An investigation of micro-mechanisms in hydrogen induced cracking in nickel-based superalloy 718
Journal article, 2016
Hydrogen embrittlement of the nickel-iron based superalloy 718 has been investigated using slow strain rate tests for pre-charged material and also in-situ hydrogen charging during testing. Fractography analyses have been carried using scanning electron microscopy, electron back-scattering diffraction and orientation image microscopy concentrating on the influence of microstructural features and associated micro-mechanisms leading to hydrogen induced cracking and embrittlement. It was observed that hydrogen induced transgranular cracking initiates at micro-voids in the crystal lattice. Similar behaviour has been observed in multi-scale finite element chemo-mechanical numerical simulations. In contrast, hydrogen induced localized slip intergranular cracking was associated with the formation of micro-voids in intergranular regions. The effects of grain boundary and triple junction character on intergranular hydrogen embrittlement were also investigated. It was observed that low end high angle misorientations (LHAM), 15 degrees 55 degrees. Finally, the use of grain boundary engineering techniques to increase the resistance of super alloy 718 to hydrogen induced cracking and embrittlement is discussed.
grain-boundary design
corrosion
Electron
character
polycrystalline materials
Microstructures
intergranular
alpha-brass
Crack mechanics
strain
stress
Corrosion and embrittlement
triple junction
resistance
Grain boundaries
embrittlement
Author
S. Jothi
Swansea University
S. V. Merzlikin
Max Planck Institut fur Eisenforschung
T. N. Croft
Swansea University
Joel Håkan Andersson
Chalmers, Materials and Manufacturing Technology, Surface and Microstructure Engineering
S. G. R. Brown
Swansea University
Journal of Alloys and Compounds
0925-8388 (ISSN)
Vol. 664 664-681Subject Categories (SSIF 2011)
Metallurgy and Metallic Materials
Areas of Advance
Materials Science
DOI
10.1016/j.jallcom.2016.01.033