Mechanical properties and oxidation behavior of W–Si–N coatings

Abstract

Monolithic and multilayered WN and W–Si–N coatings were fabricated through direct current magnetron cosputtering at substrate holder rotation speeds of 0 and 5 rpm. The mechanical properties, structural evolutions, and oxidation behaviors of the WN and W–Si–N coatings were investigated through nanoindentation, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The mechanical properties of crystalline WN coatings correlated to their textures and residual stresses. The monolithic W77N23 samples located closest to the W target exhibited a high deposition rate of 18.0 nm/min, a strong (200) texture coefficient, a high nanoindentation hardness of 32.7 GPa, a high Young's modulus of 392 GPa, and a high residual stress of −3.2 GPa. The addition of Si into the WN matrix transformed the monolithic W–Si–N coating into an X-ray amorphous phase dominated structure that comprised Si3N4, W2N, and W constituents. Ion bombardment caused the formation of multilayered W78N22 samples with high residual stress and mechanical properties. The mechanical properties and residual stresses of the multilayered W–Si–N coatings decreased due to the preferential formation of Si3N4. By contrast, oxidation resistance was improved by adding Si content higher than 24 at.% with annealing at 600 °C in a 1% O2–99% Ar atmosphere.