Fundamentals of metal and steel,
heat treatment and material
strengthening
Metallurgy & Metallurgists
• Dictionary
– Metallurgy = the science that explains methods of
refining & extracting metals from their ores & preparing
them
• Materials Today Magazine
– Metallurgy = the science that explains the properties,
behavior & internal structure of metals.
• Metallurgies
– Scientists in metallurgy that probe deeply inside the
internal structure of metal to learn what it looks like.
Terms to know !!!
 Elements = is a pure substance made up of just one kind of
materials
 Metal = is an element that has metallic properties, i.e. heat &
electrical conductor
 Compound = is a material that is composed of two or more
elements that are chemically joined
 Mixture = is a materials composed of 2 or more elements or
compounds mixed together, but not chemically joined
 Solution = is a special kind of mixture. When 2 materials
combine & become a solution, one of two will become the
“dictator” & the other one will become quiet & submissive.
 Solid solution = is a solution in which both solvent & solute are
solids. Both the “dictator” & the dissolved material are solids
Alloy
• Alloy = When 2 or more metals are
dissolved together in a solid solution
– Steel = alloy of Fe & C
– Bronze = alloy of Cu & Sn
– Brass + alloy of Cu & Zn
Taxonomy of Metals
Types of metal alloys
• Groups of metal alloys:
– Ferrous alloy (iron is the prime constituent).
– Nonferrous alloys.
• Steels: Iron-carbon alloys that may contain
appreciable concentrations of other alloying
elements. Carbon content is normally less than
1.0 wt%.
• Cast irons: Ferrous alloys with carbon contents
above 2.14 wt% (usually 3.0-4.5 wt% C).
Classification for various ferrous alloys
METAL ALLOYS
Non-ferrous
Ferrous
Gray
iron
Low alloy
Low carbon Medium carbon
Plain
High
strength,
low alloy
White
iron
Ductile
Malleable
iron
(nodular) iron
Tool
Plain
Special
alloy cast
iron
High alloy
High carbon
Heat
treatable
Plain
Wrought iron
Cast iron
Steels
Tool
Stainless
STEELS

Steel is an alloy or solid solution, dictator = Iron,
dissolved mater. = C

Most widely used materials in the world

High strength, machined & formed easily

Steel are iron-carbon alloys that may contain
appreciable concentrations of other alloying elements

Mechanical sensitive to the content of C < 1.0 wt.%

Thousands of alloys that have different compositions
and/ or heat treatments.
STEELS

Commonly classified according to C concentration
a) Low CS
b) Medium CS
c) High CS

Subclasses; according to the concentration of other
allying elements
a) Plain CS

contain only residua; concentrations of impurities other
than C & a little Mn
b) Alloy steels

