Mixed-mode hydrogen-assisted cracking of high-strength steel: the role of cyclic load history
- PDF / 578,737 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 12 Downloads / 186 Views
The authors are very grateful to Dr. J. Kinder, BAM, for providing the investigated material. This work was supported financially by Volkswagen-Stiftung (Az. I/69 362). REFERENCES
(a)
´ 1 H.-A. Kuhn, H. Biermann, T. Ungar, and H. Mughrabi: Acta Metall. Mater., 1991, vol. 39, pp. 2783-94. 2 H. Biermann, B. von Grossmann, T. Schneider, H. Feng, and H. Mughrabi: Proc. 8th Int. Symp. on Superalloys (Superalloys 1996), R.D. Kissinger, D.J. Deye, D.L. Anton, A.D. Cetel, M.V. Nathal, T.M. Pollock, and D.A. Woodford, eds., TMS, Warrendale, PA, 1996, pp. 201-10. 3 A. Royer and P. Bastie: Scripta Mater., 1997, vol. 36, pp. 1151-59. 4 M. Wilkens and K. Eckert: Z. Naturf., 1964, vol. 19a, pp. 459-70.
Mixed-Mode Hydrogen-Assisted Cracking of High-Strength Steel: the Role of Cyclic Load History J. TORIBIO, E. OVEJERO, and V. KHARIN
(b) Fig. 2—X-ray peak profiles (normalized intensity vs lattice parameter) of a sample of the nickel-base superalloy CMSX-6 creep deformed at a temperature of 1253 K under a stress of 230 MPa measured in transmission: (a) (002) peak profile and (b) (200) peak profile.
Fig. 3—Comparison of the lattice misfit d in the directions [001] and [100] of creep-deformed samples of the nickel-base superalloy CMSX-6 determined by transmission X-ray diffraction on TEM specimens (filled symbols) and regular Bragg reflection on bulk samples (open symbols), plotted vs the deformation stress s. 1882—VOLUME 30A, JULY 1999
Prestressing steel wires are manufactured from a hotrolled bar, which is heavily cold drawn to produce a highly resistant material. This manufacturing process generates very intense plastic deformations in the material and causes severe changes in its pearlitic microstructure,[1,2] thus leading to anisotropic stress corrosion behavior in the form of environmentally assisted longitudinal splitting and, thus, mixedmode stress corrosion cracking.[3,4] This work describes experimental evidence of mixedmode hydrogen-assisted cracking of high-strength steel and discusses the role of cyclic load history, because fatigue precracking is a fundamental technique of crack generation for posterior stress corrosion testing, and it has been reported that fatigue preloading may substantially alter the results from stress corrosion cracking tests, especially in the case of hydrogen-assisted cracking (cf. References 5 and 6). The material used is a cold-drawn prestressing steel wire, whose chemical composition and mechanical properties are given in Tables I and II. Metallographic techniques[7,8] were used to reveal the fine pearlitic microstructure of the steel. Figure 1 shows a micrograph of the longitudinal section. The pearlite lamellae are seen to be markedly oriented in a direction parallel or quasi-parallel to the wire axis or colddrawing direction. Slow strain rate tests were performed on transversely precracked rods immersed in aqueous environment. Specimens J. TORIBIO, Full Professor of Materials Science and Engineering and Head, and V. KHARIN, Visiting Scientist, are with the Department of ˜ ˜ Materials
Data Loading...
