PSI - Issue 16

Yaroslav Ivanytskyi et al. / Procedia Structural Integrity 16 (2019) 126–133 Yaroslav Ivanytskyi et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig 6. Distribution of relative concentration of hydrogen (С /C 0 ) at different time : (а) 160 h; (b) 800 h; (c) 1550 h.

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Fig.7. Change of creep deformation (a), deformation energy (b) and damaging parameter (c) for the 0.5Cr-0.5Mo-0.25V steel at Т = 640 °С in time: Solid curves – energy criterion, dashed – classical approach, symbols – experimental data; 1 – in air; 2 – in hydrogen.

Analysis of the data showed that the results of calculations obtained using two different approaches provided satisfactory convergence with experimental data. However, for prediction of the long-term durability using the energy approach, it is enough to have data only for creep to determine three constants. The usage of classical kinetic equations requires the establishment of an additional four coefficients. As a result, curves characterized the kinetics of damage accumulation in the specimen with different hydrogen concentration (Fig. 8) and the effect of hydrogen concentration on time required to fracture (Fig. 9) were obtained. As can be seen from these results that hydrogenation of the sample significantly influenced on its durability. Thus, at hydrogen concentration of 2 ppm, time to fracture was 1248 h, which was by 22% less than the lifetime of the non hydrogenated sample, which was 1601 h. However, a sharp decrease in durability to 674 h, almost by 58%, at increasing hydrogen concentration up to C 0 = 10 ppm was observed.