PSI - Issue 48

America Califano et al. / Procedia Structural Integrity 48 (2023) 238–243 Califano et al / Structural Integrity Procedia 00 (2019) 000 – 000

239

2

powder materials and, therefore, it is devoted to produce fully dense products. As a manufacturing process, selective laser melting has its own unique strengths and weaknesses. For example, it is usually capable of manufacturing final parts without the requirement of any further processing. Currently, several types of stainless steel have been processed widely via SLM (Afkhami et al., (2019)), as steel provides a broad range of desirable properties like good ductility, high strength, low cost and recyclability; therefore, it is largely used in both industrial and domestic products. However, in general, one of the biggest challenges when dealing with Additive Manufacturing (AM) techniques is that the several process parameters inevitably influence the characteristics of the final obtained components (Alfieri et al., (2022), De Luca et al., (2021), Sepe et al., (2020), Sepe et al., (2022)), both in terms of microstructure (sizes, morphology, grain structure) and possible arising of residual stress fields and defects. For this reason, it is fundamental to investigate the performance and the mechanical behavior of AM components. In particular, the mechanical behaviour under dynamic loading (Foti et al., (2023), Karakaş et al., (2023), Sepe et al., (2021)), is str ongly affected by crack orientation, porosities, heat treatments, corrosion etc. For this reason, in this paper, the fatigue crack propagation behaviour of 17-4 PH stainless steel made by SLM under different crack orientations is presented. The tests were carried out using standard 6.65mm thick compact C(T) specimens tested at R = 0.1 and with a frequency of f = 5 Hz. The main objective was to study the effect of the crack orientation on crack-length vs. number of cycles curves.

Nomenclature a

crack length

AM

Additive Manufacturing thickness of specimens

B

BFS CG C(T)

Back-Face Strain Crack-Gauge Compact-Tension

strain

ɛ

E Young’s modulus EDM Electric Discharge Machining EDM f frequency P max maximum applied load N f number of cycles to failure R loading ratio SLM Selective Laser Melting W width of specimens 2. Materials and methods

The case study is a 17-4 PH stainless steel rectangular plate obtained by means of the SLM technique. It has been manufactured using the commercial EOS GP1 (UNS S17400) powder and with printing parameters reported in Table 1 (Caiazzo & Alfieri, (2021)), in full-melting mode, choosing the z-axis as printing direction (Fig. 1).

Table 1. Printing parameters used for the manufacturing phase Parameter Value Operating laser power [W] 195 Operating wavelength [nm] 1030 Linear scanning speed [m∙s -1 ] 1.2 Hatch distance [mm] 0.09 Layer thickness [mm] 0.02 Focused laser diameter [mm] 0.09