deposition and characterisation of multilayered pvd tin/crn coatings on cemented carbide

Surface and Coatings Technology 116–119 (1999) 108–115www.elsevier.nl/locate/surfcoat

Deposition and characterisation of multilayered PVD TiN/CrNcoatings on cemented carbide

Maria Nordin *, Mats LarssonUppsala University, Department and Division of Materials Science, Box 534, S-751 21 Uppsala, Sweden

Abstract

In laboratory as well as in application tests, multilayered PVD coatings have shown enhanced mechanical and tribologicalproperties as compared to today’s single layered PVD coatings. A coating which has shown very interesting properties, such ashigh temperature stability and high fracture toughness, is multilayered PVD TiN/CrN. Our knowledge about the connectionbetween the growth dynamics and the properties of this coating is, however, rather poor. Therefore, to further develop andoptimise this coating, it is necessary to study the correlations between on the one hand the growth process, and on the other themicrostructure, composition and mechanical properties of the coating.

In this work growth rate, morphology, microstructure, chemical and phase composition, together with coating hardness,Young’s modulus and fracture toughness of different multilayered PVD TiN/CrN coatings have been evaluated. All coatings havebeen deposited on cemented carbide substrates using a combination of reactive electron beam evaporation (Ti) and reactive d.c.magnetron sputtering (Cr). The influence of lamella thickness and different deposition parameters: substrate bias, magnetronsputtering power and nitrogen flow, on the above mentioned characteristics has been examined. In addition to the multilayeredTiN/CrN coatings, homogeneous TiN and CrN have been included and compared.

The investigation showed that a dense, fully cubic NaCl phase, multilayered PVD TiN/CrN coating with high fracturetoughness can be deposited provided that the lamella thickness is kept less than 14 nm and 5 nm of TiN and CrN respectively.Thin lamellae seem to inhibit transformation from growth of the cubic NaCl phase to new phases, e.g. hexagonal b-Cr2N andmetallic Cr. Furthermore, thin lamellae yielded a (200) preferred growth orientation while thicker lamellae generated a mixtureof growth orientations. In addition, very thin lamellae must be deposited to obtain good fracture toughness. It was also foundthat it was necessary to use a negative substrate bias in order to obtain a high quality coating. © 1999 Elsevier Science S.A. Allrights reserved.

Keywords: Cemented carbide; Coating; Multilayer; PVD; TiN/CrN

1. Introduction coating is required, e.g. on moulds for Al alloy diecasting [2]. CrN is also known for its high toughness,which facilitates growth of thicker coatings (5–20 mm).For metal cutting tools two of the most commonA characteristic of CrN is that it is more difficult tocommercial PVD coatings are TiN and CrN. Two otherdeposit to its cubic NaCl phase, due to its lower nitrogenfrequently used coatings, not considered in this work,solubility and lower stability as compared to TiN.are Ti(C,N) and (Ti,Al )N. Of these TiN is by far theNevertheless, some papers have shown that it is possiblemost extensively investigated and used material. This isto grow stoichiometric cubic CrN coatings, e.g. Refs.partly due to the ease with which TiN can be deposited[2,4].to its very hard and wear resistant cubic NaCl phase (it

There have been several scientific works on multilay-has a large nitrogen solubility) and partly due to itsered PVD coatings, i.e. coatings obtained by alternatelybeautiful golden colour. CrN, with its excellent highdepositing two chemically and/or mechanically differenttemperature stability [1–3], is often utilised in applica-materials to form a layered structure, during the lasttions where a hard, oxidation- and corrosion-resistantyears. In many cases multilayered coatings have shownenhanced mechanical and tribological properties as com-pared to today’s single layered coatings [5,6 ]. It has* Corresponding author. Fax: +46-18-471-35-72.

