The β-NiAl single phase intermetallic compound and two-phase γ/γ’ Ni-Al-based alloys, which usually contain also small amounts of reactive elements (Hf, Y, …) and higher contents of Pt (or Pd, Rh), are the materials applied as Bond Coats in Thermal Barrier Coating systems on superalloys. Their superior high temperature oxidation resistance stems from the formation of slowly growing α-Al2O3 layer and, thus, the protective scale. Reactive elements provide the significant improvement of the scale resistance to spallation, in particular upon thermal cyclic conditions, while the beneficial effect of Pt and Pt-like elements was found to manifest itself in accelerated formation of α-Al2O3 scale even under unfavourable conditions and/or enhanced scale resistance to spallation.

The numerous reports concerning the mentioned effects do not, however, result in their sufficient understanding, which prevents from optimizing the composition and the microstructure of materials. 

This paper is focused on a comprehensive summary of the state of the art in this field, critical discussing the major issues and problems as well as on the challenges related to the optimizing the design of the possibly best effective Bond Coats.