Incoloy 925 Product Introduction
Product Overview
Incoloy 925 (UNS N09925) is a precipitation-hardening nickel-iron-chromium-molybdenum-copper superalloy engineered for harsh environments requiring both exceptional corrosion resistance and high mechanical strength. Unlike Incoloy A286 (iron-based, focus on medium-high temp strength) or Incoloy 825 (nickel-iron-based, focus on corrosion resistance but lower strength), Incoloy 925 combines a high-nickel matrix (42-46%) for corrosion stability, molybdenum/copper for localized corrosion resistance, and titanium/aluminum for γ' phase (Ni₃(Ti,Al)) precipitation hardening—delivering tensile strength up to 930 MPa (room temp) while resisting pitting, crevice corrosion, and stress corrosion cracking (SCC) in H₂S/Cl⁻-rich media. It maintains performance up to 600°C, making it the preferred material for critical components in acidic oil & gas wells, chemical processing, and marine engineering where "strength + corrosion resistance" are equally critical.
International Grade Comparison
Standard System | Grade | Description |
ASTM (USA) | N09925 | UNS Unified Numbering System Grade (exclusive for Incoloy 925) |
EN (EU) | NiFe30Cr20Mo4Cu | EN 10088-1 Standard Grade (precipitation-hardening, corrosion-resistant type) |
JIS (Japan) | NW09925 | JIS G4902 Standard Grade (equivalent to Incoloy 925) |
DIN (Germany) | 1.4529 | DIN 17750 Standard Grade (nickel-iron-chromium-molybdenum precipitation alloy) |
ISO (International) | NiFe30Cr20Mo4Cu | ISO 6363 Standard Grade (corrosion & strength dual-optimized variant) |
Physical Properties (Room Temperature & High-Temperature Highlights)
Property Indicator | Typical Value (Room Temp, After Precipitation Hardening) | Unit | High-Temperature & Corrosion Advantage |
Tensile Strength | ≥930 | MPa | 600°C tensile strength: ≥620 MPa; retains 70% strength vs. room temp |
Yield Strength (0.2% Offset) | ≥690 | MPa | 600°C yield strength: ≥480 MPa; no significant softening up to 600°C |
Elongation (50mm Gauge Length) | ≥15 | % | Maintains ductility in sour environments (H₂S: 100 psi, 25°C) |
Density | 8.1 | g/cm³ | Higher than A286 (7.9 g/cm³) due to higher nickel/molybdenum content |
Melting Point | 1360-1410 | ℃ | Stable up to maximum service temperature (600°C) |
Chemical Composition (Mass Fraction, Key Elements with Dual-Function Roles)
Chemical Symbol | Composition Range (%) | Role in Performance |
Ni | 42.0-46.0 | Stabilizes austenite; enhances resistance to SCC in H₂S media |
Fe | 22.0-26.0 | Optimizes cost vs. nickel-based alloys; improves thermal conductivity |
Cr | 19.0-21.0 | Forms Cr₂O₃ oxide film; resists general oxidation and sulfur corrosion |
Mo | 3.0-4.0 | Inhibits pitting/crevice corrosion in Cl⁻-rich environments (e.g., seawater, brine) |
Cu | 1.5-2.5 | Enhances resistance to sulfuric acid and weak organic acids |
Ti | 1.9-2.4 | Primary precipitation hardener; forms γ' phase (Ni₃Ti) for strength |
Al | 0.1-0.5 | Co-precipitates with Ti to refine γ' phase; boosts high-temp strength |
C | ≤0.03 | Minimizes carbide precipitation; avoids intergranular corrosion |
Si/Mn | ≤0.5/≤1.0 | Improves hot workability; reduces welding defects |
P/S | ≤0.02/≤0.015 | Critical for sour service: low S prevents sulfide stress cracking (SSC) |
Product Characteristics
1.Dual Advantage: High Strength + Superior Corrosion Resistance: Precipitation hardening delivers ≥930 MPa tensile strength (30% higher than Incoloy 825), while Ni-Mo-Cu-Cr synergy resists SCC in H₂S/Cl⁻ environments (meets NACE MR0175/ISO 15156 sour service standards);
2.Excellent Localized Corrosion Resistance: Mo (3-4%) + Cr (19-21%) provides pitting resistance equivalent (PREN) ≥35—outperforming A286 (PREN ≈20) and suitable for seawater, brine, and acidic brine applications;
3.Stable Medium-Temperature Performance: Retains high strength and ductility up to 600°C, avoiding softening or brittle phase formation (e.g., sigma phase) during long-term service;
4.Sour Service Compliance: Low sulfur content (≤0.015%) and optimized Ni content (42-46%) meet NACE MR0175 for use in oil & gas wells with H₂S partial pressure ≥100 psi;
5.Reliable Processability: Compatible with hot/cold working (forging, rolling, machining) and welding; post-weld aging (704°C × 8 hours) restores full strength and corrosion resistance—no complex solution annealing required.
Metallographic Structure
•As-annealed State: Uniform face-centered cubic (FCC) austenitic matrix with ASTM grain size 5-8 grades; no visible precipitates, ensuring good formability for manufacturing;
•After Precipitation Hardening: Austenitic matrix dispersed with nano-scale γ' phase (Ni₃(Ti,Al)) (5-15 nm in size) and trace TiC carbides. γ' phase acts as "dislocation pinning points" to enhance strength, while no harmful intermetallic phases (e.g., μ phase) form—ensuring long-term structural stability even in corrosive/high-temp environments.
Product Forms and Executive Standards
Product Form | Main International Executive Standards | Application Reference |
Plates/Strips | ASTM B408/B564, EN 10088-2 | Acidic oil well wellhead flanges, chemical reactor liners |
Seamless Pipes/Tubes | ASTM B625/B775, EN 10216-5 | Sour gas well downhole tubulars, seawater cooling pipes |
Bars/Forgings | ASTM B408/B564, EN 10269 | Oil & gas valve bodies, pump shafts, drill collars (sour service) |
Wires | ASTM B805, EN 10250-3 | Welding filler wires for corrosion-resistant joints, precision fasteners |
