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Tribological behaviour of TiAlBN-based PVD coatings
:
Surface
and Coatings Technology 86-87 (1996)467-471
Tribological behaviour of Ti-Al-B-N-based
PVD coatings
S. Heck *, T. Emmerich, I. Munder, J. Steinebrunner Furtwangen Polytechnical University, Jakob-Kienzle-Stra$Ie 17 D-78054 VS-Schwenningen, Germany
Abstract PVD-coatings based on TiB, are expected to show high wear resistance and low tendency of adhesion on metal forming tools. Coating adhesion and morphology can be modified over a wide range by varying the content of nitrogen (NJ and the deposition parameters power and bias voltage. All coatings were deposited using commercial unbalanced magnetron equipment, the deposition was homogeneous in a volume of 400 x 400 x 400 mm’. Hipped and hot pressed TiB,-targets were used, nitrogen (N,) was added as gas, Ti and Al by a solid Ti-Al-target. The tribological behaviour was tested by a pin-on-disc wear test. The coatings investigated were TiB2, TiAIB(N), TiAl(N) and TiB,/TiAl(N). As counterpart in the pin-on-disc wear test, 6 mm diameter spheres of steel (lOOCr6), aluminium, brass and bronze were used. The experiments showed a non-uniform wear behaviour. For the combinations
TiAlB(N) and TiB? versus aluminium, a low wear volume of the coating and adhesive tendency was found. Brass led to abrasive wear on all coatings, whereas bronze showed a strong adhesive tendency on all tested coatings. Using a steel sphere the dominant wear mechanism was tribochemical oxidation. Keywords: Tribological
behaviour; Ti-Al-B-N-based
PVD coating; Wear mechanism; Pin-on-disc
1. Introduction
The tribological behaviour of PVD-coatings has an increasingly important position in cold, semi-hot and hot extrusion of steel and non-ferrous metals. A smooth surface together with a wear resistant coating results in higher productivity and longer life for modern tools. The standard forming tool made of cemented metal carbide, cold work steel and high speed steel has a high strength and impact strength, but the wear resistance on the surface is low. Over the last 10 years more manufacturers have been using coated tools in their production and so the use of PVD-coatings rate high. The process situation for forming tools varies from case to case and so for each particular application tailor-made coatings are required. Carbides, borides and nitrides of transition metals have been increasingly used for wear reduction in tools and machine components within the last few years [ 1). The resistance against abrasive wear is normally related to the hardness of the wear parts [2]. TiB, in particular is a stable, superhard and electrically conductive refractory material with a high melting point. This combination of properties makes TiBl an interesting prospect for a wide range of mechanical applications * Corresponding author. 0257-8972/96/$15.000 1996Elsevier Science S.A. All rights reserved PIZ SO257-8972(96)02987-k?
test
in an erosive, abrasive, corrosive or high temperature environment [3]. Advantages of TiAl(N) are the important physical and mechanical properties, including hardness, adhesion, toughness, wear resistance, chemical inertness and good thermal properties [4,5]. The coating system TiAlB(N) should combine the good properties of both TiB, and TiAI(N). The present study shows the wear properties of the coating systems against steel, aluminium, brass and bronze using a CSEM pin-ondisc-test.
2. Experimental details All coatings were deposited by means of a commercial Ceme Con CC800 magnetron sputtering apparatus with substrate bias on S-6-5-2 hardened (63HRC) high speed steel (1.3343 or BM2). All samples were mechanically polished (R,= 0.54 pm and R, =O.OSpm) and subsequently cleaned (hot-ultrasonic-alkaline cleaning, water rinsing, distillation rinsing, pressure-air drying) and sputter etched in a vacuum by argon ion bombardment. The samples were mounted in such a way that, while rotating around the horizontal axis of the vacuum chamber, the primary area to be coated was facing the target. Hipped and hot pressed TiB,-targets were used, nitrogen (NJ
468 Table 1 Conditions Counterpart
S. Heck et al./Surface and Coatings Technology 86-87 (1996) 467-471
for the pin-on-disc materials
the lowest critical load of 67 N on S-6-5-2, whereas the critical load of TiAl(N) was 118 N. The duplex coating TiB,/TiAl(N) and the TiAlB(N) coating had the same critical load of 112 N. The microhardness and thickness results are given in Table 2. The hardness was measured on the coated high speed steel samples. For example, the hardness of TiAl(N) (2059 HV,,05 on S-6-5-2) differs from what is normally seen for such coatings. The hardness of TiAl(N) coated cemented carbide (quality KlO) is 3400 HV0.05, which is in the range as described in the literature.
