surfacetreatment-materials and manufacturin g

surface treatement

1. By AKANKSHA MISHRA

2. Introduction
Surface modification of materials-
•Actof modifying the surface of a material by bringing physical,
chemical or biological characteristics different from the ones
originally found on the surface of a material.
•Simply, this process, affect either a thin layer on the surface of the
part itself, or add a thin layer on top of the surface of the part.
Why we use surface treatment?
•Improves hardness and durability
•Rebuild surface
•Controls friction, reduces, adhesion, improves lubrication
•Improves corrosion resistance
•Improves aesthetics(beauty)

3. Surface modification of material-
Types-
1)Mechanical hardening of the surface
2)Case Hardening
3)Thermal spraying
4)Vapor deposition
5)Electroplating
6)Electrolessplating
7)Anodizing
8)Painting

4. Mechanical hardening of the surface-
Mechanical hardening of the surface is a surface treatment which
creates a plastically deformed strain hardened layer of material
itself, by the application mechanical impulses(e.g.-light
hammering).
This process include:-
a)Shot peening
b)Water peening
c)Laser peening
d)Explosive hardening

5. a)Shot peening-
(Uses tiny balls of metal or ceramic)
•The surface get plastically deformed.
•Make the surface harder.

6. b)Water jet peening-
(uses a jet of water at high pressures e.g.-400MPa)
•Uses cavitation impacts in the same way as shot peening.
•Used to improve fatigue strength and/or to introduce compressive
residual stress.
•In the case of cavitation peening, cavitation is generated by
cavitatingjet.

7. c)Laser peening-
(surface is hit by tiny impulses from a laser)
•The surface of the work piece is subjected to laser shocks.
•As a result of which compressive stress is induced in the
component, thus improving the fatigue life.
•Specification-
Laser intensity-100 to 300 J/cm2
Pulse duration-30 sec

8. Laser hardening application-
An expensive process used to improve fatigue strength of jet fan
blades and turbine impellers.

9. d)Explosive hardening-
(Layer of explosive roatedon the surface is blasted)
•The explosion hardening technique can obviously increases the
hardness of metals by several plastic deformation caused by the
shock wave.
Explosive hardening application-
The most common application
of explosive shock hardening
is to cost high-mega steel rail
frogs and switching.

10. Case Hardening-
•Basically, the component is heated in an atmosphere containing
elements (such as C/N/B) that alter the component, microstructure
and properties of surface. (Doping)
•The duration and temperature control the concentration and depth
of the doping.
•Mostly this process is used to harden steel and other iron alloys,
including low carbon steels, alloy steels, tool steels.

11. Types of case hardening-

13. Thermal Spraying-
•Metalismeltedinaspeciallydesignedspraygun.
(usingoxy-fuel,plasma,orothermeanstoheatthesprayedmetaltill
itmelts)
•Highpressuregasthenspraystheliquidmetal
•depositingalayerontopthepart(similartoapaintingprocess).

14. Types of thermal spraying-
A.Thermal wire spray
B.Thermal metal powder spray
C.Plasma spray

15. Thermal wire spray-
•Thefeedstockisinwireorrodform.
•Metaldropletsatomizedbyairjetsusingacetyleneorhydrogen,
whichmixedwithoxygenandburnedatthenozzle'sface.
•Coatingtexture-200microinchto800microinch
•Commonlysprayedmaterials-Zn,Al

16. Thermal metal powder spray-
•Powder feed instead of wire
•Oxyacetylene torch modified for powder feed
•No high pressure air to assist atomization: low deposition rate
•Easy method for materials that cannot be made into wire.

17. Plasma spray-
•Thematerialtobedeposited(feedstock)isintroducedintothe
plasmajet,emanatingfromaplasmatorch.
•Inthejet,wherethetemperatureisoftheorderof10,000K,the
materialismeltedandpropelledtowardsasubstrate.
•There,themoltendropletsflatten,rapidlysolidifyandforma
deposit.

18. Vapor Deposition-
They are of two types-
1)Physical vapor deposition(PVD)
2)Chemical vapor deposition(CVD)
Physical vapor deposition(PVD)
Familyofprocessesinwhichamaterialisconvertedtoitsvapor
phaseinavacuumchamberandcondensedontosubstratesurfaceasa
verythinfilm.
•Coatingmaterials:metals,alloys,ceramicsandotherinorganic
compounds,evensomepolymers
•Substrates:metals,glass,andplastics
•Veryversatilecoatingtechnology
oApplicabletoanalmostunlimitedcombinationofcoatingsand
substratematerials

19. Applications of PVD-
•Antireflectioncoatingsofmagnesiumfluoride(MgF2)onto
opticallenses
•Depositingmetaltoformelectricalconnectionsinintegrated
circuits
•Coatingtitaniumnitride(TiN)ontocuttingtoolsandplastic
injectionmoldsforwearresistance

