Jeevan ppt

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Department of Mechanical Engineering KAKATIYA INSTITUTE OF TECHNOLOGY & SCIENCE ::WARANGAL

–15 ( An Autonomous Institute under Kakatiya University )

DEVELOPMENT OF CEMENTED TUNGSTEN CARBIDE TOOL USING POWDER METALLURGY

Jeevan Pasunuti

( B14ME085 )Under the guidence of Sri P.Prabakara rao

( Assistant Professor.MED )

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Abstract

The technology of pressing metal powders into a specific shape is not new, older civilizations practiced the art in prehistoric times, as bear witness the iron pillar in Delhi. Modern powder metallurgy (P/M) technology commenced in the 1920s with the production of tungsten carbides and the mass production of porous bronze bushes for bearings.

Powder Metallurgy is the process of blending fine powdered materials, pressing them into a desired shape or form (compacting), and then heating the compressed material in a controlled atmosphere to bond the material (sintering and pre-sintering). The final component usually does not require further machining processes. Hard materials used for cutting tools include cemented carbides , Tungsten the main component of cemented carbides.

In this presentation the development of Cemented Carbide Tool Using Powder Metallurgy was presented.

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1) Introduction to powder metallurgy2) Powder manufacturing a) Atomization3) Blending & Mixing4) Compacting5) Sintering 6) Advantages & Disadvantages7) Conclusion.8) References

Contents

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Powder Metallurgy

Powder metallurgy is the process of blending fine powdered materials into a desired shape, and then heating the compressed material in a controlled atmosphere to bond the material. the final component doesn’t require further machining processes.

The technology of pressing metal powders into a specific shape is not new, Older civilisations practiced the art in prehistoric times.

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Metal and Non Metal Can also be CombinedMelting Point of the metal to be used for making a product is too high ( W , Mo).Used for metals that are too Hard to Machine.Some Components can only be manufactured by Powder Metallurgy.

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Powder Metallurgy Process

Powder production Blending or mixing Powder compaction Pre-Sintering Sintering Finishing Operations

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Powder manufacturing Mechanical methods : This process

involves the disintegration of liquid or solid metals inorder to produce metal powders.

Machining Crushing Milling Atomization

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Powder manufacturing

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Physico-chemical process: It involves both Physical and Chemical Process

Condensation Thermal decomposition Reduction Electro deposition

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Atomization

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Particle Shapes in Metal Powders

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Blending (or) Mixing : Blending is an operation of thorough intermingling of different powders of same composition of various grades of the same powders , where as mixing refers to the thorough intermingling of

powders of more than one material . Alloying powders , lubricants and voilating agents are added to the blended powders during mixing to give the desired amount of porosity.

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The main purpose of compaction is to produce metal compacts of desired shape from metal powders. The compacts should have sufficient strength to withstand ejection from the tools and subsequent handling upto the completion of sintering.

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Compacting

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Press powder into the desired shape and size in dies using a hydraulic or mechanical press

Pressed powder is known as “green compact”.

The compacts must be sufficiently strong and withstand ejection from die and subsequent handling before sintering.

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Compacting

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SinteringSintering is a heat treatment applied to a powder compact in order to impart strength and integrity.The thermal treatment of powder at temperature below the melting point of the main constituent for the purpose of increasing its strength by bonding together.

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Figure: Sintering on a microscopic scale: (1) particle bonding is initiated at contact points; (2) contact points grow into

"necks"; (3) the pores between particles are reduced in size; and (4) grain boundaries develop between particles in place of

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Sintering Sequence Parts are heated to 0.3~0.6 Tm. Transforms compacted mechanical bonds to much

stronger metallic bonds.

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Powder Metallurgy Merits

Precision parts can be produced The production can be fully automated,

therefore, Mass production is possible Production rate is high Over-head costs are low Material loss is small

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Disadvantages High tooling and equipment costs. Metallic powders are expensive. Problems in storing and handling metal powders. Degradation over time, fire hazards with certain

metals Limitations on part geometry because metal

powders do not readily flow laterally in the die during pressing.

Variations in density throughout part may be a problem, especially for complex geometries.

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Development of Cemented Tungsten Carbide Tool

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Development of Cemented Tungsten

Carbide Tool Mixing: Tungsten carbide and Other Additives. Compacting: With a pressure of 48 Kg/cm². Pre-sintering: Controlled Hydrogen

atmosphere at a temperature of about 900̊C. Final sintering : At a temperature of 1300̊C

for about 2 hours to develop full hardness. Super finishing: Grounding if necessary.

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References[1] S.R.J.Shantha Kumar ,̎Material and Metallurgical Science̎, Anuradha Agencies.[2] L. Krishna Reddy, ̎Principles of Engineering Metallurgy̋, New Age International Publications.[3] Pay yen and Deborah D.l.chung , “The International journal of powder metallurgy”, volume-31 no-4,1995.[4] G.S.Upadhyaya , “Cambridge international science publishing”, Indian Institute of Technology, Kanpur, India.[5] P.Ramakrishnan,”Indian journal of History of sciences”, 18(1):109-114 (1983 ).[6] Dr.P.Prabakar rao, Assistant Professor, MED ( KITSW ).

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