EM-IPE-101.pdf

Engineering Materials (IPE– 101)
Ref: Introduction To Physical Metallurgy - SIDNEY H. AVNER
Material Science and Engineering: An Introduction - William D. Callister Jr.
Md. Mamunur Rashid
Lecturer, Department of IPE
Bangladesh University of Textiles

Plain Carbon Steel - Structure
2
• It contains no carbon
• It contains very small quantities of
impurities such as phosphorus, silicon,
manganese, oxygen, nitrogen,
dissolved in the solid metal.
• The structure is typical of pure metals
and solid solutions in the annealed
condition.
• It is built up of a number of crystals of
the same composition - ferrite.

Lattice Structure (BCC, FCC)
3
BCC FCC

Lattice Structure (BCC, FCC)
4
BCC FCC

Solubility of Carbon in Fe
(Temperature Vs Structure)
5
Let’s Reduce the temperature of
Liquid Fe at a slow rate
Sydney H Avner
Page – (225-248)

Some Notations to Remember
6
= Ferrite (BCC Structure) = Solid (Minimum C - 0.02wt% of C)
α = Low Temp. Ferrite (BCC Structure) = Solid
γ = Austenite (FCC Structure) = Solid
L = Liquid
Fe3C = Cementite/ Iron Carbide = Maximum C(6.67wt% of C)
Ferrite + Cementite = Pearlite (lamellar structure)

Invariant Reactions
7
Eutectic
Eutectoid
Ferrite Austenite
Low C Ferrite
Ledeburite
Peritectic
Cementite
Pearlite

Iron-Cementite Phase Diagram
8

Mathematical Problem
9
Given the Fe-Fe3C phase diagram, calculate the phases present at the
eutectoid composition line at:
a. T = 3000ºF b. T = 2200ºF c. T = 1333ºF d. T = 410ºF

Mathematical Problem
10
Given the Fe-Fe3C phase diagram, calculate the phases present at the
eutectoid composition line at:
a. T = 3000ºF b. T = 2200ºF c. T = 1333ºF d. T = 410ºF
1. a. T = 3000ºF. Since the composition E is eutectoid, the carbon content is 0.83%.
b. T = 2200ºF. At this temperature, austenite exists as a single-phase solid.
c. T = 1333ºF. Two phases exist, ferrite and austenite. The percentages are determined by
the lever rule: X ÷ (X+Y) = (Cy-C) ÷ (Cy-Cx).
Pro-eutectoid ferrite = (0.83 - 0.18) / (0.83 - 0.025) x 100 = 80.7%
austenite = (0.18 - 0.025) / (0.83 - 0.025) x 100 = 19.3%
d. T = 410ºF. A small amount of cementite will precipitate following the solubility line from
0.025% C at 1333ºF to 0.008% C at room temperature. The overall percentages of ferrite
and cementite are:
ferrite = (6.67 - 0.18) / (6.67 - 0.01) x 100 = 97.4%
cémentite = (0.18 - 0.01) / (6.67 - 0.01) x 100 = 2.6%

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Iron-Cementite Phase Diagram -
Microstructure
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Microstructure
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Microstructure
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Transformation of Austenite
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% Carbide
17
Eutectoid: Cm/a = ab/be
= 0.8/6.67 = 14 % = 1:7
Hyper Eutectoid:
%Pearlite = af/ab
= 0.4/0.8 = 50 %
%Ferrite = fb/ab = 50%
Eutectic:
% y = de/ce = 2.67/4.67 = 57%
%P = de/be = 2.67/5.84= 46%
f

Types of Ferrous Alloys
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Classification. Three types of ferrous alloys:
• Iron: less than 0.008 wt % C in α−ferrite at room T
• Steels: 0.008 -2.14 wt % C (usually < 1 wt % )
α-ferrite + Fe3C at room T
• Cast iron: 2.14 -6.7 wt % (usually < 4.5 wt %)
Alloy: A mixture containing two or more metallic elements or metallic and
nonmetallic elements usually fused together or dissolving into each other when
molten

Production Process of Cast Iron
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Cast iron is made by re-melting pig iron, often along with substantial quantities of scrap iron,
scrap steel, lime stone, carbon (coke) and taking various steps to remove undesirable
contaminants.
There are four stages in Cast Iron production;
- Design, - Pattern Making, - Mould Making and - Casting.
Design: a planned approach needed – function & appearance consideration.
the stresses and conditions a machine operates.
architectural - structural ability, supportive strength or decorative embellishment.
Engineers provide detailed, often complex, manufacturing drawings.
Architects supply drawings/elevations which in most cases need to be reproduced as
manufacturing drawings showing precise dimensions, metal thickness etc.
Thus Pattern Making, can progress.
In conservation and restoration projects original samples exist, Occasionally no plans or
drawings needed.

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Pattern Making: After design being approved and manufacturing drawing ok;
a pattern can be made, in wood, fiber glass or plastics.
Patterns have to be exactly the shape of the finished item and precise in their
dimensions as they are used to make the sand moulds.
Patterns can be re-used and,
Patterns can last for many years making thousands of moulds.
Any irregularity or mistake will be reproduced in the casting.
Patterns must allow for shrinkage of the metal by
- when it cools and also create channels or runners to allow the molten metal to flow
- risers to allow for the escape of gases.
Pattern making complex and extremely skilled work.
Trained and highly experienced makers required.

