Abstract
For the purpose of an effective spark sintering, differences of sintering state by the graphite and insulating dies, are investigated with Ni powder. Main results obtained are as follows.
(1) In the case of graphite dies, almost all the initial electric current goes through this dies and nickel powders are heated by this graphite mold. We may not expect the powder itself as a main heater at the first stage of sintering. Temperature distribution in the specimen is small and sintering time is very short (10-15 see).
(2) In the case of insulating die, there exists a critical pressure (below which the current path melts but other part keeps its original powder state) and it is impossible to set the primary pressure considerably low. This results in the slow temperature rise and eventually makes the sintering time longer (40-80 see). Temperature distribution in the specimen is larger than in the case of graphite die.