wear test Steel (lOOCr6), aluminium, brass and bronze 6mm 2N 500 m 14 mm 300 rev min-’ no 22.5-25.8”C 6.8-9.0%
Counterpart diameter Normal force Total sliding distance Radius of wear track Revolution speed Lubrication Temperature Relative humidity
was added as gas, Ti and Al by a solid Ti-Al-target. Typical sputter conditions, applied to the deposition process, were a d.c. power of 1925-3500 W (power/surface of 0.11-0.20 W mme2), a total gas pressure of 0.5-l Pa and an anode voltage of 100 V. The thickness was measured by CSEM calo test and optical microscopy, adhesion with the scratch test (Revetest CSEM). The hardness was measured by a Leitz microhardness tester using a Vickers diamond and 0.49 N load. The structure of the coating was investigated by means of scanning electron microscopy (SEM). Examinations of the tribological properties were performed with a CSEM pin-on-disc test. The sliding friction coefficient, the wear appearance and the volumetric wear of the TiB,, TiAlB(N), TiAl(N), TiB,/TiAl(N) coatings and the uncoated steel S-6-5-2 were measured against steel (lOOCr6), aluminium, brass and bronze spherical counterparts without any lubricant. The conditions for the pin-on-disc wear testing experiments are shown in Table 1. The PVD-process was controlled by optical emission spectroscopy.
3. Results and discussion 3.1. Critical loads offailure, hardness and thickness
A commercial CSEM scratch tester with a Rockwell C diamond, with a tip radius of 0.2 mm and a cone angle of 120”, was used. The load was O-200 N and the distance 10 mm at a speed of 1 mm s-r. During scratching, the friction force between diamond and coating was continuously monitored. Afterwards the results were verified by optical microscopy. The TiB2 coating showed Table 2 Hardness
and thickness
Hardness (HV,,,,r Thickness (urn)))
3.2. Volumetric wear of counterpart The pin-on-disc test showed, in the case of boron coatings, that the aluminium counterpart had a high volumetric wear. For example, TiB2 showed the highest volumetric wear. TiAlB(N) and the duplex coating TiB,/TiAl(N) have less tendency to friction against aluminium but the volumetric wear is twice as high as the TiAl(N) coating. When the coating was TiAlB(N), bronze showed the highest volumetric wear. TiB, and the duplex coating led to approximately the same volumetric wear as bronze. The volumetric wear caused by the coatings is shown in Fig. 1. TiAl(N) caused higher volumetric wear of bronze than the TiB, and the duplex coating, but TiAlB(N) caused the highest wear. When using brass as the counterpart, TiB2 caused the highest volumetric wear of the counterpart. With regard to lOOCr6, TiAl(N) caused the highest wear of the sphere. Comparing the boron coatings, TiAlB(N) caused the most volumetric wear. The uncoated sample S-6-5-2 led to high volumetric wear of aluminium, but boron coatings caused higher sphere volumetric wear. Bronze caused high volumetric wear of S-6-5-2, but with TiAl(N) and TiAlB(N) it was even higher. Uncoated samples caused the highest volumetric wear of brass. The wear of the counterparts correspond to the tribological behaviour. 3.3. Tribological behaviour and the determination of the friction coejicient p During measurement, the friction coefficient p of the sphere and the counterpart sample was determined. The friction coefficients and the tribological behaviour are
results TiAl(N)
TiB,
TiAlB(N)
TiB,/TiAl(N)
2059 4.2
1843 2.7
1758 4.1
1604 TiAl(N):
“Average of five measurements, base material bAverage of three measurements.
steel S-6-5-2.
1,5 TiB,: 1,7
S. Heck et al./Surface and Coatings Technology 86-87 (1996) 467-471
TiAI( N)
TiBP
TiAIB(N)
TiB2-TiAI(N)
uncoated S6-5-2
Coating system
Aluminium
Bronze
n Brass
Fig. 1. Volumetric wear of counterpart.