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Mould Making: making a mould in sand into which the molten is poured.
The pattern is packed into sand.
When removed leaves the shape for the casting.
Moulds are in two parts and held in ‘boxes’ for the actual pouring.
Two halves are placed face to face,
A cavity is created - the molten iron is poured.
Runner system - a network of channels that allow the molten metal to run into the mould.
If the molten iron does not run quickly enough it will solidify before it reaches the casting shape
– skill required.
If it runs too quickly or violently it could damage the mould and spoil the casting.
Breaking out the casting - the sand can be recycled and reused by using same pattern.

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Casting: This is the final part of the process associates with foundries.
Melting and pouring iron at 1,350 degrees centigrade is a spectacular and potentially
violent process.
Safety is the highest priority in any foundry.
The furnace is loaded to ensure the correct chemical characteristics for the prescribed
grade of iron are achieved.
The iron is then melted in the furnace & poured off to go into the awaiting moulds.
Slag or foundry waste is put to one side for disposal.
After the iron has cooled in the moulds is broken out.
All the excess iron from the process, the runners etc. are cleaned off in a process known as
fettling, which also includes grinding and shot blasting, to produce a finished casting.

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Cast Iron
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• Grey cast iron - carbon as graphite
• Ductile cast iron -nodular, spheroidal graphite
• Malleable cast iron
• White cast iron - carbides, often alloyed
• Nodular - Compacted graphite cast iron
• Chilled Cast Iron
• Alloy Cast Iron
Types:

Cast Iron
25
• Flake graphite in a matrix of pearlite, ferrite or martensite
• Wide range of applications
• Low ductility - elongation 0.6%
• Grey cast iron forms when
Cooling is slow, as in heavy sections
High silicon or carbon
Grey Cast Iron:

Grey Cast Iron – Graphite Formation
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 Uniform
 Rosette
 Superimposed
 Inter dendritic random
 Inter dendritic preferred
orientation

Grey Cast Iron
27
Properties:
 Machinability is excellent
 Ductility is low (0.6%), impact resistance low
 Damping capacity high
 Thermal conductivity high
 Dry and normal wear properties excellent

Grey Cast Iron
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Application:
 Engines - Cylinder blocks, liners
 Brake drums, clutch plates
 Pressure pipe fittings
 Machinery beds
 Furnace parts, ingot and glass moulds

Cast Iron
29
Ductile Iron:
• Inoculation with Ce or Mg or both causes graphite
to form as spherulites, rather than flakes
• Also known as spheroidal graphite (SG), and
nodular graphite iron
• Far better ductility than grey cast iron

Ductile Iron - Microstructure
30
• Graphite spheres surrounded by
ferrite
• Usually some pearlite
• May be some cementite
• Can be hardened to martensite
by heat treatment

Ductile Iron
31
Properties:
 Strength higher than grey cast iron
 Ductility up to 6% as cast or 20% annealed
 Low cost
 Simple manufacturing process makes
complex shapes
 Machinability better than steel

Ductile Iron
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Application:
• Automotive industry 55% of ductile iron in USA
Crankshafts, front wheel spindle supports,
steering knuckles, disc brake callipers
• Pipe and pipe fittings (joined by welding)

Cast Iron
33
Malleable Iron:
 Graphite in nodular form
 Produced by heat treatment of white cast iron
 Graphite nodules are irregular clusters
 Similar properties to ductile iron

Malleable Cast Iron - Microstructure
34
• Uniformly dispersed graphite
• Ferrite, pearlite or tempered
martensite matrix
• Ferritic castings require 2 stage
anneal.
• Pearlitic castings - 1st stage only

Malleable Cast Iron
35
Ferritic malleable iron
Depends on C and Si
1st stage 2 to 36 hours at 940˚C in a controlled atmosphere
Cool rapidly to 750˚C & hold for 1 to 6 hours
For pearlitic malleable iron
Similar 1st stage above (2 - 36 h at 940˚C)
Cool to 870˚C slowly, then air cool & temper to specification
Harden and temper pearlitic iron for martensitic castings

Malleable Cast Iron
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• Similar to ductile iron
• Good shock resistance
• Good ductility
• Good machinability
Properties:

Malleable Cast Iron
37
• Similar applications to ductile iron
• Malleable iron is better for thinner castings
• Ductile iron better for thicker castings >40mm
• Vehicle components
Power trains, frames, suspensions and wheels
Steering components, transmission and differential parts,
connecting rods
• Railway components
Application:

Cast Iron
38
White Cast Iron:
When the white cast iron is fractured, white
colored cracks are seen throughout because of
the presence of carbide impurities.

White Cast Iron
39
• White cast iron is hard but brittle.
• lower silicon content
• low melting point
• C precipitates and forms large particles that
increase the hardness
• Abrasive resistant as well as cost-effective
Properties:

White Cast Iron
40
• lifter bars and shell liners in grinding mills,
• wear surfaces of pumps,
• balls and rings of coal pulverisers.
Application:

Cast Iron - Others
41
• Chilled cast irons, in which a white cast-iron layer at the
surface is combined with a gray-iron interior.
• Nodular cast irons, in which, by special alloy additions,
the carbon is largely uncombined in the form of
compact spheroids. This structure differs from malleable
iron in that it is obtained directly from solidification and
the round carbon particles are more regular in shape.
• Alloy cast irons, in which the properties or the structure
of any of the above types are modified by the addition
of alloying elements.

