Chemical inertness of Cr–W–N coatings in glass molding

• F.c.c. Cr–W–N coatings had columnar grains with a cyclical gradient concentration.
• Orientation changed [(111) to (200)] as the W amount was increased in the coatings.
• Amorphous oxide scale formation increased oxidation resistance.
• F.c.c. Cr–W–N coatings showed chemical inertness against SiO2–B2O3–BaO-based glass.

Cr–W–N coatings with a Cr interlayer were prepared using reactive direct-current magnetron cosputtering on Si and cemented carbide substrates. To investigate the chemical inertness of Cr–W–N coatings against commercial moldable SiO2–B2O3–BaO-based glass in glass molding, thermal cycle annealing at 270 °C and 600 °C was performed in a quartz tube furnace in a 15-ppm O2–N2 atmosphere. Variations in the crystalline structure, mechanical properties, and surface roughness after various annealing durations were investigated. The results indicated that Cr37W31N32 and Cr24W46N30 coatings maintained a face-centered cubic phase and exhibited superior mechanical properties and low surface roughness after up to 1000 thermal cycles; these properties were attributed to the formation of amorphous oxide scales. By contrast, Cr8W69N23 and Cr4W82N14 coatings with a nanocrystalline W phase in the as-deposited state formed WO3 oxide scales after annealing, which negatively affected their mechanical properties and raised surface roughness values.