A diffusion couple study was carried out with Ni-based superalloy / gamma'-Ni(3)Al with or without a Re-based alloy layer. The Re-based alloy containing Re, W, Cr, and Ni was formed on a second generation, single crystal Ni-based superalloy by using electroplating processes to form films of 70at%Re-Ni and Ni-20at%W, followed by Cr-pack cementation at 1573K for 36ks. The superalloy with or without the Re-based alloy layer was bonded to a gamma'-Ni(3)Al alloy in vacuum. Diffusion couples were annealed in an evacuated quartz ampoule at 1423 K for 90 and 360ks. After the 360ks diffusion treatment the Re-based alloy remained sound and suppressed inward Al diffusion from the gamma'-Ni(3)Al, it was further found that outward diffusion of alloying elements from the alloy substrate to the gamma'-Ni(3)Al was also significantly reduced by the Re-based alloy layer.