ENGINEERING MATERIALS NICKEL AND ITS ALLOYS TITANIUM AND ITS ALLOYS
Jan 12, 2015
ENGINEERING MATERIALS
NICKEL AND ITS ALLOYS TITANIUM AND ITS ALLOYS
NICKEL
PHYSICAL PROPERTIES
SILVERY WHITE METAL HARD AND DUCTILE MAGNETIC UPTO 355 DEGREE CELSIUS FCC WITH LATTICE PARAMETER OF 0.352 NM
AND ATOMIC RADIUS OF 0.124 NM MELTING PT. = 1728K HEAT OF FUSION = 17.48 KJ/MOLE
MECHANICAL PROPERTIES
THERMAL CONDUCTIVITY = 90.9 W/M/K YOUNG'S MODULUS = 200 GPa SHEAR MODULUS = 76 GPa BULK MODULUS = 180 GPa POISSON'S RATIO = 0.31
OCCURENCE
LATERITE ORES : (Fe, Ni)O(OH) GARNIERITE ORES : (a hydrous nickel silicate): (Ni,
Mg)3Si2O5(OH)4
PENTLANDITE ORES : Ni, Fe)9S8
ABOUT 40% FROM RUSSIA AND 30% FROM CANADA
EXTRACTION AND PURIFICATION
Commercial extraction is from sulphide ores. Nickel is recovered through extractive metallurgy. Concentration is done by froth floatation Next stage is roasting and reduction of the sulphide ore
which yields 75% pure nickel Refining is done by “Monds Process” Nickel is reacted with carbon monoxide at around 50 °C to form volatile nickel carbonyl. Any impurities
remain solid while the nickel carbonyl gas passes into a large chamber at high temperatures in which tens of thousands of nickel spheres, called pellets, are constantly stirred. The nickel carbonyl decomposes, depositing pure nickel onto the nickel spheres. Alternatively, the nickel carbonyl may be decomposed in a smaller chamber at 230 °C to create fine nickel powder. The resultant carbon monoxide is re-circulated through the process. The highly pure nickel produced by this process is known as carbonyl nickel.
APPLICATIONS
Household : Magnets, Coins, Rechargeable cells, Electric guitar strings
Industrial : Alloys, Wires, electric gadgets.
Laboratory: Catalyst for hydrogenation
Biology : Present in enzymes
NICKEL ALLOYS
ALNICO
“ALNICO” = Al + Ni+ Co + Cu(traces) + Ti (traces) + Fe
It is ferromagnetic and used in permanent magnets
8–12% Al, 15–26% Ni, 5–24% Co6% Cu, up to 1% Ti and balance is Fe.
GERMAN SILVER
Cu + Ni + Zn 60% copper, 20%
nickel and 20% zinc. Applications : silver plated cutlery zippers & jewellery musical instruments pipe fittings
INCONEL Family of austenitic nickel -
chromium based superalloys
PROPERTIES:
Oxidation & corrosion resistent
High heat resistence
Difficult to machine
APPLICATIONS :
Gas turbine combustors and blades.
Shafts
Rocket skins.
MONEL METAL COMPOSITION : nickel (up to
67%) and copper, with some iron and other trace elements
PROPERTIES :
difficult to machine
highly corrosion resistent
highly sonorous
APPLICATIONS:
submerged pumpsets
musical instruments
oilfield industry
earth moving drills
lab apparatus
NICHROME 80% nickel and 20%
chromium PROPERTIES: high melting point
high electrical resistivity
good stability from deforming
APPLICATIONS: resistance heating coils
rocket igniters
jewellery casting supports
ceramic manufacturing industry
HASTELLOY
COMPOSITION : Nickel + molybdenum +
chromium
PROPERTIES : High wear resistence
high corrosion resistance
high stress service
TYPES : A,B,C,D & its variants
APPLICATIONS : Bearings, pressure vessel linings,
chemical reactor pipes....
MU-METAL 75% nickel, 15% iron, plus copper and
molybdenum
PROPERTIES :
very high magnetic permeability
low hysteresis loss.
more ductile and workable.
