Submicron structure of rhenium-base diffusion barrier coating layer on a nickel-base superalloy

Abstract

Cross sectional structure of a Re-based diffusion barrier layer coated on a Ni-based single-crystal superalloy has been investigated in submicron scale. The barrier layer was prepared by electroplating of a Ni-73 at%Re film onto the alloy substrate, followed by a Cr-pack cementation in a mixture of Ni-30Cr and Al2O3 powders at 1573 K for 36 ks in vacuum. The diffusion barrier containing 38 at%Re, 35 at%Cr, 16 at%Ni and few amount of Al was identified to be topologically close-packed σ-phase using electron backscattered diffraction method. Voids formed with precipitatesin the diffusion barrier layer. Poly-crystallization and γ′-phase coarsening occurred in the superalloy substrate close to the Re-based alloy layer. © 2007 The Japan Institute of Metals.