8 times higher under 500 °C than the wear of the reference steel. Galling was the wear mechanism of the hardfacing under 20 °C, scoring – under 300 °C and combination of scoring and ...
This study aimed to compare the X3CrNiMo17-13-3 stainless steel based plasma transferred arc (PTA... more This study aimed to compare the X3CrNiMo17-13-3 stainless steel based plasma transferred arc (PTA) cladded hardfacings, reinforced with the in-situ synthesized Cr and Ti carbides. Carbon black and either pure Cr, pure Ti, or TiO2 were utilized as reinforcement precursors (the respective hardfacings are further referred to as Cr+C, Ti+C and TiO2+C). The pre-placed mixtures of matrix and reinforcement precursor powders were remelted by the plasma transferred arc, applying the preliminarily optimized process parameters (95 A, 22 – 24 V, 0.2 mm/s). As a reference, the unreinforced stainless steel hardfacing was used. The carbide reinforcement was successfully in-situ synthesized in all the hardfacings. The Cr + C hardfacing exhibited the largest average hardness (556 ± 29 HV1), while the TiO2 + C hardfacing had the largest average Young’s modulus (156.3 ± 19.7 GPa). The Cr + C and Ti + C hardfacings demonstrated the 2.3 and 2.1 times higher resistance to abrasive wear than the reference...
The study is aimed at development, fabrication and preliminary mechanical characterization of ZrC... more The study is aimed at development, fabrication and preliminary mechanical characterization of ZrC-based composites for high temperature applications. The improvement in densification was achieved through introduction of second phase (molybdenum, zirconia, and titanium carbide). ZrC powder was produced by cost-effective in situ reactive sintering of nano-sized zirconium dioxide and graphite. The powder mixtures were pressureless sintered in vacuum at temperatures lower than 2000 C. The final densities of the composites varied between 96 – 98%. Materials obtained were quite hard (HV10 > 17 GPa) while relatively tough (IFT > 6.6 MPa m).
IOP Conference Series: Materials Science and Engineering, 2021
Good cementing properties, fast setting and strong thermal performance make calcium-aluminate a v... more Good cementing properties, fast setting and strong thermal performance make calcium-aluminate a valuable raw material for use in the production of different types of new refractory materials, e.g., heat conductive/storage materials. The main aim of the study was to determine thermal properties of novel Nb-slag based materials with different fillers, and to clarify optimal composition and technology. Process of preparation of studied materials was following: mixing of components, casting to moulds and hardening of materials. To estimate potential application areas, we studied the following thermal properties of CA-based materials: thermal behaviour, coefficient of thermal expansion (CTE) and conductivity. For this small cylindrical specimens were cut out from produced materials, and plates sized 300 × 300 mm were used for conductivity studies. Different compositions of CA-based materials, the hardening process, and the influence of mechanical activation on the strength were analyzed....
International Journal for Innovation Education and Research, 2018
The purpose of this study is to X-ray line-profile analysis of the effect of rapid Joule heating ... more The purpose of this study is to X-ray line-profile analysis of the effect of rapid Joule heating and severe plastic deformation concurrently on microstructure and properties evolution in polycrystalline austenitic Fe-balanced superalloy EP718E, which is Inconel 718 derivative. The microstructure of superalloy at different stages of processing was examined by X-ray diffraction, by scanning electron microscopy, and by energy dispersive spectrometry techniques. The mechanical properties of evolution were studied by means of tension and high cycle fatigue testings. The results of X-ray study show that the intensity, raw areas, and net areas were a step–by–step changed according to processing routines. Is shown that under shear stress the fcc-crystallites were deformed and the peaks parameters by 2-Theta scale changed partly.
High-velocity oxy-fuel sprayed, iron alloy-based powder coatings, reinforced with tungsten carbid... more High-velocity oxy-fuel sprayed, iron alloy-based powder coatings, reinforced with tungsten carbide–cobalt (WC–Co) and titanium carbide–nickel molybdenum (TiC–NiMo) cermet particles, are compared under high-temperature abrasive–erosive wear conditions. Both WC–Co and TiC–NiMo particles underwent fracture, as well as dissolution, during the spraying process, but in the case of WC–Co particles this process was remarkably less intensive. Under the low impact angle conditions, the WC–Co particle-reinforced coating exhibited 1.1 times lower wear than the TiC–NiMo particle-reinforced coating because of the larger amount of the reinforcement remaining. Under the normal impact angle conditions, the WC–Co particle-reinforced coating showed 1.2 times lower wear than the TiC–NiMo particle-reinforced coating because of the resulting larger size of the WC–Co reinforcement and a more ductile matrix.
