Amitava Mandal

Modeling and Optimization of Machining Nimonic C-263 Superalloy using Multicut Strategy in WEDM

In recent years, wire-electrical discharge machining (WEDM) has gained popularity in the industry due to its capability to generate complicated shapes in exotic materials, irrespective of their hardness. Conventional machining of Nimonic C-263 superalloy is an extremely difficult and costly process due to its high hardness and tool wear rate. The present research work investigates the influence of the WEDM process parameters on different performance measures during machining of Nimonic C-263 superalloy. A mathematical model for all four important performance measures, namely, cutting rate, surface roughness, spark gap, and wire wear ratio, was developed and the responses were used for studying the interrelationship between performance measures and process parameters. The optimal settings of operating conditions were predicted using desirability function. The effectiveness of multicut strategy was also investigated in the article.

Fiber laser cutting of CFRP composites and process optimization through response surface methodology

ABSTRACT In this experimental study, the effects of major laser process control parameters, such as the laser power, beam scanning speed and assisting gas flow rate, on cut surface integrity defined by the kerf width, taper percentage, and the extent of heat affected zone (HAZ) were investigated. Response surface methodology (RSM) along with central composite design (CCD) of the experiment was used to optimize the process parameters to get better-cut surface quality. The optimum values of process parameters corresponding to cut surface with minimum defects are laser power 260 W, cutting speed 4500 mm per min, and assistance gas flow rate 14.23 l/min and the corresponding kerf width, taper percentage, and the width of HAZ are found to be 163.7 µm, 5.75%, and 573.28 µm. The confirmation experiments have been conducted that provide favorable results with an error of 2.70%, 1.87%, and 0.36%, for kerf width, taper percentage, and width of HAZ, respectively.

Pulse current co-deposition of Ni-WS2 nano-composite film for solid lubrication

ABSTRACT This study was undertaken to observe the effect of nano-composite coating on steel surface for enhancing its tribological properties. In the investigation, EN31 steel surfaces were coated with nano-composite (Ni-WS2) by pulse current co-deposition process in order to improve the tribological properties of the surface. The coatings were prepared according to different parameter settings. The effect of variations on coating thickness, microstructure, surface morphology, microhardness and tribological properties was observed. The maximum coating thickness of 117 µm with 8% by weight of WS2 particle concentration could be attained with the following parameter settings: applied voltage: 5 V; pulse frequency: 20 Hz; WS2 concentration: 20 g/l; duty factor: 0.6 and bath temperature: 50°C. The average friction coefficient of the deposited surface was 0.11, which is significantly less than that of the EN31 steel surface (average coefficient of friction > 0.5).

Influence of Abrasive Water Jet Turning Parameters on Variation of Diameter of Hybrid Metal Matrix Composite

Abrasive water jet turning is one of the recently developed manufacturing technologies. It has gained its importance due to its capability to machine difficult-to-cut material with advantages such as absence of thermal effects, high machining flexibility and little cutting force. In this study, the influence of water jet turning parameters such as abrasive type and abrasive mass flow rate has been analysed on the variation of diameter with the target diameter of metal matrix composite. Composite material A359/Al2O3/B4C fabricated by electromagnetic stir casting process was used in the experiment. To select the level of parameter, one-variable-at-a-time analysis was used. The results revealed that the abrasive type had a greater influence on the deviation of diameter from the target diameter as compared to mass flow rate.

Surface alloying of miniature components by micro-electrical discharge process

ABSTRACT Surface alloying is necessary to enhance the surface features of machine elements. In the present study, feasibility of micro-electric discharge machining (micro-EDM) process for surface alloying has been investigated. Experiments are conducted on Nickel sheets using tool of Ti6Al4V with EDM oil and kerosene as dielectric. The surface modification takes place by spark discharges on localized regions of the work piece and the tool surface causing melting of tool and work piece, disassociation of dielectric, alloying, and quenching in the electrolyte. The samples were analyzed by field emission scanning electron microscope equipped with energy-dispersive X-ray spectroscopy, microhardness testing machine, and X-ray diffraction. Recast layers obtained have distinct structure and composition as compared to the work piece. Average recast layer thickness varied from 10.72 to 69.8 µm in case of EDM oil and from 13.5 to 31.6 µm in case of kerosene by varying voltage, pulse duration (on time) and frequency during the experiment. The microhardness of the machined surfaces was obtained in a wide range of 161.61–338.25 HV whereas the microhardness of unaffected base metal was 132.25 HV. Titanium carbide (TiC) was deposited and consequently there was improvement in the hardness of the work piece.

Performance evaluation of Al2O3 nano powder mixed dielectric for electric discharge machining of Inconel 825

ABSTRACT Electrical discharge machining (EDM) process is popular for machining conductive and difficult-to-cut materials, but low material removal rate (MRR) and poor surface quality are major limitations of the process. These limitations can be overcome by adding the suitable powder in the dielectric. The powder particles influence electric field intensity during the EDM process which in turn improve its performance. The size (micro to nano) and properties of the mixed powder also influence the machining efficiency. In this regard, the objective of the present work is to study the performance of EDM process for machining Inconel 825 alloy by mixing Al2O3 nanopowder in deionized water. The experimental investigation revealed that maximum MRR of 47 mg/min and minimum SR of 1.487 µm, which are 44 and 51% higher in comparison to conventional EDM process, respectively, can be achieved by setting optimal combinations of process parameters. To analyze these observed process behavior, pulse-train data of the spark gap were acquired. The discharge waveform identifies the less arcing phenomenon in the modified EDM process compared to conventional EDM. Further, surface-topography of the machined surface was critically examined by capturing field emission scanning electron microscopy and atomic force microscopy images.

State of art in wire electrical discharge machining process and performance

Wire electrical discharge machining (WEDM) is one of the most widely used electro-thermal-based non-traditional machining process, which can be applied for almost the whole range of electrically conductive materials irrespective of their hardness. The rapid, repetitive and discrete spark discharge between the wire tool and job immersed in a dielectric medium leads to build up rapid heat and remove the unwanted material from the parent material by means of melting, spalling and chemical reaction. In recent years, researchers have explored a number of ways to improve the WEDM process performance by analysing the different factors that affect the quality characteristics. The experimental and theoretical studies show that process performance can be improved considerably by proper selection of tooling, material and operating parameters. This paper reviews the research work carried out so far in the area of machining different materials by WEDM. The review presents a report about the influence of WEDM process parameters and studies the improvement of the process performance.