Influence of high-pressure gaseous hydrogen on the low-cycle fatigue and fatigue crack growth properties of a cast titanium alloy
Artikel i vetenskaplig tidskrift, 2014

In the present study, the effect of gaseous hydrogen on the fatigue properties of a commonly used aerospace titanium alloy (Ti–6Al–4V) was studied. The low-cycle fatigue and fatigue crack growth properties were investigated at room temperature in ambient air and 15 MPa gaseous hydrogen. Results showed that the low-cycle fatigue life was significantly reduced in hydrogen, and the detrimental effect was larger at higher strain amplitudes. The fatigue crack growth rate in hydrogen remained unaffected below a critical stress intensity ΔKn E 17 MPa√m, while beyond this value, the fatigue crack growth rate fluctuated and increased with increasing ΔK. Fractography analysis clearly showed that gaseous hydrogen mainly affected the fatigue crack growth rate. On the fracture surfaces, striations were noted over the entire crack growth region in air, whereas in hydrogen striations were noted at stress intensities lower than ΔKn. Above ΔKn, secondary cracks and brittle flat surfaces with features similar to crack arrest marks were mostly observed in hydrogen. Microstructural analysis along the crack growth direction showed that the crack followed a transgranular path in air, i.e. through α colonies. In hydrogen, the crack also grew along the prior β grain boundaries and at α/β interface within the α colonies. Thereby, the detrimental effect of hydrogen in cast titanium alloy was attributed to a change in the fracture process during crack propagation.

Fatigue

Hydrogen embrittlement

Mechanical characterisation

Titanium alloys

Fracture

Electron microscopy

Författare

Raghuveer Gaddam

Sandvik Materials Technology

Lulea tekniska Universitet

Magnus Hörnqvist Colliander

Chalmers, Teknisk fysik, Materialens mikrostruktur

Marta-Lena Antti

Lulea tekniska Universitet

Robert Pederson

Lulea tekniska Universitet

Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing

0921-5093 (ISSN)

Vol. 612 354-362

Ämneskategorier

Maskinteknik

Materialteknik

Annan materialteknik

Styrkeområden

Materialvetenskap

DOI

10.1016/j.msea.2014.06.060