ER347 vs ER308L TIG filler is not a “higher number is better” decision. Both classifications sit in AWS A5.9 and both can appear around 18Cr-8Ni stainless work, but they address different alloy and service paths. ER308L is the common low-carbon choice around 304/304L-type stainless. ER347 is niobium-stabilized and is the more natural starting point when the base metal, WPS, or service requirement calls for stabilized 321/347 stainless behavior.
ER347 vs ER308L TIG filler starts with the base metal and service
The Weld Support Parts ER347 TIG rod page places ER347 on the common 321/347 stabilized-stainless path. The ER308L TIG rod page places ER308L on the common 304/304L path. Those pages are lookup starting points, not procedure approvals.
ESAB’s current OK Tigrod 347 data classifies the rod as SFA/AWS A5.9 ER347 and describes it as a chromium-nickel rod stabilized with niobium for stabilized austenitic 18Cr-8Ni alloys. ESAB specifically notes the niobium stabilization and recommends that product path for higher-temperature use. That manufacturer statement is useful selection context, but it does not establish that ER347 is automatically correct for every elevated-temperature stainless job.
ESAB’s current OK Tigrod 308L data classifies that product as SFA/AWS A5.9 ER308L. ESAB describes it as a low-carbon 18Cr-8Ni filler and says it can be used on low-carbon and niobium-stabilized steels of the same general type when service temperature does not exceed 350°C. That is an ESAB product recommendation for its rod, not a universal code limit that should be copied into an unrelated WPS.
What the classification tells you—and what it does not
An AWS classification is a controlled filler-metal designation. It does not by itself identify your exact brand, diameter, package, heat or lot, shielding setup, joint design, base-metal condition, or qualified welding procedure. “ER347” and “ER308L” are therefore classification decisions first; the exact product form and manufacturer data must still be checked before purchase and use.
Do not confuse manufacturer typical chemistry or mechanical-property tables with the acceptance limits of the AWS specification. Typical values describe the tested or representative product data reported by that manufacturer. Specification limits come from the applicable AWS standard and the exact product’s certification documentation. For code work, the WPS and project requirements control the usable range.
Where ER347 usually earns the closer look
ER347 deserves attention when the job involves stabilized grades such as 321 or 347, especially when the service condition makes stabilization relevant. The filler’s niobium addition is the defining difference highlighted by ESAB. If a drawing, material specification, customer requirement, repair procedure, or WPS identifies ER347, replacing it with ER308L because both are stainless fillers can change the intended weld-metal chemistry.
That does not mean every weld on 321 stainless must be made with ER347. ESAB’s own ER308L literature illustrates why blanket rules are risky: it allows a stabilized-steel path under stated service conditions. The correct question is not “Can ER308L ever weld stabilized stainless?” but “What filler does the applicable WPS, code, engineering requirement, and service environment call for on this specific joint?”
Where ER308L remains the normal starting point
For routine 304 and 304L stainless GTAW, ER308L remains the common starting point because the low-carbon 18Cr-8Ni chemistry is aimed directly at that family. If the base metal is 304L and there is no dissimilar-metal, elevated-temperature, corrosion, or code-driven reason to change filler, jumping to ER347 simply because it sounds more specialized usually adds complexity without solving a defined requirement.
For dissimilar stainless combinations, unknown material, pressure-containing work, high-temperature service, corrosive service, or repairs where the original metallurgy is uncertain, stop using a quick classification chart as the final answer. Those jobs need material identification and procedure review.
Use WSP as a starting point, not an approval
The WSP Filler Metal Finder is designed to narrow a job toward an AWS classification, product form, and verification list. It explicitly does not replace a WPS, code requirement, manufacturer data sheet, customer specification, or engineering approval. The broader Alloy Support library is useful when you already know the process or AWS grade and want to compare nearby classifications.
Practical decision sequence
Identify the exact base-metal grades first. Then confirm whether the service is ordinary-temperature fabrication, elevated-temperature service, corrosion-critical service, pressure or code work, or a repair governed by an existing procedure. Check the WPS and project requirements before choosing the filler. Only after the classification is settled should you select the exact manufacturer product, TIG rod diameter, package, and supporting consumables.
For this comparison, the useful distinction is simple: ER308L is the common 304/304L path; ER347 is the stabilized 321/347 path when stabilization and service requirements call for it. The exceptions are important enough that the final choice still belongs to the qualified procedure, not a generic chart.
Featured image: contextual welding photo by Collab Media via Unsplash; it does not depict a specific ER347 or ER308L product.
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