alloying elements are added in specific concentration
Steels
Composition of Steels
 Steel is a mater. Composed primary of iron.
> 90% iron, many steels contain > 99% iron
 All steel contain 2nd element = C
% C range just above 0% ~ approx. 2.0%,
many steels contain 0.15 ~ 1.0%.
Effect of C in steel
 Steel with the least C are more flexible & ductile,
not strong.
 C content increases, so do strength, hardness &
brittleness
 In making steel, the iron dissolves the C, when
there is too much carbon for the iron to “digest”
the alloy is no longer called steel.
Effect of C in steel: Microstructure
In steel, iron dissolves the C
In gray cast iron, the C
precipitates out as C flakes
In ductile cast iron, the C
precipitates out as a small round
nodules
Classification of
Steel
• 4 numbers/ digits
• 1st 2 digits refer to the
alloy content
• Eg;
– 5147 steel, ’51’ = steel
has a lot of Cr
– 2517 steel, ’25’ =
amount of Ni
– 1040 steel, ’10’ = very
little alloy content
except C
Steel Numerical
Name
10XX
11XX
13XX
23XX
25XX
31XX
33XX
303XX
40XX
41XX
43XX
44XX
46XX
47XX
48XX
50XX
51XX
501XXX
515XX
521XX
514XX
515XX
61XX
81XX
86XX
87XX
88XX
92XX
93XX
94XX
98XX
XXBXX
XXLXX
Key Alloys
C only
C only (free cutting)
Mn
Ni
Ni
Ni-Cr
Ni-Cr
Ni-Cr
Mo
Cr-Mo
Ni-Cr-Mo
Mn-Mo
Ni-Mo
Ni-Cr-Mo
Ni-Mo
Cr
Cr
Cr
Cr
Cr
Cr
Cr
Cr-V
Ni-Cr-Mo
Ni-Cr-Mo
Ni-Cr-Mo
Ni-Cr-Mo
Si-Mn
Ni-Cr-Mo
Ni-Cr-Mo-Mn
Ni-Cr-Mo
B
Pb
Steel Numbering System
• Last 2 (or 3 in 5 digits
case) digits refer to %
of C in steel.
• Eg;
– 1040 steel, ’40’ =
0.40% C
Steel
Name
Appox % C
Alloys
present in
Larger
amount than
normal case
1020
0.20
Only C
1118
0.18
Only C
1340
0.40
Mn
2340
0.40
Ni
3140
0.40
Ni & Cr
4024
0.24
Mo
4320
0.20
Ni, Cr & Mo
5135
0.35
Cr
6150
0.50
Cr & V
8622
0. 22
Ni, Cr & Mo
9255
0.55
Si & Mn
Effect of Alloys
• Greater strength – C, Mn
& Ni added
• Corrosion Resistance –
Cr or Cu added
• Better machinability – Pb
& S added
• Physical properties at
high temp. – W or Mo are
recommended
Steel Alloy
C
Effect on Steel
Hardness-strength-wear
Cr
Corrosion resistanceHardenability
Machinabiliy
Pb
Al
Strength – Hardenability
– More response To Heat
Treat
Deoxidation
Ni
Toughness – strength
Si
Deoxidation –
Hardenability
High temp. strength –
wear
High temp. strength –
Hardenability
Machinabiliy
Mn
W
Mo
S
Ti
V
Elimination of C
precipitation
Fine grain – Toughness
B
Hardenability
Cu
P
Corrosion resistance –
strength
Elimination of C
precipitation
Strengt
Tellurium
Machinability
Co
Hardness-wear
Columbium
STEELS
Low
alloy
High
alloy
Less expensive
More expensive
Less alloy
content
More alloy content
Few special
properties
Special properties
Overview
Low alloy steel
Low carbon
steel
• 0.05 ~ 0.35% C
• Comparatively
Medium carbon
steel
less
strength
• Comparatively
less
Hardness
• Easy
Machining
Forming
&
• Least Expensive
• Largest
quantity
Produced
• 0.35 ~ 0. 50% C
• Hard & strong
High carbon
steel
after
heat treating
• More
expensive than
Low CS
• 0. 50 ~ 1.0% C
• High strength
&
hardness
• Hard
& strong after
heat treating
• More
expensive than
Low & medium CS
Application of Low Alloy Steel
Low alloy steel
Low carbon
steel
Medium carbon
steel
High carbon
steel
• Fence wire
• Wheels
• Tools
• Auto bodies
• Axles
• Dies
• Galvanized sheets
• Crankshafts
• Knives
• Storage tanks
• Gear
• Railroad wheels
• Large pipe
• Various parts in
building, bridges &
ships
• High strength
materials application
High alloy steel
Tool steel
Is a grade of steel which one or more
alloying elements have been added in larger
amounts to give it special properties that
ordinary cannot obtained with CS
Stainless steel
Widely used
Used as cutting tools, mould & dies
Extremely good corrosion
resistance
Machine parts
Expensive than CS
Category
Description
W
Water Hardening
O
Oil Hardening
A
Air Hardening
D
Oil or air Hardening
S
Shock resistance
H
Hot working
M
High speed (Mo)
T
High speed (W)
L
Special purpose
F
Special purpose
P
Mold making
Harder to cut & machine
High Cr and/or Ni
High Alloy Steel
Stainless steel
Ferritic
Martensitic
Tool Steel
Austenitic
