Abstract
Multi-response characteristic optimization is the most desired aspect of the components produced from electric discharge machining (EDM). Obtaining the optimal combination of parameters for surface roughness (SR) and micro-hardness (MH) is always a challenging task as the machining parameters favourable to one performance measure adversely affects the other. The present paper deals with the simultaneous optimization of SR and MH of D2 alloy steel during EDM with tungsten carbide (WC)/cobalt (Co) P/M electrode by considering electrode and machine tool parameters. Experimental run order was planned with Taguchi’s orthogonal arrays (OA) and in the present investigation, it is based on L18 OA. The analysis of variance (ANOVA) performed for the grey relational grade (GRG) showed that the tool parameter “particle size” (PS) is the most influential factor (61.43%) for simultaneous improvement of performance measures. The P/M electrode made of fine particle size (i.e., at nano level) has improved the process stability and reduced the arcing and short-circuiting results in reduced surface roughness. Simultaneously, the formation of the hard intermetallic phase’s viz., Fe3C, Cr23C6, W2C, Fe6W6C, and Cr2Fe14C on the EDMed surface has increased the surface hardness. The optimal set of parameters was validated through confirmation experiments.
Highlights
electric discharge machining (EDM) is the most common method for machining difficult to machine materials like high strength and high thermal resistant materials
analysis of variance (ANOVA) to grey relational grade (GRG) shows that the most significant parameter is given in Table 5 is “particle size” (PS) with a wt% of 61.43%, followed by compaction pressure (CP) of 18.3%, %Co of 8.86% and the remaining all other parameters with a minor influence on the performance of measures during simultaneous optimization of surface roughness (SR) and MH
The following conclusions are drawn from the present investigation on the simultaneous optimization of SR and MH by taking into account of machine tool and electrode parameters
Summary
EDM is the most common method for machining difficult to machine materials like high strength and high thermal resistant materials. The majority of the reported literature concentrated on optimizing machining parameters only and very less on tool electrodes in general and limited on the influence of particle size variations in particular. Kumar et al [7] machined the AA7050B4C by EDM route and estimated the performance measures using GRA technique They obtained better results for an optimal combination of machining parameters by Grey-Taguchi technique than TOPSIS-Taguchi technique. There is a dearth of information about the influence of tool parameters on simultaneous optimization in general and P/M electrodes fabricated with nano particles in particular. The present study's primary focus is the simultaneous improvement of two performance measures viz., SR and MH using GRA in the machining of D2 steel with WC/Co P/M electrodes fabricated by varying particle sizes from nano to micron and a combination of both. The density and electrical resistivity values for all the WC/Co P/M electrodes show some variation but the range is within the required limits desirable for any EDM electrode for performing efficient machining
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