Influence of carbon incorporation on microstructure and properties of titanium diboride coatings deposited by combining ion beam with magnetron sputtering

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Titanium diboride (TiB2) coatings with carbon incorporation were deposited by a hybrid deposition method consisted of an ion beam and a pulsed magnetron sputtering using a gas mixture of acetylene (C2H2) and argon (Ar). The influence of carbon incorporation on composition, microstructure, mechanical properties and high temperature oxidation behavior of the TiB2 coatings was investigated using scanning electron micrograph, X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, nanoindentation and Thermogravimetric analyzer as a function of the added carbon content. The results indicate that the carbon content of the coatings increases from 0 to 24.0 at. % as the C2H2 flow fraction increases from 0 to 10% in the C2H2/Ar gas mixture. It is found that the incorporated carbon atoms tend to form B–C bonds and exist mainly as an amorphous B–C phase in the coatings when the addition content of the carbon is relatively high. The amorphous B–C phases can refine the TiB2 grains and encapsulate the TiB2 grains to build nanocomposite structures, significantly improving the mechanical properties of the TiB2 coatings. In addition, the amorphous phases can make the TiB2 grains isolate oxygen and improve the oxidation resistance of the TiB2 coatings.