Publication details

Tribological properties of WBC protective coatings prepared by magnetron sputtering



Year of publication 2018
Type Conference abstract
MU Faculty or unit

Faculty of Science

Description W2BC is a promising new material for fracture resistant protective coatings due to its high hardness and moderate ductility as predicted per ab initio calculations [1]. Three sets of W-B-C coatings with stoichiometry close to W2BC were deposited using mid-frequency pulsed-DC magnetron sputtering with differing deposition parameters. The effect of the coating composition and the deposition parameters on the structure and mechanical properties of the coatings was investigated. The lack of sharp peaks in the X-ray diffractogram indicated a prevalently amorphous nature of the coatings. The hardness of the prepared coatings ranged from 21.5 to 27 GPa. Coatings prepared at elevated temperature generally exhibited higher hardness than that of the coatings prepared at ambient temperature. The main focus of this work was placed on the tribological study of these coatings. The influence of the deposition conditions on the coefficient of friction and wear was examined. The coefficient of friction increased with the increasing amount of W and decreasing amount of B for coatings prepared at ambient as well as elevated temperature. Coatings prepared at elevated temperature have shown a significantly lower wear when a 100Cr6 steel counterpart ball was used, compared to the harder ceramic Si3N4 ball. Furthermore, the influence of the measuring temperature on the tribological properties of the coatings was investigated during high temperature tests. The coefficient of friction decreased when the temperature of the substrate during measurement reached 500 – 600°C. XRD measurements after high temperature tests have shown that this decrease was due to the formation of W-O Magnéli phases, which acted as a solid-state lubricant. This self-lubricating property could be useful in tribological applications without cooling or additional lubrication where high working temperatures are common.
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