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Nickel Alloy

Inconel 625

Inconel 625 is a solid-solution-strengthened nickel-chromium-molybdenum superalloy with superb corrosion resistance and excellent weldability. Rated 5 for corrosion and good to 980 degrees C, it resists seawater, acids, and high-temperature oxidation. At 860 MPa tensile with 40% elongation it stays tough, but it work-hardens aggressively and is notoriously gummy and difficult to machine.

How Inconel 625 machines

Machinability is 1/5, among the hardest of all. 625 work-hardens rapidly and is gummy, so dwelling or rubbing instantly hardens the surface and destroys tools. Use very low SFM, sharp coated carbide, maximum rigidity, heavy positive feeds to cut beneath the hardened layer, and constant flood coolant; never let the tool pause in the cut.

Manufacturing & processing

625 is processed by CNC, forging, sheet metal, and 3D printing. It is solid-solution strengthened, so it gains strength from chemistry rather than age hardening, and is used in the annealed condition. Its excellent weldability without post-weld cracking makes it a favorite for fabricated piping, cladding, and additive components.

Typical applications

Best for seawater and high-temperature corrosion service. Typical uses include marine and subsea piping, chemical-process equipment, exhaust and combustion components, expansion bellows, heat-exchanger tubing, and weld overlay cladding where both corrosion and elevated-temperature resistance are required.

When to choose it

Choose 625 for combined corrosion and high-temperature service where excellent weldability matters, such as fabricated seawater or exhaust systems. If you need high strength rather than weldable corrosion resistance, age-hardenable 718 is the pick. For corrosion alone at lower cost, super-austenitic stainless may suffice.

Suitable surface finishes

Common finishes for Inconel 625: electropolishing, passivation. Use the finish selector →

FAQ

Why is Inconel 625 so hard to machine?
It work-hardens almost instantly and is gummy, so any dwelling or rubbing creates a hardened layer that wrecks tooling, earning a 1/5 rating. Success demands very low speeds, sharp rigid carbide tooling, heavy feeds, and continuous flood coolant with no pauses.
How is 625 strengthened compared to 718?
625 is solid-solution strengthened, gaining strength from its molybdenum and niobium in solution, and is used annealed. 718 is age-hardened to far higher strength. Choose 625 for weldable corrosion resistance and 718 when high strength is the goal.
Is Inconel 625 good for seawater service?
Yes, excellent. Its high molybdenum content and corrosion rating of 5 give strong resistance to seawater, pitting, and crevice corrosion, while its outstanding weldability makes it practical for large fabricated marine and subsea piping systems and components.

Property values are typical/nominal for early guidance and vary by temper, grade, supplier and heat treatment. Confirm critical specs against a certified datasheet or with an mfgiq engineer.