Vol 57, No 4 (2016)

Silica-free binder ALUMOX is tested under conditions of the AO NPTs Gas Turbine Construction Salyut casting shop conditions. Amethod is developed for preparing composite ceramic molds for investment casting of critical superalloy components by directional solidification. Use of these molds makes it possible to prepare castings by high-gradient directional solidification answering component drawing specifications and technical conditions. The protective layer of the composite mold based on ALUMOX binder significantly reduces chemical interaction of the mold working layer with components of superalloy ZhS26-VI during pouring and cooling compared with the degree of interaction of a standard mold based on ÉTS-40 binder.

Microstructure, phase composition, and physicochemical properties of domestic and imported carbon materials used in refractory concretes are studied. It is established that graphites of different origin have different surface morphology, crystal lattice structure, and wetting capacity.

Relative wear resistance in service of various refractories of different chemical and mineral composition is calculated theoretically. On the basis of thermal energy density values it is established that of all oxides zirconium oxide is in first place for highest refractoriness (melting temperature >2500°C). Among available refractory minerals (compounds of other chemical classes with respect to wear resistance ZrO₂ is only worse than graphite and silicon carbide (α-SiC). On the basis of research a procedure is developed, and a production line is planned, constructed, and put into operation for industrial manufacture of fuzed partly stabilized zirconium dioxide (PSZD). Zirconia-graphite submersible nozzles for a CBCM are produced using PSZD.

Any improvement in the technological processes involved in the production of ferrous and nonferrous metals, taking into account the existence of lean crude metal and of crude metal that is heterogeneous in terms of composition, should be done not only on the basis of the traditional methods that are used to reveal cause-effect relations in the processes present in the common process flow diagram accompanied by an analysis of their material and heat balances. An additional analysis of these processes is possible on the basis of Shannon information entropy in order to combine as yet uncoordinated indicators on the basis of the content and degree of recovery of valuable components in technological products on the process flow stages and, on the whole, throughout the entire process flow diagram. This is done for the purpose of conducting a comparative analysis and evaluation of the metallurgical processes. Information criteria for an exhaustive evaluation of the uncertainty and degree of completeness of the process flow diagrams of steel production are developed on the basis of an entropy information analysis of the process flow diagrams of ferrous metallurgy.

Results are provided for an experimental study of disaggregation of aluminum hydroxide (boehmite) powder prepared by hydrothermal oxidation of aluminum powder. The effect of heat treatment temperature, drying with heated steam, milling in ball and knife mills, treatment in rotary pulsating equipment, addition of surfactant on original powder disaggregation and preparation of nanostructured boehmite and aluminum oxide, are studied. Process parameters are determined for preparing nanostructured powders.

Results are provided for study of a series of high refractoriness objects for thermal shock resistance and determination of their actual heat capacity. It is shown that under high temperature conditions and sharply varying thermal loads good resistance develops for objects with the highest ratio of heated surface area to volume. Two-phase materials demonstrate the best thermal shock resistance. Periclase objects with a protective coating based on ZrO₂ have thermal shock resistance comparable with that of zirconia objects.

Conditions and mechanisms are analyzed from a materials science position for abrasive failure (wear) and synthesis of constitutional ceramic materials. A logistical block diagram is formed for physicochemical processes and mechanisms of structural engineering in technology for preparing abrasive wear-resistant materials providing successive transformation and conversion of a mineral resource (from physicochemical positions) into structural material and objects (nozzles) with a prescribed set of properties.

Results are given for a study of the effect of surface grinding regimes with diamond wheels on Al₂O₃-ceramic surface condition. A correlation is established between grinding depth, longitudinal and transverse feed with roughness, waviness, and treated surface morphology.

Research results are given for study and use of cermet electrode materials, intermetallics, materials based on MAX-phase and ceramic materials with a nanosize structure for application of protective coatings by electric-spark alloying and electric-arc hardfacing on a metal substrate. The microstructure and properties of the alloy and hardfacing layers formed, and the nature of substrate material interaction with SHS-electrodes are studied, and comparative tribological tests are performed for coating strength. Some results of industrial testing of the materials developed are provided.

The change in rheological parameters of refractory clay is shown in relation to different additive concentration. Processes of commercial grade lignosulfonate adsorption on clay particles within the composition of complex additives are considered. It is established that the amount of absolute lignosulfonate adsorption, added to a complex, is greater than with addition of pure lignosulfonate. The efficiency of using a complex containing lignosulfonate as a diluting additive for refractory clay is demonstrated.

In order to improve the sinterability and thermal shock resistance of ceramic based on MgO magnesium oxide of micron grain size composition is used as the main starting raw material with additions of nano-Al₂O₃ and nano-SiO₂. Ceramic based on MgO is prepared by adding different amounts of Al₂O₃ and SiO₂ to MgO in a molar ratio 1:4. The mixture is molded and sintered in an air atmosphere. Ceramic phase composition and microstructure are studied in an x-ray diffractometer and a scanning electron microscope. The effect of adding different amounts of Al₂O₃ + 4SiO₂ on sinterability and thermal shock resistance of MgO base ceramic is studied. Addition of Al₂O₃ + 4SiO₂ has a favorable effect on test ceramic sinterability and thermal shock resistance. During reaction of solid substances there is formation of magnesia-alumina-spinel and forsterite that leads to retardation of periclase phase grain migration. The degree of specimen compaction is improved and this has a favorable effect on sinterability of ceramic based on MgO. The degree of compaction increases as there is an increase in sintering temperature in the range 1400 to 1500°C. In addition, specimen thermal shock resistance is improved due to connection between microcracks. As a result of adding Al₂O₃ in an amount up to 30 wt.% + SiO₂ in an amount up to 45 wt.% MgO sinterability and thermal shock resistance are improved.

The effect of titanium carbide coating thickness on transformation of the stressed state of a surface layer of Si₃N₄–TiC–Y₂O₃-ceramic under action of a concentrated force is studied. It is established that an increase in TiC-coating thickness leads to an increase in stresses σ₁₁, σ₂₂, σ₁₂ and stress intensity σ_i within a nitride ceramic surface layer.