COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF INCONEL 725 (UNS N07725) FASTENING SYSTEMS
Inconel 725 is a high-performance nickel-chromium-molybdenum-niobium superalloy engineered to bridge the gap between the exceptional corrosion resistance of Alloy 625 and the ultra-high strength requirements of modern industrial infrastructure. While it shares a nearly identical chemical foundation with Alloy 625, Inconel 725 is specifically designed to be age-hardenable.
Through the addition of approximately 1.5% titanium and a controlled precipitation heat treatment, this alloy develops a fine dispersion of gamma-double-prime (γ'') precipitates, resulting in yield and tensile strengths that are roughly double those of annealed Grade 625. This unique combination makes it a critical material for high-load fastening applications in the most aggressive corrosive environments, such as deep-water sour gas wells and naval submarine components.
■ Product Overview
Inconel 725 represents the pinnacle of precipitation-strengthened nickel alloys for aqueous and high-pressure service.
| Material Classification | Precipitation-Hardenable Ni-Cr-Mo-Nb Superalloy |
|---|---|
| UNS Designation | N07725 |
| Common Trade Names | Alloy 725, Nickel 725, Inconel 725® |
| Microstructure | Austenitic with fine γ'' (Ni3Nb) precipitates |
| Magnetic State | Non-magnetic (Paramagnetic); Permeability < 1.001 |
| Corrosion Resistance | Excellent in H2S, CO2, and chloride-rich environments |
| Strengthening Method | Precipitation Hardening (Ageing) |
| Primary Advantage | High strength in large sections that cannot be cold-worked |
■ Proprietary Datasheet Download (GATED)
Access professional-grade technical data for Inconel 725, including elevated temperature mechanicals, PREN calculations, torque charts, and sour service limits.
Inconel 725 / UNS N07725 — Complete Technical Datasheet
Contains detailed UTS and Yield charts up to 648°C, validated Pitting Resistance Equivalent Number (PREN > 45) data, specific dry and lubricated installation values, and threshold data for H2S partial pressure.
⬇ DOWNLOAD DATASHEET■ Chemical Composition
The alloy's performance is derived from a strategic balance of elements. The addition of titanium is the primary differentiator from Alloy 625, enabling the age-hardening response.
| Element | Weight % (UNS N07725) |
|---|---|
| Nickel (Ni) | 55.0 – 59.0 |
| Chromium (Cr) | 19.0 – 22.5 |
| Molybdenum (Mo) | 7.0 – 9.50 |
| Niobium (Nb) | 2.75 – 4.00 |
| Titanium (Ti) | 1.00 – 1.70 |
| Iron (Fe) | Balance |
| Aluminum (Al) | 0.35 max |
| Carbon (C) | 0.03 max |
| Manganese (Mn) | 0.35 max |
| Silicon (Si) | 0.20 max |
| Phosphorus (P) | 0.015 max |
| Sulfur (S) | 0.010 max |
■ Mechanical Properties
Unlike standard austenitic alloys that rely on cold work for strength, Inconel 725 achieves its properties through heat treatment, ensuring uniformity even in large-diameter fasteners and heavy sections.
| Mechanical Property | Solution Treated (Annealed) | Age Hardened (Typical) |
|---|---|---|
| Ultimate Tensile Strength (UTS) | ≈ 855 MPa (124 ksi) | ≥ 1034 MPa (150 ksi) |
| 0.2% Yield Strength | ≈ 427 MPa (62 ksi) | ≥ 827 MPa (120 ksi) |
| Elongation (% in 50mm) | 57% | 20% – 32% |
| Reduction of Area | – | 35% min |
| Hardness (Rockwell C) | 5 HRC (avg) | 36 – 43 HRC |
| Impact Strength (RT) | – | ≈ 132 J (97 ft·lb) |
■ Equivalent Grades
Inconel 725 is cross-referenced globally for use in international energy and defense projects.
| Standard / System | Designation |
|---|---|
| UNS (USA) | N07725 |
| JIS (Japan) | NCF 725 |
| ASTM | ASTM B805 |
| DIN (Germany) | W.Nr. 2.4856 (Variant) |
| NACE / ISO | MR0175 / ISO 15156 |
| API | API 6CRA |
■ Applications & Industries
Inconel 725 is mandated where high fatigue strength and resistance to stress-corrosion cracking (SCC) are critical.
- Oil and Gas (Upstream): Used for hangers, landing nipples, side pocket mandrels, and polished bore receptacles (PBRs) in sour gas service where H2S, chlorides, and CO2 are present.
