Alloy C-276

Identity and procurement

Haynes reports a critical pitting temperature above 150°C and a critical crevice temperature of 55°C for C-276 in acidified 6 wt.% ferric chloride under its 72-hour ASTM G48 procedures. The two test endpoints describe different attack mechanisms. Evaluate the actual liquid, crevice geometry and exposure before setting an operating limit. Haynes pitting and crevice test results

Alloy C-276 is the nickel-chromium-molybdenum alloy UNS N10276. HASTELLOY identifies Haynes's trademarked product; VDM Alloy C-276 is another producer's product designation. A generic C-276 description establishes neither producer provenance nor a particular delivery specification. Haynes C-276 brochure · VDM product identity

A useful order includes the designation, product standard and edition, supplied form, dimensions, condition, surface requirements and inspection documentation. Keep wrought stock, filler metal and a completed welded component separate in the material record. A shared alloy label cannot establish identical acceptance requirements for each.

Composition and condition

VDM's composition table identifies 15–16.5% chromium, 15–17% molybdenum and 3–4.5% tungsten, with carbon ≤0.01% and silicon ≤0.08%, by mass. Use the complete specified composition and actual heat analysis when accepting material; selected major-element percentages alone cannot establish conformance. VDM data sheet, Table 2

Mechanical values are form-specific

VDM's solution-annealed room-temperature entries below are scoped to the stated forms and dimensions. The sheet relates these values to VdTÜV Materials Sheet 400; dimensions outside its scope need agreement. VDM mechanical-properties section, Table 5

The table labels elongation as A. Confirm the specimen and gauge-length basis in the governing specification rather than silently relabeling it A5 or A50. These are supplier-document entries, not a substitute for checking the actual order and certificate.

Haynes separately reports room-temperature characterization of solution-annealed, 25.4 mm plate: 365 MPa 0.2%-offset yield strength, 785 MPa tensile strength and 59% elongation. Its disclaimer says the disclosed test results are indicative and should not be treated as guaranteed minima or maxima. Do not combine this result with VDM's minimum-value table to invent a common specification. Haynes brochure, tensile table and disclaimer

Calculated mass illustration: VDM gives density 8.9 g/cm³ at 20°C. A solid 100 × 100 × 10 mm blank has volume 100 cm³ and estimated mass 890 g, or 0.890 kg. This assumes nominal solid geometry and the listed density; it is not a delivered-weight tolerance. VDM physical properties

Corrosion evidence needs its test environment

Haynes describes strong resistance across several chemical environments, but its comparative data also distinguish pitting from crevice attack. In acidified 6 wt.% ferric chloride, under the stated 72-hour ASTM G48 procedures, it reports C-276 critical pitting temperature >150°C and critical crevice temperature 55°C. These are laboratory-test results, not allowable operating temperatures for arbitrary chloride solutions. Haynes brochure, resistance to pitting and crevice corrosion

Crevices at flanges, deposits and stagnant pockets need their own exposure assessment.

Include cleaning, startup, shutdown and upset conditions in the service description. Establish the acceptable corrosion rate or localized-attack criterion before selecting test evidence. Where published results do not match the actual duty, seek producer advice and qualify representative material, welds and joint details. Do not transfer a result between different test solutions or treat a blank table entry as evidence of zero corrosion.

Thermal processing and fabrication

VDM warns that prolonged exposure or slow cooling through 600–1100°C can form intermetallic phases; grain-boundary precipitation can reduce intergranular-corrosion resistance. This describes a metallurgical risk, not a universal time–temperature service boundary. VDM microstructural-properties section

Plan heat treatment around the exact stock, deformation and finished requirements. Record the actual cycle and cooling route. Do not assume that a stress-relief step suitable for another alloy is harmless here, or that a hardness measurement proves restored corrosion performance.

Haynes identifies GMAW, GTAW and SMAW as applicable joining processes and lists matching welding-product classifications ERNiCrMo-4 and ENiCrMo-4. These identify available joining options, not qualification of a proposed joint. Haynes welding and specification tables

Develop the procedure for the actual joint, base-material combination, cleanliness, consumables, shielding and heat input. Review dissimilar-metal joints separately. Set acceptance for the weld and heat-affected region as well as the parent stock; a base-metal certificate cannot demonstrate the completed joint's performance in corrosive service.

For machining and forming, qualify tooling and parameters on the actual condition and geometry. Preserve material identity through cutting. Inspect dimensions and surface condition at the stage required by the drawing, and prevent fabrication contamination from invalidating the intended surface preparation.

Release and source versions

A release record should connect the heat/certificate, specified form and condition, drawing, fabrication route and final inspection. Review substitutions against all those requirements, including corrosion evidence and thermal history. Confirm code applicability through the current governing documents rather than treating a producer's historical code list as approval of the completed equipment.

The VDM PDF prints Material Data Sheet No. 4115, Revision 02, March 2022. The Haynes brochure prints H-2002H, ©2023, despite its 2024 upload path. Both PDFs were checked directly. Live product pages have no technical revision date used here. Sources reviewed 2026-11-01, America/Los_Angeles.

See grades, tempers and conditions.