Investigation of electrochemical machining characteristics of 20MnCr5 alloy steel using potassium dichromate mixed aqueous NaCl electrolyte and optimization of process parameters

Abstract

Electrochemical machining is a modern machining technique that plays an important role in the applications of aerospace, die and electronic industries. Electrochemical machining is used to machine difficult-to-machine materials and complex shapes. Machining of alloy steels especially 20MnCr5 is very important for its wide variety of applications such as piston bolts, spindles, camshafts, gears, shafts and other mechanical controlling parts. Machining of the above components with conventional machine tools is a burdensome task. Hence, in this work, an investigation was made to study the electrochemical machining characteristics of 20MnCr5 alloy steel. Two electrolytes, namely, aqueous sodium chloride (NaCl) and potassium dichromate (K2Cr2O7) mixed aqueous NaCl, were used to investigate the machining performance. K2Cr2O7 was selected for its oxidizing characteristics and was included in small proportions in aqueous NaCl bath. The influence of predominant electrochemical machining process parameters such as applied voltage (V), inter electrode gap and electrolyte concentration was studied on the material removal rate and surface roughness (Ra). Scanning electron microscope photography of surface of the 20MnCr5 specimen machined with electrochemical machining was studied to understand the effect of electrolytes during the machining. The contour plots were generated to study the effect of process parameters as well as their interactions. It was noted in the study that the presence of K2Cr2O7 in aqueous NaCl electrolyte increases the material removal rate significantly. The process parameters are optimized through genetic algorithm-desirability function. Optimized operating conditions were found to be quite close with experimental results.

Enhancing the performance of electrochemical machining of 20MnCr5 alloy steel and optimization of process parameters by PSO-DF optimizer

“…Ayyappan et al [12] conducted experimental investigation on ECM characteristics of 20MnCr5 alloy steel using potassium dichromate (K 2 Cr 2 O 7 ) mixed aqueous NaCl electrolyte in the direction of enhancing MRR. Since the selection of ECM machining parameters and design of experiments in the previous work [12] are same as in this work, experimental results of MRR for both aqueous NaCl and K 2 Cr 2 O 7 mixed aqueous NaCl are used to compare the present work. In Fig.…”

“…The main process parameters governing the ECM process are voltage (V) setting, IEG and electrolyte concentration (EC) according to the earlier researches [12,13,[15][16][17][18][19][20]22]. Therefore, these parameters are considered in this work and its levels are shown in Table 1.…”

“…The change in anodic dissolution rate is also caused by the change in the conductivity of electrolyte and composition and properties of oxide film on the metal surface. Potassium dichromate mixed aqueous NaCl was used in ECM for machining 20MnCr5 alloy steels because of its enhanced conductance and oxidizing power, and the results show that sensible increase in material removal rate (MRR) [12]. Passivating layers on the machined specimen may reduce the electrolyzing current.…”

“…RSM is a technique can replace the complicated analysis which requires hours of run time to get equivalent response surface by a few numbers of runs. The effectiveness of RSM for the design and analysis of experiments was proved in many research works [12,13,[15][16][17][18][19][20]. Central composite design provides (CCD) highquality predictions over the entire design space to BoxBehnken design.…”

Electrochemical micromachining: An introduction

“…Others have also demonstrated successful machining processes using mixed electrolytes. 5,10,57,58 The electrolyte also serves the purpose of removing the reaction products from the machining gap. 14 The gap in ECM between the tool and the workpiece is very small, just a matter of micrometres, to enhance the resolution of the machining as explained above.…”