An investigation of micro-mechanisms in hydrogen induced cracking in nickel-based superalloy 718

• 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.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Metallurgi och metalliska material (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Metallurgy and Metallic Materials (hsv//eng)

Nyckelord

triple junction

Microstructures

resistance

Electron

strain

corrosion

alpha-brass

Corrosion and embrittlement

intergranular

grain-boundary design

character

embrittlement

stress

Grain boundaries

Crack mechanics

polycrystalline materials

Manufacturing and materials engineering

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art (ämneskategori)

ref (ämneskategori)