Phase configuration, nanostructure, and mechanical behaviors in Ti-B-C-N thin films
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Junping Wang Science School, Beijing University of Civil Engineering and Architecture, Beijing 100044, People’s Republic of China
Yaogen Shen Department of Manufacturing Engineering & Engineering Management, City University of Hong Kong, Kowloon, Hong Kong
Dongbai Sun National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083, People’s Republic of China (Received 8 July 2008; accepted 19 November 2008)
A series of Ti-B-C-N thin films were deposited on Si (100) at 500 C by incorporation of different amounts of N into Ti-B-C using reactive unbalanced dc magnetron sputtering in an Ar-N2 gas mixture. The effect of N content on phase configuration, nanostructure evolution, and mechanical behaviors of Ti-B-C-N thin films was studied by x-ray diffraction, x-ray photoelectron spectroscopy, Raman spectroscopy, highresolution transmission electron microscopy, and microindentation. It was found that the pure Ti-B-C was two-phased quasi-amorphous thin films comprising TiCx and TiB2. Incorporation of a small amount of N not only dissolved into TiCx but also promoted growth of TiCx nano-grains. As a result, nanocomposite thin films of nanocrystalline (nc-) TiCx(Ny) (x + y < 1) embedded into amorphous (a-) TiB2 were observed until nitrogen fully filled all carbon vacancy lattice (at that time x + y = 1). Additional increase of N content promoted formation of a-BN at the cost of TiB2, which produced nanocomposite thin films of nc-Ti(Cx,N1-x) embedded into a-(TiB2, BN). Formation of BN also decreased nanocrystalline size. Both microhardness and elastic modulus values were increased with an increase of N content and got their maximums at nanocomposite thin films consisting of nc-Ti(Cx,N1-x) and a-TiB2. Both values were decreased after formation of BN. Residual compressive stress value was successively decreased with an increase of N content. Enhancement of hardness was attributed to formation of nanocomposite structure and solid solution hardening.
I. INTRODUCTION
More recently, quaternary systematical nanocomposite hard thin films have received a lot of attention because they combine good properties of different ternary systems through nanostructure design.1 Ti-C-N films have been extensively used as industry film materials, especially for various tools, because of its better mechanical properties and wear characterizations,2–4 whereas Ti-B-N thin films showed superhard hardness value and high thermal stability.5,6 Thus, good nanostructural and mechanical properties are expected to be obtained in Ti-Ba)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0310
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J. Mater. Res., Vol. 24, No. 8, Aug 2009
C-N thin films.7,8 However, there were still several problems that needed to be solved. First, incorporation of B or C into TiN produced nanocomposite Ti-B-N or Ti-C-N thin films, respectively, in which microstructures usually exhibited nanocomposites of nanocrystalline phase less than 10 nm embedded into amorphous matrices.2,
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