High-strength steels cracking

Fig. 1.45 Breakdown of oxide film leading to a pit and crack when a high-strength steel is subjected to a tensile stress in a chloride solution (after Brown )...

The 18% Ni maraging steels do not display passivity and normally undergo uniform surface attack in the common environments. Of more serious consequence, however, for all high strength steels, is the degree of susceptibility to stress corrosion cracking (s.c.c.). 

There has been some controversy as to whether s.c.c. occurs by active path corrosion or by hydrogen embrittlement. Lack of space does not permit a full treatment of this subject here. References 14 and 15 are recent reviews on the s.c.c. of high strength steels and deal with the mechanism of cracking (see also Section 8.4). It is appropriate to discuss briefly some of the latest work which appears to provide pertinent information on the cracking mechanism. It should be noted, however, that cracking in all alloy systems may not be by the same mechanism, and that evidence from one alloy system need not constitute valid support for the same cracking mechanism in another. 

Table 3.30 Crack propagation rates for a number of high strength steels ...

Sandoz, G., In Stress Corrosion Cracking in High Strength Steels and in Titanium and Aluminium Alloys, Ed. B.F. Brown, Naval Research Laboratory, Washington, pp. 79-145, (1972)... 

Wei, R. P. and Landes, J. D., Correlation between sustained-load and fatigue crack growth in high strength steels . Materials Research and Standards, 9, 25-27, 44, 46 (1969)... 

Finally, it is necessary to point out that although a particular method of corrosion control may be quite effective for the structure under consideration it can introduce unforeseen corrosion hazards elsewhere. Perhaps the best example is provided by cathodic protection in which stray currents (interaction) result in the corrosion of an adjacent unprotected structure or of steel-reinforcement bars embedded in concrete a further hazard is when the cathodically protected steel is fastened with high-strength steel bolts, since cathodic protection of the tatter could result in hydrogen absorption and hydrogen cracking. 

M.J. Blackburn, W.H. Smyrl, J.A. Feeney and B.F. Brown (eds.), Stress-Corrosion Cracking on High Strength Steel and in Titanium and Aluminum Alloys, Naval Research Laboratory, Washington, DC, 1972, pp. 245-363. 

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