Plateau Velocity of SCC in High Strength Steel — A Quantitative Treatment

Abstract

A hydrogen embrittlement model developed by the author is adapted to stress corrosion cracking (SCC). It leads to an equation describing the characteristic shape of the SCC velocity (v) versus stress intensity (K) curve. The occurrence of a plateau velocity can be explained tentatively as the combined effect of four causes: (1) development of a plastic enclave at the crack tip, (2) blunting of the crack tip due to plasticity and corrosive attack, (3) limited diffusion rate of hydrogen, and (4) a specific relationship between critical hydrogen concentration for failure and stress intensity. An effective crack tip radius (ρe) is introduced to describe the basic susceptibility to SCC. It determines both threshold stress intensity (KISCC) and plateau velocity (vp).