Incoloy® 825 Nickel-Iron-Chromium-Molybdenum Alloy Coil Tube
Product Overview
Incoloy® 825 (UNS N08825) is a high-performance nickel-iron-chromium-molybdenum-titanium alloy coil tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This alloy is specifically engineered to provide exceptional resistance to a wide range of corrosive environments, with outstanding performance in reducing acid solutions such as sulfuric acid (H₂SO₄) and phosphoric acid (H₃PO₄). The coil tube form factor offers superior flexibility in downstream fabrication, allowing for seamless bending, forming, and cutting operations with minimal material waste.
As a member of the Incoloy® superalloy family, Incoloy® 825 distinguishes itself through its dual resistance to both oxidizing and reducing acids, making it a critical material in aggressive chemical processing environments where conventional stainless steels fail. The addition of titanium (Ti) to the alloy matrix provides enhanced resistance to stress corrosion cracking (SCC) in chloride-containing environments.
Material Composition & Mechanical Properties
Chemical Composition (Wt.%)
| Element | Specification | Role in Alloy |
|---|---|---|
| Nickel (Ni) | Balance (min. 38%) | Primary matrix element; provides base corrosion resistance |
| Iron (Fe) | 22.0 – 25.0 | Contributes strength and cost-effectiveness |
| Chromium (Cr) | 22.0 – 25.0 | Provides oxidation resistance and passivity in oxidizing acids |
| Molybdenum (Mo) | 2.5 – 3.5 | Enhances resistance to pitting and crevice corrosion |
| Titanium (Ti) | 0.20 – 0.40 | Improves resistance to stress corrosion cracking |
| Carbon (C) | ≤ 0.08 | Controlled to prevent intergranular corrosion |
| Manganese (Mn) | ≤ 1.50 | Minor deoxidizer |
| Silicon (Si) | ≤ 0.30 | Minor deoxidizer |
| Sulfur (S) | ≤ 0.03 | Controlled to minimize hot shortness |
| Phosphorus (P) | ≤ 0.04 | Controlled impurity |
Mechanical Properties (Annealed Condition)
| Property | Value | Standard |
|---|---|---|
| Tensile Strength (UTS) | ≥ 550 MPa (80 ksi) | ASTM B409 |
| Yield Strength (0.2% offset) | ≥ 240 MPa (35 ksi) | ASTM B409 |
| Elongation | ≥ 35% | ASTM B409 |
| Density | 8.14 g/cm³ | — |
| Thermal Conductivity (20°C) | 11.4 W/m·K | — |
| Thermal Expansion (20–100°C) | 12.8 × 10⁻⁶ /K | — |
| Specific Heat (20°C) | 0.50 J/g·K | — |
| Modulus of Elasticity | 200 GPa | — |
Specifications
| Parameter | Specification |
|---|---|
| Product Form | Coil Tube (盘管) |
| Alloy Designation | Incoloy® 825 / UNS N08825 / W.Nr. 2.4858 |
| Alloy Family | Nickel-based Superalloy (Ni-Fe-Cr-Mo-Ti) |
| Outer Diameter Range | 6.0 – 168.0 mm |
| Wall Thickness Range | 0.5 – 12.0 mm |
| Coil Width / Length | Customizable per customer requirement |
| Surface Finish | Pickled & Passivated / Polished / Matte |
| End Condition | Plain / Beveled / Threaded |
| Applicable Standards | ASTM B409 / ASTM B564 / EN 10217-7 / JIS H7100 |
| Heat Treatment Condition | Solution Annealed (1050–1150°C, water quench) |
| Maximum Service Temperature | 1000°C (oxidizing) / 482°C (reducing acid) |
Manufacturing Process
The production of Incoloy® 825 coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage process to ensure metallurgical integrity and dimensional accuracy:
- Vacuum Arc Remelting (VAR): The alloy is produced via vacuum arc remelting to achieve homogeneous composition and minimize inclusions. The nickel-based melt is refined under high vacuum to remove interstitial elements (C, N, O) to specification limits.
- Hot Rolling & Forging: Billets are hot-rolled into flat stock or forged into ring blanks for seamless tube production. The rolling temperature is carefully controlled between 1050–1150°C to maintain proper grain structure.
- Piercing & Seamless Tube Forming: Ring blanks are pierced and drawn through a plug to form seamless tubes, ensuring no weld seams are present—critical for corrosion resistance in aggressive environments.
- Hot Resizing & Cold Drawing: Tubes are hot-resized to near-final dimensions, followed by cold drawing to achieve precise wall thickness and outer diameter tolerances.