Cast Iron
42
Comparative qualities of cast irons
Name
Nominal
composition
[% by
weight]
Form and
condition
Yield
strength
[ksi(0.2%
offset)]
Tensile
strength [ksi]
Elongation
[% (in
2 inches)]
Hardness [
Brinell scale]
Uses
Grey cast
iron
C 3.4,
Si 1.8,Mn 0.5
Cast — 50 0.5 260
Engine cylinder
blocks, fly wheels,
gearbox cases,
machine-tool
bases
White cast
iron
C 3.4, Si 0.7,
Mn 0.6
Cast (as
cast)
— 25 0 450 Bearing surfaces
Ductile
iron
C 3.4, P 0.1,
Mn 0.4, Ni 1.
0, Mg 0.06
Cast 53 70 18 170
Gears, camshafts,
crankshafts
Malleable
iron
C 2.5, Si 1.0,
Mn 0.55
Cast
(annealed)
33 52 12 130
Axle bearings,
track wheels,
automotive cranks
hafts

Effect of Impurities in Cast Iron
43
The effects of impurities on the cast iron are as follows:
Silicon It may be present in cast iron up to 4%. It provides the formation of free
graphite which makes the iron soft and easily machinable. It also produces
sand castings free from blow-holes, because of its high affinity for oxygen.
Sulphur It makes the cast iron hard and brittle. Since too much Sulphur gives
unsound casting, therefore, it should be kept well below 0.1% for most foundry
purposes.
Manganese It makes the cast iron white and hard. It is often kept below 0.75%. It
helps to exert a controlling influence over the harmful effect of Sulphur.
Phosphorus It aids fusibility and fluidity in cast iron, but induces brittleness. It is
rarely allowed to exceed 1%. Phosphoric irons are useful for casting of intricate
design and for many light engineering castings when cheapness is essential.

Hardness & Measuring Methods
44
Hardness is defined as the ability of a material to resist plastic deformation.
- Not a physical constant
- a complex property that depends on the strength and plasticity of the metal
- It also depends on the method of measurement.
It is denoted quantitatively by Hardness Number.
Measurement Methods:
- Brinell,
- Vickers
- Rockwell
- Micro-hardness etc.

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The indentation test: most commonly used
The hardness is equal to the load relative to the area of indentation or
inversely proportional to the depth of indentation for a specified load.
The indentation is usually made with
- a hardened steel ball (Brinell test, Rockwell test),
- a diamond cone (Rockwell test),
- a diamond pyramid (Vickers test, micro hardness test).
Impact loading -
hardness is measured by the rebound height of a small steel ball dropped
onto the surface of the metal(Shore test)
Ultrasonic vibrations - the response of an oscillating system (change in natural frequency)
hardness is measured.

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Unit of Hardness Number:
• HB (Brinell test),
• HV (Vickers test),
• HR (Rockwell test),
with H standing for hardness.
Special tables and diagrams are available for converting a
Hardness number unit to another Unit.
The choice of a hardness test depends on factors like –
• material being tested,
• the dimensions,
• shape of the specimen or article.

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Hardness is very sensitive to changes in the metal structure.
Since the hardness of metals and alloys changes
- with a change in temperature or
- after various types of thermal and mechanical treatment.
Indentation Hardness:
According to the forces applied and displacements obtained Hardness measurement can
be defined as macro-, micro- or nano- scale.

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Measurement of the macro-hardness of materials is a quick and simple method of obtaining
mechanical property data for the bulk material from a small sample.
Used for the quality control of surface treatments processes.
However, when concerned with coatings and surface properties of importance to friction and
wear processes for instance, the macro-indentation depth would be too large relative to the
surface-scale features.
Demerits: Materials having fine microstructure, are multi-phase, non-homogeneous or prone to
cracking, macro-hardness measurements will be highly variable and will not identify individual
surface features. It is here that micro-hardness measurements are appropriate.

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Micro-hardness is the hardness of a material as determined by forcing an indenter such as a
Vickers or Knoop indenter into the surface of the material under 15 to 1000 gf load; usually,
the indentations are so small that they must be measured with a microscope.
Capable of determining hardness of different micro constituents within a structure.
Conversions from micro hardness values to tensile strength and other hardness scales (e.g.
Rockwell) are available for many metals and alloys.
Micro-indenters works by pressing a tip into a sample and continuously measuring: applied
load, penetration depth and cycle time.

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Nano-indentation tests measure hardness by indenting using very small, on the order of 1
nano-Newton, indentation forces and measuring the depth of the indention that was
made.
These tests are based on new technology that allows precise measurement and control
of the indenting forces and precise measurement of the indentation depths.
By measuring the depth of the indentation, progressive levels of forcing are measurable
on the same piece.
This allows the tester to determine the maximum indentation load that is possible before
the hardness is compromised and the film is no longer within the testing ranges.
This also allows a check to be completed to determine if the hardness remains constant?
even after an indentation has been made.

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Method of force application is using a coil
and magnet assembly on a loading
column to drive the indenter downward.
This method uses displacement gauge.
Such gages detect displacements of 0.2
to 0.3 NM (nanometer) at the time of force
application. The loading column is
suspended by springs, which damps
external motion and allows the load to be
released slightly to recover the elastic
portion of deformation before measuring
the indentation depth.

