Publikační činnost Katedry materiálového inženýrství / Publications of Department of Material Engineering (636)

Permanent URI for this collectionhttp://hdl.handle.net/10084/64755

Kolekce obsahuje bibliografické záznamy publikační činnosti (článků akademických pracovníků Katedry materiálového inženýrství (636) v časopisech registrovaných ve Web of Science od roku 2003 do roku 2022.
Do kolekce jsou zařazeny:
a) publikace, u nichž je v originálních dokumentech jako působiště autora (adresa) uvedena Vysoká škola báňská-Technická univerzita Ostrava (VŠB-TUO),
b) publikace, u nichž v originálních dokumentech není v adrese VŠB-TUO uvedena, ale autoři prokazatelně v době jejich zpracování a uveřejnění působili na VŠB-TUO.

Bibliografické záznamy byly původně vytvořeny v kolekci Publikační činnost akademických pracovníků VŠB-TUO, která sleduje publikování akademických pracovníků od roku 1990.

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Now showing 1 - 20 out of 140 results

Stochastic evaluation of cutting tool load and surface quality during milling of HPL
(MDPI, 2022) Frydrýšek, Karel; Skoupý, Ondřej; Mrkvica, Ivan; Slaninková, Aneta; Kratochvíl, Jiří; Jurga, Tibor; Vlk, Miroslav; Krpec, Pavel; Madeja, Roman; Havlíček, Miroslav; Stančeková, Dana; Pometlová, Jana; Hlinka, Josef
The topic of the article concerns the mechanics of machining plastics and their machined surface. This article deals with measurements and their stochastic (probabilistic) evaluation of the force and moment loading of the machine tools and workpiece. It also deals with the quality of the machined surface in relation to its surface roughness and surface integrity. Measurements were made under different cutting conditions on a CNC milling machine using a newly designed cutter with straight teeth. The statistical evaluation is presented by bounded histograms and basic statistical characteristics that give a realistic idea of the machining process. The practical focus of the experiments is on the milling of HPL (high-pressure plastic-laminate composite material). The listed procedures can also be applied to other materials and machining methods, and can be used for numerical modelling, setting the optimum parameters of machining technology, or for the design of cutting tools. Numerical modelling and other solution options are also mentioned. We have not yet found detailed information in the literature about the milling of HPL material, and our results are therefore new and necessary.
Phase transformation after heat treatment of Cr-Ni stainless steel powder for 3D printing
(MDPI, 2022) Čech Barabaszová, Karla; Slíva, Aleš; Kratošová, Gabriela; Holešová, Sylva; Volodarskaja, Anastasia; Cetinkaya, Tugrul; Brožová, Silvie; Kozubek, Libor; Simha Martynková, Gražyna
Today, Ni-Cr steel is used for advanced applications in the high-temperature and electrical industries, medical equipment, food industry, agriculture and is applied in food and beverage packaging and kitchenware, automotive or mesh. A study of input steel powder from various stages of the recycling process intended for 3D printing was conducted. In addition to the precise evaluation of the morphology, particle size and composition of the powders used for laser 3D printing, special testing and evaluation of the heat-treated powders were carried out. Heat treatment up to 950 degrees C in an air atmosphere revealed the properties of powders that can appear during laser sintering. The powders in the oxidizing atmosphere change the phase composition and the original FeNiCr stainless steel changes to a two-phase system of Fe3Ni and Cr2O3, as evaluated by X-ray diffraction analysis. Observation of the morphology showed the separation of the oxidic phase in the sense of a brittle shell. The inner part of the powder particle is a porous compact core. The particle size is generally reduced due to the peeling of the oxide shell. This effect can be critical to 3D printing processing, causing defects on the printed parts, as well as reducing the usability of the precursor powder and can also change the properties of the printed part.
