Composition and tempering of FeC and FeNiC fine particles prepared by spark erosion

FeC and FeNiC powders prepared by spark synthesis from pure Fe, FeNi and C as electrodes were investigated. They exhibit a wide variety of particles differing in form, size and phase composition. The as-prepared powders consist of graphite, carbides, α- and γ-Fe, non-magnetic phases and a new ferromagnetic component. Carbides dominate among the ferromagnetic phases. The fractions exhibiting superparamagnetic behaviour contain fine Fe and FeC particles in graphite. Changes in the phase composition due to tempering at elevated temperatures lead to the FeC equilibrium.