Welding Inspection & Metallurgy API ICP Self Study Notes

Nickel alloys are also susceptible to hot cracking, in some cases more so
than austenitic stainless steels. This hot tearing will occur as the weld pool
cools and solidifies. To help prevent hot cracking the weld joint should be:
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designed to minimize restraint and
the weld should be allowed to cool as quickly as possible.
The faster a nickel alloy weld solidifies (freezes), the less time it spends
in the temperature range where it can tear. For this reason pre-heating,
which slows down the cooling rate of the weld, is actually harmful, as it
permits more opportunity for hot tearing to occur.
As with austenitic stainless steels, the weldability of nickel alloys can also be
affected by the presence of high levels of low melting point elements like:
(1) sulfur, (2) phosphorus, (3) zinc, (4) copper and (5) lead. All of these
contaminants can lead to cracking in either the weld or base metal.