Design of oxidation resistant and spallation resistant low-β/near-γ/γ′-MCrAlYs for thermally-sprayed TBCs

HVOF-MCrAlY + APS-YSZ TBCs, compared to its APS-MCrAlY + APS-YSZ counterparts, are increasingly attractive to gas turbine OEMs and coating developers in recent years; however, producing a TBC with oxidation resistant and spallation resistant single-layer HVOF-MCrAlY bond coating remains to be a challenge, due to cracking in the YSZ/TGO vicinity and along the TGO/MCrAlY interface region. This work studies the influences of alloying elements on the maximum amount of β-NiAl phase in the MCrAlYs, and proposes to develop a single-layer oxidation resistant and spallation resistant HVOF-MCrAlY with a low-β/near-γ/γ′ microstructure, to reduce the strain at the TGO/MCrAlY interface resulted from the B2 → L10 martensite transformation on cooling from elevated temperatures.