INFLUENCE OF THE PURITY OF THE SINTERING ATMOSPHERE ON THE REDUCTION OF OXIDES DURING SINTERING OF Fe-Cr-MO STEELS

• Published in: Powder Metallurgy Progress Vol. 10; no. 2; pp. 71 - 80
• Main Authors: Hrubovcakova, M, Dudrova, E
• Format: Journal Article
• Language: English
• Published: 01.04.2010
• Subjects: Atmospheres; Density; Oxides; Purity; Reduction; Sintering; Sintering (powder metallurgy); Steels
• ISSN: 1335-8987

The effect of the purity of the 10% H(2)+N(2) sintering atmosphere and cooling rate on the reduction of oxides in Fe-3%Cr-0.5%Mo+0.5C% was investigated. Specimens with a density of 6.9 g-cm-3 were sintered at 1120 degree C for 30 min in the N(2)-rich atmosphere with oxygen contents of 2.0 vpm (purity 5.0) and 0.5 vpm (purity 6.0), respectively. Two different cooling rates, W degree C/min and 50 degree C/min, were used. The contents of the active gases CO, CO(2), and H(2)O were continuously monitored. It is shown that the iron oxide layer at particle surfaces is removed by hydrogen-reduction during the heating stage at 470 degree C. Thermodynamically stable oxides are removed by carbothermic reduction at temperatures higher than 820 degree C. The reducing processes were evaluated on the basis of oxygen-carbon balance in the sintered materials. The elimination of oxide contamination of interfaces results in higher mechanical properties.