PSI - Issue 68

Yasith H. Rajashilpage et al. / Procedia Structural Integrity 68 (2025) 981–987 Y.H. Rajashilpage, R.A. Yildiz, M. Malekan / Structural Integrity Procedia 00 (2025) 000–000

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indenter and a 100 kg major load. For each specimen, hardness tests were performed over six different points and the average value was recorded to ensure reliability and minimize variability across individual tests. These measurements facilitated a detailed comparison of how different manufacturing parameters influenced the mechanical properties of SS 316L and IN625. Annealing heat treatment cycles were tailored to each material's chemical composition (shown in Table 1) with consistent soaking times. Heat treatments were conducted using a Nabertherm™ LH 15/12 Chamber Furnace.

Fig. 1. (a) Inside view of the furnace with the sample holder box, and (b) Annealing heat treatment cycle for each temperature. Table 1. Chemical weight composition of SS 316L and IN625 alloys. Fe Cr Ni Mo Mn Co C N Other Si O F P Cb+Ta Nb Ti Al Cu SS 316L Balance 17.11 12.51 2.53 1.20 0.01 0.005 0.01 <0.10 0.53 0.03 0.005 0.003 0 0 0 0 0 IN625 4.38 21.47 Balance 8.88 0.04 0.08 0.02 0.01 <0.10 0 0 0 0 3.65 3.64 0.15 0.07 0.03

3. Results and discussion 3.1. Tensile test

The tensile test results, as presented in Fig. 2 for both alloys under different process parameters, showed a decrease in elongation (ductility) after heat treatment compared to the as-built specimens, while the ultimate tensile strength (UTS) increased. However, with higher annealing temperatures, elongation was significantly restored, reaching up to 95% in SS 316L and 78% in IN625 for specimens with 30 µm layer thickness and 1400 mm/s scanning speed. This suggests that while post-heat treatment initially reduced ductility, optimizing the annealing temperature could nearly restore the material original elongation. This trend was consistent in both SS 316L and IN625. Additionally, variations in printing parameters also influenced mechanical properties including elastic modulus (E), UTS, and elongation at break ( ! ).

Fig. 2. Tensile test results of specimens with different: (a) Scanning speeds with same 55µm layer thickness and 700°C heat treatment, (b) Heat treated temperatures with same 55µm layer thickness and 1700mm/s scanning speed, and (c) Layer thicknesses with the same 1700mm/s scanning speed and 700°C heat treatment.