24th IRG-OECD Meeting, October 16-17 2003, Portoroz, Slovenia
FRICTION AND WEAR PROPERTIES OF CNX COATINGS IN THE FLOW OF N2 GAS Koji Kato, Shin Toyokawa, Koshi Adachi, Boyko Stoimenov Tribology Laboratory, Tohoku University, Sendai, Japan
N2
CNx Si3N4 Si3N4
CNx
β-C3N4 C N
[A. I. Liu, M. L. Cohen, 1989]
Past works on CNx coating and N2 lubrication Sliding speed: 4 mm/s
CNx coating on Si wafer
Load
Evacuation
44.0-140.6mN Strain gauge Si3N4 ball
N2 Ar Air
Vacuum chamber
[N. Umehara, Sato, K. Kato 1997] 0.5 Pin : Si N ball (r=4.0mm, R 3
4
Friction Frictioncoefficient coefficient, µμ
Disk : 100 nm CNx / Si (R 0.4
0.3
max
max
= 15 nm)
= 1~3 nm)
Normal load : 100 mN Maximum contact pressure : 200 MPa Sliding velocity : 4 mm/s
0.36
Si3N4
240 friction cycles
CNx
Si Wafer 0.2
0.16
0.1
0.05 0.009 0
Air 5
(10 Pa)
Vacuum -4
(2x10 Pa)
N 2
0.03
CO 2 4
(7.4x10 Pa)
O 2
[N. Umehara,M.Tatsuno, K. Kato, 1999]
Friction coefficient μ μ Friction coefficient
0.20
Disk : a-CNx on Si (t=100nm) Ball : Si3N4 (r=4.0mm) Normal load : 125-132mN mm/s-3m/s Slidnig speed : 44.2x10
0.152
0.15
0.10
0.081 Si3N4
0.05
0
CNx
0.007
Si Wafer
0
1
2
3
4
5
6
1044Pa Pressure of N 2 ,P,x x10 Pa
7
8
Air
X-Z stage
Spring
N2 gas Inner diameter 4.5 mm
Strain gages Si3N4 ball
Disk
Si3N4 CNx Si-wafer
Ball-on disk tester
Frictioncoefficient, coefficient μ Friction μ
[K. Adachi, K. Kato, Ueno, 2000]
1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
N2
0 l/min
N2
1.2 l/min
4.8 l/min
Dis k: CNx(100nm)/S i3 N4 P in: S i3 N4 ba ll (r=4 mm) Norma l loa d: 200 mN Rota ry s pe ed: 250 rpm(0.4 m/s ) Air Air
0
2
4
6
8
10
Number of friction cycles x103 Number of cycles ×103N, cycles
12
Air Spring
N2
N2 gas
N2 gas
Inner φ 4.5mm
Si3N4 ball
Test piece
10 mm
N2 gas φ
[K. Adachi, K. Kato, Ueno, 2000] 10 mm
Friction coefficient,
0.25 0.2 0.15 0.1
Coating: 100n m CNx Substrate: Si 3 N 4 Ball: Si 3 N 4 (r = 4 mm) Normal load: 200 mN Rotatrypeed: 250 rpm Flow rate: 3.6 l/min
N2 gas φ
Air
0.05 0 0
45
90
135
Blow angle of N2 gas φ, degree
180
[K. Adachi, K. Kato, Ueno, 2000] 0.3 Disk: CNx(100nm)/Si3N4,SiC Pin: Si3N4 ball (r=4mm) Normal load: 200mN Rotary speed: 250rpm
Friction coefficient, μ μ
0.25
Air
0.2
0.15 0.1
0.05 0 0
2
4
6
8
Flow rate of N2 gas Q, l/min
10
12
What is the best combination among Si3N4/CNx , CNx/CNx and C/C? N2 Si3N4
C-coating Si3N4
CNx
Si3N4
C-coating
Si3N4 N2
CNx Si3N4
N2
Ar CNx
O2
CO2
Air
Si3N4
Is N2 gas blow better than Ar, O2, CO2 or open air for lubricating CNx/CNx contact?
