Protective Coatings
In order to enhance the mould insert's lifetime, protective coatings can be applied. “The materials that have been selected for the antistick coatings can be divided into 5 groups including: (1) single layer carbides, nitrides, oxides and borides such as TiN, BN, TiAlN, NiAlN, TiBC, TiBCN, NiCrSiB and Al2O3, (2) nitrides or carbides based gradient and multilayers, (3) nitrides based superlattice films, (4) amorphous carbon or diamond-like carbon and (5) precious metal based alloys”
Experiments carried out by Ma et al. yield the following results: “The higher the temperature, the smaller the wetting angle between glass gob and substrate could be observed. This indicates that severe interface chemical reaction occurred and resulted in the loss of transparency in glass appearance. The wetting experiment in nitrogen ambient improved the sticking situation. The combination of chemically stable substrates and coatings, such as Sapphire (substrate) / GaN (film) and Glass (substrate) / Al2O3 (film) can achieve the best antistick propose. The precious metal films such as PtIr(Platinum, Iridium) coated on the ceramic substrates can effectively reduce the interface reaction between the glass and substrates.”
Although PtIr is used as a standard coating material, it has the disadvantage of being expensive. Therefore, research activities aim at substituting PtIr with cheaper materials.
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