Materials Science Forum Vol. 946

Abstract: Electric current assisted sintering of β-Si₅AlON₇-TiN ceramic composites from raw materials prepared by combustion synthesis was investigated. A high level of relative density (92% and higher) was achieved by using of two types of electric current assisted sintering technique: high voltage electric discharge consolidation, as well as spark plasma sintering. While only spark plasma sintering, it may be considered as promising technique for obtaining ceramic composites and items with high level of strength properties.

Abstract: The results of the preliminary heat treatment effecting in a medium with a high oxygen content on the microstructure and mechanical properties of structural steels are presented. It is shown that the usage of preheating in the glass mass in the range of (A_c130°C) – A_c1 for steels of grades 50 and 40H leads to the formation of a structure with dispersed granular pearlite and crushed excess ferrite precipitates. Such a structure, when heated for quenching, provides rapid formation of a homogeneous austenite and a delay in the growth of austenite grain, which provides the best combination of strength and plasticity after the final heat treatment. It is established that the tensile strength increases 1.2-1.3 times while maintaining the plasticity characteristics. The reliability of the obtained estimates of the mechanical property characteristics is confirmed by the results of a statistical analysis.

Abstract: Four model alloys of the Fe-Cr-Co system have been tested under elongation at a standart rate and under pure bending with a constant load in air and in a corrosive medium after different treatment. Fractographic studies were performed depending on the cobalt content and duration of thermal aging at 450 °C. The experiment results are that the Fe-Cr-Co-based alloys with 5–10 % of cobalt are an acceptable composition for maraging steels since they have high strength and ductility, as well as corrosion resistance and low sensitivity to stress corrosion cracking.

Abstract: Properties of parts after a shot-blasting of a surface are investigated. Change of size of compression stresses in a surface layer of the cemented tempered parts processed by different compositions of materials in shot blasting units is shown. After shot jetting peening of parts increase in a limit of endurance for 40 – 60% is reached. The maximum effect at a shot jetting peening of toothed parts is reached when using for a shot blasting of the mix consisting of steel chopped fraction and glass balls.

Abstract: Pitting and crevice corrosion resistance of 321 stainless steel and non-vacuum electron-beam cladded stainless steel have been investigated by using potentio-dynamic polarization curve plotting. Lock-Ringer Salt Solution (LRSS) was used as biological media for corrosion test measurements. Microstructural research of samples after corrosion was carried out by using scanning electron microscopy. The experimental results show that the cladded stainless steel possesses higher pitting and crevice corrosion resistance.

Abstract: The paper presents the design of the etching unit, the experiment procedure to remove a thin surface layer of metal and fixing the elastic discharge of the pipe along its length. The value of elastic discharge is necessary to calculate the residual stresses of a thin surface layer, as well as the distribution of residual stresses of the pipe wall.

Abstract: In our work we defined two directions for synthesizing porous material: pulping selected experimental glass compositions and using caustic soda as a foaming agent. We studied the foaming temperature settings, investigated the porous material properties. The intensity of the foaming process was estimated from the value of the foaming coefficient.

Abstract: This study explores structure and characteristics of the nickel-chrome steel of the Cr-Ni-Mo-Mn-Si-Ti-Nb-B doping system obtained by surfacing with a flux-cored wire alloyed by boron carbide. It has shown that the deposited metal has a composite structure consisting of a supersaturated with alloyed elements solid solution with an austenite-martensitic matrix and a eutectic component (Mo, Cr, Fe, Nb)₂B in the form of sections along the boundaries of former austenite grains. Because of the significant content of ferrite-forming elements in the process of crystallization, a metastable δ-ferrite is formed in the weld metal in the form of differently oriented interlayers between the martensite rails. As a result of aging of such a deposited metal at 500 °C for 2 hours, the metastable ferrite undergoes decay at the interphase boundaries α/δ with the formation of the σ phase, which represents sharpened plates with the size of 300÷550 nm. Moreover, aging leads to hardening of the matrix by finely dispersed carboboride and intermetallic phases (Cr, Mo, Fe, Nb, Ti)₂₃(С,В)₆, (Fe, Cr, Si)₂(Mo, Ti) и (Ni, Fe)₃Ti, causing high levels of hardness and wear resistance. The usage of this wire as a surfacing material allows to increase significantly the operability and reliability of the stop valve parts, which work on abrasion in contact with corrosive medium.

Abstract: The paper discusses the important issues concerning recycling of industrial sulfur waste and bottom ash. The process flow diagram was designed to form protective coatings on cement concrete by impregnation with molten sulfur, which featured high strength, performance properties and corrosion resistance. The process parameters were specified. The addition of bottom ash slag to cement concrete not only offers a means for recovering waste from thermal power stations, but also increases the material strength. Besides, the impregnation process provides low thermal conductivity for concrete while giving the material high heat insulation. A higher strength of the samples containing bottom ash slag results from a high dispersity and reactive surface of bottom ash slag. The paper investigates the influence of the electrophilic agent (aluminum chloride) on the properties of sulfur binder. It was shown that addition of aluminum chloride encouraged the formation of a more effective protective coating that gave the samples of cement concrete higher strength, density, water resistance. The electrophilic agent stimulated the synthesis process for inorganic sulfides and composite materials based on them. It was found that addition of the electrophilic agent (aluminum chloride) reduced the viscosity of molten sulfur significantly, which was attributed to the formed short-chain sulfur radicals. Such a melt has a relatively high penetration capability to ensure the formation of a high-quality protective coating.

Abstract: Polyethylene is widely used in the production of products for the automotive industry, due to the unique properties and the possibility of manufacturing hollow products of complex geometry. In this work the thermal research of polyethylene in finished productsand the quality assessment of autocomponents materials, depending on the type of polyethylene were conducted. An assessment methodologyof the material of products is suggested, which indicates the difference between the batches of autocomponents products for the acceptance or rejection thisbatch by conducting DSC-analysis. It was found that the products of autocomponents, in particular, "splash-absorbing shield", based on LDPE with a melting point above 110 °C have unsatisfactory performance characteristics. It is shown that modifying additives to improve the elasticity of the LDPE lead to partial the amorphization of PE, that is, a decrease in the degree of crystallinity by 4% relative to the LDPE without additives.