Guides / Materials

AMS Specifications Commonly Called Out on Inconel Drawings

July 29, 2026

An Inconel drawing that just says “Inconel 718” is missing information a mill or a machine shop needs to actually source the right material condition. That is where an AMS number comes in, and it is one of the most common things buyers ask about when they inherit a drawing from an aerospace program. This article covers commercial aerospace use.

What an AMS number is and why it’s on the drawing

AMS stands for Aerospace Material Specification, a set of standards published by SAE International that define exact material composition, processing condition, mechanical properties and testing requirements for a given form of an alloy. “Inconel 718” describes a family of composition, but it does not by itself say whether the material should be solution treated, aged, supplied as bar or forging stock, or tested to a specific set of mechanical property minimums. The AMS number pins that down.

Aerospace buyers reference the AMS number instead of the trade name because it is the traceable, auditable requirement that a mill certificate gets checked against. Two bars of Inconel 718 from different mills can differ in grain structure, heat treatment condition or testing rigor unless both are certified to the same AMS spec. For a part with any FAI, PMI or aerospace paperwork requirement, the AMS callout is usually the part of the drawing note that actually controls sourcing.

Example AMS specs buyers see on 718 and 625 drawings

The AMS number most commonly associated with Inconel 718 bar and forging stock covers solution heat treated, precipitation hardenable 718 in bar, forging and ring form. For Inconel 625, buyers commonly see specs covering 625 bar, forgings and rings in various heat treatment conditions.

Treat any specific spec number mentioned in general reading, including this article, as a starting reference rather than a substitute for the drawing. AMS specs also exist for sheet, plate, wire and weld filler in addition to bar and forgings, each under its own number, and the exact spec that applies to a given part depends on stock form, heat treatment condition and sometimes the specific program’s requirements. Always confirm the exact callout against the drawing and the mill certificate rather than assuming it from the alloy name alone.

How this ties to mill cert verification and PMI

A mill certificate that references the correct AMS number is the paper trail that shows the material actually meets the composition, processing and mechanical property requirements the drawing calls for, not just that it is generically Inconel 718 or Inconel 625. Positive material identification, PMI, testing on incoming stock is the physical check that backs up the paperwork, confirming the alloy composition of the actual bar or forging in hand rather than trusting the certificate alone.

Together, the AMS callout, the mill cert and PMI testing are what catch a substitute or mislabeled alloy before it becomes a delivered part. Skipping any one of the three leaves a gap, especially on a nickel alloy part where visual inspection cannot tell one grade from another.

What to put on your RFQ

If the drawing has an AMS number, include it exactly as written on the RFQ rather than paraphrasing it as Inconel 718 or aerospace grade. If mill cert traceability to that AMS number is required, say so explicitly, and state whether PMI testing on incoming stock is required for this order or only for a first article. If the drawing does not reference an AMS number but the part is going into an aerospace program, say that too, since it usually means the shop should ask before assuming a commercial-grade material condition is acceptable. The more of this detail that is on the RFQ up front, the fewer round trips it takes to get a quote against the material the part actually needs.

When the AMS callout is missing or unclear

Buyers working from a legacy drawing sometimes find a partial or illegible AMS reference, or none at all on a part that clearly needs one. In that case, it is worth going back to the original engineering source rather than guessing, since specifying the wrong condition can mean a part that machines fine and inspects fine but does not actually meet the mechanical property minimums the application depends on. A shop that regularly works aerospace nickel alloy parts can often help narrow down the likely spec once it knows the stock form, whether the part is age-hardened, and what program or customer the drawing originally came from, but that is a starting point for a conversation, not a substitute for confirming the actual requirement. A UNS number does not name the form or condition; see how to read the UNS callout.

Frequently asked questions

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