E-mail address: [email protected] (M. Nordin) also been shown that by layering thin layers of a metal

0257-8972/99/$ – see front matter © 1999 Elsevier Science S.A. All rights reserved.PII: S0257-8972 ( 99 ) 00263-7

109M. Nordin, M. Larsson / Surface and Coatings Technology 116–119 (1999) 108–115

nitride (preferably less than a few nm of coatings such thereafter Ar ion etched for 15 min using a substratebias of −200 V. The coatings were reactively depositedas VN, NbN and CrN) with layers of TiN, fully NaCl

cubic coatings with a high hardness can be grown [7– using a combination of electron beam gun (e-gun)evaporation of Ti and d.c. magnetron sputtering of Cr.9]. Up to today, most of the research on multilayered

or superlattice coatings has been on the systems TiN/VN For all the multilayered coatings the depositionsequence started with the deposition of a 30 nm Ti layerand TiN/NbN [7,8]. Another multilayered coating

which has shown very interesting properties, such as followed by a 200 nm TiN layer to promote coatingadhesion. This was obtained while the substrates werehigh temperature stability and high fracture toughness,

is made of the two nitrides TiN and CrN [10,11]. Our held stationary above the Ti source. Simultaneously theCr target was Ar ion etched. By keeping both sourcesknowledge about the correlations between on the one

hand the growth dynamics, chemical composition, phase active and by alternately expose the substrates to the Tisource and the Cr source using substrate rotation, acomposition and microstructure, and on the other the

mechanical/tribological properties of multilayered multilayered coating was grown. The total pressure waskept constant at 2×10−3 mbar.TiN/CrN coatings is, however, scarce. Only a few works

concerning this coating can be found. Yashar et al. have Before the deposition of single layered CrN and TiNcommenced, a 30 nm layer (Cr and Ti, respectively) wasinvestigated the growth process and phase composition

of multilayered TiN/CrN0.6 as a function of lamella deposited. Single layered TiN and CrN were depositedby keeping only one of the material sources active andthickness [9]. They showed that CrN0.6, which normally

is hexagonal, can be stabilised into a cubic NaCl phase admitting nitrogen gas into the chamber. The totalpressure was kept at 1.7×10−3 mbar during the TiNprovided that the lamellae are kept less than 10 nm.

Furthermore, Panjan et al. showed that it is possible to deposition and at 3×10−3 mbar during the CrNdeposition.increase the activation energy for oxidation by layering

TiN with CrN (modulation periods in the range 83– The total deposition time was 40 min for all themultilayered coatings, 60 min for TiN and 160 min for425 nm) as compared to the single layered coatings

made of the constituents [12]. CrN. In Table 1 an overview of the evaluated processparameters are presented.The aim of this work is to increase our knowledge of

the growth dynamics and properties of multilayeredPVD TiN/CrN coatings. A number of multilayered 2.3. Coating characterisationTiN/CrN coatings have been characterised with respectto their growth rate, morphology, microstructure, chemi- From studies of fractured coating cross-sections,

information about the coating thickness, multilayercal composition and phase composition as well as theircomposite hardness and fracture toughness. The influ- period (L; the thickness of one lamella of TiN together

with one lamella of CrN) and coating morphology couldence of the lamella thickness and the deposition parame-ters: substrate bias, magnetron sputtering power and be obtained using scanning electron microscopy fitted

with a field emission gun (FEG-SEM ), see e.g. Fig. 1.nitrogen flow, on those characteristics has been eval-uated. In addition to the multilayered coatings, homo- An atomic force microscope (AFM) was used to reveal

the surface topography. Cross-sectional transmissiongeneous TiN and CrN have been included as referencecoating materials. electron microscopy ( XTEM) in a JEOL 2000 FXII

Table 12. ExperimentalAn overview of the deposition process parameters used. M(x) indicatesa multilayered TiN/CrN coating with the varied parameter within

2.1. Substrate material brackets [in comparison to the reference coating designated M(ref )]

Coating Substrate Magnetron N2 Substrate rotaryCemented carbide (10 wt% Co and 90 wt% WC) wasbias (V ) power (kW ) flow (sccm) speed (rpm)

used as substrate material. The substrate hardness was1350 HV30 kg. All substrates were polished to a surface TiN −110 – 140 10