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Brinell hardness is determined by forcing a hard steel or carbide sphere of a specified
diameter under a specified load into the surface of a material and measuring the
diameter of the indentation left after the test. The Brinell hardness number, or simply the
Brinell number, is obtained by dividing the load used, in kilograms, by the actual surface
area of the indentation, in square millimeters. The result is a pressure measurement, but the
units are rarely stated.
The BHN is calculated according to the following formula:
where
BHN = the Brinell hardness number
F = the imposed load in kg
D = the diameter of the spherical indenter in mm
Di = diameter of the resulting indenter impression in mm

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Vickers hardness is a measure of the hardness of a material, calculated from the size of
an impression produced under load by a pyramid-shaped diamond indenter.
The indenter employed in the Vickers test is a square-based pyramid whose opposite
sides meet at the apex at an angle of 136º.
The diamond is pressed into the surface of the material at loads ranging up to
approximately 120 kilograms-force, and the size of the impression (usually no more than
0.5 mm) is measured with the aid of a calibrated microscope.

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The Vickers number (HV) is calculated using the following formula:
HV = 1.854(F/D2)
with F being the applied load (in kilograms-force)
and D2 the area of the indentation (in square millimeters)

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The Rockwell Hardness test is a hardness measurement based on the net increase in depth of
impression as a load is applied. Hardness numbers have no units and are commonly given in
the R, L, M, E and K scales. The higher the number in each of the scales means the harder the
material.
The indenter may either be a steel ball of some specified diameter or a spherical diamond-
tipped cone of 120° angle and 0.2 mm tip radius, called Brale. The type of indenter and the
test load determine the hardness scale.
A minor load of 10 kg is first applied, which causes an initial penetration and holds the
indenter in place. Then, the dial is set to zero and the major load is applied. Upon removal of
the major load, the depth reading is taken while the minor load is still on. The hardness
number may then be read directly from the scale.

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A - Cemented carbides, thin steel and shallow case hardened steel
B - Copper alloys, soft steels, aluminum alloys, malleable iron, etc.
C - Steel, hard cast irons, pearlitic malleable iron, titanium, deep case hardened
steel and other materials harder than B 100
D - Thin steel and medium case hardened steel and pearlitic malleable iron
E - Cast iron, aluminum and magnesium alloys, bearing metals
F - Annealed copper alloys, thin soft sheet metals
G - Phosphor bronze, beryllium copper, malleable irons
H - Aluminum, zinc, lead
K, L, M, P, R, S, V - Bearing metals and other very soft or thin materials, including
plastics.

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Accuracy of Any Indentation Hardness Test:
1) Condition of the Indenter
2) Accuracy of Load Applied
3) Impact Loading
4) Surface Condition of the Specimen
5) Thickness of the specimen
6) Shape of the specimen
7) Location of Impression
8) Uniformity of Materials

Plastics – Properties and Uses
58
Elastomer is a polymer with viscoelasticity (having both viscosity and elasticity) and very
weak inter-molecular forces, generally having low Young's modulus and high failure strain
compared with other materials. When elastomers are vulcanized, they are called Rubber.
Each of the monomers which link to form the polymer is usually made of carbon, hydrogen,
oxygen or silicon. e.g. Natural poly-isoprene, Synthetic poly-isoprene, Poly-butadiene, EPM
(ethylene propylene rubber), Epi-chloro-hydrin rubber (ECO), Poly-acrylic rubber (ACM, ABR),
Silicone rubber (SI, Q, VMQ), Fluoro-silicone Rubber (FVMQ)

59
Fiber is a natural or synthetic string used as a component of composite materials, or, when
matted into sheets, used to make products such as paper, papyrus, or felt. Synthetic fibers can
often be produced very cheaply and in large amounts compared to natural fibers, but for
clothing natural fibers can give some benefits, such as comfort, over their synthetic
counterparts. e.g. Vegetable Fibers, Wood Fiber, Animal Fiber, Mineral Fiber, Metallic Fibers,
Carbon Fibers, Fiberglass etc.
Plastic is a material consisting of any of a wide range of synthetic or semi-synthetic organics
that are malleable and can be molded into solid objects of diverse shapes. Plastics are
typically organic polymers of high molecular mass, but they often contain other substances.
Due to their relatively low cost, ease of manufacture, versatility, and imperviousness to water,
plastics are used in an enormous and expanding range of products, from paper clips to
spaceships. Traditional materials, such as wood, stone, horn and bone, leather, paper, metal,
glass, and ceramic are displaced by Plastics. e.g. PES, PET, PE etc.

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Plastics fit into two categories - Thermoplastics and Thermosetting plastics. These
two have different properties and therefore the type of plastic used depends on
the use and product.
- Thermoplastic = heated & re-shaped
- Thermosetting = no re-shaping.

