Pt deposition on Ni-based superalloy via a combination of galvanic displacement reaction and chemical reduction

Abstract

We demonstrate the deposition of Pt film on a nickel-based superalloy (CMSX-4) via a combination of galvanic displacement reaction and chemical reduction. The aqueous plating bath contains an optimized mixture of Pt precursor (H2PtCl6), pH adjuster (NaOH), and reducing agent (HCHO). Both time-evolved UV–Vis and X-ray absorption spectra on the plating bath indicate a sequential chemical reduction of Pt4+ → Pt2+ → Pt. In addition, a parasitic galvanic displacement reaction occurs in which Ni, Al, and Co from the CMSX-4 suffer from corrosive dissolution whereas the Pt4+ ions from the plating bath are reduced directly. This surface-mediated galvanic displacement reaction produces numerous Pt nanoparticles serving as the nucleation sites for chemical reduction of Pt4+ from HCHO. Therefore, typical sensitization and activation steps for electroless plating are not necessary in our plating bath. From X-ray diffraction pattern, the Pt film adopts a fcc polycrystalline structure. Images from scanning electron microscope confirm the formation of a dense and continuous Pt film with 1 μm thickness.