Hangbo Alloy Group
Shanghai · Est. 2012
Guidance on welding nickel alloys — preventing hot cracking, distortion and carbide precipitation, with filler selection and argon purge practice.
Nickel alloys weld cleanly, but they do not behave like carbon steel or even 300-series stainless. Their combination of low thermal conductivity, high thermal expansion and a tendency toward hot cracking means a procedure that works on mild steel will produce porous, cracked or warped joints. This guide covers the failure modes fabricators actually see and the simple changes that prevent them.
Two physical properties dominate every nickel-alloy weld. Thermal conductivity is roughly a third of carbon steel, so heat stays localized in the arc instead of spreading through the part. At the same time, the coefficient of thermal expansion is high, so the joint shrinks hard as it cools. The practical result is a narrow, deep, heat-concentrated weld pool and significant distortion if the fit-up and clamping are not planned for it.
Most corrosion-resistant nickel alloys are also austenitic and fully non-magnetic, with no phase change on cooling to relieve stress. Any dissolved gas or surface contaminant is trapped in the solidifying puddle, producing porosity. Hot cracking — solidification cracking along the weld centerline or liquation cracking in the heat-affected zone — is the single most common failure, driven by low-melting sulfur, phosphorus and silicon films at grain boundaries.
The most effective defense is chemistry control. Keep the weld metal slightly overalloyed relative to the base metal so the final composition sits in a wider freezing range that resists centerline cracking. Match or overmatch the filler for corrosion resistance, and never dilute the puddle with carbon steel tooling, tack marks or mixed grinding debris.
Control heat input in the moderate range — enough to wet out and avoid cold lap, not so much that the HAZ soaks and sensitizes. Keep travel speed steady and avoid whip-and-pause techniques that reheat the solidifying puddle. Rigging and tacking should hold the joint against contraction rather than relying on the weld to pull it together. A clean, dedicated wire brush (never one used on carbon steel) on every joint is non-negotiable.
Because heat does not dissipate, nickel-alloy welds run hot. That invites both distortion and sensitization — chromium carbide precipitation in the 550 to 850°C band, which depletes the grain boundaries of chromium and hurts corrosion resistance. Minimize dwell, use controlled interpass temperature, and select a low-carbon or stabilized grade when the service is corrosive.
For any joint exposed to corrosion on the inside surface, purge the root side with argon. Without a backing gas, the back of the weld oxidizes and can form a brittle, carburized layer that no amount of pickling fully removes. A simple trailing shield or disposable purge dam keeps the hot zone in inert gas through solidification and early cooling.
Filler choice tracks the base alloy and the environment. For the common corrosion-resistant grades, a nickel-chromium-molybdenum wire such as ERNiCrMo-3 (Inconel 625 type) is a versatile default that stays resistant across a wide chemical range. Molybdenum-rich wires suit reducing Acid environments, while matching the base composition is preferred for high-temperature service to preserve creep strength.
For age-hardenable alloys, use a filler that does not overage or form brittle phases in the HAZ, and decide deliberately whether to weld in the solution-annealed or aged condition. The wrong filler is not a cosmetic problem — it sets the corrosion and high-temperature limit of the whole joint.
Yes, but the joint will only be as corrosion-resistant as its weakest alloy. Use a nickel-based filler that matches or exceeds the more demanding side, and plan for dilution. For a full selection rationale, see our nickel alloy vs stainless steel guide. Proper purging still applies on the corrosion-exposed face.
Most corrosion-resistant nickel alloys are used as-welded and do not require PWHT. Age-hardenable grades are a different case — they may need a solution anneal and age cycle to reach design strength. The fundamentals of that heat treatment are covered in our precipitation strengthening guide.
Grinding removes scale after the fact but cannot restore chromium lost to oxidation during cooling. An argon purge keeps the hot root face from reacting in the first place, which is what preserves corrosion resistance. This matters most for high-molybdenum grades like those discussed in our Hastelloy C22 corrosion resistance article.
As a dedicated nickel alloy manufacturer serving chemical processing, oil & gas, aerospace, power generation sectors, Hangbo Alloy Group supplies the grades discussed here across all standard product forms with full ASTM/ASME documentation and EN 10204 3.1 certification. Our material is specified for applications where corrosion resistance, high-temperature strength, and traceable quality are non-negotiable. See our production & testing facilities for more on how every heat is verified.