We investigated the temporal degradation of glass moulding dies, made of cemented tungsten carbide coated with PtIr on an adhesive Cr or Ni interlayer, by electron microscopy and atom probe tomography. During the exposure treatments at 630 °C under an oxygen partial pressure of 1.12 × 10−23 bar, Cr (Ni) was found to diffuse outwards via grain boundaries in the PtIr, altering the surface morphology. Upon dissolution of the interlayer, the WC substrate also started degrading. Extensive interdiffusion processes involving PtIr, Cr (Ni) and WC took place, leading to the formation of intermetallic phases and voids, deteriorating the adhesion of the coating

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Coatings in precision glass molding (PGM) experience severe thermo-chemical and thermo-mechanical loads during several hundred or thousand pressing cycles. Until now, little is known about the integrity loss of protective coatings for these applications. Gaining knowledge of fundamental mechanisms on the functional degradation of protective coatings is of great interest. The work presented in this paper investigates compositional changes in the surface-near region of precious metal PVD-coatings after being annealed in hot glass contact. Different characteristic wear zones identified on the samples have been analyzed by light microscopy, SEM/EDX, as well as X-ray photoelectron spectroscopy (XPS). The results are compared to the wear stages observed on molds used in industrial production. A qualitative model for the degradation of the substrate-coating system is proposed, ranging from the initial phases of material alteration to the final coating breakdown. In addition, indications that glass components might play a role in the overall degradation process were found but could not be revealed in detail. With regards to highly precise molding tools for PGM, further work should be focused on the initial phase of wear, since the end of service life time is reached at early degradation stages, far before the coating flake-off

During Precision Glass Molding (PGM), the molding tools have to withstand severe thermochemical and thermo-mechanical loads cyclically. To protect their high-quality optical surface against degradation and increase their service lifetime, protective coatings are applied on the molding tools. In this work, we designed four different PtIr protective coating systems, where the thickness of the PtIr layer and the adhesion layer were varied. Their lifetimes were evaluated and compared using an in-house built testing bench. Among all the studied coating systems, the protective coating, which consists of a 600-nm-thick PtIr layer and a 20-nm-thick Cr adhesion layer, showed the best durability with the longest lifetime. To understand the degradation mechanism of the coating during actual engineering production, an industrial PGM machine was used and emulation PGM tests were conducted. Detailed sample characterization was performed using an array of complementary techniques including white light interferometry (WLI), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), scanning transmission electron microscopy (STEM) and atom probe tomography (APT).Phenomena such as interdiffusion, oxidation, coating spallation and glass sticking on the coating were observed and are discussed in the context of optimization of the coating's performance and durability.

Precise infrared (IR) optics are core elements of infrared cameras for thermal imaging and night vision applications and can be manufactured directly or using a replicative process. For instance, precision glass molding (PGM) is a replicative manufacturing method that meets the demand of producing precise and accurate glass optics in a cost-efficient manner. However, several iterations in the PGM process are applied to compensate the induced form deviation and the index drop after molding. The finite element method (FEM) is utilized to simulate the thermomechanical process, predicting the optical properties of molded chalcogenide lenses and thus preventing costly iterations. Prior to FEM modelling, self-developed glass characterization methods for the stress and structure relaxation of chalcogenide glass IRG 26 are implemented. Additionally, a ray-tracing method is developed in this work to calculate the optical path difference (OPD) based on the mesh structure results from the FEM simulation. The developed method is validated and conducted during the production of molded lenses.