The paper presents influence of the type of abrasive media on the operating parameters of the surface of components made of composite ceramic-glass, coated with a layer of antiferromagnetic. The research presents the possibilities offered by the use of resin bonded media with different intensities abrasive, understood as different content of abrasive grains. There were used Rollwasch smoothing media PB series – resin plastic media. Media were cone-shaped, with different abrasive properties (10%, 50% and 85%). The process was carried out by using chemical compounds - liquid supportive ME series L100 A22 / NF. Attention has also been given to the relation between the properties of abrasive media and surfaces that can be obtained after polishing with porcelain media and deburring with resin bonded media. As the output surface used the disc of hard drive. Then, to analysis of the possibility various kinds of abrasive media in vibratory finishing the analysis of surface texture with an optical profilometer Talysurf CCI Lite - Taylor Hobson were done. As a result of the effects polishing and deburring using vibratory finishing were compared.
The paper is focused on the evaluation of the course of Cr2O3 reduction from slag to alloyed steel under laboratory conditions. The experiments were aimed at the evaluation of increase in the chromium content in the melt together with the studying the behaviour of Cr2O3 and the mechanism of reduction by means of four reducing agents. Anthracite, ferrosilicon, aluminium and mixture of anthracite and ferrosilicon belong among the selected reducing agents. The experimental melts were focused on the proposal of a theoretical calculation of the consumption of selected reducing agents, study of reduction under laboratory conditions at application of alloyed steel with content of chromium of 12.16 wt. %, temperatures of 1600 °C and 1650 °C, together with the change of amount of reducing agents and reduction time. The results indicated in the paper constitute basic information on the possibilities of Cr2O3 reduction from slag; they will be used for verification of results in the pilot plant and operation experiments which will simulate operating conditions in the electric arc furnace.
Formation of dissimilar weld joints of light metals and alloys including Al-Ti joints is interesting mainly due to demands on the weight reduction and corrosion resistance of components and structures in automotive, aircraft, aeronautic and other industries. Joining of Al-Ti alloys represents quite difficult problem. Generally, the fusion welding of these materials can lead to the development of different metastable phases and formation of brittle intermetallic compounds. The paper deals with numerical simulation of the laser welding-brazing process of titanium Grade 2 and EN AW 5083 aluminum alloy sheets using the 5087 aluminum filler wire. Simulation model for welding-brazing of testing samples with the dimensions of 50 × 100 × 2 mm was developed in order to perform numerical experiments applying variable welding parameters and to design proper combination of these parameters for formation of sound Al-Ti welded-brazed joints. Thermal properties of welded materials in the dependence on temperature were computed using JMatPro software. The conical model of the heat source was exploited for description of the heat input to the weld due to the moving laser beam source. The sample cooling by convection and radiation to the surrounding air and shielding argon gas was taken into account. Developed simulation model was verified by comparison of obtained results of numerical simulation with the temperatures measured during real experiments of laser welding-brazing by the TruDisk 4002 disk laser.
Low alloyed high-grade chrome-molybdenum ferritic steel was investigated from the point of views of magnetic properties in dependence on heat and mechanical treatment. This steel can be used as components of magnetic circuits or some parts in electrical equipment. The basic information on structure and phase composition was obtained by optical and scanning electron microscopy, X-Ray Powder Diffraction and Mössbauer Spectroscopy. The temperature stability of the material was proved by measurements of temperature dependences of magnetic moment. The magnetic parameters were obtained by measuring of magnetic hysteresis loops in dependence on saturation field and their frequencies. The results are discussed from the point of view of possible applications as a magnetic material in the very extremely environment, where high mechanical stresses and elevated temperatures can occur.
One of the most techniques employed to obtain drilling tools used in oil and mining fields is Hardfacing. In this work, wear resistance and microstructural properties of WC-Ni Hardfacing with Ni-Cr as interlayer are investigated. Oxyacetylene brazing technique is employed to deposit WC-Ni upon SAE 1021 steel substrate. Whereas, the interlayer Ni-Cr is obtained by flame thermal spray process. The influence of the interlayer on the mechanical properties of the interfaces is carried out through Micro-hardness profiles. Furthermore, the decarburization amount of the WC particles is influenced by their location in the hardfacing (near or far from the substrate) and related to the cooling rate and the work temperature. Wear experiment is performed at room temperature with dry sliding pin-on-disk experiment under 2N, 5N and 8N loads respectively. It indicates that the higher the load applied is, the lower the coefficient of friction, which may be related to the WC decarburization and to the oxides formed during the wear test.
Dispersed particles embedded in the metal, improve the mechanical properties, particularly wear resistance. Introduction of the metal particles in a controlled and their distribution is difficult because of the density difference and the metal particles introduced. This article provides a method for the introduction of particles in the volume of metal, it contains a proposed strengthening technique described experiment course. During the experiment, the volume-reinforced castings from wear-resistant steel, the results of studies of the microstructure by optical and scanning electron microscopy, and mechanical tests of prototypes have been obtained.