Self-Propagating High-Temperature Synthesis (SHS) method was used to produce the light weight com... more Self-Propagating High-Temperature Synthesis (SHS) method was used to produce the light weight composites on boron carbide and boron nitride base by liquid condition of aluminum alloy binder. SHS method for recycling of composites with desintegration and attritin milling of powders was used too. Special wear tests in unlubricated sliding friction condition against steel, friction coefficient and hydroerosion in solution were performed. The wear mechanism, wear rate and the wear loss in solution during testing of different composites and phase's microhardness of composites were investigated and results are compared.
: This report introduces the synthesis of diamondlike superhard cubic boron-carbon nitride (c-BC ... more : This report introduces the synthesis of diamondlike superhard cubic boron-carbon nitride (c-BC 2 N) precipitations in multi-phase binder of lightweight boron carbide aluminum composite. Mentioned B-C-N-phase was designed via self-propagating high temperature synthesis and followed by heat treatment in nitrogen atmosphere under pressure at high temperatures. X-raydiffraction revealed that as result of solid state chemical reactions new refractory ceramic phases were formed which changed the mechanical properties of composites. As determined by nanoindentation the Vickers hardness of cubic boron-carbon-nitride precipitations was ~95 GPa and elastic modulus ~600 GPa like that of diamond. The maximum value of the experimentally determined thermal stability of BC 2 N up to 1450 °C and that is higher than that of diamond.
Short-bandgap group II-VI compound cadmium telluride is widely used for the infrared optics, radi... more Short-bandgap group II-VI compound cadmium telluride is widely used for the infrared optics, radiation detectors, and solar cells where p-type CdTe is needed. p-type conductivity of CdTe is mainly caused by the chlorine-based A-centers, and in part, by the less stable copperoxygen complexes. As a rule, CdTe films are recrystallized by the help of a cadmium chloride flux that saturates CdTe with chlorine. In chlorine-saturated CdTe A-centers are converted to isoelectronic complexes that cause resistivity increasement of CdTe up to 9 orders of magnitude. Excess copper and oxygen or group I elements as sodium also deteriorate the p-type conductivity of CdTe like excess chlorine. p-type conductivity of CdTe can be restored e.g. by the vacuum annealing which removes excess chlorine from the film. Unfortunately, treatment that betters ptype conductivity of the CdTe film degrades the junction of the superstrate configuration cells. In this work we investigate possibilities to prepare p-typ...
The thermal behavior of green clay samples from the Arumetsa and Füzérradvány deposits (Hungary) ... more The thermal behavior of green clay samples from the Arumetsa and Füzérradvány deposits (Hungary) and the influence of two new types of Estonian oil shale (OS) ashes and cement bypass dust (clinker dust) additives on it were the objectives of this study. Thermal and thermo-dilatometric analysis methods were applied using a Setaram Setsys 1750 thermoanalyzer coupled with a Pfeiffer Omnistar spectrometer and a Setaram Setsys 1750 CS Evolution dilatometer. The kinetic parameters were calculated based on the differential isoconversional method of Friedman. The results of the thermal analysis of clays and blends indicated the emission of physically bound water at 200–250 °C. At temperatures from 200–250 °C to 550–600 °C the release of water is caused by oxidation of organic matter and dehydroxylation of different clay minerals like illite, illite-smectite, mica and kaolin. From blends, in addition, also from the decomposition of portlandite. The emission of CO2 at these temperatures was a...
