Solid State Phenomena Vol. 320

Abstract: Thin-walled hollow mini-spheres several millimeters in diameter have promising applications as components for the absorption of sound, pressure pulses and mechanical vibrations, as well as heat transfer elements. In this paper, an assessment of some physical and mechanical properties, including the strength and elasticity of metallic mini spheres, is given. To a great extent, the properties are determined by the wall material, however, can be modified by the coating as well.

Abstract: The dynamic alloying of aluminum and its alloy with a high-speed stream of silicon carbide (SiC) particles simulates the effect of a stream of cosmic dust on spacecraft materials. The study showed a structure change in the volume of aluminum and its alloy and the formation of new structural elements. The transformation of the structure during dynamic alloying leads to a change of the composition and mechanical properties of the matrix material.

Abstract: Contact interaction in a wheel-rail pair and its corresponding stress-strain state for various combinations of materials of this pair and the weights of passenger and freight cars were considered. The materials under study were steel and high-strength cast iron based structural material MoNiCa with strength and wear-fatigue characteristics close to steel ones.The load on each wheel was: 53.9 and 294.3 kN for an empty and loaded freight car, 146.8 kN and 230.5 kN for an empty and loaded passenger car. The bottom surface of the rail was rigidly fixed.Young's modules were adopted as follows: 200 GPa for steel and 165 for MoNiCa. The results of finite element calculations of the three-dimensional stress-strain state showed that the largest von Mises stresses of 613.08 MPa occur in the wheel (steel)-rail (steel) pair of the loaded freight car. For all types of loading, the lowest stresses (15.8 % – 16.7 % less than in the steel-steel pair) are observed in the wheel (MoNiCa)-rail (MoNiCa) pair. This indicates the appropriateness of using MoNiCa for the manufacturing elements of the wheel-rail system.

Abstract: Shielding materials play an essential role in the prevention of electromagnetic irradiation and electromagnetic interference from electric equipment. Physico-chemical modification of crumb rubber and devulcanised rubber leads to the formation of materials with distinctive properties suitable for the development of composites for electromagnetic protection. The current paper introduces an approach for secondary raw materials modification for production of composite mixtures, which could be used electromagnetic shielding materials. Experimental evaluation of electromagnetic shielding properties was performed. Devulcanised rubber-based composite materials are considered as electromagnetic shielding materials for equipment in transport systems and civil engineering applications.

Abstract: Thermal barrier coatings are widely used for protection of gas turbine parts against high temperature oxidation and hot corrosion. In present work the microstructural assessment of TBCs produced by atmospheric plasma spray (APS) method was conducted. Three types of ceramic powders were used: magnesia- stabilized zirconia oxide (Metco 210), yttria stabilized zirconia oxide (YSZ -Metco 204) and fine-grained YSZ – Metco 6700. As a base material the Inconel 713 was used as well and CoNiCrAlY was plasma sprayed (APS) as a bond coat. The thickness of all ceramic layers was in range 80 – 110 μm. The elemental mapping of cross-section of magnesia-stabilized zirconia showed the presence of Mg, Zr and O in outer layer. In the YSZ ceramic layer the Y, Zr and O were observed during elemental mapping. The isothermal oxidation test was conducted at 1100 °C for 500 h in static laboratory air. On all samples the delamination and spallation of ceramic layers was observed. Chemical composition analysis of coatings showed the presence of two areas: the first one contained elements from bond coats: Ni, Cr, Al, Co and second area contained O, Cr Co and O that suggest the scale formation. The obtained results showed the total degradation of all ceramic layers as a result of internal stresses in bond-coat. Microscopic analysis showed the areas with complete degradation of bond coats and formation of thick oxides layer.

Abstract: Nanostructured smart coatings (NSC) based on the TiAlSi-CN composite structure elements were deposited using advanced reactive physical vapor deposition (PVD) method. The novel NSC on steel substrates demonstrated enhanced wear and corrosion resistance required for multifunctional high-tech applications. The deposited NSC containing TiAlSi-CN nanoparticles strengthened by Cr, Nb and Hf additives exhibited a coefficient of friction (CoF) less than 0.2 and wear rate as low as 10E^-8 mm³/Nm. In addition, some self-healing properties were observed preventing denitrification of the core carbon-nitride (CN) layer due to specific tribochemical reactions of Al and Si constituents. Thus, the chemical composition and tentative nano-structure of the NSC can be described by a stoichiometric formula TiAlSi-CN:Me/a-C_xN_y:Si₃N₄, where Me=Cr, Nb or Hf.

Abstract: The nitriding process is a well-known technology for increasing of wear resistance of steel. The conventional gas nitriding process of stainless steel is difficult in the case of surface passivation and formation of Cr₂O₃. The using of plasma enables to form hard surface area during the nitriding process. The plasma nitriding process was developed using Ionit Metaplas device. The kinetic growth was analysed in 2, 4, 6 and 8 h processes. The plasma gasses composition was selected for formation only diffusion layer without “white area” of nitrides. The microstructure, chemical and phase composition were analysed. As a result, the diffusion layer was formed. The iron nitrides formed the precipitations in the diffusion layer. The obtained results showed that 4h process enables to form nitride layer with required composition and hardness. The relationship between process time and nitride layer thickness and its hardness was observed.

Abstract: In the article first tests of production of YSZ ceramic coatings using PS-PVD method on graphite were presented. The influence of hydrogen addition on structure and morphology of columns was analyzed. It was shown that width of the columns increased with the increase of hydrogen content in the plasma. The presence of re-solidified oxide vapors between ceramic columns was observed. The obtained results showed the possibility of using of YSZ ceramic layer as a protective layer for metallurgical applications.

Abstract: The boride coatings are characterized by attractive set of properties: high wear resistance and good high-temperature corrosion. In present research the diffusion boride coatings were obtained on X39CrMo17-1 stainless steel. The pack-boriding process was conducted using commercial Ekabor 2 powder. The influence of time of process on thickness and chemical composition was analysed. The boriding process was conducted in 2, 4, 6 hours at 1000 °C using retort furnace. The obtained coating was characterized by double layer structure and contained the FeB in outer layer and Fe₂B in inner layer. The thickness of boride coatings increased with process time. The analysis of obtained results showed that the optimal thickness of coating was obtained during 4-h pack boriding.