The investigation has been undertaken to develop and study the upsetting characteristics of iron-based sintered porous components by using elemental powders through powder metallurgical techniques. The paper presents experimental results of forming Fe-based sintered porous samples and upsetting it by two methods. The first method involves upsetting between two flat plates (anvils). The second method is based on the deformation of the material in closed-die. The study compares the graphs of variation of the force vs. displacement. The aim of the article is to compare the experimental characteristics of upsetting process of samples with different porosities. Metallic porous structure was obtained as a result of sintering processes Fe-based powders mixtures with addition of copper catalyst and Fe (III) oxide as a space holder. The sintering was proceeded at the temperature of 1130OC and 50 min. long, in dissociated ammonia protective gas. Some samples were sintered with addition of powdered activated carbon to increase its porosity properties and change chemical composition.
C45 steel (CSN 41 2050) is a plain carbon steel for quenching and tempering, widely used in mechanical engineering and automotive components due to its low cost and good combination of mechanical properties. This article is focused on investigation of plasma nitriding, tenifer and nitriding/ manganese phosphating duplex treatment to increase the wear resistance of this steel. After quenching and tempering, the plasma nitriding process was carried out under different gas ratio during 15 hours, later a thin coating of manganese phosphating was applied on nitrided layers. Tenifer technology including nitrocarburizing in salt bath and oxidation process in salt bath was performed. The wear test "pin on disc" was used to evaluate the coefficient of friction and wear rate using the tribolab BRUKER UMT-3. The hardness test, metallographical documentation and chemical analysing were realized to determine the formation of nitrided and nitrocarburized layers and coating. The analysis results verify ability of plasma nitriding, nitrocarburizing and phosphate manganese to improve the hardness, wear resistance and friction.
This paper is focused on the creation of eccentricity in rolling of seamless pipe in Železiarne Podbrezová a.s. Eccentricity influences the geometric quality of the rolling seamless tubes, which are used as a finished product or semifinished product for further processing by drawing. For quality analysis by numerical simulation it is necessary to know the real state of eccentricity in the rolling mill from piercing press to stretch-reducing mill. The article deals with the issue of the primary eccentricity in the piercing press, i.e. non-coaxial movement of piercing mandrel in relation to the axis of the die of piercing press. It was used for numerical simulation of piercing in a variety of input conditions and was using for a number of different states of billet before entering the piercing press. The first case used in the simulation is uneven heating of the billet in the rotary hearth furnace, which can result in non-coaxiality of the mandrel movement due to the different flow stress in cross-section. Another case is wrongly calibrated billet, which can be described as poorly formed edge in calibrating duo and non-coaxial centered in the cylindrical die of the piercing press. One of the cases is the uneven cutting surface, which can give rise to the eccentricity and can also occur later in next technology of production seamless tubes.
The manufacture of press-formed parts often involves deep-drawing operations. Deep drawing, however, can be deemed an industrial branch in its own right. Today, many experimental as well as numerical methods are available for designing and optimizing deep drawing operations. The best option, however, is to combine both approaches. The present paper describes one such investigation. Here, measurements and numerical simulation were used for mapping the impact of anisotropy on thickness variation in a spherical-shaped drawn part of DC01 steel.
Variation in sheet thickness was measured on spherical-shaped drawn parts of various geometries by means of two cameras, and evaluated with digital image correlation using the ARAMIS software from the company GOM. The forming experiment was carried out on an INOVA 200 kN servohydraulic testing machine in which the force vs. piston displacement curve was recorded. The same experiment was then numerically simulated and analyzed using the AUTOFORM software. Various parameters were monitored, such as thinning, strain magnitude, formability, and others. For the purpose of this simulation, a series of mechanical tests was conducted to obtain descriptions of the experimental material of 1.5 mm thickness. A material model was constructed from the tests data involving the work-hardening curve, the impact of anisotropy, and the forming limit diagram. Specifically, these tests included tensile tests, the Nakajima test, and the stacked test, which were carried out to determine materials data for the model. The actual sheet thickness was measured on a sectioned spherical-shaped drawn part using a NIKON optical microscope.
The variations in thickness along defined lines on the sectioned drawn part were compared with the numerical simulations data using digital image correlation. The above-described experimental programme is suitable for calibrating a material model for any computational software and can correctly solve deep-drawing problems.
An equal channel angular pressing (ECAP) procedure has been developed to produce a fine – grained AZ61 magnesium alloy. The results show that the microstructure can be effectively refined with increasing equivalent strain during ECAP. For increasing ECAP process efficiency was conventional tool as a helix in the horizontal part of channel built. This fine – grained alloy has an excellent strength accompanied by reasonable good tensile ductility. The success of the development of this ECAP procedure can offer a good opportunity for the development of magnesium alloys with good mechanical properties.
