Effectiveness of Different Reducing Agents during Sintering of Cr-Prealloyed PM Steels

Paper i proceeding, 2013

Development of strong inter-particle necks requires successful removal of surface oxides, present on the powder particles, during initial stages of sintering. In the case of water-atomized powder prealloyed with chromium, surface oxide is composed of mainly an iron oxide layer with some presence of more stable fine particulate oxides. Sufficiently strong inter-particle necks require as minimum full removal of the iron surface oxide layer. This can be achieved by a number of gaseous reducing agents (H2, CO or mixture of both) as well as by carbon typically admixed in the form of graphite. The present study is focused on the analysis of the reducing ability of the different sintering atmospheres (concentration of active gases ≤10 vol.%) and their combined effect with graphite by means of thermal analysis. Results indicate that the combination of the dry hydrogen-containing atmospheres and fine graphite grades allows successful sintering of chromium alloyed PM steels.