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Rubber – Properties and Uses
68
A common classification of different types of rubber is:
• General purpose elastomers
• Special purpose elastomers
• Specialty elastomers

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General purpose elastomers:
• Have good physical properties,
• good process ability and compatibility,
• economical and are typical polymers used in tyres,
• Rubber products are for good abrasion resistance and tensile properties.
General purpose types constitute the largest volume of polymer used.
3 types:
o Natural rubber (NR)/ Poly-isoprene rubber (IR)
o Styrene-butadiene rubber (SBR)
o Butadiene rubber (BR)

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Special purpose elastomers:
They have all unique properties which cannot be matched by the general purpose types
are very important for manufacturing of industrial and automotive rubber products.
4 types:
o Ethylene-propylene rubber (EPM and EPDM)
o Butyl rubber (IIR)
o Chloroprene rubber (CR)
o Acrylonitrile-butadiene rubber or Nitrile rubber (NBR)

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Speciality elastomers:
are a great number of polymers with very special properties, in many cases of
great importance for the aircraft-, space- and offshore industries.
Some of these polymers are:
o Chloro-sulfonated Polyethylene (CSM)
o Acrylic Rubber (ACM)
o Silicone Rubber (PMQ/PV/MQ/VMQ)
o Flour-silicone Rubber (FPQ)
o Fluor elastomers (FPM/FFKM/FEPM)
o Urethane Rubber (AU/EU)
o Epi-chloro hydrine Rubber (CO/ECO/GECO)

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1) NATURAL RUBBER
Natural rubber is the only non-synthetic rubber and has been in commercial use since the
beginning of the 20th century. It is extracted from the sap of the Hevea Brasiliensis tree grown in
renewable plantations. It is fully biodegradable.
Tensile strength, elongation and abrasion resistance is excellent over a wide hardness range, and
with the exception of certain formulations of poly-butadiene, it has the highest resilience of all
rubbers. With its good tear strength, fatigue resistance and excellent compression set it is the ideal
choice for dynamic applications at low and ambient temperatures. Weathering resistance is good
for black compounds but only fair for white and colored mixes.
Although natural rubber can be used with water and some dilute acids, alkalis and chemicals,
EPDM is normally preferable for most aqueous applications. Natural rubber compounds are not
suitable for exposure to petroleum based oils and fuels. It has poor resistance to elevated
temperatures and is susceptible to attack by ozone unless specifically compounded with anti-
ozonants.
Typical applications include anti-vibration mounts, drive couplings, haul-off pads and tires.

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2) STYRENE BUTADIENE RUBBER
Styrene Butadiene Rubber (SBR) is one of the cheaper general purpose rubbers. Its physical
strength, resilience and low temperature properties are usually inferior to Natural Rubber
though heat-aging properties and abrasion resistance are better.
SBR is not resistant to oil or fuel resistant and it can be prone to weathering.
Typical applications include drive couplings, haul-off pads, shoe soles/heels and car tyres.
3) BUTTADIENE RUBBER
Polybutadiene was one of the first types of synthetic elastomer, or rubber, to be invented. It
didn't take a great a degree of imagination to come up with, as its very similar to natural
rubber, polyisoprene. It's good for uses which require exposure to low temperatures. Tires
treads are often made of polybutadiene copolymers. Belts, hoses, gaskets and other
automobile parts are made from polybutadiene, because it stands up to cold
temperatures better than other elastomers. Many polymers can become brittle at low
temperatures thanks to a phenomenon called the glass transition.

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4) EPDM
Ethlylene Propylene Diene Monomer is a copolymer of ethylene and propylene and a
smaller amount of a diene monomer which forms chemically unsaturated ethylene
groups pendant from the main saturated chain. These facilitate cross-linking reactions
which do not affect the integrity of the polymer backbone. This feature gives EPDM
excellent heat, ozone and chemical resistance. Physical properties are very good and
resistance to polar fluids is generally good. Low temperature resistance is very good and
EPDM can be compounded to give excellent electrical resistance.
EPDM is not suitable for exposure to petroleum based fluids and di-ester lubricants.
Typical applications include accumulator bladders, cable connectors and insulators,
diaphragms, gaskets, hoses and seals.
Potable water (WRC/WRAS) grades are available as well as ‘Food Quality’ mixes suitable
for the food and pharmaceutical industries.

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5) BUTYL RUBBER
Butyl, also known as Isobutylene-isoprene (IIR), is a synthetic rubber developed in the 1940’s. It
has exceptionally low gas permeability making it ideal for inner tubes and high
pressure/vacuum sealing applications. Its very low resilience makes it suitable for shock and
vibration damping. Its chemical unsaturation gives it excellent resistance to heat, ozone, and
weathering, and also to dilute acids and alkalis.
It is not suitable for use in mineral or petroleum based fluids.
Typical applications include diaphragms, gaskets, inner tubes, liners, O-rings, seals, speaker
surrounds and bottle closures.
6) CHLOROPRENE RUBBER
Chloroprene Rubber (CR), widely known as Neoprene, was one of the first oil resistant synthetic
rubbers. However, it has only moderate resistance to petroleum based oils and fuels. It can be
considered as a good general purpose rubber with an excellent balance of physical and
chemical properties. Chloroprene tends to slowly absorb water and its electrical properties are
poor. Its gas permeability is fairly low and flame resistance is excellent, chloroprene being one of
the few rubbers that are self-extinguishing. Neoprene gives excellent rubber-metal bonds and
good resilience. Certain grades of Neoprene may crystallize and harden during storage
although they will thaw on heating.
Chloroprene is widely used because of its wide range of useful properties and reasonable price.
Typical applications include belting, coated fabrics, cable jackets, seals and gaiters.