Si3N4 substrate
Carbon (Evaporated)
N ion (mixing)
Carbon target
Electron beam
Deposition conditions Target Evaporation
5, 10, 20, 30, 50 Å/s
Coating speed N ion beam
Mixing
Pressure
Carbon : 99.999 %
Acc. voltage
1.5 kV
Current density
90 μA/cm2
Gas flow
N2: 3.0 SCCM *
Background
< 2.0×10-4 Pa
Operating
7.1×10-3 Pa
Substrate
Si3N4
Coating thickness
about 400nm
Rotation speed
4 rpm
N ion beam Sputter cleaning
Acc. Voltage
1.5 kV
Current density
100 μA/cm2
Gas flow
N2: 3.0 SCCM *
Duration
5 minutes
*SCCM: Standard Cubic Centimeter per Minute
The surface of CNx coating on Si3N4 substrate disk
The surface of CNx coating on Si3N4 substrate ball
5 μm
Si3N4 ball
100 μm
5 μm
CNx coated Si3N4 ball thickness : 400nm
100 μm
Hardness of CNx and C coatings 45
Indentation hardness H, GPa
40 35
CNx and C on Si3N4 (t=400nm) Maximum indentation load : 980μ N Maximum indentation depth : 50-64nm
30 25 20 15 10 5 0 5Å/s Å/s
10Å/s Å/s
20Å/s Å/s
30Å/s Å/s
50Å/s Å/s
C 20Å/s Å/s
Evaporation speed of CNx and C coating Ve, Å /s
Si3N4/CNx
vs.
CNx/CNx
N2 Si3N4 Si3N4
CNx
N2
CNx Si3N4 Si3N4
CNx
Friction in N2 gas blow CNx / CNx sliding
Si3N4 / CNx sliding 0.6
0.6
Disk : CNx(Ra=0.025μ m) on Si3N4 (t=400nm) Ball : Si3N4 (r=4.0mm) Load : 400mN Maximum contact pressure : 517MPa Sliding speed : 0.2 m/s 2 Gas blow rate : 2.10 cc/mm s Gas blow distance : 10mm Gas blow start cycle : 100 cycles Hv(CNx) : 28.8GPa
0.4
0.5
Friction coefficient μ
Friction coefficient μ
0.5
Disk : CNx(Ra=0.025μ m) on Si3N4 (t=400nm) Ball : CNx coated Si3N4 (r=4.0mm) Load : 400mN Maximum contact pressure : 517MPa Sliding speed : 0.2 m/s Gas blow rate : 2.10 cc/mm2s Gas blow distance : 10mm Gas blow start cycle : 100 cycles Hv(CNx) : 28.8GPa
0.4
No blow (in air) N2 gas blow
0.3
0.3
0.2
0.2
No blow (in air) N2 gas blow
0.1
0.1
0
0 0
2000
4000
6000
8000
10000
0
2000
4000
6000
8000
Number of cycles N, cycles
Number of cycles N, cycles
CNx / CNx sliding : low and stable friction faster than CNx / Si3N4 sliding μ=0.03 (blow) μ=0.15 (in air)
10000
Wear of ball in N2 gas blow Friction coefficient μ
3.5
Disk : CNx(Ra=0.025μm) on Si3N4 (t=400nm) Ball : Si3N4 (r=4.0mm) Load : 400mN Maximum contact pressure : 517MPa Sliding speed : 0.2 m/s Gas blow rate : 2.10 cc/mm2s Gas blow distance : 10mm Gas blow start cycle : 100 cycles Hv(CNx) : 28.8GPa
0.3
0.2
0.1
3 2.5 2 1.5 1
Friction coefficient μ
4
3
4.5 0.4
0.5
-5
5
mm
Friction coefficient μ
5.5
Wear volume of ball
0.5
6
Disk : CNx(Ra=0.025μm) on Si3N4 (t=400nm) Ball : CNx coated Si3N4 (r=4.0mm) Load : 400mN Maximum contact pressure : 517MPa Sliding speed : 0.2 m/s Gas blow rate : 2.10 cc/mm2s Gas blow distance : 10mm Gas blow start cycle : 100 cycles Hv(CNx) : 28.8GPa
0.4
0.3
0
4000
8000
12000
Number of cycles N, cycles
0 20000
16000
5
4.5 4 3.5 3
0.2
Friction coefficient μ
