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Post-plating heat treatment + hydrogen embrittlement relief baking?

A discussion started in 2011 and continuing through 2020 so far.
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November 29, 2011

Q. My customer is asking for Hydrogen embrittlement relief on a spec. GMW 3044 8K 240/120.
According to the GMW 3044 spec., unless there is an H after the 120, this is not necessary. Also they told me the steel is 1045. According to the ASTM B633 [affil. link to spec at Techstreet] spec. 6.6 section -Tensile strength of 1200 MPa or higher require Hydrogen embrittlement relief.
According to my Central Steel book, typical Mechanical Properties of 1045 steel has a tensile strength of 90/110 ksi. Do you know the conversion of MPa to ksi, or an easier way to determine if a part needs baking/hydrogen embrittlement relief, if the print/spec./customer doesn't call it out directly?
Thanks for your help!

Diana Bench
- Muskegon, Michigan, USA

November 30, 2011

A. First, you are misunderstanding the H designation within GMW3044. The H designation refers to heat treating of plated parts prior to salt spray testing, which is a method used sometimes to evaluate the corrosion resistance of finished parts because heating can degrade the chromate layer. It has nothing to do with embrittlement relief. Second, the requirements for whether or not a part requires embrittlement relief are described in section 3.5 of GMW3044: either when the core hardness exceeds 32 HRC or when the surface hardness exceeds 35 HRC. The engineering drawing should indicate whether or not the part is heat treated (quenched and tempered, etc.) and what the hardness requirement is. Based on this, SAE/USCAR-5 defines the embrittlement relief procedure: either 4 hours at 200 °C for parts up to hardness 390 HV (40 HRC) or 8 hours at 200 °C for parts over 390 HV. Embrittlement relief must take place prior to chromate treatment. Lastly, you can convert ksi into MPa by multiplying ksi value by 6.895.

Toby Padfield
Automotive module & component supplier - Michigan, USA

To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)

November 10, 2011

Q. I'm an engineer trying to write good drawing notes for plating requirements. I figure that if I ask a plater to plate a part per a specification, the least I can do is read the specification and give them all of the ordering information they need to plate our parts per the specification.

In this case I am specifying electroless nickel plating of steel parts per ASTM B733 [affil. link to spec at Techstreet]. If I am coating primarily for corrosion protection, I can select a class 3 post heat treatment to improve adhesion and to provide for hydrogen embrittlement relief. Per B733 paragraph 6.6, parts with hardness greater than 31 Rockwell C shall require post coating hydrogen embrittlement relief baking per Guide ASTM B850-98 [affil. link to spec at Techstreet].

Does specifying embrittlement relief baking per Guide B850 replace Class 3 post heat treatment or should it be specified in addition to Class 3 post heat treatment?


Bill Capers
manufacturing engineer - Orlando, Florida, USA

February 10, 2015

Q. What is the answer to the Heat Treatment vs. Hydrogen Relief question?

Richard Miller
- Merrill Michigan USA

February 13, 2015

A. Hi Bill, Richard,

Bit of an odd one this. Whereas ASTM B733 [affil. link to spec at Techstreet] indicates that Class 3 requires one stoving temperature for adhesion and de-embrittlement, it doesn't take into account the strength/hardness of the material, which as you get harder/higher strength the stoving time is normally increased and the delay time between plating and de-embrittlement reduces.

Guide ASTM B850-98 [affil. link to spec at Techstreet] is a better document to use as a guide to the minimum times for de-embrittlement operations, especially true when you get up the the high tensile strength or very hard materials.

Brian Terry
Aerospace - Yeovil, Somerset, UK

February 23, 2015

Let's say that this plating has a Class 2 requirement (Heat Treat for Hardness), and it also needs Hydrogen Embrittlement relief. Which of these would be performed first?
Thanks for your help.

Richard Miller [returning]
- Merrill Michigan, USA

February 24, 2015

A. Hi Richard,

If the high temperature treatment cannot be done within a reasonable time (at least within 4 hours of plating) then the embrittlement relief bake needs to be done first.

Some companies consider the high temperature bake as sufficient to replace the hydrogen embrittlement relief if it can be done within 4 hours, but you would need to check with your customer first before going down that route.

So, generally it is hydrogen embrittlement relief bake first and heat treatment second.

Brian Terry
Aerospace - Yeovil, Somerset, UK

Stress relief & de-embrittlement baking when hardness of parts varies?

November 15, 2020

Q. When I perform stress relief & de-embrittlement baking, I wonder which time & temp is applied if the parts have been hardened to 52-55 HRC and it's 200 pieces,

In AMS 2417 it's specified:
1. "For parts having a hardness 55 HRC and above, stress relieve at (135 °C +/_ 14 °C)"
2. "For parts having a hardness less than 55 HRC ...

So if the parts are hardened to 52-55 HRC, should it be done even if only one 55 HRC?

Sorry for my lack of english. I'm not from an english-speaking country.

Oh Jeong
- Korea Kyungsangdo

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