In deep-sea environments, material failure is not merely a costly loss, but a catastrophic threat to structural integrity. For offshore engineers and procurement managers, a major pain point in high-pressure/high-temperature (HP/HT) environments is "hidden fracture."
At Gnee Alloy, we are committed to eliminating these risks. Our AMS 5666 Inconel 625 bars are meticulously designed to maintain absolute reliability even in the deep sea.
Click to get an Inconel 625 product quoteAMS 5666 Inconel 625 bars are designed for high-pressure subsea environments | NACE MR0175 standards
AMS 5666 Inconel 625 bars are designed for high-pressure subsea environments | Compliant with NACE MR0175 standards
AMS 5666 Inconel 625 bar stock (UNS N06625) is a solution-strengthened nickel-chromium superalloy. Designed for high-pressure, highly corrosive environments, it exhibits excellent resistance to seawater corrosion, pitting corrosion, and stress corrosion cracking. Fully compliant with NACE MR0175 standards, it is suitable for sulfur-containing oilfield environments.
What is the hardness of Inconel 625?
Inconel 625 has a moderate hardness in its standard annealed state, typically around 20 to 29 HRC (Rockwell hardness C). While this is softer than grades like Inconel 718, it is extremely difficult to cut or machine due to its high viscosity, rapid work hardening during processing, and high abrasiveness.
1. AMS 5666 Inconel 625 Bar Specifications for High-Pressure Submarine Environments
| Parameter | Description |
|---|---|
| Specification | AMS 5666 (Aerospace Material Specification) |
| Material | Inconel 625 (UNS N06625) |
| Chinese Equivalent | GH3625 |
| Product Form | Bar (for subsea high pressure environment) |
| Material Type | Wrought Nickel-based Corrosion Resistant Superalloy |
| Strengthening Mechanism | Solid-solution strengthening (Mo + Nb) |
| Typical Applications | Subsea wellhead equipment, BOP components, subsea connectors, high pressure manifolds, subsea valves |
| Design Water Depth | Up to 3,000 meters (10,000 feet) |
| Design Pressure | Up to 15,000 psi (103 MPa) |
| Operating Temperature Range | -54°C to 150°C (typical subsea environment) |
| Delivery Condition | Solution treated (annealed) – not age-hardenable |
| Aerospace/Subsea Grade | VIM + VAR (double melt – mandatory) |
2. AMS 5666 Inconel 625 Submarine Bar Chemical Composition (wt%)
| Element | Content (%) | AMS 5666 Requirement | Function |
|---|---|---|---|
| Nickel (Ni) | ≥ 58.0 (Balance) | ≥ 58.0 | Matrix element; corrosion resistance and high-temperature stability |
| Chromium (Cr) | 20.0 – 23.0 | 20.0 – 23.0 | Oxidation and corrosion resistance |
| Molybdenum (Mo) | 8.0 – 10.0 | 8.0 – 10.0 | Core element – provides pitting and crevice corrosion resistance in seawater |
| Niobium (Nb) | 3.15 – 4.15 | 3.15 – 4.15 | Solid-solution strengthening; enhances creep resistance |
| Iron (Fe) | ≤ 5.0 | ≤ 5.0 | Residual element |
| Titanium (Ti) | ≤ 0.40 | ≤ 0.40 | Supplementary strengthening |
| Aluminum (Al) | ≤ 0.40 | ≤ 0.40 | Supplementary strengthening |
| Carbon (C) | ≤ 0.10 | ≤ 0.10 | Low carbon for corrosion resistance |
| Manganese (Mn) | ≤ 0.50 | ≤ 0.50 | Deoxidizer |
