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Study on Tribological Characteristics of
Plasma Carburized Titanium Alloy Gear under
Unlubricated and Water Lubrication Condition
Kindai University
Kosaku Kita
Contents
Introduction P1
Gear specification P3
Examination device P6
Experimental method P7
Test result P9
Raman spectroscopic analysis P13
Conclusion P15
Introduction
Effect of the lubricating oil
• Preventing seizure or wear
• Reduction of friction loss
• Cooling effect etc.
The environment that using lubricating oil is difficult • Special environment
(In space, Semiconductor manufacturing plant)
• The machine which is used under water
The nature with the seizure-resistance, wear-resistance,
and self-lubricity are important
under such as environment
1/15
In general, when gear device drive, lubricating oil are used
Lubricating oil is easily to evaporate
by low pressure under vacuum
Introduction
The previous method
・Plating processing
・Solid lubrication film
・Diamond-like Carbon
・Plastic gear
Defect
・Weak in adhesion with
base-metal
・Strength is low
This study
We were paying attention to plasma carburizing which has
been carried out as a seizure measures of the screw.
By treating the plasma carburized to the gear, it is intended
to perform the verification or which can be operated under
unlubricated and water lubrication.
As normal method when lubricating oil
could not been used for gear device
2/15
Introduction
Gear specification
Examination device
Experimental method
Test result
Raman spectroscopic analysis
Conclusion
Gear specification As gear material, choosing Ti-6Al-4V
To perform plasma carburized we expected to improve disadvantage
○ To light weighting
○ Superior corrosion resistance
× Easy to seizure
× Low wear resistance
Advantage Disadvantage
Specific gravity
• Ti-6Al-4V : 4.43 g/cm3
• SUS316 : 7.98g/cm3
3/15
CH4
Injection gas(methane) in furnace
↓Generating grow discharge
Gas become ion
↓Carbon ion collision object
Carbon atoms penetrate through and
diffuse the surface of processed object
↓
Hardened layer is formated
CH4
CH4
CH4 C+
C+
C+
H2
H2
H2 H2
Curbrizing furnace (Anode)
Processed object
(Cathode)
H2
C+
C+
Plasma curbrized processing ・Plasma curbrized
Technique to reform the surface by letting carbon invade in the
metal surface.
Hardening surface only
combine Wear-resistance
Toughness
4/15
Plasma carbrized process
Gear specification
Driving gear Driven gear
Module [mm] 5
Number of teeth 20
Pressure angle [deg] 20
Pitch diameter [mm] 100
Tip diameter [mm] 110
Center distance [mm] 100
Face width [mm] 5 10
As gear material, choosing Ti-6Al-4V
Plasma carburized Ti-6Al-4V gear (specific gravity : 4.43g/cm3)
The gears are numbered 1 to 4,
the gear pairs always conduct
the same teeth.
Left tooth flank
Unlubricated
Right tooth flank
Water lubrication
○To light weighting
○Superior corrosion resistance × Easy to seizure
× Low wear resistance
5/15
Introduction
Gear specification
Examination device
Experimental method
Test result
Raman spectroscopic analysis
Conclusion
(Controlling rotary speed)
Examination device
Motor Torque meter
Test gear
Powder brake
Digital torque indicator
Loadin torque in an
examination gear
6/15
Introduction
Gear specification
Examination device
Experimental method
Test result
Raman spectroscopic analysis
Conclusion
0
100
200
300
400
500
600
0 100 200 300 400 500 600 700 800
Conta
ct e
ffic
iency
[M
Pa]
Sliding velocity [mm/s]
High speed test (80rpm)
Low speed test (20rpm)
Previous study
PV curve
Limit permissible curve
PV diagram
bL
WP
2
TnnV )(30
21
Load torque :15Nm
We calculated contact pressure and sliding speed from previous
study and made a PV diagram to perform examination on test condition
at the same level as past under unlubricated and water lubrication.
