Investigation of the structure and properties of multilayer coatings on bronze synthesised by the electrospark alloying method

Abstract

Bronzes, particularly tin and aluminium bronzes, are widely used as antifriction materials in sliding units of machinery and energy equipment due to their combination of low friction coefficient, wear resistance, and corrosion resistance. However, their operational reliability is limited by intensive wear during the running-in period, when local overloads and surface micro-roughness lead to adhesive wear and scoring, reducing the efficiency of tribological components. The aim of this work is to investigate the structure and properties of multilayer coatings synthesized on bronze substrates by electrospark alloying (ESA) using a sulphur-containing paste. Samples of bronze BrO10S10 were treated on the "Elitron-22A" setup under various discharge energy modes. During ESA, the paste was applied before silver and tin alloying in the following sequence: paste → ESA with silver → ESA with tin → paste → ESA with silver. Surface roughness and topography were determined, and the distribution of microhardness and elements in the surface layer was analysed. The multilayer coating microstructure was studied using optical and scanning electron microscopy. Results revealed the formation of a multilayer structure: an outer layer with microhardness of 140-150 MPa, a lighter sublayer of 1250-2270 MPa, and a heat-affected zone of 778-1000 MPa. Intensive diffusion of electrode materials (Sn, Ag) and sulphur penetration into the bronze substrate were observed. The use of sulphur-containing paste enables controlled formation of structure and composition, enhancing coating adhesion. The study confirms that ESA can produce coatings with tailored mechanical properties, which is particularly important for tribological components with complex geometry and high loads. Therefore, the application of ESA with functional pastes is a promising approach for modifying bronze parts, optimizing the running-in process, and controlling surface layer properties, enabling the creation of coatings with high adhesion, enhanced wear resistance, and controlled composition for modern mechanical engineering and energy applications.