Abstract
The variation of graphite morphology was investigated in Ni-C compacts (0, 0.5, 1.0 and 2.0 mass%C) after sintering at 1553 K under dry hydrogen flow.
When C content is 0.5% which is less than the solubility limit of C into the Ni-phase at 1553 K, nodular graphite can be obtained after long time sintering. This result suggests the following mechanism; all graphite dissolves into the Ni-phase during heating, pores are spheroidized during sintering, and the supersaturated C precipitates as graphite to the spherical pores during cooling.
When C contents are 1.0% and 2.0% which are more than the solubility limit of C into the Ni-phase, no nodular graphite can be obtained, because of undissolved residual graphite in the pores.
