Laser powder bed fusion of 2507 duplex stainless steel: Microstructure, mechanical properties, and corrosion performance

Abstract

Duplex stainless steels offer a unique combination of advantages derived from both ferritic and austenitic structures, providing excellent mechanical properties and corrosion resistance. Nevertheless, conventional metallurgical techniques such as casting and rolling encounter challenges when it comes to the rapid fabrication of intricate components. In this study, we explore the microstructure, mechanical properties, and corrosion performance of 2507 duplex stainless steel manufactured through laser powder bed fusion (L-PBF). Through meticulous refinement of L-PBF parameters, we successfully achieved a dense sample featuring a hardness exceeding 400 HV, a relative density surpassing 98 %, and a surface roughness below 15 μm. This was obtained using a scanning speed of 700 mm/s and a laser power of 210 W. Due to the high cooling rate of L-PBF process, L-PBFed 2507 exhibits a ferritic microstructure distinct from that of rolled 2507 duplex stainless steel. Additionally, a considerable presence of internal dislocations can be observed in the L-PBFed 2507 material. The 2507 stainless steel exhibited an outstanding yield strength of 1198 MPa and an ultimate tensile strength of 1269 MPa, surpassing the performance of rolled 2507 duplex stainless steel. The corrosion current density was nearly negligible (approximately 10−6 A cm−2), with a passivation window expanding 1.2 V relative to the corrosion potential and a passivation platform below 10−4 A cm−2. These corrosion characteristics were comparable to those observed in rolled 2507 duplex stainless steel. This research demonstrates the suitability of L-PBFed 2507 stainless steel in environments requiring high strength and corrosion resistance, thereby opening up avenues for high-performance components in advanced engineering applications.