Stress Corrosion Cracking in the Pre-Cracked Specimens of Type 403 stainless Steel

Abstract

Crack growth rate and threshold stress intensity factor for stress corrosion cracking(SCC), KISCC were measured for type 403 stainless steel in 3.5% NaCl solution at room temperature and SCC was monitored by electrochemical noise technique during KISCC testing. In rising load test, pits were formed at the tip of pre-crack for the pre-cracked compact tension specimen unlike in smooth round specimen in which only unstable pits were observed and hence immune to SCC. Micro-cracks were found to initiate from the pits in the former specimen, and initiation of micro-crack as well as macro-crack was detected by electrochemical noise technique in rising load KISCC tests. Crack growth rate increased with increasing either displacement rate or stress intensity factor at crack initiation and was higher in rising load KISCC test compared to constant load KISCC test at given stress intensities. In addition, KISCC value was lower in the former test, indicating the test condition of rising load test was more severe than that of constant load test.