“…Other proposed approaches involve diffusion barrier layers, such as TiN layer [20], Al-O-N thin-film layer [21,22], Cr-O-N thin-film layer [22], Re (W)-Cr-Ni layer [23,24] and Ni-W diffusion barrier [15]. Among various diffusion barrier candidates, ␣-Al 2 O 3 is a very effective diffusion barrier material to suppress the inter-diffusion between MCrAlY and superalloy [25,26].…”