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In the glass molding process, the sticking reaction and fatigue wear between the glass and mold hinder the service life and functional application of the mold at the elevated temperature. To improve the chemical inertness and anti-friction properties of the mold, an amorphous carbon coating was synthesized on the tungsten carbide-cobalt (WC–8Co) substrate by magnetron sputtering. The friction behavior between the glass and carbon coating has a significant influence on the functional protection and service life of the mold. Therefore, the glass ring compression tests were conducted to measure the friction coefficient and friction force of the contact interface between the glass and amorphous carbon coating at the high temperature. Meanwhile, the detailed characterization of the amorphous carbon coating was performed to study the microstructure evolution and surface topography of the amorphous carbon coating during glass molding process by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Ramon spectroscopy, and atomic force microscope (AFM). The results showed that the amorphous carbon coating exhibited excellent thermal stability, but weak shear friction strength. The friction coefficient between the glass and coating depended on the temperature. Besides, the service life of the coating was governed by the friction force of the contact interface, processing conditions, and composition diffusion. This work provides a better understanding of the application of carbon coatings in the glass molding. [ABSTRACT FROM AUTHOR]

The Cr x W y N z coatings were synthesized on the cemented carbide (WC-8Co) by plasma-enhanced magnetron sputtering (PEMS). The detailed glass cylinder compression was tested for the molding performance of the coated molds in the precision glass molding machine (PGMM). This work examined the surface morphology evolution, elemental compositions and mechanical properties of the Cr x W y N z coatings by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), nano-indentation tester and atomic force microscope (AFM). The results showed that with the increased W content in the Cr x W y N z coatings, the nano-hardness and Young's modulus of the coatings increased, and the surface roughness of the coatings reduced. The contact zone had lower surface roughness than the non-contact zone because of inhibiting the oxidation reaction. The molded glass pressing on the surfaces of Cr 27 W 24 N 49 and Cr 18 W 28 N 54 coatings had relatively better light transmittance. Besides, the Cr x W y N z coatings (18 ≤ x ≤ 27, and 24 ≤ y ≤ 28) exhibited better oxidation resistance, chemical inertness, and surface quality during thermal-mechanical cycles, more suitable for glass molding protective coatings. The work sheds light on the preparation and application of glass molding protective coatings. • The Cr x W y N z coatings were prepared on the WC substrate by plasma-enhanced sputtering system. • The surface evolution and wear mechanism of coatings were revealed. • The optical performance of molded BK7 glass lenses was analyzed. [ABSTRACT FROM AUTHOR]

CrWN glass molding coatings were deposited by plasma enhanced magnetron sputtering (PEMS). The microstructure and thermal stability of these coatings were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscope, atomic force microscope and nanoindentation tests. The as-deposited coating exhibited an aggravated lattice expansion resulting in a constant hardness enhancement. The vacuum annealing induced surface coarsening and the spinodal decomposition of the coating accompanied by the formation of nm-sized c-CrN, c-W2N, and h-WN domains. The annealed coating with low W content had mainly a face-centered cubic (f.c.c) matrix, strain fields caused by lattice mismatch caused hardness enhancement. Following an increase in W content, the annealed coating showed a mixed face-centered cubic (f.c.c) and hexagonal close-packed (h.c.p) matrix. The large volume fraction of h-WN phases seriously weakened the coating strengthening effect and caused an obvious drop in hardness. [ABSTRACT FROM AUTHOR]

The CrWN glass molding coating was synthesized by plasma enhanced magnetron sputtering (PEMS). The effect of annealing environment (e.g., vacuum, N 2 and Air) on the microstructure and mechanical property of as-deposited coating was investigated by the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), atomic force microscope (AFM) and nanoindentation tests. Results showed that the as-deposited coating exhibited dense columnar structure consisting of multilayer CrN and W 2 N phases. The vacuum annealed coating showed similar thickness to that of as-deposited coating, but underwent visible surface coarsening because of slight oxygen erosion. The N 2 and air annealed coatings suffered from varying degree of oxidation damage accompanied by the formation of mixed WO 3 -CrWO 4 phases, which consequently resulted in severe thickness expansion and surface coarsening. The vacuum annealing induced a spinodal decomposition of supersaturated solid solution to form nm-sized CrN and W 2 N domains. Strain fields originating from the lattice mismatch eventually caused a pronounced age-hardening in the vacuum annealed coating. Whereas the N 2 and air annealed coatings showed significant mechanical degradation because these loose WO 3 -CrWO 4 oxides degraded the stable matrix structure. Our results clearly demonstrated that vacuum environment effectively suppressed the oxidation damage and mechanical degradation of glass molding coating. • The microstructure and mechanical property of the annealed coating are studied. • The vacuum annealing induces spinodal decomposition and light oxidation damage. • The N 2 and air annealing induce serious volume expansion and surface coarsening. • The vacuum annealed coating shows a pronounced age-hardening effect. • The N 2 and air annealed coatings suffer from remarkable mechanical degradation. [ABSTRACT FROM AUTHOR]