Nickel Based Alloy 3

[79ron79]

What is the minimum amount of Nickel content for an alloy to be considered a Nickel Based Alloy? This question came up on API 510 examination. Also please provide the source for this information if possible.
Thanks
Ron

 

[XL83NL]

Doesnt it depend on other alloying elements? Ive always believed that in nickel alloys, nickel is the main element within the composition, i.e. nickel has the highest percentage when looking at the chemical analysis.
Not sure though on the above, but that's what Ive understood so far.

 

[tbuelna]

79ron79-

Excellent question.

The alloys that I have commonly heard referred to as "nickel alloys", such as Hastelloy, Inconel, Haynes 230, etc, do have greater than 50% Ni content. Another good example is A286 alloy, which is corrosion/heat resistant but is considered an "iron-based alloy" due to an iron content above 50%. Here's what AR-MMPDS-01 has to say about A286: "Composition — The complex-base alloys comprising this group range from those in which iron is considered the base element to those which border on the nickel-base alloys. All of them contain sufficient alloying elements to place them in the “Superalloy” category, yet contain enough iron to reduce their cost considerably."

On the other hand, there is HS188 (Haynes 188) which is considered a "cobalt alloy", but only has a Co content of about 39%.

It would seem that to be considered a "nickel alloy" the Ni content percentage would just need to be greater than any other element.

Hope that helps.
Terry

 

[XL83NL]

I think my first reply isnt fully correct, but how would you clarify that e.g. UNS N08800/08810/08811 is a nickel based alloy (per ASTM spec B407), while it has more Fe than Irobn?

 

[TVP]

ASTM uses the title "Standard Specification for Nickel-Iron-Chromium Alloy" which is also how Special Metals describes it in their Publication Number SMC-047:

http://www.specialmetals.com/documents/Incoloy alloys 800H 800HT.pdf

metengr or EdStainless are more knowledgeable than I on the exact requirements within the ASTM system of when an alloy qualifies as nickel-base, iron-base, etc.

 

[Maui]

While it is a very versatile element, the majority of nickel is used as an alloy addition to stainless steels:

http://www.nickelinstitute.org/NickelUseInSociety/AboutNickel/WhereWhyNickelIsUsed.aspx

Stainless steels in the high-chromium, high-nickel ranges merge into other groups of heat resisting alloys. Where their iron content falls below approximately 50%, they are assigned to other alloy classifications because they cease to be considered stainless steels. This is generally considered to be the tipping point where a transition from ferrous-based to nickel-based alloys occurs - when the alloy contains less than 50% iron and the next most prevalent element is nickel.

Others may have a different perspective, but this has been my understanding.

Maui

http://www.EngineeringMetallurgy.com

 

[79ron79]

Excellent answers that all make sense. The options on the exam question were 20%,30%,40% and 50%. Any thoughts on that?

 

[arunmrao]

In my limited opinion, 50% is the tipping point for an alloy to be classified as XXX rich alloy.

 

[metengr]

ASME is currently working to re-classify certain ferrous and nonferrous alloy systems. Do not confuse this with nickel-base alloy systems. For Ni-base alloys, it would be nickel as the majority element, even if below 50% in comparison to other alloy additions.

 

[EdStainless]

The modern definition is to use the element that is the greatest content as the 'base'.
So AL-6XN is 48% Fe, it is Fe based.
Alloy 33 is 33% Cr, but nothing else is greater, so it is Cr based.

In the old days they used the 50% rule for being Fe based and hence gave AL-6XN a N UNS number.
This is not how it is done today.

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[XL83NL]

Thats what I meant Ed (just noticed my 2nd reply has a typo - Fe should be Ni).
Is this the reasoning why e.g. 800(H/HT) alloys are defined as nickel alloys under B31.3 table A-1?

 

[EdStainless]

The guys at Inco felt that the dominant element should define, even when ASTM/ASME did not.
They labeled alloys as Inconel if the major element was Ni, and Incoloy if it was Fe.
However many of the Incoloy grades are less than 50% Fe and so they were grouped with Ni based alloys back when.
They really are Fe based alloys.

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[tbuelna]

Here's a story that is somewhat relevant. I recently did some design work on a LOx/LH2 propellant duct system for a rocket. Per current industry practice the ducts were designed primarily of 718 Inconel. The initial engineering drawings were released with the BOM listing the material description as "Inconel 718" followed by the appropriate material specification (AMS 5664, etc). But later the design engineering group received instructions to change all of these BOM callouts from "Inconel 718" to "Nickel Alloy 718". I never found out what the reason was for making this change. The only thing I can think of is that Inconel is a trade name, and using it implies the material must be sourced from one particular supplier (INCO). Even though industry technical references like MMPDS use the term Inconel in a generic sense for these alloys, apparently the practice is not universally accepted.

Regards,
Terry

 

[XL83NL]

I just encountered the same thing, tbuelna, where a sub-supplier asked us if all the UNS N10276 components on our BOM of the isometric had to be Hastelloy.
At first I got scared, thinking he doesnt know *^&% what he's talking bout, but after some explanation, I found it was actually a pretty good statement.
Just like you implied, putting Hastelloy C-276 on the BOM simply restricts one to use Haynes' C-276 alloy, because of the trademark/-name.
From now on I simply call all alloys alloys, followed by their UNS number.

 

[TVP]

Terry,

As XL83NL noted and you already surmised, Inconel, Hastelloy, etc. are tradenames, and thus including them on drawing specifications restricts the sourcing of the material. Specific to Alloy 718, there are 5 different melt sources for this alloy in the USA alone (Special Metals, Cartech, ATI Allvac, Electralloy, Universal Stainless).

 

[metman]

Excellent answers that all make sense. The options on the exam question were 20%,30%,40% and 50%. Any thoughts on that?

My 2 cents worth is that the question is wrong. It is obviously ambiguous but probably the test composer(s) thought the correct answewr was 50%.

I like meteng and Edstainless take the best but predominent is not a number so that does not satisfy the test question.

Design for RELIABILITY, manufacturability, and maintainability

 

[EdStainless]

Given the answers I would also guess that 50% is what they were looking for, but that does not really make sense.
there are a number of alloys in use today that are called Ni alloys that are only 35% Ni, but they are also <50% Fe.

Bogus question for sure. This is one where you fill out the paperwork and request the documented solution and sources for the information. Hole their feet to the fire.

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[mrfailure]

Also note that ASTM E140 for hardness conversions defines "nickel and high-nickel" alloys as containing 50% Ni. I have seen people incorrectly assume that high-nickle means one can use the conversions for austenitic stainless steel microhardness, which is incorrect!

Aaron Tanzer

 

[tbuelna]

What I'd really like to know is why doesn't Muntz metal have a Muntz content greater than 50%?

 

[EdStainless]

How many Germans are in German silver?

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