  Atom probe tomography (APT), electron probe microanalysis (EPMA) and
nanoindentation were used to characterise the oxygen-rich layer on an
in-service jet engine compressor disc, manufactured from the titanium alloy
TIMETAL 834. Oxygen ingress was quantified and related to changes in mechanical
properties through nanoindentation studies. The relationship between oxygen
concentration, microstructure, crystal orientation and hardness has been
explored through correlative hardness mapping, EPMA and electron backscatter
diffraction (EBSD). The role of microstructure on oxygen ingress has been
studied and oxygen ingress along a potential alpha/ beta interface was directly
observed on the nanoscale using APT.