This study examines the influence of surface condition on its interaction with a laser beam. The relation was tested on milled C45 steel samples with a different width of created oxide layer. The milled surface with roughness 1.6 was modified by the creation of oxide layer. The oxide layers were created by solid state pulsed laser with scanning optics. The modified samples were processed by high power diode laser with a wide spread beam. The surface temperature was measured by the thermal camera during this process. The surface hardness and hardness depth profile were measured for all modified samples and the emissivity values were measured. The effect of pretreatment on hardness and microstructure will be discussed. The goal of this paper is to describe the relation between the parameters of created oxide layer and its effect on laser beam absorption.
Production of forgings is a complex and demanding process which consists of a number of forging operations and, in many cases, includes post-forge heat treatment. An optimized manufacturing line is a prerequisite for obtaining prime-quality products which in turn are essential to profitable operation of a forging company. Problems may, however, arise from modifications to the manufacturing route due to changing customer needs. As a result, the production may have to be suspended temporarily to enable changeover and optimization. Using material-technological modelling, the required modifications can be tested and optimized under laboratory conditions outside the plant without disrupting the production. Thanks to material-technological modelling, the process parameters can be varied rapidly in response to changes in market requirements. Outcomes of the modelling runs include optimum parameters for the forging part’s manufacturing route, values of mechanical properties, and results of microstructure analysis. This article describes the use of material-technological modelling for exploring the impact of the amount of deformation and the rate of cooling of a particular forged part from the finish-forging temperature on its microstructure and related mechanical properties.
Selection of suitable construction material for devices in glass industry includes determination of required properties influencing the lifetime and functionality of part in service. The increasing requirements are the reason for reliability and effectiveness of the individual parts in glass industry, regarding to materials for their production because the mentioned materials are exposed to mechanical, thermal and corrosion effects. Therefore, it is necessary to select material which is resistant to combined loading in aggressive environment and it is also suitable and efficient from the economic aspect.
The final glass product quality is based on responsible approach to individual production procedures, including processing of molten glass interacting with metal mould surface.
Metal surfaces can be very sensitive when there are sudden changes in thermal loading (fast cooling after fast heating) in corrosive environment. There can be occurrence of microstructural change when the operating surfaces are exposed to so-called thermal shocks leading to changes of mechanical and physical properties. Material is recommended to be exposed to specific tests in order to eliminate the material degradation or to determine suitability of material. The work is focused on observation of microstructural changes under material surface, while the material was exposed to higher thermal loading.
Today’s advanced steels are required to possess high strength and ductility. It can be achieved by choosing an appropriate steel chemistry which has a substantial effect on the properties obtained by heat treatment. Mechanical properties influenced the presence of retained austenite in the final structure. Steels of this group typically require complicated heat treatment which places great demands on the equipment used. The present paper introduces new procedures aimed at simplifying the heat treatment of high-strength steels with the use of material- technological modelling.
Four experimental steels were made and cast, whose main alloying additions were manganese, silicon, chromium, molybdenum and nickel. The steels were treated using the Q-P process with subsequent interrupted quenching. The resulting structure was a mixture of martensite and retained austenite. Strength levels of more than 2000 MPa combined with 10-15 % elongation were obtained. These properties thus offer potential for the manufacture of intricate closed-die forgings with a reduced weight. Intercritical annealing was obtained structure not only on the basis of martensite, but also with certain proportion of bainitic ferrite and retained austenite.
In a vast majority of steels, a prerequisite to successful heat treatment is the phase transformation of initial austenite to the desired type of microstructure which may consist of ferrite, pearlite, bainite, martensite or their combinations. Diffusion plays an important role in this phase transformation. Together with enthalpy and entropy, two thermodynamic quantities, diffusion represents the decisive mechanism for the formation of the particular phase. The basis of diffusion is the thermally-activated movement of ions of alloying and residual elements. It is generally known that austenite becomes more stable during isothermal treatment in the transitional region between pearlitic and bainitic transformation. This is due to thermodynamic processes which arise from the chemical composition of the steel. The transformation of austenite to pearlite or bainite is generally accompanied by formation of cementite. It can be suppressed by adding silicon to the steel because this element does not dissolve in cementite, and therefore prevents its formation. The strength of this effect of silicon depends mainly on the temperature of isothermal treatment. If a steel with a sufficient silicon content is annealed at a temperature, at which silicon cannot migrate by diffusion, cementite cannot form and austenite becomes stable for hours.
Semi-solid processing of high-alloy tool steels can remove the sharp-edged primary carbides which usually form in them during solidification. Such carbides severely impair toughness and are virtually impossible to eliminate by conventional treatment routes. After classical semi-solid processing, these carbides are dissolved, and the resulting microstructure consists of polyhedral and strongly super-saturated austenite embedded in lamellar austenite-carbide network. This affects mechanical properties, predominantly under tensile loads. Therefore, it is desirable to eliminate this network by appropriately-designed thermomechanical treatment.
