Product Description
INCOLOY 27-7MO (UNS S31277) is an advanced 7% molybdenum super-austenitic stainless steel that offers superior corrosion resistance compared to conventional 6% molybdenum super-austenitic stainless steels. In many environments, INCOLOY 27-7MO provides resistance approaching that of much more highly alloyed materials. This premium alloy typically contains 27% nickel, 22% chromium, 7.2% molybdenum, and 0.34% nitrogen, creating a stable austenitic structure with exceptional performance in aggressive media.
The high molybdenum, chromium, and nitrogen content delivers excellent resistance to pitting and crevice corrosion. The nickel, nitrogen, and molybdenum provide resistance to reducing media, while the high chromium content offers resistance to oxidizing media. This balanced composition makes INCOLOY 27-7MO an ideal choice for mixed acid environments, especially those containing both oxidizing and reducing acids.
Applications
INCOLOY 27-7MO finds wide application across multiple industries requiring materials with exceptional corrosion resistance:
- Pollution Control: Particularly in flue gas desulfurization (FGD) systems for coal-fired power plants
- Power Generation: Components exposed to aggressive media
- Marine Industry: Excellent performance in seawater and brine environments
- Chemical Processing: Handling of aggressive acids and mixed acid solutions
- Pulp and Paper: Corrosion-resistant components in chemical pulping processes
- Oil and Gas: Wireline, armor wire, screens, and subsea banding for sour gas service
INCOLOY 27-7MO is available in various product forms including plate, sheet, rod, bar, wire rod, pipe, tube, and forging stock, offering versatility for diverse application requirements.
Standards
INCOLOY 27-7MO (UNS S31277) is covered by the following standards:
- Rod, Bar, Wire, and Forging Stock: ASTM A479/ASME SA479 (Bar)
- Plate, Sheet, and Strip: ASTM A240/ASME SA240
- Pipe and Tube: ASTM A213/ASME SA213 (Tube), ASTM A249/ASME SA249 (Tube), ASTM A312/ASME SA312 (Pipe)
- Other: ASTM A182/ASME SA182
Design stresses for ASME Boiler and Pressure Vessel Code construction are defined in ASME Code Case 2458.
Chemical Composition and Grade Comparison
INCOLOY 27-7MO is designated as UNS S31277. The table below shows the limiting chemical composition:
| Element | Content (wt %) |
|---|---|
| Nickel | 26.0-28.0 |
| Chromium | 20.5-23.0 |
| Molybdenum | 6.5-8.0 |
| Copper | 0.5-1.5 |
| Nitrogen | 0.3-0.4 |
| Iron | Balance |
| Manganese | 3.00 max. |
| Phosphorus | 0.03 max. |
| Sulfur | 0.01 max. |
| Silicon | 0.5 max. |
| Carbon | 0.020 max. |
INCOLOY 27-7MO offers superior corrosion resistance compared to 6% molybdenum super-austenitic stainless steels, with a Pitting Resistance Equivalency Number (PREN) of 43.0, significantly higher than similar alloys with lower molybdenum content.
Physical and Mechanical Properties
INCOLOY 27-7MO exhibits an optimum combination of strength and ductility compared to similar alloys.
| Property | Value |
|---|---|
| Ultimate Tensile Strength | 120 ksi (827 MPa) |
| Yield Strength (0.2%) | 60 ksi (414 MPa) |
| Elongation | 50% |
| Hardness, Rockwell B | 95 |
| Density | 8.02 g/cm³ (0.289 lb/in³) |
| Specific Heat | 454 J/kg°C (0.109 Btu/lb°F) |
| Electrical Resistivity | 100 μohm·cm (604 ohm·circ mil/ft) |
The alloy maintains good strength at elevated temperatures, with yield strength above 25 ksi (172 MPa) at 1000°F (538°C).
Corrosion Resistance
INCOLOY 27-7MO offers exceptional corrosion resistance in aggressive environments:
- Critical Pitting Temperature (CPT): >85°C (>185°F) per ASTM G48 Method C
- Critical Crevice Temperature (CCT): 45°C (113°F) per ASTM G48 Method D
- Superior resistance to corrosion in seawater and chloride-containing environments
- Excellent resistance to phosphoric, sulfuric, and hydrochloric acids
- Outstanding performance in flue gas desulfurization (FGD) service
Fabrication Properties
INCOLOY 27-7MO is readily fabricated using conventional techniques:
- Hot working temperature range: 1800-2100°F (980-1150°C)
- Annealing temperature: 2050-2150°F (1121-1177°C)
- Readily welded using conventional processes (GTAW, GMAW, SMAW, SAW, PAW)
- Easily machined in the annealed condition
Available Dimensions
FUSHUN METAL provides INCOLOY 27-7MO in a wide range of dimensions:
| Product Form | Dimension Range |
|---|---|
| Plate | Thickness: 3.0-100mm Width: 1000-3000mm Length: 2000-12000mm |
| Sheet | Thickness: 0.5-3.0mm Width: 1000-1500mm Length: 2000-6000mm |
| Rod/Bar | Diameter: 5-300mm Length: 2000-6000mm |
| Wire | Diameter: 0.1-12mm |
| Pipe/Tube | OD: 6-610mm Wall Thickness: 0.5-50mm Length: up to 12000mm |
| Forging Stock | Custom dimensions available upon request |
Performance in Challenging Environments
INCOLOY 27-7MO demonstrates outstanding performance in some of the most challenging industrial environments:
Seawater and Marine Applications
In tests conducted in flowing natural seawater at 30°C for 60 days, INCOLOY 27-7MO showed no crevice corrosion, outperforming many commonly used marine alloys including 316L stainless steel and 6% Mo super-austenitic stainless steel.
Acid Resistance
The alloy exhibits excellent resistance to various acids including hydrochloric, sulfuric, and phosphoric acids at different concentrations and temperatures. In many cases, its corrosion rate is below 5 mpy (0.13 mm/a), making it suitable for long-term service in aggressive chemical environments.
Flue Gas Desulfurization (FGD) Service
In simulated FGD environments (60% H₂SO₄ + 2.5% HCl + 0.2% HF + 0.5% flyash at 80°C), INCOLOY 27-7MO shows significantly better performance than typical 6% molybdenum super-austenitic stainless steels.
Sour Gas Service
INCOLOY 27-7MO demonstrates superior resistance to stress corrosion cracking in sour gas environments compared to lower-alloyed materials, making it suitable for demanding oil and gas applications.
Why Choose FUSHUN METAL for INCOLOY 27-7MO
When it comes to sourcing high-performance INCOLOY 27-7MO super-austenitic stainless steel, FUSHUN METAL stands as your premier supplier for several compelling reasons:
- Guaranteed Quality: We ensure all our INCOLOY 27-7MO products meet or exceed the specified chemical composition and mechanical properties, verified through rigorous testing and certification.
- Complete Product Range: From plate and sheet to pipe, tube, rod, bar, and wire forms, we offer INCOLOY 27-7MO in a comprehensive range of dimensions to suit your specific application requirements.
- Technical Expertise: Our metallurgical specialists can provide guidance on material selection, fabrication techniques, and corrosion resistance for your specific operating environment.
- Global Capabilities: With our extensive supply chain network, we can deliver INCOLOY 27-7MO products to customers worldwide with competitive lead times.
- Custom Solutions: We can provide custom-sized products and specialized processing to meet your exact specifications.
For your next project requiring the exceptional corrosion resistance and mechanical properties of INCOLOY 27-7MO, contact our team for a detailed discussion of your requirements. Our technical experts will work with you to determine the optimal material specifications for your application, ensuring long-term performance in even the most challenging environments.
