Failure Mechanics of Layered Ceramics and CeramicMetal Coatings due to Environmental Exposure A'M' K

1
Failure Mechanics of Layered Ceramics and
Ceramic-Metal Coatings due to Environmental
ExposureA.M. Karlsson, University of Delaware,
DMR-0346664
Ceramic Top Coat Yttria Stabilized Zirconia
Cracks
Thermally Grown Oxide Aluminum Oxide
tensile load
Metallic Bond Coat NiCoCrAlY
When a structure fails through cracking, it is
expected that the crack grows perpendicular to
the load direction. Not it this case, where we
test how multilayered ceramic-metal coatings
interact during high temperature exposure. As
the structure is subjected to temperatures used
in gas turbine engines (around 1000oC or 1800oF),
along with mechanical loading, cracks are seen to
live their own life. Above, the smiley crack
is show, where the name comes from its shape.
This crack appears without obvious link to the
mechanical load direction, or the thermal
mismatch stresses. This is a repeated phenomena
and was found though the collaborate effort with
the German Aerospace Center. The investigator at
the University of Delaware is currently
investigating how this crack develops, which is
due to a combination of the cyclic loading and
the evolving material properties due to the high
temperatures.
2
Failure Mechanics of Layered Ceramics and
Ceramic-Metal Coatings due to Environmental
ExposureA.M. Karlsson, University of Delaware,
DMR-0346664
As part of the collaboration with Germany
graduate student of University of Delaware, Ms.
Jin Yan, the German Aerospace Center (DLR),
Cologne, Germany, for a three month visit.
Furthermore, the main collaborator in Germany Dr.
Marion Bartsch, has visited University of
Delaware (UD) three times since the start of the
project, working directly with the students at
UD. Two students from UD have visited DLR to
conduct research. Six undergraduate students
and three graduate students have contributed to
this research.
Dr. Bartsch visiting University of Delaware,
meeting with students.