Share:
More Articles
Quote, Buy, Track!
We make it easy to get instant pricing and purchase your metal at the click of a button. Track your order progress, get notified when it ships, and follow your shipment online until it’s delivered. It’s that easy!
In response to the need for a cost-effective alloy that could resist brackish water or seawater environments, stainless alloys with even higher levels of chromium and molybdenum were developed. This need resulted in the development and introduction of AL-6X™ in the early 1970s by ATI.
One significant problem with AL-6X was that the product forms and sizes were limited due to metallurgical reasons. The alloy’s high chromium and molybdenum content rendered AL-6X susceptible to forming sigma phases upon slow cooling between 1000°F – 2100°F. Flat products thicker than 0.1875″ could not be cooled quickly enough to prevent this formation, which would hamper the material’s corrosion resistance and toughness.
Nitrogen was found to be effective in retarding the formation of sigma phase and enhanced the effects of chromium and molybdenum by improving resistance to pitting, crevice corrosion, and stress-corrosion cracking. The figure below shows the times and temperatures that AL-6X and AL-6XN® tend to form sigma phase. Therefore, AL-6XN® was developed as an improvement over AL-6X. Both alloys have the same elemental composition except AL-6XN® contained an intentional addition of 0.18% – 0.25% N.
Sigma Phase Time Temperature Transformation Curves
In 1977, Avesta, now Outokumpu, developed their own super austenitic alloy, 254SMO®, but AL-6XN® became the more widely used and accepted alloy due to a market development relationship with Rolled Alloys. Rolled Alloys played an instrumental role in developing the sources to ensure the supply of all product forms and maintain an inventory of these products in various sizes.
In terms of performance, AL-6XN® is code-rated up to 800°F per ASME BPVC Section VIII Div 1, while 254SMO is approved only up to 750°F. The higher nickel content of AL-6XN® improves general corrosion resistance and makes it more resistant to sigma formation. With a low copper content, AL-6XN® also exhibits improved chloride pitting resistance, which is preferred by certain users for environmental reasons. Independent studies have consistently shown that AL-6XN® outperforms other super austenitic alloys in terms of seawater pitting and crevice corrosion resistance. For a more detailed comparison, check out a comparison between AL-6XN® and 254 SMO below.
AL-6XN® has various use cases across different industries. It is known for its exceptional performance in coal-fired flue gas desulfurization (FGD) systems and seawater applications in the power industry. Other sectors have also benefited from AL-6XN®’s chloride and acid resistance, leading to increased usage in the chemical process industry (CPI). Additionally, it has shown good resistance to microbiologically influenced corrosion (MIC). The food and pharmaceutical industries have used AL-6XN® for decades in situations where 316/316L was not sufficient. AL-6XN® is also utilized in offshore oil and gas environments, pulp bleaching applications, service water piping, LNG transportation and storage, as well as reverse osmosis desalination systems.
ATI is the only manufacturer with a long-standing history of superior performance, quality, and expertise in producing AL-6XN® (N08637). While other producers have attempted to supply substitute materials that meet the UNS number’s broad chemistry range, they sometimes offer different levels of performance or integrity. Rolled Alloys exclusively stocks genuine AL-6XN® products produced to the highest quality standards.
Buy Online Anytime
Our dashboard makes it even easier to shop online anytime from anywhere. Quote, buy, and track 24 hours a day.
Cut To Size Processing
We offer a range of processing services to provide material ready for you to begin machining or fabricating upon arrival. See our full list of capabilities for tolerances or chat with a sales rep about which processing method would be best suited for your order.
E-Services Stocking Programs
Our e-service stocking programs put you in the driver seat by using our customized purchasing options to order your recurring material with ease. Whether you have an internal process for purchasing and receiving in place or maybe looking for solutions to become more efficient, we have a program that will work for you.
New Bar Stock Available
New Round and Flat Bar Products in Stock at Rolled Alloys
New Rolled Alloys Facility in Ohio
Rolled Alloys announces new facility located in Toledo, Ohio.
Reasons Why Duplex Stainless Steels are Replacing the 300 Series
Explore the four key benefits of duplex stainless steel: high strength, superior corrosion resistance, ease of fabrication, and cost-effectiveness. Understand why 2205 is favored over 304/304L and 316/316L for industrial applications.
Understanding P-Numbers and F-Numbers in Welding
P-Numbers and F-Numbers are essential classifications in the welding industry, particularly for projects that follow ASME codes and…
Chicago Oktobarfest 2024
Join us for food, demo’s and prizes on October 11th from 11 a.m to 3:30 p.m at 711 Phoenix Lake Ave, Streamwood, Illinois.
High Temperature Strength – An Explanation of Creep and Rupture
Learn how metal strength at high temperatures differs from room temperature in this comprehensive guide. Discover the importance…
