ABSTRACT
The phenomena of crack initiation and subcritical propagation in structural materials due to the conjoint actions of stress, material microstructure, and environment have been recognized for many years, and the dependencies and mechanisms have been extensively researched. This is especially the case for alloys in relatively low-temperature (<150°C) environments containing high anionic concentrations of, for instance, chlorides, phosphates,
CONTENTS
18.1 Introduction ........................................................................................................................777 18.2 Problem and the Proposed Solution ............................................................................... 778
18.2.1 Approaches to Life Prediction ............................................................................. 782 18.3 Life Prediction Based on Empirical Correlations .......................................................... 784 18.4 Life Prediction Based on an Understanding of the Mechanism of Cracking ........... 787
18.4.1 Slip-Oxidation Mechanism .................................................................................. 789 18.4.2 Film-Induced Cleavage Mechanism ................................................................... 791 18.4.3 Hydrogen Embrittlement Mechanisms .............................................................. 792
18.5 Prediction Methodology for Ductile Structural Alloys in BWR Systems ................. 794 18.5.1 Rationale for Choice of Slip-Oxidation Model as “Working Hypothesis”
for Crack Propagation of Ductile Alloys in BWR Systems .............................. 795 18.5.2 DeŽnition of Crack Tip Alloy/Environment System ........................................ 795 18.5.3 Evaluation of Reaction Rates at Crack Tip.......................................................... 797 18.5.4 DeŽnition of Crack Tip Strain Rate ..................................................................... 798 18.5.5 Prediction of Stress Corrosion Crack Propagation of Unirradiated
Stainless Steel in 288°C Water .............................................................................. 801 18.5.6 Prediction of Cracking in Unirradiated Welded Plant Components .............807 18.5.7 Irradiation Effects on Stress Corrosion Cracking of Stainless Steels ............. 811
18.6 Conclusions ......................................................................................................................... 817 References ..................................................................................................................................... 819
hydroxides, etc.; such concentrations may be either in the bulk environment (e.g., paper mills, chemical plant, petrochemical, marine) or in localized environments where a high anionic activity may be created due to crevice or liquid-/gas-phase distribution effects on heat transfer surfaces. The mechanisms of such cracking in concentrated environments have been reviewed by, for example, Newman [1].
