Stress corrosion cracking behaviour of precipitation hardened stainless steels in high purity water environments

The susceptibility of 17-4PH and 17-7PH stainless steels to stress corrosion cracking (SCC) is examined in the present investigation. The specimens were tested in the presence of NaCl and NaOH (20%) at 90 degreesC and various pH values. The evaluations were carried out using the CERT test, at a speed of 10(-6)s(-1) supplemented by anodic polarisation and electrochemical noise analysis. The main objective was to identify the conditions of both susceptibility and performance of these materials. Fractographic analyses revealed both ductile and brittle fractures. Also, the presence of intergranular cracks was a clear indication of a characteristic anodic dissolution of the material. Nevertheless, the main mechanism for stress corrosion crack propagation was hydrogen embrittlement. From the experimental results, it was concluded that electrochemical noise analysis is a reliable technique for the identification of crack nucleation and growth.