This experimental programme was conducted on the X210Cr12 tool steel. Various temperatures for heating to the semi-solid state between 1225 and 1280 °C were tested. Then, water quenching and reheating to a forming temperature was tested. Finally, variants with interrupted quenching in the 750–1100 °C were tried as well. It was found that formation of the lamellar network strongly depends on the temperature of heating to semi-solid state. The thermomechanical treatment produced microstructures in which the matrix consisted of a mixture of polyhedral austenite grains, and the MA constituent. The lamellar eutectic network was partially or even completely eliminated and substituted with a mixture of very fine recrystallized austenite grains and chromium carbide precipitates. Fine M7C3 carbides were present in the austenitic-martensitic matrix as well. When appropriate conditions were chosen, high mechanical properties were obtained, among them the hardness value of 860 HV10.
TiAl based alloys with nominal compositions Ti-(39-43.5)Al-(3-4)Nb-0.1B-xC (at.%), where carbon content x is ranging from 0.1 to 7 at.%, were characterised by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), wave dispersive spectroscopy (WDS), X-ray diffraction analysis (XRD) and elemental LECO analysers of light elements (O, N and C). Morphology and volume fraction of coexisting phases are quantitatively analysed using computerised image analyser. The effect of carbon content on Vickers microhardness of observed carbide particles and intermetallic matrix is evaluated and discussed. Instrumented Vickers hardness measurements are carried out to evaluate the effect of carbon content on room-temperature Young modulus of the studied alloys.
A method for treatment of chips based alumium alloys through solid-state recycling was studied. The process of chip forward extrusion was investigated using four different model of dies through numerical simulation program DEFORM 3D. For the simulation, there were used a square die, square die whit integrated equal channel angular pressing (iECAP) and a porthole die one and four square profile. According to the results from numerical simulations, greatest effective strain was achieved using a porthole die with a four square profile. According to the FEM simulation carried out for industrial purposes, a porthole die with two round profile. Two rods with a diameter of 30 mm were extruded. For the extrusion, there were used separated chips based on AW 6060. The chip-based billets a diameter of 150 mm were prepared by cold pressing. Mechanical properties and microstructure of the chip-based billets extruded through the porthole die were investigated and compared to standards. Subsequently, forward extrusion for industrial purposes was analyzed by FEM simulation. Maximum volume and distribution of effective strain, strain rate, velocity and shear stress were analyzed.
Current trend of nuclear power plant components lifetime extension requires precise and credible information of structural material degradation. The use of standard methods for determination of material properties can cause considerable damage of the assessed component when sampling the test material from the component.
Due to necessary volume of test material connected with high radioactivity it is not possible to obtain mechanical properties by standard test methods for the reactor pressure vessel internals. Moreover, the internals of RPV and other hardly exchangeable components, e.g. primary circuit or steam generator, are not usually covered by surveillance programs.
The poster describes two innovative testing methods – Small Punch Testing (SPT) and Automated Ball Indentation Test (ABIT) – which are based on the determination of material properties from miniaturized testing specimens. The methods are very promising for the possibility of enlargement the present data base of irradiated materials testing results and the ABIT method also enables the option of component in-situ testing.
The testing results were obtained for base reactor pressure vessel material – 15Kh2MFA – in both states, initial unirradiated and irradiated. The standard conventional testing technique here is represented by the standard static tensile test. The data obtained by this technique were used for correlations with the results of perspective methods of SPT and ABIT. The results of correlations were found very promising for prospective determination of material properties of both unirradiated and irradiated materials.
Nowadays, water energy represents the renewable source for worldwide electrical energy production but there are the spheres where potential of water energy is not utilised sufficiently. Therefore, the significant attention has to be paid to materials for production of water turbine components.
The blades are the most important and the most vulnerable water turbine component. They are exposed to effect of surrounding environment and when they are in service, the mentioned effect is superposed by enormous loading during energy transformation. Water turbine blade material has to be suitable from service and energy aspects – these aspects represent the increasing qualitative requirements. During service, materials of water turbine blades have to withstand high centrifugal forces, temperature changes, pitting erosion that is superposed by corrosion. Superposing of negative effects leads to occurrence of mechanical damage on blade surface and it causes lifetime reduction. Material for water turbine has to meet all required criteria and therefore, the selection of this material is based on determination of many influencing factors. The given work is devoted to determination of material corrosion susceptibility and selection of optimal materials for Pelton water turbine blades because the results are expected to be useful for evaluation of material wear susceptibility.
The paper presents test results concerning the relationship between selected input parameters and the process efficiency for the sanding of plaster surfaces with alundum abrasive discs. The input parameters under study were the size of the abrasive grains, the force exerted by the plaster sample pressing against the abrasive disc and the no-load rotational speed of the abrasive disc. The experimental data illustrating the relationship between the process efficiency and the particular input parameters were used to select the optimum plaster sanding conditions.
