Hydrogen Diffusion 1

[MetalsInc]

I'm lookign for help evaluating the diffusion rate of hydrogen in ferritic steel (pipeline), austenitic SS (309L), and Inconel 625 as it relates to temperature. I'm looking for the formulae that describes the movement. The concern is how far hydrogen can/will move in a given time at a given temperature.

 

[NickE]

There is a simple relation ship:

D=Do*exp(-Q/RT) the trick is knowing Q and Do.

Also knowing how to utilize the information provided is of course also very important.


The book Diffusion In Solids by Shewman is the text we used in grad school. ISBN:0-87339-105-5 Published by TMS.

In undergrad we used: Introduction to Transport Phenomena in Materials Engineering by Gaskell. ISBN:0-02-340720-4 Published by Macmillan



Nick
I love materials science!

 

[MetalsInc]

I'll grab that book tonight if possible. Can I assume that Q and Do can be found in there? If not, any direction on that.

I'm looking at the AWS and ISO standards on diffusible hydrogen measurement and am curious about differences in their procedures. So I'd like to know how far hydrogen can diffuse in a given time at a given temp.

 

[NickE]

I dont know about the gaskell book cause I havn't read it in a long time.. The Shewman book is mainly academic, with few worked examples and few constants.

I can look around for Do (the diffusion constant for Hydrogen in ferrite iron) and Q (the activation energy)

In my experience rarely does just having the equation and proper constants help. Also using it a properly is very important.

That said Hydorgen in Fe-alloy and Ni-alloy was a homework problem for the grad class (IIRC) it was on using Ni as a diffusion barrier.

I dont know anything about standard measurement methods and such.

 

[Maui]

The following website gives a very good general explanation for this phenomena:

http://www.matter.org.uk/matscicdrom/manual/df.html

The following paper is relevant, and should provide some useful information in terms of failure behavior and mechanisms in austinitic stainless steels:

http://www.ingentaconnect.com/content/maney/mst/2001/00000017/00000003/17030302

Just click on the PDF box at the bottom of the page, and it will provide you with a PDF version of the paper.


Maui

Constants aren't; variables won't.

 

[rorschach]

I don't have an answer, but you might want to cross-post this to the fuel cell group, they have to deal with this issue too.