Abstract
Stress-corrosion tests have been performed in sodium chloride at 300° on commercially produced and laboratory-made nickel alloysand austenitic steels. It has been found that resistance to transgranular stress corrosion cracking depends upon the (Ni + Cr) content. Commercial high-Ni alloys are resistant, as are relatively pure Ni–Cr–Fe alloys with (Ni + Cr) ≥ 50% wt. The resistance of alloys with approximately 20% Cr and 20—40% Ni is markedly influenced by other alloying elements, for example, silicon and molybdenum.
Electron microscope studies indicate that resistance to cracking can be approximately correlated with the extent to which dislocation ‘tangling’ occurs at a particular deformation. Planar dislocation arrays appear to be a necessary, though not sufficient, condition for susceptibility. It is thought that the observed dislocation arrangements can be understood without recourse to hypotheses of ordering in these alloys. The influence of some alloying elements, e.g. chromium and silicon, cannot be interpreted simply in terms of their influenceon dislocation arrangements. The favourable effectof these elementson resistance to stress-corrosion cracking is probably associated withtheir ability to increase the protective properties of surface oxide films and thus to inhibit the crack initiation process.
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