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Design and Characterization of Novel Wear ResistantMultilayer CVD Coatings with Improved AdhesionBetween Al2O3 and Ti(C,N)**

ION

By Jose Garcia*, Reinhard Pitonak, Ronald Weißenbacher, Arno Kopf, Flavio Soldera,

Sebastian Suarez, Federico Miguel, Haroldo Pinto, Aleksander Kostka and Frank Mucklich

Multilayer CVD coatings for high speed cutting applications were designed to achieve high wear andheat resistance during machining of steel alloys. In this work the microstructure and cuttingperformance of these novel multilayer CVD coatings are investigated and compared with standardCVD multilayer coatings. 3D-FIB tomography is used to characterize the microstructure of the layers,especially the transition between the Ti(C,N) and the Al2O3 layer. The 3D reconstruction of the surfaceof the Ti(C,N) layer shows the formation of protruded Ti(C,N) grains with a very particulararchitecture, which penetrate into the Al2O3 top-layer, providing a mechanical anchoring betweenboth layers. Cemented carbides coated with the novel CVD multilayer present reduced crater and flankwear as well as improved adherence between the Al2O3 top-layer and the Ti(C,N) layer leading to adramatic improvement of cutting performance.

[*] Dr. J. GarciaHelmholtz Zentrum Berlin fur Materialien und EnergieGmbH, Hahn-Meitner-Platz 1,D-14109 Berlin, GermanyE-mail: jose.garcia@helmholtz-berlin.de

Dr. R. Pitonak, Dr. R. Weißenbacher, Dr. A. KopfBoehlerit GmbH & Co. KG, PO Box 85, A-8605 Kapfenberg,Austria

Dr. F. Soldera, Dr. S. Suarez, Dr. F. Miguel,Prof. Dr. F. MucklichUniversitat des Saarlandes, Functional Materials, CampusD3.3, D-66123 Saarbrucken, Germany

Prof. Dr. H. PintoUniversidade de Sao Paulo, Dep. Engenharia de Materiais,Aeronautica e Automobilıstica, 13566-590 Sao Carlos, Brazil

Dr. A. KostkaMax Planck Institute fur Eisenforschung GmbH, Max-Planck-Str. 1, D-40237 Dusseldorf, Germany

[**] The authors (J. Garcia and H. Pinto) thank the financial supportof the DFG project 444Bra-113/25/0-1 to carry out part of thiswork. J. Garcia thanks financial support of joint research groupMicrostructural Analysis (Helmholtz-Zentrum Berlin furMaterialien und Energie GmbH/Ruhr Universitat Bochum).S. Suarez and F. Miguel thank financial support of the GermanAcademic Exchange Service (DAAD).

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Cemented carbide indexable inserts are the most wide-

spread tools for machining of metal alloys.[1] In order to

improve the wear resistance of the tools, the indexable inserts

are coated with wear resistant thin films. Depending on the

coating type and application, the thin films are produced by

chemical vapor deposition (CVD) or physical vapor deposi-

tion (PVD).[2] Thin coatings produced by the PVD method are

commonly used in milling applications. For metal turning

cutting applications, multilayer coatings made by CVD are

state-of-art. Typical wear resistant materials deposited by

CVD are TiN, Ti(C,N), Zr(C,N), and Al2O3. The multilayer

sequence of the coating aims to provide wear, corrosion, and

heat resistance.[3] In general, Ti(C,N) enhances the wear

resistance, due to the intrinsic properties of Ti(C,N) com-

pounds.[4] As a result of ever increasing cutting speeds

(>250 m min�1), high temperatures at the interface tool–chip

material are reached. Due to the low thermal conductivity of

Al2O3,[5] thin layers of alumina are used as thermal barriers in

order to protect the cemented carbide substrates from the

high temperatures at the cutting edge. So, when designing a

coating, sequences of wear resistant and heat resistant layers

are produced. A typical coating for high speed metal cutting

consists of a multilayer of TiN, Ti(C,N), and Al2O3 layers. The

adhesion between the Al2O3 and the Ti(C,N) layer is always a

critical point in coatings for metal cutting applications. Lack

of adhesion of the Al2O3 layer to the Ti(C,N) layer reduces

considerably the wear resistance of the tool. Previous

investigations in order to improve the adhesion between

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the Ti(C,N) and the Al2O3 coating propose the use of an

intermediate layer made of Ti(C,N,O).[6]

