OBRABOTKAMETALLOV Vol. 27 No. 2 2025 technology while the influence of pulse-on time and magnetic field strength was insignificant. Analysis of the surface microstructure using scanning electron microscopy (SEM) showed that a white layer with a thickness of up to 20 μm formed on the BeCu alloy after EDM, with minimal number of surface cracks [33]. Powder-mixed electrical discharge machining (PMEDM), as a promising machining method for difficult-to-cut alloys, particularly beryllium bronze (BeCu), is also being considered. The addition of fine powder particles to the dielectric fluid in PMEDM promotes increased machining efficiency and stability, as well as an increased concentration of spark discharges. A copper electrode was used in the experiments with constant pulse-on time, pulse-off time, and gap voltage. The gap current (ranging from 8–14 A) and powder concentration (2–6 g/L) were varied. The results showed that increasing the gap current and powder concentration leads to an increase in MRR. However, the worsening of flushing conditions at greater depths led to an increase in TWR [34]. In addition, the methods of manufacturing and processing beryllium bronze (BeCu)-based composite materials were investigated. The composite materials were fabricated using a stir casting, and their properties were evaluated using SEM and EDX methods. It was found that increasing the silicon carbide (SiC) particle content leads to an increase in material hardness. Abrasive waterjet machining (AWJM) was used to evaluate the machining performance of the composites, assessing MRR and hole circularity. The obtained parameters were compared with those obtained during EDM. ANOVA allowed for the identification of the most significant factors influencing the machining process, and the Taguchi method was used to optimize the parameters for achieving high productivity and accuracy [35]. The presented research stands out due to its novel approach to studying the peculiarities of the EDM process for three different materials: a shape memory alloy (NiTi), a monel alloy (NiCu), and beryllium copper alloy (BeCu). Special attention is paid to the difficulties encountered in processing these materials, due to their resistance to strength loss, thermal effects, and mechanical impacts. The results of the research can be valuable in industries such as aerospace, biomedical, and tool manufacturing. The significance of the work is determined by the comprehensive approach, combining investigations of EDM characteristics for specific materials, multi-criteria optimization, and experimental verification, all of which are aimed at improving high-performance machining methods. Materials and Methods The primary purpose of this research was to identify optimal combinations of EDM parameters to achieve maximum productivity. The varied parameters included: workpiece material conductivity (S/m), gap current (A) and voltage (V), pulse-on time (µs), and pulse-off time (µs). The key output parameters characterizing process performance were material removal rate (MRR), surface roughness (SR), and tool wear rate (TWR). Therefore, the objective was to maximize the machining rate of difficult-to-machine materials through optimal selection of EDM parameters, followed by an evaluation of machinability. NiTi and NiCu alloys (20 mm diameter, 20 mm length) and BeCu (20×20×30 mm³) were used as workpiece materials. Electrolytic copper was selected as the tool electrode material due to its high electrical conductivity. A copper rod (6 mm in diameter, 2000 mm in length) was cut and processed on a milling machine to obtain rectangular-shaped blanks, from which test samples (4×4×25 mm) were made. A square cave measuring 3×3 mm and 5 mm deep was formed in the samples using a tool electrode. The use of oxygen-free electrolytic copper ensured high electrical conductivity and wear resistance of the tool during the machining process. The experiments were conducted on an Electronica Machine Tool Limited die-sinking EDM machine, model C400x250. Industrial EDM oil was used as the dielectric fluid. Side flushing at a pressure of 0.5 kg/cm² provided effective removal of erosion products and stability of the machining process. GR-300 digital scales (accuracy 0.0001 g) were used to measure MRR and TWR, and a Mitutoyo SJ 210 profilometer was used to measure surface roughness (SR). A more detailed description of the manufacturing process, experimental methods, and obtained results is presented in the previous work by Vijaykumar S Jatti et al., 2022 [36].
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