Microstructural and topographical changes of Ni-P plated moulds in glass lens pressing

The changes in microstructure and topography of nickel-phosphorus (Ni-P) plated steel moulds in a glass lens moulding process were investigated by heating tests. The results show that, at a high temperature, Ni atoms diffuse from the inner Ni-P plating layer into the outer release agent coating consisting of precious metals. The atomic diffusion leads to partial surface swelling, which makes the mould surface rough and cloudy. The diffusion is influenced by the temperature, interface structure and stress state of the moulds. These findings provide references for developing new mould materials and for improving the service life of the moulds.