The paper focuses on the corrosion behavior of Ni-/Fe-based self-fluxing alloy – WC-Co/Cr3C2-Ni c... more The paper focuses on the corrosion behavior of Ni-/Fe-based self-fluxing alloy – WC-Co/Cr3C2-Ni cermet composite coatings manufactured by high velocity oxy-fuel spraying (HVOFS). Microstructure and phase composition of the coatings were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The potentiodynamic tests were conducted in the 3.5 wt.% NaCl solutions under room temperature using a three-electrode cell setup (sample was applied as the working electrode, Pt as the counterelectrode, and Ag/AgCl – as the reference electrode) after 10 min and 24 h of immersion. Stainless steel AISI 316L was used as a reference. Tafel polarization plots were obtained, and corrosion potential Ecorr and corrosion current density icorr were determined. All the studied coatings exhibited more negative Ecorr values than the reference steel, both after short and long immersion time, whereas in the latter case, the difference in the corrosion potentials increased rema...
The present research focuses onto sliding wear of novel plasma transferred arc welded (PTAW) hard... more The present research focuses onto sliding wear of novel plasma transferred arc welded (PTAW) hardfacing with the stainless steel (DIN X3CrNiMo18-13-3) matrix, reinforced with WC/W2C, under the room and elevated temperature. The hardfacing was produced, applying the optimized set of parameters (current – 55 A, reciprocating speed – 1.0 mm/s, oscillation frequency – 0.6 Hz). The average reinforcement content was 29.3 ± 4.0 vol %. The reinforcement consisted of W2C and WC, while M7C3- and M23C6-type (M = Fe, Cr, Mo, W) carbides were the main phases in the matrix. Universal hardness and Young’s modulus were approximately 5.3 and 1.9 times higher, than those of the reference steel (DIN X2CrNiMo18-14-3). The sliding wear of the hardfacing was 4.9 times lower under 20 °C and 3.1 times lower under 300 °C, but 1.8 times higher under 500 °C than the wear of the reference steel. Galling was the wear mechanism of the hardfacing under 20 °C, scoring – under 300 °C and combination of scoring and ...
This study aimed to compare the X3CrNiMo17-13-3 stainless steel based plasma transferred arc (PTA... more This study aimed to compare the X3CrNiMo17-13-3 stainless steel based plasma transferred arc (PTA) cladded hardfacings, reinforced with the in-situ synthesized Cr and Ti carbides. Carbon black and either pure Cr, pure Ti, or TiO2 were utilized as reinforcement precursors (the respective hardfacings are further referred to as Cr+C, Ti+C and TiO2+C). The pre-placed mixtures of matrix and reinforcement precursor powders were remelted by the plasma transferred arc, applying the preliminarily optimized process parameters (95 A, 22 – 24 V, 0.2 mm/s). As a reference, the unreinforced stainless steel hardfacing was used. The carbide reinforcement was successfully in-situ synthesized in all the hardfacings. The Cr + C hardfacing exhibited the largest average hardness (556 ± 29 HV1), while the TiO2 + C hardfacing had the largest average Young’s modulus (156.3 ± 19.7 GPa). The Cr + C and Ti + C hardfacings demonstrated the 2.3 and 2.1 times higher resistance to abrasive wear than the reference...
The study is aimed at development, fabrication and preliminary mechanical characterization of ZrC... more The study is aimed at development, fabrication and preliminary mechanical characterization of ZrC-based composites for high temperature applications. The improvement in densification was achieved through introduction of second phase (molybdenum, zirconia, and titanium carbide). ZrC powder was produced by cost-effective in situ reactive sintering of nano-sized zirconium dioxide and graphite. The powder mixtures were pressureless sintered in vacuum at temperatures lower than 2000 C. The final densities of the composites varied between 96 – 98%. Materials obtained were quite hard (HV10 > 17 GPa) while relatively tough (IFT > 6.6 MPa m).
IOP Conference Series: Materials Science and Engineering, 2021
Good cementing properties, fast setting and strong thermal performance make calcium-aluminate a v... more Good cementing properties, fast setting and strong thermal performance make calcium-aluminate a valuable raw material for use in the production of different types of new refractory materials, e.g., heat conductive/storage materials. The main aim of the study was to determine thermal properties of novel Nb-slag based materials with different fillers, and to clarify optimal composition and technology. Process of preparation of studied materials was following: mixing of components, casting to moulds and hardening of materials. To estimate potential application areas, we studied the following thermal properties of CA-based materials: thermal behaviour, coefficient of thermal expansion (CTE) and conductivity. For this small cylindrical specimens were cut out from produced materials, and plates sized 300 × 300 mm were used for conductivity studies. Different compositions of CA-based materials, the hardening process, and the influence of mechanical activation on the strength were analyzed....
