AL6XN Fasteners: The Definitive Guide to Super Austenitic Stainless Steel Bolts

When standard 316L stainless steel fasteners fail due to pitting, crevice corrosion, or stress corrosion cracking in harsh chloride environments, AL6XN enters the picture. This super austenitic stainless steel contains approximately 6% molybdenum and exhibits exceptional resistance to warm seawater, bleach, and acidic brines—making it the go‑to alloy for demanding marine, chemical, and oil & gas applications. RAYCHIN LIMITED, a specialist global manufacturer and supplier of high‑performance alloy fasteners, supplies the complete range of AL6XN bolts, studs, nuts, and custom parts, backed by full material certification and decades of metallurgical expertise.

1. What Is AL6XN Material?

What is AL6XN material? AL6XN (UNS N08367) is a low‑carbon, high‑nickel, high‑molybdenum super austenitic stainless steel. It was developed to bridge the gap between standard austenitic grades like 316L and expensive nickel‑base alloys like Hastelloy C‑276. The alloy's hallmark is its PREN (Pitting Resistance Equivalent Number) of approximately 44–46, which is roughly double that of 316L and significantly higher than duplex 2205. This makes AL6XN fasteners a cost‑effective solution for combating localized corrosion in chloride‑rich environments where 316L simply cannot survive.

2. AL6XN Chemical Composition

The AL6XN chemical composition is carefully balanced to maximize corrosion resistance while maintaining good formability and weldability. The nominal chemistry per ASTM A182 (UNS N08367) is presented below.

3. AL6XN Properties – Mechanical and Physical

AL6XN properties in the annealed condition combine good strength with outstanding corrosion resistance. Typical room‑temperature mechanical properties per ASTM A182 are:

• Tensile Strength: ≥ 655 MPa (95 ksi)
• Yield Strength (0.2% offset): ≥ 310 MPa (45 ksi)
• Elongation: ≥ 30%
• Hardness: ≤ 100 HRB

Key physical properties include a density of 8.06 g/cm³, melting range of 1320–1400°C, and a mean coefficient of thermal expansion of 16.4 µm/m·°C (20–100°C). The alloy is non‑magnetic in the annealed condition, with very low magnetic permeability.

4. AL6XN vs 6Mo Fasteners and Equivalent Grades

AL6XN vs 6Mo fasteners: AL6XN belongs to the 6% molybdenum (6Mo) super austenitic stainless steel family, which also includes alloys such as 254SMO (UNS S31254) and 1925hMo. All 6Mo alloys share a similar PREN range and are often specified interchangeably in seawater and chemical environments. The table below summarizes AL6XN equivalent grades.

All three alloys can be considered interchangeable for many fastener applications, although slight differences in chemistry and product availability may influence selection. RAYCHIN stocks AL6XN as our primary 6Mo alloy and can source the other grades upon request.

5. RAYCHIN's AL6XN Fastener Product Range

RAYCHIN LIMITED supplies the complete line of UNS N08367 fasteners for global seawater, chemical, and offshore applications:

• Hex bolts – ASME B18.2.1, DIN 931/933, M6–M48, 1/4″–2″
• Stud bolts and threaded rod – ASME B16.5, DIN 976, M6–M64, 1/4″–2‑1/2″
• Socket head cap screws – ASME B18.3
• Heavy hex nuts and washers
• Custom parts – per your drawings; flanged bolts, stepped studs

All products are solution‑annealed, with full material certification, PMI testing, and EN 10204 3.1 as standard (3.2 available).