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Nickel Superalloys

The hardest metals
we machine.
700 °C service. Sour wells.

Inconel 625 and 718, Hastelloy C-276, X-750 — nickel superalloys that retain strength where every other metal fails. Aerospace hot section, oil and gas sour service, nuclear, chemical processing. Expensive, slow to machine, but irreplaceable.

01 · Grades & variants

Nickel superalloys.

Four primary grades cover most industrial applications. The choice depends on temperature, corrosion environment, and whether precipitation hardening is needed.

Inconel 625

General · non-hardening

Solid-solution strengthened nickel alloy. Excellent corrosion resistance and moderate strength. Seawater, marine, aerospace exhaust, chemical processing. Not heat-treatable.

Inconel 718

Aerospace · aged

Precipitation-hardenable to 1,036 MPa yield. Retains strength to 700 °C. Aerospace hot section, rocket engines, turbine components. Most common aerospace superalloy.

Inconel X-750

High temp · spring

Similar to 718 but with elevated-temperature spring properties. Used for high-temperature aerospace springs, turbine bolts.

Hastelloy C-276

Chemical · corrosion

Molybdenum and tungsten additions. Best-in-class corrosion resistance to most acids including hot HCl. Chemical processing, scrubbers, FGD systems.

Hastelloy X

Aerospace · oxidation

Optimized for oxidation resistance at elevated temperatures. Gas turbine combustors, industrial furnace components.

Incoloy 825

Oil & gas sour

Balanced Ni-Fe-Cr-Mo alloy. Excellent stress corrosion cracking resistance. Oil and gas downhole tools, sour service components.

02 · Why this material

When superalloys are required.

Nickel superalloys are 4–8× the cost of stainless steel. Specify them only when the application genuinely requires their unique properties.

Elevated temperature strength

Retains useful strength to 700 °C (Inconel 718) where stainless and aluminum fail. Aerospace hot section, rocket engines.

Extreme corrosion resistance

Hastelloy C-276 resists hot concentrated HCl, HF, H2SO4 at temperatures where stainless dissolves.

Cryogenic toughness

Maintains strength and toughness to -253 °C (liquid hydrogen). Aerospace fuel systems, LNG processing.

Nuclear radiation resistance

Low cobalt variants (Inconel 725) resist radiation damage. Used in nuclear fuel assemblies and pressure vessels.

03 · Applications

Superalloy applications.

Aerospace hot section

Turbine blades, vanes, combustor liners — Inconel 718 DMLS + CNC finished

Rocket engine parts

Injector plates, nozzle sections, valve bodies — Inconel 718, 625

Oil & gas downhole

Sour-service tool bodies, packers — Inconel 718 (NACE-qualified)

Chemical reactors

Hastelloy C-276 vessels, agitators, heat exchangers for aggressive chemistry

Nuclear components

Fuel rod spacers, control mechanism parts — specialty grade variants

Desalination

Inconel 625 heat exchangers, evaporator tubing for seawater

Pollution control

Hastelloy scrubber internals, SO2 absorption hardware

Marine exhaust

Inconel 625 marine diesel exhaust, turbocharger housings

Industrial furnace

Hastelloy X combustion chambers, radiant tubes

04 · Finishing

Superalloy finishes.

As-machined

Ra 1.6–3.2 µm. Visible tool marks due to work hardening. Post-processing typically required.

Passivated

Nitric acid passivation similar to stainless. Enhances corrosion-resistant passive layer.

Bead blasted

Uniform matte finish. Common for cosmetic and pre-coating preparation.

Pickled

Acid pickling removes mill scale and heat treatment discoloration. Common on as-heat-treated parts.

Electropolished

Mirror-smooth electrochemical finish. Used for crevice-corrosion-critical applications.

Ground

Surface grinding to Ra 0.4 µm on critical bearing surfaces.

Shot peened

Compressive residual stress layer for fatigue improvement. Standard on aerospace rotating parts.

HIP + CNC

Hot isostatic pressing (through partner) before final CNC — densifies and improves fatigue.

FAQ

Inconel / Hastelloy questions.

Three factors: raw material cost (Inconel 718 billet is roughly $80–120/kg vs $8 for stainless), slow machining (cutting speed 20–30 m/min vs 150 for stainless — 5–8× longer cycle), and tool cost (carbide end mills last 30 minutes in Inconel vs 4 hours in stainless, with CBN tooling required for some operations). A typical finished Inconel part costs 8–15× the equivalent stainless part.
Inconel 625: use when corrosion resistance is the primary concern (seawater, chemical, marine exhaust). Not heat-treatable, moderate strength. Inconel 718: use when high strength and high-temperature service are required (aerospace hot section, rocket engines). Heat-treatable to very high strength, but less corrosion resistant than 625. For combined corrosion + high temperature, consider Inconel 725 or specialty alloys.
Yes — a growing aerospace workstream. DMLS prints complex Inconel 718 geometry (internal channels, topology-optimized brackets), then CNC machining finishes critical features (mounting holes, mating surfaces) to drawing tolerance. Combined printed + CNC workflow enables designs impossible via pure CNC. See our <a href="/metal-3d-printing.php">metal 3D printing page</a>.
Standard aerospace heat treatment: solution anneal at 980 °C, then double-aging at 720 °C + 620 °C to achieve 1,036 MPa yield strength. We perform heat treatment in-house for most Inconel work; critical aerospace heat treatments routed through AMS 2774-qualified partners for compliance. Full heat treatment records provided on aerospace orders.
Material availability drives lead time. Common grades (625, 718, C-276) typically in stock or 1–2 week lead time from mill. Specialty grades (X-750, 725, 925) may have 4–6 week mill lead times. Machining time for superalloys is typically 2–4× the equivalent stainless part due to slower cutting parameters. Typical complete order: 4–8 weeks for simple parts, 8–14 weeks for complex aerospace components.
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