Hot deformation behavior of non-alloyed carbon steels
(MDPI, 2022) Kawulok, Petr; Opěla, Petr; Schindler, Ivo; Kawulok, Rostislav; Rusz, Stanislav; Sauer, Michal; Konečná, Kateřina
The hot deformation behavior of selected non-alloyed carbon steels was investigated by isothermal continuous uniaxial compression tests. Based on the analysis of experimentally determined flow stress curves, material constants suitable for predicting peak flow stress sigma(p), peak strain epsilon(p) and critical strain epsilon(crDRX) necessary to induce dynamic recrystallization and the corresponding critical flow stresses sigma(crDRX) were determined. The validity of the predicted critical strains epsilon(crDRX) was then experimentally verified. Fine dynamically recrystallized grains, which formed at the boundaries of the original austenitic grains, were detected in the microstructure of additionally deformed specimens from low-carbon investigated steels. Furthermore, equations describing with perfect accuracy a simple linear dependence of the critical strain epsilon(crDRX) on peak strain epsilon(p) were derived for all investigated steels. The determined hot deformation activation energy Q decreased with increasing carbon content (also with increasing carbon equivalent value) in all investigated steels. A logarithmic equation described this dependency with reasonable accuracy. Individual flow stress curves of the investigated steels were mathematically described using the Cingara and McQueen model, while the predicted flow stresses showed excellent accuracy, especially in the strains ranging from 0 to epsilon(p).
Complex material and surface analysis of anterolateral distal tibial plate of 1.4441 steel
(MDPI, 2022) Hlinka, Josef; Dostálová, Kamila; Peterek Dědková, Kateřina; Madeja, Roman; Frydrýšek, Karel; Koutecký, Jan; Sova, Pavel; Douglas, Timothy E. L.
Nickel-based austenitic stainless steels are still common for manufacture of implants intended for acute hard tissue reinforcement or stabilization, but the risk of negative reactions due to soluble nickel-rich corrosion products must be considered seriously. Corrosion processes may even be accelerated by the evolution of microstructure caused by excessive heat during machining, etc. Therefore, this study also deals with the investigation of microstructure and microhardness changes near the threaded holes of the anterolateral distal tibial plate containing approx. 14wt.% Ni by composition. There were only insignificant changes of microhardness, grain size, or microstructure orientation found close to the area of machining. In addition, wettability measurements of surface energy demonstrated only minor differences for bulk material and areas close to machining. The cyclic potentiodynamic polarization tests were performed in isotonic physiological solution. The first cycle was used for the determination of corrosion characteristics of the implant after chemical passivation, the second cycle was used to simulate real material behavior under the condition of previous surface damage by excessive pitting corrosion occurring during previous polarization. It was found that the damaged and spontaneously repassived surface showed a three-time higher standard corrosion rate than the "as received" chemically passivated surface. One may conclude that previous surface damage may decrease the lifetime of the implant significantly and increase the amount of nickel-based corrosion products distributed into surrounding tissues.
Inhibition of steel corrosion with imidazolium-based compounds – Experimental and theoretical study
(Elsevier, 2021) Legut, Dominik; Kadzielawa, Andrzej Piotr; Pánek, Petr; Marková, Kristýna; Váňová, Petra; Konečná, Kateřina; Langová, Šárka
This work aims to investigate the corrosion inhibition of the mild steel in the 1 M HCl solution by 1-octyl-3-methylimidazolium hydrogen sulphate 1-butyl-3-methylimidazolium hydrogen sulphate, and 1-octyl-3-methylimidazolium chloride, using electrochemical, weight loss, and surface analysis methods as well as the full quantummechanical treatment. Polarization measurements prove that studied compounds are mixed-type inhibitors with a predominantly anodic reaction. The inhibition efficiency obtained from the polarization curves is about 80-92% for all of the 1-octyl-3-methylimidazolium salts with a concentration higher than 0.005 mol/l, while it is much lower for 1-butyl-3-methylimidazolium hydrogen sulphate. The values measured in the weight loss experiments (after seven days) are to some extent higher (reaching up to 98% efficiency). Furthermore, we have shown that the influence of the alkyl chain length on the inhibition efficiency is much larger than that of the anion type. Furthermore, we obtain a realistic model of a single molecule on iron surface Fe(110) by applying the Density Functional Theory calculations. We use the state-of-the-art computational approach, including the meta-GGA strongly-constrained and appropriately normed semilocal density functional to model the electronic structure properties of both free and bounded-to-surface molecules of 1-butyl-, 1-hexyl-, and 1-octyl-3-methylimizadolium bromide, chloride, and hydrogen sulphate. From the calculations we extract, the HOMO/LUMO gap, hardness, electronegativity, and charge transfer of electrons from/to molecules-in-question. It supports the experimental findings and explains the influence of the alkyl chain length and the functional group on the inhibition process.
