Mohammed Baba Ndaliman

Influence of electrical discharge machining process parameters on surface micro-hardness of titanium alloy:

The resistance of a material to an indentation on microscopic scale is an indication of its micro-hardness. To a lubrication engineer, micro-hardness is synonymous with surface wear resistance of a material. In this study, an attempt was made to enhance the surface micro-hardness of titanium alloy (Ti-6Al-4V) through modification of electrical discharge machining process parameters. These parameters are the electrode, the dielectric fluid and the electrical variables of the machine. Cu–TaC composite electrode produced through powder metallurgy method was used during the electrical discharge machining with different urea concentrations in distilled water as dielectric fluid. The electrical variables used were the peak current, the pulse duration and the duty factor. Electrical discharge machining was also conducted with copper (Cu) powder metallurgy electrode with distilled water dielectric fluid for comparison. The results showed that the micro-hardness of the electrical discharge machined surfaces with Cu–TaC electrode/urea dielectric fluid was generally higher than that of those with Cu electrode/distilled water dielectric fluid. The highest micro-hardness of 1795 Hv was attained with 10 g/L of urea concentration.

Influence of dielectric fluids on surface properties of electrical discharge machined titanium alloy

Dielectric fluid is one of the major components of electrical discharge machining. In this article, the influence of two dielectric fluids on the surface properties of workpiece was investigated. Machining was conducted on the titanium alloy (Ti-6Al-4V) with the new Cu-TaC composite electrodes under the two dielectric fluids, which are the urea solution and distilled water. Cu-TaC electrodes were produced from copper and tantalum carbide powders by powder metallurgy method with 50/50% composition at compacting pressure of 24.115 MPa. The main objective is to compare the effect of these dielectric fluids on the electrical discharge machined surface properties—microhardness (Mh) and surface roughness (Ra). The machining variables used to investigate the Ra and Mh were peak current and pulse duration. The surface roughness was found to be generally higher in the specimens machined with urea solution dielectric fluid, the highest being 19.05 µm. For the specimens machined with distilled water dielectric fluid, the highest Ra is 14.45 µm. The highest microhardness improvement ratio attained by the specimens electrical discharge machined with urea dielectric fluid is about 48% higher than those machined with distilled water. It is concluded that distilled water dielectric fluid gave better surface roughness, while the urea dielectric fluid provides the machined surface with higher microhardness.

Improving micro-hardness of stainless steel through powder-mixed electrical discharge machining

Powder-mixed electrical discharge machining (PMEDM) is the technique of using dielectric fluid mixed with various types of powders to improve the machined surface output. This process is fast gaining prominence in electrical discharge machining (EDM) industry. The objective of this investigation is to determine the ability of tantalum carbide (TaC) powder-mixed dielectric fluid to enhance the surface properties of stainless steel material during EDM. The properties investigated are the micro-hardness and corrosion characteristics of the EDMed surface. Machining was conducted with 25.0 g/L concentration of TaC powder in kerosene dielectric fluid. The machining variables used were the peak current, pulse on time and the pulse off time. The effects of these variables on the micro-hardness of the EDMed surface were determined. Corrosion tests were also conducted on the samples that exhibited higher hardness. Results showed that the EDMed surface was alloyed with elements from the TaC powder. The highest micro-hardness obtained with PMEDM is about 1,200 Hv. This is about 1.5 times that obtained without TaC powder in the dielectric fluid. The loss in weight during corrosion test was found to be 0.056 µg/min for the PMEDM which was much lower than the lowest value of 10.56 µg/min obtained for the EDM without powder dielectric fluid.

Surface modification using Electric Discharge Machining (EDM) with powder addition

Powder mixed electrical discharge machining (PMEDM) is one of the recent innovations for the enhancement of the capabilities of EDM process. In this study, the effects of powder addition on the surface modification of mild steel were investigated. Copper tungsten electrode was used in the machining. Two different powders namely TiC and Al2O3 were used in the study with kerosene as the dielectric medium. The powder types and currents were manipulated to study their effects on the machined surface. The results show that increasing the current leads to increase in recast layer thickness, and the cracks. The Al2O3 powder gave higher layer thickness than TiC powder. TiC Powder addition also produced higher hardness, more tool material and carbon depositions on the work surface than Al2O3 powder.

Formation of Nitrides and Carbides on Titanium Alloy Surface through EDM

In this investigation, electrical discharge machining (EDM) was done with Cu-TaC powder metallurgy (PM) electrode and urea solution dielectric fluid. The main objective is to improve the surface wear property of Ti-6Al-4V alloy through the formation of hard ceramic compounds on its surface during EDM. The experiments were conducted with peak current, Ip (3.5, 5.5 A) and pulse duration, ton (3.3, 5.3 µsec) as the machining variables. The outputs investigated are surface characteristics and micro-hardness. The formation of nitrides, carbides and oxides of tantalum and titanium on the EDMed surface was confirmed. The highest micro-hardness of 902.2 Hv was obtained with Ip of 5.5 A and ton of 3.3 µsec.

