Effect of Processing Parameters on Oxide Transformation in Cr-Mn-Prealloyed Sintered Steels

Paper in proceeding, 2013

High-purity water-atomized steel powder grades prealloyed with chromium and manganese are currently available on the market. Amount of surface oxide with higher thermodynamic stability is below 10%, which assumes good sinterability of such powder grades. However, the risk of forming oxide products on the powder surface during critical stages of powder consolidation, especially during heating stage, remains. The present study is focused on the analysis and modelling of effect of processing parameters: sintering atmosphere composition, temperature profile (heating rate and sintering temperature), graphite addition as well as powder composition on the possible scenarios of oxide reduction/formation/transformation for Fe-Cr-Mn-C powder systems. Model of oxide transformation based on the analysis of specimens from interrupted sintering trials using advanced analysis techniques (HRSEM+EDX and XPS) and modelling of thermodynamic stability of oxide phases is presented. Controlled conditions during heating stage allow us to minimize formation of stable oxide products and produce oxide-free sintered parts.