Investigation of Selective Laser Melting of 2205 steel precipitates and heat treatment improvement

Abstract

2205 Duplex Stainless Steel (DSS) is extensively utilized in various structural components due to its exceptional strength and corrosion resistance. However, for complex structural parts that are challenging to process using conventional methods, Selective Laser Melting (SLM) technology offers a viable solution by enabling layer-by-layer solidification. The rapid cooling rates during the forming process effectively suppress the precipitation of detrimental brittle phases like σ, while concurrently promoting a high proportion of ferrite phases within the structure upon cooling to room temperature. This paper investigates the microstructure and properties of 2205 DSS fabricated via SLM. A notable observation was the presence of abundant precipitates along the ferrite grain boundaries. Characterization through Energy-Dispersive X-ray Spectroscopy (EDS) and Transmission Electron Microscopy (TEM) confirmed the presence of χ-phase and nanoscale closely packed hexagonal Cr2N-phase precipitates. The high fault density and precipitates induced by the SLM process significantly enhanced the sample's strength, resulting in a remarkable tensile strength of 1301.69 ± 19.6 MPa and yield strength of 781.2 ± 12.2 MPa. Subsequent cooling via solid solution water treatment at 1050°C yielded a biphase structure with an austenite content of 54.7% and ferrite content of 45 %. The tensile strength decreased to 815.61 ± 16.4 MPa, and the yield strength decreased to 443.245 ± 7.5 MPa, while the elongation increased significantly from 19.03 ± 1.2% to 46.53 ± 0.7%. These findings demonstrate that the material achieved performance levels comparable to forging and hot rolling processes.

Keywords

• Selective laser melting
• 2205 Duplex Stainless Steed
• Precipitates
• Mechanical properties
• Solution treatment