Inorganic Materials: Applied Research最新文献

Abstract—The structural features and microhardness in the zone adjacent to the edges of the cut during laser cutting of gear blanks from a sheet of 40Kh steel 6 mm thick were studied. The possibility of combining laser cutting with surface hardening is shown. On average, the hardened surface layer in different sections of the cut has a thickness on the order of 150–250 μm with a maximum hardness approximately equivalent to 46–58 HRC, which is quite comparable to the hardening of 40Kh steel with most surface treatments.

The results are presented for impact of defects formed during one-sided friction stir welding plates made of alloy 1901 in the root part on the mechanical properties of resulting butt joints. The defects are represented by the lack of fusion and accumulations of oxide films in the root part of the joint. The defect length is 0.1–0.3 mm and the defects are detected using computer X-ray tomography and analyzing the microstructure of the joints using an optical microscope. The defects present in the root part of the plate joints made of alloy 1901T result in decrease in the welding factor from 0.85 to 0.74. The area of the joint break during a static tensile test shifts from the heat-affected zone to the stir zone. The break of the samples exposed to static tension is initiated by a lack of fusion (the areas occupied by oxide films) in the root part of the joint with a characteristic brittle fracture propagating into the stir zone. The fracture becomes ductile with islands of oxide film entering the weld during the welding process. The presence of the lack of fusion and oxide films in the root part of the joint results in a 2-fold decrease in the joint bending angle. A necessary condition for eliminating the lack of fusion in the root part of the butt joint in plates made of alloy 1901T deals with making the length of the rod (pin) of the working tool equal to the thickness of the workpieces welded, taking into account the degree of immersion of the tool shoulder in the weld metal.

Abstract—The results of comprehensive studies of the properties of imported syringe gland materials are presented. The studied materials were identified and their domestic analogs were found.

Abstract—The technology of plasmochemical synthesis of strontium-aluminosilicate glasses using crucibles has been developed, and the features of such a synthesis are discussed. The melt is found to be enriched in strontium and aluminum oxides and depleted in silica during the plasmochemical synthesis of strontium-aluminosilicate glasses as a result of incongruent evaporation. This improves the performance of the final product. The physicochemical properties of strontium-aluminosilicate glasses are studied.

Abstract—This paper studies the chemical composition stability of modified 1 mol % CaO ceramic composites which contain 50 mol % Al₂O₃ and 50 mol % [12Ce–TZP] or 50 mol % [3Yb–TZP] and are produced from powders synthesized by a hydrolytic sol-gel method. It is shown that the content of dangerous elements, such as As, Be, Cd, Cr, Pb, and Sb, in the new composites is below the maximum allowable limits. In addition, this paper establishes the high stability in the chemical composition of the composites after a long presence in a media that simulates the conditions of the body. The mass loss for Al is no more than 5 × 10^–4 wt %; for Zr, it is no more than 1 × 10^–4 wt %.

Abstract—Gadolinium molybdate powder is produced by a mechanochemical method from a stoichiometric mixture of molybdenum oxide and dysprosium oxide. Using the XRF, TEM, and SEM methods, it has been shown that, during mechanochemical treatment for 30 min, owing to the occurrence of mechanochemical reactions between the initial powders, a fine powder of the Dy₂MoO₆ compound is formed, containing up to 8% Dy₂(MoO₄)₃. The technological properties (fluidity, compactibility) of mechanically synthesized dysprosium molybdate powder, as well as its microstructure after sintering, have been studied.

Abstract—The effect of exposures in the range of 500–10 000 h at heating temperatures of 450–750°C on changes in the structure and properties of steel 08Kh18N10T has been studied. It has been found that, in the early stages of thermal aging at 450–550°C, the precipitates of finely dispersed carbides are formed, coherent with the austenitic matrix. With an increase in the holding time and aging temperature to 650°C, the sizes of Me₂₃C₆ carbide particles sharply increase, which, under a certain combination of temperature–time parameters, evolve into the σ phase with low coherence with the γ-solid solution. However, this phenomenon has little effect on the mechanical properties at room temperature.

The issue of obtaining high-quality welds in plates made of AL9 alloy using powder through selective laser fusion is addressed. Welded butt joints in plates made of AK9 alloy having a thickness of 3.0 mm are made using welding (automatic argon arc and electron beam welding) and friction stir welding. After welding, the base metal of AK9 alloy plates and the welded joints are studied using X-ray transmission, computer tomography, metallographic analysis, and mechanical tests to get information on static tension and static three-point bending. X-ray inspection of welded joints made by automatic argon arc and electron beam welding reveals multiple porosity inside the welds. Spherical micropores formed in the parent metal during selective laser fusion act as pore nuclei inside in the weld metal. These micropores have a diameter of 150–200 µm. During fusion welding, micropores grow in diameter to 420–1070 µm in the welding bath in the case of argon arc welding and to 215–420 µm in electron beam welding. Metallographic analysis of fusion welding cross sections of welded joints reveals a characteristic pore distribution in the weld metal. In the case of argon arc welding, the largest pores are located near the front surface of the weld. The pores having a diameter of 80–220 µm form chains along the entire thickness of the welded plates in the fusion zone at the border of the weld and the base metal. It is in this zone that welded joints break under static tension. The welding factor of the AK9 alloy joints obtained by fusion welding is as follows: for automatic argon arc welding, it is 0.46; for electron beam welding, it is 0.66. It is established that the porosity issue can be eliminated in welded joints through solid-phase welding to make butt welds (through friction stir welding). The welding factor of the butt welds made in AK9 alloy plates performed by friction stir welding stays at a level of 0.81–0.86 of the ultimate strength of the base metal. The break of welded joints occurs across the stir zone. The weld zone formed during friction stir welding undergoes dynamic recrystallization resulting in forming a fine-grained equiaxial structure with an average grain size of 4.5–6.2 µm. There is almost no pores in this structure. The base metal is represented by a cell structure featuring pores up to 168 µm in size.

Technical features and examples of the practical use of technology of combined hardening treatment of steel tools are presented, which includes (1) hardening thermal cycling treatment (HTC) of tool blanks and (2) thermo-hydro-chemical treatment (THCT) of the finally manufactured instruments. THCT creates volumetric hardening of tools by thermal cycling with incomplete solid-phase α ↔ γ transformations, followed by quenching and tempering. HTC creates surface hardening of tools by boiling refractory compounds in hydrosols followed by tempering. As a result of combining THCT + HTC, the service life of cutting steel tools increased by 2–20 times, and that of die tools by 1.9–2.1 times compared to traditionally hardened tools.

Abstract—The influence of diffusion saturation of steel 20 in the medium of low-melting liquid metal melts of Pb–Bi–Li–Ni–Cu composition on its elemental composition and corrosion resistance is considered in this article. As a result of diffusion saturation, a coating is formed structurally consisting of two zones: surface and transition ones. The surface zone contains 53% Cu, 30% Ni, and 17% Fe. As one approaches the transition zone, a decrease in the concentration of Cu and an increase in the concentration of Ni and Fe are observed. In this case, the transition zone structurally consists of inclusions of Fe in a Ni-based solid solution that did not pass into solid solution. In addition, there is a layer under the coating containing C in a higher concentration than the base material owing to the low solubility of C in solid solutions of the Cu–Ni–Fe system. The coating thickness ranges from 8 to 45 μm depending on the temperature and duration of saturation. It is also found that the resulting coatings can reduce the corrosion rate of samples from 3 to 0.8 mm/year.