Crack Initiation in CERT Tests on Type 304 Stainless Steel in Pure Water

Crack initiation has been determined for Type 304 stainless steel in constant extension rate stress corrosion cracking tests. Tests have been conducted at 125, 200, and 288 C in pure water environments containing 1.8,0.2, and 0.2 ppm of dissolved oxygen, respectively. In addition to the temperature/oxygen variable, the influence of surface condition (shot peened and wet ground) and sensitization heat treatment (600 C/24 hours and welded plus 500 C/24 hours or 400 C/ 10 days) has been examined. At 288 C, crack initiation in strongly sensitized specimens occurs at less than 20% of life. At lower temperature and/or less degree of sensitization, crack initiation occurs later in life. Shot peening reduces the strain to initiation, particularly at 125 C where there is a marked contrast to the wet ground condition. In general, variations in strain to initiation may not be strongly reflected in strain to failure. The limited results of other investigations were found to support the findings of this study.