- Solution Annealing: Tubes are solution-annealed at 1050–1150°C and rapidly quenched to dissolve carbide precipitates and restore full corrosion resistance.
- Pickling & Passivation: The final surface treatment removes scale and forms a protective chromium oxide passive film, essential for maintaining corrosion resistance in service.
- Coiling: Finished tubes are coiled to specified dimensions using precision coiling equipment to prevent deformation and surface damage.
Applications
Incoloy® 825 coil tubes are deployed in the most demanding corrosive environments across multiple industrial sectors:
Primary Applications:
- Acid Pickling Equipment: Incoloy® 825 is the industry-standard alloy for sulfuric acid (H₂SO₄) pickling tanks, spray nozzles, and heat exchangers in steel and titanium pickling operations. The alloy maintains structural integrity in hot concentrated sulfuric acid where 316L stainless steel rapidly fails.
- Hydrometallurgical Processing (Wet Metallurgy): Widely used in copper, nickel, and gold hydrometallurgical circuits, including leaching tanks, evaporators, and electrolyte piping. The alloy withstands mixed acid environments (H₂SO₄/HF, HCl/H₂SO₄) encountered in ore processing.
- Condensers & Heat Exchangers: Incoloy® 825 coil tubes are extensively used in shell-and-tube condensers and plate heat exchangers for acid service, particularly in sulfuric acid production, fertilizer manufacturing, and chemical synthesis plants.
Additional Applications:
- Phosphoric acid production equipment and purification systems
- Waste acid recovery and regeneration systems
- Semiconductor wet chemical processing equipment
- Marine heat exchangers in chloride-containing cooling water
- Environmental scrubbers and flue gas desulfurization (FGD) systems
- Pharmaceutical and food-grade processing equipment requiring acid resistance
Quality Certifications & Testing
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality assurance protocols for Incoloy® 825 coil tube production:
- ISO 9001:2015 — Quality Management System certification ensuring consistent production quality
- ISO 14001 — Environmental Management System certification
- EN 10204 3.1 — Material test certificates with third-party inspection
- ASTM B409 / B564 — Compliance with American Society for Testing and Materials standards for nickel alloy bars, rods, and wire
- NORSOK M-690 — Qualification for offshore and marine applications
- Third-Party Inspection (TPI): Available upon request by SGS, BV, or Lloyd's Register
Quality Control Testing Protocol:
| Test Method | Standard | Frequency |
|---|---|---|
| Chemical Composition Analysis | ASTM E415 (OES) / ASTM E1019 (ICP) | Every heat |
| Tensile Testing | ASTM E8 / ASTM E8M | Every heat |
| Hardness Testing | ASTM E92 (Rockwell B) | Every heat |
| Intergranular Corrosion Test | ASTM A923 Practice E | Every heat |
| Hydrostatic Pressure Test | ASTM A530 | 100% of tubes |
| Dimensional Inspection | ASTM B409 | 100% of tubes |
| Surface Examination | Visual + Eddy Current (ASTM E309) | 100% of tubes |
| Corrosion Rate Testing | ASTM G48 (Potentiodynamic Polarization) | Per lot |
Unique Selling Points
- Superior Acid Resistance: Incoloy® 825 offers unmatched resistance to reducing acids, particularly hot concentrated sulfuric acid and phosphoric acid, where it outperforms 316L, 317L, and even Hastelloy® C-276 in certain conditions.
- Stress Corrosion Cracking Resistance: The titanium addition provides a significant advantage over Incoloy® 800H and other nickel-iron alloys in chloride-containing environments.
- Coil Form Advantage: The coil tube configuration provides continuous-length material that reduces welding joints, minimizes corrosion-prone areas, and enables efficient downstream fabrication with lower material waste.
- Wide Temperature Range: Maintains mechanical properties from cryogenic temperatures up to 1000°C, making it suitable for both low-temperature acid service and high-temperature oxidation environments.
- Weldability: Excellent weldability with standard TIG (GTAW) and MIG (GMAW) processes, allowing on-site fabrication and repair without loss of corrosion resistance.
- Proven Track Record: Decades of successful deployment in the world's most aggressive chemical processing environments validate long-term reliability.
Note: Incoloy® 825 should not be used in environments containing hydrofluoric acid (HF) above 0.1% at elevated temperatures, as fluoride ions can cause rapid intergranular attack. Material selection for fluoride-containing environments requires specific engineering evaluation.