- Marine Engineering: High-strength fasteners for naval systems, submarine components, and subsea hydraulic couplings.
- Aerospace: High-temperature bolts, jet engine spacers, wheels, and airframe parts.
- Chemical Processing: Critical valves, agitators, and pump shafts exposed to high-temperature reducing acids.
■ Fastener Types Available
Ananka Group manufactures a comprehensive range of Inconel 725 fasteners designed for extreme pressure and safety-critical service.
- Bolts: Hex Head Bolts, Heavy Hex Bolts, Socket Head Cap Screws, Eye Bolts, and Custom Forged Bolts.
- Nuts: Hex Nuts, Heavy Hex Nuts, Coupling Nuts, Jam Nuts, and Nylock Nuts.
- Screws: Machine Screws, Set Screws, and Socket Cap Screws.
- Washers: Flat Washers, Spring Lock Washers, Square Washers, and Ogee Washers.
- Studs: Fully Threaded Rods, Double-End Studs, and Tap-End Studs.
■ Standards & Specifications
Fasteners are manufactured to meet the most stringent international engineering codes for pressure and safety integrity.
- ASTM B805: Standard specification for precipitation-hardening Nickel alloy bar and wire.
- ASTM B166 / ASME SB166: Specification for Nickel-Chromium-Iron alloys (related components).
- API 6CRA: Requirements for age-hardened Nickel-based alloys for use in oil and gas environments.
- NACE MR0175 / ISO 15156: Materials for use in H2S-containing environments in oil and gas production.
■ MTC Integration Section
Material traceability is the backbone of safety in high-pressure systems. Ananka Group provides fully authenticated Material Test Certificates (MTC) for all Inconel 725 batches.
- EN 10204 Type 3.1: Issued by our independent quality department, this certificate provides specific heat-traceable test results (chemical, mechanical, hardness, and PMI).
- EN 10204 Type 3.2: For subsea, nuclear, or "lethal service" applications, we facilitate third-party witness testing (e.g., TUV, BV, or SGS) to provide the highest level of material assurance.
■ Why Choose Ananka Group for Inconel 725?
Ananka Group is a leading manufacturing-driven organization in Mumbai, specializing in high-performance fasteners for the global energy and marine sectors.
- Manufacturing Capability: Expertise in hot forging for large-diameter bolts (up to M100) and precision CNC machining for custom subsea components.
- In-House Testing: Advanced facilities for Tensile, Hardness, IGC (Intergranular Corrosion), and Positive Material Identification (PMI).
- Certifications: ISO 9001:2015, ISO 14001:2015, and PED 2014/68/EU certified for pressure equipment components.
- Technical Support: Direct engineering consultation for project-specific metallurgy and coating requirements (Xylan, PTFE, Zinc-Nickel).
■ Frequently Asked Questions
1. Is Inconel 725 magnetic?
No, Inconel 725 is non-magnetic and paramagnetic in all conditions. It has a magnetic permeability of less than 1.001 at room temperature, making it ideal for electronic housings and sensitive naval equipment.
2. How does Inconel 725 compare to Inconel 625?
While both have similar corrosion resistance, Inconel 725 is precipitation-strengthened, resulting in a yield strength that is roughly twice that of annealed 625. This makes 725 the preferred choice for high-load fasteners where the strength of 625 is insufficient.
3. Why is Titanium added to Inconel 725?
Titanium (1.0–1.7%) is added to the nickel-chromium matrix to allow for the formation of microscopic gamma-prime and gamma-double-prime precipitates during heat treatment. These precipitates "pin" the grain structure, significantly increasing the material's strength and toughness.
4. Can Inconel 725 be used in sour gas wells?
Yes, Inconel 725 is NACE MR0175/ISO 15156 approved. Its high molybdenum and chromium content provides outstanding resistance to hydrogen sulfide (H2S), carbon dioxide (CO2), and chloride-induced stress corrosion cracking.
5. What is the maximum service temperature for Inconel 725?
While it maintains good oxidation resistance at high temperatures, its mechanical stability is best utilized up to approximately 593°C (1100°F) for long-term load-bearing service, similar to Alloy 625.
6. Does Inconel 725 have good toughness?
Yes, because Inconel 725 gains its strength through aging heat treatment rather than cold work, it maintains high ductility and excellent impact toughness, even in heavy sections.
For project-specific technical support or to request a quote for Inconel 725 fasteners, please contact the Ananka Group Sales and Engineering Team at sales@anankafasteners.com or via WhatsApp at +91 86557 47687. Secure your high-pressure systems with PED-certified components and world-class metallurgical expertise.