STP942: Influence of Nitrogen Solutes and Precipitates on Low Cycle Fatigue of 316L Stainless Steels

    S, Degallaix
    Université de Lille, Villeneuve d'Ascq Cedex,

    G, Degallaix
    Université de Lille, Villeneuve d'Ascq Cedex,

    Institut Industriel du Nord, Villeneuve d'Ascq Cedex,

    J, Foct
    Université de Lille, Villeneuve d'Ascq Cedex,

    Pages: 14    Published: Jan 1988


    Abstract

    Improvement of monotonic and cyclic mechanical properties of 316 steels by nitrogen is studied for different nitrogen contents between 0.03 and 0.25 wt% at 20 and 600°C. At 20°C, yield and ultimate tensile stress increase almost linearly with nitrogen content to the detriment of ductility. Low-cycle fatigue (LCF) life also increases linearly with nitrogen solutes until 0.12 wt% nitrogen where a saturation of this effect occurs. This improvement is attributed to a more homogeneous distribution and to a better reversibility of plastic strain.

    The influence of aging treatment at 600°C is studied on tensile and LCF properties at 20 and 600°C. An LCF life decrease with aging is more noticeable when nitrogen content is high. Furthermore, the higher the strain range, the more marked is the decrease in life at room temperature; this tendency is inverted at 600°C.

    At 20°C, stress evolution during the hardening-softening stage is virtually independent of aging time but strongly dependent on nitrogen content. For high strain ranges at 600°C and high nitrogen content, the stress increases continuously until rupture, due to significant intergranular precipitation and embrittlement.

    Keywords:

    austenitic stainless steels, nitrogen steels, low-cycle fatigue, aging, high temperature


    Paper ID: STP24522S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP24522S


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