The selection of phase composition of silicon nitride ceramics for shaping with the use of EDM machining

Purpose: The purpose of this study is the selection of phase composition of Si3N4 matrix ceramics with the addition of conducting phases so as to make shaping of those materials possible by means of electro discharge machining (EDM). Silicon nitride matrix materials with the addition of oxide phases (Al2O3, MgO, ZrO2) and conducting phases (TiB2, TiN) were sintered by the method of SPS (Spark Plasma Sintering). Additionally the effect of oxide phases on silicon nitride sintering capacity, the value of electric resistance of nitride ceramics depending on the addition of a conducting phase and the effect of sintering parameters on selected features of produced materials were determined. Design/methodology/approach: Materials were sintered with the use of a SPS device marked with FCT-HP D 5. Apparent density Pp was measured by the hydrostatic method. Hardness was determined by the Vicker’s method at the load of 980.7 mN with the use of a Future Tech Corp digital hardness tester FM7. For the purpose of those tests a surface was prepared with the use of a Struers cutting grinder ACUTOM. Measurements of Young’s modulus for sintered samples were carried out using a ultrasonic method of transverse and longitudinal wave speed measurement with the use of a Panametrics Epoch III detector. Resistance measurement was done with the use of Wheatstone and Thomson technical bridges. Findings: The addition of titanium nitride had no effect on the reduction of electric resistance of Si3N4 matrix ceramics. The lack of electric conductivity of those materials is the result of used additions influencing sintering capacity, mainly magnesium oxide. Si3N4 matrix materials with the addition of titanium diboride are characterised by low electrical resistance with high physical and mechanical features maintained. Electric conductivity of those materials and the initial electro discharge cutting attempts prove that it is possible to shape Si3N4 matrix ceramic materials with the addition of a TiB2 phase with the use of EDM process. Practical implications: The use of EDM will enable the production of elements with complicated shapes (impossible to achieve by other shaping methods) from ceramic materials (with Si3N4 matrix). Originality/value: By the appropriate selection of a conducting phase addition it is possible to increase electric conductivity of silicone nitride matrix ceramics, for which it is possible to shape products by means of electro discharge machining.