Incoloy 825 and Hastelloy C‑276, both nickel alloy forgings under ASTM B564, differ sharply in alloy design and corrosion scope. Incoloy 825 focuses on moderate acid and chloride stress corrosion, while Hastelloy C‑276 delivers robust resistance to mixed oxidizing and reducing aggressive acids.
ASTM B564 is the standard specification for hot‑worked nickel alloy forgings. It governs chemical composition, mechanical property requirements, heat treatment rules and sampling inspection criteria for forged nickel‑based components used in corrosive industrial service, covering grades including Incoloy 825 (UNS N08825) and Hastelloy C‑276 (UNS N10276).
What is Incoloy 825 (UNS N08825)?
Incoloy 825 (UNS N08825) is a nickel‑iron‑chromium alloy with molybdenum and copper additions. It is formulated to withstand dilute sulfuric and phosphoric acids, as well as chloride‑induced stress corrosion cracking under medium temperature conditions. It balances reliable anti‑corrosion performance with a more economical cost profile, widely adopted in pickling equipment, pipelines and offshore seawater processing units.
What is Hastelloy C‑276 (UNS N10276)?
Hastelloy C‑276 (UNS N10276) is a nickel‑molybdenum‑chromium alloy containing tungsten. It is engineered to resist severe corrosion from a broad spectrum of aggressive media, including strong oxidizing and reducing acids. It maintains stable performance in harsh mixed‑acid environments and high‑corrosion chemical processes, commonly specified for chemical reactors, flue gas desulfurization and hazardous waste treatment facilities.
Request a Combined B564 Quotation for 825 and C-276
Incoloy 825 vs Hastelloy C276: Chemical Composition Comparison
The compositional gap between these alloys defines their divergent corrosion profiles. C-276 contains 15–17% molybdenum and 3–4.5% tungsten - elements absent or minimal in 825. Incoloy 825 contains 1.5–3.0% copper for sulfuric acid resistance - an element not present in C-276.
| Element (wt%) | Incoloy 825 (N08825) | Hastelloy C-276 (N10276) | Key Difference |
|---|---|---|---|
| Ni | 38.0–46.0 | Balance | C-276 is full-nickel matrix; 825 is Ni-Fe matrix |
| Cr | 19.5–23.5 | 14.5–16.5 | 825 has higher Cr for oxidizing acid passivation |
| Mo | 2.5–3.5 | 15.0–17.0 | C-276 Mo is 5× higher - drives pitting/crevice resistance |
| W | - | 3.0–4.5 | Tungsten unique to C-276; synergizes with Mo |
| Cu | 1.5–3.0 | - | Copper unique to 825; enhances H&sub2;SO&sub4; resistance |
| Fe | ≥22.0 | 4.0–7.0 | 825 is a Ni-Fe alloy; C-276 is a Ni-based alloy |
| C | ≤0.05 | ≤0.01 | C-276 ultra-low C prevents weld HAZ sensitization |
| Co | - | ≤2.5 | Residual in C-276 |
Incoloy 825 vs Hastelloy C276: Mechanical Properties Comparison
Both alloys are delivered under ASTM B564 in the solution-annealed condition. C-276's higher nickel and molybdenum content produces a higher-strength matrix. Incoloy 825's iron content reduces density and strength but lowers raw material cost.
| Property | Incoloy 825 (N08825) | Hastelloy C-276 (N10276) |
|---|---|---|
| Tensile Strength, min (MPa) | 586 | 690 |
| Yield Strength 0.2%, min (MPa) | 241 | 283 |
| Elongation in 50 mm, min (%) | 30 | 40 |
| Density (g/cm³) | 8.14 | 8.89 |
| Melting Range (°C) | 1370–1400 | 1323–1371 |
| Solution Anneal Temp (°C) | 1095–1200 | 1121–1177 |
Incoloy 825 vs Hastelloy C276: Corrosion Resistance Comparison
Incoloy 825 (UNS N08825) and Hastelloy C‑276 (UNS N10276) show distinct corrosion limits in industrial media. In 20% sulfuric acid at 80°C, Incoloy 825 corrosion rate sits below 0.1 mm/y; its performance drops sharply in concentrated oxidising acids. It tolerates chloride stress corrosion cracking in seawater and dilute acid systems.
