• Phase and Petrographic Analysis of Petrurgical Materials Obtained on the Base of Metamorphic Rocks

    pg(s) 391-393

    The phase and petrographic analysis of a part of previously prepared test samples of coloured petrographic materials coloured with different contents of CuO, SnO2, CoO, Cr2O3 were studied. The raw materials are based on metamorphic rocks – dolomite marbles from the village of Ustrem and the village of Mramor, processed by melting at 1450°C, so that after crystallization, petrographic phases are obtained, which are confirmed by X-ray phase and petrographic analysis. The main characteristics of the colouring aggregates and their effect on the mineral composition and crystal structure are described.

  • Influence of the filler material on the mechanical characteristics of structural steel GMAW and MCAW welded joints

    pg(s) 387-390

    The main objective of this paper is to get an accurate result of the mechanical characteristics of welded joints of structural steel performed with two different types of filler material, wire, which are characterized by: simple welding technology, low structural changes of the basic materials, as well as lower cost of welds. The whole research is conducted in accordance with European standards for welding. Research has been conducted on two standard plates made of constructive steel S355J2 + N Z15, with a thickness of 15mm, according to standard EN ISO 15614-1. Both plates are welded with solid wire and metal cored wire under the protection of a gas mixture based on argon, and the whole process is supported by standard documentation. Destructive tests have been performed to determine the welded joints’ quality and influence of different filler materials, such as tensile test, impact test, and hardness test in the weld and heat-affected zone. The experimental results confirm that the gas metal arc welding of structural steel in the protection of inert gas with solid and metal cored wire is a procedure that ensures the quality and safety of welded joints and retention properties of the base material after the welding process.

  • Towards the theory of evolution of spherical and ellipsoidal particles in metastable melts and solutions

    pg(s) 358-366

    This study is concerned with the dynamical laws for particle velocities in supercooled and supersaturated liquids. The cases of spherical and ellipsoidal particle shapes are considered. Also, we consider various growth conditions such as stationary and non-stationary approximations, the shift of crystallization temperature caused by the phase interface curvature, and the kinetics of atoms sticking to the solid-liquid boundary. The dynamical laws under consideration are in good agreement with experiments.

  • Influence of mechanically activated particles on the activity of polymer engineering materials and compositions based on themt

    pg(s) 327-328

    The article presents the results of studies on the study of the physical and mechanical characteristics of polymeric materials modified with mechanically activated particles. It is shown that the use of mechanically activated nanosized particles makes it possible to achieve a significant effect of increasing operational characteristics at relatively low degrees of modification of 0.05% wt. – 3% wt. The use of modifiers at such concentrations in polymer matrices makes it possible to preserve the basic technology for the processing of polymeric materials and equipment in the manufacture of composite materials on a polymer matrix.

  • New regulations on the formaldehyde emission from wood-based panels

    pg(s) 293-295

    Formaldehyde is considered a health hazard, hence the wood-based panels must be within the limits imposed by the strictest regulations regarding the formaldehyde release. New national and international international regulations of formaldehyde emission from wood-based panels widely used in furniture industry were investigated in this study. The results of the study can be useful for the woodbased panel factories to follow the standards and regulations in terms of formaldehyde emission.

  • Nanodisperse modifiers produced by the shs method for composite materials of automotive equipment

    pg(s) 290-292

    The object of the study was carbon particles obtained by the method of self-propagating high-temperature synthesis. The purpose of the work is the development of compositions and technologies for obtaining competitive composite materials modified with low-dimensional carbon modifiers based on vegetable raw materials.

  • The Effect of Vanadium, Niobium and Boron on Microstructure, Mechanical and Corrosion Properties of High-Chromium White Cast Irons

    pg(s) 286-289

    The influence of the vanadium, niobium and boron addition on properties of high-chromium white cast iron alloys for grinding balls is investigated in this paper. These alloying elements were individually added to the high-chromium white cast iron alloys with monitoring of changes in microstructure, corrosion rate, and mechanical properties in the as-cast conditions. The microstructure in all tested alloys consists of primary austenite dendrites and eutectic colonies, which consist of M7C3 carbides and austenite. The addition of V, Nb or B affects, to a greater or lesser extent, the size, morphology and volume fraction of both primary austenite dendrites and eutectic colonies. Samples of iron alloyed with vanadium and boron have a much finer structure than unmodified (base) alloy and niobium alloyed iron sample. Vanadium affects the decrease in the volume fraction of the primary austenitic phase, and the increase in the volume fraction of eutectic colonies, and thus the eutectic carbide phase in hypoeutectic alloys of high-chromium iron. The tested alloys have a comparable values of average hardness in the cross section of cast balls, as well as compressive yield strength, noting that the addition of vanadium increases the hardness, while boron addition increases the compressive yield stress. The single addition of all of three tested alloying elements shifts the corrosion potentials (and Tafel curves) of modified high-chromium white irons toward less negative values. The most favorable values of mechanical and corrosion properties were measured for the iron modified with 0.021 % of boron.