Precipitation
hardening
Stainless Steel
 Excellent corrosion resistance in many environment
due to Cr content (>11~ 12% Cr)
 Corrosion resistance enhanced by Ni & Mo
 Cr forms a surface oxide that protects the underlying
Fe-Cr alloy from corroding. To produce the protective
oxide, the SS must be exposed to oxidizing agents
 SS are divided into 3 classes based on the
microstructure phase constituent
a) Ferritic
b) Martensitic
c) Austenitic
Ferritic Stainless Steel
•
FSS are essentially Fe-Cr binary alloy containing about 12 ~ 30% Cr
•
Called ferritic bcause their structure remains mostly ferritic (BCC, α iron
type) at normal heat treatment conditions.
•
Relatively low cost
•
Mainly used as general construction materials
•
The present of the carbides in this steel reduces its corrosion resistance to
some extent
•
Considered non-heat-treatable because they are all single phase, α iron
type alloys whose crystal structure does not change under normal heattreatment conditions.
•
Eg;
– 430 SS (general-purpose, non-hardenable uses, range hood, restaurant
equipment)
– 446 SS (High-temp. application, heater, combustion chambers)
Type 430 (ferritic) SS strip annealed at 788oC.
The structure consists of a ferrite matrix equiaxed grain
& dispersed carbide particles.
Martensitic Stainless Steel
•
MSS are essentially Fe-Cr alloys containing 12 ~ 17 % Cr with sufficient C (0.15 ~
1.0 %).
•
Produced from quenching from the austenitic phase region
•
Called martensitic because they are capable of developing a martensitic structure
from austenitic condition by quenching heat treatment.
•
Can be adjusted to optimize strength & hardness but corrosion resistance is
relatively poor compared to the ferritic & austenitic steel
•
High hardness due to hard martensitic matrix & the presence of a large
concentration of primary carbides.
•
Considered as heat-treatable because the carbon content is sufficient for the
formation of a martensitic structure by austenitizing and quenching processes.
•
E.g.;
– 410 SS ( General purpose, heat-treatable machine parts, pump shafts, valves)
– 440A SS (Cultery, bearing, surgical tools)
– 440C SS (Balls bearing, valve parts)
Type 440 (martensitic) SS hardened by autenitizing at
1010oC & air cooled. Structure consists of primary
carbides in martensite matrix.
Austenitic Stainless Steel
 Austenitic steel are essentially Fe-Cr-Ni ternary alloys containing
about 16~25% Cr & 7~20% Ni.
 Called austenitic since their structure remains austenitic (FCC, γ iron
type) at all normal heat-treating temperatures.
 Better corrosion resistance than ferritic & martensitic SS because
the carbides can be retained in solid solution by rapid cooling.
 E.g.;
– 301 SS (High work hardening rate alloy, structural applications)
– 304 SS (Chemical & food processing equipment)
– 304L SS (Low carbon for welding, chemical tank)
– 321 SS (Stabilized for welding, process equipment, pressure
vessels)
– 347 SS (Stabilized for welding, tank cars for chemicals)
Type 340 (austenitic) SS hardened strip annealed 5
min at 1065oC and air cooled. Structure consists of
equiaxed austenite grains.
Example
1.
2.
3.
4.
What are the 3 basic types of stainless steels?
What is the basic composition of ferritic stainless
steels & Why are ferritic stainless steels considered
non-heat-treatable?
What is the basic composition of martensitic stainless
steels and why are these steels heattreatable?
What are some applications for ferritic and martensitic
stainless steels?
Solution;
Refer your lecture note
Example
What makes it possible for an austenitic stainless steel to have an
austenitic structure at room temperature?
Solution;
Austenitic stainless steel can retain its FCC structure at room
temperature due to the presence of nickel, at 7 to 20 weight percent,
which stabilizes the austenitic Fe structure.
What makes austenitic stainless steels that are cooled slowly through
the 870 to 600ºC range become susceptible to intergranular corrosion?
Solution;
When slowly cooled through 870 to 600ºC, some austenitic stainless
