Research on the oxidation behavior and oxidation mechanism of NiCrAl-bentonite abradable seal coatings at 650 °C

Abstract

To study the oxidation behavior and microstructure transformation mechanism of NiCrAl-bentonite abradable seal coatings (ASCs), the NiCrAl-bentonite ASCs were prepared on GH4169 substrate with NiAl as the bonding layer, and the oxidation experiments were carried out at 650 °C at different time (24 h, 48 h, 72 h, 96 h, 144 h, 192 h). The evolution of surface, interior, and interface microstructure of the coating with different oxidation time was analyzed through X-ray diffractometer (XRD) and scanning electron microscope (SEM). The results indicated that the microstructure changes of the coating surface were as follows: the initiation of spot-like oxide → the growth of acicular oxide → the production of continuous oxidation film → the generation of NiO. The internal microstructure changes of the coating were as follows: the formation of Cr oxide layer → the formation of mixed oxide layer. The microstructure changes of the coating's interface were as follows: the initiation and growth thickening of the oxide layer. Element diffusion and oxygen partial pressure controlled the overall oxidation behavior of the coating. The formation of NiO and α-Al₂O₃ on the surface of coating after oxidation for 192 h at 650 °C had a bad effect on the service performance of the coating.