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Surface & Coatings Technolo

Deposition of superhard TiAlSiN thin films by

cathodic arc plasma deposition

S.K. Kim *, P.V. Vinh, J.H. Kim, T. Ngoc

School of Materials Science and Engineering, University of Ulsan, Ulsan, 680-749 South Korea

Abstract

Thin films of TiAlSiN were deposited on AISI H13 tool steel substrate using Ti and AlSi cathodes by a cathodic arc plasma deposition system.

The influence of the nitrogen pressure, AlSi cathode arc current, bias voltage, and deposition temperature on the mechanical and the structural

properties of the films were investigated. The hardness of the film decreased with the increase of nitrogen gas pressure. The hardness of the film

increased with the increase of AlSi cathode arc current and the bias voltage. The hardness of the film reached 48 GPa at the deposition temperature

of 300 -C and decreased with a further increase of the temperature. Wear and scratch tests were performed on thin films deposited in various

conditions. The critical load of the films was above 50 N.

D 2005 Elsevier B.V. All rights reserved.

Keywords: TiAlSiN thin films; Cathodic arc plasma deposition; Superhard properties

1. Introduction

Hard coatings are applied to the surfaces of mechanical

components subjected to wear in order to increase their

durability and performance. One main application is hard

coatings for cutting tools such as drills, end mills and indexable

cutting inserts. Titanium nitride (TiN) is widely used as a

protective coating for such an application. Recently, titanium

aluminum nitride (TiAlN) coatings were developed to improve

the high temperature oxidation resistance of TiN coatings.

Further research to improve the oxidation resistance and

mechanical properties of these coatings led to the development

of titanium silicon nitride (TiSiN) [1–10] and titanium

aluminum–silicon nitride (TiAlSiN) coatings [11–15].

TiSiN films have been deposited by plasma enhanced

chemical vapor deposition [1,2] or magnetron sputtering [3–

6]. Recently, deposition of TiSiN films by a hybrid method of

cathodic arc and magnetron sputtering method was reported by

Martin and Bendavid [7] and Kim et al. [8]. Veprek and Jilek

reported deposition of nanocrystalline-TiN/amorphous-Si3N4

by vacuum arc evaporation from segmented cathodes [9] and a

combined CVD and PVD technique [10]. TiAlSiN films have

been deposited by magnetron sputtering [11,12] and cathodic

0257-8972/$ - see front matter D 2005 Elsevier B.V. All rights reserved.

doi:10.1016/j.surfcoat.2005.08.109

* Corresponding author. Tel.: +82 52 259 2228; fax: +82 52 259 1688.

E-mail address: skim@ulsan.ac.kr (S.K. Kim).

arc method [13–15]. In the cathodic arc process, they used

TiAlSi cathodes prepared by a powder metallurgical technique

which are relatively expensive. TiAlSiN films were also

prepared by a hybrid method of cathodic arc and magnetron

sputtering [16]. These films exhibit hardness values in excess

of 40 GPa. Their superhard properties are attributed to the

refinement of the grain size in which one or more phases are

present at the nanoscale to form a nanocomposite layer.

In this study, TiAlSiN films were deposited on AISI H13

tool steel by cathodic arc plasma deposition using two cathodes

of titanium and aluminum–silicon. The main purpose of this

work was to determine the feasibility of producing TiAlSiN

superhard nanocomposite films by a cathodic arc plasma

deposition method using cathodes prepared at low cost.

2. Experimental procedures

TiAlSiN films were deposited on AISI H13 tool steel (1.5%

C, 11.5% Cr, 0.8% Mo, 0.9% V) substrate by a typical cathode

arc plasma deposition equipment. A schematic diagram of the

experimental apparatus is shown in Fig. 1. One source fitted

with a titanium cathode (diameter of 63 mm) and the other with

an aluminum–silicon cathode (Al 88 wt.%, Si 12 wt.%,

diameter of 63 mm) were installed facing each other on each

side of the chamber wall. A small rectangular baffle (46

mm�178 mm) was installed between the cathode and the

gy xx (2005) xxx– xxx

www.el

SCT-11721; No of Pages 4

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Mot

or ArN2

M.F.CPump Arc

Power Supply

Filter

Trigger

Bias Power Supply

Arc Power Supply

Cathode

Vacuum gauge

Sample holder

Fig. 1. Schematic diagram of the experimental apparatus.

a)

b)

c)

d)

0 10 20 30 40 50 N

Fig. 3. Optical micrographs of scratch tracks of TiAlSiN films deposited with

various nitrogen pressure ((a) 0.2 Pa, (b) 0.4 Pa, (c) 0.6 Pa, (d) 0.93 Pa

temperature 250 -C, bias �50 V, AlSi cathode arc current 35 A, Ti cathode arc

current 55 A).