The effect of rare earth metals alloying on the internal quality of industrially produced heavy steel forgings
(MDPI, 2021) Jonšta, Petr; Jonšta, Zdeněk; Brožová, Silvie; Ingaldi, Manuela; Pietraszek, Jacek; Klimecka-Tatar, Dorota
The paper presented the findings obtained by industrial research and experimental development on the use of rare earth metals (REMs) in the production of heavy steel ingots and their impact on the internal quality of the 42CrMo4 grade steel forging. REMs alloying was carried out after vacuuming the steel. A relatively large melting loss of cerium (about 50%) and its further decrease in casting due to reoxidation were observed. Refinement of structure and better mechanical properties of forged bar containing about 0.02 wt.% of Ce compared to that of the standard production were not achieved. The wind power shaft with content of about 0.06 wt.% of Ce showed high amount of REM inclusions, which were locally chained, and in some cases, initiated cracks. Four stoichiometrically different types of REM inclusions were detected in forgings, namely (La-Ce)(2)O2S + (La-Ce)O-2 + SiO2 (minority); oxygen, phosphorus, arsenic, and antimony bound to lanthanum and cerium probably bonded with iron oxides La + Ce, MgO, Al2O3 a SiO2; (La-Ce)(2)O2S, FeO, SiO2, and CaO or CaS.
Effect of additive for preparation of reduced-porosity ceramic layer on Ti-6Al-4 V alloy for orthopaedic and trauma implants
(Elsevier, 2021) Gabor, Roman; Cvrček, Ladislav; Causidu, Simona; Drobíková, Klára; Večeř, Marek; Mamulová Kutláková, Kateřina; Buřil, Matěj; Hlinka, Josef; Seidlerová, Jana
The micro-arc oxidation (MAO) method using a pulsed unipolar source was used to prepare coatings suitable for orthopaedic and trauma implants. The application of the MAO pilot plant containing the alkaline electrolyte Na2SiO3 center dot 9H(2)O, NaOH and glycerol additive was studied on a Ti-6Al-4 V alloy while focusing on reducing the pore size and improving the tribological and corrosion properties. The effects of stress, discharge time, duty cycle and the effect of the additive on the morphology of the coating, coating thickness, pore size, chemical and phase composition, wear resistance and corrosion resistance were described. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) methods equipped with X-ray energy dispersive spectroscopy (EDX), pin-on-disc, tribometer, potentiodynamic polarisation were used to characterise the coatings. Pulsation of the unipolar source and microdischarge intensity of voltage influenced the growth of the sample surface layer, surface morphology and silicon content in the analysed coating. A significant difference in pore sizes was confirmed when a glycerol-containing electrolyte was applied. The pore size distribution influenced the wear resistance and stability of the coefficient of friction. The corrosion behaviour of the prepared coatings on Ti6Al-4 V alloy was studied in physiological solutions and evaluated by using potentiodynamic curves. Corrosion resistance was evaluated based on the corrosion potentials, current densities, and polarisation resistance; a significant improvement in corrosion resistance was observed in the coatings prepared in the electrolyte with added glycerol and the presence of smaller pores.
