|
4774 |
|
Wednesday, May 11, 2016, Room 3H + 3I + 3J 10:20 AM Power Generation I |
|
High entropy alloy coatings for application as bond coating for thermal barrier coating systems
|
|
Rabi Bhattacharya / UES, Inc., USA Oleg Senkov/ UES, Inc., USA Amarendra K Rai/ UES, Inc., USA Xinqing Ma*/ Surface Technologies Curtiss-Wright, USA Peter Ruggiero/ Surface Technologies Curtiss-Wright, USA |
|
High-entropy alloys (HEAs) have potential to be used as high temperature materials and in coating material applications due to their combination of strength, ductility, thermal stability, corrosion and wear resistance. HEAs typically refer to alloys that are comprised of five or more elements, at or near equi-atomic composition. Some of these alloys are solid solution alloys on simple underlying lattices such as face-centered cubic and body-centered cubic. In this paper, HEA coatings based on NiCoCrAlSi were deposited by high velocity oxy fuel (HVOF) and plasma spray (PS) processes. The coatings were analyzed for phase, microstructure and composition using x-ray diffraction (XRD), scanning electron microscopy (SEM) in combination with energy dispersive x-ray spectroscopy (EDS). Results showed that BCC/B2 phase is the major phase present in the as-produced HVOF coating that was diffusion heat treated at 1080°C. A small amount of L12 phase with a FCC crystal lattice was also found to be present. PS coatings of the same composition alloy showed a two-phase structure consisting of the ordered L12 phase and BCC/B2 phase. The lattice parameters are the same as in the HVOF sprayed coatings, however, the volume fraction of the L12 phase seems to become larger and is comparable with that of BCC/B2 phase. These coatings were oxidized at 1050°C in air. The coating morphology and oxide scales were examined with the aim of developing a high quality bond coat for thermal barrier coating (TBC) systems. |