raghvendra ppt

8/3/2019 Raghvendra Ppt

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Metal powder may be defined as as aggregate ofparticles of metal characterized by small size.

Usually within the range 1- 1000 micron metals inpowder form are used for large no of metallurgicalapplication.

Metal powders are very important for themanufacturing.


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Physico chemical: Conensation.

Thermal deposition.

Reduction.

Precipitation from aqueous &

fused salts.

Hydrometallurgy.

Inter granular Corrosion.

Oxidation & Decarburization.

Electro deposition.

Mechanical : Machining. Crushing. Milling. Shotting. Grinding. Atomization.


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This method is reversed that the electroplating.

There are three methods for powder productionthey are:

Deposition of a hard, brittle mass, which is subsequentlyground to powder.

Deposition as a soft, spongy substance; only loosely adherentwith fluffy texture & easily pulverized by light rubbing.

Direct deposition as powder from the eloctrolyte which dropsto the bottom of the cell.


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The principles, operation & equipment used in theelectro-deposition of metal powders are similar toconventional electroplating & electrowinningmethods, with the basic difference that operating

conditions are so adjusted that. The metal deposits on the cathode as a powdery

or even a spongy material which will give a powdereither directly or after light grinding.


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Initial low concentration of the metal. Low temperature.

High current density.

Stationary electrolyte.

Presence of neutral of neutral salts in high concentration.

Formation of basic compound in the cathode generally occurs onlyin electrolysis with neutral or slightly acid electrolyte. Theprecipitated flows of hydroxide present in cathode . film may besettled down on the cathode surface. Insulate the metal beneath &prevent it from growing, where as free parts of cathode continue togrow. In this way either or non-adherent deposit can be obtained.


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Increase the metal ion concentration. Increase the acid ion concentration.

Increase the temperature electrolyte.

Increase in interval at which at which deposits is being removedfrom the cathode.

Decreasing in current in current density. Decreasing in circulation rate of electrolyte.

Nature of powder:Usually grade or fine. It is within the range of 1

to 30 micron. Dendritic particles are obtained. Their maincharacteristic is their purity.


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The method is used for the powder production of

copper & iron.

Higher current densities than in electroplating are

used. Higher acidity a low metal ion concentration is kept

to make the deposition spongy due to H2evolution.

In order to maintain close tolerance of particle sizeto get uniform grade the equate removal of thepowder either continuously or at frequent interval.


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Melting point of Cu is 10830 C & density is 8.94 gm/cm3.

Copper is different from most other metals in that it combinescorrosion resistance with high electrical & heat conductivity,Formability, macheanability & strength when alloy , Except for high

temperature. The dried powder is proceed through classifier a blending system.

The Cu concentration has been considerably effect on currentdensity, apparent density & particle size of the powder.


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Electro plating

High voltage , low current.

Low current density.

Less H2 evolution.

Adherent film deposition.

High metal ion concentration.

Low acidity.

High temperature.

Electrolytic powderproduction:

Low voltage, high current.

High current density.

More H2 evolution.

Non Adherent deposition.

Low metal ion concentration.

High acidity.

Low temperature.


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lectrolyte: CuSO4+H2SO45-8 g/liter130-150g/liter

Temperature 40-500CCirculation rate 5-6gal/minElectrical condition tank voltage 1 volt

Anode current density 538-645 amp/ m2


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Glues has been used by drawly this resulted in production ofa non adherent fine powder as well as in increase in currentefficiency.

To enhance the separation of powder from the cathode,surface active agent like soap nut solution is added to the

electrolyte. This results in automotive falling of depositedcopper powder.

Main use of electrolytic copper powder of parts by powdermetallurgical free.


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Advantages: Comparatively economical method.

It is possible to produce the highdegree of purity.

It has excellent compatibility &sinterability when we talking aboutpowder metallurgy.

It is possible to obtain wide rangeof powder quality by alternatingthe bath composition.

We get high purity powder by thismethod.

Disadvantages: Time consuming process. High cost of powder due to low

production rate.

Not suitable for the alloypowder production.


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Corrosion engineering

Mars G. Fontana Introduction to electrometallurgy- Saran &

Narain.

Powder metallurgy A K Sinha.


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