Abstract
Commercially pure (C.P.) iron powders with a deliberate high degree of oxidation were consolidated by medium-frequency electrical resistance sintering (MF-ERS). This is a consolidation technique where pressure, and heat coming from a low-voltage and high-intensity electrical current, are simultaneously applied to a powder mass. In this work, the achieved densification rate is interpreted according to a qualitative microscopic model, based on the compacts global porosity and electrical resistance evolution. The effect of current intensity and sintering time on compacts was studied on the basis of micrographs revealing the porosity distribution inside the sintered compact. The microstructural characteristics of compacts consolidated by the traditional cold-press and furnace-sinter powder metallurgy route are compared with results of MF-ERS consolidation. The goodness of MF-ERS versus the problems of conventional sintering when working with oxidized powders is analyzed. The electrical consolidation can obtain higher densifications than the traditional route under non-reducing atmospheres.
Highlights
The electricity can be used to sinter a conductive powder mass that is passed through by the current, as numerous times has been suggested during the last century, and still remaining as an issue of extraordinary interest at present
Regarding the many conceived modalities, maybe the simplest is one of the firstly proposed, consisting in a high intensity and low voltage electrical current passing through a powder mass of conductive powders placed inside an insulating die, and being simultaneously under pressure
Besides the peculiar temperature distribution of the medium-frequency electrical resistance sintering (MF-Electrical Resistance Sintering (ERS)) process, another factor that could contribute to the non-uniform and higher porosity in some of the MF-ERS compacts is the release of gases during heating
Summary
The electricity can be used to sinter a conductive powder mass that is passed through by the current, as numerous times has been suggested during the last century, and still remaining as an issue of extraordinary interest at present. Keywords electrical resistance sintering; MF-ERS; FAST; ECAS; Iron; hot pressing; sintering; powder metallurgy doi:10.20944/preprints201805.0168.v1 MF-ERS experiments were carried out with different current intensities and heating times.
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