senior corrosion engineer, Air Products and Chemicals, Inc., Allentown, Pa.
Pages: 30 Published: Jan 1976
A review of the work done to elucidate the mechanism of stress-corrosion cracking of austenitic stainless steels is presented. The major emphasis is placed on the cracking which occurs in chloride environments, although other environments are mentioned. This paper is intended to update earlier reviews and is concerned mainly with works published in the period 1960–1971.
The various studies on the effects of environmental and metallurgical factors on the kinetics of the cracking process are reviewed in detail. Variables such as temperature, chloride concentration, pH, stress, and metallurgical state are discussed. Also, the various studies on the electrochemistry of the system are reviewed.
The major theories on the mechanism of the cracking process are divided into two groups: The electrochemical theories postulate that the effect of tensile stress is to accelerate the localization of the corrosion process at crack sites. These theories include stress assisted segregation of damaging elements in the steel to the crack region, moving crystal imperfections including dislocations, and slip steps. The hydrogen entry theories, such as the formation of an easily corroded hydride phase or eta martensite formation, also fall into this category. The quasi-mechanical theories involve a mechanical fracture step in addition to corrosion. Tunnel pitting, corrosion produced wedging, and reduction of stress energy required to propagate a crack through chemical adsorption are examples of these theories. Finally, some areas of future work are discussed, and questions which need to be resolved are delineated.
stress corrosion, austenitic stainless steels, crack propagation, nucleation, residual stresses, plastic strain, magnesium chloride
Paper ID: STP28687S