Basic microstructural characterization of second phases in homogeneous weld joint made of X6CrNiNbN25-20 steel after long-term exposure time at 973 K
(ASME, 2021) Řehořek, Jakub; Namburi, Hygreeva Kiran
New blocks of fossil fuel power plants designed for steam temperatures above 873 K require advanced stainless steels as material for superheater or reheater systems. Weld joints are critical parts in fossil power units. Great attention is paid to the exploitation of new steel grades with higher material properties. In the austenitic steels family, the superior grade is undoubtedly HR3C steel (X6CrNiNbN25-20). A detailed knowledge on stability and microstructure composition during thermal exposure of the weld joints made from HR3C is necessary in order to use them in fossil fuel power plants with ultrasupercritical (USC) and new advanced ultrasupercritical (A-USC) steam parameters. The aim of the paper is to identify critical minor phases in HR3C steel, which allow acceleration of creep damage. The sigma-phase and rough carbides M23C6 type is considered as such a phases in this steel. In this study, the sigma-phase is identified and studied in more detail in relation to the development of creep damage at 973 K. Experimental material of the homogeneous HR3C weld joints in two states: in the as-welded state (AW) and after the postweld heat treatment (PWHT). Weld joints were manufactured by orbital welding using the gas tungsten arc welding (GTAW) method, heat input Q(s) = 1600 J/mm, interpass 423 K, three beads. Nickel-base alloy UTP A6170 Co (equivalent to Thermanit 617) was used as a filler material. The PWHT was carried out at the temperature of 1503 K for 15 min. Stress rupture tests were performed on the cross-weld (CW) joints of tubes o 38 x 6.3 mm at 973 K with times to rupture up to nearly 22,000 h. The polished surface of the longitudinal sections was subjected to color etching in Murakami (30 g K-3(Fe(CN)(6)), 30 g KOH, 60 ml H2O) in order to highlight the sigma-phase. Several microscopic techniques were used for the study. The results were supplemented by creep, grain size, and microhardness data hardness vickers (HV) 0.5. The PWHT specimens exhibited an average sigma-phase size of approximately 5 mu m as well as AW specimens in specimens with short time to rupture (t(r)). However, t(r) such as 20,000 h, the average sigma-phase size already reached dangerous border 10 mu m. The AW specimens as opposed to the PWHT specimens did not show a noticeable growth of austenitic grains in the heat-affected zone (HAZ). In specimens after PWHT, the average grain size in HAZ was more than twice that of the body material (BM). It is worth noting that creep ductility values of specimens in the state after PWHT are very low, which is the result of coarse-grained structure in the HAZ and accelerated precipitation of sigma-phase particles along grain boundaries during creep at 973 K.
Case study on fire resistance of sandwiches for means of transport
(MDPI, 2021) Koštial, Pavol; Koštialová Jančíková, Zora; Frischer, Robert
These days there are undeniably unique materials that, however, must also meet demanding safety requirements. In the case of vehicles, these are undoubtedly excellent fire protection characteristics. The aim of the work is to experimentally verify the proposed material compositions for long-term heat loads and the effect of thickness, the number of laminating layers (prepregs) as well as structures with different types of cores (primarily honeycomb made of Nomex paper type T722 of different densities, aluminum honeycomb and PET foam) and composite coating based on a glass-reinforced phenolic matrix. The selected materials are suitable candidates for intelligent sandwich structures, usable especially for interior cladding applications in the industry for the production of means of public transport (e.g., train units, trams, buses, hybrid vehicles).
High–temperature interaction of molten Fe–C–O–Cr alloys with corundum
(Elsevier, 2021) Řeháčková, Lenka; Novák, Vlastimil; Váňová, Petra; Matýsek, Dalibor; Konečná, Kateřina; Smetana, Bedřich; Dobrovská, Jana
The interaction of Fe-C-O-Cr alloys varying in chromium (0.924-4.760 wt%) and carbon (0.042-1.378 wt%) content with a ceramic substrate having a high content of Al2O3 was studied by experimental wettability tests up to 1600 degrees C. The degree of interaction was assessed based on changes in contact angles (wetting angles) between the above systems, and through Energy Dispersive X-Ray (EDX), X-Ray Diffraction (XRD) analyses and Scanning Electron Microscopy (SEM). The increasing trend of wetting angles with increasing content of chromium and carbon was found. The results of the analyzes confirmed the effect of carbon (>0.1 wt%) contained in the alloys on the structural changes in substrate surface within the area under the alloy. The original corundum phase was replaced by new ones (hibonite, grossite, larnite), of which hibonite was present to the highest degree. Furthermore, in the case of low carbon alloy (0.042 wt% C), hibonite was not detected on the substrate surface contrary to chromium-doped corundum.
