Influence of machining parameters on electrochemical grooving of cylindrical Stellite 21 components

Purpose This study aims to evaluate the effects of cathode material, pulse-on time and machining duration on material removal, surface quality and groove geometry during electrochemical grooving (ECG) of hollow Stellite 21 tubes. Design/methodology/approach Grooving of hard-to-cut metals remains a significant challenge in conventional machining due to residual stresses, tool wear and microcrack formation. Findings Experiments using SS304 and brass cathodes revealed that SS304 achieved approximately 7.6% higher material removal than brass under a 1 s pulse-on time and 75 s machining duration. Shorter pulse-on times (0.5 s) reduced material removal by up to 40% for both cathodes, indicating limited influence of material under low-duty conditions. Surface roughness was strongly affected by cathode type and pulse duration, with brass achieving the lowest Ra of 0.11 µm at 0.5 s ton and 90 s machining time, corresponding to a 75% improvement compared to the highest Ra of 0.438 µm observed with SS304. Scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS) analyses confirmed pitting and intergranular corrosion as the primary contributors to surface irregularities, mitigated by shorter pulses. Geometrical analysis showed brass maintained around 18% better dimensional accuracy, with depth difference (DD) ranging from 16–30 µm versus 26–30 µm for SS304. Material removal reached equilibrium after 60 s, with further machining increasing removal by only 1%–3.6%. These findings demonstrate that careful cathode selection and pulse optimization can significantly improve material removal, surface quality and dimensional accuracy in ECG of hard-to-cut Stellite 21 tubes. Originality/value To the best of the authors’ knowledge, and based on a meticulous review of the literature, most studies have focused on material removal rate (MRR), machining accuracy and surface quality in the electrochemical machining process. However, research concerning the grooving of inner surfaces remains limited, and this area still has room for enlightenment. Hence, in this research, the mechanism of EC grooving on Stellite 21 samples was investigated and it was aimed to provide a beneficial perspective for demanding industrial applications involving hard-to-cut materials. In this context, grooving was carried out at various EC parameters using two different cathode materials. After this step, MRR, DD, groove depth (GD) and groove width (GW) were measured to assess the grooving performance of the samples in detail. Finally, the grooves were analysed by an EDS and SEM to evaluate the surface roughness, GD, GW and machined surface characteristic.