hydrogen embrittlement

By RonG

Date 11-29-2004 17:39

I should think not. What are you welding with (filler material)?

By dho

Date 11-29-2004 17:58

actually it is GTAW welded to (and sandwiched by) 304 with no filler. i read on the web, there were cases of 17-7 hydrogen embrittlement due to plating. we also had a weld failure (cracked) during vibration testing.
thanks.

By RonG

Date 11-29-2004 18:57

Not sure I understand "due to plating".
Where would the Hydrogen come from unless the work is not clean.

Is the 304 an L or H? You may have a problem with Carbon Sensitization. Normally this should only degrade the Stainless qualitys of the weld but then I do not know your application.

By dho

Date 11-29-2004 19:47

DURING PLATING, THERE IS ACID. SO THERE WILL BE "H+". YOU MAY KNOW ALL PLATED PARTS HAVE TO BE BAKED TO GET RID OF THEM.
IN OUR CASE, DIFFER FROM PLATING, BUT THE SHIELDING GAS HAS 3% HYDROGEN.
JUST 304. IT IS NOT L (LOW CARBON GRADE).

By G.S.Crisi (****)

Date 11-29-2004 20:21

If the shielding gases contain 3% of hydrogen, there's the danger that the molten metal absorbs hydrogen.
There's a difference between "hydrogen absortion" and "hydrogen embrittlement". Hydrogen absortion not always leads to embrittlement. It depends mainly from the temperature the weld is subjected to. At room temperature, for example, the danger of embrittlement is minimum. The higher the temperature, the higher the danger. I don't know what your case is.
Giovanni S. Crisi
Sao Paulo - Brazil

By dho

Date 11-29-2004 20:34

thanks, professor.
it (sandwich) welds a 17-7ph .001" thick "diaphragm" to 304 housingS. the service temperature is -65F to +275F. the weld joint subjects to (minor) pressure, vibration.
since we had a weld joint broken apart during vibration test, i was puzzled why, stress concentration, h-embrittlement... etc.

By G.S.Crisi (****)

Date 11-30-2004 17:45

Taking into account the very small thickness of the diaphragm and that it's subject to vibration, I'd say as a preliminary opinion that the reason for rupture is fatigue. Anyway, the case deserves some more investigation.
Giovanni S. Crisi

By dho

Date 11-30-2004 17:49

thanks.
if you do not mind, i would send you email with photos of the failed section.

By RonG

Date 11-29-2004 20:57

In your first post you wrote "shielding gas contains % of hydrogen" I assumed 0%. Sorry about that.

By dho

Date 11-29-2004 21:02

thanks.
because the percentage of hydrogen may vary from one weld schedule to another, so i just wrote %.