Innovative synthesis of compact NiPt coatings on nickel-based GH3535 alloy using liquid sodium: Mechanism revealed by experiments and simulations

The Pt–Ni coating holds great application potential in aerospace, catalysis, and biomedicine. This study developed a novel approach to fabricate dense NiPt coatings on nickel-based GH3535 alloy by immersing the alloy in Pt-doped liquid sodium: Pt first dissolves in liquid sodium, then diffuses to the GH3535 surface and reacts with Ni to form NiPt. Temperature is a critical factor for NiPt coating formation: Pt in sodium starts diffusing to the alloy surface as elemental Pt at 350 °C; temperatures≥500 °C initiate Pt–Ni reactions to form NiPt, but a dense coating requires temperatures≥600 °C, with coatings synthesized at 60–700 °C exhibiting excellent compactness. The coating's crystal structure evolves with immersion time: tetragonal NiPt forms for durations <48 h, while longer times (>48 h) drive its transformation into a face-centered cubic [Ni,Pt] solid solution. Combining first-principles calculations, machine learning-accelerated molecular dynamics, and classical molecular dynamics, the study reveals that Pt atoms in liquid sodium diffuse uniformly onto GH3535 surfaces. Both theoretical and experimental results confirm Pt–Ni interdiffusion at the interface, which generates a [Pt,Ni] solid solution and ensures strong bonding between the coating and the alloy substrate.