RESUMO
The present study reports on the method used to obtain the reliable outcomes for different responses in electric discharge machining (EDM) of metal matrix composites (MMCs). The analytic hierarchy process (AHP), a multiple criteria decision-making technique, was used to achieve the target outcomes. The process parameters were varied to evaluate their effect on the material erosion rate (MER), surface roughness (SR), and residual stresses (σ) following Taguchi's experimental design. The process parameters, such as the electrode material (Cu, Gr, Cu-Gr), current, pulse duration, and dielectric medium, were selected for the analysis. The residual stresses induced due to the spark pulse temperature gradient between the electrode were of primary concern during machining. The optimum process parameters that affected the responses were selected using AHP to figure out the most suitable conditions for the machining of MMCs.
RESUMO
In the present work, a hybrid magnetic field assisted powder mixed electrical discharge machining had been carried out on the Aluminum-Silicon Carbide (Al-SiC) metal matrix composite. The aim of the study was to obtain higher surface finish, and enhanced material removal rate. The dielectric mediums employed were plain EDM oil, SiCp mixed and graphite powder mixed EDM oil for flushing through the tube electrode. The magnetic field intensity, discharge current, T-on/off duration and type of dielectric were the control variables used for present investigation. From the results, it was observed that the machining variables for instance, discharge current, T-on/off duration and type of dielectric conditions remarkably affected the material removal rate, micro-hardness and surface roughness of the machined composite material. The MRR augmented considerably with an increase in the magnetic field intensity along with peak current. Subsequently, the composite with lesser vol.% of SiC particulates witnessed sharp rise in MRR in maximum magnetic field environment (0.66T). In addition, quality of the machined surface improved significantly in graphite powder mixed dielectric flushing condition with intermediate external magnetic field environment. Besides, an enhancement of micro-hardness was quantified as compared to base material due to the transfer of the material (SiCp) during powder mixed ED machining.
RESUMO
Nano-hydroxyapatite powder was used in electric discharge machining to modify the surface of Ti-6Al-4V medical alloy. Herein, electric discharge machining was performed, with and without powder-mixed flushing for evaluation of the material erosion rate and surface roughness. In addition to dielectric type, several process parameters including current, pulse-on duration, pulse-off duration, and electrode hole diameter were considered. The experiments were planned by Taguchi design technique and conducted to analyze the material erosion rate and surface roughness. After machining, scanning electron microscope, energy-dispersive X-ray spectrometry, and X-ray diffraction techniques were used to evaluate the surfaces of the samples. Furthermore, wear and corrosion tests were also carried out on the Ti alloy with modified surfaces. The influential factors were identified based on analysis of variance results. Current and dielectric type were the significant factors, both for the material erosion rate and surface roughness. The scanning electron microscope images of Ti-6Al-4V samples highlighted that the process parameters exhibited a vital influence on the topology and microstructure of machined surface. Furthermore, energy-dispersive X-ray spectrometry and X-ray diffraction analyses confirmed the presence of hydroxyapatite on Ti alloy surface after machining. Moreover, the results of wear and corrosion tests revealed lower wear and corrosion rates of the surface-treated workpiece with nano-hydroxyapatite.