Hydrogen embrittlement of super duplex stainless steel - Towards understanding the effects of microstructure and strain


Ornek C., Reccagni P., Kivisakk U., Bettini E., Engelberg D. L. , Pan J.

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, vol.43, no.27, pp.12543-12555, 2018 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 43 Issue: 27
  • Publication Date: 2018
  • Doi Number: 10.1016/j.ijhydene.2018.05.028
  • Journal Name: INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.12543-12555
  • Keywords: Super duplex stainless steel, Hydrogen embrittlement, Load partitioning, Volta potential, Austenite spacing, PROBE FORCE MICROSCOPY, DIGITAL IMAGE CORRELATION, CORROSION BEHAVIOR, WORK FUNCTION, DEFORMATION, CRACKING, SKPFM, SUSCEPTIBILITY, TRANSFORMATION, TEMPERATURE
  • Istanbul Technical University Affiliated: No

Abstract

The effects of austenite spacing, hydrogen charging, and applied tensile strain on the local Volta potential evolution and micro-deformation behaviour of grade 2507 (UNS 532750) super duplex stainless steel were studied. A novel in-situ methodological approach using Digital Image Correlation (DIC) and Scanning Kelvin Probe Force Microscopy (SKPFM) was employed. The microstructure with small austenite spacing showed load partitioning of tensile micro-strains to the austenite during elastic loading, with the ferrite then taking up most tensile strain at large plastic deformation. The opposite trend was seen when the microstructure was pre-charged with hydrogen, with more intense strain localisation formed due to local hydrogen hardening. The hydrogen-charged microstructure with large austenite spacing showed a contrasting micro-mechanical response, resulting in heterogeneous strain localisation with high strain intensities in both phases in the elastic regime. The austenite was hydrogen-hardened, whereas the ferrite became more strain-hardened. SKPFM measured Volta potentials revealed the development of local cathodic sites in the ferrite associated with hydrogen damage (blister), with anodic sites related to trapped hydrogen and/or micro voids in the microstructure with small austenite spacing. Discrete cathodic sites with large Volta potential variations across the ferrite were seen in the coarse-grained microstructure, indicating enhanced susceptibility to micro-galvanic activity. Microstructures with large austenite spacing were more susceptible to hydrogen embrittlement, related to the development of tensile strains in the ferrite. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.