Short crack nucleation and growth in lean duplex stainless steels fatigued at room temperature

R. STRUBBIA; S. HEREÑÚ ; M.C.MARINELLI; I. ALVAREZ-ARMAS

Simposio; International Symposium on Fatigue Design & Material Defects; 2011

Norwegian University of Science and Technology, NTNU

Abstract Duplex stainless steels (DSS) are two-phase alloys with approximately equal proportions of ferrite and austenite phases. These steels combine good properties of ferrite and austenite. DSS is an attractive alternative to austenitic grades having higher strength with the same and sometimes better corrosion resistance. The Ni content in current duplex stainless steels is between 4 and 7 weight percent. In the last years  many efforts have been done to reduce Ni and replace it with other low cost elements such as Mn, N etc, to lower the product cost without degradation of corrosion and mechanical properties. This gives rise to a new class of DSS called Lean DSS (LDSS). Although in recent years substructural characterization and corrosion properties of LDSS have been well documented, scarce works are found on their mechanical properties. Even fewer investigations have studied the cyclic behavior of these steels and particularly no information is available on the evolution of the surface damage before microcraking begins. Therefore, the purpose of this paper is to determine the initiation and evolution of fatigue short cracks in LDSS. Moreover, in order to propose a mechanism of microcrack nucleation and propagation internal dislocation structure is analyzed