3.1

35 40 45 50 552.7

2.8

2.9

3.0

AlSi cathode arc current (A)

(a)

Si c

onte

nt (

wt.

%)

S.K. Kim et al. / Surface & Coatings Technology xx (2005) xxx–xxx2

substrate to prevent macroparticle deposition on the substrate.

A sample holder, which could be rotated while applying bias

voltage, was located at the center of the chamber. The substrate

to the cathode distance was 280 mm.

The AISI H13 steel specimens were manually ground and

polished with 1500-grit SiC papers using a low speed polishing

machine and degreased ultrasonically in alcohol. After the

chamber was evacuated to 1.20�10�3 Pa using a rotary pump

and a turbomolecular pump, argon was introduced to maintain

an etching pressure of 86.6 Pa. At this pressure, the samples

were sputter-etched for 40 min with 600 mA and 300 V. Then,

argon was replaced with nitrogen to maintain a working

pressure of 1.3�10�1 Pa. The substrates were heated to a

predetermined value by resistance heaters set inside the

chamber and then, TiAlSiN films were deposited from titanium

cathode and aluminum–silicon cathode by rotating the

substrate. Arc current for titanium cathode was 55 A and 35

A for aluminum–silicon cathode.

The nitrogen pressure, deposition temperature, bias volt-

age, arc current of the AlSi cathode was varied to determine

the effects of these deposition parameters on the structure and

mechanical properties of the films. An X-ray diffractometer

0.2 0.4 0.6 0.8 1.0

25

30

35

40

45HardnessModulus

Pressure (Pa)

300

350

400

450

500

Modulus (G

Pa)

Har

dnes

s (G

Pa)

Fig. 2. Effect of nitrogen pressure on the hardness of TiAlSiN films

(temperature 250 -C, bias �50 V, AlSi cathode arc current 35 A, Ti cathode

arc current 55 A).

400

35 40 45 50 55

28

30

32

34HardnessModulus

AlSi cathode arc current (A)

Har

dnes

s (G

Pa)

250

300

350

(b)

Modulus (G

Pa)

Fig. 4. Effect of AlSi arc current on the Si content (a) and hardness of TiAlSiN

films (b) (pressure 4�10�1 Pa, bias�50 V, temperature 250 -C, Ti cathode arccurrent 55 A).

;

ARTICLE IN PRESS

35 40 45 50 550

10

20

30

40

50

Ti Al N O

AlSi cathode arc current (A)

Con

tent

(W

t. %

)

Fig. 5. Effect of AlSi arc current on Ti, Al, N and O contents (pressure 4�10�1

Pa, bias �50 V, temperature 250 -C, Ti cathode arc current 55 A).

-50 -100 -150 -200

30

35

40

45Hardness

Modulus

300

350

400

450

500

550

Bias potential (V)

Modulus (G

Pa)H

ardn

ess

(GP

a)

Fig. 7. Effect of bias voltage on the hardness of TiAlSiN films (pressure

4�10�1 Pa, temperature 250 -C, AlSi cathode arc current 35 A, Ti cathode arc

current 55 A).

S.K. Kim et al. / Surface & Coatings Technology xx (2005) xxx–xxx 3

(Rigaku, RAD-3C) was used to determine the phases of the

films. A field emission scanning microscope (JEOL, JSM-

820) was used to observe morphology of the films. Content

of elements in the film was determined by an electron probe

microanalyzer (EPMA-1400, Shimadzu). A computer-con-

trolled nanoindentor (MTS, Nanoindentor XP) equipped with

Berkovich diamond indentor was used to measure the

hardness of the films. The continuous stiffness measurement

method was employed. Wear resistance was measured by a

ball-on-disc type wear tester at 100 rpm, 5 N load. Adhesion

was evaluated by a scratch tester (Revetest, CSEM).

3. Results and discussion

The effect of nitrogen pressure on the hardness of the

TiAlSiN films is shown in Fig. 2. The hardness of the films

decreased with the increase of the nitrogen pressure. Fig. 3

shows optical micrographs of scratch tracks of TiAlSiN films

deposited at various nitrogen pressure. The films deposited at

4�10�1 Pa and 9.3�10�1 Pa spalled a little. Comparison of

scratch tracks of 4�10�1 Pa and 6�10�1 Pa, the films

20 40 60 80 100

55A

50A

43A

35A

TiN

(11

1)

TiN

(20

0)

TiN

(22

0)

TiN

(31

1)

Inte

nsit

y (a

.u)

2θ (Degree)

Fig. 6. XRD diffractograms of TiAlSiN films deposited with various AlSi arc

current (pressure 4�10�1 Pa, bias �50 V, temperature 250 -C).

