Helium-induced weld cracking in austenitic and martensitic steels
- 93 Downloads
Helium was uniformly implanted into type 316 stainless steel and Sandvik HT-9 (12Cr-1 MoVW) to levels of 0.18 to 256 and 0.3 to 1 a.p.p.m., respectively, using the “tritium trick” technique. Autogenous bead-on-plate, full penetration, welds were then produced under fully constrained conditions using the gas tungsten arc welding (GTAW) process. The control and hydrogen-charged plates of both alloys were sound and free of any weld defects. For the 316 stainless steel, catastrophic intergranular fracture occurred in the heat-affected zone (HAZ) of welds with helium levels ≥2.5 a.p.p.m. In addition to the HAZ cracking, brittle fracture along the centreline of the fusion zone was also observed for the welds containing greater than 100 a.p.p.m. He. For HT-9, intergranular cracking occurred in the HAZ along prior-austenite grain boundaries of welds containing 1 a.p.p.m. He. Electron microscopy observations showed that the cracking in the HAZ originated from the growth and coalescence of grain-boundary helium bubbles and that the fusion-zone cracking resulted from the growth of helium bubbles at dendrite boundaries. The bubble growth kinetics in the HAZ is dominated by stress-induced diffusion of vacancies into bubbles. Results of this study indicate that the use of conventional GTAW techniques to repair irradiation-degraded materials containing even small amounts of helium may be difficult.
KeywordsTritium Brittle Fracture Fusion Zone Intergranular Fracture Bubble Growth
Unable to display preview. Download preview PDF.
- 1.H. S. Rosenbaum, “Treatise on Materials Science and Technology”, Vol. 7 (Academic Press, New York, 1975).Google Scholar
- 5.M. M. Hall Jr, A. G. Hins, J. R. Summers and D. E. Walker, “Weldment: Physical Metallurgy and Failure Phenomena, Proceedings of the Fifth Bolton Landing Conference” (General Electric Co, Schenectady, New York, 1978) p. 365.Google Scholar
- 6.S. D. Atkin, ADIP Semiannual Progress Report (September 1981) p. 110.Google Scholar
- 7.W. R. Kanne, C. L. Angerman and B. J. Eberhard, DP-147,0 (E.I. du Pont de Nemours, Savannah River Laboratory, Aiken, SC, 1987).Google Scholar
- 9.Annual Books and ASTM Standards, “Standard Guide for Simulation of Helium Effects in Irradiated Materials”, Vol. 12.02, E492-83 (American Society for Testing and Materials, Philadelphia, PA) pp. 808–11.Google Scholar
- 11.H. T. Lin, PhD dissertation, Auburn University (1989).Google Scholar
- 20.R. L. Rickett, W. F. White, C. S. Walton and J. C. Butler, Trans. ASM 44 (1952) 138.Google Scholar