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

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.