Low-Voltage Capacitor Electrical Discharge Consolidation of Iron Powder

Abstract

Commercially pure iron powder has been processed by the capacitor electrical discharge consolidation technique. This consolidation technique applies an external pressure and, at the same time, heats a metallic powder mass by the Joule effect of a high-voltage and high-intensity electric current. In this work, a capacitor charged at low voltage has been used instead. The effect of the initial porosity of the Fe powder mass, i.e., of the precompaction pressure, and the number of discharges from the capacitor have been studied. The densification and remaining porosity, the sintering level, the Vickers microhardness, and the electrical resistivity of the sintered compacts have been studied. Compacts sintered by the conventional powder metallurgy route of cold pressing and furnace sintering were also prepared for comparison. Results show that a high initial porosity provides a high electrical resistance in the powder column, a necessary requisite for the Joule effect to increase densification with the number of discharges. Thus, the final porosity decreases to 0.22 after 50 discharges in the powder mass with an initial porosity of 0.30. With this initial porosity, the sintering process increases Vickers microhardness from 29 to 51 HV10 and decreases the electrical resistivity of the powder mass from 3.53 × 10−2 to 5.38 × 10−4 Ω·m. An initial porosity of 0.2 does not make the compacts densify, but a certain bond between particles is attained, increasing microhardness and decreasing electrical resistivity as the number of discharges increases. Lower initial porosities make the powder mass behave as an electrical conductor with no appreciable changes even after 50 electrical discharges.

Keywords

• powder metallurgy
• FAST
• capacitor electrical discharge consolidation
• iron powder