Inorganic Materials: Applied Research最新文献

Abstract—The effect of thermal treatment on the microstructure, phase composition, and microhardness of Ni + B₄C composite coatings is studied. The coatings are deposited onto the surface of an austenitic steel by cold gas-dynamic spraying. The initial coating is shown to be a nickel matrix containing distributed B₄C particles. Thermal treatment causes diffusion processes in the coating, which results in the formation of Ni₃B and Ni₂B compounds. The average microhardness of the initial coating is 3.4 GPa, and heat treatment results in an increase in the coating microhardness due to the formation of hard nickel borides.

Abstract—The acoustic emission signals that arise during the interaction of metal zirconium samples with hydrogen, as well as the changes that occur in hydrogenated samples and are sources of high-amplitude acoustic signals, are studied. Hydrogenation of pieces of compact zirconium iodide ranging in size from 5 to 10 mm, shavings obtained from compact zirconium iodide with a linear particle size from 2 to 3 mm and a thickness of ≈0.2 mm, “coarse” electrolytic zirconium powder with a fraction from 80 to 550 μm, and “fine” electrolytic zirconium powder with a particle size of less than 80 μm is carried out. It is established that the source of high-amplitude acoustic signals in all cases is the cracking of zirconium particles at the macro level, which leads to the formation of extended cracks and fractures on the surface of individual particles, as well as to the grinding of the initial materials. Cracking and grinding are caused by deformation and internal stresses that arise in the samples owing to an increase in the volume of the solid phase during hydrogenation. It is shown for the first time that the atomic ratio [H]/[Zr] in the solid phase corresponding to the maximum amplitude of the acoustic emission signal naturally increases in the series pieces of compact zirconium iodide–shavings of zirconium iodide–"coarse" electrolytic zirconium powder–"fine" electrolytic zirconium powder, which is in good agreement with the results of earlier similar studies carried out on the hydrogenation of titanium metal samples.

Abstract—The antifriction properties of fabric carbon-carbon composites paired with silicon carbide ceramics were studied under dry friction conditions. The influence of the reinforcing fabric orientation, it’s composition and heat treatment on the friction coefficient and wear rate of the composite was studied. The features of composite friction and wear mechanisms were studied for different contact configurations and different material properties. The features of friction and wear mechanisms of the composite were revealed for various contact configurations and material properties; the characteristic mechanisms of frictional surface destruction were found for individual structural elements (individual fibers, threads, layers of reinforcing fabric). The optimum reinforcement parameters for the antifriction properties of the composite were determined.

Abstract—The paper presents the results of a study of selective laser melted samples of 1CP ferromagnetic alloy powder and a mixture of 1CP and copper powders using the same set of process parameters. Optical microscopy, X-ray diffraction analysis, and differential scanning calorimetry provided the data on the macrostructure, phase composition, and degree of amorphization of the samples. The results of the study can be used for further research and development of technology for manufacture of soft magnetic composites via selective laser melting.

Abstract—The emergence of a thermionic field in a process mixture under thermal diffusion chromium plating has been established. It has been shown that some oxide compounds contained in a process mixture participate actively in the emission process. A cell for measuring emission currents and the temperature of their occurrence upon heating has been designed. The contribution of the electric emission field upon saturation of parts during thermochemical treatment has been determined in comparison with the contribution of the concentration field.

Abstract—The effect of mechanical and tribological properties of Al₂O₃ nanocomposite ceramics depending on the graphene content is studied. The samples are obtained using plasma-spark sintering in the solid state at a temperature of 1550°C. The friction of sintered samples without graphene and with a graphene content of 2 wt % is carried out according to the ball–disk scheme at room temperature without lubrication. It is shown that graphene reduces the coefficient of friction and wear. The dependence of microhardness on graphene content is constructed. The sample with a graphene content of 1% has the highest microhardness.

The results are given for impact of defects in the deposited layer on the durability of melted samples made of 08Kh14N5M2DL steel grade operating under conditions of friction at heating temperatures up to 800–900°C and under significant loads in the tribological contact zone. Defects in the deposited layer are represented by pores, the lack of fusion, and fractures. The defects inside samples undergoing friction tests are determined using X-ray computer tomography. It is found that the wear resistance of the surfacing layer without defects decreases both with growing test temperature and with increasing load applied to tribological contact. The presence of a microfracture pattern inside the deposited layer is crucial to dramatically decrease wear resistance. The presence of porosity in the deposited layer affects the wear to a lesser extent.

Abstract—The microstructure, phase composition, and oxidation resistance of as-cast high-entropy alloys (HEAs) Al_0.25CoCrFeNi and Al_0.25CoCrFeNiCuAg_x (x = 0, 0.1, 0.2) have been studied. Oxidation was carried out at 700°C for 50 h in air. During the experiment, curves for the dependence of the specific weight gain on the exposure time were plotted. It has been shown that the introduction of copper has a slight effect on the resistance of the base Al_0.25CoCrFeNi HEA to oxidation, while additional (to copper) alloying with silver worsens the resistance of the samples to high-temperature gas corrosion.

A two component Al–Ba system has been studied in which intermetallic compounds are formed that are stable at temperatures above the melting points of both barium and aluminum. This allows us to consider barium as a promising alloying element for aluminum alloys operating at high temperatures, which is also characterized by relatively high vapor pressure. Widespread use of aluminum–barium alloy in various fields of metallurgy for the preparation of alloys and complex modification of steels and cast irons, where aluminum improves the quality of steels, acting as a reducing agent for iron in its oxide compounds, and barium promotes the graphitization of cast irons, leads to improved structures of pearlitic and ferritic compounds. Taking into account the high vapor pressure of Ba in the aluminum–barium system is necessary when analyzing compositions in pressure–temperature–composition coordinates (p–T–x state diagrams), which can be used in the development of ternary or higher alloys containing aluminum and barium.

Abstract—Experiments were carried out on the treatment of nanopowders of the W–C–Co system obtained by plasma-chemical synthesis in a microwave electromagnetic field with a frequency of 2.45 and 24 GHz in different gas media. The effect of treatment time, power input, and carbon content in the treated nanopowder on the yield of tungsten monocarbide WC was investigated.