1161 Stress Corrosion Cracking

Stress corrosion cracking results in the brittle failure of normally ductile material. SCC is defined as cracking under the combined action of corrosion and a tensile stress where failure would not occur if either stress or environment were applied in isolation (see Fig. 11.11). There are a number of sources of tensile stress including external applied stresses (structural loads) and internal residual stress (from heat treatment or manufacturing processes such as welding or rolling etc.). The phenomenon of SCC was originally termed season cracking. The term came about as a result of the failure of brass ammunition cartridges used in hot, humid (ammoniacal) environments during the late 1800s. Since that time a whole range of metal/environment systems that suffer from SCC have been recognized, a few of which are given in Table 11.4.

Although SCC tends to result from the combination of tensile stress and a specific environment, the susceptibility of a material is very unpredictable because small changes in metal composition, heat treatment, environmental composition, or temperature can drastically alter the SCC behavior of the material. In addition the rate of application of stress/strain also affects the SCC susceptibility of a material.

0 0

Post a comment