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7) NITRILE RUBBER
Acrylonitrile Butadiene Rubber, usually shortened to Nitrile, was developed in 1941 as the first oil
resistant rubber. Grades with high acrylonitrile content have better oil resistance whereas low
acrylonitrile content gives better low temperature flexibility and resilience. Nitrile has moderate
physical properties but good abrasion resistance. Gas permeability is low.
Ozone resistance and electrical properties are poor. Flame resistance is poor and it is not suitable
for use with use with polar solvents (e.g. MEK).
Certain grades can be compounded with PVC to improve ageing, flame, petrol and ozone
resistance. Carboxylated grades of Nitrile (XNBR) have improved physical properties and higher
temperature resistance. Potable water (WRC/WRAS) compounds are available as well as mixes
suitable for use in the food and pharmaceutical industries.
Typical applications include accumulator bladders, diaphragms, gaskets, hose, liners, O-rings
and seals.

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8) HYPALON RUBBER
Chloro-sulphonated Polyethylene (CSM), widely known as Hypalon, can in some respects be
regarded as a superior type of chloroprene, having better heat ageing, chemical resistance
and excellent low gas permeability. Ozone and weathering resistance is also excellent and
electrical properties are good. Low temperature flexibility and oil resistance is similar to
chloroprene.
Hypalon has poor fuel resistance and dynamic sealing applications are not recommended in
view of its poor compression set.
Typical applications include static seals and any components likely to suffer hot and humid
weather conditions or exposure to hot liquids and gases.
9) POLYACRYLIC RUBBER
The key properties of Poly-acrylic (ACM) are its resistance to hot hydraulic oil and oxidation. It
is also resistant to ozone and weathering and in these respects it is much superior to Nitrile
Rubber.
Water resistance is poor, as is its resistance to acids and alkalis. Low temperature applications
are limited to -10°C. Poly-acrylic has very low resilience below 70°C and has found use in
vibration damping.
Typical applications include automotive transmissions components requiring resistance to hot
oil or fuel.

78
11) FLUOROSILICONE RUBBER
Fluoro-silicones can operate over a very wide range of temperatures (-60°C to +200°C) and
their resistance to di-ester lubricants, ozone and weathering is excellent. They have good
electrical strength and moderate oil resistance.
However, they are particularly expensive rubbers and unsatisfactory for use with phosphate
esters. Like Silicone rubbers, their physical properties and permeability to gases are poor.
Typical applications include aerospace fuel system components, diaphragms, gaskets, hose
lining, seals and O-rings.
10) SILICONE RUBBER
Silicone Rubbers are ideal for high and low temperature applications. Electrical properties are
excellent and resistance to weathering and ozone attack is outstanding.
It is not resistant to super-heated steam. Physical properties are generally low but are at least
retained at higher temperatures. Gas permeability is very poor as is resistance to petroleum
based fluids. Silicone rubbers are expensive in comparison to most other rubbers.
Food Quality/FDA compliant grades are available for use in the food and pharmaceutical
industries. Room Temperature Vulcanization (RTV) grades are also available, usually for
prototypes or small batch quantities.

79
12) FLUOROELASTOMER RUBBER
Fluoro elastomers or Fluorocarbons, widely known as Viton®, are among the most suitable
rubbers for continuous use at temperatures of 200°C and up to 300°C for short periods.
Various grades are available depending upon whether compression set, flexibility (as in
diaphragms) or chemical resistance is the prime concern. Fluoro elastomers have excellent
resistance to ozone and weathering, oils and most chemicals.
They are, however, very expensive, unsuitable for use with phosphate esters and ketones
and have poor low temperature capabilities.
Typical applications include accumulator bladders, diaphragms, gaskets, O-rings and seals
operating in especially harsh environments.
Viton® is a registered trade mark of DuPont Performance Elastomers.
12) PERFLUOROELASTOMER RUBBER
Per fluoro elastomers (FFKM) rubbers fill an important niche for applications involving
aggressive chemicals at temperatures up to 300°C.
They are extremely expensive and have poor physical properties and limited use at low
temperatures.
Typical applications include accumulator bladders, core sleeves, gaskets, O-rings and seals
working in extremely harsh environments, particularly within the oil and gas industries.

80
12) AFLAS®
Aflas® or TFE/P is a member of a new generation of fluoro-elastomers compounded
especially to provide unique properties for specific applications. The primary uses for Aflas
are in parts for oil drilling equipment. Aflas can be cross linked (cured) using a variety of
systems, but generally peroxides are used to provide the best all around environmental
resistance. A unique property of TFE/P is, that at very low temperatures (down to -54 °C) it
takes on leathery consistency and remains functional, unlike many other rubbers which can
often become brittle and shatter at low temperatures.
13) EPICHLOROHYDRIN RUBBER
Epi chlorohydrin (ECO) has properties similar to nitrile rubber but with better heat, oil and
petrol resistance. It has a low gas permeability and better low temperature flexibility than
NBR. Its resistance to acids, alkalis and ozone is excellent.
However, its poor compression set limits its use as a sealing material and its corrosive effect
on metals can increase tooling costs and limit metal bonding applications.
Typical uses are in automotive fuel systems, bladders, diaphragms and rollers.