CrN −110 2 40 10roughness of approximately 5 nm and then ultrasoni-M(ref ) −110 2 155 10cally cleaned in a heated alkaline solution followed byM(5 rpm) −110 2 155 5ethanol (5 min each).M(1 rpm) −110 2 155 1M(0 V ) 0 2 155 10

2.2. Coating deposition M(−200 V ) −200 2 155 10M(4 kW ) −110 4 155 10M(6 kW ) −110 6 155 10All coatings were deposited in a commercial BalzersM(115 sccm) −110 2 115 10BAI 640R coating unit. Prior to coating deposition, theM(195 sccm) −110 2 195 10

samples were resistively heated to 450°C for 60 min and

110 M. Nordin, M. Larsson / Surface and Coatings Technology 116–119 (1999) 108–115

developed by Oliver and Pharr [14]. A Berkovich dia-mond tip and an indentation depth of 150 nm wereused. By performing Rockwell C indentation tests (in acommercial scratch tester with the specimen translationdisconnected), information about the coating toughnesscould be gained. The load was continuously increasedup to 100 N at a loading rate of 10 N/min and subse-quently decreased at the same rate. As a measure of thecoating fracture toughness, the fracture load, LF, i.e. theload at the first coating fracture as detected usingacoustic emission (AE) was utilised [Fig. 2(a)]. In allcases, this load corresponded to a circular crack at therim of the indent, see Fig. 2(b). All indentations werepost-experimentally studied in a light optical microscope(LOM).

Fig. 1. Representative example of a SEM micrograph [M(6 kW )]showing the layered structure. In the micrograph the column diameteris indicated as well as 10 multilayer periods. 3. Results

3.1. Coating thickness and multilayer periodequipped with a LaB6 filament and a 200 kV voltagewas employed to evaluate the microstructure and

For the multilayered coatings it was found that theselected area electron diffraction (SAED) to determinecoating thickness (and the multilayer period), which isthe phase composition of one multilayered coating whichdirectly related to the coating growth rate since thein the following is denoted M(ref ).deposition time was the same for all multilayered coat-The chemical composition of the coatings was deter-ings, increased with magnetron power and nitrogen flowmined using Auger electron spectroscopy (AES). Toand slightly decreased with substrate bias, see Table 2.subdivide the intensity from the overlapping transitionsThe coating thickness was, however, not affected by theof Ti and N at approximately 382 eV into separatesubstrate rotary speed, while, naturally, L decreasedcomponents the method obtained by Dawson andwith increasing rotary speed.Tzatzov [13] was used. The electron beam energy and

emission current were 10 keV and 5 mA, respectively.All the sensitivity factors (Ti, Cr and N) were obtained 3.2. Morphology and microstructurefrom nitride reference powders. The phase compositionand preferred growth orientation were determined using All coatings deposited (both single- and multilayered)

displayed a dense and homogeneous surface morpho-a Siemens D5000 X-ray diffractometer. Cu Ka radiationover an area of approximately 1 mm2 was employed logy, see Fig. 3(a). The only exception was M(0 V ),

which appeared to be more porous, see Fig. 3(b). Noand the measurement range was 2h=30–100°. Nosample rotation was assessed during measurement. significant influence of the magnetron power, nitrogen

flow or rotary speed on the surface morphology wasThe composite hardness and Young’s modulus weredetermined using nanoindentation and the method observed.

Fig. 2. The fracture load (LF) was defined as the load corresponding to the first significant increase in the AE signal. (a) A typical example of theAE signal recorded during indentation. (b) Representative appearance of an indented coating, note the circular cracks each corresponding to oneof the AE peaks (SEM).


