November 14, 2013Mechanical Engineering Tribology Laboratory (METL)

Abhishek BaratResearch Assistant

Effect of Polishing and Surface Roughness on the performance of

coatings in Fretting Wear 

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November 14, 2013Mechanical Engineering Tribology Laboratory (METL)

Outline• Motivation and Background• Objective• Fretting Wear Test Rig• Description of experiment• Results• Future work

Personal Background• Joined Mechanical Engineering Tribology Laboratory, (METL) –

August 2013• Worked as Scientist – Gas Turbine Research Establishment, India

(December, 2009 – July, 2013)• B.Tech (Hons) in Mechanical Engineering from National Institute of

Technology, Bhopal

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November 14, 2013Mechanical Engineering Tribology Laboratory (METL)

• Fretting is the oscillatory tangential relative movement between two contacting surfaces due to small amplitude vibration. (Waterhouse R. B)

• Initial surface roughness has a significant effect on friction and wear rate• High surface roughness leads to low friction coefficient and a higher wear rate (Kubiak et.al)

• Thermal sprayed coatings - improve wear resistance and decrease friction coefficient under sliding conditions. (Picas A. J)

• CrC-NiCr coatings used to counter wear at high temperatures

I. Surface morphology in engineering applications: Influence of roughness on sliding and wearing dry fretting; K.J. Kubiak, T.W.Liskiewicz , T.G.Mathia

II. Interface roughness effect on friction map under fretting contact conditions; K.J. Kubiak, T.G. Mathia, S. Fouvry

III. The influence of heat treatment on tribological and mechanical properties of HVOF sprayed CrC–NiCr coatings; Josep A. Picas, Miquel Punset, Sergi Menargues, Manel Campillo, M. Teresa Baile, Antonio Forn

Background and Motivation

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November 14, 2013Mechanical Engineering Tribology Laboratory (METL)

• Experimentally investigate effect of polishing on fretting wear resistance of surface coatings– Study the fretting wear behavior of polished and unpolished

surface coated samples, at different load conditions– Compute wear volumes and compare the wear coefficients– Develop a numerical model and validate with experimental

results

Objective

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November 14, 2013Mechanical Engineering Tribology Laboratory (METL)

Fretting Wear Test Rig

• Contact configurations– Flat-on-Flat– Ball-on-Flat– Crossed Cylinder

• Testing capabilities– In situ contact point

observation– Friction and fretting wear

measurement– Lubricated and un-

lubricated environments– Elevated temperatures

Stationary Test Specimen

Linear Actuator

Upper Loading Weight

Loading Arm

Counterweight

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November 14, 2013Mechanical Engineering Tribology Laboratory (METL)

Description of Experiment• Experimental setup – Flat on Flat Configuration• Specimens to be tested at 3 different levels of

surface roughness: – Unpolished - Ra = 4.87µm – Polished - Ra = 0.2µm– Finely Polished - Ra = 0.01µm

• Experiment variables– Total time of experiment: 36 hours– Displacement Amplitude: 30 µm– Frequency: 20 Hz– Load/Normal force (kg): 4, 6, 8, 10– Slip regime: Gross Slip

Polished Specimen Unpolished Specimen

Data Acquisition System

-40 -30 -20 -10 0 10 20 30 40-40

-30

-20

-10

0

10

20

30

40

Displacement (m)

Friction F

orc

e (

N)

Partial Slip

Gross Slip

Amplitude

Friction force

Fretting loop

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November 14, 2013Mechanical Engineering Tribology Laboratory (METL)

Results

Wear Scars

Displacement (

Wear ScarsRaw scan of the worn regions, as observed under a microscopeSurface MapsSurface map of the wear scars and surrounding unworn region obtained using a surface profilometer. Used to calculate the worn volumeProfileA cross section of the surface, showing depth of wear scar relative to the unworn surfaceFretting LoopPlot of friction force vs displacement amplitude . Used to calculate the total dissipated energy

Where is the dissipated energy wear coefficient (Fouvry, 1997)

ProfileFretting Loop (Polished)

Surface Maps

Unpolished PolishedWear analysis in fretting of hard coatings through dissipated energy concept; Siegfried Fouvry, Philippe Kapsa, Hassan Zahouani, LEO Vincent

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November 14, 2013Mechanical Engineering Tribology Laboratory (METL)

Future Work• Extend the study to more materials and coatings• Analyze the effect of displacement amplitude and frequency

on the polished and unpolished coating performance• Study wear scars under SEM to evaluate the underlying

wear mechanisms• Study the contact evolution by observing the contact area in

situ • Build a FEA model of fretting wear with surface roughness