Abstract
In this study, fracture toughness with the base metal of 9% Ni steel, a cryogenic steel, was evaluated under conditions without hydrogen charging (WO-H) and with hydrogen charging (W-H). Hydrogen charging was performed using an electrochemical cathodic charging method in a electrolyte of 3% NaCl + 0.3% NH4SCN at 19℃ with a current density of 50 A/m². Fracture toughness was assessed at -80℃, -100℃, -130℃, and -160℃ using CTOD (Crack Tip Opening Displacement) tests. The results for WO-H indicated a decrease in fracture toughness values with decreasing temperature, while the results for W-H showed an increase in fracture toughness values as the temperature decreased. In addition, the fracture surfaces and fracture toughness of WO-H and W-H became increasingly similar as the temperature decreased, as observed through scanning electron microscopy (SEM). At -80℃, there was a significant difference in fracture toughness between the WO-H and W-H conditions. WO-H was influenced only by the low temperature, whereas W-H was affected by both low temperature and hydrogen, showing combined effects that led to a decrease in fracture toughness due to hydrogen embrittlement. However, at -160℃, the fracture toughness values for both WO-H and W-H conditions were nearly identical. This suggests that the temperature effect on fracture toughness reduction is greater than hydrogen embrittlement at very low temperatures.
Funder
Ministry of Education
National Research Foundation of Korea
Publisher
The Korean Welding and Joining Society