Table 2Coating thickness, t, multilayer period, L, chemical composition (approximate measurement scatter was 5%), Ti to Cr ratio (Ti:Cr), Me to N ratio(Me:N) and fracture load, LF

Coating t (nm) L (nm) at% Ti at% Cr at% N Ti:Cr Me:N LF (N )

TiN 3800±100 – 51 – 49 – 1.0 27±2CrN 4400±150 – – 53 47 – 1.1 32±1M(ref ) 3700±100 9.7±0.5 45 14 41 3.2 1.4 27±1M(5 rpm) 3600±100 19.1±1 46 11 43 4.2 1.3 26±1M(1 rpm) 3900±100 110.0±5 43 12 45 3.6 1.2 23±1M(0 V ) 3900±100 9.8±0.5 44 14 42 3.1 1.4 11±3M(−200 V ) 3400±100 9.5±0.5 48 12 40 4.0 1.5 27±9M(4 kW ) 4200±150 12.0±0.6 38 24 38 1.6 1.6 23±2M(6 kW ) 5000±200 14.5±0.7 32 35 33 0.9 2.0 24±3M(115 sccm) 2500±100 6.1a±0.5 37 21 42 1.8 1.4 24±2M(195 sccm) 4800±200 12.4±0.6 48 9 43 5.3 1.3 26±1

a Period is calculated from the coating growth rate since it was too thin to measure by SEM.

All coatings were found to have a more or less diameter increased with magnetron sputtering power.columnar structure when studied in SEM. When com- For the other multilayered coatings no clear differenceparing the multilayered coatings, the largest column in column size could be seen. The TiN coating displayeddiameter was found for the coating deposited at 0 V a more pronounced columnar microstructure than bothsubstrate bias. Furthermore, it was found that the CrN and the multilayered coatings.

XTEM displayed that M(ref ) was columnar, denseand fine grained (see Fig. 4), which is in agreement withthe results obtained using SEM. XTEM also showedthat coating growth, and hence coating surface profile,well followed the surface profile of the substrate. Thesubstrate roughness developed during Ar ion etching ofthe substrates prior to coating deposition. The lamellathickness of CrN and TiN was approximately 3 and7 nm, respectively. The SAED analysis revealed a 100%cubic NaCl phase composition, see diffraction patterninsert in Fig. 4. It was also observed that the diffraction

Fig. 3. Typical coating surface topography (AFM) of (a) the coatings Fig. 4. XTEM micrograph and SAED pattern of M(ref ). The broaden-ing of the diffraction peaks was due to coating growth on a not per-deposited using substrate bias [M(ref )] and (b) without substrate

bias [M(0 V )]. fectly smooth substrate.


Fig. 5. XRD patterns of the multilayered coatings with different L. S refers to peaks originating from the substrate.

spots were somewhat broadened as a result of coating peaks of b-Cr2N, together with the fact that thesecoatings are understoichiometric (with respect to thegrowth on a relatively rough substrate material.cubic TiN and CrN), it was not possible to determinethe origin of this peak. For simplicity, this peak will be3.3. Chemical and phase compositionreferred to as the (200) peak of TiN for the remainderof this paper.The single layered coatings had an elemental composi-

tion close to that of stoichiometric TiN and CrN M(1 rpm) showed, apart from the (200) peak, a peakresulting from (111) oriented TiN crystals as well as(Table 2). All multilayered coatings were found to be

understoichiometric (with respect to the cubic TiN and from (302) oriented b-Cr2N. No influence of the nitro-gen flow on the phase composition could be found.CrN phase), with a metal to nitrogen (Me:N) ratio

ranging from 1.3 to 2.0, see Table 2. It was also found M(4 kW ) displayed a broad peak of extremely lowintensity revealing small amounts of metallic Cr (PDFthat the substrate bias had no influence on the composi-

tion of the coatings. As expected, an increased magnet- file 06-0694) with a (200) preferred growth orientation.The intensity of the (200) Cr peak was found to increaseron power yielded a decrease in the Ti to Cr ratio as

well as the nitrogen content in the coatings (see Table 2). with magnetron power.An increased nitrogen flow was found to result in anincreased Ti to Cr ratio. The Me to N ratio was not 3.4. Coating hardness, Young’s modulus and fracture

toughnessaffected by the nitrogen flow, see Table 2.Single layered TiN displayed a cubic NaCl phase

