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| Abstract No.: |
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Scheduled at:
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Monday, May 03, 2010, Hullet Room 12:10 PM
Gas Turbines 1
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| Title: |
Oxidation behavior of MCrAlY bond coats manufactured by plasma, HVOF and cold gas dynamic spraying
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| Authors: |
Patrick Richer / University of Ottawa
Department of Mechanical Engineering
, Canada
Mohammed Yandouzi / University of Ottawa, Canada
Louis Beauvais/ Vac Aero International Inc., Canada
Bertrand Jodoin*/ University of Ottawa, Canada
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| Abstract: |
The performance of MCrAlY bond coats used in gas turbine engines has been the focus of numerous studies and publications. These studies have shown that the bond coat properties and microstructure influence its oxidation behaviour, which in turn is directly linked to some of the major TBC failure mechanisms. In particular, it has been demonstrated that high temperature processes such as plasma and HVOF spraying cause in-spray surface oxidation of the deposited particles. The inclusion of these oxides in the bond coat microstructure was shown to promote the growth of detrimental fast-growing mixed oxides during thermal cycling, thus limiting TBC performance and longevity. Despite these findings, thermal spraying techniques such as plasma and HVOF remain the most commonly used deposition techniques for bond coats. Cold Gas Dynamic Spraying (CGDS) is a modern coating process that relies on severe plastic deformation resulting from the high-velocity impact of particles on a substrate to produce coatings. Due to its relative low process temperature and use of inert gases, CGDS has been shown to be capable of producing dense coatings with very low oxide contents. This paper examines and compares the oxidation behaviour of CoNiCrAlY coatings manufactured by plasma, HVOF and CGDS deposition techniques when subjected to isothermal heat treatments. Comparison of the as-deposited coating microstructures is achieved by means of scanning electron microscopy (SEM). Investigation of the oxide compositions and growth dynamics is achieved by X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). Oxide growth rates were also determined by a series of mass gain measurements. Investigation of the effect of coating porosity of the oxidation behaviour is also presented.
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