steels become susceptible to intergranular corrosion because
chromium-containing carbides precipitate at the grain boundaries.
CAST IRON
Special alloy
cast iron
Gray iron
more common
Ductile
White iron
(nodular) iron
most brittle
Higher quality
Malleable iron
Higher quality
Special properties
Cast Irons
 Iron-Carbon alloys of 2.0 ~
6.0%C
 Typical composition: 2.04.0%C,0.5-3.0% Si, less
than 1.0% Mn and less
than 0.2% S.
 Si-substitutes partially for C
and promotes formation of
graphite as the carbon rich
component instead Fe3C.
Example
What are the cast irons? What is their basic range of
composition?
Solution:
Cast irons are a family of ferrous alloys intended to be cast into a
desired shape rather than worked in the solid state.
These alloys typically contain 2 to 4 percent C and 1 to 3
percent Si.
Additional alloying elements may also be present to control or
vary specific properties.
Example
What are some of the properties of cast irons that make
them important engineering materials? What are some of
their applications?
Cast irons are easily melted and highly fluid and do not form undesirable
surface films or shrink excessively; consequently, they make excellent casting
irons.
They also possess a wide range of strength and hardness values and can be
alloyed to produce superior wear, abrasion, and wear resistance. In general,
they are easy to machine.
Their applications include engine cylinder blocks and gear boxes, connecting
rods, valve and pump casings, gears, rollers, and pinions.
Gray Cast Iron
• Fe-C-Si alloys
• Composes of: 2.5-4.0%C, 1.03.0%Si and 0.4-1.0% Mn.
• Gray cast iron contain large
amount of C in the form of
graphite flakes.
• Microstructure: 3-D graphite
flakes formed during eutectic
reaction. They have pointed
edges to act as voids and crack
initiation sites.
Gray Cast Iron
• Properties:
– Hard & brittle
– Relatively poor TS because graphite flakes in the structure
– excellent compressive strength,
– excellent machinability,
– good resistance to adhesive wear (self lubrication due to
graphite flakes),
– outstanding damping capacity ( graphite flakes absorb
transmitted energy),
– good corrosion resistance and it has good fluidity needed for
casting operations.
– Easy to cast
• It is widely used, especially for large equipment parts subjected to
compressive loads and vibrations.
– Eg; brake disc, cylinder blocks, cylinder heads, clutch plates,
heavy gear boxes and diesel engine castings
White Cast Iron
• Fe-C-Si alloys
• Composes of: 1.8-3.6%C, 0.5-1.9%Si
and 0.25-0.8%Mn.
• White cast iron contain large amount of
iron carbide that make them hard & brittle
• All of its C is in the form of iron-carbide
(Fe3C). It is called white because of
distinctive white fracture surface.
• It is very hard and brittle (a lot of Fe3C).
More brittle difficult to machine
• It is used where a high wear resistance is
dominant requirement (coupled hard
martensite matrix and iron-carbide).
– Eg; iron mills, stone breaker
Malleable Cast Iron
•
Fe-C-Si alloys
•
2.0 ~ 2.6% C, 1.1 ~ 1.6% Si
•
Malleable cast irons are 1st cast as white cast
iron & then are heat-treated at about 940oC &
held about 3~20 hrs.
•
The iron carbide in the white iron is
decomposed into irregularly shaped nodules
or graphite.
•
•
Less voids and notches.
Ferritic MCI:
–
–
–
–
–
–
Ductile, 10% EL,
High TS, 35 ksi yield strength,
50 ksi tensile strength.
Excellent impact strength,
good corrosion resistance
good machinability.
Malleable Cast Iron
• Ductile iron with ferrite matrix (top)
and pearlite matrix (bottom) at
500X.
• Spheroidal shape of the graphite
nodule is achieved in each case.
• Advantageous properties of
malleable cast irons are toughness,
moderate strength, uniformity of
structure and ease of machining and
casting.
Pearlitic Malleable Cast Iron
• Pearlitic MCI: by rapid cooling through eutectic
transformation of austenite to pearlite or martensite
matrix.
• Composition: 1-4% EL, 45-85 ksi yield strength, 65-105
ksi tensile strength. Not as machinable as ferritic
malleable cast iron.
