×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Nickel Alloy vs Stainless Steel
2

Nickel Alloy vs Stainless Steel

RE: Nickel Alloy vs Stainless Steel

This has been moved a few times over the years. Notice that 825 and AL-6XN have "N" UNS numbers. At one time an alloy that was not 50% Fe was not stainless.
Today the rule is based on the dominant element. So if the alloy is 45% Fe and less of any other specific element then it is a steel.
Maybe the best example is alloy 33 (R20033). It is considered a Cr based alloy because it is 33% Cr and only 31% Ni, and then after a few other elements bal Fe (works out to be about 32%).
https://vdm-metals.com/fileadmin/user_upload/Downl...

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Nickel Alloy vs Stainless Steel

(OP)
Thanks for that Ed.

RE: Nickel Alloy vs Stainless Steel

(OP)
@EdStainless, but for Alloy 825 the Fe content is around 22% and the Ni can be as high as 46%, but it is considered a higher austenitic stainless steel?!

RE: Nickel Alloy vs Stainless Steel

What is the actual problem with the definition? Is it trying to work out the tables of ISO 15156-3, because everything with >= 10.5% Cr is a "stainless steel" for the purposes of that standard?

Steve Jones
Corrosion Management Consultant

www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

RE: Nickel Alloy vs Stainless Steel

(OP)
@SJones, I was trying to explain to a colleague that Alloy 825 is a higher austenitic stainless steel not a nickel alloy and the UNS number does not always reflect that - a clear example is the 904L (in addition to the examples given by @EdStainless) - then he asked the question I had posted - How can we decide from the compositional point of view if an alloy is a stainless steel or a nickel alloy?

RE: Nickel Alloy vs Stainless Steel

Special Metals does it for you, Incoloy is Fe based and Inconel is Ni based.
Seriously though, 825 is an attempt at pushing enough Ni in a SS to get beyond the CSCC range, and still keep the alloy stable. There are plenty of other SS grades with better pitting corrosion resistance than 825 as it has modest Cr and Mo content (but this does help phase stability).
Most of the true Ni alloys have little Fe, usually <10%. There are some odd balls such as X or 718, but you have to think of corrosion resistant alloys separately from high temperature grades.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Nickel Alloy vs Stainless Steel

If you are in oil & gas, just stick to the ISO 15156-3 classification of N08825: solid solution nickel based alloy. It saves a lot of mental wrangling.

Steve Jones
Corrosion Management Consultant

www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

RE: Nickel Alloy vs Stainless Steel

(OP)
@EdStainless and @SJones, thanks for the replies.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

The Low-Code Digital Transformation Guide
Change the way you develop apps and, in turn, change the way your business operates and engages with customers, leading to new channels of revenue. This ebook is the culmination of 14 years of experience with 4,000 customers that have all transformed their business through low-code development. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close