Surface Quality of Al2O3 Ceramic and Tool Wear in Diamond Wire Sawing Combined with Oil Film-Assisted Electrochemical Discharge Machining

At a Glance

Metadata	Details
Publication Date	2023-08-07
Journal	Applied Sciences
Authors	Zhixin Jia, Kaiyue Zhang, Jin Wang
Institutions	University of Science and Technology Beijing
Citations	5
Analysis	Full AI Review Included

Executive Summary

Core Innovation: The research successfully integrated Oil Film-Assisted Electrochemical Discharge Machining (OF-ECDM) with Diamond Wire Sawing (DWS) to enhance the processing of hard, brittle, insulating Al₂O₃ ceramic.
Efficiency Improvement: The combined OF-ECDM/DWS process achieved a 36% increase in Material Removal Rate (MRR), raising the rate from 1.29 mm³/min (DWS only) to 1.75 mm³/min.
Mechanism Stability: The oil film provides stable electrical insulation, enabling consistent spark discharge necessary for ECDM, solving the instability issues associated with hydrogen gas film formation in traditional ECDM for thicker workpieces.
Material Removal Mode: Spark discharge thermally weakens the Al₂O₃ ceramic, facilitating material removal primarily through mechanical failure (spalling) by the diamond wire, rather than melting.
Surface Integrity: Machined surfaces showed excellent integrity, with no evidence of a thermal recast layer or micro-cracks, even at high voltages (58 V).
Roughness Control: Surface roughness (Ra) increased with applied DC voltage. The minimum roughness was achieved at 46 V (0.485 µm parallel, 0.732 µm perpendicular).
Tool Wear Factor: Spark discharges created micro-craters on the nickel (Ni) binder matrix of the diamond wire, increasing the probability of diamond grit pull-out, indicating a trade-off between MRR and tool life.

Technical Specifications

Parameter	Value	Unit	Context
Al₂O₃ Density	3.9	g/cm³	Workpiece material property
Al₂O₃ Electrical Resistivity	10¹⁶	Ω cm	Workpiece material property
Al₂O₃ Thermal Conductivity	35	W/m K	Workpiece material property
MRR (DWS only)	1.29	mm³/min	Baseline performance
MRR (OF-ECDM assisted)	1.75	mm³/min	Maximum achieved rate
MRR Improvement	36	%	Relative increase in removal rate
Diamond Wire Diameter	0.2 ± 0.01	mm	Tool specification
Workpiece Thickness	10.0	mm	Cutting depth
DC Voltage Range Tested	46 to 58	V	Spark discharge parameter
Wire Speed	1400	mm/s	Machining parameter
Electrolyte Concentration	20	%	NaCl solution mass fraction
Minimum Ra (Parallel, 46 V)	0.485	µm	Optimal surface finish parallel to wire
Maximum Ra (Parallel, 58 V)	0.890	µm	Highest roughness tested parallel to wire
Guide Rail Oil Kinematic Viscosity	69.24	mm²/s (40 °C)	Oil film property
Guide Rail Oil Flash Point	233	°C	Oil film property

Key Methodologies

Equipment Modification: A DK7720 fast wire EDM machine was converted by replacing the molybdenum wire with a diamond wire saw and integrating a discharge circuit and electrolyte supply system.
Oil Film Formation: Guide rail oil was applied to the electrode wire surface using an online oil coating device prior to the wire entering the electrolyte, ensuring a complete insulating oil film.
Electrolyte Setup: A 20% mass fraction NaCl solution was selected as the electrolyte due to its non-corrosive nature and good electrical conductivity.
Discharge Mechanism: Spark discharge was generated by applying a DC voltage (46 V to 58 V) between the electrode wire (cathode) and a stainless steel auxiliary electrode (anode).
Feed Control: The Al₂O₃ workpiece was mounted on a slider and pulled by a 400 g counterweight, ensuring that the feed rate was a result of the material removal rate, not a fixed process parameter.
Surface Roughness Measurement: Roughness (Ra) was measured using a TR100 tester in two orientations: parallel and perpendicular to the diamond wire cutting direction.
Microscopic Analysis: Scanning Electron Microscopy (SEM) was used to observe surface topography, material removal mechanisms (ductile regime vs. brittle spalling), and tool wear (micro-craters on the Ni matrix).
Elemental Analysis (EDS): Energy Dispersive X-ray Spectroscopy was used to confirm the absence of carbon accumulation (kerosene pyrolysis) and nickel transfer (tool material) on the machined surface, while detecting residual Na and Cl from the electrolyte.

Commercial Applications

High-Efficiency Ceramic Slicing: Applicable in industries requiring rapid, precise cutting of thick, hard, and electrically insulating materials (e.g., Al₂O₃, SiC, glass).
Semiconductor Substrate Manufacturing: Used for dicing or slicing high-purity alumina substrates for microelectronics and power devices where minimizing subsurface damage (micro-cracks) is critical.
Structural Ceramics Fabrication: Processing complex or large structural ceramic components for aerospace and automotive applications where traditional mechanical sawing is too slow or causes excessive chipping.
Energy Conservation Machining: The OF-ECDM method significantly reduces the energy required for maintaining the electrochemical reaction necessary to generate the hydrogen gas film in traditional ECDM, offering a more energy-efficient processing route.
Precision Tooling and Insulators: Manufacturing high-tolerance ceramic parts used as electrical insulators, wear components, and specialized tooling where the absence of a recast layer is mandatory for performance.

View Original Abstract

Diamond wire sawing is one of the most widely used methods of cutting Al2O3 ceramic because it has good machining accuracy and causes less surface damage. However, its material removal rate (MRR) needs to be improved with the increasing demand for Al2O3 ceramic parts. In this paper, spark discharges are generated around the diamond wire based on the electrochemical discharge machining (ECDM) process. An oil film-assisted ECDM process is applied to solve the difficulty of generating spark discharges when the thickness of the workpiece exceeds 5.0 mm due to the difficulty of forming a hydrogen gas film. Experimental results show that the combination of oil film-assisted ECDM and diamond wire sawing improved the MRR of Al2O3 ceramic. Oil film-assisted ECDM may improve the surface quality of machined parts and reduce the wear on diamond wire. Therefore, this research focuses on the surface quality of Al2O3 ceramic and tool wear in diamond wire sawing combined with oil film-assisted ECDM. Surface roughness and topography, recast layer, and elements of the machined surface are analyzed. The tool wear is studied using SEM images of diamond wire. The results provide a valuable basis for application of diamond wire sawing combined with oil film-assisted ECDM.

Tech Support

Original Source

DOI: https://doi.org/10.3390/app13159030

References

2011 - Effect of process parameters on surface quality for wire saw cutting of alumina ceramic
2019 - Effect of MgO/MgF2 doping on sintering, microstructure and microwave dielectric properties of Al2O3 ceramics
2001 - Development Status of EDM Technology in Japan
2012 - Research on Mixed Powder Electrochemical Discharge Composite Machining Technology
2009 - Surface integrity and material removal mechanisms associated with the EDM of Al2O3, ceramic composite [Crossref]
1999 - Experimental investigations into electrochemical discharge machining (ECDM) of non-conductive ceramic materials [Crossref]
2004 - Study of electrochemical discharge machining technology for slicing non-conductive brittle materials [Crossref]
2016 - Improvement in Machining Rate with Mixed Electrolyte in ECDM Process [Crossref]
2020 - Research on Parameter Optimization of insulator ceramic Tracking electrolytic EDM