(PDF file 31-1403) with a (111) preferred growth orien- The coating hardness and Young’s modulus of thecoatings are presented in Fig. 6. The hardness oftation. Single layered CrN showed a peak corresponding

to a lattice plane spacing of 2.03 A. Due to the large the TiN and CrN was 26.5 and 23.3 GPa, respectively.The hardness of the multilayered coatings ranged fromwidth of this peak it could not be concluded whether it

corresponded to the cubic NaCl phase (PDF file 29.1 GPa to 31.9 GPa. In addition, the coating hardnessdecreased with increasing magnetron power, i.e. increas-11-0065) with a (200) preferred growth orientation or

the hexagonal b-Cr2N (PDF file 35-0803) with a (111) ing Cr:Ti and Me:N ratio. It was also found that thehardness decreased with the rotary speed of the sub-or (200) preferred growth orientation. However, the

chemical composition suggests that it was the cubic strates, i.e. with increasing lamella thickness.Young’s modulus of the multilayered coatings wasNaCl phase of CrN.

All multilayered coatings possessed a peak originating found to range between the value for CrN (340 GPa)and the value for TiN (500 GPa). The modulus wasfrom a plane spacing of approximately 2.13 A, see Fig. 5.

This corresponds well to the (200) peak of the cubic found to be relatively insensitive to changes in theprocess parameters. The only exception was found forTiN phase. Unfortunately, due to a slight peak overlap

of the (200) peak of cubic CrN, the (111) and (200) the magnetron power, for which the modulus decreased


Fig. 6. Coating hardness and Young’s modulus of the coatings.

with increasing magnetron power, i.e. with increasing to 1.1 and that the nitrogen content decreased from41 at% to 33 at%. In addition, the coatings depositedCr:Ti and Me:N ratio, see Fig. 6.

The fracture load, LF, ranged between 11 and 32 N, using a high magnetron power, i.e. M(4 kW ) andM(6 kW ), contained small amounts of metallic (200)see Table 2. The lowest load was found for M(0 V ),

whereas the highest was found for the single layered oriented Cr. Evidently, for these two coatings, thenitrogen partial pressure must be increased in order toCrN coating. For TiN and all multilayered coatings the

level of the fracture load was comparable, in the range retain a stoichiometric multilayered TiN/CrN coating.However, this was not possible as an increase in nitrogenof 23 N to 27 N. The intensity of the AE signal, detected

at the fracture load LF, was in all cases 0.5–6 dB [cf. partial pressure will act detrimentally on the quality ofthe TiN phase. The reason for this is that the electronFig. 2(a)], and corresponded to fracture at the rim of

the indent, cf. Fig. 2(b). At higher load some of the beam evaporation process of TiN requires a relativelylow total pressure as compared to that of the d.c.coatings displayed a high intensity signal of 30–150 dB

[at 33 N for CrN, 76 N for M(1 rpm), 59 N for M(0 V ), magnetron sputtering process.By increasing the nitrogen flow from 115 to 195 sccm57 N for M(6 kW ) and 88 N for M(115 sccm)], see

Fig. 7(a). This load was found to correspond to spalling an increase in the Ti to Cr ratio from 1.8 to 5.3 wasobtained, whereas the nitrogen content in the coatingof the coating, see Fig. 7(b).was unaffected. This was believed to be a result of thefact that the evaporation rate of Ti increases with thenitrogen flow, since the Ti emission was controlled to4. Discussionobtain a constant total pressure (and therefore also aconstant partial pressure of N2) in the chamber. As a4.1. Chemical and phase compositionresult, the nitrogen content in the coating will beunchanged. Another explanation for the increase of TiBy increasing the magnetron power from 2 to 6 kW

it was found that the Cr to Ti ratio increased from 0.3 as compared to Cr could be that the nitrogen reactivity

Fig. 7. Representative examples of (a) high intensity AE signal and (b) the corresponding coating failure.


