welding

1. WELDABILITY OF Ni & Ti ALLOYS
AND
SELECTION OF WELDING
PROCESS & PROCEDURE
Submitted by,
saroja.s
(ME , welding technology)
GCE,SALEM

2.  Nickel like copper, its FCC structure at all
temperature .
 Good corrosion resistance. its used food
processing plants ,chemical container and
other similar application.
 Nickel is used as alloying element to improve
mechanic properties.
 Resistant of oxidation in high temperature.
 Nickel melting point is 1453˚C.
 Nieq=%Ni+30*%C+0.5*%Mn.

6. Solid solution alloy:
 Ni-Cu=alloy 30-45%Cu its monel.
 Ni-Cr=16-20%Cr its nichrome.
 Ni-Fe-Cr=20-25%Ni,13-22%Cr,Fe-bal its INCONEL
 Ni-Mo=16-28%Mo,less % of Cr&Ni.
Precipitation hardening:
 Ni-cu.66.5%Ni,29.5%Cu monel
 Ni-Cr.76%Ni,19.5%Cr nichrome
 Ni-Fe-Cr. 73%Ni,15.5%Cr,7%Fe inconel

7. Solid Solution
Nickel - Copper
• Resistance to Sea Water
• Naval Application, Chlorination Plants, Water meter parts, pump
shafts, feed water heaters
Nickel-Chromium
• Corrosion Resistance at Elevated Temp
• Furnace muffles, heat treating equipment, nuclear steam tubing, heat
exchangers, aircraft engine components
Nickel-Iron-Chromium
• High Temp Strength, Resistance to Oxidation
• Heat exchangers, carburizing fixtures, pickling tank heaters, spent
nuclear fuel element recovery, hydrofluoric acid production
Nickel-Molybdenum
• Low temp corrosion resistance, some acids
• Cryogenic Service

8. Precipitation-hardening
Nickel-Copper Alloys
• Resistant to Sea Water, Chlorine
• Pump shafts, impellers, oil well drill collars, electronic components,
springs
•Sensitive to strain age cracking
Nickel-Chromium
• Good high temp oxidation
• Gas turbine components
Nickel-Iron-Chromium
• Forging applications

9. Phase diagram of Ni-Cu

13. MONEL AND INCONEL:
WELDING PROCESS:TIG,MIG,SMAW,elactron beam
PREHEAT: No
POST WELD: Necessary to avoid intergranular corrosion
REMARK: Good weldability
A=RECOMMENDED;C=POSSIBLY USABLE BUT NOT POPULAR
NO=NOT RECOMMENDED
proces
s
SMA
W
TIG PLAS
MA
SAW MIG FCAW
NICKEL A A A C A NO
INCON
EL
A A A NO A NO
MONEL A A A C A NO

14. GMAW techniques
 GMAW uses solid wires use for filler metal.
 The recommended polarity is DCEP with, normally,
constant-potential power sources.
 With a solid wire, the dominant mode of metal
transfer is spray transfer, but short circuiting and
globular welding are also widely employed
depending on the welding position and joint
thickness.
 For shielding the weld zone, shielding normally
use argon or argon mixed with helium.

17.  Ni & its alloy are used in coin.
 Chemical plant , heat exchanger , reaction
furnace are used
 Turbine blades,bumper , cutting tool
Imperfection:
Porosity
Lack of inter run fusion
Weld metal solidification cracking
Precaution:
Post weld heat treatment

18.  Pure Ti low tensile strength but excellent
ductility
 High strength to weight ratio compare to Al
 Suitable alloys added properties can
increased
 Above 650℃ reduce oxidation resistance
 Low thermal expansion & thermal
conductivity.
 Room temp , HCS called alpha phase. above
the 883℃ beta phase in BCC.
 Melting point is 1670 ℃

20. Ti phase diagram

21. Designation Commerically Medium
Pure Titanium Strength
Alloys
Alloy Type Alpha Alpha-Beta
0.2% Proof Stress MPa 345 - 480 480 – 550
Tensile Strength MPa 480 - 620 600 – 650
Elongation % 20 - 25 15 -20
Tensile Modulus GPa 103 104
Torosion Modulus Gpa 45 43
Hardness HV 160 - 220 200 - 280
Density kg/1 4.51 4.48 - 4.51
Thermal Expansion 10-6/ºC 8.9 8.3
Conductivity W/mK 22 8.0
Specific Heat J/kg/ºC 525 544
Properties of Ti

22.  i) commercially pure titanium
 Ii) alpha and near alpha alloy
 Iii) alpha- beta alloy
 Iv) beta alloy

23.  pure Ti 98.5 to 99 %Ti
 pure Ti has moderate strength but good
ductility. Its has good corrosion resistance,
formability , weldability
 Very important to maintain iron content
below 0.05%
 Use low iron content filler wire , avoid steel
brushes
 Weld in annealed condition . because stress
relieved , not need in after welding

24. Alpha Ti
 similar to pure Ti.
 alpha alloys and near alpha alloys have good
weldability because of there good ductility.
 The strength of cold worked material in the HAZ
is decreased as a result of heating.
 Therefore alloy are normally weld in annealed
condition
 Its has higher strength at elevated temperature

25.  Near alpha alloy:
 Its excellent creep strength at elevated
temperature
 they are weldable but residual stress can be
high
 therefore stress relieving of weldment is
always recommended.
 Iron contamination degrades creep strength
and should be avoided

26. Beta +alpha Ti:
 Ti-6Al-4V alloy has the best weldability
 Ti-10V-2Fe-3Al has good weldability
because it is highly beta stabilized and fine
grain size during welding
 Annealing temp 750-790℃
Beta alloy:
 Beta alloy weldable in either annealed or the
heat treated condition
 Weld joints have good ductility but relatively
low strength.

27. α & pure Ti:
WELDING PROCESS:TIG,MIG, electron beam,resistance, flash
butt.
PREHEAT: weld in annealed condition
POST WELD: stress relief 400-650⁰ C
REMARK: highly reactive requires good shielding. No filler is
used below 2.5mm thickness, otherwise parent metal or
commercial purity titanium is used
(α+β)Ti:
WELDING PROCESS:TIG, electron beam, resistance, flash butt
PREHEAT: No
POSTWELD: 2hours at 538⁰ C complete aging during stress
relief

28. A=RECOMMENDED;C=POSSIBLY USABLE BUT NOT POPULAR
NO=NOT RECOMMENDED
PROCESS SMAW TIG PLASMA SMA MIG FCAW
Ti & its
alloy
NO A A NO A NO
Beta Ti:
Process : electron beam , resistance, flash butt
Preheat: weld in annealed condition
Post weld heat : -
Remark : not recommended

30.  major problem with Ti weldments Is porosity.
 It is a persistent problem and mostly it is caused
by gas bubbles formed during solidification of
weld metal.
 Oxidation form.
 Other variables affecting porosity in Ti welds:
 Heat input
 Cooling rare
 Welding speed
 Arc voltage
 Shielding gas flow rate

31.  i) ASM handbook vol 6A-welding fundamental
and process
 Ii) Nadkarni .S.V. modern arc welding
technology
 Iii)Dr.R.S.parmar: welding engineering and
technology