FGM & PM in brief

1. By
Mr. Gajare S.M.
Under the Guidance of
Dr. S.G.Kulkarni.
DEPARTMENT OF MECHANICAL ENGINEERING,
SKN SINHGAD COLLEGE OF ENGINEERING, KORTI, PANDHARPUR
ACADEMIC YEAR 2019-20
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2. INTRODUCTION
In materials science, Functionally Graded Material (FGM)
may be characterized by the variation in composition and
structure gradually over volume, resulting in corresponding
changes in the properties of the material. The materials can be
designed for specific function and applications.
Due to the unique graded materials properties, FGMs have
attracted a great amount of attention from researchers in many
fields, including aerospace, biomaterials and engineering among
others in the past decades.
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3. TYPES OF FGM
FGM are classified according to different criteria:
I. Chemical Composition Gradient Functionally Gradient
Materials
II. Porosity Gradient Functionally Gradient Materials
III.Microstructure Gradient Functionally Gradient Materials
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4. TYPES OF FGM
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5. The functionally graded materials are usually in the form of surface
coatings, there are a wide range of surface deposition processes to
choose from depending on the service requirement from the process.
A. Vapour Deposition Technique
B. Centrifugal method
C. Gel casting
D. Solid Free Form (SFF) Fabrication Method
E. Powder Metallurgy(PM)
Manufacturing process
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6. Vapour Deposition Technique
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7. Centrifugal Casting
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8. Gel Casting
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9. Self Propagataing High Temp.Synthesis(Sfs)
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10.  Powder Metallurgy (PM) is an art & science of producing metal
or metallic powders, and using them to make finished or semi-
finished products.
 Particulate technology is probably the oldest forming technique
known to man.
 There are archeological evidences to prove that the ancientman
knew something about it.
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11.  Powder production
 Blending or mixing
 Powder compaction
 Sintering
 Finishing Operations
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12. POWDER
PROCESSING
PROPERTIES
Powder fabrication
Size and shape characterization
Microstructure (e.g.. dendrite size)
Chemical homogeneity, and ppt. size
Compaction
Sintering
Forging/Hot pressing
Density, Porosity
Ductility, Strength
Conductivity
Other functional properties
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13. Blending and mixing (Rotating drums, blade and
screw mixers)
Pressing - powders are compressed into desired
shape to produce green compact
Accomplished in press using punch-and-die
tooling designed for the part
Sintering – green compacts are heated to bond the
particles into a hard, rigid mass.
Performed at temperatures below the melting point
of themetal
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14.  In general, producers of metallic powders are not the same
companies as those that make PM parts
 Any metal can be made into powder form
 Three principal methods by which metallic powders are
commercially produced
 Atomization (by gas, water, also centrifugal one)
 Chemical
 Electrolytic
 In addition, mechanical methods are occasionally used to reduce
powder sizes
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15. Conventional powder
metallurgy production
sequence:
 blending
 compacting
 Sintering
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16. For successful results in compaction and sintering,
the starting powders must be homogenized
(powders should be blended and mixed).
 Blending - powders of same chemistry but possibly different
particle sizes are intermingled
 Different particle sizes are often blended to reduce porosity
 Mixing- powders of different chemistries are combined .
PM technology allows mixing various metals into alloys that would
be difficult or impossible to produce by other means.
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17.  Blending a coarser fraction with a finer fraction ensures that the
interstices between large particles willbe filled out.
 Powders of different metals and other materials may be mixed in
order to impart special physical and mechanical properties
through metallic alloying.
 Lubricants may be mixed to improve the powder’s flow
characteristics.
 Binders such as wax or thermoplastic polymers are added to
improve green strength.
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18. To make a homogeneous mass with uniform distribution of
particle size and composition.
 Powders made by different processes have different sizes and
shapes
 Mixing powders of different metals/materials
Combining is generally carried out in
 Air or inert gases to avoid oxidation
 Liquids for better mixing, elimination of dusts and reduced
explosion hazards
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19. Amixer suitable forblending metal
powders.
Some common equipment geometries used for
blending powders
(a) Cylindrical, (b) rotating cube, (c) double
cone, (d) twin shell
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20. Application of high pressure to the powders to form
them into the required shape.
Conventional compaction method is pressing, in which
opposing punches squeeze the powders contained in a die.
 The work part after pressing is called a green compact,
the word green meaning not yet fully processed.
 The green strength of the part when pressed is adequate
for handling but far less than after sintering.
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21. Press powder into the desired shape and size in dies using a
hydraulic or mechanical press
Pressed powder is known as “green compact”
Stages of metal powder compaction:
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22.  Powders do not flow likeliquid, they simply compress until an
equal and opposing force is created.
 – This opposing force is created from a combination of
I. resistance by the bottom punch and
II. friction between the particles and die surface
 Compacting consolidates and dandifies the component for
transportation to the sintering furnace.
 Compacting consists of automatically feeding a controlled amount
of mixed powder into a precision die, after which it is compacted.
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24. Figure: Typical compaction sequence for a single-level part, showing the
functions of the feed shoe, die core rod, and upper and lower punches. Loose
powder is shaded; compacted powder is solid black.
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25.  Heat treatment to bond the metallic particles, there by increasing
strength and hardness.
 Usually carried out at between 70% and 90% of the metal's melting
point (absolute scale)
– Generally agreed among researchers that the primary driving
force for sintering is reduction of surface energy
– Part shrinkage occurs during sintering due to pore size
 reduction
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27.  Near Nett Shape is possible, thereby reducing the post-production
costs, therefore:
Precision parts can be produced
The production can be fully automated, therefore,
Mass production is possible
Production rate ishigh
Over-head costs are low
Break even point is not too large
Material loss is small
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28. Virtually unlimited choice of alloys, composites, and
associated properties
 Refractory materials are popular by this process
Can be very economical at large run sizes (100,000
parts)
Long term reliability through close control of
dimensions and physical properties
Wide latitude of shape and design
Very good material utilization
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29.  High tooling and equipment costs.
 Metallic powders are expensive.
 Problems in storing and handling metal powders.
 Degradation over time, fire hazards with certain metals
 Limitations on part geometry because metal powders do not
readily flow laterally in the die during pressing.
 Variations in density throughout part may be a problem,
especially for complex geometries.
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30.  Porous !! Not always desired.
 Large components cannot be produced on a large scale.
 Some shapes are difficult to be produced by the conventional
p/m route.
Whatever, the merits are so many that P/M, as a
formingtechnique, is gaining popularity
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