High temperature oxidation behavior of Hf/Zr/Y co-doped CoAlNiCrFe high entropy coatings fabricated by high-speed laser cladding

CoAlNiCrFe high entropy coatings co-doped with reactive elements (REs, HfZr\HfY\ZrY) are prepared by high-speed laser cladding. At the initial oxidation, the REs inhibits the generation of α-Al₂O₃ slightly. The long-term oxidation results demonstrate that the growth rates of the three REs-doped TGO are reduced: particularly, the Hf-Y doped one exhibits the lowest growth rate (2.55 ± 0.09μm/200 h). Moreover, the Hf-Y doped and Zr-Y doped ones show similar TGO spallation rate (0.29 ± 0.16 % and 0.98 ± 0.23 %, respectively) compared to the REs-free one (50.7 ± 5.1 %). Both the TGO growth mechanism and their spallation behavior of the REs-doped and REs-free coatings are discussed thoroughly.