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| Hauptseite > Publikationsdatenbank > Differences in Oxidation Resistance of MCrAlY Coatings Manufactured by Low Pressure and High-Velocity Atmospheric Plasma Spraying |
| Hauptseite > Publikationsdatenbank > Differences in Oxidation Resistance of MCrAlY Coatings Manufactured by Low Pressure and High-Velocity Atmospheric Plasma Spraying |
| Poster (After Call) | FZJ-2015-05486 |
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2015
Abstract: Gordon Conference High Temperature CorrosionNew London, USA, 26 – 31 July 2015Differences in Oxidation Resistance of MCrAlY Coatings Manufactured by Low Pressure and High-Velocity Atmospheric Plasma SprayingE. Hejrani1) , D. Sebold2), G. Mauer2), D. Naumenko1), R. Vassen2), W.J. Quadakkers1)Forschungszentrum Jülich, Institute for Energy and Climate Research (IEK)52425 Jülich, D1) Microstructure and Properties of Materials (IEK-2)2) Materials Synthesis and Processing (IEK-1)In industrial gas turbines coatings of the MCrAlY type (M = Co, Ni) are commonly used to protect metallic components against damage by high temperature oxidation and corrosion processes. They are also frequently used as bond coats in ceramic thermal barrier coating systems. Due to the high affinity to oxygen of the alloying additions Al, Cr and especially Y, MCrAlY coatings are often manufactured by low pressure plasma spraying (LPPS) to minimize oxygen uptake of the coating and prevent oxidation of the mentioned alloying elements during processing. Plasma spraying at atmospheric conditions (APS) is a cost-effective alternative if it would be possible to limit the oxygen uptake as well as to obtain sufficiently dense coatings. In the present investigation free standing MCrAlY coatings with a thickness of approximately 3 mm were manufactured using a three-cathode plasma torch with a high velocity nozzle and adapted plasma parameters. The high particle velocities result in reduced particle oxidation during flight and contribute to coating densification by kinetic rather than thermal energy. Free standing coatings with the same composition were additionally manufactured by conventional low pressure plasma spraying (LPPS).From the free standing coatings rectangular specimens with a thickness of 2 and 0.6 mm were machined and investigated in respect to cyclic and isothermal oxidation testing at 1100 and 1000°C. The isothermal tests were carried out in a thermo-gravimetrical analysis (TGA) facility to obtain detailed information about oxidation kinetics. The use of specimens of different thickness allowed estimating the differences in reservoir of free, i.e. non-oxidized Y in the coatings and its effect on mechanisms of surface scale formation. The coating microstructures as well as external and internal oxidation products were characterized by using a combination of analysis methods such as light and electron optical microscopy, energy and wave length dispersive x-ray analysis (EDX/WDX), x-ray diffraction (XRD), glow discharge optical emission spectroscopy (GDOES) as well as Laser Raman Spectroscopy (LRS). Differences in scale growth rate and adherence as function of coating manufacturing process and specimen thickness will be illustrated and correlated with the results of the detailed microstructural analyses.
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