Preparation and Performance Evolution of Plasma Sprayed Abradable CuAl/PHB-NiAl Layered Seal Coatings.

In this study, a double-layered CuAl/PHB-NiAl seal coating was prepared on a GH4169 substrate by atmospheric plasma spraying. The evolution of the microstructure and mechanical properties of the coating under simulated working conditions was studied. The surface hardness of as-sprayed coating decreased with an increase in the temperature from 25 to 700 °C, decreasing from 90.42 HR15Y to 66.83 HR15Y. A CuO phase was formed in the coating and the oxidation weight gain rate increased with an increase in the temperature when the coating was constantly oxidized at 500~700 °C for 100 h. The hardness of metal matrix in the coating increased with the extension in the oxidation time at 600 °C, increasing from 120.8 HV to 143.02 HV. The residual stress of the as-sprayed porous CuAl top-coating was less than that of the top-coating/bond-coating interface, and it is further relieved by about 15~20 MPa after heat treatment. The coating porosity first increased and then decreased when the oxidation time was 1000 h. The further ablation of PHB and the formation of oxide were concluded to be the main reasons for the evolution of porosity.