Investigation of the effect of Ti6V4Al powder additive in EDM machining of cocrmo alloy

CoCrMo is one of the materials widely used as biomaterial in biomedical technology. In this study, the effect of powder addition on the electro erosion machining of this material, which has good wear and corrosion resistance and high mechanical properties, was investigated. Ti6V4Al powders were added to the dielectric liquid (DIELEKTRIKUM 358) at different concentrations (0, 2 g/l, 4 g/l, 8 g/l) during electro erosion machining. As electro erosion processing parameters; 4 different peak current (9 A, 12 A, 15 A, 18 A), 4 different pulse duration (180 μs, 240 μs, 300 μs, 360 μs), 4 different off time (18 μs, 24 μs, 30 μs, 36 μs) were determined. AISI 316L stainless steel was used as the electrode material and all experimental processes were carried out with a constant processing time of 10 minutes. Experimental sets were determined by Taguchi Analysis (4x4) and surface roughness (Ra / Rz), tool wear rate and workpiece wear rate were evaluated by creating regression models with the response surface method and creating three-dimensional (3D) surface models. In addition to these, surface properties were evaluated with SEM images and EDS analyzes on both the machining surface and the cross-section of the machined surface, while the residues formed by the electrode, workpiece and additional powder on the workpiece were also examined. As a result of the investigations carried out, the minimum Ra value was obtained as a result of the processing in the experimental parameters with dust ratio (w) = 8 g/l, peak current (I) = 9 A, pulse time (Ton) = 360 µs, waiting time (Toff) = 36 µs. The minimum Rz value was realized as a result of processing with the experimental parameters of dust content (w) = 8 g/l, peak current (I) = 18 A, pulse duration (Ton) = 180 µs, dwell time (Toff) = 36 µs. The most important factor affecting the workpiece wear rate (MRR) is the peak current (I). After the peak current, the factors that affect the wear rate of the workpiece are, respectively, the stroke time (Ton), dust rate (w) and dwell time (Toff). Among these factors, w and Toff affect the workpiece wear rate negatively. The effect of peak current on workpiece wear rate increases at high dust rates. While peak current (I) and powder rate (w) are important accelerating factors for tool wear rate (TWR), the effect of stroke duration (Ton) and dwell time (Toff) is limited. All factors have an accelerating effect on TWR. As a result of SEM images and EDS analysis, it is seen that the frequency of the residues seen on the surface decreases with the increase in the powder ratio. It is seen that the increase in current generally decreases the residue density. It is observed that the powder material does not leave a significant residue. It is thought that the particles that break off at low dwell times do not have time to move away from the surface. With the increase in current, fluctuations on the surface increase, as well as cracks are formed with the temperature differences. Since high currents create a temperature difference between the surface and deep regions, it is observed that the cracks go deeper. It was observed from the cross-sectional images that the fragments broken off from the workpiece and electrode were also embedded in the hot surface.