Key Engineering Materials Vol. 836

Abstract: The article discusses the experience of drilling and blasting operations in the conditions of high water cut of the rock massif, it also presents practical experience in modeling and forecasting water inflows into workings. By the example of the Koashvinskoe deposit, the problems of work in conditions of high water cut of the rock mass leading to the collapse and silting of drilled boreholes are considered. The article presents calculations showing the effectiveness of the drainage systems for lowering the groundwater level of a prepared rock mass section. The paper provides a rationale for the optimal mass of bottom charges for the preparation of drains in the rock mass, depending on the water saturation of the mass and the grid of drilled boreholes.

Abstract: The article presents the results of studies of steel strength of K70 (X90) class. The investigated semi-finished products were graded by their repair ability (by the number of allowed repeated local heating of the material during repair). The gradation is made from the condition of the reduction of metal viscosity in the overheating zone, determined by the magnitude of the impact of Sharpy samples at the temperature of 40 °C below zero.

Abstract: The paper deals with modern designs of crankshaft bushings used in internal combustion engines. It delineates the prospects of polymer coatings to ensure additional protection of lead bronze bushings in the event of emergencies associated with a temporary loss of lubrication. For this purpose, a polymer composition of silicone polyorganosiloxane and fluoro-epoxy lacquers is proposed. Tribotechnical results are provided for polymer-coated bushings: 1) in a full-film lubrication condition, 2) in boundary conditions (with lubricant residues once the unit has been switched off) and 3) in dry conditions (with no lubrication after a long standstill). A thin-layer (3...5 μm) polymer coating based on polyorganosiloxane and fluorine can be used on the bearing surfaces of the shells of highly loaded bearings in order to increase antifriction properties, especially with limited lubrication and possible scores in a bearing.

Abstract: According to the dynamic characteristics of the electrochemical system, according to V.F. Molchanov, it is possible to optimize the composition of chroming electrolyte and predict the properties of chromium deposits depending on the mode of deposition and the transition time. The possibility of using the transition time for the formation of the cathode surface colloid-dispersion film to study the chemical composition of the chroming solution is considered. The chemical composition can be optimized by the position of the maxima and minima on the polarization curves. An electrochemical cell can be described as a system by a differential equation, the form of which is determined by its internal structure, which varies with electrolysis conditions. The properties of the system are evaluated by a number of factors: the time of the transition process, forcing, attenuation, and the quality factor. This approach is used to develop a low-concentration chroming electrolyte with organic additives. Analytical dependences of chromium yield on current, micro hardness, roughness and deposition rate on deposition conditions are obtained. Chroming on non-stationary modes allows the most effective influence on the structure and physical-mechanical properties of coatings. When changing electrolysis parameters, it is possible to influence the structure and physical-mechanical properties of coatings, to obtain various functional chromium coatings with specified characteristics (adjustable micro hardness in thickness, porosity, internal stresses, corrosion resistance, wear resistance, roughness) from a single electrolyte. The use of a low-concentration electrolyte together with non-stationary deposition modes makes possible to increase the chromium current yield, covering and dissipative ability of the electrolyte, deposition rate, producibility and environmental friendliness of the process, and to reduce hydrogenation. The electrolyte with crystal violet additives has an increased current output (up to 28 %), an extended range of obtaining wear-resistant coatings up to 240 A / dm², a high deposition rate of up to 2.5 μm / min, an increased micro hardness by 100-300 kg / mm², reduced toxicity, a decreased absorbed hydrogen level at 500-700 cm³ per 100 grams of chrome coating and internal stresses at 600-950 kg / mm2.

Abstract: The physical-mechanical properties of chromium coatings from low-concentrated electrolytes with additions of organic substances were studied when comparing with similar ones from standard sulphate electrolyte. It has been established that the properties of chromium coatings from low concentrated electrolytes are superior to those of standard sulphate electrolyte. An additional advantage of low-concentrated electrolytes is less carry-over of chromium anhydrate through ventilation and wash water, which reduces the cost of cleaning them when they are discharged. However, under operating conditions, more frequent adjustment of the composition of such electrolytes is required. The electrolyte is distinguished by a good scattering over the surface of parts and covering power when restored to size on a thickness of 250-300 μm of hydraulic cylinders of agricultural and mining equipment, having a length of up to 4 m and a diameter of up to 0.5 m, an increased current output of up to 24-36 % and up to 3-4 times higher corrosion resistance, micro hardness of up to 1,300 kg / mm2, determined by the conditions of deposition relative to the standard sulfate electrolyte of chromium plating. Chromium coatings from a low-concentration electrolyte with organic additives passed the recommended tests for adhesion, tearing, wear and micro hardness according to GOST methods. Their use at the enterprises of technical service for repair of agricultural parts promises economic advantages in the field of practical application (higher deposition rate and less application time), as well as lower costs for environmental protection.

Abstract: The article presents information on the technological characteristics and industrial use of chroming electrolytes. The modern electrochemical technologies of repairing worn-out parts of agricultural machinery are considered. Particular attention is paid to the use of chrome plating methods making possible to increase the durability and reliability of the parts recovered in electrolytes of different composition, allowing to obtain coatings with high physical-mechanical properties that determine their suitability for the operation in the process of use for their intended purpose. The use of self-regulating dilute chroming electrolytes makes possible to increase the productivity of the deposition process of chromium coatings significantly, to obtain high-quality coatings of chromium and iron, and high adhesion to the base material - carbon, alloyed steels, and cast iron. The deposition of metals using reverse, pulsed currents with adjustable anodic-cathodic ratio of amplitude values and its duration allows to influence electro crystallization, control the structure, texture and roughness of the formed precipitate, which makes possible to get with predetermined functional physical and mechanical properties for specific repair conditions and subsequent operation in agricultural machinery. The following modes are recommended for brilliant coatings: when reverse current τ (cat) / τ (an) = 50-70, τ (cat) = 4-7 min, D(cat) = 40-100 А / dm2, D(cat) / D(an) = 3-4, Т = 60-65 ° С; when impulse current D(cat) = 40-100 А / dm2, Т = 60-65 ° С, τ (imp) = 1.5-2.5 min, τ (pauses) = 5-10 sec., impulse ratio 1.07-1.15.