presented in Table 3. All measured friction coefficients were determined following stabilisation. The high friction coefficient resulted from the low relative humidity, 6.8-9.0%, without lubrication and a normal force of 2 N. Compared to its counterpart aluminium, TiBz showed low adhesion and low smoothing of the coating surface by high volumetric wear (see Fig. 2). The behaviour of
the duplex coating TiB,/TiAl(N) (TiB2 on the top) against all counterparts is similar to TiB2, with respect to the same friction coefficient. The tribological wear behaviour of TiB, against bronze resulted in strong adhesion with deep grooves on the coating surface (see Fig. 3). The wear of the TiAlB(N) coating against brass showed strong abrasion and grooves on the coating
Table 3 Tribological behaviour and friction coefficient of counterpart matching (friction coefficient p is given in parentheses’) Counter part
Coating system TM(N)
TiB2
TiAlB(N)
TiBJTiAl(N)
uncoated S 6-5-2
Aluminium
low abrasion, Alparticles on coated surface (0.8 1)
low adhesion, low smoothing of coated surface (0.94)
Al-particles, low adhesion, smoothing of coated surface (0.91)
low adhesion, smoothing of coated surface (0.90)
strong adhesion, tribochemical reactions, surface grooves (0.82)
Bronze
strong adhesion, particles, low grooves on coated surface (0.96)
strong adhesion, deep grooves on coated surface (0.50)
strong adhesion, no surface grooves (0.99)
low adhesion, deep grooves on coated surface (0.48)
strongest surface adhesion, tribochemical reactions (0.63)
Brass
low abrasion, deep grooves on coated surface (0.17)
low abrasion, deep grooves on coated surface (0.20)
strong abrasion, grooves on coated surface (0.10)
strong abrasion, grooves on surface (0.15)
strongest abrasion, tribochemical reactions, strong surface grooves (0.38)
lOOCr6
no tribochemical reactions, particles, low adhesion on coated surface (0.84)
strong tribochemical reactions on coated surface (0.75)
low adhesion, particles, no tribochemical reactions on coated surface (0.78)
low tribochemical reaction on coated surface (0.75)
strongest tribochemical reactions, abrasion, surface grooves (0.94)
“Average of three measurements.
S. Heck et al. jSurface
470
Fig. 2. Wear track: TiB, coating
against
Fig. 3. Wear track: TiB, coating
aluminium
against
bronze
and Coatings Technology 86-87 (1996) 467-471
sphere.
sphere.
surface (see Fig. 4), but a low adhesion of brass particles was found. TiAlB( N) showed no tribochemical reactions on the coating surface against IOOCr6 (see Fig. 5). TiAl(N) against a lOOCr6 sphere showed no tribochemical reactions and low adhesion on the coated surface
Fig. 4. Wear track: TiAIB(N)
-. Pig. 5. Wear track: TiAlB(N)
coating
coating
against
against
brass sphere.
steel lOOCr6 sphere.
(see Fig. 6). Brass showed high abrasion in all tribological tests. lOOCr6 without lubrication, tends to lead to tribochemical reactions. The reason why the friction coefficient of brass without lubrication has such low
S. Heck et al./Surface and Coatings Technology 86-87 (1996) 467-471
471
against various counterparts. In the case of concrete applications, e.g., cold, semi-hot and hot extrusion and interrupted-cut machining without lubrication, further tests must be undertaken to find the suitable coating. The pin-on-disc test showed a wide range of tribological behaviour. Up to now TiB, seems to be most qualified to transform and machine aluminium. TiAlB(N) promises to be a suitable coating to transform brass. The results show that TiAl(N)-coatings seems to be qualified for the transforming of steel. The characterisation of hard coatings for forming tools using the impact tester appears necessary, as pulsatory load occurs in the processes mentioned above. Further investigations of the wear tracks and interface zones when adhesion occurs are necessary. This may lead to better understanding of the tribological interactions and the reason for the different results which have been presented.
References [i] [2] Fig. 6. Wear track: TiAl(N)
coating
against
steel lOOCr6 sphere. [S]
results, but deep grooves on all coating surfaces, is not yet clarified.
[4]
[S]
4. Conclusion The results show how important it is to develop a coating geared to a particular application and to test it
B. Matthes, E. Broszeit and K.H. Kloos, Surf. Coat. Technol., 57 (1993) 97-104. K.H. Habig, Verschleiss und Hdrte van Werkstoffeen, Carl Hanser Verlag, Miinchen-Wien, 1980. 0. Knotek, R. Breidenbach, F. Jungblut and F. LBffler, Surf. Coat. Technol., 43144 (1990) 107-115. Toni Leyendecker, ijber neuartige Schneidwerkzeug beschichDissertation RWTH tungen auf Titan- und Aluminiumbasis, Aachen, 1985, 51-59. G. Hokannson and J.-E. Sundgren, Thin Solid Films, 153 (1987) 55-65.
