Transcript Effect of Polishing and Surface Roughness on the performance of coatings in Fretting Wear Abhishek Barat Research Assistant Mechanical Engineering Tribology Laboratory (METL) November 14, 2013

Effect of Polishing and Surface
Roughness on the performance of
coatings in Fretting Wear
Abhishek Barat
Research Assistant
Mechanical Engineering Tribology Laboratory (METL)
November 14, 2013
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Outline
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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
Mechanical Engineering Tribology Laboratory (METL)
November 14, 2013
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Background and Motivation
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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
Surface morphology in engineering applications: Influence of roughness on sliding and wearing dry fretting; K.J. Kubiak, T.W.Liskiewicz , T.G.Mathia
Interface roughness effect on friction map under fretting contact conditions; K.J. Kubiak, T.G. Mathia, S. Fouvry
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
Mechanical Engineering Tribology Laboratory (METL)
November 14, 2013
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Objective
• 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
Mechanical Engineering Tribology Laboratory (METL)
November 14, 2013
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Fretting Wear Test Rig
Counterweight
• Contact configurations
Loading Arm
– Flat-on-Flat
– Ball-on-Flat
– Crossed Cylinder
• Testing capabilities
– In situ contact point
Upper Loading Weight
observation
– Friction and fretting wear
measurement
– Lubricated and unlubricated environments
– Elevated temperatures
Stationary Test Specimen
Linear Actuator
Mechanical Engineering Tribology Laboratory (METL)
November 14, 2013
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Description of Experiment
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Experimental setup – Flat on Flat Configuration
Specimens to be tested at 3 different levels of
surface roughness:
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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
Amplitude
Partial Slip
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30
Friction force
20
Friction Force (N)
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Unpolished - Ra = 4.87µm
Polished - Ra = 0.2µm
Finely Polished - Ra = 0.01µm
10
0
-10
Fretting loop
-20
-30
-40
-40
-30
-20
-10
0
10
Displacement (m)
20
30
40
Gross Slip
Data Acquisition System
Mechanical Engineering Tribology Laboratory (METL)
November 14, 2013
Results
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Wear Scars
Raw scan of the worn regions, as observed
under a microscope
Surface Maps
Surface map of the wear scars and surrounding
unworn region obtained using a surface
profilometer. Used to calculate the worn
volume
Profile
A cross section of the surface, showing depth of
wear scar relative to the unworn surface
Wear Scars
Fretting Loop
Plot of friction force vs displacement amplitude
. Used to calculate the total dissipated energy
𝑽𝒘 = 𝜶𝑬𝑫
Where 𝛼 is the dissipated energy wear
coefficient (Fouvry, 1997)
Surface Maps
Displacement (𝜇𝑚)
Fretting Loop (Polished)
Profile
Unpolished
Polished
Wear analysis in fretting of hard coatings through dissipated energy concept; Siegfried Fouvry, Philippe Kapsa, Hassan Zahouani, LEO Vincent
Mechanical Engineering Tribology Laboratory (METL)
November 14, 2013
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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
Mechanical Engineering Tribology Laboratory (METL)
November 14, 2013