Overview
Seamless Incoloy 925 Nickel Alloy Pipe (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.
Chemical Composition
| 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 |
Features
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.
Mechanical Properties
(as per ASTM B163)
Grade | Condition | Tensile Strength ksi(MPa) | Yield Strength ksi(MPa) | Elongation(%) | Rockwell Harness for annealed ends |
| N09925 | SolutionAnn+prechard | ≥140(965) | ≥140(965) | ≥18 | 38 |
Applications
Alloy 925 (UNS N09925) is an age-hardenable nickel-iron-chromium alloy with additional elements such as molybdenum, copper, titanium, and aluminum. This alloy is utilized in various applications that require a combination of high strength and corrosion resistance. Let's explore its industrial uses:
Chemical Processing:
It finds applications in reactors, heat exchangers, and other components exposed to aggressive chemical environments.
Alloy 925 is commonly employed in chemical processing equipment due to its excellent resistance to reducing chemicals.
Oil and Gas Industry:
In the oil and gas sector, Alloy 925 is used for downhole tools, subsea components, and offshore platforms.
Its ability to withstand corrosive seawater and harsh downhole conditions is crucial1.
Aerospace and Aircraft Components:
Alloy 925 is found in aircraft engine components, where high-temperature resistance and mechanical strength are essential.
It contributes to the reliability and performance of aerospace systems.
Marine Engineering:
The alloy is suitable for marine applications, including propeller shafts, fasteners, and other fixtures.
Its corrosion resistance ensures durability in saltwater environments
Heat Exchangers and Boiler Feedwater Heaters:
Remember that Alloy 925's properties make it a versatile material across different industries, especially where both strength and corrosion resistance are critical.
