Surface texture and integrity of electrical discharged machined titanium alloy
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ORIGINAL ARTICLE
Surface texture and integrity of electrical discharged machined titanium alloy P. Karmiris-Obratański 1,2 & K. Zagórski 1 & E. L. Papazoglou 2 & A. P. Markopoulos 2 Received: 15 August 2020 / Accepted: 24 September 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract Electrical discharge machining (EDM) is a non-conventional machining process, extensively applicable in the modern industry. Owing the non-contact nature of the process, any electrical conductive material can be machined in high quality, regardless its mechanical properties. Titanium alloys are commonly machined by EDM, as difficulties related with their low thermal conductivity and the high chemical reactivity can be overcome. As titanium alloys are utilized in quality demanding applications and industries, high machined surface quality is required, as well surface integrity. The current study presents an experimental investigation of how ED machining parameters affect the MRR, the TWR, and the SQ on machining Titanium Grade 2 by EDM. For pulse current 9/13/17/25A, and pulse on time 25/50/100/200 μs, a full-scale experiment has been carried out, using graphite electrode. The surface texture (ST) has been estimated in terms of arithmetic mean height (Sa), maximum height of scale-limited surface (Sz), and skewness of the scale-limited surface (Ssk), while also measurements of the surface waviness were conducted as well. For all the aforementioned parameters an analysis of variance (ANOVA) has been performed. Finally, the surface topography and integrity were evaluated through optical and SEM microscopy observation, through which the surface cracks and micro-cracks due to high pressure and temperature gradients can be distinguished and characterized. Keywords EDM . Titanium Grade 2 . Surface texture and integrity . ANOVA . Cracks and micro-cracks
Nomenclature Elst Working electrode weight before the machining (g) Elfin Working electrode weight before the machining (g) IP Pulse on current (A) MRR Material removal rate (mm3/min) Sa The arithmetic mean of the absolute of the height within a definition area A (μm) Ssk The skewness of the scale-limited surface Sz The sum of the largest peak height and pit height value within a definition area in [μm] Ton Pulse on time (μs) TWR Tool wear ratio Wst Workpiece weight before machining (g) * A. P. Markopoulos [email protected] 1
Faculty of Mechanical Engineering and Robotics, Department of Manufacturing Systems, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Cracow, Poland
2
School of Mechanical Engineering, Laboratory of Manufacturing Technology, National Technical University of Athens, Heroon Polytechniou 9, 15780 Athens, Greece
Wfin tmach ρ
Workpiece weight after machining (g) Machining time (min) Workpiece material density (g/mm3)
1 Introduction Electrical discharge machining (EDM) is considered as one of the earliest non-conventional machining processes, which still finds extensive use in the modern industrial environment. The inherent uniqu
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