Microstructure and Properties of TiAlN/a-C Nanocomposite Coatings Prepared by Reactive Sputtering

Abstract

TiAlN/a-C nano-composite coatings were synthesized by a reactive co-sputtering process to investigate the effects of sputtering conditions on the microstructure and mechanical properties. Coating films were deposited on square plates of Si and high speed steel (ANSI M2) by the cosputtering of TiAl (pulsed-d.c. sputtering) and C (d.c. sputtering) targets using a ''Facing Target-type Sputtering'' system at an atmosphere with a mixture of Ar and N 2 but without hydrocarbon gas. The structure of the coatings was investigated by means of XRD, XPS and HRTEM with GIF (Gatan Imaging Filter). Mechanical properties of coating films were measured by a submicron indentation system. Though TiAlN and a-C coatings showed hardness of about 32 and about 10 GPa, respectively, TiAlN/a-C coatings containing 4.6 at% of C showed higher hardness of 43 GPa. The energy filter images depicted that a change of contrast in the zero-loss image corresponded to nanometer-size of Ti agglomerates in Ti map. C1s spectrum in XPS analysis revealed that carbon in the coatings was bounded as C-C and C-N without bonding of Ti-C or Al-C. These results indicated that the TiAlN/a-C nano-composite coatings consisted of complicated mixture of nanocrystalline Ti-Al-N phase and a-C phase (including C-N bonding).

Structure characterization and tribological study of magnetron sputtered nanocomposite nc-TiAlV(N,C)/a-C coatings

“…The column boundary area is also completely amorphous. Thus, according to the definition described in literature [9][10][11][12][13][14][15][19][20][21][22], the TiAlVCN coatings can be termed as nanocomposites of nc-TiAlV(N,C)/a-C, namely nano-crystalline TiAlV(N,C) and amorphous carbon.…”

“…Carbon is known to have multiple sp, sp 2 and sp 3 binding characteristic, and thereafter may have a series of different condensed structures having diverse physical and mechanical properties. Considering the fact that carbon coatings, mostly diamond like carbon (DLC), have environment-dependent low friction coefficient, more recently the research interests have been focused in the growth of carbon-containing TMN coatings, such as Ti-N-C [18][19][20][21], Ti-Al-N-C [22][23][24], Zr-N-C [25] and Ti-Si-C-N [26][27], which show both high hardness and environment-dependent low friction. It has been found that a transition from columnar nitride crystallites to a dual-phase structure occurs as a result of the precipitation of free carbon in the coating structure.…”

“…It is known that many nitride coatings grown by vapour deposition shown columnar structure, where the relationship between the deposition conditions and the coating morphology has been established in several models [28]. When carbon is incorporated, it may partially dissolve in the nitride lattice depending on its solutibility, whereas the rest carbon precipitates as a secondary free-carbon phase to form the nanocomposite structure [18][19][20][21][22][23][24][25][26][27]. Therefore, the coating growth involves redistribution or segregation of the impinging atoms/ions on the growth front.…”

Surface Morphology and Tribological Properties of Nanoscale (Ti, Al, Si, C)N Multilayer Coatings Deposited by Reactive Magnetron Sputtering

“…Several studies have indicated that multilayer coatings can exhibit high hardness and fracture resistance with low compressive stress through control of the parameters of the layered structure [5,17]. The tribological behavior of carbon-based thin films is also strongly influenced by their chemical composition, polycrystalline structure, and surface morphology [18].…”

“…Films of diamond-like carbon (DLC) and transition-metal and carbon nitrides (CNx), such as titanium aluminum nitride (TiAlN) and CNx are the most widely used coatings for tribological applications, such as for forming and cutting tools. Thus, it is desirable to improve the tribological properties of these films to enhance their performance in tool applications [5].…”