INCREASING THE RESOURCE OF WORKING PARTS OF SOIL CULTIVATION EQUIPMENT BY OPTIMIZING THE COMPOSITION OF POWDER WIRES FOR ELECTROSLAG SURFACING

Abstract

The article substantiates an approach to increasing the service life of working parts of soil cultivation equipment by rationalising the composition of powder (electrode) wires for electroslag surfacing in a current-supplying crystalliser with constant reverse polarity current. For ten experimental wire compositions, a comprehensive assessment of the properties of coatings was carried out according to the following indicators: hardness (HRC), abrasive wear (mass loss Δm, g) and corrosion resistance (mass loss Δm, mg after 72 hours in 5 % NaCl). In addition, the technological stability of surfacing and the tendency of layers to porosity and cracking were analysed. A formalised multi-criteria selection procedure was proposed based on the integral quality index K, which aggregates the normalised criteria of ’hardness–wear resistance–corrosion resistance’ and takes into account the technological limitations of the process (slag bath stability, heat input control, defect minimisation). According to the integral ranking, the most balanced operational properties were provided by wire No. 6, which was accepted as the basic prototype. The effectiveness of carbide-oxide modification (NbC, ZrO₂, Al₂O₃, graphite) in combination with high chromium alloying for the formation of a dispersion-strengthened and technologically suitable structure is demonstrated. The recommended composition range for powder wire for wear-resistant coatings is: Cr 50–60 %, C 3–4 %, NbC 5–8 %, ZrO₂ 5–10 %, Al₂O₃ 5–7 %, graphite 2–3 %, microimpurities V and Mo 1–2 %. Field tests on ploughshares and cultivator tines confirmed a reduction in wear of approximately 40 % compared to serial parts. Technical and economic justification for 1,000 hectares showed a reduction in direct costs from 42,800 UAH to 29,276.8 UAH and savings of 13,523.2 UAH (31.6 %), confirming the feasibility of introducing the proposed wire compositions in repair production and service departments. Practical value – reproducibility of compositions on standard workshop equipment.