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PSE 2014 - 2014
Helmut Riedl (H. Riedl)
"High temperature oxidation behaviour and mechanical properties of PVD sputtered Mo-Si-B coatings"
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State of the art industrial applications require increased performance and
efficiency, which is in most cases linked to elevated process or combustion
temperatures, even beyond 1000C. Materials exposed to these
temperatures need protective coatings, such as thermal barrier coatings
(TBC), to withstand the applied mechanical and thermal load. However,
typical TBCs are mostly brittle and obtain inferior mechanical properties,
hence the area of use is limited. Refractory-metal-based thin films exhibit
the most promising properties to overcome these requirements, due to their
high melting points, thermal and mechanical properties, and electronic
structure. The excellent creep resistance of Mo-Si-B bulk materials
constitute them as coatings for Ni-based-superalloys for high temperature
applications. Nevertheless Mo1-x-ySixBy coatings are up to now not fully
understood and the knowledge on this system requires further
investigations. Within this study we investigate the mechanical and thermal
properties as well as the oxidation behavior of sputter deposited
Mo1-x-ySixBy thin films in the high temperature regime. Based on the
ternary system and former bulk material studies we focus on compositions
containing x and y ? 0.50, and so distinguish between 12 different
Mo1-x-ySixBy coatings. We used elemental Mo, Si and B targets as well as
powder metallurgical Mo-Si-B targets to reach all preferred compositions. All
coatings exhibit dense and columnar structures in the as deposited state.
Increasing Si and B contents lead to grain refinement, which is also
confirmed through XRD analysis. Vacuum annealing at 900C stabilizes the
crystalline structures of three preferred phases Mo3Si, Mo5Si3, and
Mo5SiB2. During oxidation experiments the formation of a stable SiO2
protection layer on top of the coatings after exposure to 900, 1100, and
1300C for 1h could be observed.

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2011 - 2017 - Christian Doppler Laboratory for Application Oriented Coating Development