Ductile Cast Iron
• Fe-C-Si alloy
• 3.0 ~ 4.0% C, 1.8 ~ 2.8% Si.
• Ductile cast iron contain large
amount of C in the form of
graphite nodules (spheres).
• Without a heat treatment by
addition of ferrosilicon
(MgFeSi) formation of smooth
spheres (nodules) of graphite
is promoted.
• Properties: 2-18% EL, 40-90
ksi yield strength, 60-120 ksi
tensile strength.
Ductile Cast Iron
• Attractive engineering material due to:
good ductility, high strength, toughness,
wear resistance, machinability and low
melting point castability.
• Applications for ductile cast irons include
valve and pump casings, crankshafts,
gears, rollers, pinions and slides.
Example
Why are ductile cast irons in general more ductile than gray
cast irons?
Solution
Ductile cast irons are, in general, more ductile than gray
cast irons because their spherical graphite nodules are
surrounded by relatively ductile matrix regions which allow
significant deformation without fracture.
In contrast, the gray cast irons consist of an interlacing
network of graphite flakes which can be fractured easily.
Example
Why does the graphite form spherical nodules in ductile
cast irons instead of graphite flakes as in gray cast irons?
Solution;
Graphite forms spherical nodules in ductile cast irons
because the levels of phosphorus and sulfur are reduced
significantly compared to those in gray cast irons; these
two alloying elements prevent the formation of nodules and
thus promote the formation of graphite flakes
Special alloy cast iron
 Contain High % of Ni, Cu, Cr & other alloys
 Ni, Cu & Cr good corrosion & chemical resistance to
acids.
 Greater strength & better high temperature properties
 Used in cylinders, pistons, piston rings & turbine stator
vanes
Example
How Steel & Cast Iron Differ ?
Steel
Cast Iron
Iron with C still in solution
Iron which some of the C has
precipitate out & appears as
flakes
C content; 1.6 ~ 2.0%
C content; 2.0 ~ 6.0%C
Ductile compare to C. iron
Brittle compare to steel
High strength
Poor Strength
Hard to machine
Easy to machine
Hard to control casting
Easy to cast
Low damping capacity
Good Damping Capacity
Wrought Iron
 Very different from cast iron
 Almost pure iron, little C
content
 Low strength & hardness
 Good corrosion resistance
 Many fibrous stringers of slag
are distributed throughout
wrought iron
Elements
Wt.%
Fe
balance
C
0.06 ~ 0.08
Si
0.10 ~ 0.16
Mn
0.02 ~ 0.05
S
0.01
P
0.06 ~ 0.07
Nonferrous alloys
• Cu Alloys
• Al Alloys
Brass: Zn is subst. impurity -lower : 2.7g/cm 3
(costume jewelry, coins,
-Cu, Mg, Si, Mn, Zn additions
corrosion resistant)
-solid sol. or precip.
Bronze: Sn, Al, Si, Ni are
strengthened (struct.
subst. impurity
aircraft parts
(bushings, landing
& packaging)
gear)
• Mg Alloys
NonFerrous
Cu-Be:
-very low : 1.7g/cm 3
Alloys
precip. hardened
-ignites easily
for strength
-aircraft, missles
• Ti Alloys
-lower : 4.5g/cm 3
• Refractory metals
-high melting T
-Nb, Mo, W, Ta
vs 7.9 for steel
• Noble metals
-reactive at high T -Ag, Au, Pt
-oxid./corr. resistant
-space applic.
Cu & its alloys
 Unalloyed Cu is so soft & ductile; difficult to machine
 Highly resistant to corrosion
 Unalloyed Cu cannot be hardened or by strengthened by
heat heat-treating procedures
 Mechanical & corrosion properties can be improved by
alloying
 Cold working and/or solid-solution alloying must be utilized
to improved the mechanical properties
 Cu alloys, e.g.; Brass, Bronze, Beryllium Cu, Cartridge
brass, Cu-Ni alloy, Tin bronze, Al bronze
 Application; Electrical wire, nails, valves, automotive
radiator, condenser, heat exchanger components, pistons
rings, bearing, gears & so on
Example
What are some of the important properties of unalloyed
copper that make it an important industrial metal?
Solution:
Properties of unalloyed copper, which are important to
industrial applications, include high thermal and electrical
conductivity, good corrosion resistance, ease of fabrication,
medium tensile strength, controllable annealing properties,
and general soldering and joining characteristics.
Al & its alloys

