Vol 2019, No 13 (2019)

The shapes and the sizes of metal oxide particles in polymer-stabilized disperse systems subjected to mechanical activation are considered. The digital processing of images of metal oxide particles is used to determine the parameters of the particles and the adsorbed polymer layers and to find the density change dynamics in an adsorbed layer.

An indentation technique for measuring and comparing the microhardness of hardening coatings, which takes into account the scale factor, is proposed and explained. This technique is experimentally shown to be more valid in terms of estimation and comparison of the microhardness of thin hardening coatings.

The contamination of the recirculated powder, namely, the material retained after the selective laser sintering of VZh159 and EP648 alloys, is studied as a function of the geometry of a part. The contamination of the recirculated powder is shown to depend mainly on the complex geometry of the part with a long perimeter of its contours and supporting elements rather than on the area of the section to be sintered. The main source of the contamination of the recirculated powder is represented by ejected particles, i.e., secondary granules, which form during a local microexplosion in the focal laser spot on a powder layer. The laws of ejection formation during synthesis are determined as functions of the type of part element to be synthesized.

Test flux-cored wires for arc spraying technology are developed. Tantalum and tungsten powders are selected as modifying additives. A PGSR-4 (Ni–Cr–B–Si) commercial powder is the basis of the powder material. The structure of the modified coatings is studied by metallographic analysis. Wear tests of the modified coatings are performed by slipping friction. The friction coefficients and the roughness characteristics are measured.

The deformation characteristics of silica fabric with a thermal barrier coating, which is used for the production of the ballute-type aerobrake of a descent module, are estimated. A rubberized fabric strip is subjected to uniaxial tensile tests to failure. Various finite-element simulation approaches to the deformation of the fabric are considered.

Two technologies of single-part production of layered composites are considered, the main technological operations are normalized, and the properties of the prepared materials are considered. A nonwoven material with a honeycomb structure is used as one of the components of the layered composite material. The properties of the nonwoven material, foam plastic, honeycomb fillers, and spheroplastics are compared. The total time of impregnation of a layered composite material is theoretically and experimentally studied.

The influence of technological heredity factors on the quality indices of parts and products made of polymer composite materials is considered. A technique is developed to take into account the technological heredity factors using the theory of catastrophes. To formalize the technological heredity factors, we propose to use logical functions to form models to predict the change in the quality of a structural material during the entire life cycle of a product. The proposed models can be used to estimate the fracture kinetics for many materials qualitatively.

Ultrajet diagnostics is used to analyze bimetallic knives for rotary crushers, and a polymer powder is introduced in a jet to imitate the operating conditions of the equipment. The correlation between the cavern depth formed during ultrajet action on a knife and the geometric parameters of the wear of its cutting edge is shown to be high.

Some theoretical concepts about the internal stresses in an elastic coating and ways for relaxing of them are reported. These concepts are used in predicting the physicomechanical properties of nickel–phosphorus coatings. The role of surface curvature of a coated component and the layer thickness and the effect of heat treatment on the internal stresses after nickel-plating are considered. Moreover, the effect of heat treatment on the adhesive strength of coating, its wear-resistance, hardness, and fatigue strength is studied.

A promising method of corrosion protection of steel parts in chemical engineering is a gas-phase coating, which has a high density and chemical stability to the influence of fluorine and good adhesion to substrate over entire coating area even for parts of complex shapes. The characteristics of the static and fatigue fracture of BSt.3sp, 40, and E10 steels are considered after coating with gas-phase nickel of different thicknesses (5, 10, 20, 50, and 100 μm) at various substrate temperatures (130, 160, 180, and 200°C). The gas-phase nickel coating 30 μm thick of steel parts can be considered useful due to its high chemical stability and the simplicity of the technological process in spite of some decrease in the mechanical characteristics.

The nitriding of a grade 45 carbon steel with a zinc-filled coating (ZFC), which was preliminary formed by cold galvanizing, is considered. The microstructure and the chemical and phase compositions of the modified layer are studied experimentally. It is found that the nitriding leads to the formation of a transition zone in the steel substrate, which is located under ZFC and results from the diffusion of zinc and nitrogen in iron.

The life cycles of products made of metal and polymer composite materials are considered, and their common and distinctive features are determined. Using the mirror of a space antenna (made of carbon-filled plastic) as an example, we analyze the influence of auxiliary materials on the quality indices. A technique is developed to determine the influence of auxiliary materials on the phase composition (polymer matrix content is determined by thermogravimetry). A structure for forming carbon-filled plastic products using vacuum infusion and a system for the implementation of competitive design-technological solutions are presented for the manufacture of carbon-filled plastic products.

