Study of nonconductive Si3N4 ceramic machining ability by electrical discharge machining process by assisting electrode

Based on the review of the previous researches, more than 50% of the cost of ceramic parts is related to machining costs, about silicon nitride (Si3N4), which is one of the most important engineering ceramics, while up to 80% has been reported. This ceramic has a combination of desirable properties such as wear and corrosion resistance and high hardness. Due to the high tool wear in machining process, the use of traditional methods is not appropriate. The electrical discharging machining process is a method that can machined all conductive materials without regard to mechanical and metallurgical properties, but machining of non-conducting ceramics such as silicon nitride is not normally possible by electrical discharging machining process. Therefore, in this research, the assisted electrode method has been used to perform the electrical discharge machining of silicon nitride ceramics. After preparing ceramic samples, copper-carbon bilayer and single copper layer were coating on the Si3N4 and they were successfully machined. In order to further examine the machined surface, imaging was performed by SEM. The results show that an increase in material removal rate in two-layer coating compared to single-layer coating. Also, after finishing machining process, EDX analysis was performed from the surface of ceramic workpiece, which indicates the presence of carbon and copper elements in the machined surface. In addition, the copper tool wear ratio in two-layer coating is less than that of single-layer coating.