Creative Preparation of High-oxidation Resistant Coating on Nb-base Heat-resistant Alloys using Molten-salt Electrodeposition and Self-systematization

在Ni电沉积后，采用熔盐电解液电沉积Al，在Nb-W和Nb-W- mo合金表面制备了Ni铝化物/Ni双层镀层。薄镍层涂层试样在初始阶段表现出强烈的氧化反应。相反，Ni层较厚的涂层试样具有较高的抗氧化性。对于Ni层较厚的涂层试样，在氧化试验过程中，Ni层与合金基体扩散形成由Ni- nb合金组成的中间层。这些中间层有助于维持表层高浓度的Al，抑制层的剥落，从而提高涂层的抗氧化性。

Coatings of Ni aluminide/Ni bilayer on Nb-W and Nb-W-Mo alloys were prepared by the electrodeposition of Al using a molten salt electrolyte after the Ni electrodeposition. The coating specimen with a thin Ni layer showed a vigorous oxidation during the initial period. On the contrary, the coating specimen with a thick Ni layer showed a high oxidation resistance. For the coating specimen with a thick Ni layer, intermediate layers consisting of Ni-Nb alloys were formed by the diffusion of the Ni layer and the alloy substrate during the oxidation test. These intermediate layers contributed the maintenance of a high concentration of Al in the surface layer and the suppression of spallation of the layers, leading to the improvement in the oxidation resistance of the coating.