Microstructural Evolution of a Pre-Alloyed Duplex Stainless Steel 2205 with Boron Addition Prepared by Powder Metallurgy

The addition of hard particles such as borides to a ductile stainless steel matrix can be very efficient for improving mechanical properties. Powder metallurgy represents a suitable route for developing these material modifications, combining high reproducibility and cost-effectiveness. The present research investigated the effect of sintering time on an atomized, pre-alloyed 2205 stainless steel with 2.5 wt.% boron, using two different powder size distributions: fine (<45 µm) and coarse (250–500 µm). Cold uniaxial compaction was conducted using a cylindrical closed die. Sintering was carried out at 1200 °C with a dwell time of 2 and 4 h in argon atmosphere. Microstructural investigation showed that borides were formed in the powder’s atomization step and presented a small size with different morphologies. The borides significantly improved the hardness and compression strength. Compared to the reference 2205 stainless steel, specimens prepared with the fine powder size distribution achieved a twofold enhancement in yield stress, while hardness increased by 26%.