Effects of Ferrite and Sensitization on Intergranular and Stress-Corrosion Behavior of Cast Stainless Steels

    Published: Jan 1976

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    Cast stainless steels of the CF grades (19Cr, 9Ni), which find widespread application in the chemical, petrochemical, and power generating industry, were subjected to intergranular corrosion tests (Huey) and stress-corrosion tests (vapor phase of aqueous 875-ppm sodium chloride (NaCl) solution at 477 K [400°F]) to evaluate the effect of ferrite in the range of 0 to 40 ferrite numbers, in the solution-annealed and in the sensitized condition.

    The intergranular corrosion tests demonstrated beneficial effects of ferrite for all the alloys tested in the solution-annealed condition and for the molybdenum-free cast steel grades in the sensitized condition. Ferrite increased the sensitization effects on intergranular corrosion for the molybdenum-bearing grades. Highest corrosion rates in Huey tests, based upon weight loss measurements, do not necessarily mean deepest intergranular attack. Intergranular attack was found to terminate at ferrite-austenite grain boundaries. The intergranular corrosion test results would indicate that ferrite numbers exceeding 10 offer greater operating safety for cast, corrosion resistant grades, CF-3, CF-3M, CF-8, and CF-8M in the solution-annealed condition and also, in the event of sensitization, for cast corrosion-resistant grades CF-3 and CF-8.

    Significantly increased resistance to stress-corrosion cracking with increasing ferrite content was observed for cast steels in the solution-annealed and in the sensitized condition. These stress-corrosion cracking tests would indicate that ferrite numbers of 10 or more offer greater operating safety for cast corrosion-resistant CF grades in the solution-annealed as well as in the sensitized condition.


    stress corrosion, cracking (fracturing), castings, stainless steels, corrosion tests, ferrite, sensitizing

    Author Information:

    Beck, FH
    Professor, Ohio State University, Columbus, Ohio

    Juppenlatz, J
    Chief metallurgist, Quaker Alloy Casting Company, Myerstown, Pa.

    Wieser, PF
    Research director, Steel Founders' Society of America, Rocky River, Ohio

    Paper ID: STP28691S

    Committee/Subcommittee: G01.06

    DOI: 10.1520/STP28691S

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