Surface Analysis at Different Sintering Stages of Steel Compacts with Mn and Si

Paper in proceeding, 2011

The different stages of sintering have been studied for a gas atomized master alloy containing Fe-Mn- Si-C. Surface characterization and depth profiling of the master alloy powder was performed by means of XPS. In order to understand the phenomena taking place at surface of the green parts, mixes containing plain iron powder, master alloy and graphite were heated in high vacuum (10-6 mbar) at increasing temperatures (400ºC, 600ºC, 800ºC, 1000ºC) and analyzed with XPS. The conditions during the heat treatments described seem to be reducing enough to remove part of the manganese and silicon oxides present at the original surface when the annealing is performed at 800ºC and 1000ºC. However, intensive manganese evaporation was observed when heating at 1000ºC. While the amount of silicon cations on the surface decreases importantly from 800 to 1000ºC, the oxygen concentration in the surface is very similar and this might point out to a recombination of Si cations to form complex Mn-Si oxides. The Mn/Si cations ratio registered indicates that the oxide formed at 1000ºC could be the type MnSiO3.