Inconel 625 Nickel Alloy Coil Tube — High-Performance Nickel-Based Alloy Coil Tubing
Product Overview
The Inconel 625 Nickel Alloy Coil Tube is a premium, cold-formed coil tubing manufactured from UNS N06625 (Inconel 625), a precipitation-hardenable nickel-chromium-molybdenum-niobium (Ni-Cr-Mo-Nb) alloy. Produced by Wenzhou Jixing Metal Materials Co., Ltd, this product is engineered to deliver exceptional resistance to high-temperature oxidation, thermal cycling fatigue, and a wide range of corrosive acidic media. The coil tube form factor enables efficient downstream processing—including cutting, bending, welding, and forming—making it ideal for complex geometries in demanding industrial and aerospace applications.
Inconel 625 coil tubing is distinguished by its superior combination of mechanical strength, ductility, and corrosion resistance across an extraordinary temperature range, from cryogenic conditions up to 1,000 °C (1,832 °F). The alloy's beta-phase (Ni₃Nb) precipitation hardening mechanism provides outstanding resistance to stress corrosion cracking (SCC), pitting, crevice corrosion, and intergranular attack, particularly in oxidizing and reducing environments containing chlorides, sulfides, and organic acids.
Material & Properties
Chemical Composition (UNS N06625 / Inconel 625)
| Element | Specification (wt%) | Role |
|---|---|---|
| Nickel (Ni) | Balance (min. 52.0%) | Base matrix; primary source of corrosion resistance and high-temperature strength |
| Chromium (Cr) | 20.0 – 23.0% | Forms protective Cr₂O₃ passive film; enhances oxidation and acid resistance |
| Molybdenum (Mo) | 8.0 – 10.0% | Improves resistance to pitting and crevice corrosion in reducing acids |
| Niobium (Nb) | 4.0 – 5.3% | Forms β-phase precipitates for strengthening; stabilizes microstructure |
| Titanium (Ti) | 0.40 – 0.65% | Aids carbide control; secondary strengthening element |
| Iron (Fe) | ≤ 1.0% | Residual element from processing |
| Carbon (C) | ≤ 0.10% | Controlled to minimize sensitization risk |
| Copper (Cu) | ≤ 0.30% | Residual impurity limit |
| Manganese (Mn) | ≤ 1.0% | Residual impurity limit |
| Sulfur (S) | ≤ 0.015% | Controlled to prevent hot shortness and sulfide inclusions |
| Phosphorus (P) | ≤ 0.015% | Controlled to prevent embrittlement |
Mechanical Properties (Annealed Condition)
| Property | Specification | Test Temperature |
|---|---|---|
| Tensile Strength (UTS) | ≥ 690 MPa (100 ksi) | Room Temperature (20 °C) |
| 0.2% Proof Stress (Yield Strength) | ≥ 310 MPa (45 ksi) | Room Temperature (20 °C) |
| Elongation (A50mm) | ≥ 30% | Room Temperature (20 °C) |
| Hardness (HV) | ≤ 235 HV10 | Room Temperature |
| Density | 8.44 g/cm³ | — |
| Thermal Conductivity | 11.4 W/(m·K) | 100 °C |
| Thermal Expansion Coefficient | 12.8 × 10⁻⁶ /K | 20 – 100 °C |
| Specific Heat Capacity | 440 J/(kg·K) | 100 °C |
| Electrical Resistivity | 1.10 × 10⁻⁶ Ω·m | 20 °C |
Corrosion Resistance Characteristics
- High-Temperature Oxidation Resistance: Continuous service up to 1,000 °C (1,832 °F) in oxidizing atmospheres with formation of a stable, adherent chromium oxide scale.
- Pitting and Crevice Corrosion: Pitting Resistance Equivalent Number (PREN) exceeding 130, providing outstanding resistance to chloride-containing environments.
- Acid Resistance: Immune to nitric acid, sulfuric acid (dilute to concentrated), hydrochloric acid (moderate concentrations), and organic acids including acetic, formic, and citric acid.
- Stress Corrosion Cracking (SCC): Immune to chloride SCC in boiling magnesium chloride (MgCl₂) solutions and seawater at elevated temperatures.
- Fluoride Resistance: Excellent resistance to molten fluorides and hydrofluoric acid environments at moderate temperatures.
- Intergranular Corrosion: Resistant after heat treatment exposure up to 1,150 °C due to niobium-carbide formation instead of chromium-carbide sensitization.
Specifications
| Parameter | Specification |
|---|---|
| Product Form | Coil Tube (Coiltube) — continuous length in coil configuration |
| Alloy Designation | Inconel 625 / UNS N06625 / W.Nr. 2.4856 / Alloy 625 |
| Outer Diameter (OD) | 3.0 mm – 50.0 mm (custom sizes available upon request) |
| Wall Thickness | 0.3 mm – 5.0 mm |
| Coil Inner Diameter (ID) | 150 mm – 300 mm (adjustable based on order volume) |
| Coil Length | Typically 50 m – 200 m per coil (continuous production capability) |
| Surface Finish | Pickled & Passivated (P&P), Bright Annealed (BA), or Polished |
| Tolerance — OD | ± 0.1 mm (standard); ± 0.05 mm (precision grade) |
| Tolerance — Wall Thickness | ± 10% (standard); ± 5% (precision grade) |
| Roundness | ≤ 0.1 mm |
| Flatness (for rectangular/square coil tube) | ≤ 0.1 mm per 100 mm |
| Heat Treatment Condition | Fully Annealed (Solution Annealed at 1,040 °C ± 15 °C, water quenched) |
| Available Shapes | Round, Square, Rectangular, Oval, D-Shaped, and custom cross-sections |
| Applicable Standards | ASTM B619 / AMS 5600 / EN 10217-7 / ISO 11402 / GB/T 2953 |
| Material Form | Coil (continuous rolled form) |
| Packaging | Wooden pallet with moisture-proof wrapping, or custom packaging per customer specification |
Manufacturing Process
The production of Inconel 625 coil tubing at Wenzhou Jixing Metal Materials Co., Ltd follows a rigorously controlled multi-stage manufacturing sequence to ensure consistent metallurgical quality and dimensional precision:
- Raw Material Sourcing & Ingot Casting: High-purity nickel, chromium, molybdenum, niobium, and titanium feedstock are melted via vacuum arc remelting (VAR) or electro-slag remelting (ESR) to produce homogeneous ingots with minimal inclusion content. Each heat is spectrographically verified for full chemical compliance with ASTM B619 specifications.
