Cast supealoyCobalt based alloyPrecision alloySUPER ALLOY
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Inconel 713C (IN-713C / K418)
1. Product Overview
Inconel 713C is a cast nickel-base superalloy developed by the International Nickel Company (INCO) in the 1950s, and is one of the representative early precipitation-hardening cast alloys.
Inconel 713C (often written IN-713C or Alloy 713C, corresponding to UNS N07713; the closest Chinese designation is K418 / K418B) is an equiaxed-cast nickel-base superalloy strengthened by precipitation of the gamma-prime (γ′) phase (Ni₃(Al,Ti)). It uses aluminum (about 5.5%–6.5%) as the main γ′-forming element, together with Nb and Mo for solid-solution strengthening and Cr for oxidation resistance; the volume fraction of the γ′ strengthening phase can reach ≈60%, and at 900 °C it still retains very high strength and creep resistance, with a long-term service temperature limit of about 900–980 °C.
Three key decision points for selection are: internal casting quality (porosity and shrinkage, usually improved by hot isostatic pressing, HIP), whether aerospace-grade standards and non-destructive testing levels apply (X-ray, fluorescent penetrant, ultrasonic), and whether delivery is to the US AMS 5391 or the Chinese GB/T 14992 K418. Note also that this alloy cannot be forged, rolled or drawn, has extremely poor weldability and is not suitable for welded structural components.
2. Chemical Composition (AMS 5391 System)
Inconel 713C chemical composition (AMS 5391 / US system, wt%, balance Ni)
Element | Range / max. | Element | Range / max. |
C | 0.08–0.20 | Cr | 12.0–14.0 |
Mo | 3.8–5.0 | Nb (Cb+Ta) | 1.8–2.5 |
Al | 5.5–6.5 | Ti | 0.50–1.00 (0.6–1.2 in some systems) |
B | 0.005–0.015 | Zr | 0.05–0.15 |
Fe | ≤1.0 (≤3.0 in some US standards) | Si | ≤0.50 |
Mn | ≤0.50 | Cu | ≤0.50 |
P | ≤0.015 | S | ≤0.015 |
Pb / Bi and other low-melting-point impurities | Controlled to trace levels | Ni | Balance |
3. Chemical Composition (K418 / GB System)
K418 chemical composition (GB / HB system, wt%, balance Ni)
Element | Range / max. | Element | Range / max. |
C | 0.08–0.16 | Cr | 11.5–13.5 |
Mo | 3.80–4.80 | Al | 5.50–6.40 |
Ti | 0.50–1.00 | Nb | 1.80–2.50 |
B | 0.008–0.020 | Zr | 0.06–0.15 |
Fe | ≤1.0 | Si | ≤0.50 |
Mn | ≤0.50 | P | ≤0.015 |
S | ≤0.010 | Ni | Balance |
Comparing the two systems, the GB grade K418 has slightly narrower ranges for the main elements and lower minimums (especially for chromium and molybdenum), a stricter iron limit (≤1.0 versus ≤3.0 in some US standards), and tighter control of phosphorus and sulfur. In practice the safest approach is to state "to GB/T 14992 K418 (or AMS 5391)" in the contract and the technical agreement, and to list the full set of elemental limits as an annex, so that mixing the two systems does not lead to acceptance disputes.
4. Grade Cross-Reference
Cross-reference of the main designations for Inconel 713C
Country / producer system | Equivalent designation | Notes on equivalence |
UNS | N07713 | Unified Numbering System code used for material identification and database lookup |
United States (original developer) | Inconel 713C / Alloy 713C / IN-713C | Original designation, most widely used in aerospace |
China | K418 (formerly K18), K418B | Approximate equivalent; K418B is an improved grade with tighter ranges for the main trace elements |
Germany | W.Nr. 2.4670 / 2.4671 | German material number, common on European drawings |
Common industry shorthand | 713C, IN713C, UNS N07713 | Short forms used in inquiries and on drawings |
5. List of Applicable Standards
Applicable standards commonly used for Inconel 713C / K418
Standard | Scope | Application notes |
AMS 5391H | Nickel-base cast superalloy (713C) ingot stock and castings | The most frequently cited US delivery standard; specifies composition, mechanical properties and heat treatment |
AMS 5390 / AMS 5381 | Related specifications for similar cast alloys | Cited where a specific product form or historical revision is required |
ASTM A494 | Nickel and nickel-alloy castings | General nickel-base casting standard, often used for industrial-grade castings |
SAE J467B | Related superalloy material specification | Widely cited in the automotive and power machinery sectors |
HB 5162 / HB 7728 / HB/Z 140 | Aviation cast superalloy standards and process guidance documents | Chinese aviation system; covers acceptance and process control requirements |
GJB 5512.1 | Military specification for cast superalloys | Mandatory for military products, usually with stricter NDT and batch inspection |
GB/T 14992 | Classification and designation of superalloys and high-temperature intermetallic materials | Chinese basis standard for grade designation and composition |
6. Key Performance Parameters
(1) Physical Properties
Table 3-1 Typical physical properties of Inconel 713C (reference values)
Property | Typical value | Property | Typical value |
Density | 8.0–8.01 g/cm³ | Melting range | 1260–1345 °C |
Solidus (typical) | ≈1295 °C | Liquidus (typical) | ≈1345 °C |
Thermal conductivity (100 °C) | ≈10.15–11.0 W/(m·K) | Specific heat capacity | ≈455 J/(kg·K) |
Electrical resistivity | ≈1.22 µΩ·m | Magnetism | Non-magnetic |
Coefficient of linear thermal expansion (20–100 °C) | 12.60×10⁻⁶ /°C | Coefficient of linear thermal expansion (20–1000 °C) | ≈13.8×10⁻⁶ /°C |