In a recent development novel Ti(C,N) coatings with a

gradient in grain morphology and composition were pro-

duced by modifying the deposition conditions during CVD.[7]

The wear resistance is provided by a modified microstructure

of the Ti(C,N) phase.[8] In ref. [8] the microstructure of the

novel Ti(C,N) layer produced after[9] was investigated. It was

found that this novel Ti(C,N) layer is a nitrogen-rich layer with

an overall C/N ratio of 0.16:0.84. The Ti(C,N) phase presents a

composite structure, showing the presence of two Ti(C,N)

crystallites co-existing in the layer (star-shape and lenticular-

like). These crystallites protrude from the surface of the

Ti(C,N) layer, giving a topographic rough-effect to the coating

layer. These protruded crystallites may improve the adhesion

of subsequent coating layers, such as Al2O3 layers, to

the Ti(C,N) layer, due to mechanical anchoring. Within the

method described in ref. [9] a tailored transition from the

Ti(C,N) into the k-Al2O3 without the production of inter-

mediate layers is obtained.

In this work, the microstructure and cutting performance

of a novel multilayer system containing, among others, a

graded Ti(C,N) layer with protruded crystallites is investi-

gated; in particular, the spatial architecture of the interface

between the Ti(C,N) and the k-Al2O3 layer by 3D-FIB

tomography. High speed cutting tests of cemented carbides

coated with the novel multilayer system are carried out under

severe conditions and compared with cemented carbides

coated with conventional multilayer coatings produced by

state-of-art methods.

Experimental

Multilayer coatings were prepared in an industrial hot wall

CVD reactor at temperatures between 900 and 1050 8C and

pressures between 70 and 150 mbar. The novel multilayer

coating consists of five thin layers: TiN, two Ti(C,N) layers

(produced by medium temperature (MT), and high tempera-

ture (HT) CVD), k-Al2O3 and a thin TiN top-layer. In

particular, the production of the MT–Ti(C,N) and the

HT–Ti(C,N) layer was carried out following these chemical

reactions:

MT–Ti(C,N):

TiCl4ðgÞ þ CH3CNðgÞ þ 21=2H2ðgÞ ¼> TiðCx;NyÞðsÞþ CH4ðgÞ þ 4HClðgÞ

(1)

where (s) means solid phase and (g) gas phase.

The reaction takes place at a temperature range between

750 and 950 8C; for this reason the process is called

‘‘moderate’’ or ‘‘medium’’ CVD process and in the following

it will be referred as MT–CVD.

HT–Ti(C,N):

TiCl4ðgÞ þ xCH4ðgÞ þ1

2ð1� xÞN2ðgÞ

þ 2ð1� xÞH2ðgÞ ¼> TiCxN1�xðsÞ þ 4HClðgÞ(2)

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The reaction takes place at temperatures between 950 and

1050 8C and this process is called CVD or ‘‘high’’ temperature

CVD, and in the following it will be referred as HT–CVD. In

this study all HT–CVD Ti(C,N) layers were produced

following the modified CVD method described in ref. [7].

The mutilayer coating was analyzed by light microscopy

on polished cross-section of samples. SEM analyses were

performed in a Jeol JSM 6500F equipped with an EDX. The

results of TEM were carried out using a Jeol 2200 FS operating

at 200 kV. TEM specimens were prepared using focused ion

beam (FIB) system Jeol JEM-9320 operating at 30 kV. FIB

tomography was performed in a dual beam system (FIB

combined with SEM, FEI Strata 235 DB). The series of images

for tomography were acquired with the software Slice& View

(FEI). The processing and 3D reconstruction of the serial

sectioning images was done with A4i and AMIRA software,

while for the quantitative analysis MAVI was employed. A Pt

layer was deposited on top of the region of interest (ROI) in

order to protect the material, improve the quality of the

FIB-cuts and provide a sharp interface between the sample

surface and the Pt layer, which would be later used for slice

alignment. The Pt layer was deposited by ion beam induced

deposition (IBID) in situ in the Dual Beam System SEM/FIB.

