Ti-6Al-4V Surfaces in SiC Powder Mixed Electrical Discharge Machining

2013 ◽  
Vol 856 ◽  
pp. 226-230 ◽  
Author(s):  
Hamidullah Yaşar ◽  
Bülent Ekmekci
Keyword(s):  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Dielectric Liquid ◽  
Operational Parameters ◽  
Electrical Parameters ◽  
Machined Surface ◽  
Optical Scanning ◽  
Surface Topographies ◽  
Powder Suspension

The role of suspended particles on Ti-6Al-4V surface in Powder Mixed Electrical Discharge Machining (PMEDM) is studied using SiC powder mixing in water dielectric liquid. Surface modifications due to the additives in dielectric liquid are investigated by means of optical, scanning electron microscopy and energy dispersive spectroscopy. The attachment of added powders and surface topographies interrelated with powder suspension concentration, particle size and electrical parameters such as pulse on duration and current. The influence on discharge transitivity with respect to SiC additives is noticed with pock like features on the surface. The geometry and size of these features indicated a robust dependency with respect to operational parameters and indicated the role of secondary discharges during PMEDM. SiC particles severely transferred from di-electric liquid to machined surface at critical operational parameters and implied that the process could be also used as a surface alloying technique.

A Discharge Separation Model for Powder Mixed Electrical Discharge Machining

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Bülent Ekmekci ◽  
Hamidullah Yaşar ◽  
Nihal Ekmekci
Keyword(s):  
Electrical Discharge ◽  
Discharge Channel ◽  
Electrical Discharge Machining ◽  
Complete Separation ◽  
Dielectric Liquid ◽  
Material Transfer ◽  
Machined Surface ◽  
Machining Conditions ◽  
Main Discharge ◽  
Pulse On Time

Added powders in a dielectric medium substantially influence the features of electrical discharges due to altered interelectrode conditions during the electrical discharge machining (EDM) process. The main discharge channel is disturbed due to the added powders in dielectric liquid and leads formations of secondary discharges. Such altered discharge conditions generate a unique topography on the machined surface and consequent subsurface microstructure beneath it. Ti6Al4V work material machined using SiC powder mixing in de-ionized water for an extensive set of pulse-on duration and pulse currents. Then, different forms of secondary discharges were identified from the resultant surface features and corresponding subsurface microstructures. The results pointed out that generation of unevenly separated secondary discharges increased the material transfer rate from the powder mixed dielectric liquid to the machined surface by means of the decomposed ions in the plasma channel. Complete separation of the main discharge channel into evenly distributed secondary discharges is possible under specific machining conditions that suggested minimal deformation of the machined surface regarding microcracks, roughness, and heat affected layer thickness. Under such machining conditions, another means of material transfer mechanism is activated that lead a powder particle build-up process on the machined surface. Consequently, five different discharge forms were proposed to describe the resultant surface topographies and subsurface microstructures. The material migration phenomena and the mechanisms are discussed in relation to the pulse-on time and pulse current.

Hydroxyapatite Deposition onto Ti-6Al-4V Surface in Powder Mixed Electrical Discharge Machining

2013 ◽  
Vol 856 ◽  
pp. 205-209 ◽  
Author(s):  
Nihal Ekmekci ◽  
Bülent Ekmekci
Keyword(s):  
Electron Microscopy ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Bone Ingrowth ◽  
Material Surface ◽  
Operational Parameters ◽  
Optical Scanning ◽  
Prosthetic Implants ◽  
Ha Coating ◽  
Scanning Electron

Hydroxyapatite (HA) is bioactive and biocompatible bioceramics that is commonly used as a filler to replace amputated bone or as a coating to promote bone ingrowth into prosthetic implants. The need to overcome biocompatibility problems and improve the bone bonding ability enforced the researchers to develop suitable coating techniques. Feasibility of Powder Mixed Electrical Discharge Machining of Ti-6Al-4V alloy with HA additives in water dielectric liquid is studied as an alternative coating technique. Machined samples are analyzed by means of optical, scanning electron microscopy and energy dispersive spectroscopy. The experimental results have revealed that it is possible to deposit HA powders onto the work material surface by using the process. The morphology of the deposited material signified the dependency with respect to the operational parameters such as pulse on duration and current. Moderate pulse currents together with low pulse on duration were found to be the plausible choices for HA coating applications.