Unalloyed Al; low density (2.7 gcm-3), lightweight, high
electrical & conductivity, workability, ductile & low cost.
Moderate melting point (660oC)

Resistance to corrosion in most natural environments due to
formation oxide film that form on its surface.

Non-toxic, used food container & packaging

Mechanical properties can enhanced by cold work & alloying

Alloying elements; Cu, Mg, Si, Mn & Zn

Al alloy are classified as either cast or wrought
Al & its alloys

Chemical composition is designated by 4-digit number indicates
the principle impurities & in some cases, the purity level

Application of Al alloys; aircraft structure parts, beverage cans,
Food/chemical handling, storage equipments, bus bodies,
automotive parts (engine blocks, pistons & intake manifolds).

To be used as eng. materials for transportation to reduce fuel
assumption because its specific strength, which is quantified by
the TS-specific gravity ratio. Its TS is inferior to a more dense
material (such as steel), on weight basis it will able to sustain a
larger load.

A new generation Al-Li alloys applied in aircraft & aerospace
industries has low densities (~ 2.5gcm-3), high specific moduli,
excellent fatigue, low temp. toughness.
Example
What are some of the properties that make aluminum an
extremely useful engineering material?
Solution:
Aluminum is an extremely useful engineering material due
to its low density (2.70 g/cm3), good corrosion resistance,
good strength when alloyed, high thermal & electrical
conductivities and low cost.
What are some of the properties that make aluminum to be
high prospect for transportation material.
Solution:
To be used as eng. materials for transportation to reduce
fuel assumption because its specific strength, which is
quantified by the TS-specific gravity ratio. Its TS is inferior
to a more dense material (such as steel), on weight basis it
will able to sustain a larger load.
Mg & its alloys

Lightweight metal, low density = 1.74gcm-3. Moderate melting point
(651oC).

Applications requiring a low density metal (aircraft, aerospace &
missile)

Soft, low elastic modulus.

Difficult to cast because molten state burn in air

Low strength, poor resistance to creep, fatigue & wear.

At RT, Mg & its alloy are difficult to deform.

Chemically unstable; susceptible to corrosion in marine environments.

Mg alloys are classified as either cast or wrought.

Alloying elements; Al, Zn, Mn & some rare earth elements.
Mg & its alloys

Mg alloys have replaced engineering plastic that
have comparable densities inasmuch as the Mg
materials are stiffer, more recyclable, & less costly
to produce.

Application of Mg alloys;



hand held devices (chain saws, power tools, hedge
clippers)
Automobile ( steering wheels & columns, seat frames,
transmission case)
Audio-video-computer-communications equipment (
laptop computers, camcorders, TV sets, cellular
telephones)
Example
What advantages do magnesium alloys have as
engineering materials?
Solution:
As engineering materials, the primary advantage of
magnesium alloys is their lightness; magnesium has the
low density value of 1.74 g/cm3.
What are some of the properties that make a Mg can be
replaces plastic as an engineering materials ?
Solution:
Mg alloys can replaces engineering plastic because it has a
comparable densities, stiffer, more recyclable, & less costly
to produce.
Ti & its alloys

Pure Ti; relatively light metal (density = 4.54 gcm-3), high melting point
(1668oC), high elastic modulus & high strength.

Ti alloys; extremely strong, high TS, spesific strength, highly ductile,
easily forged & machined.

