Nickel alloy filler selection determines whether your weld resists corrosion, withstands high temperatures, and avoids cracking. Unlike carbon steel where one or two fillers cover most jobs, nickel alloys require precise matching between filler chemistry, base metal, and service conditions. Get it wrong, and the weld fails from hot cracking, galvanic corrosion, or loss of high-temperature strength.
ERNiCrMo-3 (Inconel 625 chemistry) is the closest thing to a universal nickel filler. It covers the widest range of base alloys and dissimilar combinations. But some alloys demand specific fillers that nothing else can replace.
Master Filler Selection Chart
| Base Alloy | UNS | Primary Filler (TIG/MIG) | Stick Electrode | Notes |
|---|---|---|---|---|
| Inconel 600 | N06600 | ERNiCr-3 | ENiCrFe-3 | Standard Ni-Cr filler; also for 601 |
| Inconel 601 | N06601 | ERNiCr-3 or ERNiCrMo-3 | ENiCrFe-3 | ERNiCrMo-3 for added corrosion resistance |
| Inconel 617 | N06617 | ERNiCrCoMo-1 | ENiCrCoMo-1 | Cobalt-bearing filler matches base chemistry |
| Inconel 625 | N06625 | ERNiCrMo-3 | ENiCrMo-3 | Matching filler; most popular Ni filler overall |
| Inconel 718 | N07718 | ERNiFeCr-2 | ENiCrFe-3* | Matching filler; responds to aging heat treatment |
| Inconel X-750 | N07750 | ERNiCr-3 | ENiCrFe-3 | Does not match; X-750 is precipitation hardened |
| Incoloy 800/800H/800HT | N08800/N08810/N08811 | ERNiCr-3 or ERNiCrMo-3 | ENiCrFe-3 | Nickel filler preferred over stainless filler |
| Incoloy 825 | N08825 | ERNiCrMo-3 | ENiCrMo-3 | Must match Mo content for corrosion resistance |
| Monel 400 | N04400 | ERNiCu-7 | ENiCu-7 | Matching Ni-Cu filler for seawater service |
| Monel K-500 | N05500 | ERNiCu-7 | ENiCu-7 | Same filler as 400; K-500 is age-hardened |
| Hastelloy C-276 | N10276 | ERNiCrMo-4 | ENiCrMo-4 | High Mo for chloride resistance; matching filler |
| Hastelloy C-22 | N06022 | ERNiCrMo-10 | ENiCrMo-10 | Matching filler; improved Cr for oxidizing acids |
| Hastelloy C-2000 | N06200 | ERNiCrMo-17 | ENiCrMo-17 | Cu addition for reducing acids |
| Hastelloy B-3 | N10675 | ERNiMo-10 | ENiMo-10 | High Mo filler for HCl service |
| Hastelloy G-30 | N06030 | ERNiCrMo-11 | ENiCrMo-11 | Phosphoric acid service |
| Waspaloy | N07001 | ERNiCrMo-3 or ERNiCr-3 | ENiCrFe-3 | Gamma-prime hardened; SAC risk is very high |
| Haynes 230 | N06230 | ERNiCrWMo-1 | ENiCrWMo-1 | Tungsten-bearing for high-temp oxidation |
| Haynes 556 | R30556 | ERNiCrCoMo-1 or ERNiCrMo-3 | ENiCrCoMo-1 | Multi-purpose high-temp alloy |
| Nickel 200/201 | N02200/N02201 | ERNi-1 | ENi-1 | Pure nickel filler; 201 (low carbon) for service above 600F |
*For Inconel 718 stick welding, ENiCrFe-3 is used as a non-matching (lower strength) alternative when ERNiFeCr-2 stick electrodes aren’t available.
