STP782: Optimization of Precipitation Hardened Fe-Ni-Cr Alloys Using Nickel Ion Bombardment Simulation Studies

    Bajaj, R
    Senior engineer, fellow engineer, and manager, Westinghouse Advanced Reactors Division, Madison, PA.

    Diamond, S
    Senior engineer, fellow engineer, and manager, Westinghouse Advanced Reactors Division, Madison, PA.

    Bleiberg, ML
    Senior engineer, fellow engineer, and manager, Westinghouse Advanced Reactors Division, Madison, PA.

    Pages: 29    Published: Jan 1982


    Abstract

    Two precipitation hardened Fe-Ni-Cr alloys were irradiated with nickel ions to simulate neutron irradiation and evaluate the in-reactor swelling and phase stability of these materials. Based upon the results of these tests, minor chemical adjustments were made to the base chemistry which will improve in-reactor phase stability and swelling resistance.

    The alloys were preinjected with 5 appm He and Ni-ion irradiated in an aged condition to a maximum dose of ∼250 dpa at temperatures between 500°C and 750°C. Surface profilometry measurements on sheet samples showed a small swelling peak at 550°C for one alloy and at 500°C for the other. Very low swelling (less than 1%) was measured by TEM in both alloys irradiated in disc form at 550°C to a dose of ∼220 dpa. The steady-state swelling rates at the peak temperatures were 0.015%/dpa with incubation doses of 145 dpa.

    The pre-existing spherical γ' precipitates in the alloys assumed irregular shapes under Ni-ion bombardment and their size distribution broadened without significant change in the average size (∼12 nm) or volume fraction (1–2%).

    Substantial radiation-induced precipitation (other than γ') was observed in both alloys. Dark field microscopy and electron diffraction analysis were used to identify the precipitates. It was established that a deleterious G-phase precipitation could be eliminated by reducing the silicon content from 1.0% to 0.1%, without affecting the swelling resistance of the alloys. A reduction in the Mo content was also recommended based on phase stability considerations.

    Keywords:

    Ni-ion irradiation, simulation, ion bombardment, Fe-Ni-Cr alloys, swelling, liquid metal fast breeder reactor, TEM, ion implantation, incubation dose, γ' precipitates, phase stability, electron diffraction, G-phase, alloy optimization, voids


    Paper ID: STP34384S

    Committee/Subcommittee: E10.07

    DOI: 10.1520/STP34384S


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