  • Recent developments and regulations in fire resistance of wood and wood-based composites

    pg(s) 260-262

    This study focused on the fire-retardant treatment of wood and wood-based composites using various methods. The recent developments in the fire-retardant standards and classification of wood and wood-based composites were reviewed. Most commonly used fire-retardants and commercial application methods of fire retardants such as boron compounds and phosphates to improve fire resistance of wood and wood based composites were explained. Furthermore, fire-retardant mechanism was informed. Novel nanomaterials used in the fire resistance of wood and wood-based composites were introduced. Significant criteria in choosing of the suitable fire retardants for wood and wood-based composites were explained

  • Features of the tribological behavior of the magnesium alloy Mg -1% ca depending on the structural state

    pg(s) 255-259

    This paper presents experimental data on the tribological properties of the Mg-1%Ca magnesium alloy with different microstructures (coarse-grained microstructure in the initial state, and ultrafine-grained and nanocrystaline microstructures after severe plastic deformation via two processes – equal-channel angular pressing and high pressure torsion) in contact with an indenter made of the Fe-18W-4Cr- 0.8C steel without any coating and with applied hydroxyapatite, which is the main mineral component of bones. An indenter with hydroxyapatite on the surface was used as a bone simulator. As a result of the experiments, it was found that the shear strength of adhesive bonds and the adhesive component of the friction coefficient are structurally sensitive parameters. For all the samples in the considered contact pairs, when using a bone tissue simulator the strength of adhesive bonds was lower than that when using a steel indenter. It is noted that ultrafine-grained and nanocrystalline structures produced as a result of severe plastic deformation via two processes, equal-channel angular pressing and high pressure torsion, contribute to a decrease in the shear strength of adhesive bonds and the adhesive component of the friction coefficient due to strengthening resulting from grain size reduction from originally 100 μm to 1.4–4 μm on average in the investigated Mg-Ca magnesium alloy.

  • Nanophase structures in vacuum multilayer coatings formed on tool and high-speed steels

    pg(s) 251-254

    The most common coatings for metalworking tools include titanium nitride, titanium carbide, titanium carbonitride, zirconium nitride, zirconium carbide, zirconium carbonitride, compounds based on chromium, titanium, aluminum, diamond-like coatings that are formed in vacuum using PVD, CVD, PCVD methods or a combination of the above methods. The current trend in the deposition of vacuum coatings is the production of multifunctional coatings, which can significantly increase operational characteristics compared to the starting materials. To form multifunctional coatings, the creation of “sandwich” structures is used, since each layer performs various functions – forming, antiwear, anticorrosion. Thus, the use of a composite multilayer coating containing layers of titanium nitride, titanium, diamondcontaining compounds with a thickness of one layer from 0.1 to 2 microns makes it possible to increase the wear resistance of a metalworking tool by 1.5-5 times.

  • Analytical approach to crack tip plasticity of dental CoCrMo alloy

    pg(s) 248-250

    In this paper, a thin infinite plate of CoCrMo alloy with a straight crack was loaded perpendicularly to the crack plane. CoCrMo alloys are due to their suitable mechanical and corrosion properties widely used for dental applications. The importance of good mechanical properties is reflected in ensuring the functional and technical durability of dental appliances. The intention of this paper is to use a mathematical approach in analyzing a thin infinite plate with a straight crack to the rather complex occurrences within the cohesive zones around the crack tips. The dependence of plastic zone magnitude around the crack tip on an external load of dental CoCrMo alloy plate was considered in this paper. Static tensile tests were carried out to determine the mechanical properties of dental CoCrMo alloy. At plastic deformation, the dental CoCrMo alloy is nonlinearly hardened in accordance with the Ramberg-Osgood equation which parameters were determined using a least-squares method from experimental data. The application of the Dugdale model the plastic zone magnitude around the crack tip was determined. The stress intensity coefficient from the cohesive stresses was calculated using Green functions. The analytical methods, assuming a small plastic zone around a crack tip, were used in the analysis. The results were obtained by means of a commercial software package and presented in the form of diagrams.