STP677: Cryogenic Effects on the Fracture Mechanics Parameters of Ferritic Nickel Alloy Steels

    Tobler, RL
    Metallurgist, Metallurgist, and Division Chief, National Measurements Laboratory, Boulder, Colo.

    Mikesell, RP
    Metallurgist, Metallurgist, and Division Chief, National Measurements Laboratory, Boulder, Colo.

    Reed, RP
    Metallurgist, Metallurgist, and Division Chief, National Measurements Laboratory, Boulder, Colo.

    Pages: 21    Published: Jan 1979


    Abstract

    Fracture toughness (KIc, JIc) and fatigue-crack growth (da/dN) datafor quenched and tempered low-carbon ferritic 3.5Ni and 9Ni steels were measured at temperatures between 295 and 4 K. The tests were performed using 25- and 31-mm-thick compact specimens having fracture planes parallel to the rolling direction (TL orientation). The fracture toughness results for both steels showed qualitatively similar trends: at decreasing temperatures below 295 K, JIc increased by about 20 percent prior to the onset of classical ductile-to-brittle transitions involving cleavage. The transitions occurred between 172 and 100 K for 3.5Ni steel, and between 76 and 4 K for 9Ni steel. Transitional behavior also was evident in the fatigue crack growth behavior. The room-temperature fatigue crack growth rates for these nickel steels are typical of ferritic steels, but the rates at subtransition temperatures are accelerated drastically, in association with cleavage and other brittle cracking modes. Data comparisons between the 3.5Ni and 9Ni steels tested here and other nickel alloy steels are included.

    Keywords:

    fatigue (materials), fracture (materials), low temperature tests, mechanical properties, nickel alloys, steels


    Paper ID: STP34908S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP34908S


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