June 24-29, 2018
Doping of reactive elements (RE) as Y or Dy into the composition of NiAl bond coat in EB-PVD thermal barrier coatings (TBC) leads to an increase of performance characteristics of the latter. The report contains results of structure and property investigation of NiAl / ZrO2-8% Y2O3 condensed TBC. Thickness of the condensed TBC is 40 ... 50/140 ... 160 μm done on Ni-based super alloy samples-buttons. The effect of Y or Dy dopants into NiAl bond coat, including their gradient distribution through-the-thickness of NiAl layer was considered as well. It was found that the additions of REs reduce the average grain size of the condensed NiAl layer by 4-5 times. It was shown that REs precipitate both inside the NiAl grains and along boundaries in the form of particles ranging in size from 5 nm to 20 mcm, depending on the level of their concentration. REs optimal content was estimated to ensure the highest thermal cyclic durability. It is noted that positive effect of Dy doping into NiAl (in comparison with Y) occurs due to improvement of adhesion of the scale layer because of the growth of spindle-shaped precipitates of dysprosium oxides in it, slowdown of the growth rate of Al2O3 scale at the metal-ceramic interface and inhibition of interdiffusion of Al (about 1,2 times) in TBC-super alloy system.
A.V. Mykytchyk, K. Yu Yakovchuk, Yu.E. Rudoy, E.V. Onoprienko, and R.A. Tkach, "Structure and properties of condensed gradient coatings with NiAl-bond coat doped with Y or Dy" in "Thermal Barrier Coatings V", Prof. Dr. Robert Vaßen, Forschungszentrum Jülich GmbH, Germany Brian Hazel, Pratt & Whitney, USA Prof. Dr. Uwe Schulz, German Aerospace Center, Germany Dr. Michael J. Maloney, Pratt & Whitney, USA Dr. Ram Darolia, GE Aviation (Retired), USA Eds, ECI Symposium Series, (2018). http://dc.engconfintl.org/tbcv/34