Experimental Investigation of the Surface Integrity of Deep Cryogenically Treated WEDM Machined Surface

Abstract

WEDM is the most important machining method with which complex and complicated geometries can be easily machined. Based on exhaustive literature survey, it has been found that limited work has to be done on machining of deep cryogenic treated die steel AISI D3. The die steel AISI D3 plate of 150mm×150mm×10mm and deep cryogenic treated die steel plate of size 80mm×50mm×10mm is used for experimental purpose. The input process parameters pulse on time, pulse off time, spark gap set voltage and wire feed rate are investigated to check their effects on performance characteristics like material removal rate, surface roughness and percentage of dimensional deviation. The ranges of process parameters are selected based on the pilot study. In pilot study different input parameters are varied to check their effect on cutting rate. The experiments were designed using L18 orthogonal array with variation in process parameters. In this study MINITAB 16.0 software is used for designed the number of alternative experiments. The analysis of variance has to be done for study the significant factors that will greatly affect the performance characteristics. The main aim of study is to check the affect of deep cryogenic treatment on performance characteristics at same parameters conditions. Experimental results showed that material removal rate and surface roughness is increased up to 21.27% and 34% respectively and percentage of dimensional deviation is decreased up to 7.62% after deep cryogenic treatment. Scanning electron microscope (SEM) and Energy dispersive spectroscopy (EDS) of WEDM surface has been done for deep cryogenic treated and non cryogenic machined samples. The scanning electron microscope (SEM) of selected samples has been done for average recast layer thickness. It has been concluded from the results that average recast layer thickness is increased after deep cryogenic treatment because large amount of discharge energy is produced during machining in cryogenic workpiece as compared to non cryogenic workpiece. Energy dispersive spectroscopy (EDS) of WEDM samples indicates the accumulation of brass wire elements on the machined surface. Finally a hybrid of TOPSIS and AHP methods is used for parametric optimization of wire electric discharge machining. Ranking of alternative experiments of WEDM has to be done on the basis of coefficient of closeness. The coefficient of closeness found to be maximum at the experimental conditions corresponding to pulse on time: 120 unit (1.1 μs), pulse off time: 50 unit (36 μs), spark gap set voltage: 50 volts and wire feed rate 5 m/min respectively, so these are the optimum parameters setting of WEDM. A MATLAB is used for evaluation of TOPSIS and AHP methods.