January 1, 2002
Conference Paper

Grain Boundary Character Along Intergranular Stress Corrosion Crack Paths in Austenitic Stainless Alloys Removed from High-Temperature Water Service

Abstract

Stress-corrosion cracks produced in high-temperature water environments were examined in alloy 600 and stainless steel samples. The alloy 600 samples were removed from pressurized-water reactor (PWR) steam generator tubing after exhibiting cracking in service or after model-boiler stress corrosion cracking tests. The 304 and 316 stainless steel samples also experienced intergranular stress corrosion cracking (IGSCC) in high-temperature-water environments similar to a PWR steam generator. Grain boundary misorientations were measured along IG crack paths as well as in the bulk. In general, only twin Sigma 3 boundaries exhibited improved resistance to crack propagation. If the Sigma 3 were factored out, the fractions of grain boundary types of cracked boundaries corresponded to their frequency of occurrence in the bulk alloy. Other boundaries with coincident site lattice misorientations, including Sigma 9 and Sigma 27, were observed to crack. The cracks were often (but not always) arrested at grain boundary junctions containing Sigma 3 boundaries. The results obtained indicate that grain boundary crystallography does not fully determine its susceptibility to IGSCC in typical commercial alloys. Other factors must be taken into account when assessing material?s propensity to IG failure.

Revised: April 27, 2007 | Published: January 1, 2002

Citation

Gertsman V.Y., and S.M. Bruemmer. 2002. Grain Boundary Character Along Intergranular Stress Corrosion Crack Paths in Austenitic Stainless Alloys Removed from High-Temperature Water Service. In Proceedings of the Tenth International Conference on Environmental Degradation of Materials in Nuclear Power Systems-Water Reactors, August 5-9, 2001, Lake Tahoe, Nevada, paper no. 55, 8 pages. Houston, Texas:Nace International. PNNL-SA-34786.