Taguchi-based analysis of WEDM performance of cryogenically treated and untreated Inconel 718: Surface roughness, kerf width, and material removal rate

This study investigates how deep cryogenic treated (DCT) affects the machining characteristics and surface morphology of Inconel 718 during wire electrical discharge machining (WEDM). Surface roughness (R a , R q , and R z ), kerf width (KW), and material removal rate (MRR) were analyzed for both cryogenic treated (CT) and untreated (UT) workpieces. Using a Taguchi L 9 orthogonal array, the effects of voltage (V), liquid pressure (LP), and wire feed rate (WF) were examined at three levels. Experiments were conducted using deionized water as the dielectric and a 0.25-mm-diameter brass wire electrode. The results show that cryogenic treated influences machining performance by improving surface morphology and modifying the KW response under the investigated WEDM conditions. Quantitative analysis further showed that CT increased hardness by approximately 8.7%, reduced the resolidified globule area by up to 37.9%, and decreased the mean crater area by approximately 20.1% compared with the untreated condition. Furthermore, S/N ratio analysis showed that voltage was dominant for surface roughness in UT workpieces (V > WF > LP) and wire feed rate was dominant in CT workpieces (WF > LP > V), while KW and MRR followed WF > LP > V (UT) and LP > WF > V (CT). Minimum R a /R q /R z values were 3.819/4.679/22.192 µm (UT, at low V-high LP-low-to-medium WF) and 3.849/4.775/23.491 µm (CT, at high V-high LP-low WF); although UT reached a marginally lower absolute minimum, CT gave lower roughness across most machining conditions, indicating an overall beneficial effect of cryogenic treated. LP also governed KW and MRR in CT workpieces, giving a minimum KW of 0.477 mm and maximum MRR at 65 V-11 kg/cm 2 LP-12 m/min WF, while wire feed rate governed both in UT workpieces, with maximum MRR at 55 V-7 kg/cm 2 LP-9 m/min WF. This research demonstrates that integrating DCT with Taguchi-based parameter optimization offers a promising strategy for improving the overall surface morphology of WEDM-machined Inconel 718 in high-precision manufacturing applications.