Hastelloy C‑276 retains a corrosion rate under 0.1 mm/y in mixed 20% sulfuric + oxidising ferric ions at 80°C. It resists pitting and crevice corrosion at higher chloride concentrations and handles both oxidising and reducing acid mixtures, environments where Incoloy 825 suffers rapid material loss.
| Medium & Condition | Incoloy 825 (UNS N08825) | Hastelloy C‑276 (UNS N10276) |
|---|---|---|
| 20% H₂SO₄, 80°C | Corrosion rate ＜0.1 mm/y | Corrosion rate ＜0.05 mm/y |
| 20% H₂SO₄ + Fe³⁺, 80°C | ＞1.0 mm/y, rapid attack | ＜0.1 mm/y |
| Chloride SSC (seawater, 60°C) | Resistant to SSC, susceptible to crevice pitting at high Cl⁻ | High pitting resistance, low crevice corrosion tendency |
| Mixed oxidising + reducing acids | Not suitable | Acceptable for continuous service |
Incoloy 825 vs Hastelloy C276: Temperature Capability Comparison
Incoloy 825 and Hastelloy C‑276 have different continuous and peak service temperature limits, determined by alloy composition and thermal stability. Incoloy 825 is suitable for continuous operation up to 540°C; above this temperature, long‑term exposure leads to sigma phase precipitation and reduced ductility.
Hastelloy C‑276 supports continuous service up to 650°C. At temperatures exceeding 700°C, C‑276 faces grain boundary precipitation of intermetallic phases, shortening service life. Neither grade is designed for sustained load-bearing use above their temperature thresholds.
| Parameter | Incoloy 825 (UNS N08825) | Hastelloy C‑276 (UNS N10276) |
|---|---|---|
| Max continuous service temperature | 540°C | 650°C |
| Temperature range for sigma phase risk | >540°C, prolonged holding | 600–950°C, long exposure |
| Short‑term peak temperature | 600°C | 700°C |
| Main high‑temperature risk | Sigma embrittlement | Molybdenum-rich intermetallic precipitation |
Incoloy 825 vs Hastelloy C276: Weldability Comparison
Both alloys can be welded with GTAW, GMAW and SMAW processes, yet they require different filler metals and post‑weld controls. Incoloy 825 uses matching 825 filler; it does not require post‑weld heat treatment after welding. Hastelloy C‑276 must use C‑276 filler metal to preserve corrosion resistance; uncontrolled heat input raises susceptibility to intergranular corrosion. Both materials need low heat input to limit grain coarsening. Welds of C‑276 retain corrosion resistance without solution annealing, but heat input must be kept below 1.5 kJ/mm.
| Parameter | Incoloy 825 (UNS N08825) | Hastelloy C‑276 (UNS N10276) |
|---|---|---|
| Recommended welding processes | GTAW, GMAW, SMAW | GTAW, GMAW, SMAW |
| Matching filler metal | ERNiFeCr‑1 | ERNiCrMo‑4 |
| Mandatory post-weld heat treatment | Not required | Not required for standard service |
| Heat input limit | <2.0 kJ/mm | <1.5 kJ/mm |
| Primary welding risk | Grain growth at excessive heat input | Intergranular corrosion from high heat input |
The skilled worker is performing the welding process.
Incoloy 825 vs Hastelloy C276: Cost Comparison
| Cost Factor | Incoloy 825 | Hastelloy C-276 |
|---|---|---|
| Relative price index (825 = 1.0) | 1.0 | 2.5–3.5 |
| Key cost drivers | Ni 38–46%, Mo 2.5–3.5%, Cu 1.5–3% | Ni balance, Mo 15–17%, W 3–4.5% |
| Density impact on cost/kg | 8.14 g/cm³ (lower material mass) | 8.89 g/cm³ (+9.2% mass per same volume) |
For reference only, subject to final technical confirmation. Prices fluctuate with Ni/Mo/W raw material indices.
