Thermal barrier coatings used in airplane engines or land-based gas turbines can show
catastrophic failure (i. e. spallation) typically during cooldown due to thermal expansion mismatch
stresses. However, it is also often noted that spallation occurs minutes, hours, or even days after the
sample is cold. This type of delayed failure, called “desk top spallation” is, up to now, not fully
understood and therefore a field of great interest. Because desk top failure occurs in ambient air, the
working hypothesis is that water vapor from the office environment plays a role. Consequently, a
number of experiments have been designed to verify this hypothesis. The experiments include more
traditional approaches like acoustic emission measurements during cyclic oxidation, but also
innovative new approaches like acoustic emission during water drop testing, and hydrogen
detection at the interface to the thermally grown oxide using ion beam techniques.