Influence of oxygen partial pressure in sintering atmosphere on properties of Cr-Mo prealloyed powder metallurgy steel
2007 (English)In: Powder Metallurgy, ISSN 0032-5899, Vol. 50, no 3, 243-249 p.Article in journal (Refereed) Published
Chromium is an attractive alloying element in low alloyed steels since it gives good hardenability at low cost. The drawback with using chromium in powder metallurgy ( PM) grades is its high affinity for oxygen. Thermodynamic calculations show that the oxygen partial pressure should be <4 x 10(-18) atm at 1120 degrees C in order to have reducing conditions for a powder grade prealloyed with 3 wt-%Cr and 0 center dot 5 wt-%Mo, which is supported by sintering experiments. With graphite added to the powder grade, conditions are reducing during sintering at higher partial pressures of oxygen ( up to 10 216 atm) due to favourable conditions locally in the material. Sintering of the powder grade with 0 center dot 35 wt-% graphite added at 1120 degrees C for 30 min at reducing conditions leads to high mechanical properties, although kinetics is insufficient for complete reduction of chromium oxides. At 1250 degrees C, kinetics is faster and practically all oxides are reduced after sintering for 30 min, with enhanced mechanical performance as result.
Place, publisher, year, edition, pages
2007. Vol. 50, no 3, 243-249 p.
PM steel, chromium, sintering, oxygen partial pressure, oxide reduction
IdentifiersURN: urn:nbn:se:kth:diva-9552DOI: 10.1179/174329007X205073ISI: 000250730700035OAI: oai:DiVA.org:kth-9552DiVA: diva2:117459
QC 201011052008-11-132008-11-132010-11-05Bibliographically approved