81
14) POLYURETHANE
Polyurethanes fall into two main classes; polyester (AU) and polyether (EU). These materials
have outstanding tensile strength and abrasion resistance. They also have good resistance to
oxidation, ozone and petroleum based fuels and oils. Polyesters have physical properties
slightly superior to those of poly-ethers. Electrical properties are fairly good.
Unlike poly-ethers, polyesters can be affected by hot water and high humidity and their
resistance to acids and alkalis is low. Maximum operating temperatures should not significantly
exceed ambient. Compression set and creep properties are only fair. In view of the high
hysteresis (damping) of most polyurethanes, care must be taken for applications involving high
frequency deformation and tyre/wheel speeds of over 8 mph.
As these materials are liquid cast, tooling prices tend to be lower than for heat and pressure
molded rubbers.
Typical applications include abrasion-resistant coatings and linings, diaphragms, gaskets, haul-
off pads, hoses, seals and tyres/wheels.

Lubricants – Properties and Uses
82
Friction - is created when there is relative motion between two surfaces
Resistance to motion is defined as friction.
Lubrication is use of a material between surfaces to reduce friction
Any material used is called a lubricant.
Methods of lubrication: 2 Types
1) Hydrodynamic lubrication
Also called complete or full flow.
Occurs when two surfaces are completed separated by a fluid film
2) Boundary lubrication
Occurs when Hydrodynamic lubrication fails.
By adsorption or chemical reaction

83
Types of Lubricant – Physical:
Liquid: Typical lubricants are liquid/fluids; Mineral oil or synthetic oils
Solid: Graphite, MoS2
Semi solid: Greases
Gases: Atomized 2 stroke oils
Typical lubricants – Application:
Engine oils
Gear Oils
Turbine Oils
Hydraulic Oils
Metal working oils: Cutting oils, Forming Oils
Rust preventives
Heat Transfer Oils
Heat Treatment Oils: Quenching Oils, Tempering Oils
Refrigeration Oils
Rubber Process Oils
Ink process Oils

84
Lubricant – Components:
Base Oils: Mineral by-products of crude oil refining process.
Base oils are polymerized or synthesized further and called synthetic.
Additives: Natural, Synthetic
Function of a lubricant:
• Lubricate - Reduce friction
• Cooling - Heat transfer
• Cleaning - Detergency
• Noise pollution - dampening
• Sealing – prevent leakage
• Protection – prevent wear

85
Lubricate - Reduce friction
• The effects of friction: Metal to metal contact, Leads to wear and tear, Generates heat,
Results in Power loss
• Lubricant reduces friction by forming a film
• Reduces ill effect of friction
Cooling - Heat transfer
• When fuel is burnt in an engine
33% is useful power
33% removed by cooling water
33% by lube oil and radiation
• Lube oil removes heat from all areas and brings it to the engine sump.
• Improper cooling can lead to over heating, lead to wear, distortion and failure.
• Protection against acids and moisture
• Very important to increase life of component and equipment
Protection: Wear Prevention

86
Cleaning - Detergency
• Cleans carbon and varnish deposits
• Flushes the entire system removing
Soot
Deposits
Acids
Wear products
Moisture
• Removes external contaminants dust, moisture (external)
Reduce noise: By preventing metal to metal contact
Dampens noise: As between camshaft and tappet
Noise Reduction
Sealing
Oil film -
Between piston ring and liner
Helps in creating a gas tight seal

87
Properties of lubricants
1) Kinematic viscosity
• Measure of internal resistance to flow
• “Thickness” of fluid (in laymen terms)
• Decreases with increase in temperature
• Important in lubricant selection
• Increase in used oil indicates oxidation
• Specified at 40˚C and 100˚C
• Measured in Centi Stokes (CSt)
Low Viscosity oils used: High speeds, Low pressure, Low temperature
High Viscosity oils used: Low speeds, High pressure, High temperature

88
2) Viscosity index:
• Measure of fluids change of viscosity with temperature.
• Empirical number
• Higher the VI lower will be the change of viscosity with temperature
• Indicator of temperature range of operations
3) Pour Point:
• Lowest temperature at which the fluid will flow
• Indicates lowest operating temperature
• Measured in ˚C

89
5) Total Base Number (TBN)
• Measured the acid neutralizing reserve in oil.
• Important for deciding discard of oil
• Decreases due to - Oxidation of oil, Water contamination, Fuel contamination
• Measured in Mg KOH/gm of oil
4) Flash Point:
• Lowest temperature at which the vapor above the liquid will ignite under flame
• Indicated safe maximum temperature of operation.
• Indicator of volatility
• Test method – COC(Cleveland Open Cup) and PMCC(Pensky Martens Closed
Cup)
• Measured in ˚C

Composites
90
Composites are combination of two or more individual materials
Design goal: obtain a more desirable combination of properties (principle of combined action)
e.g., low density and high strength

Composites
91
Composite:
-- Multiphase material that is artificially made.
Phase types:
-- Matrix - is continuous
-- Dispersed - is discontinuous and surrounded by matrix
• Matrix phase:
-- Purposes are to:
- transfer stress to dispersed phase
- protect dispersed phase from environment
-- Types: MMC, CMC, PMC
metal ceramic polymer
• Dispersed phase:
-- Purpose:
MMC: increase sy, TS, creep resist.
CMC: increase KIc
PMC: increase E, sy, TS, creep resist.
-- Types: particle, fiber, structural

