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