Electro-Discharge Machining of SUS 304 Stainless Steel with TaC Powder-Mixed Dielectric

Powder-mixed dielectric fluid is one of the innovations of electro-discharge machining (EDM) which seeks to improve the process outputs by addition of powders to the dielectric during machining. In the present study, the influence of TaC powder in kerosene dielectric fluid on EDM process outputs was investigated. Experiments were conducted with the outputs as material removal rate (MRR), surface roughness (Ra) and micro-hardness. During the EDM, the discharge current was varied between 2.5 and 6.5 A, while powder concentration ranges between 5.0 and 15.0 g/l. Results indicate that the highest MRR of 0.38 g/min was obtained with TaC concentration of 15 g/l at the current of 6.5 A. TaC powder addition does not affect both the MRR and Ra at lower current. However, the level of micro-hardness attained was influenced by TaC powder concentration in dielectric fluid, the highest being 1,040 Hv with 5.0 g/l at the current of 2.5 A.

Surface Quality Produced in EDM with Tungsten Carbide and Copper Compacted Electrodes

Electrical discharge machining (EDM) is one of the most commonly used technique to machine very hard materials. Materials like hardened tool steels, titanium and its alloys and difficult-to-machine materials can be easily processed with EDM. The machining performance to a great extent depends on the composition of the electrode. This paper presents the machining performance of powder metallurgy (PM) compacted electrodes made from titanium carbide (TiC) and copper (Cu) powders. The Cu-TiC electrodes made up of 70% of TiC and 30% of Cu powders. They were compacted at a pressure of 6,000 psi (41.34 MPa). Mild steel was used as the workpiece material. Machining was conducted with the peak current, pulse-on time and pulse-off time as the electrical input variables. The output variables of the investigation were work surface roughness and its hardness. It was found that work surface roughness increases with increase in current and pulse-on-time. However, it decreases with increase in pulse-off time. It was found that the highest value of surface roughness (14.782 μm) was found at highest peak current (6.5 A), highest pulse on-time (7.5 μs) and lowest pulse-off time (6.5 μs). The highest value of surface hardness (57.3 BHB) was found at the same machining conditions. The smoothest surface (14.782 μm) was found at the lowest peak current (3.5 A), lowest pulse on-time (6.0 μs) and highest pulse-off time (8.5 μs). The lowest value of surface hardness (42.9 BHB) was found at the same machining conditions.

Electro-Discharge Machining of Ti-6Al-4V alloy using Cu-TaC compact electrode with urea dielectric: Reactions and their effects on the machined surface

This paper presents the investigation of compounds / phases formed during the Electrical Discharge Machining (EDM) of titanium alloy (Ti-6Al-4V) with Cu-TaC compact electrode using urea dielectric fluid. It is proposed that the materials involved in the machining are likely to react and form new compounds on the EDMed surface. The outcomes of the reactions were predicted. The EDMed surfaces were subjected to energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis to determine the changes in the surface composition. Results of EDX analysis indicate the presence of additional elements (Cu, Ta, O and C) on the surface of the parent alloy. XRD results also confirm the main compounds formed on the surface to include metallic oxides, carbides and nitrides (TaC, TiC, Ti2N, TiO) of tantalum and titanium. It is concluded that the surface was reinforced during the EDM with hardened ceramic layers which are capable of enhancing its wear properties.

Surface Roughness Characteristics in Finish Electro-Discharge Machining Process

Surface characteristics, which include surface roughness, surface hardness, and corrosion resistance of surface of machining products, have received attention in recent years. Research on how to improve the surface characteristics by electro-discharge machining with chromium powder mixed fluid and improvement on surface integrity in both conventional and cryogenic Electrical discharge machining (EDM) is gaining more ground. The trend in determining surface finishing by hand polishing, which is performed after the EDM, has given way to the controlling of the discharge pulse energy or using powder mixed working fluid to obtain a better surface roughness. Hence, this chapter highlights recent research in improving surface characteristics in the finish EDM process.

Simulating the Electrical and Thermal Conductivity in EDM Die Sinking of Cu-TaC Compact Electrodes Using Neural Network

Electrical and thermal conductivity of electrode materials in Electrical Discharge Machining (EDM) is the main factors that determine the suitability of these electrodes. These electrodes are usually made from graphite, copper and copper alloys because these materials have high electrical and thermal conductivity in additional to high melting temperature. The objective of this paper is to simulate the electrical conductivity and thermal conductivity for new compact electrodes made from Cupper-Tantalum Carbide (Cu-TaC). This simulation based on experimental work. Materials have been used in the experiment were Cupper and Tantalum Carbide powders. The compositions of the Cu-TaC are made of 30 % and 55 % wt of TaC, while the compacting pressures are 1, 500 psi and 3,000 psi. The thermal and electrical conductivities have been measured. The Neural Network (NN) technique has been used to simulate the electrical conductivity and thermal conductivity of the green compacted electrodes. They were subjected to sintering at temperatures of 450°C and 850°C.