Wear of mold surfaces: Interfacial adhesion in precision glass molding

Micro-optical components, such as glass-based microlens arrays, have become essential in applications relying on advanced optical systems such as 3D displays, optical fiber coupling, and unmanned vehicles. Precision glass molding (PGM) has emerged as a promising method for fabricating optical components based on the formability of glasses beyond their glass transition temperature (Tg), while adhesion wear strength and mechanism of mold-glass interfaces remain major obstacles. This paper aims to explore the adhesion wear mechanisms between mold surfaces and optical glass D-FK95 in PGM. The applicability of WC molds with coatings of Ta–C, AlCrN, and AlTiN was investigated respectively considering their thermodynamic properties and surface energy characteristics. The study identified three adhesion wear mechanisms in the open-air atmosphere with WO3 oxidation on mold surfaces and four adhesion mechanisms featured by scattered distribution, island aggregation, dispersed flow, and planar coverage in an inert atmosphere. It was also found that when the temperature was close to Tg, the WC-glass adhesion force was negligible. The adhesion stress increased to 0.80 MPa with an increase in the applied temperature and pressure. With coating, however, the adhesion stress reduced significantly to 0.03 MPa. The study also concluded that when paired with the D-FK95 glass, the WC mold coated with Ta–C provides the best anti-adhesive performance in comparison to those with AlCrN and AlTiN coatings.