Inconel 713C is cast, not forged: what that means for your drawing

713C is built around aluminium at 5.50–6.50% and a gamma-prime volume fraction that makes it un-forgeable. When the drawing says bar to AMS 5391 and the part is a turbine blade, the route is investment casting — and several notes on the drawing change with it.

Most enquiries for Inconel 713C start with the wrong question: what size bar can you cut? 713C does not arrive in that sense at all. Our data lists it as remelt stock and cast bar for investment casters, and states that it is not supplied as wrought bar, plate or tube. The part is created by casting, not by machining down from a rolled or forged section. The reason sits in the chemistry, and once a buyer accepts it, four or five lines on the drawing have to change with it.

The composition decides the process

Inconel 713C, UNS N07713 and DIN 2.4671, carries 66.4–76.3% nickel, 12.0–14.0% chromium, 3.80–5.20% molybdenum and 1.80–2.80% niobium. The aluminium is what marks it out. At 5.50–6.50% it is roughly ten times the 0.20–0.80% that Inconel 718 carries, and that is the whole design of the grade: it forms a high volume fraction of gamma-prime Ni3Al, which is where 713C gets its creep strength and also why it cannot be rolled or forged. A billet with that much gamma prime lacks the ductility a rolling schedule needs.

The rest of the specification follows. Titanium sits at 0.50–1.00%, carbon at 0.08–0.20%, zirconium at 0.05–0.15% and boron at 0.005–0.015% — trace levels that belong to a casting specification. Iron is held to 2.50% maximum and silicon to 0.50%. The delivery standard reflects the form: AMS 5391 covers remelt stock and cast bar, not plate or tube. When a drawing cites AMS 5391 and asks for a 120 mm round bar, the two halves disagree.

What the cast route gives, and what it takes away

What it gives is temperature. Density is 7.8–8.0 g/cm³ and the melting range 1260–1290 °C, but the useful number is the service ceiling: up to 982 °C. That ceiling is a surface property as much as a base-metal one. Chromium at 12.0–14.0% together with aluminium at 5.50–6.50% forms an alumina scale, and that scale is what carries the alloy to roughly 980 °C in oxidising service without a coating.

What it takes away is ductility and repairability. Elongation is typically 3–8%. That figure drives handling, proof testing and the machining sequence. The alloy is, in our own description, only poorly weldable, so a design that assumes weld repair of a rejected casting is a design that will scrap parts. There is no grain flow to lean on either: the directional properties of a forged bar are absent, and the casting process and section thickness set what the part actually does.

713C beside a wrought grade

The table below is the comparison a buyer makes when a part could be designed either way. These two grades are not substitutes, and the columns show why.

	Inconel 713C (cast)	Inconel 718 (wrought)
UNS	N07713	N07718
Europe	DIN 2.4671	DIN 2.4668
Delivery standard	AMS 5391 — remelt stock and cast bar	ASTM B637 — round bars
Nickel	66.4 – 76.3%	50.0 – 55.0%
Chromium	12.0 – 14.0%	17.0 – 21.0%
Molybdenum	3.80 – 5.20%	2.80 – 3.30%
Niobium	1.80 – 2.80%	4.75 – 5.50%
Aluminium	5.50 – 6.50%	0.20 – 0.80%
Titanium	0.50 – 1.00%	0.65 – 1.15%
Carbon	0.08 – 0.20%	≤ 0.08%
Iron	≤ 2.50%	11.1 – 22.5%
Density	7.8 – 8.0 g/cm³	8.19 g/cm³
Melting range	1260 – 1290 °C	1260 – 1336 °C
Service temperature	up to 982 °C	up to 700 °C

Read the aluminium and iron rows together. 718 carries 11.1–22.5% iron and far less aluminium, which is consistent with a grade supplied as round bar to ASTM B637, age-hardenable, described as easily weldable and rated to 700 °C. 713C trades all of that for 982 °C and a casting route. If the duty is 750 °C in a wrought part that must be welded and repaired, 713C is not an upgrade; it is a different manufacturing process with a different drawing.

Five notes that change when the drawing says 713C

• Form of supply. Write “remelt stock to our foundry’s specification” or “cast bar”. Do not carry bar, plate or tube language over from a wrought grade; the grade does not exist in those forms.
• Condition. Our data records 713C as as-cast, or as remelt stock to the foundry’s specification. There is no annealed or aged temper to call up in the way a wrought grade has one, so a drawing that specifies one was written for another alloy.
• Where the test comes from. Cast properties follow section. State whether the mechanical test is cut from an integrally cast coupon or from the part, and at what section.
• The elongation limit. With typical elongation of 3–8%, an acceptance figure borrowed from a wrought grade will reject sound castings. Set the limit against what the casting route can hold.
• Weld repair. Say explicitly whether repair welding is permitted, and to which procedure. The alloy is only poorly weldable, so silence here becomes a disagreement at final inspection.

Where 713C is the right answer, and where it is not

Our data lists equiaxed investment-cast turbine blades and vanes for jet engines; nozzles and wheels in industrial gas turbines where creep resistance matters more than ductility; diesel turbocharger turbine wheels; and press forging, extrusion and die-casting dies that see high temperature. 713C is the wrong answer for a wrought structural part, a thin-wall tube, a component that has to be field-welded, or oxidising service above its 982 °C ceiling without a coating. In those cases the conversation moves to a wrought grade, and the drawing is a different document.

What to send us

Send the casting drawing or the machined part drawing, the section thickness at the hottest point, the metal temperature — average and peak — and whether the part carries load. Tell us whether you need remelt stock for your own caster or cast bar for your own machining, and name the acceptance document: AMS 5391 or your foundry’s remelt specification. We will check the chemistry against the heat certificate and quote on hangbonickel.com; the mailbox is vicky@hangboalloy.com.

Values quoted here follow the ASTM / EN edition named in each paragraph. For a specific heat, the governing numbers are those printed on the EN 10204 certificate that ships with the material. Written by the technical desk at Shanghai Hangbo Alloy Group.