Properties of duplex stainless steels made by powder metallurgy

Purpose: of this paper was to examine the mechanical properties of duplex stainless steels. Design/methodology/approach: In presented study duplex stainless steels were obtained through powder metallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements, such as Cr, Ni, Mo and Cu. In the studies behind the preparation of mixes, Schaeffler's diagram was taken into consideration. Prepared mixes have been sintered in a vacuum furnace with argon backfilling at 1260 °C for 1 h. After sintering: rapid cooling have been applied in argon atmosphere. Produced duplex stainless steels have been studied by scanning and optical microscopy. Mechanical properties such as tensile strength, impact energy, hardness and wear rate were evaluated. Findings: According to achieved results, it was affirmed that applied sintering method as well as powder mixes preparation allows for manufacturing the sintered duplex steels with good mechanical properties which depends on austenite/ferrite ratio in the microstructure and elements partitioning between phases. The additions of alloying elements powders (promoting formation ferritic and austenitic phase) to master alloy powder, makes possible the formation of structure and properties of sintered duplex stainless steels. Sintered duplex steels obtained starting from austenitic and ferritic powders with admixture of elemental powders achieve lower mechanical properties when compared to composition obtained by mixing ferritic and austenitic powder in equal amounts. Research limitations/implications: According to the powders characteristic, the applied fast cooling rate seems to be a good compromise for mechanical properties and microstructures, nevertheless further tests should be carried out in order to examine different cooling rates. Originality/value: The use of elemental powders added to a stainless steel base showed its potentialities, in terms of fair compressibility and final sintered density. In addition a good microstructural homogeneity and first of all mechanical properties and corrosion resistance was achieved, also working with cycles possible for industries.