1. Wear Mechanism
SHIVAJI CHOUDHURY

2. Wear
 Wear is the undesirable removal of
solids from a sliding or rolling
component.

3. Wear analysis
 In analyzing a wear problem in a machine,
it is necessary to determine the kind of
wear that occurred.
 Analysis requires microscopic examination
of the worn area and a close look at the
used lubricant.
 Wear is generally proportional to the
applied load and the amount of sliding.

4. Types of wear :
 1.Adhesive Wear
 2.Abrasive Wear
 3.Erosion Wear
 4.Polishing Wear
 5.Contact fatigue
 6.Corrosive wear
 7.Electro-Corrosive
wear
 8.Fretting wear
 9.Electrical
discharge wear
 10.Cavitation
damage
 11.False brinelling

5. 1.Adhesive Wear
Adhesive Wear — the removal of material due to
adhesion between surfaces.
1. – Mild adhesion — is the removal of surface films,
such as oxides, at a low rate.
2. – Severe adhesion — the removal of metal due to
tearing, breaking, and melting of metallic junctions.
This leads to scuffing or galling of the surfaces and
even seizure.

6. 1.1.Adhesive Wear -Prevention
 MECHANICAL
1. Reduce load, speed
and temperature
2. Improve oil cooling
3. Use compatible
metals
4. Apply surface
coatings such as
phosphating
LUBRICANT
1. Use more viscous
oil to separate
surfaces
2. Use "extreme
pressure" (anti-scuff)
additives
such as a sulfur-phosphorous
or
borate compounds

7. 2.Abrasive Wear
• Abrasive Wear — the cutting of furrows on a
surface by hard particles, (for example,
sand particles between contact surfaces, or
hard asperities on an opposing surface).
 Hard coatings can reduce abrasive wear.

8. 2.1.Abrasive Wear-Prevention
 MECHANICAL
1. Remove abrasive by
improved air and oil
filtering, clean oil
handling practices,
improved seals, flushing
and frequent oil changes
2. Minimize shot peening,
beading, or sand blasting
of surfaces because
abrasives cannot be
completely removed
3. Increase hardness of
metal surfaces
 LUBRICANT
1. Use oil free of
abrasive particles
2. Use more viscous
oil

9. 3.Erosion Wear
 • Erosive Wear — the cutting of
furrows on a surface by hard particles
contained in a fluid traveling at high
velocity.

10. 3.1.Erosion Wear -Prevention
 MECHANICAL
1. Remove abrasive by
improved air and oil
filtering, clean oil
handling practices,
improved seals, flushing
and frequent oil changes
2. Reduce impact angle to
less than 15 degrees
3. Increase hardness of
metal surfaces
 LUBRICANT
1. Use oil free of abrasive
Particles
2. Use more viscous oil

11. 4.Polishing Wear
 • Polishing Wear — the continuous removal
of surface films, laid down via a chemical
reaction from an additive in oil or by very
fine hard particles in the lubricant, and so
on.
 Polishing wear is characterized by very
shiny, very smooth, mirror like metal
surfaces. Fine abrasives wear away the
surface films as they form and reform.

12. 4.1.Polishing Wear -Prevention
 MECHANICAL
1. none
 LUBRICANT
1. Choose less
chemically active
additive
2. Remove corrosive
contaminant
3. Remove abrasive

13. 5.Contact fatigue
 • Contact Fatigue — the cracking,
pitting, and spalling of a surface in
sequence due to cyclic stresses in a
contact.
 Contact fatigue is most common in
rolling element bearings, gear teeth,
and cams.

14. 5.1.Contact fatigue- Prevention
 MECHANICAL
1. Reduce contact
pressures and
frequency of cyclic
stress.
2. Use high quality
vacuum melted
steels.
3. Use less abusive
surface finish
 LUBRICANT
1. Use clean, dry oil.
2. Use more viscous
oil
3. Use oil with
higher-pressure
viscosity coefficient

15. 6.Corrosive wear
 • Corrosive Wear — the removal of
corrosion products from a surface by
motion, such as the rubbing off of
rust.

16. 6.1.Corrosive wear-Prevention
 MECHANICAL
1. Use more corrosion
resistant metal
(not stainless)
2. Reduce operating
temperature
3. Eliminate corrosive
material
 LUBRICANT
1. Remove corrosive
material such as
too chemically
active additive and
contaminates
2. Use improved
corrosion inhibitor
3. Use fresh oil

17. 7.Electro-Corrosive wear
 • Electro-Corrosive Wear — the
removal of metal by dissolution in a
corrosive liquid with the aid of electric
currents.
 One source of currents is streaming
potential from high velocity fluids.
 The oil serves as the electrolyte.

18. 7.1.Electro-Corrosive wear-prevention
 MECHANICAL
1. Decrease liquid
velocity and
velocity gradients
2. Use corrosion-resistant
metals
3. Eliminate stray
currents
 LUBRICANT
1. Decrease or
increase electrical
conductivity of
lubricants or
hydraulic fluids

19. 8.Fretting wear
 • Fretting Wear — localized wear of
lubricated surfaces due to
reciprocating sliding of extremely low
amplitude because of vibration.

20. 8.1.Fretting wear -Prevention
 MECHANICAL
1. Reduce or stop
vibration by tighter
fit or higher load .
2. Improve lubrication
between surfaces by
rougher (then
honed) surface finish
 LUBRICANT
1. Use oil of lower
viscosity
2. Relubricate
frequently
3. Use oxidation
inhibitors in oil

21. 9.Electrical discharge wear
 • Electrical Discharge Wear — the
removal of molten metal from
surfaces due to electrical sparks
between them.
 High static voltages are sometimes
generated by large rotating
machinery and these are relieved by
sparking to regions of lower potential.

22. 9.1.Electrical discharge wear-
Prevention
 MECHANICAL
1. Improve electrical
insulation of bearings
2. Degauss magnetic
rotating parts
3. Install brushes on
shaft
4. Improve machine
grounding
 LUBRICANT
1. Use of oil of higher
electrical conductivity

23. 10.Cavitation damage
 • Cavitation Damage — the removal of
material due to cracking and pitting caused
by high energy implosions of vacuous
cavities in a cavitating liquid.
 Liquids cavitate when suddenly subjected
to low pressures.
 Removal of metal by vapor cavity implosion
in a cavitating liquid.

24. 10.1.Cavitation damage-Prevention
 MECHANICAL
1. Use hard, tough
metals, such as tool
steel
2. Reduce vibration, flow
velocities and
pressures
3. Avoid restriction and
obstructions to liquid
flow
 LUBRICANT
1. Avoid low vapor
pressure, aerated, wet
oils
2. Use noncorrosive oils

25. 11.False Brinelling
 • False Brinelling — localized wear in
lubricated rolling element bearings
due to slight rocking motion of rollers
against raceways.

26. 11.1.False Brinelling- Prevention
 MECHANICAL
1. Reduce or
eliminate impact
2. Rotate bearings
occasionally
 LUBRICANT
1. Change viscosity

27. Microscopic Observation
(Wear debris analysis)
 (a) Rubbing wear,
 (b) cutting wear,
 (c) fatigue wear,
 (d) scuffing wear,
 (e) corrosive
wear,
 (f) abrasive wear.

28. Bearing damage classifications:
ISO 15243

29. Thanking you