Stress corrosion cracking characteristics

H.C. Choe, Stress corrosion cracking characteristics of shot-peened stainless steel containing Ti, Han guk Pyomyon Konghak Hoechi 37 (2004) 350-359. 

Few, if any, failure mechanisms have received as much attention as stress-corrosion cracking (SCC). Yet despite an enormous research effort over many years, an acceptable, generalized theory that satisfactorily explains all elements of the phenomenon has not been produced. SCC is a complex failure mechanism. Nevertheless, its basic characteristics are well known, and a wealth of practical experience permits at least a moderately comfortable working knowledge of the phenomenon. 

Electrochemical noise A variety of related techniques are now available to monitor localized corrosion. No external polarization of the corroding metal is required, but the electrical noise on the corrosion potential of the metal is monitored and analyzed. Signatures characteristic of pit initiation, crevice corrosion and some forms of stress corrosion cracking is obtained. 

However, whilst the effects of change in alloy composition upon stress-corrosion cracking susceptibility in the present context may be partly due to their effect upon stacking-fault energy, this does not constitute a complete explanation, since alloying may have significant effects upon electrochemical parameters. The effect of the zinc content of brasses upon their filming characteristics has already been mentioned, while in more recent... 

New alloys with improved corrosion-resistance characteristics are continually being marketed, and are aimed at solving a particular problem, e.g. improved stress-corrosion cracking resistance in the case of stainless steels improved pitting resistance or less susceptibility to welding difficulties. 

A. Parthasarathi and N.W. Polan, Stress Corrosion Cracking of Copper Alloys The Effects of Corrosion Potential and Tarnishing Characteristics, Corrosion, Vol 43, 1987, p 747-755... 

For each aTToy, experiments Have been done in which specimens were exposed unstressed, to solutions that can cause cracking, under a variety of conditions. If broken in air immediately after removal from the solution, specimens exhibited a low value of Zf and fracture surfaces characteristic of stress corrosion cracking. If lapse of time occurs between removal from solution and stressing, specimens exhibited increased values of Sf and decreased amounts of stress corrosion-type fracture with increasing length of lapse of time. This behavior is characteristic of hydrogen embrittlement fracture and has been interpreted as such for the four types of alloys described. These are simple but very clear experiments. 

Definition and Characteristics of Stress Corrosion Cracking Testing Methods... 

In addition to the known corrosive effects of alkali-metal hydroxide and nitrate solutions, intergranular stress corrosion cracking in unalloyed and low-alloy steels in contact with ammonium carbonate and crude methanol (methanol with low concentration of impurities) has also been observed (Matsukura and Sato 1977 Wendler-Kalsch 1983). When this group of materials comes into contact with various othCT aggressive substances, stress corrosion cracking occurs, primarily with transgranular characteristics. 

Material and structural issues to be addressed are primarily related to the potential for corrosion and stress corrosion cracking under irradiation at the high temperatures and pressures associated with the SCWR. Materials for cladding and structural components must be identified and tested to demonstrate their performance in thermal and fast-spectrum reactors. Radiolysis and water chemistry at supercritical conditions must be investigated to understand the effect on reactor materials. Specific material properties to be investigated include dimensional and microstructure stability, and strength, embrittlement, and creep resistance characteristics of the materials. 

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