45 - Portevin-Le Chatelier effects in 316L stainless steels processed by LPBF for nuclear applications

Abstract

316L austenitic stainless steels are commonly used in core components in the nuclear industry, acting as structural materials in the primary circuit of pressurized water reactors (PWR). Due to the aggressive environment involved in such applications, 316L stainless steels may be susceptible to stress corrosion cracking (SCC), potentially leading to the plant shutdown. On the other hand, additive manufacturing technologies are of growing interest of the nuclear industry. Among these processes, laser powder bed fusion (LPBF) is a promising tool for the replacement of obsolete or unique components [1]. There is, however, a lack of knowledge on the SCC resistance of 316L stainless steels processed by LPBF due to their significantly different microstructures compared to conventional manufacturing processes (e.g. forging). To this aim, a thorough study of the mechanical properties of 316L LPBF at PWR operating temperatures, i.e. between 290°C and 340°C, is first needed. Tensile tests at room temperature, 300°C and 340°C were carried out on stress-relieved 316L LPBF specimen at four different strain rates ranging from 10-5 to 10-1 s-1. Strain fields during each test were monitored by digital image correlation (DIC). At room temperature, the strain rate sensitivity was positive and similar to the conventionally manufactured 316L. This positive strain rate sensitivity was lost at 300°C, and serrations were noticeable on the stress-strain curves at lower strain rates, hinting at Portevin-Le Chatelier effects. This was confirmed by digital image correlation, which highlights nucleation and propagation of strain localization bands during tensile tests. Similar observations were made at 340°C. Finally, tensile tests were performed on recrystallized 316L LPBF specimens to assess the effect of the as-built microstructure on the PLC effects.

Speaker

Sylvain Dépinoy

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Mines Paris Université PSL, MAT - Centre des Matériaux, CNRS UMR 7633, Evry, France

Conference

45 - Portevin-Le Chatelier effects in 316L stainless steels processed by LPBF for nuclear applications

Date/Time

21/03/2024

4:25 pm -4:45 pm

Location

Room 8