LOW FRICTION SELFLUBRICATING COATINGS FOR …

Technical University of Lodz

Institute of Materials Science

& Engineering, Lodz, Poland

LOW FRICTION SELFLUBRICATING COATINGS FOR

ENVIRONMENTALLY FRIENDLY AVIATION & CARS

PolSCA MEETING: Environementally friendly cars & road vehicles, Brussels, 12.12.2011

B.G. Wendler

Head of Coatings’ Engineering Department

of Mechanical Engineering Faculty of TUL

ENVIRONMENTALLY FRIENDLY AVIATION & CARS

by

PolSCA MEETING: Environementally friendly cars & road vehicles, Brussels 12.12.2011

TUL was involved in two Projects concerning low

friction coatings for car industry and aviation:

-KomCerMet (coposites and nanocomposites for aviation and car

industry) financed in the frame of the European Regional

Development Fund ERDF (scope 2007 – 2013)

-POWERFUL (POWER train for Future Light duty vehicles) financed

in the fame of 7th Framework Programme Sustainable Surface

Transport Research (scope 2007-2013 and TARGET: CO2 emission Transport Research (scope 2007-2013 and TARGET: CO2 emission

reduction to 95g/km in 2020)

The following groups of nanocomposite low friction, selflubricating

coatings were proposed by TUL:

I. Carbon based nanocomposite coatings nc-MeC/a-C(:H)

type nc-WC/a-C:H or ncCrC/a-C:H or nc-TiC/C:H

II. MoS2 based (directly or in the frame of a duplex treatment based on

proprietary gas sulfonitriding®) for medium temperatures

III. Ag2MoO4 based low friction coatings for high temperatures


Solidcontact

Boundary lubrication

Mixed lubrication

Hydrodynamic lubrication

Friction coefficient µ

Increasing speed

0.01

0.1

Legend

� - Valve train

� - Liner - piston skirt

� - Liner – piston ring

� - Liner – shaft bearing

without coating


Friction coefficient

Lubricating film thickness λ

0.001

0.01 0.1 1 10

��

��

Modified Stribeck chart on the effect increasing speed on friction coefficient of lubricated

tribological contacts

with low friction

coating

Nanocomposite WC1-x/a-C:H coating deposition

2

1

4 5

7

3

24

5

6

PVD chamber for coatings’ deposition

Front

view

Top

view


1

1

1- magnetron W; 2- magnetron C; 3- magnetron C; 4- magnetron C; 5- specimens;

6- auxiliary RF electrode; 7- rotary table with pulsed bias.

30 P1

[GPa]

0 500 1000

150

300

Nanomodulus En

[nm]

P3

P2

P4

P1

Dynamic nanomodulus E

n [GPa]

Indenter displacement in depth of the specimen

nc-WC/a-C:H

NANOMODULUS


0 500 1000

15

30

Nanohardness Hn

[nm]

P3

P2

P4

P1

Dynamic nanohardness H

n [GPa]

Indenter displacement in depth of the specimen

& NANOHARDNESS

COATING’S FRACTURE MORPHOLOGY

nc-WC/a-C:H coating


nc-WC/a-C:H coating

Si(100) silicon substrate

COATINGS’ ROUGHNESS

P1 P2Ra=0.19nm Ra=0.29nm


P3 P4Ra=0.61nm Ra=1.35nm

TEM, HRTEM & SAED

COATING’S STRUCTURE


5 nm

0,1

0,2Test specimen from hardened and tempered

VANADIS 23 HS steel deposited with nc-WC/a-C:H

µµµµ = 0.075

Dry friction coefficient µµ µµ

DRY FRICTION COEFFICIENT


0 500 10000,0

Dry friction coefficient

Friction path [m]

Dry friction coefficient in a ball-on-disk test of a nc-WC/a-C:H coating on hardened

VANADIS 23 HS steel against a steel ball 5 mm diam under a load of 10 N at ambient

temperature and RH = 60%

DRY FRICTION & WEAR RESISTANCE (cont.)

