Stress corrosion cracking cold work

Stress Corrosion Crocking. Stress corrosion cracking occurs from the combined action of corrosion and stress. The corrosion may be initiated by improper chemical cleaning, high dissolved oxygen levels, pH excursions in the boiler water, the presence of free hydroxide, and high levels of chlorides. Stresses are either residual in the metal or caused by thermal excursions. Rapid startup or shutdown can cause or further aggravate stresses. Tube failures occur near stressed areas such as welds, supports, or cold worked areas. 

Nitrogen compounds These also arise from both natural and synthetic sources. Thus ammonia is formed in the atmosphere during electrical storms, but increases in the ammonium ion concentration in rainfall over Europe in recent years are attributed to increased use of artiflcial fertilisers. Ammonium compounds in solution may increase the wettability of a metaland the action of ammonia and its compounds in causing season cracking , a type of stress-corrosion cracking of cold-worked brass, is well documented. 

Stress-corrosion cracking occurs in certain aluminium alloys which have been developed for medium and high strength by employing variations in composition, cold work and heat treatment The main alloys are based upon Al-Mg, Al-Mg and Al-Cu, but stress corrosion also occurs in Al-Ag, Al-Cu-Mg, Al-Mg-Si, Al-Zn and Al-Cu-Mg-Zn alloys. It has... 

In stress corrosion cracking, the material breaks as the result of mechanical stress under the influence of a corrosive medium. Stress corrosion cracking is characterized by the presence of deep intergranular or intercrystalline cracks that are generally not externally evident. It can be caused by inherent stress, which can be due to cold working or arise near a welding seam. 

K scc depends on metallurgical factors (it usually decreases as the strength of the steel increases, even though it also depends on the microstructure of the material, e. g. it is lower in quenched and tempered steel than in cold-worked steels) and on environmental factors (for instance, in alkaline environments and in the absence of chlorides, Kfscc so high that normal mechanical failure takes place before stress corrosion cracks can develop). 

J.I. Dickson, A.J. Russell, D. Tromans, Stress corrosion crack propagation in annealed and cold worked 310 and 316 austenitic stainless steels in boiling (154 °C) aqueous magnesium chloride solution, Can. Metad. Q. 19 (1980) 161-167. 

W.C. Moshier, C.M. Brown, Effect of cold work and processing orientation on stress corrosion cracking behavior of Alloy 600, Corrosion 56 (2000) 307—320. 

D.H. Lee, J.H. Han, K.M. Kim, J.S. Kim, U.C. Lee, Effect of cold work on primary water stress corrosion cracking of Inconel Alloy 600 nuclear power steam generator tube material, Han guk Chaelyo Hakhoechi 8 (1998) 726-732. 

P. Muraleedharan, H.S. Khatak,J.B. Cnanamoorthy, P. Rodriguez, Effect of cold work on stress corrosion cracking behavior of types 304 and 316 stainless steels, MetaU. Trans. A 16A (1985) 285—289. 

J.H. Zheng, W.F. Bogaerts, Effects of cold work on stress corrosion cracking of type 316L stainless steel in hot lithium hydroxide solution, Corrosion 49 (1993) 585—593. 

Z. Lu, T. Shoji, Y. Takeda, Y. Ito, A. Kai, S. Yamazaki, Transient and steady state crack growth kinetics for stress corrosion cracking of a cold worked 316L stainless steel in oxygenated pure water at different temperatures, Corros. Sci. 50 (2008) 561—575. 

The critical potential for stress-corrosion cracking of moderately cold-worked 18-8 stainless steel in deaerated MgCb solution at 130°C is -0.145V (S.H.E.). 

Annealed brass, if not subject to a high applied stress, does not stress-corrosion crack. Whether residual stresses in cold-worked brass are sufficient to cause stress-corrosion cracking in an ammonia atmosphere can be checked by immersing brass in an aqueous solution of 100 g mercurous nitrate [Hg2(N03)2] and 13 mL nitric acid (HNO3, specific gravity 1.42) per liter of water. Mercury is released and penetrates the grain boundaries of the stressed alloy. If cracks do not appear with 15 min, the alloy is probably free of damaging stresses. 

---