Oxidation resistance and microstructural changes of Pt/Ni+Al two layered coatings were investigated in comparison to those of Pt diffusion coatings. The two layered coatings were successfully prepared by a two-step electroplating process, which involves Pt electroplating followed by Ni+Al-particle composite electroplating. The cross-sectional observations of specimens after the cyclic oxidation test confirmed that the two-layered coatings retarded the formation of voids, suggesting that the top Ni+Al-particle composite layer played a role as the diffusion retarder between the coated layer and the substrate. In addition, the Ni+Al-particle composite coatings preferentially accelerated the formation of the Al2O3 scale on the surface. These results confirmed the beneficial effect of the designed two layered coatings.
