Investigation of the effect of cryogenic process on inconel 718 workpiece machined by wire electrical discharge machining

In this experimental thesis study, the machining of Inconel 718 workpiece on a wire electro-discharge machine was investigated. The effect of the cryogenic process on the kerf (cutting width), metal removal rate (MRR) and average surface roughness (Ra), quadratic average roughness (Rq) and maximum roughness (Rz) values measured on the surfaces of the machined workpiece were examined. In order to better understand the effect of the cryogenic process, the same processes were applied to the untreated workpiece. In this context, the machining parameters used in the processing experiments were chosen as three different wire feed speeds, voltages and dielectric fluid pressures. Dielectric liquid (pure water) was used as the cooling fluid used in the machining experiments and 0.25 mm brass wire was used as the wire electrode. Taguchi L9 (3^3) orthogonal array was preferred to reduce the number of experiments performed and costs. The surface roughness values (Ra, Rq and Rz) obtained as a result of the cutting experiments were obtained from the machined surface of both cryogenically treated and untreated workpieces. According to Taguchi signal/noise ratios, it was determined that the most effective processing parameter on the surface roughness values for the untreated workpiece was "voltage", while it was "wire speed" for the cryogenically treated workpiece. Optimum Ra, Rq and Rz surface roughness values were obtained at voltage 45 V, liquid pressure 15 kg/cm2 and wire speed 9 m/min for the untreated workpiece. For the cryogenically treated workpiece, the voltage was 65 V, the liquid pressure was 11 kg/cm2 and the wire speed was 6 m/min. When the kerf values obtained from cryogenically treated and untreated workpieces were compared, it was seen that the kerf values with which cryogenic treatment was applied were lower. When evaluated in terms of metal removal rate, it was concluded that less chip was removed in cryogenically treated workpieces. Additionally, SEM imaging was performed to analyze the machined surfaces of cryogenically treated and untreated workpieces.