Formation of nanostructured Re–Cr–Ni diffusion barrier coatings on Nb superalloys by TVA method

Nanostructured Re–Cr–Ni multiple component film was chosen as a diffusion barrier layer and was prepared by the original thermionic vacuum arc (TVA) method. It uses an electron beam emitted by an externally heated cathode (a filament which is grounded) and accelerated by the high anodic voltage. The electron beam can evaporate the anode materials as much as to create a dense gaseous metal atmosphere between the cathode and anode in which the electrons can build up dense pure plasma which expands out in the surrounding vacuum space toward the substrates. The Re and Re–Cr–Ni films were deposited using: (i) a single discharge in Re vapors and (ii) two independent discharges in Re and Ni / Cr vapors, running in the same vacuum vessel. The appropriate Cr / Ni raw composition of 25 / 75 at.% was found in order to obtain the desired Re30Cr10Ni composition.