Powder Metallurgy

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POWDER METALLURGY

Metal processing technology in which parts are produced from metallic powders powders. .

ADVANTAGES of POWDER METALLURGY PROCESS. 1)A combination of metals and non metals powdered parts can be manufactured. 2)High Dimensional accuracy is achieved. 3)Fine Surface finish is achieved. 4)No material is wasted as scrap. This process makes use of 100% raw material unlike casting, press forming etc. 5)Porous parts can be produced which is not possible by any other method. 6)Highly qualified or skilled person is not required for handling powder metallurgy method. 7)Large scale production of small parts with this process gives efficient results. 8)Production of cemented carbide tools is possible only by this process. 9)It eliminates numerous machining operations. 10)Powder metallurgy parts can be easily brazed, welded, soldered. 11)Process is economical as mass production process.

LIMITATIONS of POWDER METALLURGY PROCESS.

(1)High tooling costs. (2)Expensive raw materials (powders). (3)Relatively long parts are difficult to manufacture. (4)Difficult storing and handling of powders (degradation with time and fire hazard with particular metallic powders). (5)Powder metallurgy is not economical for small scale production. (6)Articles produced by powder metallurgy process possess poor ductility. (7)Difficult to produce high purity powder.

POWDER METALLURGY PROCESS

A. Producing metal powders B. Mixing C. Pressing D. Sintering E. Finishing and sizing the final product.

FLOW CHART FOR PM

A. PRODUCING METAL POWDERS
Various methods for manufacturing powders are-

1.Atomization 2.Reduction 3.Crushing 4.Milling 5.Shotting 6.Electrolysis.

B. MIXING / BLENDING OF METAL POWDERS
•Blending: mixing powder of the same chemical composition but different sizes •Mixing: combining powders of different chemistries. Wet or dry mixing is generally employed
BLENDING AND MIXING IS NECESSARY FOR :• Addition of lubricants coats the powders and reduces die wear and lowers pressure required for pressing of powders. • Mixing powders of different materials • Obtaining uniform distribution of particle sizes

C. PRESSING OF METAL POWDERS
1) DIE PRESSING. • It consists of upper punch and lower punch as shown in figure. • Powder is filled on the space above lower punch. • Upper punch applies high pressure to the powder. • Finally the green compact powder is received as shown in figure. 2. ROLL PRESSING. • Two rolls of appropriate sizes are used. Stream of powder is guided, so that the • rolls are able to apply the necessary compacting pressure in a continuous sequence. 3. EXTRUSION METHOD. • Ram is used for applying force. • Two dies are used for achieving proper thickness. • As seen in the figure the green compact is received which is further send for sintering process.

D. SINTERING
1. Sintering is the Heat treatment process, to bond the metallic particles, thereby increasing strength and hardness 2. Sintering consists of heating pressed metal compacts in batch or contin uous furnaces to a temperature below the melting point of material. 3. Most metals are sintered at 70% to 80% of melting temperature.

E. SECONDARY /FINISHING OPERATIONS
A number of secondary and finishing operations can be applied after sintering, some of them are: • Sizing: cold pressing the sintered part to improve dimensional accuracy. • Coining: cold pressing to press details into its surface. • Impregnation: oil fills the pores of the part • Infiltration: pores are filled with a molten metal • Heat-treating: annealing can be done for stress relief in powder metallurgy part. • Machining- creates geometric features that cannot be achieved by pressing, such as threads, side holes, and other details

SOME APPLICATIONs

Cermets cutting inserts for lathe

Powder Metallurgy:

Cermet cutting tools (Ceramic-Metal composite)

www.kyocera-yashica.com.br

Microstructure: ceramic particles in metal matrix

Cermet-tipped saw blade for long life

www.moldmakingtechnology.com www.toolbarn.com

Metal filters
Powder Metallurgy: Porous Metals

Oil-impregnated Porous Bronze Bearings
nic.sav.sk

www.ondrives.com

www.hd-bearing.com

Powder Metallurgy: Connecting Rods

www.dps-performance.com

Forged on left; P/M on right

Powdered Metal Transmission Gear

www.chipm.com

• Warm compaction method with 1650-ton press • Teeth are molded net shape: No machining • UTS = 155,000 psi • 30% cost savings over the original forged part

Powdered Metal Turbine blade-disk (“blisk”): 1 piece!

www.ml.afrl.af.mil

Conventional Forging vs. Forging of Powdered Metal blank (2nd op)

DeGarmo

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