- Hot Rolling & Billet Production: Remelted ingots are homogenized at 1,150 °C for extended durations and subsequently hot-rolled into strip or wire rod form. The hot rolling process establishes the initial grain structure and dimensional baseline.
- Intermediate Annealing: The hot-rolled strip undergoes controlled annealing at 1,040 °C with rapid water quenching to dissolve all secondary phases, refine the grain structure, and restore full ductility for subsequent cold working operations.
- Cold Rolling & Coil Forming: The annealed strip is cold-rolled to final wall thickness dimensions with precise tension control to achieve uniform thickness and flatness. The cold-rolled strip is then fed into a roll-forming die set that progressively bends and shapes the strip into the desired coil tube cross-section (round, square, rectangular, or custom profile).
- Seam Welding (for welded coil tubes): Where applicable, the formed coil tube undergoes high-frequency induction welding (HF welding) or TIG (Tungsten Inert Gas) seam welding under inert gas (argon) shielding to ensure a gas-tight, metallurgically sound weld seam with minimal heat-affected zone.
- Pipe Welding (for seamless-equivalent coil tubes): Alternatively, the coil strip is drawn through a capillary die with internal gas pressure (Autogenous Capillary Welding / ACW process) to produce a seamless coil tube with uniform wall thickness and no weld seam.
- Solution Annealing & Passivation: The formed coil tube is solution annealed at 1,040 °C ± 15 °C followed by rapid water quenching to achieve the fully annealed condition with maximum corrosion resistance and ductility. Subsequently, the coil tube undergoes pickling (to remove surface oxide scale) and passivation (to establish a chromium-rich passive film) to achieve optimal surface finish and corrosion protection.
- Dimensional Inspection & Quality Control: Every coil undergoes 100% dimensional inspection using ultrasonic thickness gauges, laser diameter measurement systems, and profile scanning equipment. Chemical composition is verified via optical emission spectroscopy (OES). Mechanical properties are tested on representative samples per ASTM E8/E8M and ASTM A370 standards.
- Coiling, Packaging & Shipping: The inspected coil tube is wound onto precision-machined coil cores, secured with steel strapping, wrapped in moisture-proof polyethylene film, and packed onto wooden pallets or custom crates for safe international shipping.
Applications
Inconel 625 coil tubing finds critical application across multiple high-demand industries where conventional stainless steels fail due to extreme corrosion, temperature, or mechanical requirements:
Aerospace & Aviation
- Jet engine exhaust manifolds, afterburner ducting, and heat exchanger tubing operating at temperatures exceeding 800 °C.
- Hydraulic and fuel system tubing requiring resistance to thermal cycling fatigue and fuel fluid compatibility.
- Engine mount brackets and structural components subject to vibration and high-temperature oxidation.
- Spacecraft thermal management systems and radiative cooling panel tubing.
Flue Gas Desulfurization (FGD) & Environmental Protection
- Absorber tower internals, spray nozzles, and mist eliminator support tubing in wet FGD systems treating sulfur dioxide (SO₂) emissions from coal-fired power plants and industrial boilers.
- Wet scrubber spray headers and recirculation piping exposed to acidic slurry containing dissolved SO₂, H₂SO₃, and chloride ions.
- Flue gas ducting and heat recovery steam generator (HRSG) tubing in waste-to-energy and cement kiln applications.
- Denitrification (SCR/SNCR) catalyst support structures and ammonia injection manifold tubing.
Oil & Gas — Acidic Wells & Offshore Platforms
- Downhole tubing, completion strings, and injection tubing in sour wells containing high concentrations of hydrogen sulfide (H₂S), carbon dioxide (CO₂), and chloride ions.
- Wellhead components, Christmas tree tubing, and flowline spools in subsea production systems.
- Offshore platform heat exchangers, vapor recovery units, and acid gas treating system piping.
- Hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC) resistant tubing for sour service per NACE MR0175/ISO 15156 compliance.
Additional Industrial Applications
- Petrochemical Processing: Reactor internals, heat exchanger tubes, and distillation column internals in chlor-alkali, acid production, and polymer manufacturing.
- Chemical Processing: Equipment handling concentrated sulfuric acid, hydrofluoric acid, and molten fluorides.
- Power Generation: Boiler tube components, superheater and reheater tubing, and steam generator internals.
- Marine & Shipbuilding: Ballast water treatment system tubing, seawater cooling circuits, and propeller shaft components.
- Medical & Pharmaceutical: Autoclave components, steam sterilization tubing, and equipment handling aggressive cleaning chemicals.
- Nuclear Energy: Containment building components, spent fuel pool internals, and reactor coolant system instrumentation tubing.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and holds the following certifications and complies with the following international standards:
Quality Management Certifications
- ISO 9001:2015 — Quality Management System certification for manufacturing and supply of metallic products.
- ISO 14001:2015 — Environmental Management System certification ensuring environmentally responsible manufacturing practices.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- ISO 3834-2 — Welding Quality Requirements (where