Abstract
308L welding duplex stainless steel has been irradiated at 360 °C with 2 MeV protons, corresponding to a dose of 3 dpa at the maximum depth of 20 μm. Microhardness of the δ-ferrite and austenite phases was studied before and after proton irradiation using in situ nanomechanical test system (ISNTS). The locations of the phases for indentations placement were obtained by scanning probe microscopy from the ISNTS. The hardness of the δ-ferrite had a close relationship with the vacancy distribution obtained from the Stopping and Range of Ions in Matter (SRIM) Monte Carlo simulation code. However, the hardness of the austenite phase in the maximum damage region (17–20 μm depth) from the SRIM simulation was decreasing sharply, and a hardness transition region (>20 μm and <55 μm depth) was found between the maximum damage region (17–20 μm depth) and the unirradiated region (>20 μm depth). However, the δ-ferrite hardness behavior was different. A hardness of the two phases increased on the irradiated surface and the interior due to different hardening mechanisms in the austenite and δ-ferrite phases after a long time high-temperature irradiation. A transition region (>20 μm and <55 μm depth) of the Volta potential was also found, which was caused by the deeper transfer of implanted protons measured by scanning Kelvin probe force microscopy.
Highlights
Many devices are irradiated by various high-energy ions in the primary circuit environment of pressurized water reactors (PWR) [1,2,3]
It can be concluded that irradiation hardening has a close relationship with defect types formed in the bulk when the irradiation dose is below saturation
The effects of irradiation on the hardness of 308L welding duplex stainless steel (DSS) stainless steel were investigated in this study and the following conclusions are drawn
Summary
Many devices are irradiated by various high-energy ions in the primary circuit environment of pressurized water reactors (PWR) [1,2,3]. When metal is hardened by ion irradiation, it becomes more brittle. Some components, such as springs and fasteners, could break, causing damage to larger parts if not replaced [5,6]. Various studies of irradiation hardening have been conducted using austenite stainless steels (face-centered cubic, fcc), such as 304L and 316L, which are widely used as nuclear structural materials [10,11,12]. Defect types are most important, as the temperature of PWR is 300–400 ◦C in different circuits and hardening tends to saturate at some radiation doses [21,22,23]. It can be concluded that irradiation hardening has a close relationship with defect types formed in the bulk when the irradiation dose is below saturation
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