Spacing roughness parameters study on the EDM of silicon carbide

In this work, a surface roughness study on the die-sinking electrical discharge machining (EDM) of siliconised or reaction-bonded silicon carbide (SiSiC) has been carried out. The selection of the above-mentioned conductive ceramic was made taking into account its wide range of applications in the industrial field: high-temperature gas turbines, bearings, seals and lining of industrial furnaces. This study was made only for the finish stages, due to the enormous importance that a good surface quality has over such important properties, in the case of ceramic materials, as: corrosion, fatigue and wear resistance. The present study 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), which are the most relevant parameters to be controlled by the EDM process machinists, over two spacing roughness parameters such as Sm (mean spacing of profile irregularities) and Pc (peak count or peak density). One of the innovations of this work is the roughness parameters selected, Sm and Pc, as against some other much more commonly used ones such as Ra, Rq or Rt. The study of the behaviour of the two previously mentioned spacing parameters has been done by means of the technique of design of experiments (DOE), which allows us to carry out the previous analysis performing a relatively small number of experiments. In this case, a 25−1 fractional factorial design, whose resolution is V, has been selected due to the number of factors considered in the study. The resolution of this fractional factorial design allows us to estimate all the main effects, two-factor interactions and pure quadratic effects of the five design factors selected to perform this study.