2.5
Wear volume of ball
2 1.5
0.1
1
0.5 0
5.5 -5
6
Wear volume of ball V, x10
0.6
CNx / CNx sliding
0.6
0.5 0
0 0
μ=0.03 (blow) μ=0.15 (in air)
4000
8000
12000
16000
Number of cycles N, cycles
at 500~20000cycles
at 500~20000cycles
Ws,s = 5.89x10-8 mm3/Nm
Ws,s = 1.13x10-8 mm3/Nm
20000
Wear volume of ball V, x10 3 mm
Si3N4 / CNx sliding
C/C
vs. C-coating
Si3N4 Si3N4
CNx/CNx
N2
C-coating
N2
CNx Si3N4 Si3N4
CNx
0.6
Disk : CNx(Ra=0.025μ m) on Si3N4 (t=400nm) C(Ra=0.035mm) on Si3N4 (t=400nm) C/C with N2 N2 gas blow Ball : CNx, C coated Si3N4 (r=4.0mm) N2 gas blow CNx/CNx with N2 Load : 400mN Maximum contact pressure : 517MPa Sliding speed : 0.2 m/s Gas blow rate : 2.10 cc/mm2s Gas blow distance : 10mm Gas blow start cycle : 100 cycles Hv(CNx) : 28.8GPa
Friction coefficient μ
0.5
0.4
0.3
0.2
0.1
0 0
2000
4000
6000
Number of cycles N, cycles
8000
10000
C-coated Si3N4 ball
Sliding direction of counterface
100 μm
C-coated Si3N4 disk
Sliding direction of disk
100 μm
After sliding of 10000 cycles with N2 gas blow in air
CNx coated Si3N4 ball Sliding direction of counterface
100 μm CNx coated Si3N4 disk
Sliding direction of disk
100 μm
After sliding of 10000 cycles with N2 gas blow in air
CNx-coated Si3N4 ball
C-coated Si3N4 ball Hv = 33 GPa
Hv = 28 GPa
Sliding direction of counterface
100 μm
C/C 6.42x10-7 mm3/Nm
After CNx / CNx 10000 cycles 9.31x10-9 mm3/Nm
Effect of Gases of N2, Ar, CO2 and Air on friction and wear of CNx / CNx
N2
CNx Si3N4 Si3N4
CNx
Ar
O2
CO2
Air
0.6 Disk : CNx(Rmax =0.025mm) on Si3N4 (t=400nm) Ball : CNx coated Si3N4 (r=4.0mm) Load : 400mN Maximum contact pressure : 517MPa Sliding speed : 0.2 m/s
Friction coefficient μ
0.5
0.4
N2 gas blow O2 gas blow Ar gas blow CO2 blow Air
2
Gas blow rate : 2.10 cc/mm s Gas blow distance : 10mm Hv(CNx) : 28.8GPa
0.3
0.2
0.1
0 0
2000
4000
6000
Number of cycles N, cycles
8000
10000
(a) N2 blow
(b) Argon blow
(d) O2 blow
(c) CO2 blow
(e) Air (No blow) Sliding direction of counterface
After 10 000 cycles
Sliding direction of disk
100μm
0.4
6
5 4.5
Disk : CNx(Ra=0.025mm) on Si3N4 (t=400nm) Ball : CNx coated Si3N4 (r=4.0mm) Hv(CNx) : 28.8GPa, Load : 400mN Maximum contact pressure : 517MPa Sliding speed : 0.2 m/s
0.35
0.3
2
4 3.5 3 2.5
Gas blow rate : 2.10 cc/mm s Gas blow distance : 10mm Gas blow start cycle : 100 cycles Air : 20℃，RH=30%
0.25
0.2
Specific wear rate Ws
μ Stable friction coefficient μ 0.15
2
0.1
1.5 1
0.05 0.5
0
0 blow NN2 2 blow
Ar blow
CO2 blow
Blow gas
O2 blow
Air (No blow)
Friction coefficient
Specific wear rate of ball Ws. x10-7 mm3/Nm
5.5
Surface analysis
CNx Evaporation speed 20Å /s O2 gas blow
Intensity, counts
In itial We ar tr ac k
D-band G-band
800
1000
1200
1400
1600
Raman shift, cm-1
1800
2000
CNx on Si3N4 disk after 10000 sliding cycles in blows of Nitrogen , Oxygen, and in air. W = 400 mN, V = 0.2 m/s
