Preparation and characterization of superhard AlB₂‐type WB₂ nanocomposite coatings

Abstract

WB2 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 AlB2‐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 mm3 N−1 m−1 were obtained under dry sliding condition in ambient environments. These characteristics indicate AlB2‐type WB2 coatings have high potential application as superhard and low wear coatings. Moreover, the AlB2‐type WB2 can hardly be prepared using the conventional powder metallurgy technology without high pressure, and this study proposes a new practical approach to prepare it.

Effect of Nitrogen Content on Microstructures and Mechanical Properties of WB2(N) Films Deposited by Reactive Magnetron Sputtering

“…The double peaks are observed for W 4f 7/2 spectra at 31.25 eV and W 4f 5/2 spectra at 33.4 eV, which are in good agreement with those of the AlB 2 -type WB 2 compounds [6] . The XPS spectra, however, cannot distinguish the compound of WN x and WB 2 in the 4f region.…”

“…4(b), the B 1s XPS spectra present a significant change with the increasing P N2 . For the pure WB 2 film, B 1s only shows a peak centered at 188.1 eV corresponding to that of the AlB 2 -type WB 2 [6] . When nitrogen is incorporated into the films, however, a weak peak of B 1s appears at the binding energy about 190.5 eV, reflecting the formation of BN phase.…”

“…Details of the deposition apparatus had been published in our previous work [6] . YG8 (WC-Co, 20 mm×20 mm×3 mm) and Si (1 0 0) wafers (25 mm×5 mm×0.4 mm) were used as substrates.…”

“…Therefore, AlB 2 -type WB 2 has been considered to be a new kind of materials for superhard and wear resistant films. In 2013 we successfully produced the AlB 2 -type WB 2 films by dc magnetron sputtering [6] , and reported the microstructure dependence of the films on deposition parameters such as substrate bias and deposition temperature [7] . The as-deposited films exhibit good mechanical and tribological properties with high hardness and low wear rate [7] .…”

“…In recent years, AlB 2 -type WB 2 has attracted extensive attention theoretically and experimentally due to its controversial structure and excellent properties [1][2][3][4][5][6][7] , including the high hardness, outstanding chemical inertness, good thermal and electrical conductivity. Therefore, AlB 2 -type WB 2 has been considered to be a new kind of materials for superhard and wear resistant films.…”