No abstract

No abstract

Background Electrical Discharge Machining (EDM) is a well-established non-conventional machining process for the machining of electrically conductive and difficult-to-machine materials. But its applications are limited because of the slow machining rate and poor surface finish. Powder mixed EDM (PMEDM) is unitary of the recent progresses in the EDM process in which powder particles mixed in the dielectric fluid results in higher machining rate and better surface quality. In the past, limited work has been found on PMEDM of Inconel-800 material.  Researchers have reported about machining with different powder particles like aluminum powder, silicon carbide, graphite etc. in the dielectric fluid of EDM, but the effect of powder particles, i.e. Tungsten carbide, cobalt and boron carbide along with tool material i.e. copper, copper-chromium and graphite on Inconel-800 material has not been explored. The purpose of the present work is to look into the issue of tool material (Cu, copper-chromium, and graphite) along with powder particles (tungsten carbide, cobalt and boron carbide) suspended in EDM oil on Inconel-800 material. Methods The present work includes optimization of Material Removal Rate (MRR) and Tool Wear Rate (TWR) for the machining of Inconel-800 material using Powder Mixed Elctric Discharge Machining (PMEDM). Different input parameters such as peak current, pulse on-time, pulse off-time, tool and powder materials along with effect of three micro powder particles, i.e. tungsten carbide, cobalt and boron carbide and three electrodes i.e. copper, copper-chromium, and graphite have been considered for the experimentation. The box-Behnken method of Response Surface Methodology (RSM) has been used for designing the experiments along with the Desirability Approach for multiple response parameters optimization. The adequacy of the proposed mathematical models have also been tested using analysis of variance (ANOVA). Microstructure analysis and transfer of different factors on the machined surface has also been investigated using Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS) and X - Ray Diffraction (XRD). Results The results showed that peak current, pulse on-time, and tool material significantly affects the Material Removal Rate (MRR) while peak current, pulse on-time, tool material and powder materials affected the Tool Wear Rate (TWR). Pulse off-time has a trifling effect on both MRR and TWR, while powder particles on MRR. From desirability approach, the optimal combination of parameters found to be current 1 amp, pulse on-time 0.98 μs, pulse off-time 0.03 μs, tool material 0.31 and the powder (suspended particles) 0.64. Conclusion The analysis of the experimental observations highlights that the current, pulse on-time and tool material have found to be the most decisive factors for MRR, while current, pulse on-time, tool material and powder particles for TWR.

Three grades of titanium alloy Ti (grade 2), Ti-6Al-4V (grade 5) and Ti-5Al-2.5Sn (grade 6) were machined using electric discharge machining after deep and shallow cryogenic treatment. The peak current was observed to be the most significant factor followed by electrode material and pulse-on time. Subsequently, a mathematical model for predicting material removal rate of titanium alloys was developed using dimensional analysis based on the significant process parameters affecting material removal rate and the thermal–physical properties of the titanium alloy. The predicted results obtained from the mathematical model were validated by comparing with the experimental results and were found to be in good agreement with each other. Incremental increase in material removal rate was observed after deep cryogenic treatment due to increase in thermal and electrical conductivity of the material. The model showed that the thermal properties of the material such as thermal conductivity, specific heat and boiling point of materials affect the erosion process in electric discharge machining. Microstructure analysis was carried out using scanning electron microscope, energy-dispersive X-ray spectrometer and X-ray diffraction for selected samples. The migration of different elements and formation of compounds on the machined surface was investigated using energy-dispersive X-ray spectrometer and X-ray diffraction analysis.

Three grades of titanium alloy TITAN 15, TITAN 21, and TITAN 31 were machined using powder mixed electric discharge machining to study the effect of cryogenic treatment and its effect on tool wear rate (TWR). Thereafter, an attempt has been made to develop a mathematical model for predicting TWR using dimensional analysis using the outcome of the Taguchi model and thermo-physical properties of tool materials. The model shows the significant role of thermal conductivity on TWR in electric discharge machining of titanium alloys. The predicted values from the developed mathematical model were validated and were found to be in good agreement with the experimental results. Microscopic investigations on selected tool samples were performed using scanning electron microscope, energy-dispersive X-ray spectrometer, and X-ray diffraction. The results showed transfer of material on the tool surface from the workpiece, dielectric, and the powder.

No abstract

No abstract

No abstract