Characterization of ion irradiation effects on the microstructure, hardness, deformation and crack initiation behavior of austenitic stainless steel:Heavy ions vs protons

Abstract

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao. Proton irradiation is generally used as a representative alternative of neutron irradiation to improve the current understanding of the mechanisms involved in IASCC. This study assesses the possibility of using heavy ions irradiation to evaluate IASCC mechanisms by comparing the irradiation induced modifications (in microstructure and mechanical properties) and cracking susceptibility of SA 304 L after both type of irradiations: Fe irradiation at 450 C and proton irradiation at 350 C. Irradiation-induced defects are characterized and quantified along with nano-hardness measurements, showing a correlation between irradiation hardening and density of Frank loops that is well captured by Orowan's formula. Both irradiations (iron and proton) increase the susceptibility of SA 304 L to intergranular cracking on subjection to Constant Extension Rate Tensile tests (CERT) in simulated nominal PWR primary water environment at 340 C. For these conditions, cracking susceptibility is found to be quantitatively similar for both irradiations, despite significant differences in hardening and degree of localization.

Effect of dislocation channeling on void growth to coalescence in FCC crystals

“…The Vickers hardness of irradiated samples has been measured to be 310 ± 14 HV 0.02 using the same conditions as for the reference state (20g with 10s hold time). The increase of hardness is thus equal to ∆H V = 117, in agreement with the Frank loop density and size measured (as the major contributor 785 to hardening) following the correlation explained for example in [85].…”

Role of irradiation and irradiation defects on the oxidation first stages of a 316L austenitic stainless steel

“…13). Such behaviour was already reported by several authors [16,17,19]. The literature attest that oxygen diffusion through the inner layer is slower for Cr-rich oxides [7].…”

“…A higher amount of chromium is detected in the inner oxide layer formed on the irradiated area (Cr/ (Cr + Fe + Ni) unirr ≈0.50 vs Cr/(Cr + Fe + Ni) irr ≈0.56). The formation of oxide richer in chromium onto irradiated materials was already reported by several authors [16,17,19].…”

“…On irradiated materials, the number of crystallites is always reported higher but Gupta and Dumerval et al observed smaller crystallites [16,17] whereas Fukuya and Deng et al bigger ones [9,18]. As for the inner oxide the literature agrees that inner oxide layers formed on an irradiated area are richer in chromium but some works attest that the inner oxide is thicker [16,18] while other that it is thinner [17,19]. These different o xidation b ehaviour p robably arise from the different i rradiation a nd o xidation c onditions ( dose, temperature, oxidation duration, etc.).…”

Comparative Study of Two Nanoindentation Approaches for Assessing Mechanical Properties of Ion-Irradiated Stainless Steel 316

“…Experiments by Byun et al [19] on SS316 suggests that hardening due to irradiation is comparable to hardening by deformation-induced dislocation formation. The approach taken herein is analogous to the study detailed in the authors' previous work [14], where the influence of the most pronounced Frank loop obstacles [20] and forest dislocation obstacles in stainless steel are reduced to a simplified fitted model, where σ rad (σ 0 ,dpa) is a first order function that expresses the irradiated hardening and provides a continuum level bulk property response as outlined in [21]…”