Abstract
Electro-discharge grinding has been said to be effective not only on metallic materials but also on ceramic materials. But the latter hasn't been widely accepted up to now because its material removal mechanism is still unknown. To make the mechanism clear, by using NaOH solution as grinding fluid, electro-discharge machining on 4 kinds of ceramics are carried out with a needle electrode. The ceramic materials are alumina and 3 kinds of silicon nitrides which are added with alumina (ASN), magnesia (MSN), yttria and alumina (YASN) respectively. The results obtained are as follows : (1) A pit can be formed on any ceramics, the pit depth varies apparently with the ceramic materials. (2) The removal rates of ASN, Alumina, YASN and MSN become low in turn and are independent on their mechanical properties. (3) In the case of silicon nitrides, the removal rates depend on their sintering additives. (4) The higher the applied voltage, the more the removed volume. (5) High removal rate and low electrode loss are obtained only when the needle electrode is minus. (6) A material removal mechanism is proposed : ceramic materials are mainly removed by corrosion of grain boundary in high temperature electrolyte during discharge.
