STP756: Intergranular Stress-Corrosion Cracking Resistance of Austenitic Stainless Steel Castings

    Hughes, NR
    Senior metallurgical engineer and principal metallurgical engineer, Plant Component Behavior Analysis, General Electric Co., San Jose, Calif.

    Clarke, WL
    Principal metallurgical engineer, Vallecitos Nuclear Center, General Electric Co., Pleasanton, Calif.

    Delwiche, DE
    Senior metallurgical engineer and principal metallurgical engineer, Plant Component Behavior Analysis, General Electric Co., San Jose, Calif.

    Pages: 22    Published: Jan 1982


    Abstract

    This paper evaluates the resistance to intergranular stress-corrosion cracking (IGSCC) in the boiling water reactor of several grades and compositions of austenitic stainless steel castings. A specific objective of this work was to predict the performance of Alloy Casting Institute CF3, CF3A, and CF8 castings in nuclear applications. Full-size welded pipe tests were performed on 10.16-cm-diameter (4 in.) centrifugal castings and small-specimen tests were performed on isothermally treated static and centrifugal castings. The environment for both series of tests consisted of oxygenated high-purity water at 288°C (550 ± 10°F). Axial loads were applied to the full-size pipes in a trapezoidal time-load wave shape with the peak stress exceeding the 288°C (550°F) yield strength of the material tested. For the small-specimen tests, either a constant-extension-rate test technique, a constant-load test technique, or a variable-load test technique was utilized. Both the pipe test and small-specimen tests consistently produce IGSCC in susceptible material such as sensitized AISI-304 stainless steel. Test results clearly indicate the influence of carbon content and δ-ferrite in determining IGSCC susceptibility of austenitic stainless steel castings in the aforementioned environment. Both low carbon content and the presence of critical quantities of ferrite in CF3, CF3A, and CF8 cast material are shown to promote high resistance to IGSCC. In contrast, AISI-304 with essentially zero ferrite (comparable carbon content to CF8) fails by IGSCC when tested similarly.

    Keywords:

    castings, intergranular, stress-corrosion cracking, ferrite content, ferrite distribution, boiling water reactor


    Paper ID: STP28434S

    Committee/Subcommittee: A01.18

    DOI: 10.1520/STP28434S


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