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Influence of the interlayer material selection for PtIr-coatings on the degradation mechanisms for use in Precision Glass Molding

: Friedrichs, Marcel; Dambon, Olaf; Bernhardt, Frank; Dong, Zhen; Klocke, Fritz

Bobzin, K.:
12th International Conference THe "A" Coatings 2016 : Institute of Production Engineering and Machine Tools Hannover, March 31st-April 1st, 2016; Proceedings
Garbsen: TEWISS, 2016 (Berichte aus dem IFW 2016, 3)
ISBN: 978-3-95900-072-7
ISBN: 3-95900-072-3
International Conference THe "A" Coatings <12, 2016, Hannover>
Conference Paper
Fraunhofer IPT ()
Beschichtung; Oberflächentechnik; Optik; Umformtechnik; Werkzeug- und Formenbau; Werkzeugverschleiß; precision glass molding; protective coatings; interlayers; degradation mechanism; heating tests

Thermo-chemical and thermo-mechanical loads act on molding tools during several hundred up to thousand pressing cycles of Precision Glass Molding (PGM). Mainly precious metal physical vapor deposition (PVD) coatings such as platinum-iridium (PtIr) are used to increase the lifetime of molding tools. Using a thin interlayer, the protective coating adheres to the molding tool. Furthermore, the interlayer should serve as a diffusion barrier between molding tool and protective coating. The presented work investigates thermo-chemical and thermo-mechanical degradation mechanisms of PtIr-coatings by duration and cyclic heating tests. The influence of different metallic and ceramic interlayer materials on the degradation mechanisms was examined. Compositional changes at the surface-near region of PtIr-coatings and interlayers were studied after heating tests. Heating tests were executed with and without glass contact. Subsequent analyses of the samples were performed by light microscopy, white light interferometry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Different wear zones and degradation mechanisms as diffusion, oxidation, adhesion and flaking off could be verified. Using metallic interlayers such as chromium or tantalum, minimal degradation and maximum stability under thermal load were observed.