Effects of austenitization temperature and pre-deformation on CCT diagrams of 23MnNiCrMo5-3 steel
(MDPI, 2020) Schindler, Ivo; Kawulok, Rostislav; Opěla, Petr; Kawulok, Petr; Rusz, Stanislav; Sojka, Jaroslav; Sauer, Michal; Navrátil, Horymír; Pindor, Lukáš
The combined effect of deformation temperature and strain value on the continuous cooling transformation (CCT) diagram of low-alloy steel with 0.23% C, 1.17% Mn, 0.79% Ni, 0.44% Cr, and 0.22% Mo was studied. The deformation temperature (identical to the austenitization temperature) was in the range suitable for the wire rolling mill. The applied compressive deformation corresponded to the true strain values in an unusually wide range. Based on the dilatometric tests and metallographic analyses, a total of five different CCT diagrams were constructed. Pre-deformation corresponding to the true strain of 0.35 or even 1.0 had no clear effect on the austenite decomposition kinetics at the austenitization temperature of 880 degrees C. During the long-lasting cooling, recrystallization and probably coarsening of the new austenitic grains occurred, which almost eliminated the influence of pre-deformation on the temperatures of the diffusion-controlled phase transformations. Decreasing the deformation temperature to 830 degrees C led to the significant acceleration of the austenite -> ferrite and austenite -> pearlite transformations due to the applied strain of 1.0 only in the region of the cooling rate between 3 and 35 degrees C center dot s(-1). The kinetics of the bainitic or martensitic transformation remained practically unaffected by the pre-deformation. The acceleration of the diffusion-controlled phase transformations resulted from the formation of an austenitic microstructure with a mean grain size of about 4 mu m. As the analysis of the stress-strain curves showed, the grain refinement was carried out by dynamic and metadynamic recrystallization. At low cooling rates, the effect of plastic deformation on the kinetics of phase transformations was indistinct.
Analysis of welded joint properties on an AISI316L stainless steel tube manufactured by SLM technology
(MDPI, 2020) Mohyla, Petr; Hajnyš, Jiří; Sternadelová, Kristýna; Krejčí, Lucie; Pagáč, Marek; Konečná, Kateřina; Krpec, Pavel
This work is focused on the analysis of the influence of welding on the properties and microstructure of the AISI316L stainless steel tube produced by 3D printing, specifically the SLM (Selective Laser Melting) method. Both non-destructive and destructive tests, including metallographic and fractographic analyses, were performed within the experiment. Microstructure analysis shows that the initial texture of the 3D print disappears toward the fuse boundary. It is evident that high temperature during welding has a positive effect on microstructure. Material failure occurred in the base material near the heat affected zone (HAZ). The results obtained show the fundamental influence of SLM technology in terms of material defects, on the properties of welded joints.
Influence of steel structure on machinability by abrasive water jet
(MDPI, 2020) Hlaváčová, Irena M.; Sadílek, Marek; Váňová, Petra; Szumilo, Stefan; Tyč, Martin
Although the abrasive waterjet (AWJ) has been widely used for steel cutting for decades and there are hundreds of research papers or even books dealing with this technology, relatively little is known about the relation between the steel microstructure and the AWJ cutting efficiency. The steel microstructure can be significantly affected by heat treatment. Three different steel grades, carbon steel C45, micro-alloyed steel 37MnSi5 and low-alloy steel 30CrV9, were subjected to four different types of heat treatment: normalization annealing, soft annealing, quenching and quenching followed by tempering. Then, they were cut by an abrasive water jet, while identical cutting parameters were applied. The relations between the mechanical characteristics of heat-treated steels and the surface roughness parameters Ra, Rz and RSm were studied. A comparison of changes in the surface roughness parameters and Young modulus variation led to the conclusion that the modulus was not significantly responsible for the surface roughness. The changes of RSm did not prove any correlation to either the mechanical characteristics or the visible microstructure dimensions. The homogeneity of the steel microstructure appeared to be the most important factor for the cutting quality; the higher the difference in the hardness of the structural components in the inhomogeneous microstructure was, the higher were the roughness values. A more complex measurement and critical evaluation of the declination angle measurement compared to the surface roughness measurement are planned in future research.
