Mechanical properties and oxidation resistance of CrAlN/BN nanocomposite coatings prepared by reactive dc and rf cosputtering |
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| Authors: | M Nose T Kawabata T Watanuki S Ueda K Fujii K Matsuda S Ikeno |
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| Affiliation: | 1. School of Materials Science & Engineering, South China University of Technology, Guangzhou 510640, China;2. Zhongshan R&D Center for Materials Surface and Thin Films Technology of the South China University of Technology, Gent Materials Surface Technology(Guangdong) Co., Ltd, Zhongshan 528437, China;1. Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075, Singapore;2. Koszalin University of Technology, Sniadeckich 2, 75-0453 Koszalin, Poland;3. Technical University of Liberec, Studentska 1402/2, 461 17 Liberec1, Czech Republic;4. Institute of Materials Research and Engineering, 3 Research Link, 117602, Singapore;1. State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083, China;2. Zhuzhou Cemented Carbide Cutting Tools Co., LTD, Zhuzhou, Hunan 412007, China;3. Institute of Materials Science and Technology, Technische Universität Wien, Getreidemarkt 9 1060, Vienna, Austria |
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| Abstract: | CrAlN/BN nanocomposite coatings were deposited through reactive cosputtering, i.e., pulsed dc and rf sputtering, of CrAl and h-BN targets, respectively. X-ray diffraction (XRD) and selected area electron-diffraction (SAED) analysis indicated that the CrAlN/BN coating consists of very fine grains of B1 structured CrAlN phase. With an increasing BN volume fraction of over 8 vol.%, the nanocrystalline nature of the grains is revealed through a dispersion of fine grains in the CrAlN/BN coating. A cross-sectional observation using a transmission electron microscope (TEM) clarified that the coating demonstrating the highest level of hardness has a fiber-like structure consisting of grains that are ~ 20 nm in width and ~ 50 nm in length. X-ray photoelectron spectroscopy (XPS) analysis revealed that the coating consists mainly of CrAlN and h-BN phase. The indentation hardness (HIT) and effective Young's modulus (E*) of the coatings increased with the BN phase ratio, reaching a maximum value of ~ 46 and ~ 440 GPa at ~ 7 vol.% of BN phase; it then decreased moderately to ~ 40 and ~ 350 GPa at 18 vol.% of BN, respectively. Furthermore, CrAlN/BN coatings showed superior oxidation resistance compared with CrAlN coatings. After annealing at 800 °C in air for 1 h, the indentation hardness of CrAlN coatings decreased to 50% of the as-deposited hardness; in contrast, the hardness of CrAlN/BN nanocomposite coatings either stayed the same or increased, attaining a value of about 46 GPa. After annealing at 900 °C for 1 h, the hardness of all the coatings decreased to about 40%. |
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