Table 3 to a mixed phase and texture composition of (200)Estimated TiN and CrN lamella thickness and/or (111) and (302) b-Cr2N. Hence, the critical

thickness for transformation must be somewhereCoating tTiN (nm) tCrN (nm)between 5 and 31 nm.

TiN – – It is clear that the lamella thickness, i.e. the thicknessCrN – – of deposited material per revolution, has to be kept lowM(ref ) 7 3 in order to stabilise the cubic NaCl phase as well as theM(5 rpm) 14 5

(200) preferred growth orientation. The reason why theM(1 rpm) 80 30single layered CrN most likely exhibits a NaCl phaseM(0 V ) 7 3

M(−200 V ) 7 3 with 100% (200) preferred growth orientation is proba-M(4 kW ) 7 5 bly the high rotary speed of the substrates used duringM(6 kW ) 7 8 CrN deposition. This will result in a short exposure timeM(115 sccm) 3 3 above the sputtering target. As a result, only thinM(195 sccm) 10 3

(approximately 3 nm) CrN layers will be deposited ateach revolution. This also ensured a thorough argon ionetching of each CrN layer deposited, since the etchingis higher for Ti than for Cr. This was found by Jehntakes place almost solely away from the sputteringet al. [3] who showed that the Ti to Cr ratio increasedtarget. To confirm this theory an additional CrN coatingfrom 2.5 to 4.0 as the nitrogen pressure was increasedwith the substrates held stationary over the sputteringfrom 8×10−5 to 3×10−3 mbar, although no pressuretarget was deposited. It was observed that thecontrol was utilised.coating consisted of a mixture of cubic CrN and hexago-It is clear that when discussing the influence of thenal b-Cr2N, or more likely only hexagonal b-Cr2N.deposition parameters on the phase composition of theApart from a peak representing (200) CrN and/or (111)coatings it would be more convenient to use the lamellab-Cr2N, which was still the dominating diffraction peak,thickness, i.e. the thickness of the individual layers ofseveral peaks were present such as (200) Cr, (111)TiN and CrN, instead of the multilayer period, sinceb-Cr2N, (112) b-Cr2N and (302) b-Cr2N.the two individual components have different properties.

Unfortunately, the individual lamella thickness cannot4.2. Fracture toughnessbe determined accurately for all the multilayered coat-

ings using FEG-SEM. Therefore an estimation of theThe coatings that displayed cohesive/adhesive failures

lamella thicknesses was done and used when discussing at high indentation loads have one feature in common,the phase composition and mechanical properties of the namely thick CrN lamellae [approximately 30 nm incoatings, see Table 3. M(1 rpm)] or a high CrN to TiN ratio [8:7 for M(6 kW )

An interesting finding was that M(1 rpm) showed and 3:3 for M(115 sccm)]. From this it can be concludeddiffraction peaks originating from cubic NaCl TiN (111) that CrN lamellae should be kept thin if a coating withas well as of TiN (200), cf. Fig. 5. Homogeneous TiN high cohesive strength is to be made. Finally it can bedisplayed only a (111) peak, whereas thin TiN lamellae mentioned that the results of the indentation tests werein e.g. M(ref ) and M(5 rpm) only displayed a (200) in agreement with the results obtained in an earlierpeak. This ought to mean that the thickness of the TiN investigation of the coating cohesion/adhesion using thelamellae in M(1 rpm) was higher than the critical thick- well-known scratch test [15].ness for transformation of the preferred growth orienta-tion from (200) to (111). That is, the critical lamellathickness for the transformation is in the range 14 5. Summaryto 80 nm.

