INCREASING THE OPERATIONAL STABILITY OF WORKING PARTS OF SOIL CULTIVATION EQUIPMENT BY ELECTROSLACK SURFACE COATING WITH COMPLEX MODIFICATION OF THE COATING COVERINGS

Abstract

The article discusses a comprehensive approach to improving the operational stability of working parts of soil cultivation equipment operating under conditions of intense abrasive and impact-abrasive wear. The object of study is plough blades and cultivator arrow-shaped tines, restored by electroslag surfacing in a current-fed crystalliser with the formation of thick surfaced layers and the use of powder wires, the mixture of which contains complex modifying additives based on chromium carbides, niobium carbide and aluminium oxide. The study is structured as a closed loop ‘structure – microhardness – wear resistance – service life – economics, which allows tracing the entire chain of transformations from the micro level to practical technical and economic results. The design and principle of operation of the current- conducting crystalliser are described, a technological diagram of the electroslag surfacing process of working parts is presented, and the choice of the thickness of the surfaced layers is justified, taking into account the conditions of their operation in the soil. Based on structural, electron microscopic and optical-mathematical studies, it has been shown that the use of complex- modified powder wires provides a transition from a coarse-grained martensitic matrix with local clusters of coarse carbides to a fine-grained structure with a uniformly developed dispersed carbide framework. According to the hardness and microhardness distribution maps, it has been established that complex modification with Cr carbides, NbC and Al₂O₃ increases the hardness of the surface zones by 15–20 % compared to unmodified coatings, while the hardness gradient across the layer thickness decreases, indicating better deformation compatibility of the coating with the base metal. The results of laboratory tests for sliding abrasive wear are summarised in the form of a ‘hardness-wear resistance’ diagram, which shows an increase in the relative wear resistance of complex-modified coatings by 2.2–3.1 times compared to the base deposited metal. Field tests of refurbished ploughshares and cultivator tines in heavy, stony soils showed an average increase in their service life of 35–40%, and for optimal powder wire compositions – up to 85–100% compared to new serial parts without restoration. A technical and economic assessment showed that it is possible to reduce the total costs of repair and maintenance of soil cultivation equipment by almost 40% by reducing the number of replacements of working parts, reducing machine downtime and making more rational use of metal resources. It has been shown that the developed technology of electroslag surfacing with complex modification has significant resource-saving potential and can be adapted to the restoration of other parts that operate under conditions of intense abrasive and impact-abrasive wear.