deposited at 4�10�1 Pa was found to be more stable since

partial edge of the films deposited on the disc type samples at

2�10�1 Pa spalled. Therefore, the pressure of 4�10�1 Pa

was chosen for subsequent experiments. To determine the

effect of silicon content in the film, the aluminum–silicon

cathode arc current was varied from 35 to 55 A. The titanium

cathode arc current was kept constant at 55 A (Fig. 4). The

silicon content of the film increased with the increase of the

aluminum–silicon cathode arc current resulting in the increase

of the hardness of the films. This hardness enhancement is

believed to be due to grain-boundary hardening both by

strong cohesive energy in interphase boundaries [17]. Another

possible reason would be due to solid-solution hardening of

crystallites by Si dissolution into Ti–Al–N [15,18]. Fig. 5

shows the effect of AlSi cathode arc current on the Ti, Al, N

and O contents in the film. The aluminum content increased

whereas the titanium content decreased with the increase of

AlSi cathode arc current.

Fig. 6 shows XRD diffractograms of TiAlSiN films

deposited with various AlSi cathode arc currents. The

diffraction pattern shows the presence of crystalline TiN with

250 300 350 40030

35

40

45

50

HardnessModulus

Har

dnes

s (G

Pa)

350

400

450

500

550

600

Modulus (G

Pa)

Temperature (0C)

Fig. 8. Effect of deposition temperature on the hardness of TiAlSiN films

(pressure 4�10�1 Pa, bias �50 V, AlSi cathode arc current 35 A, Ti cathode

arc current 55 A).

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Fig. 9. Cross-sectional HRTEM images of TiAlSiN films.

S.K. Kim et al. / Surface & Coatings Technology xx (2005) xxx–xxx4

mixed orientation of (111), (200), (220), and (311) crystal

planes. As the silicon was incorporated into the TiAlN, the

diffraction peak intensities reduced gradually. However, the

TiN (200) peak became strong when the films were deposited

with 55 A. Park et al. also reported that the XRD peak shape of

TiAlSiN films was broadened with an increase of Si contents

[16]. In general, XRD peak broadening is believed to originate

from the diminution of grain size or the residual stress induced

in the crystal lattice [10]. Peak broadening was notable with the

films deposited with 50 A arc current of AlSi cathode. The

films deposited with this arc current exhibited best wear

resistance. Adhesion of these films was best as shown in Fig. 2.

The effect of bias voltage on the hardness of TiAlSiN films is

shown in Fig. 7. With the increase of bias voltage, the TiN phase

became more crystalline resulting in increased hardness of the

films. Fig. 8 shows the effect of deposition temperature on the

hardness of the TiAlSiN films. The films deposited at 300 -Cshowed maximum hardness. XRD diffractogram of these films

showed that TiN phase in the films was more crystalline at this

temperature. Further experiments were performed with the bias

voltage of �150 V. Wear resistance of the films deposited at

�150 V was better than those deposited at�200 V. So, this bias

voltage was chosen. The hardness of these films increased with

the increase of deposition temperature showing maximum

hardness of 44 GPa at 350 -C.A further increase in temperature decreased the hardness of

the films. The hardness of the films was dependent on the

deposition process parameters. We obtained maximum hard-

ness of the films at deposition temperatures around 300 and

350 -C. Scratch tests on these films exhibited critical load

higher than 50 N, whereas films deposited without the bias

voltage showed very low critical load.

Fig. 9 shows a cross-sectional HRTEM image of a TiAlSiN

film. The crystalline order on this HRTEM picture is locally

poor. However, it is interesting that very high hardness was

obtained at these films deposited at relatively low temperatures.

It is feasible to produce TiAlSiN superhard thin films by

using Ti and AlSi cathodes. However, further research is

necessary to decrease macroparticle generation for this process

to be implemented in industries.

4. Conclusion

TiAlSiN films were deposited on AISI H13 tool steel using

simultaneously a titanium cathode and an aluminum–silicon

cathode by a cathodic arc plasma deposition method. The

hardness of the films decreased with the increase of the nitrogen

pressure. The silicon content of the films increased with the

increase of the aluminum–silicon cathode arc current resulting

in the increase of the hardness of the films. The films deposited

with 50 A aluminum–silicon cathode arc current exhibited best

wear resistance. These films showed themost notable XRD peak

broadening. With the increase of the bias voltage, the TiN phase

became more crystalline resulting in increased hardness of the

films within the bias voltage range investigated. The hardness of

the films increased with the increase of the deposition

temperature showing maximum hardness at the temperature

ranges of 300–350 -C. Further increase of the deposition

temperature decreased the hardness of the films.

Acknowledgement

This work was supported by the Korean Ministry of Science

and Technology through the Traditional Technology Innova-

tion Research Program. The authors gratefully acknowledge

Prof. J. Y. Lee at KAIST for his HRTEM work.

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