• Work piece is impacted repeatedly

Surface treatment processes

Shot peening

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.

Water jet

peening

Water jet peening

• Pressure

– As light as 400MPa

• Impinges surface

• Induces compressive residual stresses

similar to sheet peening

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.

Ultrasonic

peening

Ultrasonic peening

• Uses tools based on

– Piezoelectric transducers

• Operating frequency

– 22khz

Roller burnishing (Surface rolling)

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.

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.

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.

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

Cladding

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

Mechanical plating

(mechanical coating, impact plating,

peen plating)

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.

Steps involved in

Mechanical plating

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 µm

Case hardening

• Carburising

• Carbo-nitriding

• Cyaniding

• Nitriding

• Flame hardening

• Induction hardening

Low Pressure Carburizing and High Pressure Gas

Quench

Gas Nitriding

Nitriding Furnace

Cyaniding

Flame hardening

Induction

hardening

Case harding

Ferrous 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

• Nitriding

• Heated in ammonia gas

• flame hardening

• Heated in oxyacetylene flame

• Quenched

• Induction hardening

• Placed in induction coil

• High frequency current

• Quenched

Hard facing

Hard facing

Depositing

• 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

Thermal spraying

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

Surface texturing

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

Surface texturing

• For

– Technical – Functional – Optical

– Aesthetic resources

• Processing

– Etching

– Electric arcs – Laser pulses – Atomic oxygen

• Reacts and provide cone like texture

Ceramic coating

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

Vapour deposition

Ion Vapor Aluminum Deposition

System from Ipsen

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)

Physical vapour deposition

• Particle transported physically

• Carried in a high vacuum

• At temperature 473 K to 773 K

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

Ion implantation equipment

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

Diffusion coating

Thermal

Diffusion

coating

Diffusion coating

• Alloying element is diffused into the surface

• Element can be

• Solid

• Liquid

• Gas

• e.g-carburizing

• nitriding

• etc.

Electroplating

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

Electroless plating

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

Anodizing

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

Continued

• Applications

– Aluminium furniture – Utensils

– Architectural shapes – Automobile trim

– Keys

– Sporting goods

– Also to provide good base for painting

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

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

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 /m

• Coating material depends upon the environment to be exposed

• e.g. automobile bodies

• Container

• proper drawing to remove extra coating material

Hot-Dip Galvanizing: Protecting Steel

PERC® is porcelain enamel powder being

sprayed onto a steel part

Glass frit used to make

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

Organic coating of

metal surfaces Mechanism

of osmotic blistering -

coatings

Ceramic

coating

Ceramic 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

METAL SURFACES PAINTING

METAL SURFACES PAINTING

PAINTING

• Paints

– Enamels – Lacquers

– Water base paints

• Process of application

– Brushing – Dipping – Spraying

– Electro-coating (electrostatic spraying)

Assorted Diamond

Coated Hole Saw Drill Bits

Suitable for use

in drill hole on

glass, marble,

tile or granite.

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

Titankote™ C10 (DLC)

Coated End Mill

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

Metal texture

Surface texturing

May be obtain through

• Etching

• Electric arcs

• Laser pulses

• Atomic oxygen

– React to produce

• Fine

• Cone like surface texture

Cleaning of surfaces

Automatic blast cleaning

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

Thanks