Effect of sintering cooling rate on corrosion resistance of powder metallurgy austenitic, ferritic and duplex stainless steels sintered in nitrogen

Duplex stainless steels obtained by powder metallurgy from austenitic AISI 316L and ferritic AISI 430L powders were studied. Austenitic stainless steel and ferritic stainless steel were also obtained for comparative purposes. All materials were sintered in nitrogen with three sintering cooling rates: furnace, gas and water. Corrosion resistance using anodic polarization measurements and electrochemical potentiodynamic reactivation tests were evaluated. The cooling rate was a determinant factor. For the duplex and ferritic stainless steels, a beneficial effect on the anodic behaviour and the degree of sensitization for water cooled materials was observed. Gas cooling was preferred for austenitic stainless steel.

► Powder metallurgy stainless steels sintered in nitrogen are characterized.
► Lamellar constituents do not allow the passive films to be stabilized.
► Cooling in water from sintering shows the best corrosion resistance.
► Water-cooled 50/50 (austenite/ferrite) shows the lowest passive current density.
► Low degree of sensitization is found for water-cooled duplex stainless steels.