Experimental Research And Removal Crater Simulation Of Single Pulse Discharge For EDM Of ZrB₂-SiC Ceramic

In recent years, ceramic Zr B₂-Si C have been extensively applied in aerospace such as hypersonic aircraft and rocket propulsion because of its high melting point, hardness, and excellent performance resisting to thermal shock. The all Zr B₂-Si C components that are fabricated by sintering need subsequent precision processing for practical industrial application. However, Zr B₂-Si C is difficult to machine via traditional machining methods due to its high hardness and brittleness.Electrical discharged machining（EDM） has been becoming one of most popular untraditional methods to machine Zr B₂-Si C components with high shape and dimension precision. Compared with the traditional methods, this process has remarkable advantages on non-contact mechanical stress and has no limitation on mechanical properties of materials. To the best of the authors’ knowledge, a comprehensive experimental investigation for the EDM of Zr B₂-Si C has not been reported in the literature. Hence, the primary objecti ve of this work is to conduct fundamental experimental investigation and numerical simulation of the EDM of Zr B₂-Si C. The specific details are as follows:The randomly distributed model of Si C particles is established via APDL language of ANSYS to simulate the crater of single pulse discharge. Simultaneously, the relationship among energy parameters including peak current and pulse duration, discharged crater profile and volume is investigated, based on this model. Finally, the confirmation experiment of single pulse discharge is performed to verify its validity.The process parameters including polarity of electrode, peak current, pulse duration, pulse interval, reference voltage and servo speed are selected to carry out single factor experiments. And the three responses consisting of material removal rate, lateral gap, and surface roughness are selected to determine how the process parameters have effect on the performance on EDM of Zr B₂-Si C. Moreover, the machined surface composition and surface integrity are detected using energy dispersive spectroscopy and scanning electron microscopy, respectively. The findings show that rupture zone and smooth zone are formed on the machined surface. The former is due to thermophysical properties mismatch between Zr B₂ and Si C in the process of resolidification. And the latter is generated by larger energy discharge. Furthermore, Zr O2 is generated in debris. The tiny crater with few microns is formed on the machined after removal of Si C. And the number of it increases with enlargement of discharge energy. The thickness of resolidification layer increases with increasing peak current and pulse duration, respectively.The process parameter optimization is investigated by combining the Taguchi method with signal-noise ratio analysis, based on the above determined process parameters and responses. The results show that material removal rate increases by 12.33%, lateral gap and surface toughness decrease by 12.38% and 4.75%,respectively. Finally, the multi-response optimization is performed using the grey relational analysis. The findings indicate that the material removal rate increases by 12.9%. The lateral gap and surface toughness decrease by 4.27% and 4.87%, respectively. The significant factors that influence the multiple performance characteristics for EDM of Zr B₂-Si C are pulse duration, peak current, and reference voltage in sequence.