904l stainless steel vs super duplex: what is the difference?
Leave a message
904l stainless steel vs super duplex：Composition
| Characteristic | 904L Stainless Steel (Super Austenitic) | Super Duplex Stainless Steel (e.g., 2507/2205) |
|---|---|---|
| Main Alloying Elements | High nickel (23-28%), molybdenum (4-5%), copper (1-2%) | Nickel (5-8%), molybdenum (3-4%), nitrogen (0.2-0.3%) |
| Microstructure | Single austenitic phase | Ferrite-austenite duplex structure (≈50% each) |
| Density | 8.0 g/cm³ (higher) | 7.8 g/cm³ (lower) |
904l stainless steel vs super duplex： Mechanical Properties
Strength
Super Duplex: Yield strength ≈ 450-550 MPa (e.g., 2507), twice that of 904L (≈220 MPa).
904L: Higher ductility (elongation up to 35%) for complex forming.
Corrosion Resistance
Uniform Corrosion: 904L excels in sulfuric/phosphoric acid (e.g., corrosion rate < 0.1 mm/year in 50% H₂SO₄).
Localized Corrosion: Super duplex has higher PREN (e.g., 2507 PREN ≈40), offering superior resistance to chloride pitting (critical pitting temperature 20-30°C higher than 904L in 3.5% NaCl).
Stress Corrosion: Duplex steel is less prone to hydrogen embrittlement in H₂S environments.
High-Temperature Performance
904L: Stable up to 600°C for long-term use.
Super duplex: Limited to ≤300°C due to σ-phase embrittlement risk above 500°C.
904l stainless steel vs super duplex：Applications
| Industry | 904L Stainless Steel | Super Duplex Stainless Steel |
|---|---|---|
| Chemical | Sulfuric acid tanks, fertilizer reactors | Chloride-containing pipelines, seawater heat exchangers |
| Energy | Flue gas desulfurization, waste incineration | Offshore drilling platforms, nuclear condensers |
| Environmental | Acid wastewater treatment systems | Paper bleaching equipment, pharmaceutical machinery |
| Construction | Coastal-area facades (salt fog resistance) | High-strength structural components (e.g., bridge cables) |
904l stainless steel vs super duplex：Welding:
904L: Requires strict heat input control to avoid hot cracking.
Super duplex: Needs rapid cooling to maintain duplex phase balance.
904l stainless steel vs super duplex：price
Super duplex is 10-20% more expensive due to nitrogen alloying and stricter processing.
Selection suggestions
Select 904L: high ductility, resistance to sulfuric acid/phosphoric acid corrosion, and temperature ≤600℃.
Select super duplex steel: high strength, resistance to chloride ion corrosion, and temperature ≤300℃.
