Porous Bearings- Application of
Powder Metallurgy
Presented by:
Surya Singh -BT15MME073
Teer Meena -BT15MME074
Sakshi Turkar-BT15MME075
LEARNINGS
➢ What are Porous Bearings and
their need?
➢ Manufacturing
➢ Working of Porous Bearings
➢ Advantages and Drawbacks of
Porous Bearings.
➢ Properties of Porous Bearing
materials and materials used
➢ Applications of Porous Bearings
What are Porous Bearings?
▪ metallic component
▪ high percentage of porosity (20-25% volume)
Need for Porous Bearings
▪ Overcome the heat conductivity limitations of oil
soaked wooden bearings which eventually turned dry
after some time.
▪ Hence need for self-lubricating bearings.
Manufacturing of Porous Bearings
Production of Cu, Sn, graphite powder
Mixing of Elemental Powders
Compaction
Sintering
Sizing
Impregnation
Bearing
Metallic Powder Production Methods
Water Atomization
Metallic Powder Production Methods
Electrolytic Deposition
Compaction of Powders
• Densification of Powdered particles.
• Interlocking of surface irregularities
• No heating
• Pressure commonly used: 150-700 MPa
• Use of Automated Compaction Presses
• The compact obtained has good green strength
Stages in Compaction
Sintering
• Consolidating the green compact under controlled
temperature (below M.P.) and time.
• Sintering Furnace used: Continuous Mesh Belt Furnace
• Atmosphere: Hydrogen Gas Atmosphere (reducing)
• Type of Sintering: Liquid Phase Sintering
• Stages:
-Burn off zone or Preheat zone (400-450 °C)
-Sintering Zone (800-850 °C)
-Cooling Zone
Sintering Furnace
Sizing
- To control the dimensions of bearings with tolerance.
- Gives information about the load bearing capacity of the bearing.
- Also tells about the measure of heat generated in the bearing.
Impregnation
- Refers to Filling of pores in part with oil
- Technique used is combination of vacuum and pressure. It
involves:
• Sintered part placed in basket and subjected to vacuuum.
• Oil is introduced and external pressure of 4-5 atm is applied.
• Pressure is brought to 1atm and excess oil is drained.
- Oils used are synthetic hydrocarbons and silicone oil.
Working of Porous Bearings
Stationary Position:
• Oil retained in the pores
• Direct metallic contact
Rotating Shaft:
• Rubbing leads to overcome of high friction coefficient
• Temperature raised rapidly
After Operation:
• Reabsorption of oil in pores
Advantages of Porous Bearings
• Provides a constant lubrication to the system and hence
results in very low friction coefficient.
• Reliable as it works for long time without wear.
• Maintenance free and no need for lubricants
• Performs well upto loads of 10MPa.
• Dimensional precision is very high.
• Produces extremely low noise.
Drawbacks of Porous Bearings
• The have limited
circumferential speeds of
supported shafts owing to
thin thickness of oil film.
• Due to high proportion of
pores, they have low
strength and they are
sensitive to impacts and
bruising by edges in
comparision with a
compact material.
Properties of Porous Bearing Materials
• Good Lubrication characteristics (with minimum
maintenance and long service life)
• Adequate mechanical strength (including fatigue strength
over a range of temperatures)
• Good wear characteristics.
• Good heat dissipation capacity
• Must not weld/seize with mating parts (shafts during
service)
Materials
• Bronze: Can produce a wide range of porosities. These
bearings have excellent wear resistance, ductility and
corrosion resistance.
• Leaded Bronze: Has low coefficient of friction, higher
conformability and good resistance to galling.
• Iron: Used for low-cost bearings.
• Leaded Iron: Improved speed capability, and reduced cost.
• Aluminium: provides cooler operating conditions, greater
tolerance for misalignment and longer oil life
Applications of Porous Bearings
1.Automotive
• Starters
• Active driving elements: Brakes, steering, transmission etc.
• Cooling
2.Electric motors and Gear boxes
3.Household Appliances: Washing Machines, fans, shaving
machines
4.Home Appliances: Locks, garage doors, roller shutters,
sliding windows
5.Industrial
THANK YOU
