Heat, quench, and bend test to detect delayed flaking / blistering

letter 37006

Heat, quench, and bend test to detect delayed flaking / blistering

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Is anyone familiar with a heat, quench, bend test to detect potential delayed blistering and flaking? We currently use zinc cobalt on a 1008 cold formed part that gets crimped at installation, and are having some occasional problems with flaking.

I have heard that the above mentioned test will help find these type of defects if done immediately after plate. We already make it a requirement that the parts be crush tested, but I was wanting to know if the heat and quench before crush will help?

Also, if this is a typical test, what are the parameters that are usually used, time, temp., etc.
Thanks,

Kevin Davis
Automotive tube fab. - Versailles, KY, USA.

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Dear Kevin,

I have tried this test myself and I do believe it can help with the early detection of some of the causes of delayed blistering. For example if the base metal contains pits/pores that entrap oils or solution beneath the plate; heating this will drive these out of the pores and blister or weaken the bonding between the plate and the substrate.

I'm not aware of any set of standard conditions for this test, however I would try heating to about 150 oC for a few hours to ensure the traped solution is fully driven out of the pores.

Also keep in mind if the test gives a negative result, i would not automatically conclude that the plate wont blister over time, as it maybe due to different factors.

good luck and let us know what you think of it...

Peter Van de Luecht
- Melbourne, VIc, Australia

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