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3612 |
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Thursday, May 22, 2014, Hall H2 10:40 AM Power Generation - Industrial Gas Turbines 2 |
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Isothermal and thermo-cyclic performance of multi-layer bond coat systems for gas turbines |
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Nicholas Curry* / University West Production Technology Centre, Sweden Wyszomir Janikowski/ University of Manchester, UK Nicolaie Markocsan/ University West, Sweden Lars Östergren/ GKN Aerosapce Engine Systems, Sweden Xin-Hai Li/ Siemens Turbomachinery, Sweden Mitch Dorfman/ Sulzer Metco, USA |
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This study investigates the high temperature performance of MCrAlY coatings aimed at gas turbine applications. Bondcoats with varying chemical compositions were manufactured using Air Plasma Spraying (APS) and High Velocity Air Fuel (HVAF). Single as well as dual layer systems with uniform thicknesses were produced. Coating lifetimes were assessed using two independent furnaces cycling at 1100°C. Separately, coatings underwent isothermal heat treatment at 950°C over a 10-400h range of exposure times. Microstructural evolution was examined with SEM aided with image analysis software to characterise oxide and porosity contents. Analysis carried out with Energy Dispersive X-ray (EDX) provided insight into diffusion of elements and scale formation mechanisms. X-Ray Diffraction (XRD) analysis was performed to precisely identify the oxides forming at the bondcoat interface. The kinetics of oxidation were quantified by Thermogravimetric Analysis (TGA). Additionally, 3D maps of the interface were obtained with equipment based on light stripe projection. The results were combined together in an effort to explain the phenomena underpinning failure and to determine which coating properties are decisive for the durability. The mixed HVAF-APS bondcoats showed a slight advantage over APS coatings in terms of lifetime. |