OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 At the same time, a cursory literature analysis shows that the wear resistance of Fe-Ni-Al composites is still significantly inferior to that of metalloceramic composites (MMCs). Therefore, reinforcing Fe-Ni-Al compositions with ceramic powder particles presents a promising strategy to significantly increase their hardness and wear resistance while maintaining high oxidation resistance. Tungsten carbide (WC) is often considered as a reinforcing component of MMCs due to its high hardness and good wettability with metal melts [5–7]. The Fe-Ni-Al composition exhibits exceptionally high oxidation resistance but relatively poor wear resistance, while hard tungsten carbide is easily oxidized at high temperatures. Therefore, reinforcing the Fe-Ni-Al matrix with tungsten carbide allows for the creation of a WC/Fe-Ni-Al composite coating that combines high oxidation resistance and wear resistance. According to a literature analysis, metalloceramic WC/Fe-Ni-Al coatings have previously been applied using techniques such as flame spraying [8], plasma-arc powder spraying [9], and electrospark deposition (ESD) [10]. Electrospark deposition (ESD) is a surface hardening technology that uses low-voltage, highcurrent electrical discharges to melt and transfer material from the working electrode to the substrate surface, significantly increasing the surface hardness and wear resistance. ESD technology offers notable advantages such as process simplicity, low cost, low residual stresses, and minimal substrate deformation, making it a highly effective method for producing coatings on metals and alloys [11]. The high temperature generated during the spark discharge process melts the electrode material, resulting in a uniform and dense coating, and the metallurgical bond ensures high adhesion of the coating to the substrate. The ESD method is employed in various applications: to improve the physical and chemical properties of metallic materials by applying refractory metals and their compounds; to expand the scope of application of composite materials by creating wear-resistant and oxidation-resistant layers on their surface; and to alter the chemical and phase composition of the surface in a controlled manner by processing in the presence of a reactive gas (e.g., nitriding of a titanium alloy) [12]. The use of a non-localized electrode (NE) for ESD facilitates the automation of the coating application process, including on curved parts, and enables the use of powders as the primary coating constituent [13]. In a previous study, WC/Fe-Ni-Al coatings with a high ceramic content were produced by the ESDNE method using a NE consisting of nickel and aluminum granules, and αWC powder with an average particle size of 1 μm [10]. In the field of compact WC-Co metalloceramic materials, the particle size of tungsten carbide has a significant effect on the hardness and strength of sintered products [14, 15]. However, the influence of the WC powder particle size on the properties of metalloceramic coatings has not been systematically investigated. Aim of the study is to investigate the influence of the particle size distribution (granulometry) of the initial WC powder introduced into the non-localized electrode on the kinetics of mass transfer, chemical composition, cross-sectional structure of WC/Fe-Ni-Al coatings, and their corrosion and tribological properties. To achieve the stated aim, the following tasks were accomplished: – preparation of various tungsten carbide powder fractions via grinding in a planetary ball mill and sieve analysis; – investigation of the influence of the particle size distribution of the initial tungsten carbide powder used in a non-localized electrode on mass transfer, composition, and structure of the coating; – establishment of the relationship between the coating’s structure and its properties: roughness, wettability, hardness, wear resistance, and oxidation resistance. Methods The working electrode for the ESD was a non-localized electrode consisting of iron granules and Ni, Al and WC powders (Table 1). Iron granules were obtained by cutting welding wire (SV-08AA) with a diameter of 4±0.1 mm into cylinders with a length of 4±0.5 mm. The tungsten carbide powder fractions ranged from 80 nm to 40 µm. The most dispersed fraction was nanostructured WC powder (99.95%) with an average particle diameter by volume D [4.3] of 0.8 μm, produced by Hongwu (China) (Fig. 1, a, b).
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