Abstract
Electrical discharge machining (EDM) has recently become very popular for processing titanium alloys, but surface quality is a major problem. During machining, a defect layer inevitably forms on the surface, which can have a negative impact on surface quality. One of the ways to reduce the defect layer is to add powder to the dielectric. However, it is not yet completely clear which powder and in what quantity it should be added to reduce the defect layer. In this sense, the present study aims to investigate the effects of machining parameters on the defect layer in powder-mixed electrical discharge machining of titanium alloys. The main goal is to achieve the minimum thickness of the defect layer by optimally adjusting the input parameters. Experimental studies were performed using the Taguchi orthogonal array L9, considering discharge current, pulse duration, duty cycle, and graphite powder concentration as input parameters. Based on the Taguchi and ANOVA analyses, the discharge current was found to have the greatest effect on the defect layer. In addition, analysis of variance revealed that pulse duration was the second influential parameter, followed by graphite powder and duty cycle. The minimum thickness of the defect layer is obtained at a discharge current of 1.5 A, a pulse duration of 30 µs, a duty cycle of 50%, and a graphite powder concentration of 12 g/L. The results obtained in this study provided answers to some of the unresolved research questions and confirmed the findings that the proposed method can be applied in the industry.