PSI - Issue 65

Boris Voloskov et al. / Procedia Structural Integrity 65 (2024) 302–309 Voloskov et al./ Structural Integrity Procedia 00 (2024) 000–000

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2

1. Introduction

Additive Manufacturing (AM) represents a significant advancement in manufacturing technology, enabling the production of complex geometries and customized components with reduced material waste (Gu et al. 2012). As industries increasingly adopt AM processes, understanding the factors that influence part quality becomes essential. Among these factors, process induced defects play important role. They have an effect on the microstructure and thus on the mechanical properties of the end products. The properties of the final part highly depend on certain process parameters, such as the laser velocity and power density, scanning strategy, hatch distance, and thickness of the printed layers and other parameters. The details are generally printed using a specific set of printing parameters. Such combinations of printing parameters affect the distribution of typical defects in the final part (Grasso and Colosimo 2017), such as a lack of fusion, pores, and microcracks induced by residual stresses (Mishurova et al. 2021). Defects significantly impact fatigue, particularly subsurface defects (Panov et al. 2022) and internal defects (B. Voloskov et al. 2022; B. S. Voloskov et al. 2024). Recent studies have highlighted the significant impact of scanning strategies on the quality of AM parts. For instance, authors (Ali, Ghadbeigi, and Mumtaz 2018) demonstrated that different scanning strategies in laser powder bed fusion (PBF-LB) affect residual stress and mechanical properties, indicating that optimized scanning paths can lead to improved material performance. Also, some researchers (Mao et al. 2024) investigated the effects of hatch spacing on the quality of Inconel 718 alloy parts, revealing that smaller hatch distances can enhance part integrity by reducing porosity and improving mechanical characteristics. This work investigates the effects of different scanning strategies and hatch distances on the porosity and mechanical properties of 316L stainless steel produced by PBF-LB.

2. Materials and Experimental Procedures

2.1. Specimens

All specimens in present study were produced by PBF-LB using the TruPrint 1000 by TRUMPF (Ditzingen, Germany). The laser beam had a Gaussian profile and the diameter of the focal spot was 55 μm. Specimens were printed from Höganäs 316L stainless steel powder obtained by gas atomization process. The scanning parameters are shown in Table 1. The 316L stainless steel powder particles had a spherical shape with a diameter of 20–55 µm. The powder analysis including particle size distribution is reported in previous work (Y. O. Kuzminova, Evlashin, and Belyakov 2024).

Table 1. PBF-LB manufacturing parameters. Laser power (W)

Beam traverse speed (mm/s)

Layer thickness (  m)

Hatch distance (  m)

Scanning parameters Contour parameters

113

700 500

20 20

50/80/110

70

50

Two printing strategies were used: 90° alternating hatch scanning strategy (called No Pattern (NP) in present study) and chessboard scanning strategy. The scheme of the printing strategies is shown in Fig. 1b. The scanning strategy NP is a strategy where the angle between the layers is always changed by 90° angle as it is schematically shown (Fig. 1b). In the case of chessboard scanning strategy, the layer is equally divided by squares. The scanning directions between these squares are always perpendicular to each other. The dimensions of the squares can be different, but in this study, it was a square with a side length equal to 250 µm (Fig. 1b).