Cutting tests were carried out in continuous turning of

42CrMo4 steel under high speed cutting conditions (cutting

speed¼ 280 m min�1, depth of cut¼ 1.5 mm, feed¼ 0.28 mm

U�1, and continuous cooling). The response to flank wear and

crater wear was measured before plastic deformation takes

place. Worn interfaces were analyzed on cross-sections of

indexable inserts after complete damage of the tools.

Microstructure of Coating Multilayer Systems

The multilayer coating arrangement of the novel multilayer

coating is shown in Figure 1a. The coating is made of five thin

layers, with the following sequence: a TiN thin layer of 0.5 mm

which ensures a good adherence to the cemented carbide

substrate, a MT–Ti(C,N) of 5 mm thickness, a HT–Ti(C,N) of

5 mm, a 4 mm k-Al2O3, and a 0.5 mm TiN top-layer. A tough

graded surface zone was produced in the cemented carbide

part, in order to impart toughness to the indexable insert

cutting tool [10].

The HT–Ti(C,N) layer shows dark-orange colored and

light-orange colored regions. It is well-known that the color of

Ti(C,N) changes from light yellow for TiN into dark gray for

TiC. From this observation it can be assumed that the

orange-colored HT–Ti(C,N) corresponds to a nitrogen-rich

carbonitride. This hypothesis was previously verified by X-ray

diffraction investigations, determining a C/N ratio of 0.16:0.84

for the HT–Ti(C,N) [8]. For sake of comparison, a state-of-art

CVD multilayer coating is also presented [Fig. 1(b)]. A

different arrangement of thin films is observed, consisting on

MT–TiCN, TiOx, k-Al2O3, and TiN top-layer. For increasing

the cutting performance, the TiN top-layer was removed in

both multilayers by microblasting [11].

In Figure 2a TEM micrograph of the novel multilayer

coating system is shown. The TiN, MT–CVD, and HT–CVD as

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Fig. 1. Light microscopy pictures of CVD multilayer coating. a) the novel multilayer consists of a TiN/MT–Ti(C,N)/HT–Ti(C,N)/k-Al2O3/TiN thin film sequence; b) state-of-art coating with MT-Ti(C,N)/TiOx/k-Al2O3/TiN multilayer.

Fig. 2. TEM micrograph of novel multilayer system showing sequence of layers.

well as the k-Al2O3 layer are observed. The first carbonitride

layer (MT–TiCN) presents the typical columnar structure of

CVD MT carbonitrides, with columns that grow throughout

the coating.[12]

The next carbonitride layer (HT–TiCN) does not show

the typical equiaxed crystallite shape of HT–CVD Ti(C,N)

Fig. 3. SEM (top view) of novel HT–Ti(C,N) layer showing different morphologies for Ti(C,N) crystallites(star-shaped and lenticular-like crystallites). Light microscopy image showing the interface between theHT–Ti(C,N) layer and the k-Al2O3 layer, with Ti(C,N) crystallites penetrating into the k-Al2O3 top-layer.

coatings [12]. A mixture of columnar grains

and equiaxed grains can be observed on

this layer. Also a gradient of crystallite size

in the coating growth direction from

the interface with the MT–Ti(C,N) into the

interface with the k-Al2O3 is clearly seen.

Some HT–Ti(C,N) grains penetrate into the

alumina layer. In the top-layer corresponding

to k-Al2O3, columnar grains are clearly

visible. No pores are visible in the alumina

phase.

In Figure 3a a SEM picture (top view)

and an optical micrograph (cross-section,

sample preparation with an angle of 208 for

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enlargement of the observed area) of the

interface between the HT–Ti(C,N) and the

k-Al2O3 layer is shown. In the interface

between the HT–Ti(C,N) and the k-Al2O3

layer, a needle-like structure is observed,

where protruded crystallites of the

HT–Ti(C,N) penetrate in the k-Al2O3

top-layer.

The formation of these protruded crystal-

lites has been previously discussed by

considering the nucleation and growth of

the Ti(C,N) crystallites during the modified

CVD manufacturing process.[14]

3D-FIB Tomography of the Interface Transition Ti(C,N)–Al2O3

The FIB-tomography technique was used in order to

investigate the 3D arrangement of the grains in the transition

between the HT–Ti(C,N) and the k-Al2O3 top-layer.