Composites
92
• Examples:
Adapted from Fig.
10.19, Callister &
Rethwisch 8e. (Fig.
10.19 is copyright
United States Steel
Corporation, 1971.)
- Spheroidite
steel
matrix:
ferrite (a)
(ductile)
particles:
cementite
(Fe
3
C)
(brittle)
60mm
Adapted from Fig. 16.4,
Callister & Rethwisch
8e. (Fig. 16.4 is
courtesy Carboloy
Systems, Department,
General Electric
Company.)
- WC/Co matrix:
cobalt
(ductile,
tough)
particles:
WC
(brittle,
hard)
:
600mm
Adapted from Fig. 16.5,
Callister & Rethwisch
8e. (Fig. 16.5 is
courtesy Goodyear Tire
and Rubber Company.)
- Automobile
tire rubber
matrix:
rubber
(compliant)
particles:
carbon
black
(stiff)
0.75mm
Particle-reinforced

Composites
93
• Elastic modulus, Ec, of composites:
-- two “rule of mixture” extremes:
Data:
Cu matrix
w/tungsten
particles
0 20 40 60 80 100
150
200
250
300
350
vol% tungsten
E(GPa)
(Cu) (W)
lower limit:
1
Ec
=
Vm
Em
+
Vp
Ep
upper limit: c m m
E = V E + VpEp
Particle-reinforced
• Application to other properties:
-- Electrical conductivity, se: Replace E’s in equations with se’s.
-- Thermal conductivity, k: Replace E’s in equations with k’s.

Composites
94
• Fibers very strong in tension
– Provide significant strength improvement to the composite
– Ex: fiber-glass - continuous glass filaments in a polymer matrix
• Glass fibers - strength and stiffness
• Polymer matrix - holds fibers in place, protects fiber surfaces, transfers
load to fibers
Fiber-reinforced
• Fiber Types
– Whiskers - thin single crystals - large length to diameter ratios
• graphite, silicon nitride, silicon carbide
• high crystal perfection – extremely strong, strongest known
• very expensive and difficult to disperse
– Fibers
• polycrystalline or amorphous
• generally polymers or ceramics
• Ex: alumina, aramid, E-glass, boron, UHMWPE
– Wires
• metals – steel, molybdenum, tungsten

Composites
95
aligned
continuous
aligned random
discontinuous

Composites
96
• Critical fiber length for effective stiffening & strengthening:
• Ex: For fiberglass, common fiber length > 15 mm needed
c
f d



2
length
fiber
fiber diameter
shear strength of
fiber-matrix interface
fiber ultimate tensile strength
• For longer fibers, stress transference from matrix is more efficient
Short, thick fibers:
c
f d



2
length
fiber
Long, thin fibers:
Low fiber efficiency
c
f d



2
length
fiber
High fiber efficiency

Composites
97
Continuous fibers - Estimate fiber-reinforced composite modulus of
elasticity for continuous fibers
 Longitudinal deformation
c = mVm + fVf and c = m = f
volume fraction iso-strain
 Ecl = EmVm + Ef Vf Ecl = longitudinal modulus
c = composite
f = fiber
m = matrix

Composites
98
Composite Stiffness: Transverse Loading
 In transverse loading the fibers carry less of the load
c= mVm + fVf and c = m = f = 
f
f
m
m
ct E
V
E
V
E


1
Ect = transverse modulus

c = composite
f = fiber
m = matrix
isostress

Ect 
EmEf
VmEf Vf Em


Composites
99
Composite Production Methods (i)
Pultrusion
 Continuous fibers pulled through resin tank to impregnate fibers with
thermosetting resin
 Impregnated fibers pass through steel die that preforms to the desired shape
 Preformed stock passes through a curing die that is
 precision machined to impart final shape
 heated to initiate curing of the resin matrix
Fig. 16.13, Callister & Rethwisch 8e.

Composites
100
Composite Production Methods (ii)
 Filament Winding
 Continuous reinforcing fibers are accurately positioned in a
predetermined pattern to form a hollow (usually cylindrical) shape
 Fibers are fed through a resin bath to impregnate with thermosetting resin
 Impregnated fibers are continuously wound (typically automatically) onto
a mandrel
 After appropriate number of layers added, curing is carried out either in
an oven or at room temperature
 The mandrel is removed to give the final product

Composites
101
• Laminates -
-- stacked and bonded fiber-reinforced sheets
- stacking sequence: e.g., 0º/90º
- benefit: balanced in-plane stiffness
• Sandwich panels
-- honeycomb core between two facing sheets
- benefits: low density, large bending stiffness
honeycomb
adhesive layer
face sheet
Structural Composite

Materials in Hostile Environment
102
Sydney H Avner : Chapter – 13
Assignment:
1) Effects of High Temperature on Materials
2) Effects of Sub normal Temperature on Materials
3) Effect of Corrosion on Materials

103
SUMMARY
 Phase Diagram – Sydney H Avner (Ch -7)
 Hardness – Sydney H Avner (Ch -1)
 Cast Iron – Sydney H Avner (Ch -11)
 Materials in Hostile Environment - Sydney H Avner (Ch -13)
Practice Mathematical problems of Phase Diagrams from William D. Callister, Jr. (Materials Science and
Engineering: An Introduction)
 Plastic - Lecture
 Rubber – Lecture
 Lubricants - Lecture
 Composites – Lecture + William D. Callister, Jr. – (Ch – 16)
 Ceramic – Lecture + William D. Callister, Jr. – (Ch – 12,13)
 Glasses – Thermal, Electrical, Optical, Electrical, Mechanical Properties, Production Process

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