Home / Glossary

Nickel Superalloy Machining Glossary

Terms that show up on an Inconel or nickel superalloy RFQ, in plain language. Where a full guide exists, the term links to it.

Material specs and certs

AMS specificationAerospace Material Specification, published by SAE International. Defines the exact composition, processing condition and mechanical property testing for a specific form of an alloy, such as bar or forging. "Inconel 718" alone does not say this; the AMS number does.
UNS numberUnified Numbering System code, such as N07718 for Inconel 718 or N06625 for Inconel 625. It identifies the alloy composition itself, independent of trade name, spec or supplier.
Mill certificateA document from the material producer stating the actual chemical composition and mechanical properties of a specific heat or lot of stock. A shop checks incoming material against it before cutting.
PMI testingPositive Material Identification. A handheld or lab test that confirms the actual composition of the bar or forging in hand, as a physical check against the mill certificate rather than trusting the paperwork alone.
Material Test Report (MTR)Another name for a mill certificate in some industries, particularly oil and gas. Lists the chemical and mechanical test results for the specific lot supplied.

SuperalloyA metal alloy that keeps useful strength and resists oxidation at a high fraction of its melting point. Inconel and Hastelloy are nickel-based superalloys. Monel and most Incoloy grades are corrosion-resistant nickel alloys but are not usually called superalloys, since they are not built primarily for extreme high-temperature strength.
Solid-solution strengtheningA way of hardening an alloy by dissolving other elements directly into the metal’s crystal structure, with no separate heat treatment step. Inconel 625 reaches most of its strength this way.
Age hardening (precipitation hardening)A heat treatment that forms fine particles inside an alloy after it is solution annealed, raising its strength significantly. Inconel 718 gets most of its strength this way, which is why the machining sequence around it matters.
Solution annealingA heat treatment step that dissolves alloying elements evenly through the material and leaves it in a softer, more machinable state, ahead of any later aging cycle.
Work hardeningA material getting harder as it is cut, because the cutting action itself deforms the surface. Nickel superalloys work-harden fast, which is why a light finishing pass can cut tougher than the rough pass before it.

FAI (First Article Inspection)A full dimensional and material check on the first part produced from a job, before the rest of the run continues. Common on aerospace and other regulated parts.
CMM (Coordinate Measuring Machine)An inspection machine that probes a part’s surfaces to measure dimensions against the drawing, used for tighter tolerances than manual gauging can confirm reliably.
ToleranceThe allowed variation from a stated dimension. On nickel superalloys, tolerance tighter than the part needs adds real machine time, not just inspection time, because of work hardening.
AS9100A quality management standard built on ISO 9001 for the aerospace industry, covering traceability, process control and documentation. A shop holding it is not the same as every part it makes meeting every aerospace requirement; check what the drawing actually calls for.

RFQ (Request for Quote)What a buyer sends to get pricing: drawing, alloy, quantity, tolerance and timeline. The more of this is specific up front, the fewer round trips it takes to get a real quote.
MOQ (Minimum Order Quantity)The smallest quantity a shop will accept for a given part or process. Less relevant on low-volume nickel superalloy work than on commodity parts, since setup and tooling cost usually dominate the price at low quantity anyway.
Lead timeThe time from order confirmation to delivery. On nickel superalloys this often depends more on raw material availability at the mill than on the machining itself.
NDA (Non-Disclosure Agreement)A signed agreement not to share a drawing or design outside the parties involved. Worth requesting on any part where the geometry itself is sensitive, before files go to a shop.