Series of cross-sections with FIB and images with FE–SEM

were performed perpendicular to the layers (Fig. 4). The

description of the tomography process can be found else-

where [14]. A total volume of 22� 23� 12 mm3, with a distance

of 50 nm between cuts, was analyzed. Phases and some grains

were segmented using the software Amira1. As displayed in

Fig. 4(a), the images from the slices were affected in some

cases by a strong curtaining effect, which would mainly

interfere with the HT–Ti(C,N) grains segmentation. To

overcome this issue, periodic and symmetric patterns were

removed from the frequency spectrum after applying the fast

fourier transform (FFT) to each slice with the software A4i.

Afterwards, with the Inverse FFT, the spectrums were

reversed to the original images but with almost no remaining

traces of the curtaining effect, as shown in Fig. 4b. Given

the high contrast of the WC phase in the cemented carbide

substrate and the k-Al2O3 top layer respect to the Ti(C,N) the

segmentation of these phases could be performed completely

by gray scale thresholds Fig. 4(c). The Ti(C,N) layer was the

most problematic area in terms of segmentation capability.

Despite the many grains present, being a single phase material

resulted in a very low contrast among them. Individualization

of complete grains required a meticulous visual inspection

through the slices because, even when a relatively good

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Fig. 4. FIB/SEM slices of novel multilayer system: a) original slice with strong curtaining effect, b) curtainingeffect removed after FFT spectrum of frequencies modification, c) segmented cemented carbide and k-Al2O3 toplayer, d) segmented HT–Ti(C,N) grains.

Fig. 5. 3D-FIB tomography of novel multilayer system, showing WC grains ofcemented carbide, the morphology and distribution of selected HT–Ti(C,N) grains,and the k-Al2O3 top-surface layer.

contrast was devised, it may happens, that in some slices the

contrast between the grain and the surrounding is hard to

distinguish. This makes the grain unsuitable for analysis. As

for the suitable ones, each of them had to be differently

processed: smoothing, edge detection and shading correction

filters, contrast/brightness manipulation, and morphological

operations were selectively employed to enhance the visua-

lization of each grain, leading to their manual segmentation

[Fig. 4(d)].

The final 3D reconstruction is shown in Figure 5. The dark

red substrate represents the WC grains of the cemented

carbide and the purple top-layer is the alumina coating.

Between them, several HT–Ti(C,N) grains are reconstructed in

different colors. The Ti(C,N) grains present a particular

architecture, which is very different to the well-known

equiaxed grains of HT–CVD coatings or the columnar grains

of MT–CVD Ti(C,N) layers [12]. In previous investigations [13] it

was determined by XRD that HT–Ti(C,N) layers produced by

the modified CVD method present a preferred texture in the

direction h110i. This texture corresponds with the observed

h110i texture for star-shaped crystallites on TiN coatings [15].

Nevertheless, some other crystallites with a lenticular-like

morphology having a h211i texture are present in the layer

microstructure, providing a mixed-morphology to the layer.

In ref. [13] it was concluded that during the modified CVD

4 http://www.aem-journal.com � 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

deposition star-shaped Ti(C,N) grains with

h110i texture form in the HT–Ti(C,N) layer

and that they prevail in the competitive

growth with the lenticular-like crystallites,

which form at higher deposition tempera-

tures. From the 3D reconstruction, some

preferred crystallite-growth in a direction

perpendicular to the substrate is observed.

However, the Ti(C,N) crystallites present a

non-typical morphology, with some grains

showing screw-like type morphologies. Here

it may be pointed out, that the reconstruction

intended to follow the pattern of a particular

grain for the 3D representation of one single

Ti(C,N) grain.

In Figure 6, the top oxide layer was

removed for a better visualization of the

reconstructed Ti(C,N) grains. The protruded

grains produce a rough and irregular

transition surface with the k-Al2O3 layer,

which provides an interlocking effect

between them and the k-Al2O3 layer,

anchoring it.