APPLICATION: Electric power
Hard Drives
Cathode-ray tubes
Magnetic phonograph cartridges
Magnetic resonance imaging
The magnetometers used in magnetoencephalography and magnetocardiography
Photomultiplier
Vacuum chambers
Superconducting
TITANIUM
PHYSICAL PROPERTIES
Low density high strength and ductility lustrous corrosion resistant and high melting point low thermal & electrical conductivity Paramagnetic
MECHANICAL PROPERTIES
Young's modulus =116 Gpa Shear modulus 44 Gpa Bulk modulus 110 Gpa Poisson ratio 0.32 Thermal conductivity = 21.9 W/m/K
OCCURENCE Titanium is always bonded to other
elements in nature
It is present in most igneous rocks and in sediments derived from them
living things and natural bodies of water
Titanium is contained in meteorites
found in coal ash
Major ores : anatase,brookite,ilmenite,rutile,titanite,perovs-kite and a few iron ores.
EXTRACTION AND PRODUCTION
4 MAJOR STEPS : - reduction of titanium ore into "sponge"
melting of sponge, or sponge plus a master alloy to form an ingot
primary fabrication, where an ingot is converted into general mill products such as billet, bar, plate, sheet, strip, and tube
secondary fabrication of finished shapes from mill products
KROLL'S PROCESS ( COMMERCIAL PROCESS) : -
2 FeTiO3 + 7 Cl2 + 6 C → 2 TiCl4 + 2 FeCl3 + 6 CSSO (900 °C)
TiCl4 + 2 Mg → 2 MgCl2 + Ti (1100 °C)
APPLICATIONS ALLOYING
PAINTS,PAPER,TOOTHPASTE,PLASTICS
CORROSION RESISTANT TOOLS
SURGICAL INSTRUMENTS
AIRCRAFT PARTS AND GEARS
MARINE VEHICLE PARTS
PLUMBING EQUIPENTS
TiCl4 IS USED TO PRODUCE MANY CATALYSTS.
SPORTS GOODS
DEGIGNER JEWELLERY
ORTHOPAEDIC IMPLANTS
TITANIUM ALLOYS
The crystal structure of titanium at ambient temperature and pressure is close-packed hexagonal α phase . At about 890°C, the titanium undergoes an allotropic transformation to a body-centred cubic β phase which remains stable to the melting temperature.
Some alloying elements raise the alpha-to-beta transition temperature (i.e. alpha stabilizers) while others lower the transition temperature (i.e. beta stabilizers).
Aluminium, gallium, germanium, carbon, oxygen and nitrogen are alpha stabilizers.
Molybdenum, vanadium, tantalum, niobium, manganese, iron,chromium, cobalt, nickel ,copper and silicon are beta stabilizers.
CATEGORIESAlpha alloys which contain neutral alloying elements (such as tin) and/ or alpha stabilisers (such as aluminium or oxygen) only. These are not heat treatable.
Near-alpha alloys contain small amount of ductile beta-phase. Besides alpha-phase stabilisers, near-alpha alloys are alloyed with 1-2% of beta phase stabilizers such as molybdenum, silicon or vanadium.
Alpha & Beta Alloys, which are metastable and generally include some combination of both alpha and beta stabilisers, and which can be heat treated.
Beta Alloys, which are metastable and which contain sufficient beta stabilisers (such as molybdenum, silicon and vanadium to allow them to maintain the beta phase when quenched, and which can also be solution treated and aged to improve strength.
GENERAL PROPERTIES OF TITANIUM ALLOYS
It is stronger than steel, but 45% lighter
It is not easily corroded
resistance to high temperatures
low thermal conductivity
low electrical conductivity
heat has no or negligible effect on dimension but it hardens on heating
higher resistance towards metal fatigue
no harm to biological tissues
ALLOY GRADES
BY VARYING THE TYPE AND COMPOSITION OF METALS ADDED, 38 DIFFERENT ALLOYS ARE USED FOR COMMERCIAL PURPOSES.
MAJOR ALLOYED METALS ARE ALUMINIUM, VANADIUM, CHROMIUM AND MOLYDENUM.
THESE ARE VERY VERY COSTLY ALLOYS.
Aerospace Applications
turbines shafts sheet metal work
Industrial Applications
Increased life of articles.
Reliability of machine parts
Pipings
AUTOMOTIVE
Engine parts such as connecting rods, wrist pins, valves, valve retainers and springs, rocker arms and camshafts, to name a few, lend themselves to fabrication from titanium, because it is durable, strong, lightweight and resists heat and corrosion.
Computer Industry
Modern Hard disks Modern pendrives
Human Implants
Surgical instruments Implants to repair
facture of bones...