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University of Nevada, Las Vegas

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Las Vegas (Nev.)

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This task 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.

Recent Accomplishments:

● Tensile properties of T91 grade steels containing 0.5, 1.0, 1.5 and 2.0 weight percent (wt%) silicon (Si) have been evaluated at temperatures ranging between ambient and 550°C. The engineering stress vs. strain (s-e) diagrams for all four heats of T-91 grade steels are illustrated in Figures 1-4, located in the technical portion. As anticipated, the magnitudes of both the yield strength and the ultimate tensile strength were reduced with increasing temperature.

● The extent of failure strain (ef) was not significantly affected by the variation in the testing temperature for steels containing 0.5 and 1 wt% Si. However, the magnitude of ef was gradually reduced in steels containing 1.5 and 2 wt% Si in the temperature regime of ambient to 400oC, followed by a significant increase at 550oC, as shown in Figures 3 and 4, respectively. The occurrence of reduced ef in this temperature regime may possibly be attributed to dynamic strain ageing (DSA), which is currently under investigation by transmission electron microscopy (TEM).

● Stress corrosion cracking (SCC) evaluation by the slow strain rate (SSR) technique is in progress involving steel containing 0.5 and 1.5 wt% Si. The effect of controlled potential on the SCC susceptibility will also be studied soon.

● The localized corrosion study by cyclic potentiodynamic polarization (CPP) technique revealed active-passive behavior with a positive hysterisis loop for steels containing 0.5 and 1.5 wt% Si. The magnitude of Ecorr became more active with increasing temperature. This behavior is consistent with the previous data on steels containing 1 and 2 wt% Si.


Corrosion and anti-corrosives; Eutectic alloys; Lead-bismuth alloys; Martensitic stainless steel; Nuclear reactors — Materials — Testing; Silicon; Steel – Embrittlement; Stress corrosion

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Corrosion and anti-corrosives--Testing; Eutectic alloys; Nuclear reactors--Materials--Testing


Materials Science and Engineering | Metallurgy | Nuclear Engineering | Oil, Gas, and Energy

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