Image from a confocal microscope of a weartrack on the surface of the nc-WC/a-C:Hcoating on Vanadis 23 HS steel after 1.6 E+4friction cycles of a ball-on-disk test againsta steel bearing ball 5 mm diam. under 1.5 GPaload. Linear velocity 0.1 m/s; temperature250C; RH = 60 %; radius of curvature of thefriction path 10mm.


friction path 10mm.

� Wear rate Vw ~ 1⋅⋅⋅⋅E-16 m3/J

or

a wear resistance coefficient

WR �� 3 GJ/g

ADHESION OF THE nc-WC/a-C:H COATING

TO DIFFERENT SUBSTRATES


Results of the Daimler-Benz adhesion test of a nc-WC/a-C:H coating 2 µm thick on a Vanadis 23 HSS steel (a) and on a hardened Ti6Al4V alloy (b): 1st class (HF=1, the best one) from six different grades.

A proprietary treatment (P-392505) has been applied first to the steel

substrate in order to improve adhesion and lubricating properties of a

Characterization of MoS2TiW coating


substrate in order to improve adhesion and lubricating properties of a

MoS2TiW low friction coating. As a result, a significant decrease of a

friction and wear coefficients during dry friction against a ZrO2 ball 5

mm diam. was achieved and, simultaneously, an important increase of

the adhesion the steel substrate took place.

MoS2(Ti,W) characterization (cont.)

SINTERED HIGH SPEED STEEL Vanadis 23

DEPOSITION MoS2TiW COATING

HEAT TREATMENTLP NITRIDING

NitroVac®

SULFONITRIDING

Sulfonit®


Effect of a primary heat or surface treatment of the HS

steel substrate on the adhesion of the MoS2(Ti,W) coating

MoS2TiW characterization (cont.)

3

6

1

2

45

1

µ


Dry friction coefficient µµµµ of a ZrO2 ball 5 mm diam. under a load of 10 N (~1.5 GPa) against a disk from Vanadis 23 HS steel without any treatment (1),after sulfonitriding (2,3) and after sulfonitriding with a subsequentMoS2(Ti,W) coating (4,5,6).

0 200 400 600 800 1000

64

5

00 Friction path 1000 m

0,04

0,08MoS

2TiW/ZrO

2 ball 5 mm diam.

Load 10 N

µµµµ=0,029

Dry friction coefficient µµ µµ

MoS2TiW characterization (cont.)


Dry friction coefficient µµµµ of a ZrO2 ball under a load of 10 N (~ 1.5 GPa)against a sulfonitrided disk from Vanadis 23 HS coated with a 3µµµµ thickMoS2(Ti,W) layer

0 500 1000

µµµµ=0,029

Dry friction coefficient

Friction path [m]

*E-15 m3/J10

Vw00

1

Bar chart of a volume wear rate Vwof a Vanadis 23 HS steel after

different surface treatments withor without MoS2(Ti,W) coating

during dry friction against aZrO2 ball 5 mm diam. at a

temp. 25 0C, under a load of 10 N(~1.5 GPa) and a linear velocity 0.1 m/s in a ball-on-disk test.

Legend:


0.1

0.01

Legend: -without any coating temperedor nitrided or sulfonitrided

-with a supplementary MoS2TiW coating

Ew��60MJ/g

Tempered Nitrided Sulfonitrided®+MoS2TiW

Duplex treatment based on MoS2TiW coating


Falex journal and vee-blocks geometry – linear friction couple



Heat treated - H Catastrophic wear

High friction, Oxidation


Gas sulfonitriding + MoS2TiW coating – S+C

Very low wear, no oxidation

1800

2400

3000

3600

300

350

400

450

500

550

600

Loa

d [

N]

ela

tive

mo

me

nt

of

fric

tio

n f

orc

e [

%]

N

N+C

Load curve (right scale)

H



0

600

1200

0

50

100

150

200

250

0 100 200 300

Loa

d [

N]

Re

lati

ve

mo

me

nt

of

fric

tio

n f

orc

e [

%]

Time [s]

S+C

H+C

S

Ag2MoO4 selflubricating coatings

for friction couples

working at high temperatures


working at high temperatures

a) b)


SEM SE images of a fractal-type morphology composed of greater and smaller clusters

on the surface of a 2.5 µm thick Ag10.8Mo22.7O64.4 nanocomposite coating magnetron

sputtered onto a flat Si substrate (a) and of a fracture of the same coating with a well

developed columnar morphology (b). The mean diameter of the smaller clusters in Fig.

