> Mike and Chris both have part of the HIC picture (although this is a
> subject very difficult to "prove" a mechanism in). Essentially what
> happens is that the hydrogen atom, being very small and mobil, works
> into the crystal structure, and either 1) stresses a previously
strong,
> stable, crystal, leading to failure at the smallest level of crystal
or
> 2) forces a change in the crystal structure (i.e., from a BCC to a FCC
> or other combinations), resulting in a material change (austenitic to
> ferritic?), in that particular crystal or region of crytals, and often
> releasing energy that induces changes adjacent to it.
>
> I did a fair amount of study on hydrogen formation back in my nuke
days.
> Some level of hydrocarbon cracking or even water hydrolysis happens
all
> the time. Conditions aggravate it. Some materials are apparently
> catalysts to inducing it.
>
> The mechanisms of SIC are quite different. A good reference on it is
> "Corrosion handbook" by HH Uhlig.
A lot of what you never hear about happens in Air Liquide/Air Products/Praxair labs and test projects. They do this all the time (can't say more without violating agreements).
That is where a lot of the forward thinking is done, and it can take 5-20 years to be implemented due to commercial and ROI concerns.
I *think* I'm starting to see one result of an R&D project I worked on 10 years ago, but I can't be sure; it's all compartmentalized.
Paul Received on Fri May 14 10:51:00 2004
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