PSI - Issue 36

Ihor Dmytrakh et al. / Procedia Structural Integrity 36 (2022) 298–305 Ihor Dmytrakh et al./ Structural Integrity Procedia 00 (2021) 000 – 000

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3

The hydrogen concentration in bulk of specimens has been determined on the base of the hydrogen discharging process under anodic polarisation using the modified hydrogen electrochemical oxidation method proposed by Capelle et al. (2008) and Capelle et al. (2010). The general view of developed facility for hydrogen charging of specimens and determination of hydrogen concentration is presented in Fig. 1.

Table 1. Chemical composition of NS4 solution (gram/litre). NaHCO 3 KCl CaCl 2 MgCl 2 ∙ H 2 O 0.483 0.120 0.137 0.131

Fig. 1. The general view of developed facility for hydrogen charging of specimens and determination of hydrogen concentration: 1 – dynamic electrochemical laboratory VoltaLab40; 2 – electrochemical cell; 3 – oxygen meter; 4 – high pressure gas cylinder (argon); 5 – gas pressure regulator; 6 – low pressure gas cylinder (argon); 7 – argon-admission valve; 8 – water-lock. As the preliminary stage of the study the experimental dependence “hydrogen concentration C H in specimen – time of exposure τ ” was received. Following to work of Capelle et al. (2008), these experimental data were described by power relation:

6 m 10   −

0 128 .

C

  A

[wppm] ,

(1)

=

H

where A and m are some constants that depend on the system “material – environment” and testing conditions; τ is the time of exposure given in hours. For our case, the values of these constants are: 0 28 . A = and 0 65 . m = . This analytic relation served as the reference curve under hydrogen charging of the specimens for the tensile test to the assigned level of С H  0.23 wppm.

0 = 

f   =

d=5mm

t=3mm

t=3mm

d=5mm

SEM observation area

Fig. 2. The scheme of cutting of the special disk-like mini samples for SEM observations from the cylindrical tensile specimens.