Surface treatment processes

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Shot peening

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Shot peening• Work piece is impacted

repeatedly• Large number of small

balls of – Cast –steel shot– Glass sheets shots– Ceramic shot

• Size– 0.125mm to 5mm

diameter• Overlap indentations of

1.25mm deep

• Imparts compressive residual stress

• Improve fatigue life• Used in

– Shafts– Gears– Springs– Oil well drilling equipments– Jet engine parts – e.g. Turbine blades

Compressor blades.

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Water jet peening

Water jet peening

• Pressure– As light as 400MPa

• Impinges surface• Induces compressive residual stresses

similar to sheet peening

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laser shot / laser peening

Laser shot peening

• Laser shocks• High power laser • Up to 1kw• Applied on jet –engine fan blades of

– Titanium alloy– Nickel alloy

• Compressive residual stress is deeper– Then 1mm.

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Ultrasonic peening

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Ultrasonic peening

• Uses tools based on– Piezoelectric transducers

• Operating frequency– 22khz

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Roller burnishing (Surface rolling)

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Rollers Burnishing• Surfaces are

– Cold rolled • Hard and highly polished

rollers– Series of rollers

• Can be used for – Flat surfaces – Cylindrical surfaces– Conical surfaces

• Improves– Surfaces finish– Corrosion resistance– Mechanical properties

• Remove– Scratches– Tool marks– Pits etc

• Can be employed on– Soft martial – Hard martial – e.g. seals– Values– Spindle– Fillets on shafts– Ball burnishing is applied

burnishing internal surfaces.

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Explosive hardening

Explosive hardening• PA&E’s Bonded Metals Division

– employs an explosive shock hardening metal working technique

– to generate a work-hardened surface on a fabricated metal part

– similar to results achieved through peen hardening.– During the hardening operation,

• explosive materials are applied directly to the metallic surface to be hardened and are detonated,

• driving the resultant forces into the metal surface. • The operation, essentially cold, • works the metal surface • hardening can be induced up to 1/4″ deep.

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Explosive Hardening Applications

• The most common application – to cast high-manganese steel rail frogs and– switching's.

• Other mining and excavating applications– Hadfield’s steel and modified Hadfield’s alloys.

• Limited research has implied that rhenium can also be hardened through explosive shock hardening.

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Explosive hardening

• Surface are subjected to– High transient pressures– A layer of explosive sheet is placed directly on the

work surface– Pressures

• Up to 35GPa• 2 to 3µs

• Large increase in surface hardness• Little change in shape < 5%

– e.g.• rail road rail

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Cladding

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Cladding• Bonded with thin layer of

– Corrosion-resistant metal– By applying pressure– Through

• rolls• Dies• Explosives etc.

• Multiple-layer cladding– e.g.1.Aluminium clad over

• Aluminium alloy– 2. steel over stainless steel

• Laser-cladding– Fusion of metal on substrate

• e.g. metal on ceramics– Enhances wear resistance

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Mechanical plating(mechanical coating, impact plating,

peen plating)

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Mechanical Plating is a surface-treatment process for coating parts, iron and steel with a metal layer of zinc, tin as their alloys which protects them against corrosion.

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Steps involved in Mechanical plating

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Mechanical plating• Mechanical coating• Impact plating• Peen plating

– Fine metal particles• Coated over work surface• By impacting

– Spherical glass– Ceramic– Porcelain beads

• Applications– Hardness steel parts for

• Automobile– Thickness

• 0.25 µm25

Case hardening

• Carburising• Carbo-nitriding• Cyaniding• Nitriding• Flame hardening• Induction hardening

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Low Pressure Carburizing and High Pressure Gas

Quench

Gas Nitriding

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Nitriding Furnace

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Cyaniding

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Flame hardening

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Induction hardening

Case hardingFerrous alloy• Carburising

• Heating in carboneous atmosphere • quenching

• Carbo-nitriding• Heating in carboneous and

ammonia atmosphere• Quenching

• Carbo-nitriding• Heating in carboneous and

ammonia atmosphere• Quenching

• Cyaniding• Heated in molten bath of cyanide

solution sodium cyanide

• Nitriding• Heated in ammonia gas

• flame hardening• Heated in oxyacetylene flame• Quenched

• Induction hardening• Placed in induction coil• High frequency current • Quenched

