EDM technology and strategy development for the manufacturing of complex parts in SiSiC

Silicon carbide (SiC) is an extremely hard and difficult-to-shape engineering ceramic material used extensively in industry because of its superior mechanical properties, wear and corrosion resistance even at elevated temperature. Conventional ceramic processing and structuring techniques such as injection molding and grinding are costly and difficult to obtain flawless complex shaped components. By infiltrating free Si into the SiC, the electrical conductivity of the matrix is largely improved. Thus it can be machined by electrical discharge machining (EDM). In this paper, a die-sinking EDM technology for manufacturing components in a commercial available silicon infiltrated silicon carbide (SiSiC) is developed. The influences of the major operating EDM parameters (discharge current image, open gap voltage image, discharge duration image and pulse interval image) of the iso energetic generator on the machining performances like Material Removal Rate (MRR), Tool Wear Ratio (TWR) and surface roughness (Ra) are examined. Relaxation pulses which have lower energy input are also considered to improve the surface quality. Furthermore, the topography and surface integrity of the material after the EDM process are analysed to determine the corresponding material removal mechanism. With the developed machining strategy, a sample piece with designed features such as ribs, a deep cavity and chamfers are manufactured to examine the machining performances.