Microstructure and Mechanical Properties of PM Steels with Additions of a Mn-containing Master Alloy.

摘要

The marked price increase of raw materials in the international markets, notably Ni and Mo, has motivated the search for cheaper, alternative and metallurgically feasible chemical compositions for PM steels. In this work the design and use of a novel Mn-containing Master Alloy for obtaining a new family of sintered steels with very attractive mechanical properties, dimensional stability and hardenability is presented. The main characteristics of this Master Alloy, in comparison to alternative Mn sources, are described, and the microstructural development of the steels after sintering at 1120oC under typically used industrial atmospheres, is discussed. The hardenability characteristics of these steels based on the preparation of a diversity of powder mixtures containing varying amounts of Mn, Cr, C and/or reduced additions of Mo and Ni were studied. The influence of, both, cooling rate after sintering and tempering temperature on their final tensile properties were also investigated.