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Hard facing

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Hard facingDepositing• Thicker layer of wear –

resistance material– Tungsten carbide– Chromium– Molybdenum carbide

• Using electric arc• Alloys available as

– Electrodes– Rods– Wire– Powder

• e.g. (applications)– valve seats– oil directly tools– dies for hot working– worn parts

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Thermal spraying

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Thermal spraying• Also called metalizing• Metal in form of

– Rod– Wire– Powder

• Melted through– Oxyacetylene flame– Electric arc– Plasma arc

• Sprayed on to a preheated surface

• Speed– 100 m/s– Compressed air spray gun

• e.g. Applications– Automobile parts– Steel structures– Storage tanks– Rocket –motor nozzles– Tank cars

• Thickness – up to 0.25mm

• Metal sprayed – Zinc– Aluminium

• Cold spraying is recent process

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Surface texturing

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Texturing effects of low-energy UV irradiation

Surface texturing

May be obtain through• Etching• Electric arcs• Laser pulses• Atomic oxygen

– React to produce• Fine• Cone like surface texture

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Surface texturing

• For– Technical– Functional– Optical– Aesthetic resources

• Processing– Etching– Electric arcs– Laser pulses– Atomic oxygen

• Reacts and provide cone like texture

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Ceramic coating

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CERAMIC COATING• Spraying ceramic coating• For high temperature• Electric –resistance

– to with stand repeated arcing• Powder of

– hard metal– ceramic

• Sprayed on materials• Heat –treated

– plasma-arc – -15, 273 K

• Application – Nozzle for rocket motors– wear resistant parts

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Vapour deposition

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Ion Vapor Aluminum Deposition System from Ipsen

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Physical vapour deposition by Noken

VAPOUR DEPOSITION• Treated with chemically reactive

gases• Deposited material –a few µm thick• Consists

– Metal– Alloy– Carbide– Nitrides– Borides– Ceramic– Oxide

• Substrate (work piece)may be– Metal– Plastic– Glass– Paper

• Application– Coating for– Cutting tool– Drill– Reamers– Milling cutter– Punches– Dies– Wear surfaces

• Major vapour deposition process– Physical (PVD)– Chemical (CVD)

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Physical vapour deposition

• Particle transported physically• Carried in a high vacuum• At temperature 473 K to 773 K

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Chemical vapour deposition• Thermo chemical process

– e.g. tool placed on graphite tray • Heated

– to 1223-1323 K – in an inert atmosphere pressure

• titanium tetrachloride(vapour)+ Hydrogen + Nitrogen

• Introduced in to the chamber• Form a thin coating of TiN• For titanium carbide coating

– Hydrogen &nitrogen are substituted with • Methane

• Coating obtain are thicker than PVD

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Ion implantation equipment

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ION IMPLANTATION

• Ions at high speed• Onto surface (in a vacuum)

– Penetrate to a depth of few µm

• Resistance to friction– Wear – Corrosion

• Also allow corrosion doping

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Diffusion coating

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Thermal Diffusion coating

Diffusion coating

• Alloying element is diffused into the surface

• Element can be• Solid • Liquid• Gas• e.g-carburizing• nitriding• etc.

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Electroplating

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Electroplating• Work piece (cathode) is electroplating with• Metal (angle)• Both suspended bath coating• Electrolyte• Under electricity• Metal (anode) ions is dislodged• Deposited on work piece (cathode)• Depends upon• Current• Time electro• Chemical equivalent of metal

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Electroless plating

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Electroless plated

Electrodeless plating

• Chemical reactions• Without external source

of electricity• Common application

– Nickel chloride• Reduced with

– Sodium hypo phosphate

• Deposited on work piece

• Hardness– 425 to 575 HV– Heat treated

• 1000HV

• Excellent resistant to– Wear– Corrosion

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Anodizing

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Anodizing

• Oxidation process• Work pieces surfaces

– Converted to oxide layer• Corrosion resistant• Decorative finish• Anode in electrolytic cell

– Immersed in acid bath• Chemical adsorption of

oxygen from bath

• Organic dye of various colours– Black– Red– Brown– Gold– Grey– Stable surface texture

