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Hydrogen embrittlement when plating Aermet 100

Q. Hi,

I would like to know your opinion on plating ultra high strength high alloy steels like Aermet 100.

Most specs require to use test specimens of AISI 4340 for hydrogen embrittlement testing, which is a low alloy steel. When plating steels like Aermet, I doubt that the hydrogen embrittlement testing bars required per spec are representative. On the other hand one could say that the process is controlled per spec by the tests using AISI 4340. But when you're talking about production control testing, the non-representativeness would be a problem I guess.

I was asked for advise on putting a cad plating specification (AMSQQP416) on drawing by our design dept.

I work at an Aerospace company with design responsibility as you'd probably guessed.

Looking forward to your replies.

Best regards,

Jeroen Visser

Jeroen Visser
Chief of Plating dept. - Helmond, The Netherlands
August 29, 2011

A. Jeroen,

Most of the hydrogen embrittlement test requirements have been developed for fasteners, such as ISO 15330, NASM 1312-5, etc. ASTM F519 is really the one exception, but as you already noted, it specifies the use of a 4340 steel specimen. However, section 1.3 states the following:

Components with ultimate strengths higher than 260 - 280 ksi may not be represented by the baseline. In such cases, the cognizant engineering authority shall determine the need for manufacturing specimens from the specific material and heat treat condition of the component. Deviations from the baseline shall be reported as required by section 12.1.2.

I would suggest that you follow the requirements of ASTM F519, but use specimens fabricated from production-representative material, i.e., Aermet 100. Here is an example of some testing done by the US Air Force that specifically used Aermet 100 specimens for ASTM F519 testing:

www.serdp.org/content/download/8646/105487/file/WP-1405-FR(2).pdf

Toby Padfield
Automotive module & component supplier - Michigan, USA

Hi Toby,

Thank's a lot for your reply. I will study the document in your link and will get back on it later.

Besides the cad plating spec I was asked for advise on electroless nickel plating on Aermet 100. I contacted a customer for cad plating and was advised to call out their spec on the drawings, since AMSQQP416 is not quite suitable for ultra high strength high alloy steels. Their spec requires high current density cad plating for facilitating embrittlement relief baking and also requires tape testing on each part, since adhesion is also an issue with this material. However AISI 4340 is their requirement as well for the hydrogen embrittlement test specimens.

This also brings up my further doubts on representativeness of test panel material called out in most specs for corrosion resistance and adhesion testing, AISI 4130.

For my company I am the author of the hydrogen embrittlement testing procedure and I specifically mentioned the section in ASTM F519 you refer to that the procedure only applies for baseline geometry AISI 4340 specimens.

I was told that specimens made of Aermet 100 and qualified per ASTM F519 are also hard and expensive to get in the market.

I will discuss this with our design engineering dept.

Jeroen Visser
- Helmond, The Netherlands

A. I agree with Toby. I'll just add that ASTM F519 tensile testing specimens are widely used and are available in 4340 from various suppliers. That will not be the case with Aermet 100, so you will need to plan to machine your own specimens per the dimensions in ASTM F519.

Jon Barrows, MSF, EHSSC
GOAD Company

Independence, Missouri

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