PSI - Issue 68

Birhan Sefer et al. / Procedia Structural Integrity 68 (2025) 1121–1128 Author name / Structural Integrity Procedia 00 (2025) 000–000

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Table 2. SSRT test results of hot rolled and AM Hastelloy Ni-base alloy using hollow specimens.

Condition

Temp

Rp0.2 h

Rp0.2 h

Rp0.2 h

Rm h

Rm h

Rm h

A h

A h

A h

H 2 (MPa) 387 +3.3 244 +7.8 630 +7.9 254 +2.2

Ar (MPa) Rel. (%)

H 2 (MPa) Ar (MPa) Rel. (%)

H 2 (%)

Ar (%)

Rel. (%)

Hot rolled Hot rolled

RT

390 +2.0 228 +0.0 624 +14 286 +3.0

99

823 +1.4 275 +0.8 825 +2.6 277 +3.9

835 +3.5 254 +0.5 820 +12 286 +4.5

99

46.4 +1.2 80.8 +4.0 31.1 +0.0 9.6 +0.3

48.7 +0.4 73.0 +0.9 33.1 +0.5 10.1 +0.6

95

800 ⁰ C

107 101

109 101

111

AM AM

RT

94 97

800 ⁰ C

96

97

Typical SEM-micrographs of the fracture surfaces from the hollow specimens SSRT tested for both materials at both temperatures in H 2 and Ar environment are shown in Figure 3 to Figure 6. For all tests a ductile mode of failure was prevailing and was characterised with dimples of various size. However, in some small areas close to the inner hole surface for the SSRT specimens in both conditions, hot rolled or AM, tested with H 2 a quasi-cleavage fracture features were also possible to identify (see Figure 3b and Figure 5b).These small quasi-cleavage regions on the fracture surface were surrounded with dimples indicating a mixed of ductile and brittle type of fracture behaviour in H 2 environment for both materials when tested at room temperature.

Figure 3. SEM-images showing the typical appearance of the fracture surface of hot rolled Hastelloy SSRT specimens tested at room temperature with a) argon and b) hydrogen gas

Figure 4.SEM-images showing the typical appearance of the fracture surface of hot rolled Hastelloy SSRT specimens tested at 800°C with a) argon and b) hydrogen gas.