Effect of porosity on the properties of nickel-free stainless steel obtained by powder metallurgy route

This paper presents the results of research on nickel-free austenitic stain- less steel with the composition Fe-18% Cr-12% Mn, obtained by powder metallurgy, with the use of mechanical alloying of elementary powders, manganese nitride and various process atmospheres. The influence of different protective atmosphere of the process (nitrogen and argon) and the addition of manganese nitride on poros- ity, microstructure, hardness and corrosion resistance of the sinters was described. Steel samples after pressing and sintering at 1200°C (1473 K) in nitrogen were char- acterized by a relative density above 80% and a porosity among 12–19%. In tested materials the pores on the surface are visible in each of the tested materials, which is confirmed by SEM images. The material obtained from powders with manganese nitride after mechanical alloying in nitrogen is characterized by the highest hard- ness and corrosion resistance. The addition of manganese nitride can be another way of introducing nitrogen into nickel-free steel.