The AL-6XN^® alloy carries the Unified Numbering System (UNS) designation of N08367. AL-6XN alloy is an austenitic stainless steel alloy with high nickel and molybdenum contents plus nitrogen. The alloy was a further development of the Allegheny Ludlum alloy AL-6X. The addition of nitrogen provided the alloy with improved resistance to pitting and crevice corrosion, a greater resistance to localized corrosion in oxidizing chlorides and reducing solutions plus higher strength. Nitrogen also helps to significantly reduce the potential formation of harmful secondary phases during welding.

AL-6XN alloy has a face-centered cubic crystal structure similar to other austenitic stainless steels. The alloy is non-magnetic and its magnetic permeability remains low even after severe cold forming.

Alloy Development
Over the years corrosion resistance in chloride environments have forced the change of the more popular 18%-8% Ni austenitic stainless steels. Corrosion resistance, weld ability and strength of the austenitic alloys were improved by changing the basic chemical composition to meet the more demanding applications.

• Molybdenum was added to improve corrosion resistance in chloride environments.
  
• Carbon was reduced to minimize sensitization during welding.
  
• Nitrogen was added to compensate for the reduced strength of the "L" grades, improve phase stability and together with chromium and molybdenum, improve pitting resistance.
  
• Chromium was increased to improve oxidation resistance.
  
• Nickel was added to stabilize the austenitic crystal structure and, at higher contents, improve stress-corrosion cracking resistance and general corrosion resistance in reducing environments.

Chemical Composition of AL-6XN Alloy

The high strength and corrosion resistance of the AL-6XN alloy make it a better choice than the conventional duplex stainless steels and a cost effective alternative to more expensive nickel-based alloys in applications where excellent formability, weldability, strength and corrosion resistance are essential. It is a cost effective alternative to less expensive stainless steels that do not have the strength or corrosion resistance to maximize life cycles.

AL-6XN alloy has exceptional resistance to chloride corrosion, pitting, crevice corrosion, stress corrosion cracking, and excellent general corrosion resistance to various acid, alkalis and salt solutions.