Interface regulation of nickel-phosphorus coatings and surface quality control of lenses in precision glass molding

Precision glass molding technology is widely employed for the mass production of optical lenses owing to its high efficiency and low cost. The surface quality of molded lenses, which directly determines their optical performance, is jointly governed by the surface condition of the mold core and the molding process. Nickel–phosphorus coatings are extensively used for ultra-precision molds due to their excellent machinability; however, under high-temperature conditions, they undergo a transition from an amorphous to a crystalline state with grain precipitation, resulting in increased mold surface roughness and degraded optical performance of molded lenses. To improve the surface quality of lenses produced by high-temperature glass molding, this study systematically investigates the thermally induced grain precipitation mechanism of nickel–phosphorus coatings and the dynamic evolution of surface crystalline particles at elevated temperatures. The evolution mechanism of coating surface roughness under coupled high-temperature and high-pressure conditions is clarified, and methods for grain size control and mold core heat treatment are proposed. In addition, a surface roughness transfer model for high-temperature glass molding is established to elucidate the mechanism of abnormal roughness variation during molding, and a temperature-controlled molding method is developed to reduce the surface roughness of glass lenses. Experimental results show that the surface roughness of glass microlens arrays can be controlled below that of the nickel–phosphorus-coated mold core. After high-temperature heat treatment, the surface roughness Rq of the nickel-phosphorus coating reached 5.96 nm, while the molded lens achieved a surface roughness Rq of 5.40 nm. This study provides a theoretical basis for the precision molding of glass lenses with high surface quality.