Inconel MIM — Metal Injection Molding of Nickel Superalloys
Quick Answer
Yes — Inconel can be metal injection molded, and for small complex superalloy parts it is often the only economical route. Inconel 718, 625, and IN713C are all processed by MIM for aerospace, turbine, and oil & gas components. The business case is simple: Inconel is one of the most difficult alloys to machine (severe work hardening, rapid tool wear, slow cutting speeds), so producing it near-net-shape eliminates its biggest cost driver. The trade-offs are fine-powder feedstock cost, strict atmosphere control during sintering (~1,260–1,300 °C in vacuum or high-purity hydrogen), and the need for HIP when fatigue-critical properties are required.
Emitech processes Inconel MIM parts for aerospace programs with HIP, NDT, and full traceability. Send your drawing for a manufacturability review.
Inconel Grades Available for MIM
| Grade | Key Alloying (approx.) | Strengthening | Continuous Service Temp | Typical MIM Applications |
|---|---|---|---|---|
| Inconel 718 (UNS N07718) | Ni bal., Cr 17–21%, Nb+Ta ~5%, Mo ~3%, Ti ~1%, Al ~0.5% | Precipitation (γ″) — age hardenable | ~700 °C | Brackets, fasteners, sensor housings, fuel system components, turbine hardware |
| Inconel 625 (UNS N06625) | Ni ≥58%, Cr 20–23%, Mo 8–10%, Nb ~3.5% | Solid solution — excellent corrosion resistance | ~650 °C (higher for oxidation) | Marine and chemical fittings, seals, oil & gas downhole components |
| IN713C (UNS N07713) | Ni bal., Cr ~12.5%, Mo ~4%, Al ~6%, Nb ~2%, Ti ~0.8% | High γ′ fraction — cast-grade creep strength | ~900 °C+ (load-dependent) | Small turbine vanes, turbocharger components — see IN713C MIM technology |
Other superalloys (Hastelloy, Rene-class, Fe50Co soft magnetics) are evaluated case by case — feedstock availability in MIM-grade powder is usually the deciding factor. For magnetic alloys, see Fe50Co MIM.
Why MIM Instead of Machining Inconel?
Inconel work-hardens aggressively. Cutting speeds run 5–10× slower than for carbon steel, tool life is short, and thin-walled or small features are prone to distortion and chatter. For a small, complex 718 bracket, machining can mean 30+ minutes of cycle time and 70% of an expensive forging or bar turned into chips. MIM inverts the economics:
- Near-net-shape: the part leaves sintering at final geometry; machining is limited to critical features (see MIM + CNC secondary operations)
- 95%+ material utilization — critical when alloy powder costs tens of dollars per kilogram
- Complexity is free: internal channels, thin ribs, and cross-holes add no cycle time
- Volume scaling: once tooled, hundreds of thousands of parts with consistent properties
Processing Challenges (and How They Are Solved)
Oxygen Sensitivity
718 and IN713C contain aluminum and titanium, which form stable oxides that block sintering necks and embrittle grain boundaries. Powder must be gas-atomized with low oxygen content, stored under inert conditions, and sintered in vacuum or high-purity dry hydrogen. This is the single biggest difference between MIM of Inconel and MIM of stainless steel.
High Sintering Temperature
Inconel 718 sinters at roughly 1,260–1,300 °C — near the practical limit of many furnaces and hard on furniture and setters. IN713C, being a cast chemistry with a high γ′ fraction, sits at the upper end of that range. Sintering cycles are longer, and atmosphere purity matters more than peak temperature.
Distortion Control
At these temperatures the compact is soft, and gravity plus friction can distort thin sections. Setter design and, where needed, ceramic supports are part of the DFM package — flag geometry risks early using the MIM design guide.
HIP for Fatigue-Critical Parts
As-sintered MIM reaches 95–98% density. For rotating or fatigue-critical aerospace hardware, hot isostatic pressing closes residual porosity to near-100%, dramatically improving fatigue life and elongation. HIP plus full solution-and-age heat treatment brings MIM 718 close to wrought performance.
Typical Properties of MIM Inconel 718
| Property | As-Sintered + Aged | HIP + Full Heat Treatment | Wrought 718 (reference) |
|---|---|---|---|
| Density | 95–98% | ~100% | 100% |
| Ultimate tensile strength | ~900–1,100 MPa | ~1,150–1,300 MPa | ~1,275 MPa |
| Yield strength (0.2%) | ~700–900 MPa | ~950–1,100 MPa | ~1,035 MPa |
| Elongation | 4–8% | 10–15% | ~12–15% |
Values are typical ranges from published MIM 718 data and production lots; guaranteed minimums are agreed per specification (AMS/MMPDS-style) during qualification.
Where Inconel MIM Parts Are Used
- Aerospace: brackets, clips, latches, sensor housings, actuator components — aerospace MIM parts
- Turbomachinery: small vanes, seal segments, and turbocharger hardware
- Oil & gas: downhole tool components, valve trim, corrosion-resistant fittings (625)
- Energy & industrial: fuel system components, high-temperature fasteners, burner hardware
Frequently Asked Questions
Q: Can Inconel 718 be metal injection molded?
Yes. Inconel 718 is one of the most established superalloys in MIM. It requires low-oxygen gas-atomized powder and vacuum or high-purity hydrogen sintering at ~1,260–1,300 °C. With HIP and full heat treatment, MIM 718 approaches wrought mechanical properties.
Q: Is MIM Inconel cheaper than machining?
At volume, almost always. Inconel's machining cost is driven by slow cutting speeds, short tool life, and high material waste. For small complex parts above ~10,000 pieces per year, MIM typically cuts total part cost by 40–70% compared with machining from solid.
Q: What is the difference between MIM 718 and MIM IN713C?
718 is a wrought-grade, age-hardenable alloy with good processability up to ~700 °C. IN713C is a cast-grade chemistry with a high γ′ fraction, offering superior creep strength above 850 °C but less ductility — it is the usual choice for small turbine vanes and turbocharger parts.
Q: Do MIM Inconel parts need HIP?
Not always. Static, non-fatigue-critical parts perform well as-sintered at 95–98% density. For rotating, vibrating, or flight-critical parts, HIP is strongly recommended — it closes residual porosity and roughly doubles fatigue life in most published comparisons.
Q: What size and tolerance can Inconel MIM achieve?
The same as other MIM alloys: parts typically under 100 g, walls from ~0.4 mm, and as-sintered tolerances of ±0.3–0.5%, with tighter features machined secondarily. See MIM size limitations and MIM tolerance.
Source Custom MIM Parts from Emitech
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