Abstract:
Laser-powder bed fusion (L-PBF) is a type of additive manufacturing (AM) that involves the addition of metal powders in a sequential layer-by-layer manner to create near-net-shape components. An outstanding characteristic of this technology is its ability to achieve high cooling rates, reaching up to 107 K/s. This unique characteristic has benefits in the production of high-strength stainless steel alloys, as it helps to reduce unwanted phase formation. SAF 2507 super duplex stainless steel (SAF 2507 SDSS), a type of stainless-steel alloy, contains around 25% chromium and 7% nickel, has a unique phase composition with an equal distribution of about 50% ferrite and 50% austenite and characterized by its higher mechanical strength and resistance to corrosion, which are attributed to its high levels of chromium and nickel content along with its low level of carbon. Producing intricate geometry with SAF 2507 using traditional methods with a specific phase composition is challenging and requires post-processing. LPBF is an alternative technology capable of manufacturing near-net-shape components with complicated geometry. It is important to conduct a comprehensive investigation to retain the desired phase composition while fabricating components using L-PBF. Although several studies have investigated the microstructure and mechanical properties of SAF 2507 using L-PBF. However, the influence of different L-PBF process parameters as well as energy density on microstructure and mechanical properties has yet to be investigated. This study examines the influence of L-PBF process parameters (laser power, scan speed, hatch distance) on the microstructure and mechanical properties of SAF 2507 SDSS. Additionally, the corrosion properties are investigated using the established optimum parameters. A design of experiment (DoE) was performed using the central composite design over a wide range of process parameters: laser power (100–300 W), scan speed (250–1000 mm/s), and hatch distance (50–180 μm) to investigate their effect on the microstructural and mechanical properties of SAF 2507. By implementing the selected parameter set, the as-built SAF 2507 SDSS sample had porosity less than 1%, a Vicker hardness ranging from 288 to 357 HV, a yield strength of 824 to 1220 MPa, an ultimate tensile strength of 965 to 1304 MPa, elongation of 6% to 18.1%, and a corrosion rate of 127.65 μm/y was determined. The findings derived from this investigation have the potential to facilitate the customization of component quality by meeting design specifications and minimizing as-built defects, thereby decreasing the need for post-processing.