20. Chemical vapor deposition(CVD)
Involvesinteractionbetweenamixtureofgasesandthesurfaceofa
heatedsubstrate,causingchemicaldecompositionofsomeofthegas
constituentsandformationofasolidfilmonthesubstrate.
•Reactionsoccurinenclosedreactionchamber
•Reactionproductnucleatesandgrowsonsubstratesurfacetoform
thecoating
•MostCVDreactionsrequireheat
•Varietyofcoatingandsubstratematerials

21. Application of CVD-
•Industrial metallurgical processes
•Coated carbide tools
•Solar cells
•Refractory metals on jet engine turbine blades
•Integrated circuit fabrication
Photomicrograph of cross
section of a coated carbide
cutting tool using CVD
and PVD

22. Sputtering-
•An electrical field ionizes an inert gas(Ar).
•Ions are generated and directed at a target.
•The ions sputter target atoms.
•The ejected atoms are transported to the substrate.
•Atoms condense and form a thin film.

23. Electroplating-
•Electroplatingistheprocessofdepositingonemetalontoanother
metal.
•Electronstravelfromthenegativeendofthebatterythroughthe
cathode,throughthesolution,upthroughtheanode,andintothe
positiveendofthebattery.
•Thepositivelychargedionformthesolutionareattractedtothe
negativelychargedcathode.
•Theseionsattachedthemselvestothecathode.
Electroplating can enhances-
Chemicalproperties-increase corrosion
resistance
Physical properties-increase thickness
of part
Mechanical properties-increase tensile
strength & hardness

24. Electrolessplating-
•Partissubmergedintoanaqueousbathfilledwithmetalsalts,
reducingagentsandcatalysts.
•Catalystsreducemetaltoionstoformthecoating.
•Thisprocesscanbeusedtoplatenonconductingpartswithalayer
ofmetal.
•Excellentforcomplexgeometriesasdepositionisuniformacross
surfaceregardlessofgeometry(exceptverysharpcorners(0.4mm
radii)

25. Anodizing-
•The process uses the metal as an anode, by electrolytic process a
layer of hard metal oxide is formed at the anode i.e. on the surface of
the part.
•The coating provided on the metal surface may be of different colors
(usually black, red, blue)
•Electrolytic treatment produces a stable oxide layer on the metallic
surface
•Applications: Aluminium, Magnesium, zinc, titanium, and other
metals
•Dyes can be incorporated into anodizing process to create a wide
variety of colors
•Especially common in aluminium anodizing
•Functions: primarily decorative; also corrosion protection

28. INTRODUCTION
•PAINT is a solution of a pigment in
water, oil, or organic solvent, used to
cover wood or metal articles either for
protection from moisture and termites
etc.
•For different surfaces different types
of paints from different companies are
used. Some of the leading companies
of India are Asian paints, Nerolac,
berger, nipponetc.

29. Paints are of three types:
A.Enamel:oil-basedpaintsthatproduceasmoothsurfaceandglossy
appearance
B.Lacquers:theseareresinbasedpaintsthatdrytoathincoatafter
thesolventevaporatesout.Commonexamplesarevarnishusedin
paintingwood.
C.Water-basedpaints:commonexamplesincludeseveralwallpaints
andhome-interiorpaints.
Lacquers Water-based

30. The most common methods of paint application include:
I.Dip coating: Part is dipped into a container of paint, and pulled
out.
II.Spray coating: One or more spray guns move along the surface of
the part to give a uniform coat of paint; this is the method most
commonly used in painting auto bodies, home appliances, e.g.
fridge doors, etc.
III.Electrostatic spraying: Here the paint particles are given an
electrostatic charge and the spray is achieved by applying a
voltage difference across the paint particles and the part.
IV.Silk-screening: This is the most common method of painting
patterns, text, etcon top of most products. Tine holes are made in
a thin (silk-like) sheet, corresponding to the pattern that needs to
be painted. The screen is kept on top of the part in the correct
position, and the paint is poured n top of the screen. A roller (or
squeegee brush) is used to squeeze the paint out through the holes
in the silk screen and onto the part. The screen is removed and the
part is sent to dry in an oven.

31. Silkscreeninghasseveralveryimportantuses:
1.Itisusedextensivelyinthetextileindustrytocreatecolored
patternsontextiles(e.g.logosonT-shirts).
2.Itisusedtopaintalmostalltextandpatternsonallelectronics
products–e.g.allnumbers,textandsymbolsonyourmobile
phone.
3.Itisusedtodepositpatternsofsolder-pasteontopofprintedcircuit
boards.Lead-lesselectronicchipsareplacedontopofthese
patterns,andaprocesscalledwave-solderingthensoldersthechip
tothecircuitboard.Wewillseethisprocessindetaillater.

32. Silk screening process-

33. ACKNOWLEDGEMENT
I wish to express my sincere gratitude to Dr.Jyoti
Pandeyfor providing me an opportunity to give my
presentation on “Surface Modification”
I sincerely thank Dr.JyotiPandeyfor their guidance and
encouragement in carrying out this presentation work. I
also wish to express my gratitude to my class friends of
BBAU, who rendered their help during the period of my
presentation work.