Austenitic Stainless Steel 654SMO 丨S32654
654SMO (UNS S32654, W.Nr. 1.4652) is an ultra-high alloyed super austenitic stainless steel specifically engineered for the most aggressive chloride-containing environments. With approximately 24% nickel, 23% chromium, 7.3% molybdenum, and high nitrogen content, it delivers exceptional resistance to pitting, crevice corrosion, and chloride stress corrosion cracking. Its PREN exceeds 56, making it one of the world’s most corrosion-resistant commercially available stainless steels for seawater, offshore, desalination, and chemical processing applications.
Austenitic Stainless Steel 654SMO (UNS S32654, W.Nr. 1.4652)
654SMO (UNS S32654, W.Nr. 1.4652) is a super austenitic stainless steel designed for applications where conventional stainless steels, duplex stainless steels, and even many nickel alloys cannot provide sufficient corrosion resistance. The alloy combines extremely high chromium, molybdenum, and nitrogen contents to achieve outstanding localized corrosion resistance while maintaining excellent toughness, weldability, and fabrication characteristics.
Its extremely high Pitting Resistance Equivalent Number (PREN >56) makes it one of the preferred materials for seawater systems, desalination plants, flue gas desulfurization systems, offshore platforms, and chemical processing facilities.
654SMO At a Glance
| Key Attribute | Value |
|---|---|
| Material | 654SMO Stainless Steel |
| UNS Number | S32654 |
| Material Type | Super Austenitic Stainless Steel |
| Microstructure | Austenitic |
| PREN | >56 |
| Density | 8.0 g/cm³ |
| Main Advantage | Exceptional Seawater Corrosion Resistance |
| Typical Service Temperature | -196°C to 400°C |
| Main Industries | Offshore, Desalination, Chemical Processing |
| Comparable Grade | 254SMO, Alloy 625 |
Features of 654SMO
- Outstanding pitting corrosion resistance
- Excellent crevice corrosion resistance
- Superior chloride stress corrosion cracking resistance
- PREN exceeding 56
- Exceptional seawater resistance
- Excellent resistance to oxidizing acids
- High nitrogen strengthening
- Excellent weldability
- Outstanding toughness at cryogenic temperatures
- Long service life in highly aggressive environments
Chemical Composition of 654SMO
| Element | Content (%) |
|---|---|
| Chromium (Cr) | 24.0 – 25.0 |
| Nickel (Ni) | 21.0 – 24.0 |
| Molybdenum (Mo) | 7.0 – 8.0 |
| Nitrogen (N) | 0.45 – 0.55 |
| Manganese (Mn) | 3.0 – 5.0 |
| Copper (Cu) | 0.3 – 1.0 |
| Silicon (Si) | ≤0.5 |
| Carbon (C) | ≤0.02 |
| Phosphorus (P) | ≤0.03 |
| Sulfur (S) | ≤0.01 |
| Iron (Fe) | Balance |
Physical Properties of 654SMO
| Property | Value |
|---|---|
| Density | 8.00 g/cm³ |
| Melting Range | 1320–1390°C |
| Electrical Resistivity | 0.95 μΩ·m |
| Thermal Conductivity | 11.5 W/m·K |
| Specific Heat Capacity | 500 J/kg·K |
| Modulus of Elasticity | 195 GPa |
Mechanical Properties
Solution Annealed
| Property | Typical Value |
|---|---|
| Tensile Strength | ≥750 MPa |
| Yield Strength (0.2%) | ≥430 MPa |
| Elongation | ≥40% |
| Hardness | ≤250 HB |
Corrosion Resistance
654SMO is one of the highest-performing commercial stainless steels for corrosion resistance.
It provides:
- Exceptional seawater resistance
- Outstanding pitting resistance
- Excellent crevice corrosion resistance
- Superior chloride SCC resistance
- Excellent resistance to acidic chloride solutions
- Excellent resistance in FGD systems
- Outstanding performance in desalination plants
High Temperature Performance
Recommended continuous service:
- Cryogenic service
- Ambient temperatures
- Up to approximately 400°C
Not recommended for prolonged exposure within the sigma phase formation temperature range (approximately 600–950°C).
Available Forms
J&A Alloy supplies:
- Round Bar
- Forged Bar
- Plate
- Sheet
- Coil
- Pipe
- Tube
- Flanges
- Forgings
- Wire
- Fittings
- Custom Machined Parts
Applications of 654SMO
Offshore
- Offshore platforms
- Subsea piping
- Seawater systems
Desalination
- Reverse osmosis equipment
- Evaporators
- Brine handling systems
Chemical Processing
- Heat exchangers
- Pressure vessels
- Acid handling equipment
Marine
- Pump shafts
- Valves
- Fasteners
- Propeller components
Environmental
- Flue Gas Desulfurization
- Wastewater treatment
654SMO vs Other Stainless Steels
| Grade | PREN | Main Advantage |
|---|---|---|
| 654SMO | >56 | Maximum Corrosion Resistance |
| 254SMO | 43–45 | Excellent Seawater Resistance |
| 2205 Duplex | 35 | Higher Strength |
| 316L | 24 | General Industrial Use |
Welding & Fabrication
Recommended welding methods:
- GTAW (TIG)
- GMAW (MIG)
- Plasma Welding
- SMAW
Use matching super-austenitic or nickel alloy filler metals.
Post-weld heat treatment is generally unnecessary.
Standards & Equivalent Grades
| Standard | Designation |
|---|---|
| UNS | S32654 |
| EN/W.Nr. | 1.4652 |
| Material Type | Super Austenitic Stainless Steel |
| ASTM Plate | A240 UNS S32654 |
| ASTM Bar | A479 UNS S32654 |
| NACE | MR0175 / ISO 15156 |
Frequently Asked Questions
What is 654SMO?
654SMO is an ultra-high alloy super austenitic stainless steel designed for the most severe chloride-containing environments.
What is the UNS number?
UNS S32654.
Is 654SMO better than 254SMO?
Yes. 654SMO offers significantly higher pitting and crevice corrosion resistance due to its higher chromium, molybdenum, and nitrogen contents.
What is the PREN of 654SMO?
Typically greater than 56.
Can 654SMO be used in seawater?
Yes. It is specifically developed for long-term seawater service.
Is 654SMO magnetic?
No. It remains essentially non-magnetic in the solution annealed condition.
Can 654SMO be welded?
Yes. It exhibits excellent weldability using conventional stainless steel welding processes.
What industries use 654SMO?
Offshore oil & gas, desalination, marine engineering, chemical processing, power generation, and environmental protection.
Why Choose J&A Alloy
Professional Stainless Steel Supplier
J&A Alloy specializes in supplying super austenitic, duplex, super duplex, precipitation-hardening stainless steels and nickel alloys.
Quality Assurance
- PMI Testing
- Chemical Analysis
- Mechanical Testing
- Corrosion Testing
- Ultrasonic Inspection
International Standards
- ASTM
- ASME
- EN
- NACE
- ISO 9001
- EN 10204 3.1 / 3.2 Certification
Processing Services
- Precision Cutting
- CNC Machining
- Forging
- Heat Treatment
- Custom Fabrication
Global Supply
Reliable worldwide supply for offshore, marine, desalination, and chemical industries.
