Preparation and characterization of superhard Al<scp>B</scp>₂‐type <scp>WB</scp>₂ nanocomposite coatings

Abstract

Abstract WB 2 nanocomposite coatings were synthesized by dc magnetron sputtering. The morphology, chemical composition, chemical bonding state, microstructure, hardness, and tribological properties were investigated. The columnar‐structured coatings are dense and uniform. The as‐deposited coatings were found to have a metastable AlB 2 ‐type structure as characterized by X‐ray diffraction and further confirmed by high‐resolution transmission electron microscopy. Coatings exhibit superhardness about 43.2 ± 5 GPa (taken from the plateau region) obtained by nanoindentation. In addition, the steady‐state friction coefficient µ = 0.23 and wear rate K = 6.5 × 10 −6 mm 3 N −1 m −1 were obtained under dry sliding condition in ambient environments. These characteristics indicate AlB 2 ‐type WB 2 coatings have high potential application as superhard and low wear coatings. Moreover, the AlB 2 ‐type WB 2 can hardly be prepared using the conventional powder metallurgy technology without high pressure, and this study proposes a new practical approach to prepare it.