Alloy 925 UNS N09925: Premium Age-Hardenable High-Strength Nickel-Iron-Chromium Alloy for Severe Corrosion & High-Pressure Service

Alloy 925 (UNS N09925, widely known as Incoloy 925) is a precipitation-hardening nickel-iron-chromium specialty alloy reinforced with molybdenum, copper, titanium and aluminum, highly recognized by manufacturers of oil & gas downhole equipment, offshore marine facilities, high-pressure chemical vessels and heavy-duty corrosion-resistant fasteners worldwide. Distinguished from conventional solid-solution nickel alloys, Alloy 925 gains exceptional tensile and yield strength via gamma prime (Ni₃(Al,Ti)) precipitation after aging heat treatment, while retaining full-spectrum anti-corrosion performance in oxidizing, reducing, chloride-rich and sour H₂S/CO₂ environments. Its balanced multi-element matrix resists sulfide stress cracking (SSC), chloride stress corrosion cracking (SCC), pitting and crevice corrosion simultaneously, making it the primary CRA (Corrosion Resistant Alloy) selection for extreme high-pressure, high-temperature corrosive working conditions.

This alloy is engineered specifically for sour crude & natural gas extraction, offshore seawater service and chemical processing with mixed acid media. It maintains stable mechanical and anti-corrosion properties under long-term thermal cycling up to 650°C, complies with global oilfield standards NACE MR0175 / ISO 15156 and API 6A CRA, and meets ASME pressure vessel certification requirements. Hot/cold forming and welding performance are well-controlled, supporting the production of forgings, bars, seamless tubes and precision machined structural components for critical industrial hardware.

Alloy 925 Basic Information

Item	Specification Details
UNS Unified Number	N09925
Commercial Trade Name	Incoloy 925
W.Nr. German Standard	2.4858
Alloy Category	Precipitation/Age-Hardenable Nickel-Iron-Chromium Corrosion Resistant Alloy
Core Application Positioning	High-strength CRA for sour oil & gas, offshore marine and high-pressure chemical equipment
Maximum Continuous Service Temperature	650°C
Critical Compliance Standard	NACE MR0175, API 6A CRA, ASME Code Case 2218

UNS N09925 Chemical Composition (Mass %)

Note: Listed ranges conform to ASTM & international nickel alloy standards. Final delivered chemical composition shall be subject to factory Mill Test Certificates (MTC) and third-party independent inspection reports.

Element	Alloy 925 UNS N09925
Nickel (Ni)	42.0–46.0
Chromium (Cr)	19.5–22.5
Iron (Fe)	Balance, min. 22.0
Molybdenum (Mo)	2.5–3.5
Copper (Cu)	1.5–3.0
Titanium (Ti)	1.9–2.4
Aluminum (Al)	0.1–0.5
Carbon (C)	Max. 0.03
Manganese (Mn)	Max. 1.00
Silicon (Si)	Max. 0.50
Sulfur (S)	Max. 0.030
Phosphorus (P)	Max. 0.030
Niobium (Nb)	Max. 0.50

Incoloy 925 Applicable Industrial Standards

Product Form	Applicable Specifications
Seamless Tubing & Pipe	ASTM B805 / ASME SB805
Hot Rolled & Forged Round Bars	ASTM B806 / ASME SB806
Plates, Sheets & Strips	ASTM B906 / ASME SB906
Open-Die & Closed-Die Forgings	ASTM B564 / ASME SB564
Sour Oil & Gas Service	NACE MR0175 / ISO 15156, API 6A CRA
Pressure Vessel Construction	ASME Section VIII Div.1 Code Case 2218

