How to Weld Nickel-Based Alloys

Nickel-based alloys are known for their excellent strength, corrosion resistance, and high-temperature performance. These properties make them the material of choice in demanding industries like aerospace, power generation, chemical processing, and marine engineering. However, welding nickel-based alloys requires specialized knowledge and techniques to ensure integrity and performance. In this comprehensive guide brought to you by sasaalloy, we will explore how to weld nickel-based alloys, the challenges involved, recommended processes, and best practices for achieving high-quality welds.

What Are Nickel-Based Alloys?

Nickel-based alloys are materials where nickel is the primary element, often combined with chromium, iron, molybdenum, cobalt, titanium, or copper to enhance specific properties. Common nickel-based alloys include:

• Inconel (e.g., 625, 718) — High strength and corrosion resistance at elevated temperatures.

• Monel (e.g., 400) — Excellent resistance to seawater and acids.

• Hastelloy (e.g., C276) — Outstanding corrosion resistance in chemical environments.

These alloys are often used in critical applications where weld quality is vital.

Challenges of Welding Nickel-Based Alloys

Welding nickel alloys presents unique challenges:

• Hot cracking susceptibility: Nickel alloys are prone to solidification cracking if not welded correctly.

• High thermal expansion: This can lead to distortion or residual stress if not properly managed.

• Porosity risk: Nickel alloys can absorb gases like hydrogen and oxygen, leading to porosity in welds.

• Work hardening: These alloys can harden rapidly during machining or preparation, making handling more difficult.

Understanding these challenges is essential for successful welding.

Recommended Welding Processes

1. Gas Tungsten Arc Welding (GTAW / TIG)

• Best for: Thin sections, precision welds, critical joints.

• Advantages:

  • Excellent control over heat input.

  • Produces high-purity welds with minimal defects.

2. Shielded Metal Arc Welding (SMAW / Stick Welding)

• Best for: Field work, maintenance, and repair.

• Advantages:

  • Good for thicker sections.

  • Less equipment complexity.

3. Gas Metal Arc Welding (GMAW / MIG)

• Best for: Medium-thickness sections, production welding.

• Advantages:

  • Faster deposition rates.

  • Suitable for automated or semi-automated processes.

4. Submerged Arc Welding (SAW)

• Best for: Very thick sections in industrial settings.

• Advantages:

  • High deposition rates.

  • Deep penetration welds.

Key Best Practices for Welding Nickel-Based Alloys

1. Material Preparation

• Clean the surfaces thoroughly to remove oil, grease, paint, and oxides.

• Use dedicated brushes and tools for nickel alloys to avoid cross-contamination.

• Ensure tight fit-up to minimize gaps and prevent excessive heat input.

2. Control Heat Input

• Use lower heat inputs to reduce the risk of hot cracking.

• Employ stringer beads rather than weaving to keep heat input consistent.

• Allow adequate cooling between passes.

3. Use Correct Filler Metal

• Match the filler metal to the base material composition to maintain corrosion and strength properties.

• For example:

  • Inconel 625 base metal → Inconel 625 filler.

  • Monel 400 base metal → Monel filler wire.

4. Shielding Gas Selection

• GTAW: 100% argon or argon-helium mixtures.

• GMAW: Argon with small amounts of oxygen or carbon dioxide (for spray transfer).

• Maintain proper gas flow to avoid porosity.

5. Minimize Contamination

• Avoid sulfur, lead, and other low-melting contaminants that can cause cracking.

• Do not use lubricants or marking crayons containing sulfur.

6. Interpass Temperature Control

• Monitor interpass temperatures, typically keeping them below 150–200°C (300–400°F), depending on the alloy.

• Excessive interpass temperature increases the risk of microstructural issues.

Post-Weld Treatment

• Solution annealing (for certain alloys like Inconel 625 or Hastelloy C276) may be required to restore corrosion resistance and mechanical properties.

• Pickling or passivation to remove heat tint and restore the protective oxide layer.

• Non-destructive testing (NDT), such as dye penetrant or radiographic inspection, to verify weld integrity.

Common Defects to Watch For

Applications Where Welded Nickel Alloys Excel

• Aerospace: Jet engine components, exhaust systems.

• Power generation: Heat exchangers, boiler tubes.

• Chemical processing: Reactors, piping.

• Marine: Propeller shafts, fasteners.

At sasaalloy, we supply certified nickel alloy materials and technical support to help you achieve superior weld quality in these demanding applications.

Conclusion

Welding nickel-based alloys requires precision, proper technique, and a clear understanding of the material’s behavior under heat. By selecting the right welding process, filler metal, and parameters—and by adhering to best practices—you can produce high-integrity welds that meet the performance demands of critical applications.

If you’re sourcing nickel alloys for welding or require guidance on proper welding procedures, sasaalloy is ready to assist. We provide top-quality materials and technical expertise to help you succeed in your projects. Contact our team for tailored solutions and support.