At the same dimensions, C-276 forging weighs 9.2% more than 825 due to density difference (8.89 vs 8.14 g/cm³). Combined with the 2.5–3.5× unit price premium, a C-276 component at identical geometry costs approximately 2.7–3.8 times more than the 825 equivalent. For projects requiring both alloys, provide the full BOM with mixed material lines to our technical team for a consolidated quotation - combined orders reduce logistics, documentation, and inspection overhead per kilogram.
Incoloy 825 vs Hastelloy C276: Application Decision Matrix
| Service Scenario | Recommended | Justification |
|---|---|---|
| H&sub2;SO&sub4; transport piping, 40–80°C | 825 | Cu content provides sufficient resistance; C-276 is over-specified |
| HCl processing >10%, 25°C | C-276 | 15–17% Mo required; 825 corrosion rate 8.8× higher |
| FGD scrubber internals | C-276 | Mixed SO&sub2;/Cl− requires PREN >60 |
| Sour gas valve internals, H&sub2;S <10 bar | 825 | NACE MR0175 qualified; cost-effective |
| Subsea manifold, sour + Cl− | C-276 | PREN 66 + NACE MR0175 + high Cl− |
| Phosphoric acid reactor, 80°C | 825 | Cu + Cr sufficient; C-276 unnecessary |
Why Choose Us as Your Supplier Partner?
- Order flexibility: From 10 kg mixed-alloy forging sets to 20-ton bulk pipe orders - same quality control protocol, same MTC standard, same traceability.
- Dual-material consolidation: Combined PO for Incoloy 825 + Hastelloy C-276 + Inconel 625 under one inspection and documentation package, reducing lead time and procurement overhead.
- Full NDT capability: PMI per ASTM E1621, UT per ASTM E213, hardness per ASTM E18, hydrostatic per ASTM E1003 - all in-house.
- Material certification: EN 10204 3.1/3.2 MTC with heat number traceability from VIM+ESR melt to finished forging. NACE MR0175 compliance verification per lot.
- Custom processing: Forging, machining, drilling, threading, solution annealing, and surface finishing per ASTM B564 dimensional requirements.
- Export packaging: VCI rust-inhibitor wrapping, seaworthy wooden cases with steel banding, heat-number marking per piece.
- Technical support: Metallurgical engineers available for specification verification, standard selection, and welding procedure recommendations.
FAQ
Q: What is the equivalent material for Hastelloy C-276?
A: UNS N10276, DIN/W.Nr. 2.4819 (NiMo16Cr15W), EN NiMo16Cr15W. ASTM standards: B564 (forgings), B575 (plate), B574 (bar), B619 (welded pipe), B622 (seamless pipe).
Q: What is the equivalent material for Incoloy 825?
A: UNS N08825, DIN/W.Nr. 2.4858 (NiCr21Mo), EN NiCr21Mo. ASTM standards: B564 (forgings), B423 (seamless pipe), B424 (plate), B425 (bar), B163 (heat exchanger tube).
Q: Can Incoloy 825 replace Hastelloy C-276?
A: Only in moderate corrosion environments. 825 has PREN 29 vs C-276's 66. In HCl above 5%, high-chloride pitting service, or FGD scrubbers, 825 will fail. In H&sub2;SO&sub4; transport at moderate temperature or sour gas with low H&sub2;S partial pressure, 825 is a cost-effective substitute.
Q: Why does C-276 cost 3 times more than 825?
A: C-276 contains 15–17% molybdenum (vs 2.5–3.5% in 825) and 3–4.5% tungsten (absent in 825). Molybdenum and tungsten raw materials are among the most expensive alloying elements. C-276 is also a full-nickel matrix (balance Ni) vs 825's Ni-Fe matrix (22% Fe), further increasing raw material cost.
Q: Can both alloys be ordered under ASTM B564 in one purchase order?
A: Yes. B564 covers nickel alloy forgings for both UNS N08825 and N10276. A combined PO with separate heat numbers, separate solution-anneal records, and separate MTCs per material is standard practice. Our production schedule supports dual-material consolidation to reduce lead time and documentation overhead.
