A Test Procedure to Evaluate the Relative Susceptibility of Materials to Stress Corrosion Cracking Available to Purchase

A variety of experimental test procedures are being used to determine the susceptibility of high strength materials to stress corrosion cracking (SCC). Much controversy exists over the interpretation of the large scatter in the resultant time to failure data. The experimental test procedure discussed here presents reasons for the discrepancies in test data and provides a semiquantitative approach to SCC testing of high strength materials. The electrochemical potentiostatic testing technique is used to cathodically and anodically polarize notched round bars stressed to 0.9 of their notched tensile strength. Three strength levels of high strength materials are investigated: (1) A-286 and 17-4 PH at the 180- to 220-ksi level; (2) tensilized Inconel 718, H-11, and PH 13-8 Mo at the 220- to 250-ksi level, and (3) H-11, Maraging 300, and MP35N at the 250- to 290-ksi level. The Potentiostatic Stress Corrosion Life Curve (PSCLC) obtained from this procedure provides a technique to predict (1) the relative SCC behavior of high strength materials in aqueous environments, and (2) any accelerated failure times that result from galvanic coupling. The scanning electron microscope (SEM) is used to characterize the SCC failure mode under these various environmental conditions.