Dear all,
I have created a potential project proposal on dimensional stability of high temperature alloys. We will post an SPS shortly with a detailed project description. But the thing that got me started was the figure in a paper by Stickler & Weiss on the acceleration of precipitation by plastic deformation (cold work).
Then I read another paper by Boeuf on the contraction/densification of 304 upon M23C6 precipitation from solid solution,
and I found the same happened for alloy 617 upon gamma prime precipitation.
Since the strains during/after welding are located particularly around welds, I am intrigued to see if, and how much, localized contraction occurs by fast precipitation in cold worked areas with work hardening:
After some fast calculations on the back of an envelope, I think these localized strains may have a significant influence on localized creep cracking such as what we see in SRC/reheat cracking. They may explain why the profusely precipitating (stabilized) alloys we use so much (321/347/617/800H) are so sensitive to SRC. And also why 304/316/347AP/1.4910 type alloys perform better in terms of susceptibility, because they form much less precipitation.
The goal of the project is to build a thermodynamic/kinetic framework model that is calibrated to literature data on contraction. This can then be used to do FEA calculations on the rise of additional hydrostatic over the course of a PWHT or early operational life. It can also potentially be used for alloy development. I would eventually do some testing in a second phase to characterize certain alloys with experimental data.
Please see my EuroTAC introductory presentation, which will be uploaded by Asger soon on the EuroTAC page. Kind regards. Jan-Willem
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Jan-Willem Rensman
Fluor
Hoofddorp Netherlands
31 23 5432164
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