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

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 degrees C and 600 degrees C was performed in a quartz tube furnace in a 15-ppm O-2-N-2 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. (C) 2015 Elsevier B.V. All rights reserved.