International Journal for Innovation Education and Research, 2018
The purpose of this study is to X-ray line-profile analysis of the effect of rapid Joule heating ... more The purpose of this study is to X-ray line-profile analysis of the effect of rapid Joule heating and severe plastic deformation concurrently on microstructure and properties evolution in polycrystalline austenitic Fe-balanced superalloy EP718E, which is Inconel 718 derivative. The microstructure of superalloy at different stages of processing was examined by X-ray diffraction, by scanning electron microscopy, and by energy dispersive spectrometry techniques. The mechanical properties of evolution were studied by means of tension and high cycle fatigue testings. The results of X-ray study show that the intensity, raw areas, and net areas were a step–by–step changed according to processing routines. Is shown that under shear stress the fcc-crystallites were deformed and the peaks parameters by 2-Theta scale changed partly.
High-velocity oxy-fuel sprayed, iron alloy-based powder coatings, reinforced with tungsten carbid... more High-velocity oxy-fuel sprayed, iron alloy-based powder coatings, reinforced with tungsten carbide–cobalt (WC–Co) and titanium carbide–nickel molybdenum (TiC–NiMo) cermet particles, are compared under high-temperature abrasive–erosive wear conditions. Both WC–Co and TiC–NiMo particles underwent fracture, as well as dissolution, during the spraying process, but in the case of WC–Co particles this process was remarkably less intensive. Under the low impact angle conditions, the WC–Co particle-reinforced coating exhibited 1.1 times lower wear than the TiC–NiMo particle-reinforced coating because of the larger amount of the reinforcement remaining. Under the normal impact angle conditions, the WC–Co particle-reinforced coating showed 1.2 times lower wear than the TiC–NiMo particle-reinforced coating because of the resulting larger size of the WC–Co reinforcement and a more ductile matrix.
Self-Propagating High-Temperature Synthesis (SHS) method was used to produce the light weight com... more Self-Propagating High-Temperature Synthesis (SHS) method was used to produce the light weight composites on boron carbide and boron nitride base by liquid condition of aluminum alloy binder. SHS method for recycling of composites with desintegration and attritin milling of powders was used too. Special wear tests in unlubricated sliding friction condition against steel, friction coefficient and hydroerosion in solution were performed. The wear mechanism, wear rate and the wear loss in solution during testing of different composites and phase's microhardness of composites were investigated and results are compared.
: This report introduces the synthesis of diamondlike superhard cubic boron-carbon nitride (c-BC ... more : This report introduces the synthesis of diamondlike superhard cubic boron-carbon nitride (c-BC 2 N) precipitations in multi-phase binder of lightweight boron carbide aluminum composite. Mentioned B-C-N-phase was designed via self-propagating high temperature synthesis and followed by heat treatment in nitrogen atmosphere under pressure at high temperatures. X-raydiffraction revealed that as result of solid state chemical reactions new refractory ceramic phases were formed which changed the mechanical properties of composites. As determined by nanoindentation the Vickers hardness of cubic boron-carbon-nitride precipitations was ~95 GPa and elastic modulus ~600 GPa like that of diamond. The maximum value of the experimentally determined thermal stability of BC 2 N up to 1450 °C and that is higher than that of diamond.
Short-bandgap group II-VI compound cadmium telluride is widely used for the infrared optics, radi... more Short-bandgap group II-VI compound cadmium telluride is widely used for the infrared optics, radiation detectors, and solar cells where p-type CdTe is needed. p-type conductivity of CdTe is mainly caused by the chlorine-based A-centers, and in part, by the less stable copperoxygen complexes. As a rule, CdTe films are recrystallized by the help of a cadmium chloride flux that saturates CdTe with chlorine. In chlorine-saturated CdTe A-centers are converted to isoelectronic complexes that cause resistivity increasement of CdTe up to 9 orders of magnitude. Excess copper and oxygen or group I elements as sodium also deteriorate the p-type conductivity of CdTe like excess chlorine. p-type conductivity of CdTe can be restored e.g. by the vacuum annealing which removes excess chlorine from the film. Unfortunately, treatment that betters ptype conductivity of the CdTe film degrades the junction of the superstrate configuration cells. In this work we investigate possibilities to prepare p-typ...
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