Elastic modulus | 197–211 GPa (144–211 in different sources) | γ′ phase volume fraction | ≈60% |
Crystal structure | Face-centered cubic γ matrix + γ′ precipitates | Maximum long-term service temperature | about 900–980 °C |
(2) Room-Temperature Mechanical Properties
Table 3-2 Room-temperature mechanical properties of Inconel 713C in the as-cast condition (typical values and standard requirements)
Property | Typical range | AMS 5391 requirement | Notes |
Tensile strength Rm | 900–1050 MPa | ≥758 MPa | Tested in the as-cast condition; varies with section thickness and cooling rate |
Yield strength Rp0.2 | 700–850 MPa | ≥690 MPa | Dominated by γ′ precipitation; meets the requirement in the as-cast condition |
Elongation A | 3%–10% | ≥3% | Low ductility is normal for cast alloys |
Hardness HRC | 30–42 (typical 33–37) | Per drawing or agreement | Coarse grains and segregation can cause locally higher hardness |
Hardness HB | 330–390 | Per drawing or agreement | Conversion from HB to HRC involves discrepancies; direct Rockwell testing is recommended. |
(3) Elevated-Temperature Tensile, Stress-Rupture and Creep Properties
Elevated-temperature tensile properties of Inconel 713C (reference values)
Test temperature | Tensile strength Rm | Yield strength Rp0.2 | Engineering significance |
540 °C | ≈1100 MPa | ≈850 MPa | Retains near-room-temperature strength in the mid-temperature range |
650 °C | ≈1050 MPa | ≈800 MPa | Typical service range for turbocharger turbine wheels |
760 °C | ≈950 MPa | ≈760 MPa | The γ′ phase is still stable, with no obvious softening |
870 °C | ≥760 MPa | ≥690 MPa | Typical qualification temperature for turbine blades |
982 °C | ≈345 MPa | ≈275 MPa | Suitable for short-term load carrying; oxidation must be assessed for long-term service |
Stress-rupture and creep properties of Inconel 713C (reference values)
Test temperature | Applied stress | Stress-rupture life requirement / typical result | Nature of data source |
750 °C | 608 MPa | ≥40 h | Typical stress-rupture qualification point |
800 °C | 490 MPa | ≥45 h | Typical stress-rupture qualification point |
850 °C | 100 MPa | >100 h | Long-term low-stress regime |
871 °C | 160 MPa | ≥100 h | Stress-rupture strength criterion |
982 °C | 152 MPa | ≥30 h | Short-term high-temperature load carrying |
Taken together, these data show a clear layering in the property envelope of 713C: between 650 and 760 °C it combines high strength with adequate ductility, making it an ideal operating window for turbocharger turbine wheels; from 850 to 900 °C strength becomes time-dominated rather than stress-dominated, so the design basis should shift to stress-rupture strength and creep limit; above 950 °C the limiting factor moves from mechanical properties to oxidation and microstructural stability, at which point higher-generation directionally solidified or single-crystal superalloys should be preferred.
7. Available Forms and Size Range
The available forms of 713C are rather special: as an alloy dedicated to casting, it is not supplied as conventional semi-finished bar or plate, but in two broad categories — "master alloy ingot for remelting" and "investment castings for direct use". This section describes the size ranges and supporting capabilities of each.
(1) Master Alloy Ingot
Typical supply sizes for master alloy ingot (actual availability confirmed at order)
Item | Typical range | Notes |
Diameter | Φ30–175 mm | Selected according to crucible capacity and furnace type |
Length | 250–1200 mm | Cut to length on request |
Melting method | Vacuum induction melting (VIM) | Vacuum refining or remelting can be added on request |
Surface condition | As-cast, turned, ground or peeled | Surface cleaning reduces inclusion carry-over during remelting |
Marking and traceability | Heat-number stamping + material certificate | Heat-number traceability is mandatory for aerospace use |
Packaging | Wooden case / pallet, moisture-proof and impact-protected | Protect both ends of the ingot from impact to avoid cracking |
(2) Investment Castings and Machined Parts
Typical investment casting product categories and support capabilities
Product category | Typical size / range | Supporting operations | Remarks |
Turbocharger turbine wheel | Per engine model; typical outside diameter 30–200 mm | Grinding, dynamic balancing, non-destructive testing | Largest volume; supplied as matched sets by model |
Turbine rotor blade | Airfoil length on the order of 20–200 mm | Tip grinding, pre-coating preparation | Internal cooling cavities available; requires ceramic cores |
Nozzle vane / nozzle assembly | Per drawing | Dimensional inspection, flow-path gauge inspection | Tight tolerances on aerodynamic surfaces |
Integrally cast turbine wheel | Per drawing | Five-axis machining, dynamic balancing | Common in small power and auxiliary power units |
Ring-shaped parts | Outside diameter per drawing; wall thickness usually ≥3 mm | Turning, drilling, grinding | Nozzle rings, seal rings, mounting flanges |
Custom-shaped structural parts | Per drawing | Machining, deburring, surface treatment | Brackets, flanges, combustor components |
High-temperature tooling | Per drawing | Welded assembly (with caution) or integral casting | Furnace fixtures, trays, baskets |
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