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Cool Software for Hot Materials
As part of NASA's efforts to build upon the philosophy of
"cheaper, better, faster," one way to achieve that
standard is through the increased efficiency of turbine engines.
To help this goal along, NASA's Glenn Research Center awarded
a Small Business Innovation Research (SBIR) contract to
Deformation Control Technology, Inc. (DCT) of Cleveland, Ohio.
Under the contract, DCT has developed a computer model as
an aid to designing ceramic coatings to extend the life of the
coating and the coated component. NASA's interest in the research
stemmed from a desire to develop quantifiable descriptors for
the complex interactions experienced in thermal barrier coating
systems (TBCs). Typical TBCs are composed of three "layers":
the metallic component, an oxidization resistant "bond coat,"
and finally, the ceramic top coat.
![DCT's software and it's ability to generate predictive computer models for coatings, which saves time and money on coating design](images/74B.JPG) |
DCT's software can generate
predictive computer models for coatings, saving time and money
on coating design. |
This software allows for coating designers to measure the
stresses being placed on coatings using computer simulation.
Thermal barrier coatings have traditionally been evaluated using
expensive "Burner Rig" tests. These tests involve a
series of sequential heating and cooling cycles run on cylinders
coated with the substance undergoing testing. The coated cylinders
are run through varying configurations within a temperature range
of 30-1200 degrees Celsius. DCT's new software will contribute
toward reducing the need for extensive "Burner Rig"
tests, since results can be predicted prior to actually producing
the coating.
DCT's pioneering work involved the modeling of the thermal
barrier coating system through finite element analysis and adding
a statistical software package that measures the influence of
material stress drivers on the internal stresses developed during
thermal cycling.
The benefits of this research have meant a reduction in the
cost of experimentation and the development of new design concepts.
The results derived from the prediction models will support the
development of coatings that can be applied to turbine engines.
The turbine engines, with improved coatings, can operate at higher
temperatures with improved efficiency.
The modeling aspect of the research provided one of the first
descriptions of the role of bond coat oxidization in thermal
barrier coating breakdown. In addition, other bond coat and top
coat properties which may influence TBC fatigue have been identified.
Another innovation in the DCT model was accounting for the
growing oxide layer between the bond coat and the ceramic layer.
This oxide is formed at high temperatures when the porous properties
of the ceramic enable oxygen to penetrate to the bond coat surface.
By accounting for the oxide layer in its models, DCT was able
to provide a sound description of the role of oxidization in
TBC failure.
DCT's new method has been successfully used in the TBC design
for electrical power generation turbine applications. Future
applications for improved TBC systems include aerospace, land-based
turbine, and diesel engines.
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