Surface
and Coatings Technology 86-87 (1996)467-471
Tribological behaviour of Ti-Al-B-N-based
PVD coatings
S. Heck *, T. Emmerich, I. Munder, J. Steinebrunner Furtwangen Polytechnical University, Jakob-Kienzle-Stra$Ie 17 D-78054 VS-Schwenningen, Germany
Abstract PVD-coatings based on TiB, are expected to show high wear resistance and low tendency of adhesion on metal forming tools. Coating adhesion and morphology can be modified over a wide range by varying the content of nitrogen (NJ and the deposition parameters power and bias voltage. All coatings were deposited using commercial unbalanced magnetron equipment, the deposition was homogeneous in a volume of 400 x 400 x 400 mm’. Hipped and hot pressed TiB,-targets were used, nitrogen (N,) was added as gas, Ti and Al by a solid Ti-Al-target. The tribological behaviour was tested by a pin-on-disc wear test. The coatings investigated were TiB2, TiAIB(N), TiAl(N) and TiB,/TiAl(N). As counterpart in the pin-on-disc wear test, 6 mm diameter spheres of steel (lOOCr6), aluminium, brass and bronze were used. The experiments showed a non-uniform wear behaviour. For the combinations
TiAlB(N) and TiB? versus aluminium, a low wear volume of the coating and adhesive tendency was found. Brass led to abrasive wear on all coatings, whereas bronze showed a strong adhesive tendency on all tested coatings. Using a steel sphere the dominant wear mechanism was tribochemical oxidation. Keywords: Tribological
behaviour; Ti-Al-B-N-based
PVD coating; Wear mechanism; Pin-on-disc
1. Introduction
The tribological behaviour of PVD-coatings has an increasingly important position in cold, semi-hot and hot extrusion of steel and non-ferrous metals. A smooth surface together with a wear resistant coating results in higher productivity and longer life for modern tools. The standard forming tool made of cemented metal carbide, cold work steel and high speed steel has a high strength and impact strength, but the wear resistance on the surface is low. Over the last 10 years more manufacturers have been using coated tools in their production and so the use of PVD-coatings rate high. The process situation for forming tools varies from case to case and so for each particular application tailor-made coatings are required. Carbides, borides and nitrides of transition metals have been increasingly used for wear reduction in tools and machine components within the last few years [ 1). The resistance against abrasive wear is normally related to the hardness of the wear parts [2]. TiB, in particular is a stable, superhard and electrically conductive refractory material with a high melting point. This combination of properties makes TiBl an interesting prospect for a wide range of mechanical applications * Corresponding author. 0257-8972/96/$15.000 1996Elsevier Science S.A. All rights reserved PIZ SO257-8972(96)02987-k?
test
in an erosive, abrasive, corrosive or high temperature environment [3]. Advantages of TiAl(N) are the important physical and mechanical properties, including hardness, adhesion, toughness, wear resistance, chemical inertness and good thermal properties [4,5]. The coating system TiAlB(N) should combine the good properties of both TiB, and TiAI(N). The present study shows the wear properties of the coating systems against steel, aluminium, brass and bronze using a CSEM pin-ondisc-test.
2. Experimental details All coatings were deposited by means of a commercial Ceme Con CC800 magnetron sputtering apparatus with substrate bias on S-6-5-2 hardened (63HRC) high speed steel (1.3343 or BM2). All samples were mechanically polished (R,= 0.54 pm and R, =O.OSpm) and subsequently cleaned (hot-ultrasonic-alkaline cleaning, water rinsing, distillation rinsing, pressure-air drying) and sputter etched in a vacuum by argon ion bombardment. The samples were mounted in such a way that, while rotating around the horizontal axis of the vacuum chamber, the primary area to be coated was facing the target. Hipped and hot pressed TiB,-targets were used, nitrogen (NJ
468 Table 1 Conditions Counterpart
S. Heck et al./Surface and Coatings Technology 86-87 (1996) 467-471
for the pin-on-disc materials
the lowest critical load of 67 N on S-6-5-2, whereas the critical load of TiAl(N) was 118 N. The duplex coating TiB,/TiAl(N) and the TiAlB(N) coating had the same critical load of 112 N. The microhardness and thickness results are given in Table 2. The hardness was measured on the coated high speed steel samples. For example, the hardness of TiAl(N) (2059 HV,,05 on S-6-5-2) differs from what is normally seen for such coatings. The hardness of TiAl(N) coated cemented carbide (quality KlO) is 3400 HV0.05, which is in the range as described in the literature.
