Pulse-Type Influence on the Micro-EDM Milling Machinability of Si₃N₄-TiN Workpieces

Area of Science:

• Materials Science
• Manufacturing Engineering
• Surface Engineering

Background:

• Micro-electro discharge machining (micro-EDM) is crucial for fabricating intricate components from advanced ceramics.
• Silicon nitride-titanium nitride (Si3N4-TiN) composites present unique machinability challenges due to their properties.
• Understanding the influence of discharge pulse characteristics is key to optimizing micro-EDM processes for these materials.

Purpose of the Study:

• To investigate the micro-EDM milling machinability of Si3N4-TiN workpieces.
• To analyze the impact of different discharge pulse types on material removal rate (MRR) and tool wear rate (TWR).
• To characterize the surface integrity of micro-EDM machined Si3N4-TiN.

Main Methods:

• Micro-EDM milling experiments were conducted on Si3N4-TiN using a Design of Experiments (DOE) approach.
• Voltage and current pulse waveforms were recorded during machining.
• A pulse discrimination algorithm classified pulse types (short, arc, delayed, normal) for post-processing.
• Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were used for surface analysis.

Main Results:

• Material removal rate (MRR) was significantly influenced only by normal discharge pulses.
• Tool wear rate (TWR) was affected by normal pulses, while arc and delayed pulses unexpectedly reduced tool wear.
• Surface analysis revealed re-solidified droplets and micro-cracks, altering the surface's chemical composition and quality.

Conclusions:

• The micro-EDM process for Si3N4-TiN exhibits distinct behaviors compared to metallic materials.
• Optimizing pulse types, particularly utilizing arcs and delayed pulses, could enhance tool life in Si3N4-TiN micro-EDM.
• Surface modifications, including micro-cracks and re-solidified material, necessitate further investigation for specific applications.