Advanced Hybrid Alloyed PM Steels Sintered In The 1140°C Range

Abstract

Hybrid alloying, i.e. combining prealloyed base powders with admixed further alloying elements, is a flexible way to exploit the benefits of different alloying components. For Mn and Si, using masteralloys has shown to be particularly attractive. However, for removing the natural oxygen content of the powder compacts during sintering, high temperatures would be required, which implies economic penalties. In the present study it is shown that also after sintering in the 1140°C range, i.e. at temperatures typical for belt furnaces, attractive combinations of hardness and impact energy can be obtained, in particular when using Mo prealloyed base powders which contain less starting oxygen than a Cr-Mo alloyed variant. Thus, also the final oxygen content is lower, which is beneficial mainly for the impact energy. Combining both Mo and Cr-Mo with the Mn-Si masteralloys decisively improves the hardenability, after gas quenching apparent hardness levels up to 500 HV30 being attained.