PSI - Issue 34

T. Silva et al. / Procedia Structural Integrity 34 (2021) 45–50

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Author name / Structural Integrity Procedia 00 (2019) 000–000

and Nair, 2017). The vast potential of the additive manufacturing (AM) assets, such as topological optimization al lied to relatively flexible design constraints, has additionally contributed to its quick evolution. Laser powder bed fusion (LPBF) is currently the most popular technique in MAM due to requiring less support structures and using finer processing conditions (i.e. smaller metal particles and laser spot size) relatively to other MAM technologies, which translates into an increased attainable geometrical complexity (Garcia-Colomo et al., 2020). Moreover, it is generally acknowledged that due to the smaller build rates the process yields parts with higher dimensional accuracy (though requiring finishing post-processing), in addition to a superior as-built surface condition relatively to other MAM processes. Despite the potential of LPBF for processing a wide range of materials, the development of opti mized feedstock is rather challenging (Shoji Aota et al., 2020), meaning that only a small quantity of materials are currently seen as commercial alternatives. When increased performance in terms of yield strength is required, typical of very demanding structural applications, maraging steel (18Ni300) is usually considered due to its excellent combi nation of strength and ductility. Moreover, its lack of carbon enhances weldability and maximizes corrosion resistance due to carbide precipitation, highlighting its suitability towards AM processing (Kro´ l et al., 2020). From manufacturing processes modelling to the validation structural requisites of parts, the numerical simulation is currently one of the most used tools in components design. With the emergence of new (i.e. AMed) materials, a clear characterization need arises, especially given the contemporary tendency towards geometrical complexity in crease (i.e. topological optimization). This work reports the essential input data in FEM software of a popular AMed maraging steel (18Ni300). A wide range of characterization tests was performed in order to establish a comprehensive physical and mechanical characterization, enabling material modelling with state of stress, temperature, metallurgical condition, loading direction and speed consideration. This document intends to be a compilation of material character ization data, the majority of it published elsewhere. Therefore an overview of the material, tests and final results will be presented in a condensed way, the interested readers being directed to the relevant references for further details.

2. Materials and methods

Distinct geometries from the same material sample were used for a through characterization of additively man ufactured (AMed) 18Ni300 maraging steel. A set of processing parameters was selected by the manufacturer as an optimal solution towards part density and mechanical strength maximization, corresponding to a power laser of 400 W, scanning speed of 0.86 m / s, hatch spacing of 95 µ m and a layer thickness of 40 µ m. Figure 1 presents the 18Ni300 buildplate as-received from the manufacturer with the labelled raw geometries and its purpose. After separation from the buildplate, the raw geometries were machined to final specimen dimension. The conventionally manufactured

Fig. 1. Maraging steel 18Ni300 buildplate with labelled distinct as-built geometries and their purpose.

Table 1. Chemical composition (wt%) of AMed and CMed 18Ni300 maraging steel with respect to the standard composition. Ni Co Mo Ti Si Mn C P

S

(MIL-S-46850D, 1986)

18.8-19.0

8.5-9.5

4.6-5.2

0.5-0.8

< 0.10

< 0.10

< 0.03

< 0.01

< 0.01

AMed 18Ni300 CMed 18Ni300

18.80 18.93

8.84 8.92

5.15 4.88

0.65 0.77

0.05 0.02

0.03 0.03

0.02 0.01

< 0.001 < 0.001

< 0.001 < 0.001