High temperature behavior of a diffusion barrier coating evolved from ZrO2 precursor layer

The zirconia (ZrO2) as a precursor layer for the diffusion barrier coating (DBC) was deposited by electron beam physical vapor deposition (EB-PVD) between the René N5 superalloy substrate and NiCrAl coating. The high temperature exposure for the N5/ZrO2/NiCrAl system was carried out at 1000 °C for 5 h, 100 h and 200 h in atmosphere to investigate the structure evolution of the ZrO2 precursor layer and the elements interdiffusion of the system compared with the N5/NiCrAl system. The results showed that a sandwich structural DBC (α-Al2O3/rich-Zr/α-Al2O3) was formed through redox reaction between zirconia and aluminum under high temperature, leading to the transformation of N5/ZrO2/NiCrAl system into the N5/DBC/NiCrAl system. It was found that the sandwiched DBC could effectively suppress the interdiffusion of elements compared to the N5/NiCrAl system.