Post on 02-Jan-2016
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