Session: CS-17-02 EAF Testing Outcomes

Paper Number: 105888

105888 - Microstructure Characterization of Eu Incefa-Scale 316l Stainless Steel Fatigue Specimens – Mechanistic Understanding 

A pressurized water reactor (PWR) primary environment can have a deleterious effect on the fatigue lifetime of austenitic stainless steels. INCEFA-SCALE (INcreasing safety in NPPs by Covering gaps in Environmental Fatigue Assessment - focusing on gaps between laboratory data and component SCALE) is a five-year project supported by the European Commission HORIZON2020 programme and it kicked off in October 2020. One of the main goals of the INCEFA-SCALE project is to develop an improved mechanistic understanding behind the effect of a PWR primary environment on the fatigue behaviour of austenitic stainless steels through coordinated extensive characterisation of as-machined and tested specimens at partner organizations. This work focuses on the microstructure characterization by optical microscope, scanning electron microscope and analytical electron microscopy (including electron backscatter diffraction (EBSD), scanning/transmission electron microscopy (STEM/TEM), X-ray energy dispersive spectroscopy (EDS) and electron diffraction) of as-received and post-mortem 316L stainless steel fatigue specimens. Hardness, grain structure, inclusions, and delta ferrite of the as-received 316L materials were investigated. The surface roughness, machining induced deformation layers and ultra-fined grain structure of as-machined ground and polished specimens were studied. Post-mortem characterization of fatigue specimens tested in air and high-temperature PWR water environments with different surface finishes and loading parameters was performed. Effects of surface finish, loading parameters and environments on the fatigue behaviour of 316L stainless steel are discussed. A ground surface finish and the exposure to a PWR environment result in a decreased low-cycle fatigue lifetime, an enhanced fatigue crack initiation and an accelerated fatigue crack growth rate of 316L austenitic stainless steel.

Presenting Author: Aleks Vainionpää VTT Technical Research Centre of Finland

Presenting Author Biography: Aleks Vainionpää obtained his bachelor's and master's degree in Mechanical Engineering at Aalto University School of Engineering and is currently working as a Research Scientist at VTT Technical Research Centre of Finland. His research is mainly focused on various nuclear materials and he has expertise in material characterization and fractography using advanced scanning electron microscopy techniques.

Authors:

Aleks Vainionpää VTT Technical Research Centre of Finland
Julio Spadotto Henry Royce Institute, Department of Materials, University of Manchester
Zaiqing Que VTT Technical Research Centre of Finland
Brian Connolly Henry Royce Institute, Department of Materials, University of Manchester
Alec Mclennan Jacobs
Sergio Arrieta University of Cantabria
Joseph Huret IRSN
Thomas Damiani EPRI