Corrosion resistance to many chemical environments.

Limitation; chemical reactivity with other materials at elevated temp.

Expensive because it is difficult to extract to pure state from it
compound.

Combine to Al for aircraft structural parts application.

Application; airplane structures, jet engine, space vehicles, gas
turbine engine casings, jet engine components (compressor disks,
plates & hubs) surgical implants & petroleum & chemical industries.
Example
Why are titanium and its alloys of special engineering
importance for aerospace applications?
Solution:
Titanium and its alloys are of special engineering
importance for aerospace applications because of their
high strength-to-weight ratios.
Why is titanium metal so expensive?
Solution:
Titanium is very expensive because it is difficult to extract
in the pure state from its compounds.
Refractory Metals
• metals with exceptionally high melting points;
above 2450oC
Melting Point,
oC
Density, gcm-3
Cost
RM/ Ib
Niobium
(columbium) (Nb)
2468
8.57
192 ~ 210
Tantalum (Ta)
2996
16.6
780 ~ 840
Molybdenum (Mo)
2620
10.22
210 ~ 228
Tungsten
3380
19.3
450
Metal
Refractory Metals
Group in periodic Table
Group VB
Group VIB
Nb, Ta
Mo, W
Tensile strength at elevated
temperature
Low
Low
Elastic moduli
Less
High
Solid solubility for interstitial
elements (C,O,H,N)
High
Less
Electronic Configuration
Less
Stable
Creep Strength
Less
High
Metal Elements
Ductile-to-brittle fraction
Below room
transition-temperature behaviour
temp
(DBTT)
(easy fabricate)
Near OR above
room temp
Refractory Metals
Example
Define a refractory metals. Name the metal elements that
are considered to be refractory elements?
Solution:
Refractory metals are metals with exceptionally high
melting points; above 2450oC.
Refractory elements
i) Niobium (Nb)
ii) Tantalum (Ta)
iii) Molybdenum (Mo)
iv) Tungsten (W)
Superalloys
 Superalloys have superlative combinations of properties.
 Most are used in aircraft turbine components
 Must withstand exposure to severely oxidizing
environments & high temperature
 These materials are classified according to the
predominantly metal in alloys;- Co, Ni or Fe.
 Other alloying elements; refractory metals (Nb, Mo, W &
Ta), Cr & Ti.
 Other application; nuclear reactors & petrochemical
equipment.
Noble metals
 The noble metals are a group of 8 elements that have
some physical characteristics in common.
 Expensive & superior or notable (noble) in properties.
 Examples; Silver (Ag), gold (Au), Platinum (Pt),
Palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium
(Ir) & osmium (Os).
 Ag, Au & Pt are used as jewelry
 Alloys of Ag & Au employed as dental restoration
materials & IC electrical contacts.
 Pt used for laboratory equipment, catalyst &
thermocouples.
Miscellaneous nonferrous alloys
Nickel & its alloys (eg. Monel) – highly corrosion
resistance.
 Used in pumps, valves and other components that
are in contact with some acid & petroleum solutions.
Lead (Pb) & Tin (Sn) and its alloys –
mechanically soft & weak.
 Low melting temperature, quite resistance to many
corrosion environment.
 Many common solders are lead-tin alloys,
 Application of lead alloys – x-ray shields & storage
batteries
 Application of tin alloys – thin coating on the inside of
plain CS cans (tin cans) used for food containers.
Miscellaneous nonferrous alloys
Zn – soft & low melting temperature, reactive
with several materials, susceptible to corrosion
 Zn applications;- thin coating on CS roofing
 Zn alloys applications;- padlocks, plumbing fixtures,
automotive parts (door handles & grilles) & office
equipments.
Zirconium & its alloys are ductile, resistance to
corrosion in superheated water, transparent to
thermal neutrons
 Application of Zr alloys – Cladding for uranium fuel in
water-cooled nuclear reactors.
 Heat exchangers, reactor vessels & piping systems
for the chemical-processing & nuclear industries.