Dissimilar Joint Filler Selection
When joining different nickel alloys to each other or to stainless steel and carbon steel, the filler must be compatible with both base metals and survive the service environment.
| Joint Combination | Recommended Filler | Alternate | Notes |
|---|---|---|---|
| Inconel 625 to 304/316 SS | ERNiCrMo-3 | ERNiCr-3 | ERNiCrMo-3 handles dilution from both sides |
| Inconel 625 to Carbon Steel | ERNiCrMo-3 | -- | Butter the CS side first if dilution is a concern |
| Inconel 600 to Carbon Steel | ERNiCr-3 | ERNiCrMo-3 | Common in power plant transitions |
| Monel 400 to Carbon Steel | ERNiCu-7 | ERNiCr-3 | ERNiCr-3 for higher strength dissimilar joint |
| Monel 400 to 304 SS | ERNiCr-3 | ERNiCrMo-3 | Ni-Cr filler handles both chemistries |
| C-276 to 316L SS | ERNiCrMo-4 | ERNiCrMo-3 | Match C-276 for maximum corrosion resistance |
| Inconel 625 to Monel 400 | ERNiCrMo-3 | -- | 625 filler compatible with both alloys |
| Inconel 800 to Carbon Steel | ERNiCr-3 | ERNiCrMo-3 | Standard power plant boiler tube-to-header joint |
| Nickel 200 to Carbon Steel | ERNi-1 | ERNiCr-3 | ERNi-1 minimizes carbon migration from CS |
The Universal Nickel Filler: ERNiCrMo-3
ERNiCrMo-3 appears in more rows of the chart than any other filler. Its broad compatibility comes from a balanced chemistry:
- 22% chromium provides oxidation and corrosion resistance
- 9% molybdenum adds pitting and crevice corrosion resistance
- 62% nickel base provides the matrix for high-temperature stability
- 3.5% niobium strengthens the deposit and reduces hot cracking sensitivity
It handles dilution from iron (carbon steel and stainless), copper (Monel), and most other common alloying elements without forming brittle phases. If you’re unsure which filler to use for a nickel alloy joint, ERNiCrMo-3 is the safest default.
Limitations of ERNiCrMo-3:
- Doesn’t match Monel’s copper content (ERNiCu-7 is better for Monel-to-Monel)
- Doesn’t match C-276’s high molybdenum (ERNiCrMo-4 is better for maximum chloride resistance)
- Not suitable for Hastelloy B-series (need high-Mo ERNiMo fillers)
- Doesn’t respond to precipitation hardening (can’t replace ERNiFeCr-2 when aged properties are required)
Filler Properties Comparison
| Filler | Primary Chemistry | Tensile (ksi, as-welded) | Key Corrosion Resistance |
|---|---|---|---|
| ERNi-1 | 99Ni | 55-65 | Caustic (NaOH), dry chlorine |
| ERNiCu-7 | 67Ni-30Cu | 70-80 | Seawater, HF acid, brackish water |
| ERNiCr-3 | 72Ni-20Cr | 80-95 | Oxidation, carburization, general high-temp |
| ERNiCrMo-3 | 62Ni-22Cr-9Mo | 100-120 | Broad: pitting, crevice, SCC, high-temp |
| ERNiCrMo-4 | 57Ni-16Cr-16Mo | 100-115 | Best for chloride pitting and crevice corrosion |
| ERNiFeCr-2 | 53Ni-19Cr-18Fe-5Nb | 120-140 (as-welded); 170+ (aged) | Moderate; designed for strength, not corrosion |
| ERNiMo-7/10 | 65Ni-28Mo | 100-110 | HCl, H2SO4 (reducing acids) |
Selection by Service Environment
When the joint serves a specific corrosive environment, the service conditions determine filler selection, not just the base metal match.
| Service Environment | Primary Filler | Why |
|---|---|---|
| Chloride-containing (seawater, brine, HCl) | ERNiCrMo-4 or ERNiCrMo-3 | High Mo content resists pitting and crevice corrosion |
| Oxidizing acids (HNO3, chromic acid) | ERNiCrMo-10 (C-22) | Higher Cr content for oxidizing conditions |
| Reducing acids (HCl, H2SO4) | ERNiMo-7 or ERNiMo-10 | High Mo without Cr for reducing environments |
| Caustic (NaOH, KOH) | ERNi-1 | Pure nickel has best caustic resistance |
| Hydrofluoric acid | ERNiCu-7 | Copper content provides HF resistance |
| High temperature oxidation (over 1000F) | ERNiCr-3 or ERNiCrMo-3 | Chromium forms protective Cr2O3 scale |
| Sulfidation (refinery service) | ERNiCrMo-3 | Nickel-chrome-moly resists high-temp sulfur attack |
Common Filler Selection Mistakes
Using stainless filler on nickel alloy base metal. ER308L or ER316L has too little nickel to match the base metal’s corrosion resistance or high-temperature stability. The weld deposit corrodes preferentially in aggressive environments and may lack the strength needed at elevated temperatures. Always use a nickel-based filler when at least one base metal is a nickel alloy.
