Material removal rate and electrode wear study on the EDM of silicon carbide

(BQ) This study was made only for the finish stages and has been carried out on the influence of five design factors: intensity supplied by the generator of the EDM machine (I), pulse time (ti), duty cycle (η), open-circuit voltage (U) and dielectric flushing pressure (P), over the two previously mentioned response variables. This has been done by means of the technique of design of experiments (DOE), which allows us to carry out the above-mentioned analysis performing a relatively small number of experiments. In this case, a 25−1 fractional factorial design, whose resolution is V, has been selected considering the number of factors considered in the present study.
Nội dung trích xuất từ tài liệu:
Material removal rate and electrode wear study on the EDM of silicon carbideJournal of Materials Processing Technology 164–165 (2005) 889–896Material removal rate and electrode wear study onthe EDM of silicon carbideC.J. Luis, I. Puertas ∗ , G. VillaMechanical, Energetics and Materials Engineering Department, Manufacturing Engineering Section, Public University of Navarre,Campus de Arrosadia, Pamplona, Navarre 31006, SpainAbstractIn this work, a material removal rate (MRR) and electrode wear (EW) study on the die-sinking electrical discharge machining (EDM) ofsiliconised or reaction-bonded silicon carbide (SiSiC) has been carried out. The selection of the above-mentioned conductive ceramic wasmade taking into account its wide range of applications in the industrial field: high-temperature gas turbines, bearings, seals and lining ofindustrial furnaces. This study was made only for the finish stages and has been carried out on the influence of five design factors: intensitysupplied by the generator of the EDM machine (I), pulse time (ti ), duty cycle (η), open-circuit voltage (U) and dielectric flushing pressure(P), over the two previously mentioned response variables. This has been done by means of the technique of design of experiments (DOE),which allows us to carry out the above-mentioned analysis performing a relatively small number of experiments. In this case, a 25−1 fractionalfactorial design, whose resolution is V, has been selected considering the number of factors considered in the present study. The resolutionof this fractional design allows us to estimate all the main effects, two-factor interactions and pure quadratic effects of the five design factorsselected to perform this study.© 2005 Elsevier B.V. All rights reserved.Keywords: EDM; Manufacturing; Wear; DOE1. IntroductionElectrical discharge machining (EDM) is a non-traditionalmanufacturing process based on removing material from apart by means of a series of repeated electrical dischargesbetween a tool, called the electrode, and the part being machined in the presence of a dielectric fluid. At present, EDMis a widespread technique used in industry for high-precisionmachining of all types of conductive materials such as: metals, metallic alloys, graphite, or even some ceramic materials,of any hardness [1].The term, technical ceramic materials or advanced ceramic materials, is a relatively new term, which is applied to arange of various materials generally obtained from inorganicprimary materials with a high grade of purity. These primarymaterials are subjected to typical processes in powder metallurgy technology and subsequently, to high-temperature sintering processes. With these materials, it is possible to obtain∗Corresponding author. Tel.: +34 948 169 305; fax: +34 948 169 099.E-mail address: inaki.puerta@unavarra.es (I. Puertas).0924-0136/$ – see front matter © 2005 Elsevier B.V. All rights reserved.doi:10.1016/j.jmatprotec.2005.02.045high-density parts which have excellent technical propertiesrelated to hardness, mechanical resistance, wear, and corrosion [2].In spite of their exceptional mechanical and chemicalproperties, ceramic materials have only achieved a partialacceptance in the field of industrial applications due to thedifficulties in processing and the high costs associated withtheir manufacture. Over the past few years, the advances inthe field of EDM have permitted the application of this technology to the manufacture of conductive ceramic materials.In line with current knowledge, the main inconvenience whenapplying the EDM technology to the field of ceramic materials is the electrical resistivity of these materials, where thelimits are fixed between 100 and 300 cm [2–4].In this work, the selected ceramic material has been siliconised or reaction-bonded silicon carbide (SiSiC), whosefield of applications is in constant growth. In this way, a material removal rate (MRR) and electrode wear (EW) studyhas been carried out on the influence of the following design factors: intensity (I), pulse time (ti ), duty cycle (η),open-circuit voltage (U) and dielectric flushing pressure (P).890C.J. Luis et al. / Journal of Materials Processing Technology 164–165 (2005) 889–896This has been performed using the techniques of designof experiments (DOE) and multiple linear regression analysis. In this case, a 25−1 fractional factorial design withresolution V has been employed to carry out the presentstudy.2. Equipment used and conductive ceramic EDMedIn this section, a brief description of the EDM machineused to perform the experiments and the conductive ceramicmaterial studied in this work will be given.2.1. Die-sinking EDM machineThe equipment used to perform the experiments was adie-sinking EDM machine of type ONA DATIC D-2030-S(Fig. 1). Also, a jet flushing system in order to assure theadequate flushing of the EDM process debris from the gapzone was employed. The dielectric fluid used for the EDMmachine was a mineral oil (Oel-Held Dielektrikum IME 82)with a flash point of 82 ◦ C. The electrodes used were made ofelectrolytic copper (with a cross-section of 12 mm × 8 mm)and the polarity was negative.2.2. Reaction-bonded or siliconised silicon carbideF®silicon carThe ceramic material used was REFELbide. This reaction-bonded silicon carbide (SiSiC) is manufactured by infiltrating silicon into a porous block made ofsilicon carbide powder and carbon, which is then submittedto a firing process at a specific temperature. This producesFig. 1. EDM machine used to carry out the experiments.approximately 10% of free silicon, which fills the pores. Theresulting microstructure has a low level of porosity and avery fine grain, giving a density of 3.1 g/cm3 . The mechanical resistance of the material (2000–3500 MPa to compression and 310 MPa to tension, up to 1350 ◦ C), combined witha hardness (25–35 GPa, Vickers hardness) whic ...