Deoxidation And Internal Gettering In Advanced Hybrid Alloyed Sintered Steels

Abstract

In ferrous powder metallurgy, replacing the common alloy elements Ni and Cu by less critical ones such as Cr, Mn and Si is both technically and economically attractive. Combining the masteralloy route with prealloying offers compositional flexibility and rapid homogenization during sintering as well as sinter hardening capability. However, the oxygen affinity of the alloy elements has to be considered. In the present study it is shown that combining starting powders prealloyed with Cr-Mo or Mo with Mn-Si masteralloys results in internal gettering, i.e. oxygen transfer from the base powder to the masteralloy, which shifts deoxidation to higher temperatures. However, the masteralloy thus promotes deoxidation of the base powder particles and consequently enhances interparticle strength even when sintering at moderate temperatures, with just slight loss of alloying effect. This shows that not only the total oxygen content but also the oxygen distribution is of relevance for the mechanical properties.