Articles written in Sadhana

    • Powder-mixed electro-discharge machining performance of Inconel 718: effect of concentration of multi-walled carbon nanotube added to the dielectric media


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      The present work reports an experimental investigation on Powder-Mixed Electro-Discharge Machining (PMEDM) of Inconel 718 superalloy using Multi-Walled Carbon Nanotubes (MWCNTs) dispersed in kerosene, as dielectric media. Effects of variation of peak discharge current along with concentration of carbon nanotubes in the dielectric fluid are studied in purview of machining performance indicators including material removal efficiency, tool wear rate, and surface integrity of the machined part. The obtained results are compared to that of conventional EDM which utilizes kerosene as dielectric media. Morphology and topography, these two aspects of machined surface integrity are deliberated. The following surface morphological features: uneven fusion structure, globules of debris, molten metal deposition, surface cracks, pockmarks, and recast layer are identified. Topographical study includes surface roughness, severity of surface cracking, recast layer thickness, transfer of foreign elements, surface metallurgical characteristics, residual stress, and microindentationhardness. It is observed that application of MWCNT mixed dielectric media substantially improves EDM performance of Inconel 718 over conventional EDM. This is due to excellent thermo-physical properties of carbon nanotubes.

    • Pulse laser welding of high carbon alloy steel: assessment of melt pool geometry and mechanical performance


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      An attempt has been made to join high carbon alloy steel sheet of 0.9 mm thickness by pulse Nd:YAG laser beam welding. Weld melt-pool geometry (i.e., melting depth and width) and the microstructure of the weld zone was analyzed through the optical microscopic images. The tensile strength of the weld joint was assessed through a universal testing machine. The variation of microhardness value in the melt pool zone of the weldment was assessed through Vickers micro indentation method. The effect of laser peak power and scan speed on the melt pool geometry, microstructure, tensile strength, and microhardness value of the weld joint was explored. The outcomes indicated that within the experimental domain for an optimum processing condition (laser peak power: 5 kW, beam diameter: 0.7 mm, pulse duration: 7 ms, and pulse frequency: 5 Hz), full penetrated welding was achieved, which exhibited almost 85% of the base material strength.

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