Sintering of Cr-prealloyed PM steels requires atmospheres with good quality – low oxygen potential – to achieve satisfactory sintering results. But during heating even the best atmospheres may be oxidizing, the system turns to reducing conditions only at high temperatures, which can be monitored by thermal analysis. During the dewaxing process, oxidizing conditions are favourable for effective dewaxing without sooting and blistering. However, this may result in some oxygen pickup during heating, and then the final properties of the produced parts may be strongly influenced by this intermediate oxidation. This study demonstrates the behaviour of artificially oxidized steels (Fe-C and Fe3Cr-0.5Mo-C) during the sintering process by stepwise sintering. Iron and steel powder were slightly oxidized and then pressed and sintered at different temperatures. In parallel, as a second approach, pressed samples were oxidized and then sintered. Density, hardness and impact energy were measured and dilatometry/MS was used for online monitoring of the sintering process. The starting oxygen content of 0.20 to 0.30 wt% is high enough to change the sintering behaviour of the materials, but still leads to rather good properties. Thermal analysis showed that most of the oxygen picked up was present as iron oxides on the surface which were reduced by hydrogen at rather low temperatures, confirming that these were iron oxides, which also holds for the Cr-prealloyed variant. The biggest influence on the final performance was exerted by the final carbon content and the microstructural development of the material.
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 Chasoglou, D., Hryha, E., Norell, M., Nyborg, L: Applied Surface Science, vol. 268, 2013, p. 496
 Nyborg, L., Hryha, E. In: Advances in Powder Metallurgy & Particulate Materials 2014, Proceedings of the 2014 International Conference on Powder Metallurgy & Particulate Materials. Orlando, FL, MPIF, Princeton NJ, 2014, Vol. 2, p. 153
 Chasoglou, D., Hryha, E., Nyborg, L. In: Proc. Euro PM2009, Copenhagen, Denmark, Oct. 12-14, EPMA, UK 2009, Vol. 2, p. 181
 Chasoglou, D., Hryha, E., Nyborg, L. In: Proceedings of World PM2010, Florence, EPMA, Shrewsbury UK, 2010, Vol. 2, p. 3
 Gierl-Mayer, C., Danninger, H., De Oro, R., Hryha, E. In: Advances in Powder Metallurgy and Part. Materials 2014; Proceedings of World PM Orlando, Florida May 18-22 2015, Eds. R.A. Chernenkoff, W.B. James, p. 05-74
 Gierl-Mayer, C., Danninger, H. In: Lecture at: International Conference on Sintering 2014, Dresden; 24.-28.08.2014
 Danninger, H., Nikolov, D., Leitner, G., Jaenicke-Rößler, K. In: Proc. Int. Conf. “Sintering ‘03”, State College PA, 2003
 Kremel, S., Danninger, H., Yu, Y.: Powder Metall. Progress, vol. 2, 2002, no. 4, p. 211
 Danninger, H., Gierl, C.: Materials Chemistry and Physics, vol. 67, 2001, no. 1-3, p. 49
 Momeni, M., Gierl, C., Danninger, H.: Powder Metallurgy Progress, vol. 8, 2008, no. 3, p. 183
 Gierl-Mayer, C., Calderon, R., Danninger, H.: JOM, vol. 68, 2016, no. 3, p. 920