Microstructure and mechanical properties of duplex stainless steels sintered in different atmospheres

Present investigation is aimed at developing duplex stainless steels through powder metallurgy route and study the effect of sintering atmospheres on density, mechanical properties and microstructures. Duplex stainless steel composition was prepared from the mixture of 316L and 430L alloyed powders. The powders were mixed in a pot mill for 12 h and compacted at a pressure of 560 MPa. The green compacts were sintered at 1350 degrees C in four different atmospheres such as nitrogen, argon, hydrogen and partial vacuum. Sintered duplex stainless steels were subjected to density measurement, metallography examinations and tensile testing. Duplex stainless steel sintered in partial vacuum showed highest densification of 96% theoretical, tensile strength and ferrite content, when compared with stainless steels sintered in other three atmospheres. Microstructure of stainless steels sintered in argon, hydrogen and partial vacuum showed the bi-phase structure. SEM fractographs of the stainless steels sintered in partial vacuum and hydrogen revealed completely ductile mode of failure.