| Silicon (Si) | ≤ 0.50 | ≤ 0.50 | Deoxidizer |
| Phosphorus (P) | ≤ 0.010 | ≤ 0.015 | Stricter for aerospace/subsea |
| Sulfur (S) | ≤ 0.005 | ≤ 0.015 | Stricter for aerospace/subsea |
| Cobalt (Co) | ≤ 1.0 | ≤ 1.0 | Residual element |
| Copper (Cu) | ≤ 0.07 | - | Low copper for seawater compatibility |
3. AMS5666 inconel 625 Bar Dimensional Specifications
| Diameter (mm) | Diameter (in) | Length (mm) | Tolerance | Surface |
|---|---|---|---|---|
| 10 – 18 | 0.375 – 0.750 | 2000 – 6000 | h6 – h8 | Ground / Bright |
| 18 – 30 | 0.750 – 1.200 | 2000 – 6000 | h6 – h8 | Ground / Bright |
| 30 – 50 | 1.200 – 2.000 | 2000 – 4000 | h6 – h8 | Ground / Bright |
| 50 – 80 | 2.000 – 3.150 | 2000 – 4000 | h7 – h9 | Ground / Rough Turned |
| 80 – 100 | 3.150 – 4.000 | 1000 – 3000 | h7 – h9 | Rough Turned |
| 100 – 150 | 4.000 – 6.000 | 1000 – 3000 | h8 – h10 | Rough Turned |
| 150 – 200 | 6.000 – 8.000 | 1000 – 2000 | h9 – h11 | Rough Turned |
Dimensional Tolerances (AMS 5666)
| Parameter | Range | Tolerance |
|---|---|---|
| OD (≤ 25.4 mm) | - | ±0.025 – ±0.050 mm |
| OD (25.4 – 50.8 mm) | - | ±0.050 – ±0.075 mm |
| OD (50.8 – 101.6 mm) | - | ±0.075 – ±0.100 mm |
| Length | Up to 6,000 mm | ±1 mm |
| Straightness | - | ≤ 0.5 mm/m |
| Roundness | - | ≤ 0.5% of diameter |
4. AMS 5666 Inconel 625 Submarine Solution Annealed Bars: Room Temperature Mechanical Properties
| Property | AMS 5666 Requirement | Typical Value | Test Standard |
|---|---|---|---|
| Tensile Strength, Ultimate | ≥ 830 MPa (120 ksi) | 900 – 950 MPa | ASTM E8 / AMS 2370 |
| Tensile Strength, Yield (0.2% Offset) | ≥ 415 MPa (60 ksi) | 450 – 500 MPa | ASTM E8 / AMS 2370 |
| Elongation at Break | ≥ 30% | 35 – 45% | ASTM E8 / AMS 2370 |
| Reduction of Area | Not specified | 50 – 60% | ASTM E8 |
| Hardness (Rockwell B) | ≤ 96 HRB | 90 – 95 HRB | ASTM E18 |
| Hardness (Rockwell C) | - | ~22 HRC | ASTM E18 |
| Modulus of Elasticity | ~207 GPa (30.0 × 10⁶ psi) | - | ASTM E111 |
| Poisson's Ratio | 0.29 – 0.30 | - | - |
5. AMS 5666 Inconel 625 Submarine High-Pressure Bar Design Requirements
| Requirement | Specification | Significance |
|---|---|---|
| Minimum Tensile Strength | 830 MPa (120 ksi) | Component design basis |
| Minimum Yield Strength | 415 MPa (60 ksi) | Pressure containment design |
| Minimum Elongation | 30% | Ductility for installation |
| Hardness Limit | ≤ 35 HRC (NACE) | SSC resistance for sour service |
| Burst Pressure | ≥ 2.0 × Design Pressure | Safety factor |
| Proof Pressure | 1.5 × Design Pressure | Factory hydrostatic test |
| Hydrostatic Pressure | External pressure resistance | Deep sea water depth capability |
| Collapse Resistance | Design basis | External pressure resistance |
6. Gnee Alloy Inconel 625 Bar Stock NACE MR0175 / ISO 15156 Standard
| Parameter | Inconel 625 (AMS 5666) | Requirement/Notes |
|---|---|---|
| Sour Gas Service (H₂S) | ✅ Compliant | NACE MR0175 / ISO 15156 certified |
| Maximum Hardness | ≤ 35 HRC | Annealed ~22 HRC – meets requirement |
| SSC Resistance | Excellent | No risk of stress corrosion cracking |
| H₂S Partial Pressure Limit | No limit | Suitable for any H₂S partial pressure |
| Chloride Concentration Limit | No limit | Suitable for any chloride concentration |
