PSI - Issue 75

Nina Grözinger et al. / Procedia Structural Integrity 75 (2025) 642–649 Author name / Structural Integrity Procedia (2025)

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1. Introduction The aim of this work was to get quantitative statements on the cyclic material behavior of austenitic stainless steel and weld materials in HTW compared to an air environment. A HTW environment leads to corrosion and thus to environment assisted cracking (Dong et al. 2017), (Wang et al. 2023), (Wang et al. 2021). This is relevant for lots of technical applications, where components get in contact with water, like in piping systems or pressure vessels. It is important to know how much their service life is reduced due to the influence of the HTW. Because many of these components contain weld seams, it is also of great interest to investigate weld materials. Two materials were chosen for the tests: AISI 321 and ER 308L. Both of them are often used in nuclear power plants (Dong et al. 2017), (Emerson et al. 2024), (IAEA 1999). Controlling the strain inside an autoclave is challenging. Different approaches are known from literature. Some use non-contact measurements like digital image correlation (DIC) (Myhre et al. 2023). The issue with this kind of control is, that it does not correspond to the recommendations of ASTM E606 (Blug et al. 2019). Another possibility is to use hollow specimens, where the medium is inside the specimens and no autoclave is needed. A control from outside of the autoclave is also possible. However, this means, that the relation between the specimen heads and the gauge section has to be found. One approach for this is described in (Simonovski et al. 2021), where the ratio between shoulder and gauge section is calculated by using constitutive laws.

2. Materials and methods 2.1. Materials and specimens

From a former project, specimens were available. The chemical composition of the specimens out of the two materials AISI 321 and ER 308L was analyzed and the results can be seen in Table 1. AISI 321 is an austenitic chromium-nickel steel with addition of titanium for stabilization. ER 308L is a typical material for welding stainless steels, especially in apparatus and tank construction. Round specimens with cylinder heads are used for the fatigue testing, see Fig. 1. The test cross-section is 10 mm in diameter, the length of the test section is 20 mm.

Table 1. Chemical composition of the materials in wt.%

C

Si

Mn

P

S

Cr

Mo

Ni

Al

Co

Cu

Nb

Ti

N

AISI 321 ER 308L

0.031 0.031

0.48 0.48

1.501 1.502

0.031 0.026 17.32 0.031 0.025 17.40

0.290 9.45

0.029 0.190 0.326 0.008 0.104 0.030

0.300 9.520 0.027 0.183 0.327 -

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Fig. 1. Geometry of round fatigue specimens with cylinder heads