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Incoloy 925 seamless pipe and tube (UNS N09925, ASTM B161/B983) is a nickel-iron-chromium-molybdenum-copper-titanium alloy designed for exceptional resistance to chloride-induced stress-corrosion cracking (SCC) and high-temperature oxidation. Composed of 42% nickel, 22% chromium, 3% molybdenum, 2.5% copper, 1.8% titanium, and balanced iron, it combines the chloride resistance of Incoloy 825 with titanium stabilization to prevent intergranular corrosion. Manufactured via seamless hot-rolling and cold-drawing to meet standard, it features a fine-grained microstructure for uniform mechanical properties.
Incoloy 925’s unique composition makes it a preferred choice for sour gas environments where H2S, CO2, and chlorides coexist, outperforming conventional stainless steels in harsh downhole conditions.
Sour Gas Resistance: Resists SCC in H2S-containing brines (up to 30,000 ppm Cl⁻, pH 2-6) and meets NACE MR0175 requirements for sulfide stress corrosion (SSC), making it suitable for HPHT (high-pressure, high-temperature) oil wells.
Balanced Corrosion Resistance: Handles both oxidizing (e.g., Fe³+/Cu²+ ions) and reducing (H2S/CO2) conditions, with excellent resistance to pitting in seawater and organic acids.
High-Temperature Stability: Maintains tensile strength >650 MPa at 500°C and resists scale formation in air up to 850°C, ideal for downhole tubing and surface equipment.
Ease of Fabrication: Weldable with ERNiCrMo-3 filler metal (GTAW/GMAW) and formable via cold working (up to 20% reduction) without intermediate annealing, though heat treatment improves ductility for severe bends.
Oil & Gas Exploration: Used as production tubing, casing, and Christmas tree components in deepwater wells (e.g., Gulf of Mexico), enduring H2S (10,000+ ppm) and high salinity (200,000 ppm Cl⁻).
Chemical & Petrochemical: Ideal for refinery overhead condensers, amine treaters, and pipelines transporting corrosive crude oil fractions.
Marine Cables: Employed in subsea power cables and umbilicals, resisting biofouling and galvanic corrosion in seawater-mud interfaces.
Geothermal Energy: Suitable for high-temperature brine pipelines (150-300°C) in geothermal plants, resisting sulfide and chloride attack simultaneously.
Q: How does Incoloy 925 differ from Incoloy 825?
A:925 adds titanium (1.8% vs. 0.6% in 825) to stabilize carbon, improving intergranular corrosion resistance in welded joints, and has lower iron (balance vs. 32%), enhancing H2S resistance.
Q: Can 925 be used in pure H2SO4?
A:It resists dilute H2SO4 (<50% at 80°C) but is optimized for mixed H2S/CO2/chloride environments; use Hastelloy C2000 for concentrated sulfuric acid.
Q: What is the minimum yield strength of Incoloy 925?
A:As-annealed: 380 MPa (55 ksi); cold-worked: up to 550 MPa (80 ksi), with elongation ≥30% in both conditions.
Q: Does 925 require NACE-compliant testing for oil field use?
A:Yes, typical specifications include hardness testing (≤22 HRC), SSC testing (ASTM G41), and HIC (hydrogen-induced cracking) resistance per NACE TM0284.
| Grade | C | Mn | Si | S | Cr | Mo | Co | Ti | Al | Fe | Ni | Cu |
| N09925 | ≤0.03 | ≤1.00 | ≤0.50 | ≤0.03 | 19.50-23.5 | 2.50-3.50 | ≤0.50 | 1.90-2.40 | 0.10-0.50 | ≥22.00 | 38.00-46.00 | 1.50-3.00 |
