Tribological properties of W-B-C protective coatings prepared by pulsed DC magnetron sputtering
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| Year of publication | 2017 |
| Type | Conference abstract |
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| Description | One of the many applications of thin films is the protection of tools, as appropriate coatings increase the tool’s efficiency and lifetime. Hard ceramics such as TiN, TiAlN and c-BN are the most commonly used materials for this purpose. However, these materials exhibit brittle behaviour, which facilitates the formation and spreading of cracks in the coating. A solution for this problem would be materials that are simultaneously hard and ductile. This seemingly contradictory combination of properties has been predicted in a group of materials consisting of a metal, boron and carbon. W-B-C has been predicted to have the highest toughness and ductility out of this group and will therefore be the subject of this study. Mid-frequency pulsed-DC magnetron sputtering was used to deposit W-B-C coatings in this study. The effect of coating composition and the deposition parameters on the structure, mechanical and tribological properties of the coatings is investigated. X-ray diffractometry has shown a low level of crystallinity due to high enthalpy of formation of W2BC crystalline phase. Hardness of the coatings ranged from 21.5 to 27 GPa. Main emphasis was placed on the tribological properties of the coatings. The influence of the deposition conditions on the coefficient of friction and wear was examined. Furthermore, the influence of the measuring temperature on the tribological properties of the coatings was investigated during high temperature tests. It was found that the deposition temperature and the measuring temperature had the greatest influence on the properties of the coatings. Coatings prepared at elevated temperature showed significantly lower wear and better adhesion. The coefficient of friction decreased with increasing temperature of the substrate during measurement. Coating composition 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. |
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