Nickel Alloy Filler Metal Selection: A Complete Guide to ERNiCrMo, ERNiCrFe, and ERNiMo Designations
Nickel alloy filler metals are not interchangeable with carbon or stainless steel fillers — and in many cases they are not interchangeable with each other. Using the wrong ERNiCrMo filler on a Hastelloy C-276 pipe fitting joint can result in a weld deposit with lower corrosion resistance than the base metal. Using an ERNiCrFe filler where ERNiCrMo is required can cause HAZ sensitisation or inadequate properties at service temperature. This article maps every major nickel alloy base metal to its correct filler, the AWS classification, and the critical limitations to state on the WPS.
The ERNiCrMo Family
The ERNiCrMo suffix indicates the filler is a Ni-Cr-Mo alloy — the dominant family for corrosion-resistant nickel alloy welding. The number suffix distinguishes compositions within the family:
| AWS Class | UNS | Base Metal Application | Key Notes |
|---|---|---|---|
| ERNiCrMo-3 | N06625 | Inconel 625, Incoloy 825, 904L overlay, dissimilar welds | Most widely used Ni-alloy filler. Also used as universal overlay filler. |
| ERNiCrMo-4 | N10276 | Hastelloy C-276 | Do NOT substitute ERNiCrMo-3 — Mo content lower, reduces corrosion resistance. |
| ERNiCrMo-7 | N06455 | Hastelloy C-4 | Ti-stabilised, usable as-welded to 650°C. |
| ERNiCrMo-10 | N06022 | Hastelloy C-22 | Higher Cr than C-276 filler — correct for C-22 base metal. |
| ERNiCrMo-13 | N06059 | Alloy 59 (2.4605) | PRE ~70 — for ultra-high alloy mixed acid service. |
| ERNiCrMo-17 | N06200 | Hastelloy C-2000 | Contains Cu — specifically for C-2000 base metal only. |
The ERNiCrFe Family
ERNiCrFe fillers are used for Ni-Cr-Fe base metals (Inconel 600/601/690 family) and for dissimilar welds between CrMo steel and austenitic stainless. The key members:
- ERNiCrFe-6 (N06082, FM82): Inconel 600, Incoloy 800/800H, nuclear PWR primary circuit welds. Also used as butter on CrMo steel side of DMW before joining to stainless.
- ERNiCrFe-7 (N06052, FM52): Inconel 690 (PWR steam generator replacement). Low Fe — DDC (ductility dip cracking) risk in thick sections; ERNiCrFe-7A or FM52M preferred for heavy wall.
- ERNiCrFe-11 (N06601): Inconel 601 — contains Al for oxide layer retention in oxidising high-temperature service.
- ENiCrFe-3 (covered electrode only): DMW butter on P11/P22 CrMo side when joining to 316L — prevents carbon migration into weld metal.
The ERNiMo Family (B-Family Alloys)
- ERNiMo-7 (N10665): Hastelloy B-2 — no longer specified for new work.
- ERNiMo-10 (N10675): Hastelloy B-3 — correct filler for all new B-family fabrications. As-welded without PWSA required.
Stating Filler Metal on the WPS and PO
The WPS must state the AWS classification and the filler UNS number — not just a trade name. On the PO for shop-fabricated fitting assemblies, state: "Filler metal to be ERNiCrMo-[X] per AWS A5.14, UNS [N0XXXX]. Certificate of conformance required." For field welds on critical service, the filler wire heat certificate must be held in the ITP documentation package linked to the fitting heat number.