Rotational speed
n1= 20rpm
80rpm
Examination condition
Seizure
Friction and wear increase
High load
7/15
Experimental method
Room temperature : 20℃ Load torque : 15Nm
Rotational speed : 80rpm
Lubricated condition : Unlubricated / Water lubrication
Input and output torque
Gear temperature
Surface roughness of the gear tooth surface
Tooth profile and tooth trace
Experimental condition
Measurement item
Every 200Cycles
Every 2000Cycles
8/15
Introduction
Gear specification
Examination device
Experimental method
Test result (Unlubricated)
Raman spectroscopic analysis
Conclusion
Appeared damage on whole contact surface
Tooth surface after 20000cycles
(Unlubricated)
Teeth number 2 Teeth number 1
Teeth number 3 Teeth number 4
0 cycle
Kept good surface condition
There were good tooth and
damaged tooth in
after 20000 cycles
9/15
As a comparison, efficiency of low speed test is shown in the same graph
90
92
94
96
98
100
0 4000 8000 12000 16000 20000
Tra
nsm
issi
on e
ffic
iency
[%
]
Total number of rotation [cycles]
20rpm 80rpm
Transmission efficiency
(Unlubricated)
96.6%
Ti-6Al-4V (80rpm)
Ti-6Al-4V (20rpm) Average
95.2%
Result in high efficiency
Efficiency of high speed test was lower than low speed test,
so it was seen influence by high load
10/15
Introduction
Gear specification
Examination device
Experimental method
Test result (Water lubrication)
Raman spectroscopic analysis
Conclusion
Tooth surface after 20000cycles
(Water lubrication)
Teeth number 1
Teeth number 4 Teeth number 3
Teeth number 2
0 cycle Most damaged
surface
There are a little damage on tooth surface, the damage were less than unlubricated
11/15
95
96
97
98
99
100
0 4000 8000 12000 16000 20000
Tra
nsm
issi
on
eff
icie
ncy
[%
]
Total number of rotation [cycle]
20rpm 80rpm
Transmission efficiency
(Water lubrication)
98.0%
Ti-6Al-4V (20rpm)
Ti-6Al-4V (80rpm)
The big difference was not seen in rotational speed.
Water has lubricating effect on this condition
Average
98.1%
Plasma carburized Ti-6Al-4V gears were good results.
So, we investigated surface them
12/15
Introduction
Gear specification
Examination device
Experimental method
Test result
Raman spectroscopic analysis
Conclusion
Test peaces were analysed
Raman spectroscopic analysis
Glassy carbon film(GLC) was formed on the surface of the
Ti-6Al-4V alloy plasma carburizing.
Glassy carbon
Ti-6Al-4V
A wave pattern of the glasscy carbon resembles Ti-6Al-4V
GLC have property of high mechanical strength and
self-lubricating. So it is considered that plasma
carburizing Ti-6Al-4V gears shown good results.
13/15
Raman spectroscopic analysis
100μm
Wear parts Non-wear parts
Ti-6Al-4V
100μm
100μm
14/15
Cut teeth after examination analysed three spot
Raman spectroscopic analysis
100μm
Wear parts
Non-wear parts
Ti-6Al-4V
100μm
100μm
Glassy carbon is still left on the surface of wear parts,
or a property of Ti-6Al-4V changed by plasma carburizing.
14/15
400
500
600
700
800
900
1000
800 1000 1200 1400 1600 1800 2000
Int
Raman shift
Wear parts
Non-wear parts
Cut section
[cm-1]
Introduction
Gear specification
Examination device
Experimental method
Test result
Raman spectroscopic analysis
Conclusion
Conclusion
Glassy carbon film is formed by plasma carburizing on Ti-6Al-4V.
The plasma carburizing gear can run in high transmission efficiency
and a good tooth surface state under unlubricated and water
lubrication.
The difference with rotational speed was uncommon by the water
lubrication.
The plasma carburizing is effective in driving under unlubricated
and the water lubrication.
Because a high effect is provided by the Ti-6Al-4V alloy,
we can expect in particular the light weighting of the gear device.
15/15