Substituting ERNiCrMo-3 for ERNiCu-7 on Monel. ERNiCrMo-3 is compatible with Monel in terms of weldability, but the chromium-rich deposit doesn’t match Monel’s corrosion profile. In hydrofluoric acid or deaerated seawater, the 625-chemistry weld corrodes differently than the Monel base metal. Use ERNiCu-7 for Monel-to-Monel joints where the service environment specifically requires the nickel-copper corrosion resistance.
Ignoring sulfur and phosphorus limits in the filler. Premium-quality filler from reputable manufacturers holds sulfur below 0.005% and phosphorus below 0.010%. Economy-grade filler from unknown sources may have higher impurity levels that dramatically increase hot cracking risk. Always check the mill test report, especially for critical applications.
Using the wrong filler on precipitation-hardened alloys. ERNiCrMo-3 works on solid-solution alloys but doesn’t respond to aging heat treatment. If the application requires the weld to develop aged-condition strength (like on Inconel 718 turbine components), ERNiFeCr-2 is the only correct choice. Similarly, ERNiCr-3 on Waspaloy won’t develop the gamma-prime strengthening that the base metal relies on.
Storage and Handling
Nickel alloy filler wire and rod are expensive (typically $40-100/lb for TIG rod, more for specialty alloys). Protect your investment:
- Store in sealed containers. Moisture absorption causes porosity. Reseal opened packages immediately.
- Handle with clean gloves. Sulfur from skin oils causes hot cracking. Always wear clean nitrile or cotton gloves when handling nickel filler.
- Segregate from other alloys. Don’t store nickel filler next to carbon steel wire. Cross-contamination with iron causes weld defects.
- Track lot numbers. For code work, filler metal must be traceable to the mill test report. Keep the AWS classification label with the filler at all times.
- Rod ovens for stick electrodes. ENiCrFe-3, ENiCrMo-3, and other nickel alloy stick electrodes pick up moisture through their basic coatings. Store at 250-300F in a rod oven after opening the sealed can. If electrodes have been exposed to humidity for more than 4 hours, re-bake at 600F for 1 hour before use.
Stick Electrode Considerations
Covered electrodes (stick welding) for nickel alloys use basic or lime-type coatings. They run on DCEP (reverse polarity) with a short arc length. Key differences from TIG:
- Higher dilution per pass (especially root passes), which affects the deposit chemistry
- Slag removal between passes is critical; nickel alloy slag is more adherent than steel slag and doesn’t self-release
- Not recommended for root passes on pipe when the root must meet corrosion requirements (TIG root, stick fill/cap is a common combination)
- Limited positions; nickel alloy stick electrodes don’t run as smoothly out of position as carbon steel electrodes
- Use a slight drag angle (5-10 degrees) and keep a tight arc; long arcs cause porosity and nitrogen pickup
- Chip slag completely between every pass using a chipping hammer and stainless steel brush; any trapped slag creates inclusions that show up on radiography
Submerged Arc Welding (SAW) Fillers
For heavy-section nickel alloy welding and cladding, SAW wire and strip are available in most major filler classifications. SAW produces high deposition rates for weld overlay (cladding) but has higher dilution than TIG or MIG. Common SAW fillers:
- EQNiCrMo-3 (strip or wire): 625-chemistry for overlay on carbon steel vessels
- EQNiCr-3 (strip or wire): Inconel 82 chemistry for general overlay
- ERNiCrMo-4 (wire): C-276 chemistry for chloride-resistant overlay
SAW fluxes for nickel alloys must be low-basicity or neutral types specifically designed for nickel. Standard carbon steel fluxes contaminate the deposit with silicon, manganese, and other elements that promote hot cracking.
For detailed welding procedures on specific alloys, see the Inconel 625 welding guide, the Inconel 718 welding guide, and the Monel welding guide.
Back to the nickel alloys welding category.