Presentation On

“Applications Of Powder Metallurgy In Reference with

Cutting tools”

BYDUSHYANT KALCHURI

Introduction: Powder metallurgy is used for manufacturing

products or articles from powdered metals by placing these powders in molds and are compacting the same using heavy compressive force. Typical examples of such article or products are grinding wheels, filament wire, magnets, welding rods, tungsten carbide cutting tools, self-lubricating bearings electrical contacts and turbines blades having high temperature strength. The manufacture of parts by powder metallurgy process involves the manufacture of powders, blending, compacting, profiteering, sintering and a number of secondary operations such as sizing, coining, machining, impregnation, infiltration, plating, and heat treatment.

• In powder metallurgy basically their are many Product prepared with help of Powdered metal in Reference to Cutting Tools.

• Here we will discuss about Two Mostly utilized cutting tool manufactured by Powder metallurgy i.e. :-

1. CEMENTED CARBIDES

2. DIAMOND TOOLS

Manufacture of Cemented Carbides

• Products of powder metallurgy process• Tantalum, titanium, niobium

• Operations• Blending• Compaction• Presintering• Sintering

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Cemented Carbides

Blending

• Five types of powders• Tungsten carbide, titanium carbide, cobalt,

tantalum carbide, niobium carbide• One or combination blended in different

proportions depending on grade desired• Powder mixed in alcohol (24 to 190 h)• Alcohol drained off• Paraffin added to simplify pressing operation

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Compaction

• Must be molded to shape and size• Five different methods to

compact powder• Extrusion process• Hot press• Isostatic press• Ingot press• Pill press

• Green (pressed) compacts soft, must be presintered to dissolve paraffin 6

Presintering

• Green compacts heated to about 1500º F in furnace under protective atmosphere of hydrogen• Carbide blanks have consistency of chalk• May be machined to required shape• 40% oversize to allow for shrinkage that

occurs during final sintering

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Sintering

• Last step in process• Converts presintered machine blanks into

cemented carbide• Carried out in either hydrogen atmosphere or

vacuum• Temperatures between 2550º and 2730º F

• Binder (cobalt) unites and cements carbide powders into dense structure of extremely hard carbide crystals

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Carbides: Inserts• Available in a variety of shapes: square, triangle,

diamond and round• The smaller the included angle, the lower the

strength of the edge

Fig : edge preparation of inserts to improve edge strength.

Cemented-Carbide Applications

• Used extensively in manufacture of metal-cutting tools• Extreme hardness and good wear-resistance

• First used in machining operations as lathe cutting tools• Majority are single-point cutting tools used on

lathes and milling machines

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Diamond :

• Hardest known substance • Low friction, high wear resistance• Ability to maintain sharp cutting edge• Single crystal diamond of various carats used for

special applications• Diamond is brittle , tool shape & sharpened is

important• Low rake angle used for string cutting edge

Polycrystalline Diamond Tools

• Polycrystalline diamond (PCD) layer fused to cemented-carbide substrate• .020 in. thick

• Highly efficient cutting tool• Increased production when machining abrasive

nonmetallic, nonferrous materials

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High PressureHigh Temp

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Types and Sizes of PCD Tool Blank Insert Shapes Available

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Types and Sizes of PCD Tools

• Catalyst-bonded PCD available in three microstructure series• Coarse PCD blanks• Medium-fine PCD blanks• Fine PCD blanks

• Basic difference between types is size of diamond particle used to manufacture blank

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Properties of PCD Tools

• Composite materials found in base provide mechanical properties• High thermal conductivity and low coefficient

of thermal expansion• Diamond layer• Hardness, abrasion resistance, compressive

strength, and thermal conductivity• Compressive strength highest of any tool• Thermal conductivity highest of any tool

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Advantages of PCD Tools

Offset their higher initial cost

1. Long tool life

2. Cuts tough, abrasive material

3. High quality parts

4. Fine surface finishes

5. Reduced machine downtime

6. Increased productivity

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Types of Material Cut

1. Nonferrous metals• Typically soft but have hard particles

dispersed• Silicon-aluminum alloys• Copper alloys

2. Tungsten carbide3. Advanced composites4. Ceramics5. Wood composites

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Disadvantages of PCD Tools

1. Carbon Solubility Potential

2. Their higher initial cost

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Electro-Plated Diamond Tools

• Process• Polycrystalline Diamond coated with copper or

nickel metal• Copper or nickel mixture electroplated to a

metallic form• Electroplated form then dressed to remove a

small amount of metal to expose PCD within• Form tools can be de-plated and re-plated

multiple times20

Diamond-Coated Tools

• Early 1980s brought new process of chemical vapor deposition (CVD)• Produce diamond coating few microns thick

• Process• Elemental hydrogen dissolved in hydrocarbon

gas around 1330º• Mixture contacts cooler metal, carbon

precipitates in pure crystalline form and coats metal with diamond film (slow 1-5 microns/hr)

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QQC

• Process developed by Pravin Mistry in mid 1990s• Eliminated problems of adhesion, adjusting to

various substrates, coating thickness and cost• Process creates diamond film through use of

laser energy and carbon dioxide as source of carbon

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QQC Process

• Laser energy directed at substrate to mobilize, vaporize and react with primary element (Carbone) to change crystalline structure of substrate• Conversion zone created

beneath substrate surface• Changes metallurgically

to composition of diamond coating on surface

• Diffusion bonding of diamond coating to substrate

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Major Advantage of the QQC Process

• Superior bonding and reduced stress form metallurgical bond between diamond and substrate• Diamond-coating process can be carried out in

atmosphere (no vacuum needed)• Parts do not require pretreatment or preheating

to be coated

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More Advantages

• Only carbon dioxide primary or secondary source for carbon; nitrogen acts as shield• Diamond deposition rates exceed 1 micron per

second• Process can be used for wide variety of materials• Tool life up to 60 times better than tungsten

carbide and 240 times better than high-speed steel

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Thank You!!!