Effect of Al plating on growth behavior of TGO layer in CoCrNiAlY–YSZ–RSZ dual-ceramic coating

Thermally grown oxides (TGO) are the key to determine the longevity of thermal barrier coatings (TBCs). This study investigates the growth behavior of the TGO layer in a dual-ceramic coating consisting of CoCrNiAlY, yttria-stabilized zirconia, and rare earth-stabilized zirconia (CoCrNiAlY–YSZ–RSZ) with an Al plating layer. The results demonstrate that these inherent defects (e.g., holes or cracks) in the dual-ceramic layer without Al plating provide diffusion channels for oxygen. These diffusion channels lead to a high oxidation weight gain rate, severe CoCrNiAlY elemental diffusion, and rapid TGO growth. However, the use of Al plating layer effectively seals these inherent ceramic layer defects and leads to the formation of a dense and continuous alumina barrier layer. This barrier layer significantly inhibits internal oxygen diffusion as well as rapid TGO growth. Therefore, the dual-ceramic coating fabricated with Al plating layer exhibits an extremely low oxidation weight gain rate compared to the coating without Al plating. •Effect of Al plating on growth behavior of TGO in dual-ceramic coating was studied.•The coating without Al plating showed severe oxygen diffusion and TGO growth.•The Al plating greatly inhibited rapid oxygen diffusion and growth of TGO layer.•The coating with Al plating showed an extremely low oxidation weight gain rate.