Turning Cutting Tests

The cutting response of the novel multi-

layer coating was tested in turning of

42CrMo4 steel. It is well-known that the

tribological phenomenon at the tool–chip

interface controls chip formation and tool

wear [16]. Most common wear mechanisms

for cemented carbide indexable inserts in steel turning

applications are flank wear, crater wear, and plastic

deformation. Flank wear is produced due to the contact

between the cutting material and the edge of the indexable

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Fig. 6. 3D-FIB tomography reconstruction of HT–Ti(C,N) grains showing the spatialdistribution of some grains as well as an interlocking effect. Note: the k-Al2O3 top-layerwas removed for better visualization of the interface between the Ti(C,N) and thek-Al2O3 layer.

Fig. 7. Scheme of main wear mechanisms at the tip of indexable cutting inserts, whichlead to plastic deformation and end of tool-life. Cutting test results of investigatedmultilayer systems. The novel multilayer containing the novel HT–CVD Ti(C,N)(curve C) shows an improvement between 50 and 80% in cutting performance comparedto state-of-art multilayers (curves A and B).

insert. Crater wear is produced by abrasion of the coating

and, after the coating is worn, of the cemented carbide body

itself, due to flow of chips during metal cutting. Plastic

deformation is the result of the combination of the HT

reached during cutting (reported to be almost 900–1000 8C)

and the increasing tangential force at the cutting edge due to

the contact between the cutting material and the indexable

insert. As metal cutting increases, the tribological conditions

at the tool–chip interface change from sliding to seizure (i.e.,

solid weld between chip and tool). Once seizure sets in,

thermoplastic shear occurs raising the local temperature at

the tool–chip contact and diffusion mechanisms take place,

leading to enhanced crater wear. Crater wear accelerates the

plastic deformation due to a reduction of the effective wear

resistant area and hence a reduction of the strengthening of

the cutting edge. Therefore, a primary goal to increase the

cutting performance of the inserts is to delay crater wear

formation.

Fig. 8. Light microscopy images showing cross-sections of the cutting edge of indexable inserts at the end tool life.The selected area (white box) shows the adhesion of the k-Al2O3 to the Ti(C,N) coating layer at the end tool life.The k-Al2O3 detaches of the MT–Ti(C,N) (a), whereas the interlocking effect of the novel HT–Ti(C,N) enhancesthe adhesion of the k-Al2O3 (b).

Figure 7 shows the results of cutting tests.

A reduced flank wear and crater formation

was measured for the novel multilayer

system compared to the state-of-art

multilayers. This dramatic improvement

may be explained by the particular structure

of the novel HT–Ti(C,N) layer as well

as the adherence-effect at the transition

between the Ti(C,N) layer and the k-Al2O3

top-layer.

The presence of different types of crystals

in the HT–Ti(C,N) layer (star-shape and

lenticular-like grains) compared with the

MT–Ti(C,N) (columnar grains) may act as

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barriers for dislocations propagation. On the other hand, the

nitrogen-rich Ti(C0.2N0.8) layer may improve the crater wear

resistance by forming oxide layers on the crystal surface [17],

which are not soluble in hot steel chips. Subramanian et al. [18]

demonstrated that by choosing a coating layer with the least

thermodynamic potential for dissolution into the workpiece

chip, the amount of dissolution wear is reduced drastically,

leading to enhanced crater resistance. The equilibrium

solubility products of nitrides such as TiN, ZrN, etc. are

several orders of magnitude lower than that of WC in steel in

the temperature range of 1000 8C, making these coatings more

suitable to resist dissolution wear.

Another positive effect of the crystallite morphology of the

novel HT–CVD coating is the formation of the needle-like

transition (Figs. 3, 5, and 6), which results in a better adhesion

of the k-Al2O3 top-layer.

In Figure 8a a cross-section of the cutting edge of the

indexable insert with the novel multilayer at the end tool

life is shown. A perfect adherence of k-Al2O3 to the Ti(C,N) in

the novel multilayer system is achieved, even though the tip

of the insert is completely damaged. Contrary, the state-of-art

coating system shows a detached k-Al2O3 layer for the

same cutting conditions, as seen in [Fig. 8(b)]. It can be then

concluded that, both the combination of the particular

morphology of the novel HT–Ti(C,N) layer and the improved

adhesion of the heat resistant k-Al2O3 layer are then

responsible for the enhanced cutting performance of the

novel multilayer systems.

