Correlation of the Surface Layer Stress Coefficient and Stress Corrosion Cracking — Part 1

The time to failure, the crack propagation velocity, and the surface layer stress of titanium (6Al-4V) and a 4130 steel were measured as a function of applied potential and concentration in solutions of HCl-CH3OH and NaCl. Compact tension specimens were used in the SCC tests. It is shown that a direct correlation, independent of the applied potential or solution concentration, exists between the surface layer stress and SCC. The data show that the resistance to stress corrosion cracking (SCC) decreases under conditions that enhance the strength of the surface layer. It appears that SCC occurs when the environmental conditions raise the surface layer stress coefficient above a critical value.