Download - Powder Metallurgy Process (E-2 Batch)
POWDER METALLURGY
PROCESSGROUP MEMBERS:NAMIT SINGH (111650)NIKHIL KATIYAR (111651)NITIN GOYAL (111652)NITIN VIJ (111653)
OVERVIEWHISTORYINTRODUCTIONBLENDING &MIXINGCOMPACTIONSINTERINGFINISHINGADVANTAGES & DISADVANTAGESAPPLICATIONS
HistoryThe history of powder metallurgy (P/M) and the art of
metals and ceramics sintering are intimately related to each other.
Sintering involves the production of a hard solid metal or ceramic piece from a starting powder.
While a crude form of iron powder metallurgy existed in Egypt as early as 3000 B.C.
The smiths of India, produced the famous "Delhi Iron Pillar" weighs about 6.5 tons and other objects even larger as early as 300 A.D.
Mass manufacturing of P/M products did not begin until the mid-or late- 19th century. In these early manufacturing operations, iron was extracted by hand from metal sponge following reduction and was then reintroduced as a powder for final melting or sintering.
Introduction After the metallic powders have
been produced and classified, the conventional P/M process sequence consists of three major steps:
Blending and mixing of powders CompactionSintering and a number of
optional and finishing secondary operations.
Simplified flowchart illustrating the sequence of operations in powder metallurgy process
The condition of powders during the three primary P/M operations is shown in the figure:
The conventional P/M process sequence: (1) blending, (2) compacting, and (3) sintering; (a) shows the condition of powders, and (b) shows the schematics
of operation
(a)
(b)
(1) (2) (3)
Blending and MixingBlending : mixing powder of the same
chemical composition but different sizesMixing : combining powders of different
chemistriesBlending and mixing are accomplished by
mechanical means:
Several blending and mixing devices: (a) rotating drum, (b) rotating double cone,(c) screw mixer, (d) blade mixer
CompactionBlended powers are pressed in dies under
high pressure to form them into the required shape. The work part after compaction is called a green compact or simply a green, the word green meaning not yet fully processed.
SinteringCompressed metal powder is heated in a
controlled-atmosphere furnace to a temperature below its melting point, but high enough to allow bounding of the particles:
(a) Typical heat treatment cycle in sintering ; (b) schematic cross-section of a continuous sintering furnace
Finishing Operation A number of secondary and finishing
operations can be applied after sintering, some of them are:
Sizing : cold pressing to improve dimensional accuracy
Coining : cold pressing to press details into surface
Impregnation : oil fills the pores of the partInfiltration : pores are filled with a molten
metalHeat treating, plating, painting
Advantages / Disadvantages Virtually unlimited choice of alloys, composites,
and associated properties. Controlled porosity for self lubrication or
filtration uses. Can be very economical at large run sizes
(100,000 parts). Long term reliability through close control of
dimensions and physical properties. Very good material utilization. Limited part size and complexity High cost of powder material. High cost of tooling. Less strong parts than wrought ones. Less well known process.
Applications of powder metallurgy
► Electrical Contact materials► Heavy-duty Friction materials► Self-Lubricating Porous bearings► P/M filters► Carbide, Alumina, Diamond cutting
tools ► Structural parts► P/M magnets► Cermets and more, such as high tech
applications