Effect of Silicon Content on the Corrosion Resistance and Radiation-Induced Embrittlement of Materials for Advanced Heavy Liquid Metal Nuclear Systems: Quarterly Progress Report (November 2004 – January 2005)

Abstract

This proposal is intended to study the effect of Si content not only on the corrosion resistance but also on the radiation-induced embrittlement of martensitic stainless steels. The susceptibility of these alloys with different Si content to stress corrosion cracking, general corrosion and localized corrosion will be evaluated in the molten LBE and aqueous environments of different pH values using state-of-the-art testing techniques. Testing in the aqueous media is intended to develop baseline data for comparison purpose. Radiation-induced embrittlement of these alloys will initially be studied by irradiating the test specimens with bremmstrahlung gamma radiation from 20-40 MeV electron beams at ISU. These gammas induce (γ, n) reactions in the giant dipole energy region. The principal radiation damage from these irradiations, in turn, stems from the recoiling residual nucleus (with average kinetic energy of approximately 20,000 eV) after the neutrons are emitted. The high penetrability of gammas, whose range is of order one meter in steel, ensures that the resulting damage will be uniform over the volume of the sample. The induced activity of these specimens will have very short half-lives (typically minutes) due the systematics of (slightly) proton-rich nuclei. The resulting radiation-induced hardening can subsequently be evaluated by proper experimental techniques. Accomplishments: ● Four experimental heats of martensitic alloys (similar to Mod9Cr-1Mo) with different Si content (0.5, 1.0, 1.5 and 2.0 weight percent) have been melted by vacuum-induction melting (VIM) practice at the Timken Research Laboratory. ● The VIM heats have been processed into round and rectangular bars, followed by thermal treatments. The heat treatments consisted of austenitizing, quenching, tempering and air cooling to develop a fully-tempered martensitic microstructure in all heats. ● Fabrication of test specimens has been initiated. ● Literature review on relevant topics is in progress