Nickel and cobalt alloys have a unique combination of physical and mechanical properties that make them resistant to corrosive attack. The attributes of the base metal carry over to weldments to a high degree, but the quality of weldments depends on the welding process and limitations in welding material choice. Welding procedures for nickel and cobalt alloys are generally similar to those for stainless steels, though modifications may be needed if the base metal has not been fully annealed. Overmatching the composition of the weld metal can provide benefits in very aggressive corrosive environments.

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NICKEL AND COBALT ALLOYS
INTRODUCTION

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Unique combination of
physical and mechanical
properties
Cost???

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Is Nickel and Cobalt alloys is
resistance to corrosive
attack?

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Attributes of base metal to
high degree…….

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Quality of weldments and
process?
Limitation in choice of
welding……

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Is Welding Procedure for
Nickel and Cobalt alloy is
similar to Stainless steel?

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Amount of Hot Work/ Cold
Work in base metal.
VS
Mechanical Properties.

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Is modification in Welding
Procedure is required if
base metal is not fully
annealed?
Option for PWHT?

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Solution Annealing
and
Welds made in Nickel Moly
Alloy B (N10001) & Nickel
Silicon cast alloys

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How to deal with very
aggressive corrosive
environment?

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Benefits in using
overmatching composition
in weldmetal?
Eg:
1) N06686 to Super Austenitic Stainless steel.
2) Alloy C-276 (N10276) base metal.

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Precipitation Hardening &
PWHT

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Post weld stress relief in
hydrofluoric acid or certain
caustic solutions.
Eg : Alloy 400 (N04400)

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Essential Parameters for
selection of Welding
Process….