Hot deformation behaviour of Mn-Cr-Mo low-alloy steel in various phase regions
(MDPI, 2020) Schindler, Ivo; Opěla, Petr; Kawulok, Petr; Sojka, Jaroslav; Konečná, Kateřina; Rusz, Stanislav; Kawulok, Rostislav; Sauer, Michal; Turoňová, Petra
The deformation behaviour of a coarse-grained as-cast medium-carbon steel, alloyed with 1.2% Mn, 0.8% Cr and 0.2% Mo, was studied by uniaxial compression tests for the strain rates of 0.02 s(-1)-20 s(-1)in the unusually wide range of temperatures (650-1280 degrees C), i.e., in various phase regions including the region with predominant bainite content (up to the temperature of 757 degrees C). At temperatures above 820 degrees C, the structure was fully austenitic. The hot deformation activation energies of 648 kJ center dot mol(-1)and 364 kJ center dot mol(-1)have been calculated for the temperatures <= 770 degrees C and >= 770 degrees C, respectively. This corresponds to the significant increase of flow stress in the low-temperature bainitic region. Unique information on the hot deformation behaviour of bainite was obtained. The shape of the stress-strain curves was influenced by the dynamic recrystallization of ferrite or austenite. Dynamically recrystallized austenitic grains were strongly coarsened with decreasing strain rate and growing temperature. For the austenitic region, the relationship between the peak strain and the Zener-Hollomon parameter has been derived, and the phenomenological constitutive model describing the flow stress depending on temperature, true strain rate and true strain was developed. The model can be used to predict the forming forces in the seamless tubes production of the given steel.
Complex corrosion properties of AISI 316L steel prepared by 3D printing technology for possible implant applications
(MDPI, 2020) Hlinka, Josef; Kraus, Martin; Hajnyš, Jiří; Pagáč, Marek; Petrů, Jana; Brytan, Zbigniew; Tański, Tomasz
This paper deals with the investigation of complex corrosion properties of 3D printed AISI 316L steel and the influence of additional heat treatment on the resulting corrosion and mechanical parameters. There was an isotonic solution used for the simulation of the human body and a diluted sulfuric acid solution for the study of intergranular corrosion damage of the tested samples. There were significant microstructural changes found for each type of heat treatment at 650 and 1050 degrees C, which resulted in different corrosion properties of the tested samples. There were changes of corrosion potential, corrosion rate and polarization resistance found by the potentiodynamic polarization method. With regard to these results, the most appropriate heat treatment can be applied to applications with intended use in medicine.
Case study of chosen sandwich-structured composite materials for means of transport
(MDPI, 2020) Koštial, Pavol; Koštialová Jančíková, Zora; Ružiak, Ivan; Gajtanska, Milada
Modern means of transport increasingly utilize sandwich constructions. Among other things, the reasons for such state of affairs include the reduced weight of means of transport, and through this, better fuel economy as well as price. This work is dedicated to a systematic experimental study of the influence of various materials and sandwich designs on their mechanical properties. In the framework of experiments, sandwich-structured composites were exposed to two types of stressing: static as well as impact stressing. The testing of prepared samples was performed according to ASTM C-393 Standard, dealing specifically with the bending behavior of sandwich composite constructions and impact testing under the scope of ISO 6603-2 Standard test. In this article we deal with static and impact testing of the eight types of core materials, two types of coatings, two types of surface finishes, and two types of resins with a special emphasis on their use in constructions of some exterior or interior components of transport means.
