Cyclic Oxidation Behavior of TBC Systems with a Pt-Rich γ-Ni+γ′-Ni3Al Bond-Coating Made by SPS

Abstract

To obtain long-lasting thermal barrier coating (TBC) systems, two types of Pt-rich γ-Ni+γ′-Ni3Al bond-coatings (BC) were fabricated by spark plasma sintering (SPS). The former had the highest possible Pt content (Ni-30Pt-25Al in at.%) while the latter had the highest possible Al level (Ni-28Al-17Pt in at.%). Hf was added as a reactive element. TBCs were fabricated on different superalloys (AM1, Rene N5 and MCNG) with the aforementioned BCs and with zirconia stabilized with yttria top coats made by SPS or electron beam physical vapor deposition (EBPVD). The cyclic oxidation resistance of these systems was studied at 1,100 °C in air. Most TBCs with a Pt-rich γ–γ′ BC showed better thermal cycling resistance when compared to the reference TBCs (β-(Ni,Pt)Al diffusion BC and EBPVD ceramic top coat), with lifetimes up to 1,745 cycles instead of 700 for the reference, and despite the fabrication defects observed within the SPS BCs. Cu was tested as an addition in the BCs and proved to have a slight negative effect on the system lifetime. Moreover, the fourth generation MCNG substrate led to the best cyclic oxidation behavior.