Heat and thermo-mechanical treatments with various processing parameters were applied to middle carbon low alloyed 42SiMn steel. The aim of the treatment was to obtain multiphase microstructure typical for TRIP (Transformation induced plasticity) steel and to achieve the best combination of ultimate tensile strength and ductility. TRIP steels typically possess about 5-15% of metastable retained austenite, which can transform to martensite during plastic deformation. The gradual phase transformation during loading postpones the onset of necking, thus increasing ultimate tensile strength and ductility at the same time. Manganese and silicon used as the main alloying of the experimental steel are employed to increase austenite stability and to hinder cementite precipitation during the treatment. All proposed methods of heat and thermo-mechanical treatment contain bainitic hold at 400°C or 425°C. The final microstructures were very complex, consisting of bainite, ferrite, very small areas of extremely fine perlite lamellas, about 10% of retained austenite and M-A constituent (austenitic islands partially transformed to martensite). Even though pearlite and martensite are undesirable microstructure in TRIP steel, the samples reached tensile strength 850-1065 MPa with ductility A5mm 26-47%.
This article deals with tribological and corrosion resistance comparison of plasma nitrided and nitrocarburized 42CrMo4 steel used for breech mechanism in the armament production. Increasing of materials demands (like wear resistance, surface hardness, running-in properties and corrosion resistance) used for armament production and in other industrial application leads in the field of surface treatment. Experimental steel samples were plasma nitrided under different nitriding gas ratio at 500 °C for 15h and nitrocarburized for 45 min at temperature 590°C and consequently post-oxidized for 10 min at 430°C. Individual 42CrMo4 steel samples were subsequently metallographically evaluated and characterized by hardness and microhardness measuring. The wear test “pin on disc’’ was realized for measuring of adhesive wear and coefficient of friction during unlubricated sliding. NSS corrosion tests were realized for corrosion resistance evaluation and expressed by corroded area and weight loss evaluation. The corrosion resistance evaluation were by the surface corrosion-free surfaces evaluation supplemented using the laser confocal microscopy. Due to different surface treatment and plasma nitriding conditions, there are wear resistance and corrosion resistance differences evident between the plasma nitrided steel samples as well.
Material properties of nuclear fuel claddings and their behavior under operational and accident conditions are one of the key issues in the nuclear fuel licensing process. These characteristics are described in detail in the number of scientific publications and theses. During the research of material properties it is necessary to check the claddings behavior after irradiation by neutrons for evaluation of important parameters, such as: irradiation induced growth, yield strength, ductility, toughness, which depend on the received neutron fluency. Observation of changes in the selected parameters is the main aim of the irradiation program in the frame of long term research project based on cooperation of several organizations in Russia and Czech Republic.
This project has been in progress since 2012, when the material cluster assemblies (MCA) were designed and manufactured in cooperation with JSC TVEL, OKBM and VNIINM. The construction of the MCA is based on standard components and materials of the reactor core. The main goal of the project is the support for the nuclear fuel licensing process and providing the correlation between the real operation in VVER reactor core and large experimental databases obtained in research reactors and laboratories working with different neutron spectra. Irradiation induced growth and other important parameters will be evaluated depending on neutron fluency under the operational conditions of VVER-1000 reactor. The samples were placed into the ampoules, which are the part of material cluster assemblies. After the irradiation, the ampoules will be cut off the MCA, and transferred to the hot cells for further examination. A special equipment for cutting off samples, has been evolved in cooperation with ŠKODA JS. Its main advantages are simple working mechanism, robust construction and compatibility with fuel assemblies. In August 2017, cutting off the first set of ampoules is planned (after one year of irradiation). After that, one set of ampoules will be cut off every year (up to 6 years of irradiation). The project is planned to be finished in 2022/2023.
Alloys on the base of TiNb were heat treated by two different regimes in argon or hydrogen atmospheres. The hot compression tests, measurement of microhardness and microstructure analysis were performed. Based on the hot compression test results, the plasticity at elevated temperatures was evaluated. The influence of hydrogen on microstructure and mechanical properties of TiNb alloys was discussed.
The aim of this work is to study the influence of successive weld repairs on the microstructure, the mechanical properties and the corrosion resistance of the weldment of an HSLA X70steel. Detailed microstructural examination combined to grain size measurement showed that beyond the second weld repair, the microstructure of the HAZ undergoes significant change in the grain morphology and grain growth. Consequently, a loss of the mechanical properties namely the yield strength and the toughness with the number of the weld repairs was recorded. Potentiodynamic polarization tests of different repair weld were evaluated in 0.8% HCl solution. Beyond the second weld repair the corrosion resistance decrease due to the formation of martensite-austenite (M-A) and bainitic structures.
This work describes creation of FE model of clinched joint and brings information about its verification with help of experiment. Also the sensitivity of the simulation model to the selected parameters (size of the model and coefficient of friction) and boundary conditions is studied so that the model is close to the reality. Deformation and uniaxial stress near the joint obtained with help of strain gauge is the output from the unidirectional, nondestructive test. Comparison of two values of stress in the chosen place obtained by experiment and FE simulation is the principle for verification of FE model and its adjustment. Based on the results it can be said that the FE model corresponds with the reality with the desired accuracy.
