Inconel 625 vs Hastelloy C-276
Both are premium nickel alloys for extreme environments — but they are optimized for different types of corrosion. C-276 dominates in reducing acids; 625 excels at high-temperature oxidation and strength.
| Propiedad | Inconel 625 | Hastelloy C-276 |
|---|---|---|
| UNS | N06625 | N10276 |
| Nickel | ≥ 58.0% | ≥ 57.0% |
| Chromium | 20.0 – 23.0% | 14.5 – 16.5% |
| Molybdenum | 8.0 – 10.0% | 15.0 – 17.0% |
| Tungsten | — | 3.0 – 4.5% |
| Niobium | 3.15 – 4.15% | — |
| Tensile Strength | ≥ 827 MPa (120 ksi) | ≥ 690 MPa (100 ksi) |
| Yield Strength | ≥ 414 MPa (60 ksi) | ≥ 283 MPa (41 ksi) |
| Max Service Temp | 980°C | 1093°C |
| PREN | > 45 | > 65 |
| Oxidizing Resistance | Very good | Good (C-22 better for oxidizing) |
| Reducing Resistance | Good | Excellent (best in class) |
| Weldability | Excellent | Very good |
| Relative Cost | 1.0× (base) | 1.15 – 1.25× |
Elegir Inconel 625 Cuando:
- High-temperature strength required (> 650°C)
- Aerospace and gas turbine components
- Subsea umbilicals and control lines
- Oxidizing environments (nitric acid, wet chlorine)
- NACE sour service with mechanical loads
Choose Hastelloy C-276 When:
- Hot HCl, H₂SO₄, or mixed acids
- Wet chlorine gas and hypochlorite
- Flue gas desulfurization (FGD) scrubbers
- Chemical reactors with unpredictable process streams
- Reducing environments (the universal solvent)
Conclusion
625 is an engineer's alloy — optimized for strength, fatigue resistance, and high-temperature oxidation with good general corrosion resistance. C-276 is a chemist's alloy — optimized for universal corrosion resistance including the most aggressive reducing acids. For chemical processing with unknown or variable process streams, C-276 is the safer choice. For mechanical components that happen to need corrosion resistance, 625 is stronger and more fatigue-resistant.
Preguntas Frecuentes
Inconel 625 vs Hastelloy C-276: which has better corrosion resistance?
Hastelloy C-276 (N10276) excels in reducing environments — it resists HCl across a wide concentration and temperature range and handles reducing H2SO4, phosphoric acid, and wet chlorine better than 625. Inconel 625 (N06625) is stronger in oxidizing conditions, seawater, and pitting or crevice attack thanks to high Mo plus Nb. C-276's near-zero C and Si minimize carbide and mu-phase precipitation, aiding weld-zone corrosion resistance. Choose C-276 for aggressive reducing acids; choose 625 for seawater, sour or oxidizing service, and where high strength is needed. TOKO TECH stocks both in pipe, tube, and fittings.
How do the high-temperature limits of 625 and C-276 compare?
Inconel 625 (N06625) outperforms C-276 at high temperature: it retains useful strength to about 980°C (1800°F) and resists oxidation and scaling thanks to its Nb-strengthened matrix, making it a go-to for flue-gas, furnace, and exhaust systems. Hastelloy C-276 (N10276) is serviceable to about 650–705°C (1200–1300°F) but is not a high-temperature structural alloy; above this it loses strength and can form deleterious phases. For combined heat and corrosion, 625 usually wins. TOKO TECH supplies both with NACE and ISO test reports for high-temperature and CPI applications.
Which alloy is mechanically stronger, 625 or C-276?
Inconel 625 (N06625) is the stronger alloy: typical annealed yield is about 414 MPa (60 ksi) and tensile about 830 MPa (120 ksi), boosted by Nb and Mo solid-solution strengthening, with excellent fatigue and cryogenic toughness. Hastelloy C-276 (N10276) is also strong (yield about 283–310 MPa, tensile about 790 MPa) but softer and more formable. For pressure-bearing components at high stress or cyclic load, 625 offers larger margins. TOKO TECH provides certified mechanicals (EN 10204 3.1) so designers can confirm margin against ASME Section II and VIII allowable stresses.
What is the cost premium and when does each alloy win?
Both are premium nickel alloys costing several times 316L. C-276 typically carries a higher mill premium than 625 in bar and plate, while 625 pipe and tube pricing is often comparable or slightly higher depending on form. Choose C-276 for severe reducing-acid service (HCl, reducing H2SO4, mixed acids, FGD). Choose 625 for seawater and offshore, aerospace, high-temperature, and high-strength needs. TOKO TECH helps buyers pick the lowest-cost alloy that meets the corrosion envelope, avoiding over-specification.
For HCl and H2SO4 service, which alloy should I choose?
For hydrochloric acid (HCl), Hastelloy C-276 (N10276) is the stronger choice, resisting HCl at most concentrations and temperatures where 625 would pit. For sulfuric acid (H2SO4) it depends: C-276 dominates the reducing regime and moderate concentrations; Inconel 625 (N06625) holds up better in oxidizing or aerated H2SO4 and in chloride-contaminated acid. Neither beats glass-lined or purpose-built alloys at extreme conditions. TOKO TECH reviews your acid concentration, temperature, and contaminants to specify C-276 versus 625 and confirms with ASTM G28 intergranular testing.
How do 625 and C-276 compare for pitting and crevice resistance?
Inconel 625 (N06625) has a PREN around 49–54 (Cr about 21.5%, Mo about 9%, Nb about 3.6%), giving excellent pitting and crevice resistance. Hastelloy C-276 (N10276) PREN is similarly high (about 62 due to very high Mo, around 16%), so both resist chloride pitting strongly. In chloride-rich seawater, 625 is the more common offshore choice; in hot acidic chlorides, C-276 edges ahead. TOKO TECH stocks both as pipe, tube, and flanges with PMI verification of Cr, Mo, and Nb chemistry.