Vol 2018, No 11 (2018)

The problems of using the oil-bearing leucoxene ores of the Yarega deposit as raw materials for the production of titanium and pigment TiO₂ are discussed. The results of the investigation of two variants of the technological process predicting the preparation of artificial rutile (for processing by the chloric method) and anosovite (for sulfuric acid decomposition) with the accompanying preparation of synthetic wollastonite are presented. The developed process includes reducing roasting of a leucoxene concentrate under various conditions, magnetic separation for the removal of free quartz, and chemical desiliconization of the magnesium fraction (siliceous titanium concentrate) to form the end products.

The layer-by-layer structural and texture ingomogeneities of hot-rolled 55KhN2MA-Sh steel sheets are studied by X-ray diffraction. Hot rolling of the steel forms a substantial layer-by-layer texture inhomogeneity in the sheets: the {112}\(\left\langle {111} \right\rangle \) and {110}\(\left\langle {112} \right\rangle \) texture components prevail in the external layers in the sheets; the {100}\(\left\langle {110} \right\rangle \), {112}\(\left\langle {110} \right\rangle \), and {554}\(\left\langle {225} \right\rangle \) texture components prevail in the central layers; and texture is very weak in the intermediate layers. The crystallographic texture is shown to influence the anisotropy of the mechanical properties of the sheet. The layers with different crystallographic textures are found to exhibit different mechanical properties and different anisotropy coefficients. The anisotropy of the properties is characteristic of the central layers, and it is less pronounced in the external layers of the hot-rolled sheets.

The magnetic hysteretic properties of an Fe–27Cr–10Co–1Mo (27Kh10K1M) magnetic hard alloy are studied. Residual induction B_r (up to 1.36 T), coercive force H_cB (up to 45.4 kA/m), and maximum energy product (BH)_max (up to 44 kJ/m³) have been evaluated using the Statgraphics Centurion XVI software package after optimum heat treatment. The obtained data are higher than those of a commercial iron–chromium–cobalt 25Kh15KA alloy (Russian Standard GOST 24897–81) by 15–20% on average. Different optimum heat treatment of the alloy is shown to be required to obtain the optimum values of its residual induction B_r, coercive force H_cB, and maximum energy product (BH)_max.

The morphology of the intermetallic phases and their contents in the welded joint zones of a V‑1469 alloy (Al–Cu–Li system) are studied by X-ray diffraction and transmission electron microscopy. Welding is shown to change the phase composition, the crystallographic texture, and the microhardness of the alloy. According to quantitative X-ray diffraction analysis, the T₁-phase content decreases and the δ'-phase content increases in the weld metal. As a result, the microhardness in the weld zone decreases, since the T₁ phase is much stronger hardener than the δ' phase. This effect weakens when the weld root is approached.

The structures of the scale and the subscale layers that form during the air oxidation of the β + γ' + γ alloys of the Ni–Al–Co system containing (at %) ~27 Al (alloys 1–3), 10 Co (base alloy 1), 16 Co (alloy 2), and 10 Co and 4.25 Cr (alloy 3) at 1300°C for 100 h are studied. The formation of scale (Al₂O₃) in all alloys leads to the aluminum depletion of the subscale layers and to the γ' → γ + γ' transition due to the interdiffusion of aluminum and oxygen. An increase in the cobalt content from 5 to 10 at % increases the heat resistance. The degradation of the heat resistance induced by an increase in the cobalt content to 16 at % is related to an increase in the volume fraction of the γ phase in an alloy as compared to the base alloy with 10 at %. The introduction of small amounts of chromium degrades the heat resistance because of the development of internal oxidation, i.e., the penetration of alumina into an alloy along interdendritic γ-phase precipitates. The heat resistance of the chromium-free β + γ' + γ alloy with 10 at % Co at 1300°C, which was estimated from the sample mass increment per unit surface area in 100 h, is higher than the heat resistance of the well-known γ' + γ VKNA and VIN alloys at 1100–1200°C.

The thermal stability and the heat resistance of TiAlN–Cu and TiAlN–Ni coatings are studied. The phase compositions of the coatings are found to be unchanged upon annealing at temperatures up to 700°C in a vacuum of 10^–5 Pa. As the annealing temperature increases to 800°C, the lattice parameter of the nitride phase increases to near-stoichiometric TiN_x, the microstrains decrease, and the coherent domain sizes increase. The calculated diffusion coefficients of oxygen in the coatings upon heating in the temperature range 600–800°C demonstrate higher protective properties (high-temperature oxidation resistance) of the TiAlN–Ni coatings as compared to the TiAlN–Cu coatings, which is caused by the formation of a barrier layer based on NiO, TiO₂, and TiNiO₃ oxides.