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Continued

• Applications– Aluminium furniture– Utensils– Architectural shapes– Automobile trim– Keys– Sporting goods– Also to provide good base for painting

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Conversion coating

• Also called– Chemical- reaction primary– Chemical or electro chemical

reactions

• Applications• Steel• Aluminium• Zinc etc.• Pre-painting• Decorative finish• Protection against corrosion• Lubricant carrier

– Forging – Extrusion– Wire drawing– Rough and spongy surface

• After treatment borax or lime is used to remove acid

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Coloured stainless steel pipes

Colouring

• Corrosion of surfaces by • Chemical• Electro-chemical• Thermal process in to compound• Oxides• Chromates• Phosphate• e.g. hot caustic soda on iron and steels develop

block-oxide film

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Hot dipping- galvanizing

Hot dipping• Galvanizing (plumbing supplies)• Tin(tin cans for food containers)• Aluminium (aluminizing)• Terve (lead with 10to20 tin)• Coating thickness• In terms of weight/surface area• 150 to 900g /m2

• Coating material depends upon the environment to be exposed

• e.g. automobile bodies • Container• proper drawing to remove extra coating material

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Hot-Dip Galvanizing: Protecting Steel

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PERC® is porcelain enamel powder being sprayed onto a steel part

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Glass frit used to make porcelain enamel.

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Custom Porcelain Enameling A thin layer of glass

Porcelain enamelling• Coating of glassy (vitreous)

substances• Inorganic substances• 0xides• Resistance at elevated

temperature– Electricity– Corrosion– Alkali– Acids– Detergents– Cleanness– Water etc.

• Application– House hold appliances– Plumbing fixtures– Chemical processing

equipments– Sigus– Cook-ware– Jewellery– Jet-Engine components

• Applied on surfaces by– Dipping– Spraying– Electro-depositing

• Thickness – 0.005 mm to 0.6mm

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Organic coating of

metal surfaces

Mechanism of osmotic blistering -

coatings

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Ceramic coating

75Ceramic coating

Ceramic coatings

• For example• Aluminium oxide• Zirconium oxide• Applied a room temperature• Thermal spraying• Serve thermal barrier• Hot extrusion dies• Diesel –engine components• Turbine blades

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METAL SURFACES PAINTING

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METAL SURFACES PAINTING

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PAINTING

• Paints– Enamels– Lacquers– Water base paints

• Process of application– Brushing– Dipping– Spraying– Electro-coating (electrostatic spraying)

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Assorted Diamond Coated Hole Saw Drill BitsSuitable for use in drill hole on glass, marble, tile or granite.

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Diamond coating• Coatings on

– Metals– Glass– Ceramics– plastics

• Processing through– Chemical and plasma-assisted

vapour deposition– Ion beam enhanced deposition

• Film thickness– 1 mm to 125 mm– Smooth– Optically clear– With diamond properties

• Hardness• Wear resistance• High thermal conductivity• Trancperancy to

– Ultra voitlet light– Microwave frequencies

• Applications– Aerospace– Electronic parts and

components– Scratch proof windows– Cutting tools– Measuring

instruments– Light emitting diodes– Turbine blades

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Titankote™ C10 (DLC) Coated End Mill

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Diamond like carbon (DLC)

• Less expensive than diamond

• Deposition process– Low temperature– Ion beam assisted

• Thickness– A few nm

• Hardness– 5000 HV

• Application– Dies– Gear– Bearings– Micro-electro-

mechanical systems– Micro-scale probes

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Metal texture

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Surface texturing

May be obtain through• Etching• Electric arcs• Laser pulses• Atomic oxygen

– React to produce• Fine• Cone like surface texture

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Cleaning of surfaces

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Automatic blast cleaning

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Manual blast cleaning

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Cleaning of surfaces• Cleaning processes

– Mechanical• Wire brushing• Abrasive blasting• Tumbling• Steam jet• Ultrasonic cleaning

– Electrolytic cleaning• Aqueous solution• Bubbles of

– Hydrogen or– Oxygen

• Chemical cleaning• Solution• Saponification• Emulsification• Dispersion• Aggregation

• Cleaning fluids– Alkaline solution– Emulsions– Solvents– Hot vapours– Acids– Salts

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Thanks

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