HTS Coatings — machining & grinding

Hastelloy C-276

15% Cr, 5% Fe, 16% Mo, 3% W, Ni-balance

  • Arc
  • HVOF

Hastelloy C-276 is a corrosion-first coating — not a wear coating. That distinction matters, because it's the most common reason spec sheets get misread. At 250-400 HV as-sprayed, C-276 won't save a ball valve from galling or a pump impeller from slurry erosion. What it will do is keep chloride, hypochlorite, wet chlorine, dilute sulfuric, HCl above 5%, and sour H₂S/Cl⁻/CO₂ streams from eating the base metal.

The chemistry is Haynes's classic Ni-Mo-Cr-W recipe: Ni balance, 16% Cr, 16% Mo, 4% W, ultra-low carbon and silicon. Wrought C-276 carries a PREN of 65-70 and a 150°C critical pitting temperature in ferric chloride — among the best all-around nickel-base alloys for mixed-acid and high-halide service. As a thermal-sprayed coating, it brings that same alloy to refurbishment work where solid construction isn't practical.

We apply it three ways: twin-wire arc for fast, thick vessel and scrubber linings (sealed for chloride duty); HVOF for dense sub-1% porosity coatings on pumps, valves, and heat-exchanger parts; and HVAF when porosity is the failure mode to beat. Typical work: FGD stacks, chlor-alkali gear, pulp-mill bleach plants, phosphoric-acid evaporators, pharmaceutical reactors, sour-service oilfield parts.

Got a vessel pitting out, or a sour-gas component you'd rather refurbish than replace? Send us the part and the process conditions — we'll tell you if C-276 is the right call.

Technical data

Hardness
250-400 HV typical as-sprayed (HVOF ~300-350 HV0.2 measured on production coatings; research builds reach ~329 HV0.2)
Hardness (HRC)
~28-30 HRC as-sprayed HVAF/HVOF — this is a soft, corrosion-first alloy, not a wear coating
Bond strength
HVOF/HVAF >10,000-12,000 psi (>70-80 MPa) to carbon steel; arc-sprayed wire typically 5,000-8,000 psi (35-55 MPa)
Max service temp
Continuous oxidation resistance to ~1,900°F (1,038°C); ASME Section VIII wrought service limit 1,250°F (677°C); most aqueous-corrosion duty below 650°F
Max service temp
~1,040°C oxidation limit; ~677°C ASME design; aqueous service typically <340°C
As-sprayed porosity
HVOF/HVAF <1% (gas-shrouded HVOF reports near-zero through-porosity); twin-wire arc spray 3-8% (open porosity must be sealed for chloride service)
Typical thickness
Arc spray 10-40; HVOF 5-20; HVAF up to 80 (2 mm) in a single setup
Melting range
2415-2500°F (1323-1371°C)
Density
8.89

Where it earns its keep

  • Exceptional resistance to localized corrosion — pitting, crevice, and chloride stress-corrosion cracking in both oxidizing and reducing environments where 316L and 625 fail
  • Handles high-chloride aqueous service including wet chlorine gas, hypochlorite, and chlorine dioxide — one of the few alloys that will
  • NACE MR0175 / ISO 15156 qualified for sour service; resists sulfide stress cracking in H₂S/Cl⁻/CO₂ oilfield environments
  • Wide acid compatibility — HCl above 5%, dilute-to-moderate H₂SO₄, phosphoric to 65%, and mixed-acid pickling streams where single-alloy choices run out
  • Available across the spray stack: twin-wire arc for fast, thick vessel linings; HVOF for dense, low-porosity production coatings; HVAF for near-zero porosity up to 2 mm single-setup builds

Where it doesn't

  • This is a corrosion-first coating, not a wear coating. At 250-400 HV it will not survive 3-body abrasion, valve-seat galling, or erosive slurry — pick WC-CoCr or Stellite when the duty is mechanical wear
  • Arc-sprayed C-276 runs 3-8% open porosity — chloride and acid services require a sealer (epoxy, phenolic, or fluoropolymer) or a dense HVOF/HVAF overlay to prevent through-thickness ingress
  • Premium Ni-Mo-W chemistry carries premium raw-material cost; wrought C-276 cladding or solid construction is often preferred where geometry allows — thermal spray shines for refurbishment and localized upgrade

Typical applications

  • Wet scrubber internals and FGD (flue-gas desulfurization) stack liners, ducts, dampers, and reheaters
  • Chlor-alkali plant components — wet chlorine gas, hypochlorite, and chlorine dioxide service
  • Pulp & paper bleach-plant chlorination stages, digesters, and D-stage equipment
  • Pharmaceutical reactors, heat exchangers, and piping exposed to mixed acids and halides
  • Hydrochloric-acid service piping, pumps, and vessel linings above 5% concentration
  • Sour-gas oilfield components — Christmas trees, wellhead parts, and downhole tooling in H₂S/Cl⁻/CO₂
  • Phosphoric-acid plant evaporators, heat exchangers, and transfer piping
  • Industrial and municipal waste-treatment reactors, incinerator scrubbers, and amine contactor walls
  • Sulfuric-acid handling equipment and sulfur-removal towers in refineries

Wear modes addressed

  • Pitting corrosion in oxidizing chloride media
  • Crevice corrosion under deposits, gaskets, and weld heat-affected zones
  • Stress-corrosion cracking (SCC) in chloride-bearing solutions
  • Sulfide stress cracking (SSC) in sour H₂S service
  • Erosion-corrosion in flashing acid streams and abrasive slurries
  • General uniform corrosion in reducing acids (HCl, H₂SO₄) at elevated concentration and temperature

Industries

  • Chemical and petrochemical process
  • Pulp & paper (bleach plants, recovery boilers)
  • Oil & gas (sour service, upstream and midstream)
  • Pharmaceutical and fine chemicals
  • Power generation (FGD, waste-to-energy boiler waterwalls)
  • Pollution control and air-quality equipment
  • Fertilizer and phosphoric-acid production
  • Waste treatment and incineration

Substrates

  • Carbon and low-alloy steels (A106, A516, 4130, 4140)
  • Austenitic stainless steels (304, 316, 316L) — common refurbishment substrate
  • Duplex and super-duplex stainless steels
  • Ni-base alloys (Alloy 600, 625) for upgrade or repair service
  • Cast iron vessel components (with suitable prep and bond coat)

Which process, when?

Twin-wire arc spray (TWAS) lays down thick C-276 linings fast and on-site: vessel interiors, scrubber walls, duct repairs at 10-40 mils, bonded around 5,000-8,000 psi. Porosity runs 3-8%, so chloride and acid duty almost always requires a sealer or a dense topcoat. HVOF is the production default for components that can come to the shop — pumps, valves, heat-exchanger components, small vessels. Sub-1% porosity, >10,000 psi bond, dense enough for aggressive aqueous service with minimal sealing. HVAF goes further: near-zero porosity, thicker single-setup builds up to 2 mm, and less in-flight oxidation than HVOF, which matters when the service is hot acid or wet chlorine. Pick arc spray for reach-and-coverage refurbishment, HVOF for precise production components, HVAF when porosity and oxidation are the failure modes to beat.

Sources

Data points on this page draw on the following published references. Nothing here replaces a material-specific review by our process engineers — but it's the working starting point.

Material data on this page is provided as a general reference and can vary by lot, substrate, and application. Contact HTS to confirm the right material and specification for your specific part.

Thinking about Hastelloy C-276 for a part?

Send us the spec or a photo. We'll tell you whether this fits, or point you at a better material for the job.

Ask about this material