ER318 and ER316L are both Cr-Ni-Mo stainless steel filler metals, but they are not identical and should not be substituted automatically.
The Main Metallurgical Difference
ER318 uses niobium stabilization. ER316L relies mainly on low carbon content to reduce the risk of sensitization.
ER318 generally contains:
- 18.0–20.0% chromium
- 11.0–14.0% nickel
- 2.0–3.0% molybdenum
- Niobium controlled in relation to carbon
- Up to 0.08% carbon
The niobium requirement is a key point that separates ER318 from ER316L.
When Is ER318 Selected?
ER318 may be selected when:
- A stabilized filler is required
- The matching base metal is niobium-stabilized
- The approved welding procedure specifies ER318
- The project requires a stabilized Cr-Ni-Mo weld deposit
- Service includes thermal exposure that makes stabilization relevant
When Is ER316L Selected?
ER316L is commonly selected when:
- Welding 316L stainless steel
- A low-carbon filler is specified
- The procedure requires ER316L
- Post-weld corrosion behavior is addressed through low carbon rather than stabilization
- Broad commercial availability is a priority
Can ER318 Replace ER316L?
Not without engineering approval. Substituting filler metals can affect:
- Welding-procedure qualification
- Weld-metal chemistry
- Ferrite content
- Mechanical performance
- Corrosion behavior
- Code compliance
Even where two fillers contain similar levels of chromium, nickel, and molybdenum, their stabilization strategy and intended matching base materials may differ.
Which One Should Buyers Choose?
The selection should begin with the base-metal designation and approved welding procedure-not with price or availability. Buyers should also review service temperature, corrosion medium, joint design, required inspection, and applicable construction code.
Dayang Welding can support the supply of stainless steel filler metals according to the specified classification, diameter, product form, and project requirements.