The structure formation in corrosion-resistant steel during laser melting is studied. The results of investigation of the morphology and the granulometric and chemical compositions of a CL20ES steel powder, which was prepared by melt dispersion with a high-pressure inert gas, are reported. It is shown that samples characterized by the highest density and microhardness are prepared using a converging laser beam.

The methods of decreasing the surface wear in tribounits and increasing the service life of agricultural machines by modifying tribounits by fluocarbon surfactants are considered, and the technology of application of a protective molecular film, electrolytic fluorination, and copolymerization reaction are discussed.

The problems of optimization of the amplitude–frequency characteristics of a gas flow affecting metallic articles and blanks and the gas pulse duration are considered. This optimization ensures the required increase in the mechanical and service properties at the minimum treatment time. The influence of the gas flow velocity on these properties is analyzed.

Extruded sections with various versions of reinforcing elements are considered. In particular, a T‑shaped stringer made of an aluminum alloy and reinforced at its base is studied. A sample is reinforced by a wire placed along the stringer length. Wires made of titanium, nickel, and 30KhGSA steel were used a reinforcing material. Wires of two diameters, namely, 4 and 6 mm, are considered for each material. For each case, we performed numerical and analytical estimations of the temperature stresses in the composite stringer, which are caused by cooling from 500 to 0°C. The numerical calculation is conducted by the finite-element method with the Femap and Nastran software packages. The analytical calculation is executed using Hooke’s law with allowance for temperature terms and the Lamé solution. The stringer–core combination, where the core is inserted in the stringer without interference, is analyzed. Equivalent stress distributions in the stringer and the core are obtained for all versions under study. The strengths of all versions of reinforcing are estimated.

The challenging problem of ensuring the accuracy of sizes in bending followed by elastic springback of angle parts, which form a wide class of aircraft elements, i.e., stringers, stiffening ribs, and lattice wheel and wing elements, is considered. The purpose of this work is to develop a technique for engineering estimation of the angle error in bending an angle blank in a tool die. The proposed technique reflects the physical features of springback in bending in a tool die, is characterized by simplicity, and provides the accuracy of estimating the angular error that is sufficient for engineering practice. This technique can be used to solve a number of practical problems.

The microstructures of the weld core, the heat-deformation-affected zone, and the heat-affected zone having formed during the friction stir welding (FSW) of 12Kh18N10T steel and OT4-1 and VT-1 alloys are studied. The weld core of the solid-state FSW welded joints made of the metals and alloys that undergo polymorphic transformations is shown to form under structural superplasticity due to corporative recrystallization processes and phase transformations.

The influence of the method of machining of the edges of carbon-filled plastics on their water absorption is experimentally studied. The water absorption of composite materials is shown to depend on both the method of machining of the edges and the plastic material. The results of structural investigations demonstrate that milling is the most suitable method for machining the edges of the polymer composite material parts produced by vacuum infusion.

The methods of hardening of the chaff-cutter drum knives in a grain harvester combine are analyzed. The wear resistances of 65g steel samples hardened by quenching and borating and heating by high-frequency currents are compared. The results of field tests of the hardened knives are presented. These results are used to propose a design for a hardening coating. A two-coil induction heater is suggested for simultaneous heating of both face edges of a knife.

In many cases, when metals and alloys are oxidized under the continuous regeneration of the direct oxidant taken in the amounts comparable with catalytic amounts, the near-surface layer of surface deposits of the products of oxidation of the metal and the reduction of the oxidant of the metal can be considered as a local zone of the macrocyclic stage of regeneration of the oxidant of the metal. The transfer of this stage to the volume phase is admissible and sometimes reasonable if the product of the reduction of the direct oxidant of the metal is soluble in the volume phase to a sufficient extent and the metal oxide is almost insoluble in the volume phase, where the metal exists in a higher oxidation state, or metal peroxide is used as an oxidant. If the indicated solubility of the reduction product of the primary oxidant of the metal is too low or entirely absent, its transfer to the volume phase due to the mechanical failure of the near-surface layer results in progressive self-retardation and also, in many cases, in the nearly entire termination of the oxidation process. The facts of the presence and mechanical failure of the near-surface layer on the metal and alloy favorable from the viewpoint of chemistry and technology are considered.

This article discusses the peculiar features of quality management in modern manufacturing and technological systems with consideration for risk-based thinking, in particular, which characterizes quality as a measurable and estimable factor, its indices, existing major categories of quality management, how and when they are applied, as well as their distinctive features.

The problems of the processing of sulfate lead industrial products containing noble metals, which are related to lead reduction after partial sulfidizing in an alkali melt at ~600°C followed by the extraction of the present noble metals to molten lead, are studied. The process provides deep recovery of lead and extraction of noble metals.