Nitrogen ion implantation-induced friction reduction of Ni-P coatings for precision glass molding

Improving the friction-reduction and anti-adhesion performance of nickel-phosphorus (Ni-P) coatings during precision glass molding (PGM) is critical for enhancing mold service stability and the replication quality of microstructures. In this study, nitrogen (N) ion implantation was employed to modify the surfaces of Ni-P coatings, and subsequent heat treatment (HT) was introduced to tailor the near-surface structure and interfacial state. Ion implantation simulations combined with multiscale experimental characterizations were conducted to systematically investigate the effects of N ion implantation and HT on the structural evolution, surface properties, and PGM performance of Ni-P coatings. The results show that N ion implantation forms a modified near-surface layer with compositional gradients and structural heterogeneity in the Ni-P coating. HT further induces surface elemental redistribution and the formation of Ni-O-related bonding. The N-implanted + HT sample exhibits higher surface hardness and improved resistance to plastic deformation, while its wettability changes from a hydrophilic state to a weakly hydrophobic state. Friction tests demonstrate that the N-implanted + HT sample shows a lower and more stable coefficient of friction, indicating that the modified surface layer effectively reduces interfacial shear resistance during sliding contact. Chalcogenide glass (ChG) PGM experiments further reveal that the N-implanted + HT mold promotes the flow of softened glass into microstructures, increases the filling height of glass microfeatures, and effectively suppresses the adhesive transfer of Ni elements onto the glass surface. Overall, N ion implantation synergistically enhances the friction-reduction and anti-adhesion performance of Ni-P coatings by improving the load-bearing capacity of the near-surface layer, reducing the real contact area, regulating the surface chemical state, and weakening mold-glass interfacial adhesion. These findings provide experimental evidence and mechanistic insight for the surface modification and performance enhancement of Ni-P coatings used in PGM.