Study on Tribological Characteristics of Plasma Carburized ... · Study on Tribological...

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


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


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)


Conclusion

Appeared damage on whole contact surface

Tooth surface after 20000cycles

(Unlubricated)

Teeth number 2 Teeth number 1


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)


Conclusion

Tooth surface after 20000cycles

(Water lubrication)

Teeth number 1


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


Conclusion

Test peaces were analysed


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


100μm

Wear parts Non-wear parts

Ti-6Al-4V

100μm

100μm

14/15

Cut teeth after examination analysed three spot


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


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

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