Equipment for the production and transportation of bulk agricultural materials operates under extremely difficult operating conditions, is exposed to abrasive particles of the processed material. Such working conditions lead to changes in operational properties, deterioration of the technical condition of the equipment and the occurrence of malfunctions, which are expressed in changes in the original shapes, sizes, weight, structure of the material and mechanical properties. (Research purpose) The research purpose is to predict the performance of composite coatings using a mathematical apparatus that adequately describes the process of abrasive wear of the contact surface of the grain conveyor auger when working with abrasive particles of the processed material. (Materials and methods) As a sample for modeling the process of surface wear, authors chose a screw conveyor, the working screw surface of which is treated with plasma spraying in order to increase its wear resistance. The screw works in an abrasive environment, without touching by the contact surface with other bodies. External abrasive wear is characterized by the presence of scratches or cavities oriented in the direction of sliding. The article presents the model of abrasive wear of the grain conveyor screw and numerical methods of its calculation. (Results and discussion) The article describes a method for assessing the wear resistance of restored shafts by determining the wear intensity of the surface of the part and the energy intensity of linear wear for parts with non-stationary geometry. The article presents a method for calculating the shape and contact area of composite particles with the recovered surface. The obtained expression is valid when ensuring the deviation of the screw speed during the test from the nominal one, not exceeding 10 percent of the set value, the error of applying the load on the screw does not exceed 5 percent. (Conclusions) As a result of the study, the article presents the dependence of the intensity of abrasive wear as a function of the geometry of the surface to be restored and the density of the applied material.

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One of the most common reasons for the failure of hydraulic drive systems for agricultural machinery is the working fluid leak in the contact points of the rubbing surfaces of hydraulic blocks. The application of composite coatings based on chromium on the contacting surfaces allows you to restore the defect in the shape of the part caused by wear, as well as reduce the friction coefficient at the contact points, which positively affects the wear resistance of the part. (Research purpose) The research purpose is in developing technologies for restoring parts of agricultural machinery with predetermined operational properties. (Materials and methods) A servo valve, widely used in various hydraulic drive systems, was used as an experimental sample. Its working surface was restored with a composite coating applied by electroplating to increase the wear resistance of the servo valve. (Results and discussion) Authors conducted a series of direct measurements under the same conditions. The article presents the de-pendence of the microhardness on the parameters of the electrolysis mode and the thickness of the applied coating using the method of least squares. The nature of changes in microhardness and residual stresses was evaluated to determine the quality of the coatings. The article presents the dependences of these indicators on various control parameters (current density, temperature, tool pressure). The equations of the regression of the main qualitative and accuracy characteristics of the parts were deter-mined using the apparatus of the theory of experimental planning. (Conclusions) The article presents the method for predicting coatings of a given quality, taking into ac-count the influence of the current density and the temperature of the electrolyte during electrolysis on the nature of the precipitation obtained. The influence of the tool pressure on the depth of deformation of the formed layers was estimated. This approach allows us to evaluate the nature of the stress distribution in the formed coating and the quality of the restored parts.