Presentation on

Powder Methods

VIJAY2008AMD2925

Introduction Manufacturing process in which fine powder of

materials are-Blended or mixed,Compacted (pressed) in to required shape, size and surface

finish Sintered (heated) Controlled atmosphere to bond the contacting surfaces of

particles and to achieve required properties like strength, density etc.

High quality, complex parts to close tolerances in an economical manner (eliminating additional machining or finishing operations ).

Controlled degree of density, porosity, strength and other properties of material, with minimum waste

ApplicationsApplication Metals Uses

Abrasive Fe, Sn, Zn Cleaning, abrasive wheelsAerospace Al, Be, Nb Jet engine, heat shield

Automotive Cu, Fe, W Valve insert, bushing, gearsElectronic Ag, Au, Mo Diode heat sink

Joining Cu, Fe, Sn Solder, electrodeMagnetic Co, Fe, Zn Relay, magnets

Manufacturing Cu, Mn, W Dies, tools, bearingsNuclear Be, Ni, W Shielding, filters, reflector

Tungsten lamp filaments, oil-less bearings, automotive transmission

gears, electrical contacts, nuclear power fuel elements, aircraft brake

pads, jet engine components, printed circuit boards, explosives, welding electrodes, rocket fuels, etc [2]

Table1:- Application of powder methods [1]

Production of a component

1. Production of powder

2. Preparation of powder including blending and mixing

3. Compacting

4. Sintering 5. Post sintering treatment [3]

Production of Powder

1. Mechanical method (milling) Ball mills and roller mills Ferrous and non ferrous materials Brittle

Fig 1:- Ball mill

Image courtesy: - Ref. [4]

Production of Powder2. Electrolytic Deposition

Spongy or powdery state of metalSuitable conditions; composition and strength of the

electrolyte, temperature, current density, etcCopper, chromium and manganese powders Pure powder

Fig 2:- Electrolytic deposition Image courtesy: - Ref. [2]

Production of Powder3. Reduction of ores Iron powder

4. Atomisation Liquid metals – Orifice- Jet stream of gas, water, or

steam –Broken into fine particles To control particle size distribution-

Parameters; design and configurations of the jets, pressure and volume of the atomising fluid, thickness of the stream of metal, etc

Production of iron, tool steels, alloy steels, copper, brass, bronze and the low-melting-point metals, such as aluminium, tin, lead, zinc, cadmium powders. [2]

Fig 3:- Vertical gas atomization unit Image courtesy: - Ref. [5]

Preparation of powder Blending and MixingTo obtain desired properties and characteristics we

have to mix Powder of different materials -different grades and

sizes- different compositionLubricants and binders. Alloying elements

Fig 4:- Powder contents Image Courtesy: - Ref. [2]

Compacting Loose powder of material is compressed and densified –Green

compact- At room temp.

Mechanical, hydraulic and pneumatic presses.

Fig 5:- Compaction sequence

(1)Cycle start (2)Charge die with powder(3)Compaction begin(4) Compaction completed(5) Ejection of part(6) Recharging die

Image Courtesy: - Ref.[2]

Sintering Green compact is heated in a controlled atmosphere Below the melting point but high enough to permit solid

state diffusionHeld for sufficient time to permit bonding of the particlesSintering temperature range for iron-based alloys is

1100-1150°C and the time varies between 10 and 60 minutes, depending on the application [6]

Fig 6:- Sintering process Image Courtesy: - Ref. [7]

Post sintering treatments

Machining De-burring Joining Heat treatment Double Pressing Oil Impregnation

Advantages of the powder methods Complex shapes can be produced. Close dimensional accuracy with elimination

or reduction in machining. High production rate due to automation. Wide range of properties like density, porosity

and particle size can be obtained. No waste during fabrication. Highly skilled labour is not required. [8]

Disadvantages and limitations Pure metal powders are very expensive. Size of part produced is limited. Alloy powders are not easily obtained. Strength properties are lower than product

manufactured by convention way. Increased tendency to oxidation due t pores. Poor plastic properties like impact strength,

elongation etc. High pressure and severe abrasion involved in

process increase the die cost. [8]

References:-1. Manufacturing Engineering and Technology by Seropr

Kalpakjian and Steven R. Schmid , Chapter 17, Table 17.1 Page 461

2. http://www.turktoz.gazi.edu.tr3. Manufacturing Engineering Processes by Leo Alting, Chapter

9, Page 281-2994. http://www.ktf-split.hr/glossary/image/ball_mill.gif5. http://www.xstreamscience.org/H_Glaze/assets/Powder

%20Atomizer.gif6. http://www.substech.com7. http://www.azom.com/details.asp?ArticleID=1328. Elements of Workshop Technology by S.K. and A.K. Hajra

Choudhury, Chapter 12, Page 431-440.

Thank You…….