This paper describes a method for studying the wear of abrasive mesh discs differing in the type of grains employed to sand plaster. The tests were conducted at a specially developed and constructed setup. The investigations involved analysing the influence of the basic input parameters (the size of the abrasive grains covering the disc surface, the force exerted by the plaster sample pressing against the abrasive disc and the no-load speed of the abrasive disc) on the efficiency of the sanding process. The paper also describes the structural details of the experimental setup.
The compound casting process was used to join AZ91 magnesium alloy with AlSi17 aluminium alloy. Molten AZ91 was cast onto a solid AlSi17 insert placed in steel mould heated to 370 oC. Results showed that temperature of the AZ91 melt affect the formation of the bonding zone between two alloys. The continuous bonding zone was formed by applying melt temp. 650 oC. The applying higher temperature i.e. 680 oC and 700 oC not lead to formation continuous metallurgic transition zone at AZ91/AlSi17 interface. Characterization of the bonding zone was performed by an optical microscope and scanning electron microscope equipped with the energy dispersive X-ray (EDS) detector. In bonding zone in the vicinity to the AlSi17 alloy the following structural constituents occur: an Al3Mg2 intermetallic phase, primary Si particles surrounded by a rim of an Mg2Si intermetallic phase and fine Mg2Si particles. The bonding zone near the AZ91 alloy had eutectic structure composed of an Mg17Al12 intermetallic phase and a solid solution of Al and Si in Mg. The microhardness of the bonding zone containing intermetallic phases was much higher compared to microhardness both alloys join by compound casting.
The possibility of producing ultrafine-grained (UFG) structure in martensitic steel by severe plastic deformation was studied. Using combined SPD technique (preliminary heat treatment and high press torsion) the integral bulk billets of martensitic steel were produceв. The features of the microstructure were investigated by ТЕМ. The influence of different modes of HPT on the microstructure and mechanical properties was investigated.
Rolling element bearings are widely-used machine components and their failure can result in damage to the whole machine. A bearing failure can be caused by many factors. In most cases it is damage on the raceway surface as a result of rolling contact fatigue (RCF). This article describes the fatigue analysis consists of determining service-life of a roller bearing using a stress-strain analysis with finite element method and subsequent numeric calculation using software fe-safe with application of multiaxial fatigue criterion. These theoretical results are compared to the experiments carried out on AXMAT test-rig with more accurate defect detection using acoustic emission method. Numerical service-life calculation can be applied as tool for fatigue life prediction of full scale bearing with sufficient correlation with experimental results.
The paper reports on the behaviour of low alloyed TRIP (transformation induced plasticity) steel alloyed with Niobium during tensile test. The structures were analysed using in-situ tensile testing coupled with EBSD analysis. Steel specimens were of same chemical composition; however, three different annealing temperatures, 800°C, 850°C and 950°C, were applied to the material during the heat treatment. The treatment consisted of annealing for 20 minutes in the furnace; cooling in salt bath after the heating and holding at 425°C for 20 minutes for all the samples. Flat samples for deformation SEM stage were cut out from the heat-treated bars. Untreated bar was used as reference material. In situ documentation of microstructure and crystallography development were carried out during the deformation experiments. High deformation lead to significant degradation of EBSD signal.
The features of structure refinement in a copper alloy of the Cu-Cr-Zr system via severe plastic deformation (SPD) processing under different levels of deformation action were studied.
The SPD processing techniques of high-pressure torsion (HPT) and equal-channel angular pressing (ECAP) were used in the investigation. It has been established that the level of accumulated strain is an important characteristic that has an effect on the structural transformations; ACKNOWLEDGEMENT: The authors acknowledge the financial support by the Ministry of Education and Science of the Russian Federation under Grant agreement No. 14.586.21.0025 (unique identification number RFMEFI58616X0025).
The importance of 3D printing in today’s industry is continuously increasing. One of the materials which are frequently used in this process is the precipitation-hardenable MS1 Maraging steel whose properties after conventional treatment have been thoroughly mapped. Maraging steels belong to the strongest homogeneous steel materials ever. Their alloying additions include cobalt, molybdenum, titanium and aluminium, and their unusual properties make them candidates for heavy-duty parts operating predominantly under dynamic loading. Semi-solid processing of this particular steel enables near-net shape products to be made using a single production step. Furthermore, unconventional microstructure and physical, chemical and mechanical properties can be obtained by this process. The semi-solid processing route and the mechanical properties achieved by it can expand the potential uses of this material. Semi-solid processing of small volumes of material has already been mastered with high-alloy steels which offer a wide range of forming temperatures. However, as this process is technically demanding, its use for medium and low-alloy ultra-high-strength steels has not been explored in greater detail yet. In the present experiment, MS1 Maraging steel was studied. The experimental feedstock was made by 3D printing. The initial set of semi-solid processing parameters was proposed on the basis of calculation and then tested experimentally. In this article, description of the microstructures of this steel before and after several semi-solid processing routes is given, based on examinations using optical and electron microscopy.
