PSI - Issue 68

5

Rahul Singh et al. / Procedia Structural Integrity 68 (2025) 715–721 Rahul Singh et.al/ Structural Integrity Procedia 00 (2025) 000–000

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(a)

(b)

Fig 2 : (a) Tensile plot for NP550 specimens (b) Absorbed impact energy during Charpy test conducted at 25 ° C for NP550 sample compared with PE590 sample of Khiratkar et. al(Khiratkar et al., 2019). The tensile test results for the NP550 samples are presented in Error! Reference source not found. (a) and summarized in Error! Not a valid bookmark self-reference. . These results provide a detailed analysis of the material's mechanical properties, including parameters such as tensile strength, yield strength, and elongation at break. The result is compared with the tensile properties of pearlitic steel used in another study (Mishra et al., 2019). The yield strength is similar but we observe a drastic decrease in the tensile strength whereas the elongation at fracture is significantly higher compared to PE590 pearlitic steel.

Table 2: Tensile properties of NP550 specimens and compared with PE590 samples of Khiratkar et al. (2019).

Yield Strength (MPa)

Tensile Strength (MPa)

Elongation at fracture (%)

Specimen

NP550

1431 ± 8

1490 ± 5.3

11.72 ± 0.6

PE590(Mishra et al., 2019)

1482 ± 4

2679 ± 7

8.2 ± 0.8

Impact energy absorbed during the Charpy test is shown in Error! Reference source not found. (b) for NP550 samples. The result is compared with the PE590 samples of Khiratkar et al. (2019). It has been observed that the energy absorbed by NP550 is almost double that of PE590 samples that were tested at 25 ° C. The fracture of the specimens was completely brittle with cleavage-like facets as seen from Fig 3. The size of the cleavage facets was in the range of 18 to 54 µ m, which is similar to the nodule size of the NP550 specimens as seen in Table 1. Garbarz and Pickering (1988) and Zhou et al. (2016) explored the relationship between pearlitic nodule size and the absorption of impact energy, particularly at room temperature (~25 °C). They observed that the cleavage crack is deflected at the boundaries of these nodules. Their findings suggest that smaller pearlite nodules, formed from a finer prior austenite grain size (PAGS), lead to a higher Charpy impact energy at room temperature compared to larger nodules formed from a coarser PAGS. Additionally, Park and Bernstein (1979) and Alexander and Bernstein (1982) used transmission electron microscopy (TEM) to demonstrate that the cleavage planes in pearlite at this temperature correspond to {100} planes in ferrite. The orientation of cementite within a single nodule, which can vary, does not significantly affect the crack path during impact at room temperature.