A number of (Cr,Mo)-alloyed PM-steels was prepared from commercial powder (3 wt.% Cr, 0.5 wt.% Mo) and sintered to various oxygen levels. The microstructure and the fractographic appearance of these materials were analyzed. Oxygen being generally precipitated as particulate Cr203 was found to be concentrated in planes along former particle boundaries. This spatial configuration controls the nucleation and spacing of micro-voids during plastic deformation of sintering necks and significantly reduces ductility and fatigue resistance upon increasing oxygen content. Considering this effect, it is shown that a reduction of total oxygen content has two major effects: i) Reduced oxygen content increases strength and hardness since it leaves more Cr available for hardening purposes ii) Less chromia precipitates contribute to better dynamic and static toughness properties, i.e. they improve strain to fracture, fatigue strength and impact work. Finally it is shown that (Cr,Mo)-PM-steels combining both high strength and good ductility can be obtained by high temperature sintering which reduces the oxygen content of such materials below 0.05 wt.%
Impact of oxygen on the microstructure and fracture morphology of Fe(Cr,Mo)-PM steels
2003
14 Seiten, 9 Bilder, 1 Tabelle, 19 Quellen
Aufsatz (Konferenz)
Englisch
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