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Nickel and Copper-Free Sintered Structural Steels Containing Mn, Cr, Si, and Mo Developed for High Performance Applications

Cias A., Stoytchev M.

Archives of Metallurgy and Materials

2017

Vol. 62, iss. 1

11--17

In an attempt to study the sinterability of potential high-strength nickel-free sintered structural steels containing Mn, Cr, Si and Mo compacts were prepared based on sponge and water atomised iron powders and on Astaloy prealloyed powders. To these were admixed ferromanganese, ferroslicon, and graphite. The samples were sintered at temperatures 1120 and 1250°C in laboratory tube furnaces in hydrogen, hydrogen-nitrogen atmospheres with dew points better than –60°C or in nitrogen in a semiclosed container in a local microatmosphere. After sintering the samples were slowly cooled or sinterhardened. Generally resultant microstructures were inhomogeneous, consisted of pearlite/ bainite/martensite, but were characterised by an absence of oxide networks. Sintering studies performed over a range of compositions have shown that superior strength, ranging beyond 900 MPa, along with reasonable tensile elongation, can be achieved with these new steels.

Development of sintered Mn-(Mo)-(Cr)-C steels.

Mitchell S.C., Wronski A.S., Cias A.

Inżynieria Materiałowa

2001

R. XXII, nr 5

633-646

The potential of manganese and chromium as alloying elements, reflected in their widespread use in wrought medium-to-high strength steels, is still to be realised in Powder Metallurgy alloys. The attempts to sinter Mn [+ Cr] alloys have largely ended in failure, due to either poor mechanical properties or lack of reproducibility. The authors have analysed previously published results and identified the principal reason as lack of process control: both in powder preparation and during sintering. This leads to large-scale oxidation, in the form of brittle networks, and also to lack of diffusion, due to the oxide film barriers. Reviewed now are the necessary processing conditions established for the successful processing of manganese steels. The development of additional chromium and molybdenum alloying is also considered and results are presented which additionally incorporate current areas of research, involving warm compaction, high temperature (including liquid phase) sintering and sinter and air hardening.