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Vol.42, No.1, 37 ~ 43, 2004
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| Title |
| Delayed Hydride Cracking Velocity of Zr-2.5Nb Tubes with Yield Strength |
| 김영석 Kim Yeong Seog , 최승준 Choe Seung Jun , 정용무 Jeong Yong Mu , 김인섭 Kim In Seob , 마르켈로프 Vladimir Markelov |
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| Abstract |
| The objective of this study is to investigate delayed hydride cracking velocity (DHCV) of Zr-2.5Nb pressure tubes with yield strength. DHC tests were conducted at an initial K_(I) of 15 to 19 MPa √m and 250℃ on the compact tension specimens containing up to 100 ppm hydrogen that were taken from the Zr-2.5Nb tubes with different yield strengths. The crack growth was determined with the direct current potential drop method. A nice correlation of the DHC velocity and the yield strength was obtained at all temperatures by normalizing the DHCV with the terminal solid solubility and diffusion of hydrogen: the DHCV increased exponentially with increased yield strength of the Zr- 2.5Nb tubes. In contrast, the texture and the distribution of the β-Zr phase were found to have a comparatively minor effect on the DHCV of the Zr-2.5Nb tubes. Yield strength of the Zr-2.5Nb tubes determines a plastic zone size with a steep gradient of hydrogen concentration ahead of the crack tip where hydrides can be precipitated. The yield strength effect is analyzed by correlating the plastic zone and the striation spacing observed on the fractured surfaces as a function of the yield strength. |
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| Key Words |
| Zr-2.5Nb, DHC Velocity, Yield strength, Texture, β-Zr, Striation spacing |
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