A similar finding was done for the CrN. For the The investigation was performed in order to increaseM(1 rpm) coating four peaks originating from (200) the understanding of multilayered PVD coatings andCrN, (200) b-Cr2N, (111) b-Cr2N as well as (302) especially of the TiN/CrN coating system. It was foundb-Cr2N were observed (Fig. 5). For the coatings with that a dense, fully NaCl cubic, multilayered PVDthinner CrN lamellae, i.e. M(ref ) and M(5 rpm), only TiN/CrN coating with a high cohesive strength can bethe (200) CrN peak and/or (200) and (111) b-Cr2N deposited using the hybrid technique combining reactivepeak were observed. The SAED analysis showed that electron beam evaporation of Ti and d.c. magnetronthe M(ref ) consisted of 100% cubic phase, i.e. no traces sputtering of Cr. To obtain a high quality coating it wasof the b-Cr2N were found. This indicated that the necessary to use not only a negative substrate bias, butthickness of the CrN lamella in the M(1 rpm) was also to deposit very thin TiN lamellae, ≤14 nm, andabove, and in the M(ref ) [and probably also M(5 rpm)] thin CrN lamellae, ≤5 nm. Thin lamellae seem to inhibitbelow, the critical thickness for transformation from the transformation from growth of the cubic NaCl phase to

new phases, e.g. the hexagonal b-Cr2N and the metallicNaCl phase with a (200) preferred growth orientation


[2] B. Navinsek, P. Panjan, Surf. Coat. Technol. 74/75 (1995) 919.Cr. Furthermore, thin lamellae coatings grew in a 100%[3] H.A. Jehn, F. Thiergarten, E. Ebersbach, D. Fabian, Surf. Coat.(200) preferred orientation, while thicker lamellae coat-

Technol. 50 (1991) 45.ings displayed a mixed texture. [4] S.B. Sant, K.S. Gill, Surf. Coat. Technol. 68/69 (1994) 152.

[5] C. Subramanian, K.N. Strafford, Wear 165 (1993) 85.[6 ] H. Holleck, V. Schier, Surf. Coat. Technol. 76/77 (1–3) (1995)

328.Acknowledgements[7] U. Helmersson, S. Todorova, S.A. Barnett, J.-E. Sundgren, L.C.

Markert, J.E. Greene, J. Appl. Phys. 62 (2) (1987) 481.The financial support of AB Sandvik Coromant and [8] X. Chu, M.S. Wong, W.D. Sproul, S.L. Rohde, S.A. Barnett,

J. Vac. Sci. Technol. A 10 (4) (1992) 1604.the Swedish Research Council for Engineering Sciences[9] P. Yashar, X. Chu, S.A. Barnett, J. Rechner, Y.Y. Wang, M.S.(TFR) is gratefully acknowledged. Torbjorn Selinder at

Wong, W.D. Sproul, Appl. Phys. Lett. 72 (8) (1998) 987.AB Sandvik Coromant is recognised for providing the[10] U. Wiklund, O. Wanstrand, M. Larsson, S. Hogmark, Wear

cemented carbide substrates. (1998) in press.[11] M. Nordin, M. Larsson, S. Hogmark, Surf. Coat. Technol. 106

(2/3) (1998) 234.[12] P. Panjan, B. Navinsek, A. Cvelbar, A. Zalar, J. Vlcek, Surf.References Coat. Technol. 98 (1998) 1497.[13] P.T. Dawson, K.K. Tzatzov, Surf. Sci. 149 (1985) 105.

[1] O. Knotek, F. Loffler, H.-J. Scholl, Surf. Coat. Technol. 45 [14] W.C. Oliver, G.M. Pharr, J. Mater. Res. 7 (6) (1992) 1564.[15] M. Nordin, M. Larsson, S. Hogmark, Wear (1998) in press.(1991) 53.

deposition and characterisation of multilayered pvd tin/crn coatings on cemented carbide

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