Modeling of Recast Layer in Micro-Electrical Discharge Machining

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
P. C. Tan ◽  
S. H. Yeo
Keyword(s):  
Numerical Model ◽  
Electrical Discharge ◽  
Prediction Models ◽  
Electrical Discharge Machining ◽  
Performance Measure ◽  
Recast Layer ◽  
Micro Edm ◽  
Machined Surface ◽  
Functional Layer ◽  
Pulse On Time

The thickness of recast layers produced during electrical discharge machining (EDM) is an important process performance measure as it may indicate an extent of crack propagation in a machined surface or thickness of a functional layer alloyed onto a machined surface. Thus, the availability of the recast layer thickness prediction models is needed to allow better control of machining outcomes, which becomes more vital for micro-EDM due to the microscale of machined features. The proposed numerical model, based on a multiple discharge approach for recast layer prediction, is developed to fill an existing gap in micro-EDM. The multiple discharge approach accounts for the overlapping nature by which craters are generated on the machined surface and considers the recast layer to be a combination of individual recast regions from individual craters. The numerical analysis, based on finite element methods, is used to determine the melting isotherms due to heat inputs on overlapping crater profiles. Then, a hemispherical-capped crater profile is estimated by applying a recast plasma flushing efficiency to the amount of molten material bounded by the melting isotherm. Finally, the recast region is defined to be bounded by the melting isotherm and crater profile. The model, developed for a peak discharge current of 1.45 A and pulse on time between 166 ns and 606 ns, predicted recast layer thicknesses of between 1.0 μm and 1.82 μm. It is then validated at pulse on time settings of 244 ns and 458 ns, which generated average recast layer thicknesses of 1.18 μm and 1.56 μm, respectively. Thus, the numerical model developed using the multiple discharge approach is suitable for estimation of recast layer thicknesses in micro-EDM.

A Study of the Mechanism of Electrical Discharge Machining of Particle Reinforced Metal Matrix Composites with Concavo-Convex Electrode

2011 ◽  
Vol 480-481 ◽  
pp. 300-305
Author(s):  
Jiang Wen Liu ◽  
T.M. Yue ◽  
Zhong Ning Guo ◽  
Z. Y. Wan ◽  
G.Y. Liu
Keyword(s):  
Metal Matrix ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Processing Condition ◽  
Matrix Composites ◽  
Wire Electrode ◽  
Machined Surface ◽  
Particulate Reinforced ◽  
Stable Processing ◽  
Processing Mechanism

A new concavo-convex electrode has been designed and employed. And an analysis of the electrical discharge machining (EDM) mechanism of a particulate reinforced metal matrix composite with this new electrode was conducted in this study. It was found that EDM with this new electrode can accelerate the debris discharge during machining so that it has a higher MRR compared to the case where a normal electrode was employed. Moreover, by studying the surface craters, it could confirm that discharge craters tend to connect together for the normal electrode. This indicates an abnormal arcing condition. Thus, the wire electrode was easy to be broken. While for the new electrode, separated craters were observed on the machined surface. This means a stable processing condition. The experiment results reveal the processing mechanism of EDM electrical discharge machining of MMCs by employing this new electrode.

Effects of Electrical Discharge Energy on Machining Performance of Sintered NdFeB Magnet

2009 ◽  
Vol 620-622 ◽  
pp. 711-714 ◽  
Author(s):  
Li Li ◽  
Guang Ming Yuan ◽  
Zong Wei Niu ◽  
Rong Guo Hou
Keyword(s):  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Removal Rate ◽  
Machining Parameters ◽  
Discharge Energy ◽  
Machining Performance ◽  
Ndfeb Magnet ◽  
Machined Surface ◽  
Micro Cracks ◽  
Ndfeb Permanent Magnet

Sintered NdFeB permanent magnet is widely used in many areas because of its excellent magnet property. In this study, the machining parameters of electrical discharge machining (EDM) are varied to study the effects of electrical discharge energy on material removal rate and surface roughness of NdFeB magnet. Moreover, the micro-cracks on the machined surface induced by EDM are also examined. The experimental results reveal that the MRR increases with the electrical discharge energy. The number of surface cracks on the machined surface increases with the enhancement of discharge energy Thus, using EDM process to machine sintered NdFeB magnet depends on setting the machining parameters to prevent surface crack.

High Speed Wire Electrical Discharge Machining (HS-WEDM) Phenomena of Insulating Si3N4 Ceramics with Assisting Electrode

2007 ◽  
Vol 339 ◽  
pp. 281-285 ◽  
Author(s):  
Yong Feng Guo ◽  
Ji Cheng Bai ◽  
Guan Qun Deng ◽  
Ze Sheng Lu
Keyword(s):  
Electrical Discharge ◽  
High Speed ◽  
Electrical Discharge Machining ◽  
High Hardness ◽  
Single Pulse ◽  
Wire Electrical Discharge Machining ◽  
Electrical Parameters ◽  
Abrasive Resistance ◽  
Electrode Method ◽  
Assisting Electrode

Advanced engineering ceramics are more and more widely employed in modern industries because of their excellent mechanical properties such as high hardness, high compressive strength, high chemical and abrasive resistance. This paper investigates the high speed wire electrical discharge machining (HS-WEDM) of Si3N4-based ceramics by assisting electrode method. The theory of assisting electrode method is introduced. The machining phenomena under different electrical parameters were studied and the optimized machine pulse width was got. The material removal mechanisms change with the increase in the power of single pulse.

Sign in / Sign up

Export Citation Format

Share Document