| Temperature Range | -60°C to 232°C | Covers full subsea oil & gas range |
| pH Range | 3.0 – 12.0 | Wide pH compatibility |
| Applicable Standards | API 6A, 17D, 6A | Wellhead, subsea equipment |
7. AMS 5666 Inconel 625 bar heat treatment properties
| Parameter | Specification |
|---|---|
| Condition | Solution Annealed |
| Temperature | 940 – 1040°C |
| Time | 1 hour per 25mm thickness |
| Atmosphere | Controlled atmosphere for bright finish |
| Cooling | Rapid cool (water or air) |
8. AMS 5666 Inconel 625 Bar Non-destructive Testing (NDT)
| Test Method | Requirement | Standard | Acceptance Criteria |
|---|---|---|---|
| Ultrasonic Testing (UT) | 100% (bars ≥ 12mm) | ASTM E2375 / AMS 2370 | No defects exceeding 0.8mm |
| Eddy Current Testing (ET) | As specified (surface) | ASTM E426 | No relevant indications |
| Liquid Penetrant Inspection (LPI) | 100% (finished components) | ASTM E1417 | No relevant indications |
| Visual Inspection | 100% (10-30x magnification) | ASTM E543 | No surface defects |
| Hardness Testing | 100% (NACE requirement) | ASTM E18 | ≤ 35 HRC |
9. Why choose to partner with our Gnee Alloy factory?
✅️Audit-Ready MTC 3.1: Every shipment is accompanied by a full EN 10204 3.1 or 3.2 certificate documenting exact heat analysis and PREN values.
✅️Wholesale Pricing: Benefit from Direct Factory Price on bulk tonnage for large-scale offshore field developments.
✅️Short Lead Time: We maintain a massive Wholesale Inventory of 1" to 12" diameter rods ready for Immediate Global Dispatch.
✅️Custom Fabrication: We offer precision centerless grinding and Cut-to-Length services to minimize your material waste.
Gnee Alloy Inconel 625 certificate
Gnee Alloy Product Packaging
All stainless steel products are:
✅️Packed in wooden pallets or crates
✅️Covered with moisture-proof wrapping
✅️Labeled with heat number, standard, and size
✅️Shipped worldwide via sea, air, or express
Gnee Alloy 625 Alloy Packaging
Gnee Alloy Production Equipment and Product Testing
FAQ
Q1: Why is the 35 HRC hardness limit so important for Inconel 625?
A: According to NACE MR0175, keeping the hardness of Inconel 625 below 35 HRC (in certain conditions) is the primary defense against Sulfide Stress Cracking. Higher hardness often indicates inconsistent solution annealing, which creates internal stresses and vulnerability to H₂S.
Q2: Is your GH3625 (Inconel 625) interchangeable on an international blueprint?
A: Yes. GH3625 is the technical equivalent designation used within the Chinese national standard system for the exact same metallurgical system as UNS N06625. We provide materials that comply with the technical threshold of AMS 5666 and ASTM B446.
Q3: Can these bars be used for subsea fasteners?
A: Absolutely. Our AMS 5666 bright rods are optimized for precision thread rolling and CNC machining. Their exceptional straightness and uniform hardness ensure stable high-speed automated production of subsea bolts.
Q4: Do you support small trial orders for prototype manifolds?
A: Yes. As a Reliable Supplier, we support innovation. We offer Flexible MOQs on our in-stock inventory to help your R&D phase reach certification faster.
