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RE: Hydrogen embrittlement of fasteners 

07-21-2020 08:56
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18 Medcalf J.S. Thomas B.G. and Brahimi S.V. Hydrogen Emb....pdf   5.65 MB   1 version
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Vivek Singal
08-18-2020 02:55

Thanks Brian for your message. I like your suggestion for need of further studies and had particularly liked your suggestion that probably increasing the baking time could reverse the effect. Hydrogen embrittlement is a diffusion controlled phenomena This makes it is more difficult to judge the holding time.

Brian Thomas
08-18-2020 02:25

Thanks for your interest in our paper. 

It is clear that baking lowered the failure strength of the fasteners, but the fracture surfaces of the failed fasteners appeared to show embrittlement, so we do not think it was simply lower strength that caused the premature failures.  However, I agree that our study was very limited, and evaluation of fracture surfaces subjected to failure under torsion are not easy to interpret, so we are open to other explanations, and we recommend further study is needed to investigate this controversy. 
Nothing beats sampling based on proper statistical process control, destructive testing, and examination of the fractured specimens and fracture surfaces to evaluate embrittlement, so I am sorry I do not know of an NDT test that can substitute for that. That is another question that deserves further research.

Vivek Singal
08-18-2020 01:48

I read through your paper and it was interesting. I would like to debate the conclusion that baking after electroplating was detrimental to the fastener. Can we not say that the baking of 11.2 hrs has lowered the strength of the sample.

Also do you recommend any NDT method to find hydrogen embrittlement.

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