wear test Steel (lOOCr6), aluminium, brass and bronze 6mm 2N 500 m 14 mm 300 rev min-’ no 22.5-25.8”C 6.8-9.0%
Counterpart diameter Normal force Total sliding distance Radius of wear track Revolution speed Lubrication Temperature Relative humidity
was added as gas, Ti and Al by a solid Ti-Al-target. Typical sputter conditions, applied to the deposition process, were a d.c. power of 1925-3500 W (power/surface of 0.11-0.20 W mme2), a total gas pressure of 0.5-l Pa and an anode voltage of 100 V. The thickness was measured by CSEM calo test and optical microscopy, adhesion with the scratch test (Revetest CSEM). The hardness was measured by a Leitz microhardness tester using a Vickers diamond and 0.49 N load. The structure of the coating was investigated by means of scanning electron microscopy (SEM). Examinations of the tribological properties were performed with a CSEM pin-on-disc test. The sliding friction coefficient, the wear appearance and the volumetric wear of the TiB,, TiAlB(N), TiAl(N), TiB,/TiAl(N) coatings and the uncoated steel S-6-5-2 were measured against steel (lOOCr6), aluminium, brass and bronze spherical counterparts without any lubricant. The conditions for the pin-on-disc wear testing experiments are shown in Table 1. The PVD-process was controlled by optical emission spectroscopy.
3. Results and discussion 3.1. Critical loads offailure, hardness and thickness
A commercial CSEM scratch tester with a Rockwell C diamond, with a tip radius of 0.2 mm and a cone angle of 120”, was used. The load was O-200 N and the distance 10 mm at a speed of 1 mm s-r. During scratching, the friction force between diamond and coating was continuously monitored. Afterwards the results were verified by optical microscopy. The TiB2 coating showed Table 2 Hardness
and thickness
Hardness (HV,,,,r Thickness (urn)))
3.2. Volumetric wear of counterpart The pin-on-disc test showed, in the case of boron coatings, that the aluminium counterpart had a high volumetric wear. For example, TiB2 showed the highest volumetric wear. TiAlB(N) and the duplex coating TiB,/TiAl(N) have less tendency to friction against aluminium but the volumetric wear is twice as high as the TiAl(N) coating. When the coating was TiAlB(N), bronze showed the highest volumetric wear. TiB, and the duplex coating led to approximately the same volumetric wear as bronze. The volumetric wear caused by the coatings is shown in Fig. 1. TiAl(N) caused higher volumetric wear of bronze than the TiB, and the duplex coating, but TiAlB(N) caused the highest wear. When using brass as the counterpart, TiB2 caused the highest volumetric wear of the counterpart. With regard to lOOCr6, TiAl(N) caused the highest wear of the sphere. Comparing the boron coatings, TiAlB(N) caused the most volumetric wear. The uncoated sample S-6-5-2 led to high volumetric wear of aluminium, but boron coatings caused higher sphere volumetric wear. Bronze caused high volumetric wear of S-6-5-2, but with TiAl(N) and TiAlB(N) it was even higher. Uncoated samples caused the highest volumetric wear of brass. The wear of the counterparts correspond to the tribological behaviour. 3.3. Tribological behaviour and the determination of the friction coejicient p During measurement, the friction coefficient p of the sphere and the counterpart sample was determined. The friction coefficients and the tribological behaviour are
results TiAl(N)
TiB,
TiAlB(N)
TiB,/TiAl(N)
2059 4.2
1843 2.7
1758 4.1
1604 TiAl(N):
“Average of five measurements, base material bAverage of three measurements.
steel S-6-5-2.
1,5 TiB,: 1,7
S. Heck et al./Surface and Coatings Technology 86-87 (1996) 467-471
TiAI( N)
TiBP
TiAIB(N)
TiB2-TiAI(N)
uncoated S6-5-2
Coating system
Aluminium
Bronze
n Brass
Fig. 1. Volumetric wear of counterpart.