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Conclusions

In this work a novel multilayer coating system was

characterized regarding its microstructure and cutting

performance in turning of steel. The microstructure at the

interface between the Ti(C,N) and the k-Al2O3 layer was

investigated by 3D-FIB tomography. The cutting response of

the multilayer was compared with a conventional state-of-art

multilayer system. Conclusions can be summarized as

follows:

� T

6

he 3D reconstruction shows Ti(C,N) with a very particular

architecture, different from conventional equiaxed or

columnar grains of CVD Ti(C,N) coatings. From the

3D-reconstruction, some grains showing screw-like type

morphologies with a preferred growth perpendicular to

the substrate are observed.

� R

esults of 3D-FIB tomography confirms that Ti(C,N) crys-

tallites at the interface between the HT–Ti(C,N) and the

k-Al2O3 layer present a needle-like structure. The Ti(C,N)

protruded crystallites penetrate into the k-Al2O3 top-layer,

providing mechanical anchoring between the layers.

� In

vestigations on cross-sections of worn indexable inserts

show improved adherence between the k-Al2O3 top-layer

and the Ti(C,N) layer – due to the needle-like transition –

compared with conventional Ti(C,N)-k-Al2O3 systems.

� C

emented carbides coated with the novel CVD multilayer

present reduced crater and flank wear compared to state-

of-art indexable inserts, leading to enhanced cutting

performances. Reasons for the dramatic improvement of

the performance (up to 80%) are the improved wear resist-

ance of the novel HT–Ti(C,N) layer and the better adhesion

of the k-Al2O3 heat-resistant layer, both retarding crater

wear and plastic deformation.

Received: March 30, 2010

Final Version: May 20, 2010

Published online: XX XX XX

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n and Characterization of Novel Wear Resistant Multilayer .

[1] K. J. A. Brookes, World Directory and Handbook of Hard-

metals and Hard Materials, 5th Edn, East Bamet, UK

International Carbide Data, 1992.

[2] H. O. Pierson, Handbook of Chemical Vapour Deposition,

Noyes Publication/William Andrew Publishing LLC,

Norwich, New York, USA 1999.

[3] S. Ruppi, M. Halvarsson, Thin Solid Films 1999, 353,

182.

[4] W. Lengauer, in: Handbook of Ceramic Hard Materials,

Vol. 1 (Ed: R. Riedel), Wiley-VCH, 2000 p. 202–252.

[5] D. G. Gahill, S. M. Lee, T. I. Selander, J. Appl. Phys. 1998,

83(11), 5783.

[6] H. Halvarsson, S. Vuorinen, Surf. Coat. Technol. 1993,

56, 165.

[7] R. Pitonak, J. Garcia, R. Weissenbacher, K. Udier, Aus-

trian Patent AT503050 B1 2007.

[8] R. Pitonak, J. Garcia, A. Koepf, R. Weissenbacher, Proc.

15. IFHTSE and SMT 20, 2006, Vol. SE-CVD, CD-Version,

Austria

[9] R. Pitonak, J. Garcia, R. Weissenbacher, K. Udier, US

Patent US2009226758 A1 2009.

[10] C. Barbatti, J. Garcia, F. Sket, A. Kostka, A. Pyzalla, Int. J.

Surf. Coat. Technol. 2008, 202, 5962.

[11] C. Barbatti, J. Garcia, H. Pinto, A. Kostka, A. Di Prinzio,

M. Staia, R. Pitonak, A. Pyzalla, Int. J. Surf. Coat. Technol.

2009, 203, 3708.

[12] A. Larsson, S. Ruppi, Thin Solid Films 2002, 402, 203.

[13] R. Pitonak, J. Garcia, R. Weissenbacher, A. Koepf, sub-

mitted to Int. J. Surf. Coat. Technol. 2010.

[14] A. Velichko, F. Mucklich, Adv. Solid State Phys. 2009, 480, 331.

[15] H.-E. Cheng, M.-H. Hon, J. Appl. Phys. 1996, 79(10), 8047.

[16] H. O. Gedonke, S. V. Subramanian, Surf. Coat. Technol.

2002, 149, 151.

[17] H.-Y. Chen, F.-H. Lu, J. Vac. Sci. Technol. A 2005, 23(4),

1006.

[18] S. V. Subramanian, S. S. Ingle, D. A. R. Kay, Surf. Coat.

Technol. 1993, 61, 293.

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