Alloy 925 UNS N09925 Core Performance Advantages

Performance Item	Technical Description
Age-Hardening High Strength	Ti & Al precipitate γ′ intermetallic phase during aging heat treatment; aged condition delivers yield strength ≥758 MPa, outstanding load-bearing capacity for high-pressure structural parts
Multi-Media Broad-Spectrum Corrosion Resistance	Cr provides oxidation resistance; Mo+Cu synergistically resist sulfuric/phosphoric reducing acids; high Ni matrix suppresses chloride SCC, fully stable in alternating acid-alkali environments
Sour Gas SSC & H₂S Corrosion Resistance	Formulated for H₂S/CO₂ mixed downhole media, eliminates sulfide stress cracking risk, certified compliant with NACE sour service specifications
Superior Localized Corrosion Resistance	High PREN value above 26, robust protection against seawater brine-induced pitting and crevice corrosion for long-term offshore deployment
High-Temperature Microstructure Stability	Negligible grain coarsening and minor strength degradation under continuous service up to 650°C, reliable for high-temperature pressure-bearing equipment
Fabrication & Weld Compatibility	Ductile in solution-annealed state for hot forging, cold turning and deep machining; suitable for GTAW/GMAW with matching Ni-base filler metals; post-weld aging restores full strength
Excellent Low-Temperature Toughness	No ductile-brittle transition at subzero temperatures, maintains stable Charpy impact toughness down to -60°C for cryogenic corrosive process systems

Applications

Industry Sector	Representative Components
Sour Oil & Gas Upstream	Downhole packers, landing nipples, tubing hangers, safety control valves, pump shafts, tool joints, wellhead fasteners
Offshore & Marine Engineering	Seawater cooling pressure vessels, subsea connectors, offshore pump components, marine high-strength bolts & studs
High-Pressure Chemical Processing	Acid medium high-pressure reactors, mixed acid transfer piping, pickling equipment, heavy-duty corrosion-resistant flanges
Energy & Power Equipment	High-temperature pressure fittings, flue gas desulfurization high-load internal supports, waste acid treatment hardware
Precision Heavy-Duty Fasteners	Superalloy bolts, nuts, studs and threaded components for extreme corrosion & high tensile load service

Material Selection Guidance

Service Condition	Recommended Grade	Selection Rationale
Sour crude & natural gas downhole high-pressure service	Alloy 925 UNS N09925	NACE & API certified, anti-SSC & anti-SCC performance, ultra-high yield strength for downhole load-bearing components
Offshore seawater, brine long-term pressurized operation	Alloy 925 UNS N09925	High Mo-Ni composition prevents pitting & crevice corrosion, combines structural strength with marine corrosion resistance
High-pressure mixed oxidizing/reducing acid process equipment	Alloy 925 UNS N09925	Cr-Mo-Cu multi-alloy system resists both acid types simultaneously, meets pressure vessel design strength requirements
Heavy-duty threaded fasteners under combined tension & corrosive media	Alloy 925 UNS N09925	Aging treatment achieves superior tensile strength, avoids fastener fracture and corrosion failure in harsh industrial environments

C&N’s Product Supply Scope & Packaging Standards

Item	Standard Supply Package
Available Product Range	Hot/cold rolled plates, coils, seamless tubes, solid & bored round bars, flat bars, open/closed die forgings, wire rods, custom machined blanks
Packaging Solutions	Sealed moisture-proof plastic wrapping, reinforced steel strapping, export fumigated plywood cases, standard ISPM pallet packaging
Product Marking	Alloy grade UNS N09925, dimensional specifications, heat lot number, production batch, theoretical net weight, permanent material stamping
Accompanying Documentation	Complete original Mill Test Certificates, third-party chemical & mechanical test reports, NDT ultrasonic/spectral inspection records, full product traceability files

Alloy 925 (UNS N09925 / Incoloy 925) is a premium precipitation-hardening nickel alloy engineered for the world’s most demanding high-pressure, high-temperature and sour corrosive industrial environments. Its unique Ti-Al strengthened matrix delivers unmatched combination of ultra-high mechanical strength and universal resistance to chloride stress cracking, sulfide stress cracking, pitting, crevice and mixed acid corrosion. Fully certified for oilfield sour service and pressure vessel applications, it is the optimal CRA material for oil & gas downhole hardware, offshore marine equipment and heavy-duty chemical pressure components. C&N provide custom machining for non-standard dimensions, and all Alloy 925 deliveries are supported by full authoritative inspection documentation to satisfy global API, NACE and ASME project acceptance criteria.If you need, contact us now！