Initial surface
In Oxygen blow
In Nitrogen blow
In Air
Raman spectra of initial surface and wear track of CNx
1200
1400
1600
Raman shift, cm
1800
2000
800
1400
1600
1800
800
2000
G-band
1400
1600
Raman shift, cm-1
N2 gas blow
1800
2000
1000
1200
1200
1400
1600
Raman shift, cm
1800
2000
-1
CNx coated Si3N4 ball Evaporation speed 20Å /s No blow
D-band
800
1000
-1
Initial Wear track
Intensity, counts
Intensity, counts
Ball
D-band
1200
1200
D-band G-band
CNx coated Si3N4 ball Evaporation speed 20Å /s O2 gas blow
Initial Wear track
1000
1000
Raman shift, cm
CNx coated Si3N4 ball Evaporation speed 20Å /s N2 gas blow
800
Intensity, counts
D-band G-band
-1
Initial Wear track
G-band
1400
Initial Wear track
Intensity, counts
1000
Initial Wear track
Intensity, counts
D-band G-band
800
CNx Evaporation speed 20Å /s No blow
CNx Evaporation speed 20Å /s O2 gas blow
Initial Wear track
Intensity, counts
Disk
CNx Evaporation speed 20Å /s N2 gas blow
1600
Raman shift, cm-1
O2 gas blow
1800
2000
D-band
800
1000
1200
G-band
1400
1600
Raman shift, cm-1
In Air
1800
2000
N2 gas blow
O2 gas blow
Sliding direction of counterface
100μm
CNx coated Si3N4 ball Evaporation speed 20Å /s N2 gas blow
CNx coated Si3N4 ball Evaporation speed 20Å /s O2 gas blow
D-band
800
1000
1200
G-band
1400
Initial Wear track
Intensity, counts
Intensity, counts
Initial Wear track
1600
Raman shift, cm-1
1800
2000
D-band
800
1000
Initial surface Wear track
1200
G-band
1400
Raman shift, cm
1600 -1
1800
2000
XPS analysis of the initial surface and wear track after 10000 cycles Concentrationofofbonds bonds of of C C-atoms in Concentration atom on C andCNx CNxcoating, coating % C, %
100% 90% 80% 70% 60% 50% 40%
C-N C-N or or C-O C-O C=N C=N C=C C=C or or C-C C-C
30% 20% 10% 0%
Initial surface
Wear track
Wear track
Wear track
N2 blow
O2 blow
In air
Concentration of of bonds bonds of of NN-atoms Concentration atom onin C andCNx CNxcoating, coating% C, %
XPS analysis of the initial surface and wear track after 10000 cycles 100% 90% 80% 70% 60% 50% 40% 30%
N-O N-O N=C N=C N-N N-N or or N=N N=N N-C N-C
20% 10% 0%
Initial surface
Wear track
Wear track
Wear track
N2 blow
O2 blow
In air
In N2 blow
Conclusions
μ
Ws, mm3/N.m
1. The combination of CNx/CNx gives lower value of the friction coefficient and wear rate, than the combination of CNx/Si3N4 and C/C in the blow of N2 gas in open air.
CNx/CNx
0.03
1~3 x10-8
CNx/Si3N4
0.03
5.9 x10-8
C/C
6.4 x10-7 0.05 ~0.15 CNx/CNx
2. For the contact of CNx coating against CNx coating N2 gas blow in open air, gives lowest friction coefficient and wear rate among the gases N2, Ar, CO2, O2 and lower than in open air.
Blown gas
μ
Ws, mm3/N.m
N2
0.03
3.0 x10-8
Ar
0.05
4.0 x10-8
CO2
0.05
5.2 x10-8
O2
0.17
5.4 x10-7
Air
0.19
3.5 x10-7
