INCOLOY
Incoloy® 925 (UNS N09925)
High-strength nickel-iron-chromium alloy for demanding oxidizing and reducing environments
Incoloy 925 is an iron-based superalloy combining excellent corrosion resistance with superior strength at elevated temperatures. Engineered for oil and gas downhole applications, geothermal systems, and chemical processing where aggressive H₂S environments demand reliable performance.
Quick Specifications
- Density
- 8.22 g/cm³ (0.297 lb/in³)
- Melting Point
- 2370-2450°F (1300-1345°C)
- Yield Strength (0.2% offset)
- 115-120 ksi (793-827 MPa) at room temperature
- Tensile Strength
- 160-165 ksi (1103-1138 MPa) at room temperature
- Elongation
- 30-35% in 1 inch
- Modulus of Elasticity
- 30.5 × 10⁶ psi (210 GPa) at 68°F
Standards & Certifications
Product Description
Incoloy 925 represents a next-generation superalloy designed specifically for severe corrosion and stress-corrosion cracking resistance in sour environments. Its unique composition balances iron as the primary constituent with substantial nickel and chromium additions, creating exceptional resistance to both oxidizing and reducing attack. The alloy maintains structural integrity even in the presence of hydrogen sulfide, making it ideal for deepwater oil and gas exploration where downhole conditions combine extreme pressure, corrosive gases, and mechanical stress.
The metallurgical structure of Incoloy 925 is carefully controlled through precise heat treatment protocols. The addition of molybdenum, aluminum, and titanium creates a matrix of gamma-prime precipitates that contribute significantly to yield strength and creep resistance at temperatures up to 1400°F (760°C). This precipitation hardening mechanism ensures that mechanical properties remain stable during extended service in high-temperature applications, while the face-centered cubic matrix maintains toughness and ductility.
Incoloy 925 exhibits outstanding resistance to stress-corrosion cracking (SCC) in chloride-containing brines and H₂S environments, a critical requirement for subsea and downhole equipment. The alloy's resistance to pitting and crevice corrosion in seawater and produced water is superior to conventional stainless steels, with NACE rating in harsh sour service environments. Welding characteristics are excellent, with minimal sensitization risk and superior HAZ (heat-affected zone) performance compared to austenitic stainless steels.
Applications range from production tubing and wellhead equipment in deepwater fields to chemical reactor vessels, heat exchangers, and geothermal piping systems. The combination of strength, corrosion resistance, and reliability in demanding environments makes Incoloy 925 a preferred material among major operating companies and equipment manufacturers requiring assured performance over the lifetime of critical infrastructure.
Specifications
| Density | 8.22 g/cm³ (0.297 lb/in³) |
| Melting Point | 2370-2450°F (1300-1345°C) |
| Yield Strength (0.2% offset) | 115-120 ksi (793-827 MPa) at room temperature |
| Tensile Strength | 160-165 ksi (1103-1138 MPa) at room temperature |
| Elongation | 30-35% in 1 inch |
| Modulus of Elasticity | 30.5 × 10⁶ psi (210 GPa) at 68°F |
| Thermal Conductivity | 7.8 BTU/hr·ft·°F at 68°F (13.5 W/m·K) |
| Coefficient of Thermal Expansion | 7.2 × 10⁻⁶ in/in·°F (12.9 × 10⁻⁶ m/m·°C) 68-212°F |
| Creep Rupture Strength | 30 ksi (207 MPa) at 1400°F for 10,000 hours |
| Hardness (Annealed) | ≤ 285 HB |
Chemical Composition
| Element | Content (%) |
|---|---|
| Nickel (Ni) | 42.0-46.0 |
| Iron (Fe) | Balance |
| Chromium (Cr) | 22.0-24.0 |
| Molybdenum (Mo) | 2.8-3.5 |
| Aluminum (Al) | 1.9-2.3 |
| Titanium (Ti) | 1.8-2.3 |
| Cobalt (Co) | 0.0-0.5 |
| Manganese (Mn) | 0.0-0.5 |
| Carbon (C) | 0.05-0.10 |
| Silicon (Si) | 0.15-0.35 |
| Sulfur (S) | ≤ 0.015 |
| Phosphorus (P) | ≤ 0.015 |
Mechanical Properties
| Property | Value |
|---|---|
| Yield Strength @ 70°F | 115-120 ksi (793-827 MPa) |
| Tensile Strength @ 70°F | 160-165 ksi (1103-1138 MPa) |
| Elongation (1 inch gauge) | 30-35% |
| Reduction of Area | 50-55% |
| Rockwell Hardness (C scale) | 25-30 HRC |
| Stress Rupture Strength (10,000 hrs @ 1400°F) | 30 ksi (207 MPa) |
| Impact Strength (Charpy V-notch @ 32°F) | ≥ 85 ft·lbf (115 J) |
| Fatigue Strength (10⁷ cycles) | 65 ksi (448 MPa) at 1000°F |
Key Features & Advantages
Applications
Deepwater Oil & Gas Production
Production tubing, wellhead equipment, and subsea manifolds in H₂S-rich deepwater fields operating at extreme depths and pressures. Incoloy 925 provides reliable performance where equipment failure could result in environmental disaster and operational shutdown.
Geothermal Energy Systems
High-temperature piping, heat exchanger tubing, and downhole equipment in geothermal wells. The alloy's strength retention and corrosion resistance in high-temperature brines with dissolved gases makes it ideal for sustained heat recovery applications.
Chemical Processing Equipment
Reactor vessels, heat exchangers, and piping in chemical plants handling corrosive process streams. The balanced resistance to both oxidizing and reducing acids provides reliable service in complex chemical manufacturing environments.
Sour Service Valves and Fittings
High-pressure valve bodies, seats, and stem materials for sour service applications. The strength and corrosion resistance allow for smaller valve bodies and higher pressure ratings compared to conventional stainless steels.
Pressure Vessel Components
Flanges, closures, and nozzles for high-pressure equipment in corrosive environments. Superior strength-to-weight ratio enables optimized designs while maintaining regulatory compliance and safety margins.
Aerospace Engine Components
Landing gear components and fasteners in modern aircraft engines. The exceptional strength and fatigue resistance at temperature make Incoloy 925 valuable for critical structural components exposed to severe thermal and mechanical cycling.
Frequently Asked Questions
How does Incoloy 925 compare to super duplex stainless steels in sour environments?
What is the maximum temperature at which Incoloy 925 maintains adequate properties?
Is Incoloy 925 weldable, and what precautions are necessary?
What certifications and compliance documentation is available?
How should Incoloy 925 be machined to achieve optimal surface quality?
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