On VSB -Technical University of Ostrava developed a method that uses the principle of severe plastic deformation to refine the structure and enhance mechanical properties of sheet metal strips. The greatest importance in practice represents an increase in yield strength and ultimate strength of sheet metal strips. The DRECE method (Dual Rolls Equal Channel Extrusion) is a newly developed method. Severe plastic deformation results in a high degree of the material reformation. The method can be used to produce metallic materials with a very fine grain structure.
The paper analyses the effects of the values of angles of the newly developed forming tools on the achievement of mechanical properties in selected carbon steels by SPD process. The different types of steels were verified experimentally. Experiments were performed on the sheet metal strip with dimensions 58 (width) x 2 (thickness) x 1000 (length) mm.
In the article were made numerical and laboratory tests of two-layers rolling process sheet composed of Al99, 8 + M1E. Laboratory tests made with use of 150 mm diameter working rolls mill. To the modeling of the bimetallic plate rolling were taken the FEM Forge 2D software based on the theory of plasticity and MathCad program (in which to the rolling process modeling were used the mathematical model developed in the work [5] based on the theory of viscoelasticity). The aim of study was to determine the influence of layer thickness HT0/HM0 and relative deformation on the uneven distribution of steel sheet deformation after rolling process. Calculations based on the theory of viscoelasticity allowed additionally take into account the impact of the delayed effects of the variation of viscoelastic deformation of layers of the bimetallic plate rolling process.
Charpy test is one of the basic material tests used for material properties characterization. In order to avoid brittle failure under service conditions, transition temperature based on Charpy impact tests is determined for the materials exhibiting transition behavior. The size of the experimental material does not allow in all cases application of standard full size specimens (10x10mm) and sub-size specimens have to be used. Although, some of sub-sized geometries are standardized, procedures for comparison of results obtained for various specimen geometries are not standardized due to ambiguous relations for different applications; therefore relations for specific areas have to be individually established.
This paper discusses the correlation between specimen dimensions and transition temperature. Notch toughness properties of Standard Charpy-V specimens are compared to samples with lower width (7.5 mm, 5 mm, 2.5 mm) and sub-size Charpy specimens with cross section 3x4. In this study transition curves are correlated with fracture appearance based on the results for 5 considered geometries. On the basis of the obtained results, correlation procedure for transition temperature determination of full size specimens based on fracture appearance of sub-sized specimens is proposed.
Aluminium Al-Mg-Si-type alloys (6xxx-series) exhibit good mechanical properties, formability, weldability and good corrosion resistance in various environments. They often find use in automotive industry and other applications Some alloys, however, particularly those with higher copper levels, show increased susceptibility to intergranular corrosion.
Intergranular corrosion (IGC) is typically related to the formation of microgalvanic cells between cathodic, more noble phases and depleted (precipitate-free) zones along grain boundaries. It is encountered mainly in AlMgSi alloys containing Cu, where it is thought to be related to the formation Q-phase precipitates (Al4Mg8Si7Cu2) along grain boundaries.
The present paper describes the effects of mechanical working (pressing, drawing and straightening) and artificial aging on intergranular corrosion in rods of the 6064 alloy. The resistance to intergranular corrosion was mapped using corrosion tests according to EN ISO 11846, method B.
Corrosion tests showed dependence of corrosion type on mechanical processing of the material. Intergranular, pitting and transgranular corrosion was observed. Artificial ageing influenced mainly the depth of the corrosion.
Steels and other ferrous alloys are very well known as construction materials but still are widely used and in the near future this will not change. Among the steel and cast steel resistant to corrosion most modern and dynamically developing group are ferritic-austenitic alloys, commonly known as duplex. Higher than austenitic steels, mechanical properties and good corrosion resistance in both overall and pitting make duplex steels irreplaceable material in the petrochemical industry, power, pulp and paper, food. Duplex steels and cast steels characterized by multiphase microstructure have a complex plasticity due the fact of deforming two different phase austenite and ferrite. The chemical composition of a steel containing about 0.02% C, 26% Cr, 6.5% Ni, 3% Mo, 1.4% Mn, 0.2% N guarantees that already, in the raw state, immediately after casting is obtained ferritic - austenitic structure. The paper present results of the X2CrNiMo25-6-3 duplex steel physical tests made with the Gleeble 3800 machine. The researches concerned problems of the influence of primary structure on the plasticity and sigma phase formation. The deformations was applied at temperature from 1150 to 800°C. As it was presented by many authors this phase have a very strong destroying influence already at the stage of cast.
Presented paper summarizes weld assessment on the basis of national standards. The approach concerning the static loading has been still not adequately developed in standards. The standard of American Institute of Steel Construction was considered as the best candidate for implementation into finite element method using post-processing of a particular weld. A comparative analysis of maximum allowable loadings of weld connection models loaded in-plane and out-of-plane has been performed. Results obtained by finite element method and American and Czech standards were compared and the conclusions of applicability and reliability were made.