(a) is equal to ~20 nm. Own research together with W. Pawlak, Ph.D., Eng. and M.

Makowka, M.Sc., Eng. in the frame of the POIG project KomCerMet co-funded by DG of

the European Commission.

300

600

Si / silicon ICDD 05-0565

Ag / silver ICDD 04-0783

Ag10.8Mo

22.7O

64.4 coating

on a monocrystalline SiIn

ten

sity [

arb

. u

nits]


60 120

0

Inte

nsity [

arb

. u

nits]

Co Ka 2Θ [deg]

XRD diffraction pattern of the Ag10.8Mo22.7O64.4 nanocomposite coating from former

figur as deposited (without any subsequent annealing). Nanocrystallites of Ag phase in

an amorphous MoO3 matrix. Own research together with W. Pawlak, Ph.D., Eng. and M.

Makowka, M.Sc., Eng. in the frame of the POIG project KomCerMet co-funded by DG of

the European Commission.

0,14

0,16

µµµµavg = 0.14; st. dev. 0.01

Dry

fri

ction

co

eff

icie

nt


0 500 10000,12

Friction path [m]

Dry friction coefficient of a magnetron sputtered 2.5 µm thick Ag2MoO4 coating (after 3h

preliminary annealing at 450 0C) against a 5 mm diam. alumina ball under a load of 10 N

as a function of the friction path. Substrate from Vanadis HS steel after quenching and

tempering to 64 HRC, linear velocity 0.1 m⋅s-1, substrate temperature 450 0C. Own

research together with W. Pawlak, Ph.D., Eng., and M. Makowka, M.Sc., Eng., in the

frame of the POIG project KomCerMet co-funded by DG of the European Commission.

500

1000

Ag2MoO

4 silver molybdate

Ag10.8Mo

22.7O

64.4 as deposited

+ postannealing for 3h in air at 550 0C

Inte

nsity [a

rb. u

nits]


500 1000

0

Inte

nsity [a

rb. u

nits]

Raman shift ∆ω [cm-1]

Spectrum of the intensity of a scattered laser light (λ=514.5 nm) as a function of

the Raman shift ∆ω for the magnetron sputtered nanocomposite Ag2MoO4

coating after a postannealing for 3h at 550 0C deposited. Well developed

Ag2MoO4 silver molybdate polytype of very low FWHM of the Raman peaks.

ADVISABLE DEPOSITION OF FRICTION-REDUCING COATINGS ONTO:- any split bearing bushes, bearing pillows or bearing sleeves

- shaft necks of crankshafts or camshafts

- sliding surfaces of timing gears (chain type or toothed or cogged ones)

- dismountable bearing roller races or roller paths

- friction couples of fuel injectors

- racing surfaces of turbochargers’ airfoil bearings

- friction couples of air and refrigerant compressors

- duplex treatment of piston pins’ racing surface (NITROVAC®+nc-WC/a-C:H)

- piston skirts

- gudgeon pins

OTHER EXAMPLES:

air and refrigerant

compressors

hydraulic and

pneumatic valves

and fittings

sliding bearings synchronizersball pins

&

valve spindles

parts of waterpumps


Technical University of Lodz

Institute of Materials Science

& Engineering, Lodz, Poland

THANK YOU VERY MUCH

FOR YOUR ATTENTION


FOR YOUR ATTENTION

LOW FRICTION SELFLUBRICATING COATINGS FOR …

Documents

Transcript of LOW FRICTION SELFLUBRICATING COATINGS FOR …