Effect of chemical composition and sintering conditions on the mechanical properties of sintered duplex stainless steels

Duplex stainless steels were obtained through powder metallurgy technology from austenitic AISI 316L and ferritic AISI 430L powders mixed in different amounts to obtain ratios of austenite/ferrite of 25/75, 50/50 and 75/25. Prepared powder mixes were compacted at 650 or 750 MPa and sintered in N2–H2 atmosphere (95%-5%) at several sintering conditions and with three sintering cooling rates (furnace, gas and water). Mechanical properties were evaluated using tensile testing and macro–microhardness. The cooling rate was the main factor affecting the microstructure. A full microstructural study for the three cooling rates has been performed. The mechanical behaviour was a function of the cooling rate and the chemical composition. For furnace cooling, the sample with 75/25 of austenite/ferrite powders showed the best result. A hardening effect for the water cooling process was observed with the duplex stainless steels.