RAYCHIN LIMITED

Expertise Across the Full AL6XN Fastener Range

Manufacturing Standards for AL6XN Fasteners

RAYCHIN LIMITED manufactures AL6XN fasteners to the following national and international standards, ensuring full compliance for projects worldwide. Both standard and non-standard custom configurations are available.

International Standards & Global Designations for AL6XN Fasteners

To serve clients worldwide, RAYCHIN LIMITED manufactures AL6XN fasteners from material conforming to the following national and international specifications. This ensures full compliance for projects in the Americas, Europe, Asia, and the Middle East.

UNS N08367 AL6XN ASTM B691 ASTM B688 NACE MR0175 1.4501

Chemical Composition (Weight %) – AL6XN Super Austenitic Stainless Steel

Our AL6XN bolts, nuts, screws, washers, stud bolts and threaded rods are produced from melts that strictly conform to the limits below per ASTM B691 / UNS N08367. The high levels of chromium, nickel, molybdenum, and nitrogen provide exceptional resistance to pitting and crevice corrosion, with a Pitting Resistance Equivalent (PRE) typically exceeding 45.

Expert note: The high molybdenum (6-7%) and nitrogen (0.18-0.25%) content gives AL6XN a PRE value exceeding 45, providing resistance to pitting and crevice corrosion in seawater and other chloride environments that is far superior to 316L (PRE≈24) and 317L (PRE≈29). The high nickel content (23.5-25.5%) provides exceptional resistance to chloride stress corrosion cracking. This makes AL6XN fasteners ideal for offshore, desalination, and FGD applications. The material also meets NACE MR0175 requirements for sour service in oil and gas environments.

Complete Mechanical Properties of AL6XN Fasteners (Solution Annealed Condition)

AL6XN fasteners are supplied in the solution annealed condition (1100–1200°C followed by water quenching). The data below represent minimum values per ASTM B691 and EN 10088-3.

Mechanical Properties at Room Temperature

High Temperature Performance of AL6XN Fasteners

AL6XN maintains good mechanical properties at elevated temperatures, with a suggested operating range from -196°C to 427°C (-320°F to 800°F). It should not be exposed to temperatures above 427°C for prolonged periods due to metallurgical stability considerations. For continuous service, the maximum operating temperature is approximately 400°C.

Temperature-Dependent Yield Strength (0.2% Offset)

Note: AL6XN is not recommended for applications requiring prolonged exposure above 427°C (800°F). The material maintains excellent oxidation resistance up to 500°C and retains good impact strength at cryogenic temperatures down to -196°C.

Thermal Stability Limits

Corrosion Resistance of AL6XN Fasteners

AL6XN was specifically developed for use in aggressive chloride-bearing environments. Its high molybdenum (6-7%), chromium (20-22%), nickel (23.5-25.5%), and nitrogen (0.18-0.25%) content provide exceptional resistance to localized corrosion, including pitting, crevice corrosion, and stress corrosion cracking. The material is frequently used as a cost-effective alternative to nickel-based alloys such as C-276 in moderately corrosive conditions.

Pitting and Crevice Corrosion Resistance

The Pitting Resistance Equivalent (PRE) for AL6XN is typically >45, calculated as PRE = %Cr + 3.3 × %Mo + 16 × %N. This value is significantly higher than 316L (PRE≈24) and 317L (PRE≈29), and even exceeds that of 6% molybdenum alloys like 254SMO. Tests in natural seawater have shown that AL6XN can be exposed for prolonged periods without suffering crevice corrosion. In chloride environments with concentrations of 10,000-70,000 ppm and temperatures of 50-68°C, AL6XN demonstrates virtually no pitting or crevice corrosion.

Stress Corrosion Cracking (SCC) Resistance

Ordinary austenitic steels (304, 316) are prone to chloride stress corrosion cracking at temperatures above 60°C. AL6XN, with its high nickel content (24-25%) and molybdenum (6-7%), exhibits excellent resistance to SCC. In boiling 45% MgCl₂ solution, AL6XN shows no cracking after 1000 hours, while 316 fails in less than 100 hours. The material is approved per NACE MR0175/ISO 15156 for sour service applications in oilfield equipment.

Critical Corrosion Considerations

• PRE >45: The high Pitting Resistance Equivalent ensures outstanding performance in seawater and aggressive chemical environments. With 6-7% molybdenum content, AL6XN provides exceptional resistance to chloride-induced pitting and crevice corrosion.
• NACE MR0175 Compliance: AL6XN is qualified for sour service (sulfide stress cracking resistance) in oilfield equipment per NACE MR0175/ISO 15156.
• Temperature Limitations: Maximum service temperature for corrosion applications is approximately 400°C. Avoid exposure to temperatures above 427°C for prolonged periods.
• Galvanic Corrosion: When paired with lower-grade materials, galvanic corrosion should be considered. AL6XN is cathodic to most other stainless steels. Proper isolation may be required in mixed-material assemblies.
• Acid Resistance: In sulfuric acid containing chlorides, AL6XN offers maximum resistance to localized corrosion. In hydrochloric acid, AL6XN can be used in diluted concentrations at moderate temperatures.
• Comparison to Duplex: With higher nickel and molybdenum content than Duplex 2205 and Super Duplex 2507, AL6XN delivers better corrosion resistance in highly aggressive chloride environments.

Corrosion Engineering Note: For critical applications in aggressive environments, RAYCHIN LIMITED can provide passivation, specialized coatings (Xylan, PTFE, silver plating), or recommend optimal heat treatment conditions. Third-party corrosion testing per ASTM G31, G48, or G61 available upon request. NACE MR0175 compliant AL6XN fasteners available for sour service applications. In many applications, AL6XN serves as a cost-effective substitute for high nickel alloys such as C-276 in moderately corrosive conditions.

Why RAYCHIN LIMITED – The AL6XN Fastener Authority