presented in Table 3. All measured friction coefficients were determined following stabilisation. The high friction coefficient resulted from the low relative humidity, 6.8-9.0%, without lubrication and a normal force of 2 N. Compared to its counterpart aluminium, TiBz showed low adhesion and low smoothing of the coating surface by high volumetric wear (see Fig. 2). The behaviour of
the duplex coating TiB,/TiAl(N) (TiB2 on the top) against all counterparts is similar to TiB2, with respect to the same friction coefficient. The tribological wear behaviour of TiB, against bronze resulted in strong adhesion with deep grooves on the coating surface (see Fig. 3). The wear of the TiAlB(N) coating against brass showed strong abrasion and grooves on the coating
Table 3 Tribological behaviour and friction coefficient of counterpart matching (friction coefficient p is given in parentheses’) Counter part
Coating system TM(N)
TiB2
TiAlB(N)
TiBJTiAl(N)
uncoated S 6-5-2
Aluminium
low abrasion, Alparticles on coated surface (0.8 1)
low adhesion, low smoothing of coated surface (0.94)
Al-particles, low adhesion, smoothing of coated surface (0.91)
low adhesion, smoothing of coated surface (0.90)
strong adhesion, tribochemical reactions, surface grooves (0.82)
Bronze
strong adhesion, particles, low grooves on coated surface (0.96)
strong adhesion, deep grooves on coated surface (0.50)
strong adhesion, no surface grooves (0.99)
low adhesion, deep grooves on coated surface (0.48)
strongest surface adhesion, tribochemical reactions (0.63)
Brass
low abrasion, deep grooves on coated surface (0.17)
low abrasion, deep grooves on coated surface (0.20)
strong abrasion, grooves on coated surface (0.10)
strong abrasion, grooves on surface (0.15)
strongest abrasion, tribochemical reactions, strong surface grooves (0.38)
lOOCr6
no tribochemical reactions, particles, low adhesion on coated surface (0.84)
strong tribochemical reactions on coated surface (0.75)
low adhesion, particles, no tribochemical reactions on coated surface (0.78)
low tribochemical reaction on coated surface (0.75)
strongest tribochemical reactions, abrasion, surface grooves (0.94)
“Average of three measurements.
S. Heck et al. jSurface
470
Fig. 2. Wear track: TiB, coating
against
Fig. 3. Wear track: TiB, coating
aluminium
against
bronze
and Coatings Technology 86-87 (1996) 467-471
sphere.
sphere.
surface (see Fig. 4), but a low adhesion of brass particles was found. TiAlB( N) showed no tribochemical reactions on the coating surface against IOOCr6 (see Fig. 5). TiAl(N) against a lOOCr6 sphere showed no tribochemical reactions and low adhesion on the coated surface
Fig. 4. Wear track: TiAIB(N)
-. Pig. 5. Wear track: TiAlB(N)
coating
coating
against
against
brass sphere.
steel lOOCr6 sphere.
(see Fig. 6). Brass showed high abrasion in all tribological tests. lOOCr6 without lubrication, tends to lead to tribochemical reactions. The reason why the friction coefficient of brass without lubrication has such low
S. Heck et al./Surface and Coatings Technology 86-87 (1996) 467-471
471
against various counterparts. In the case of concrete applications, e.g., cold, semi-hot and hot extrusion and interrupted-cut machining without lubrication, further tests must be undertaken to find the suitable coating. The pin-on-disc test showed a wide range of tribological behaviour. Up to now TiB, seems to be most qualified to transform and machine aluminium. TiAlB(N) promises to be a suitable coating to transform brass. The results show that TiAl(N)-coatings seems to be qualified for the transforming of steel. The characterisation of hard coatings for forming tools using the impact tester appears necessary, as pulsatory load occurs in the processes mentioned above. Further investigations of the wear tracks and interface zones when adhesion occurs are necessary. This may lead to better understanding of the tribological interactions and the reason for the different results which have been presented.
References [i] [2] Fig. 6. Wear track: TiAl(N)
coating
against
steel lOOCr6 sphere. [S]
results, but deep grooves on all coating surfaces, is not yet clarified.
[4]
[S]
4. Conclusion The results show how important it is to develop a coating geared to a particular application and to test it
B. Matthes, E. Broszeit and K.H. Kloos, Surf. Coat. Technol., 57 (1993) 97-104. K.H. Habig, Verschleiss und Hdrte van Werkstoffeen, Carl Hanser Verlag, Miinchen-Wien, 1980. 0. Knotek, R. Breidenbach, F. Jungblut and F. LBffler, Surf. Coat. Technol., 43144 (1990) 107-115. Toni Leyendecker, ijber neuartige Schneidwerkzeug beschichDissertation RWTH tungen auf Titan- und Aluminiumbasis, Aachen, 1985, 51-59. G. Hokannson and J.-E. Sundgren, Thin Solid Films, 153 (1987) 55-65.