Insulating material is an important part of thermocouples because it insulates wires from each other. Recently, ceramics Al2O3 (purity 99.7 %) has been the most used materials in temperature calibration laboratories. The temperature maximum of standard materials is usually around 1800 °C and their properties are not suitable at measurement in horizontal position. This material starts to deform above temperature 1400 °C plastically and deformation has a negative influence for the measurement. Scale of the deformation depends on both temperature gradient along the material including its immersion and time of exposure on the high temperatures.
The aim of this work was to make an overview and testing of other materials in the temperature range (1400 – 1800) °C which might replace Al2O3. Selected materials were tested at horizontal furnace Clasic. Tested materials are used for both insulation powder and capillary. The suitability of insulating materials for thermocouple preparation will be presented; ACKNOWLEDGEMENT: This work is supported by internal project No. 16101202.
Computer simulation of the combination extrusion process for ENAW-1050A aluminum alloy is presented. The tests were carried out for three values of relative strain in forward direction E1: 0.77, 0.69 and 0.59. For each value of relative strain E1, three different values of strain in backward direction, E2, were taken: 0.41, 0.52, 0.64. The effect of the relative strain degree on the development and values of the punch force was determined. It was demonstrated that the punch force increases with the increasing degree of relative strain in both forward and backward directions.
The paper presents a new knowledge and experiences with verification and optimization of production technology of heavy slab ingot weighing 40 t from tool steel using the results of numerical modelling and of operational experiments at steel plant in VÍTKOVICE HEAVY MACHINERY a.s. The final porosity, macrosegregation and the risk of cracks were predicted. Based on the results, the slab ingot can be used instead of the conventional heavy steel ingot. Also, the ratio, the chamfer and the external shape of the wall of the new design of the slab ingot was improved which enables to reduce a production cost while internal quality of steel ingots is also at very high level.
3D printing technologies like Selective Laser Melting (SLM) or Electron Beam Melting (EBM) produce components of very complicated shapes from various kinds of materials. In this work a highly porous (porosity of almost 90 vol. %) stainless steel component was prepared by SLM. The material was characterized in terms of structure, surface chemistry and mechanical properties. It was observed that mechanical properties of the material were similar to those of trabecular human bone. The tests realized in this work confirmed suitability of the porous material prepared by SLM for the use in medicine, for example, for scaffolds designed to repair bone defects.
Energo-dispersive spectrometer (EDS) is a method that works on the principle of measuring energy X-ray radiation, which is caused by the impact of primary electrons on the valence electron element where the electron punched and then replaced by an electron from the lower shell. Each element has a different energy x-ray radiation, and the type and the X-ray quanta is determined by the type and amount of element in the sample. EDS analysis is used for rapid (about 100 seconds) and its elemental analysis (depending on the proton number and type of detector to tenths of a percent) and elemental mapping. An accelerated electron beam is incident on the surface of the sample to be studied and interacts with atoms. When this interaction may cause ejection of one electron from the inner peel atom. Atom in this way gets into an excited state. Deexcitation, the transition to the initial state takes place jumping an electron from one energy level to a higher level with a missing electron. This jump is accompanied by the emission of quanta of elec-tromagnetic radiation, a photon of energy precisely determined by the difference of energy levels. These energies are in the relatively wide range of energies. However, for the EDS is used an area of approximately 100 keV for about 15 to 20 keV. From the intensity of the emitted photon which falls on a certain interval of energy, it is possible to obtain information not only about the elemental composition, but also to quantify the amount (ratio) of individual elements in the sample.
This paper, examines the microstructure and the mechanical proprieties of WC-Co and low carbon steel joints obtained by Tungsten Inert Gas (TIG) brazing using two different thermal sprayed interlayers. On the connection zone, the characterizations of the WC–Co/interlayer/steel joints were studied by SEM, EDS and XRD. Microhardness measurements and shear test were made.
The interlayer promoted the formation of interdiffusion zone, which possessed positive effects on the bond strength of the WC– Co/interlayer/steel joints. Having performed line and surface micro analyses of various zones, postbrazing diffusions of Co and Ni and other elements were determined.
The hardness distribution in microhardness measurements on this zone shows the existence of element diffusion.
Superalloys based on nickel and selected steels are widely used in the aerospace industry, because of their excellent mechanical properties, heat resistance and creep resistance. Metal sheets of these materials are plastically deformed and applied, inter alia, to critical components of aircraft engines. Due to the chemical composition these materials are hardly deformable. There are various methods to improve the formability of these materials, including plastic deformation at an elevated or high temperature, or a suitable heat treatment before forming process. The paper presents results of the metal sheets testing after heat treatment.
For the research, sheets of two types of nickel superalloys type Inconel and of three types of steels were chosen. These materials were subjected to multivariate heat treatment at different temperature range and time. After this step, the mechanical properties were examined according to the metal sheet rolling direction. The results were compared and determined the optimal type of pre-trial plasticizing heat treatment for each of the materials.