Hastelloy C276 CNC machining is slow, deliberate work, and it goes well only when the shop plans for it from the first toolpath. C276 is a nickel-molybdenum-chromium alloy with added tungsten, specified for its resistance to pitting, crevice corrosion and stress-corrosion cracking in chlorides, wet chlorine, hypochlorite and mixed acids. Wexmar machines C276 valve trim, pump components, fittings and instrument parts at our shop in Canastota, New York, on CNC lathes, horizontal machining centers and Swiss-type machines, with material certs and heat-lot traceability available on every order.
Machinability of Hastelloy C276
C276 carries an approximate machinability rating of 12 against AISI 1212 steel at 100, which places it among the toughest alloys we cut. It keeps its strength at temperature, conducts heat poorly and work hardens quickly, so heat stays at the tool tip instead of leaving with the chip. Typical carbide surface speeds are a fraction of what 316 stainless tolerates, and tool life is measured in parts, not hours. Cycle time and insert consumption are the main cost drivers, which is why C276 sits at the top of our cost index.
Tolerances and surface finish
On turned and milled C276 features we typically hold plus or minus 0.001 in. on diameters and bores and plus or minus 0.002 in. on general milled dimensions, with tighter bands reviewed drawing by drawing. A 63 Ra finish is routine, and 32 Ra is typical on turned sealing diameters with a fresh finishing insert and a steady feed. Because the alloy moves as machining stress is released, we rough, let the part settle, then finish critical features. Dimensions are verified on Brown and Sharpe CMMs with NIST-traceable calibration.
Tooling, work hardening and chip control
- Never dwell. A tool that rubs instead of cutting leaves a hardened skin that damages the next pass. Feeds stay positive and each depth of cut gets under the layer left by the previous one.
- Sharp, positive geometry. Honed but sharp PVD-coated carbide, and ceramic inserts for continuous roughing on larger diameters, keep cutting forces and heat down.
- High-pressure coolant. Through-tool or directed flood coolant pulls heat out of the zone and helps break the long, stringy chips C276 produces.
- Rigid setups. Pallet-changing horizontals with tombstone fixtures and short tool stick-out limit chatter, which in this alloy turns into notching and chipped edges fast.
- Burrs. C276 burrs are tough and tenacious, so edge breaks are programmed into the toolpath instead of left for hand deburring.
Heat treat and finishing
C276 is not hardenable by heat treatment. It is supplied solution annealed and is almost always used that way. When heavy cold work or welding calls for it, solution annealing and stress relief are arranged through qualified outside processors. Cleaning and passivation for corrosive service, and electropolishing when a smoother wetted surface is specified, are also handled through qualified outside processors. Most C276 parts ship bare, since the corrosion resistance comes from the alloy itself and not from a coating.
Common C276 parts and the right process
- Valve stems, seats, balls and trim for chemical processing (CNC lathes with live tooling)
- Pump shafts, sleeves and impeller hubs (lathes, then horizontal mills for keyways and flats)
- Instrument fittings, thermowell components and sensor housings (Swiss-type, up to 32 mm diameter)
- Flanges, manifold blocks and scrubber hardware (horizontal machining centers)
- Pins, studs and small fasteners for flue gas equipment (Swiss or lathe)
Round work goes to our CNC turning cells, where Y-axis and live tooling finish cross holes and flats in one chucking. Prismatic parts run on the horizontals, and small precision Hastelloy turned parts run on the Maier Swiss machines with bar feeders.
Cost index vs 6061 aluminum
| Material | Approx. machinability (1212 = 100) | Cost index vs 6061 | Notes |
|---|---|---|---|
| 6061-T6 aluminum | ~180 | 1.0 | Baseline |
| 316 stainless | ~36 | 2.5 | Lower-cost corrosion option |
| Monel 400 | ~20 | 5.0 | Seawater and hydrofluoric service |
| Inconel 625 | ~15 | 7.0 | Broad corrosion and heat resistance |
| Inconel 718 (annealed) | ~12 | 8.0 | High strength after aging |
| Hastelloy C276 | ~12 | 9.0 | Reducing and oxidizing acids, chlorides |
These values are typical and illustrative for a comparable part; actual quotes depend on geometry, quantity, tolerances and mill pricing. If your service conditions are marginal for C276, compare it with Inconel 625 machining, which often costs less and covers many of the same environments.
Applications and industries
C276 appears where other alloys give out: chemical and petrochemical processing, pulp and paper bleach plants, pollution control scrubbers, pharmaceutical process equipment, and pumps and valves handling sour or chloride-laden media. As a Hastelloy C276 machine shop in Central New York, we support pump and fluid power OEMs, instrumentation makers and defense build-to-print programs, with FAI reports in AS9102 format and DFARS-compliant specialty metals sourcing available. See the industries we serve.
Getting a quote
For Hastelloy C276 machining services, upload a drawing for an instant estimate or call (315) 400-2654. A human estimator confirms every quote before it is released, including bar and plate availability for C276.