Effect of severe plastic deformation on mechanical and fatigue behaviour of medium-c sheet steel
(Technical Faculty, Bor, 2020) Rusz, Stanislav; Hilšer, Ondřej; Ochodek, Vladislav; Čížek, Lubomír; Kraus, Martin; Mareš, Vratislav; Grajcar, A.; Švec, Jiří
The DRECE method belongs to the severe plastic deformation (SPD) processes used for the refinement of sheet metal elements. A forming device used in this method is currently being installed in the workplace in the Centre of Advanced Innovation Technologies, VSB Technical University of Ostrava. In the present work the structural characteristics and fracture morphology of Ck55 carbon steel after the application of the DRECE method with a forming tool angle of 118 degrees are presented. The microstructure results are linked to selected mechanical properties. The tensile, hardness, and fatigue tests are performed. The methodology of non-destructive residual stresses measurement in the carbon steel after the extrusion and application of tensile tests on small samples are important for their use in technical practice. The paper presents the original results of selected properties after the application of the DRECE method on Ck55 steel, which will be used in the future to assess the application of the DRECE method and to determine other directions of the processing of ferrous alloys and steels.
Surface and interfacial properties of Fe-C-O-Cr alloys in contact with alumina
(Technical Faculty, Bor, 2020) Novák, Vlastimil; Řeháčková, Lenka; Váňová, Petra; Smetana, Bedřich; Konečná, Kateřina; Drozdová, Ľubomíra; Rosypalová, Silvie
In this paper, temperature and concentration dependencies on density and surface tension of liquid Fe-C-O-Cr alloys (1.93 - 4.80 wt.% Cr) were investigated in high-temperature resistance observation furnace by a sessile drop method during heating from liquidus temperature to 1600 degrees C. The interfacial characteristics (interfacial tension, wetting angle, work of adhesion, and spreading coefficient) of liquid alloy/alumina system were also determined depending on temperature. The effect of temperature and chromium content on surface and interfacial properties was proven in case of all examined alloys. Based on the fact that the content of surface-active elements such as oxygen (up to 195 ppm) and sulfur (up to 545 ppm) was higher; the influence of activities of both mentioned elements on surface tension of alloy samples was assessed. Particular attention was paid to the dependence of the surface tension temperature coefficient on oxygen and sulfur activity.
Complex corrosion properties of AISI 316L steel prepared by 3D printing technology for possible implant applications
(MDPI, 2020) Hlinka, Josef; Kraus, Martin; Hajnyš, Jiří; Pagáč, Marek; Petrů, Jana; Brytan, Zbigniew; Tański, Tomasz
This paper deals with the investigation of complex corrosion properties of 3D printed AISI 316L steel and the influence of additional heat treatment on the resulting corrosion and mechanical parameters. There was an isotonic solution used for the simulation of the human body and a diluted sulfuric acid solution for the study of intergranular corrosion damage of the tested samples. There were significant microstructural changes found for each type of heat treatment at 650 and 1050 degrees C, which resulted in different corrosion properties of the tested samples. There were changes of corrosion potential, corrosion rate and polarization resistance found by the potentiodynamic polarization method. With regard to these results, the most appropriate heat treatment can be applied to applications with intended use in medicine.
Thermal aging of Menzolit BMC 3100
(Hindawi, 2020) Koštial, Pavol; Koštialová Jančíková, Zora; Krejcar, Ondřej; Kuča, Kamil; Fadeyi, Oluwaseun; Orogun, Adebola; Frischer, Robert
This paper deals with the influence of thermal aging on physical properties of a composite material, Menzolit BMC 3100. First, we present a number of analysis, FTIR (infrared spectroscopy), DSC (differential scanning calorimetry), TMA (thermomechanical analysis), TGA (thermogravimetric analysis), and HDT (heat deflection temperature), to understand the material performance under heat, and then, we carry out a test of toughness and strength using Charpy impact strength and Brinell hardness. Finally, we present optical surface analysis of the material under investigation by carrying out aging analysis at increments from room temperature up to 300 degrees C. It was observed that above 200 degrees C, the material begins to degrade at the surface, especially its organic component, polyester resin. This type of degradation has a negative impact on a variety of its physical properties. Exposure to temperatures above 200 degrees C reduces the material's hardness, toughness, and shape stability, likewise, material degradation was found to increase with higher thermal loads almost linearly for all the observed properties.

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